Section 5 Gastrointestinal Tract and Abdomen
2 Abdominal MassWilbur B. Bowne, MD
State University of New York Downstate Medical Center College of Medicine
Section of Surgical Oncology
State University of New York Health Science Center of Brooklyn
State University of New York Downstate Medical Center College of Medicine
Chairman, Department of Surgery
University Hospital of Brooklyn
Evaluation of an Abdominal Mass
Abdominal masses are commonly addressed by surgeons, as well as by members of many clinical subspecialties. In terms of clinical importance, abdominal masses cover a broad spectrum: some have few or no apparent consequences, others significantly impair quality of life, and still others represent severe conditions that are associated with poor outcomes and high mortalities. For each patient, therefore, it is essential to formulate a management approach that is tailored to the particular clinical situation. Effective decision-making in this regard involves establishing the correct diagnosis, introducing an effective treatment plan, eliminating risks and complicating factors, initiating preventive measures, and determining the prognosis.
The history of the abdominal mass in the medical literature is ancient, dating back to the Egyptians. The varied differential diagnosis of such masses was discussed in the Papyrus Ebers (ca. 1500 B.C.).
1 Egyptian medical scholars kept detailed notes chronicling conditions encountered and describing methods of abdominal examination that were based on studies of basic anatomy and embalming practices. Centuries later, in his Book of Prognostics, the Greek physician Hippocrates (ca. 400 B.C.) discussed the prognostic significance of various types of abdominal masses:The state of the hypochondrium is best when it is free from pain, soft, and of equal size on the right side and the left. But if inflamed, or painful, or distended; or when the right and left sides are of disproportionate sizes; all of these appearances are to be dreaded. A swelling in the hypochondrium, that is hard and painful, is very bad.... Such swellings at the commencement of disease prognosticate speedy death. Such swellings as are soft, free from pain, and yield to the finger, occasion more protracted crises, and are less dangerous than others.2
In this chapter, we begin with essential definitions and anatomic considerations and then outline our fundamental approach to evaluating patients with an abdominal mass, which integrates the clinical history, the physical examination, and various investigative studies. In particular, we address current developments in investigative techniques, including radiographic and molecular imaging studies that facilitate anatomic evaluation, diagnosis, and determination of the biologic significance of the abdominal mass; we also address minimally invasive diagnostic interventions. Throughout, we emphasize an algorithmic, evidence-based approach to detection and evaluation of abdominal masses. Specific perioperative and operative strategies for addressing particular diagnoses are outlined in other chapters.
Clinical EvaluationIn general, the term abdominal mass refers to a palpable mass that lies anterior to the paraspinous muscles in a region bordered by the costal margins, the iliac crests, and the pubic symphysis. One method of description divides the abdomen into nine areas: epigastric, umbilical, suprapubic, right hypochondriac, left hypochondriac, right lumbar, left lumbar, right inguinal, and left inguinal.
3 Our preferred method divides the abdominal cavity into four quadrants—right upper, right lower, left upper, and left lower—and makes specific reference to the epigastrium and the hypogastrium as necessary. This method of description also includes masses discovered within the retroperitoneum and the abdominal wall. For practical purposes, the abdominal wall begins from the diaphragm superiorly and continues inferiorly to the pelvic cavity through the pelvic inlet. The anterior, posterior, and lateral boundaries of the abdominal wall should be familiar to surgeons. Further anatomic detail is available in other sources.4,5A sound understanding of the normal anatomy in each abdominal quadrant is essential for the evaluation of the abdominal mass. Particular abnormalities tend to be associated with particular regions or quadrants of the abdomen, and these associations should be considered first in the differential diagnosis. Commonly, an abnormal enlargement or mass in the abdomen comes to the clinician's attention in one of three ways: it is detected and reported by the patient, it is discovered by the clinician on physical examination, or it is noticed as an unrelated incidental finding on a radiographic study. Subsequent clinical decision making is then influenced by whether the lesion is intra-abdominal, pelvic, retroperitoneal, or situated within the abdominal wall. In certain cases, a prompt diagnosis can be made after the physical examination, with no further investigation required; obesity, ascites, pregnancy, hernias, infection or abscess, cysts, and lipomas are examples of conditions that can generally be diagnosed at this point.
Of the various factors that go into making the diagnosis and implementing therapy, clinical experience is undoubtedly paramount. Nevertheless, even the most experienced physicians are subject to some degree of clinical inaccuracy. A randomized study from 1981 found that even when experienced clinicians were certain about the presence of a mass, there was still an appreciable (22%) chance that further investigation would not reveal any abnormality.6 The evaluation of abdominal masses continues to pose many clinical challenges for the surgeon. There is no magical formula for mastering the necessary diagnostic skills; the closest thing to such a formula is an approach that combines knowledge and application of fundamental anatomic principles with continuous development and appropriate utilization of new diagnostic modalities. For accurate assessment of the origin and character of the abdominal mass, it is essential to possess a thorough understanding of the normal anatomy, the anatomic variations that may be observed, and the distortions that may be caused by the various potential disease processes. As has been said of many professions besides surgery, 'You must know the territory.' Ultimately, whether a correct diagnosis calls for further intervention or for referral to colleagues with complementary technical expertise depends on the experience of the practitioner.
Fundamental to the successful diagnosis of any abdominal mass are a detailed medical and surgical history and a meticulous physical examination (see below).
History
Establishing a solid surgeon-patient relationship is vital for building patient trust and confidence, particularly during a period of great uncertainty and vulnerability in the patient's life. Accordingly, our philosophy in dealing with an abdominal mass is to evaluate the patient first and then consider radiographic and laboratory studies if the initial assessment does not yield a diagnosis. A careful and methodical clinical history should be taken that includes all factors pertaining to the lesion. Information about the lesion's mode of onset, duration, character, chronology, and location should be obtained, as well as confirmation of the presence or absence of associated symptoms.
Interviewing strategies for collecting clinical data may vary from surgeon to surgeon.
7 For example, some prefer to conduct a clinical history while sitting rather than standing because this posture tends to suggest the absence of undue haste and the presence of appropriate concern and empathy. A focused, comprehensive interview usually provides all the information necessary for making the correct diagnosis. Our practice is to start by asking nondirective questions—for example, 'When did you first notice the mass on your left side?' or 'How long did you experience this pain in your abdomen?' It is important to allow patients to describe the history in their own words. It is also important to avoid questions with a built-in degree of bias—for example, 'Didn't you know the mass was on your left side?' or 'The pain must have been there for some time?' Such questions can lead to biased answers that may misrepresent the chronology or the true natural history of the disease. In most cases, we then proceed to ask questions designed to elicit more specific information (e.g., previous operations, previous medical conditions or therapies, family medical history, or recent travel). It is sometimes necessary to fill in the details by asking direct questions about particular points not already mentioned by the patient. For example, an inquiry regarding gastrointestinal symptoms associated with the abdominal mass may be either nonspecific (e.g., concerned with nausea, vomiting, diarrhea, or constipation) or specific (e.g., concerned with jaundice, melena, hematochezia, hematemesis, hematuria, or changes in stool caliber). Non-GI symptoms (including urologic, gynecologic or obstetric, vascular, and endocrinologic symptoms) should not be overlooked. A history of surgery, trauma, or neoadjuvant or adjuvant cancer therapy may be diagnostically important.8 For instance, the presence of an abdominal mass representing recurrent cancer raises important clinical questions concerning the advisability of additional therapy or palliative measures, which may carry significant morbidity and mortality.9–12Differential Diagnosis
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| Figure 1. Diagnosis of abdominal mass by region |
For practical purposes, the differential diagnosis for an abdominal mass is divided into categories corresponding to the anatomic divisions of the abdomen (i.e., the four quadrants, the epigastrium, and the hypogastrium) [see Figure 1]. The challenge for the modern surgeon is how to narrow down the diagnostic possibilities while avoiding needlessly extensive and expensive evaluations. To accomplish this goal with efficiency, the surgeon must draw both on his or her own reservoir of fundamental knowledge and on the available patient data (e.g., age, gender, associated symptoms, and comorbidities).
After obtaining a thorough clinical history, the surgeon should be able to generate a differential diagnosis. The physical examination may then help confirm or rule out diagnostic possibilities. For example, the presence or absence of pain or tenderness may distinguish an inflammatory or nonneoplastic process from a neoplastic one (e.g., cholecystitis from Courvoisier gallbladder or, perhaps, diverticulitis from carcinoma of the colon). Likewise, the acuteness of the condition may help eliminate diagnostic possibilities, as when an incarcerated abdominal wall hernia is distinguished from a lipomatous mass. So too may the nature of the process, as when a pulsatile mass such as an aneurysm is distinguished from a nonpulsatile one such as a hematoma or a cyst.
Masses of the abdominal wall commonly are subcutaneous lipomas, and care should be taken to differentiate them from neoplastic lesions such as desmoid tumors,13 dermatofibrosarcoma protuberans (DFSP),14 and other related15 or nonrelated tumors.16,17 When an abdominal mass is associated with uncommon or unexpected findings, the surgeon must be alert to the possibility of an uncommon or unexpected disease process.18,19 It remains true, however, that knowledge of the most common disease processes associated with region-specific abdominal masses, combined with familiarity with the characteristic signs and symptoms, is the foundation of the clinical assessment of such masses.
Physical Examination
The physical examination plays an essential role in the evaluation and workup of an abdominal mass. Current investigative studies are also important in this setting, but all too often, clinicians become overly reliant on various imaging modalities, sometimes overlooking the importance of a careful and thorough examination. Such overreliance can increase the chances of missing subtle physical findings—such as an enlarged lymph node, subcutaneous irregularity, or referred pain—that could have a significant effect on the management of the abdominal mass. Our practice in examining patients with an abdominal mass is to follow an organized, systematic approach consisting of inspection, auscultation, percussion, and palpation, in that order. More detailed discussions of these specific maneuvers are available elsewhere.20
The physical examination has three main objectives. First, the examiner must evaluate the patient's condition as it directly or indirectly relates to the mass (e.g., by noting associated systemic illness, pain, malaise, or cachexia). Second, the examiner must assess the acuteness of the patient's condition (e.g., by determining whether a left upper quadrant mass is likely to be a ruptured spleen or simply a long-standing mass in the abdominal wall), which will dictate whether the next step is immediate treatment or further evaluation. Third, the examiner must carefully examine each abdominal quadrant, assessing both normal and abnormal anatomic relations as possible sources of the presumed mass.
How to distinguish a normal abdominal mass or swelling from an abnormal one remains a common challenge for the surgeon. Physical findings on examination are sometimes variable and can be affected by factors such as obesity, body habitus, associated medical conditions, and the patient's ability to cooperate. For example, the normal aorta is often palpable within the epigastrium and may be slightly tender; in elderly, asthenic patients, the normal aorta may be mistaken for an aneurysm. Likewise, the cecum and the descending colon, both of which are usually palpable in thin patients (especially when they contain feces), sometimes masquerade as a cancerous mass; subsequent disimpaction causes such 'masses' to resolve. Obesity may preclude evaluation of a potential abdominal mass: it can be difficult to identify discrete palpable masses amid the often remarkable adiposity present within the abdominal wall and the surrounding structures. Ascites may also obscure abdominal masses, making examination more problematic. Transient gaseous distention or intestinal bloating occasionally presents a similar problem, but it usually resolves spontaneously, except in cases of intestinal obstruction. Either gastric dilatation or intestinal obstruction may lead to abdominal distention that is severe enough to necessitate nasogastric decompression. Not uncommonly, in women of childbearing age, a lower abdominal mass may represent a gravid uterus. In such cases, a gynecologic examination must be conducted and a pregnancy test performed before further studies are ordered. The multiplicity of potential benign causes notwithstanding, the possibility of a neoplasm (single or multiple) clearly remains a matter of considerable concern in the evaluation of any patient with abdominal distention. A convenient method of recalling the main causes of generalized enlargement or distention of the abdomen is to use the so-called 'six Fs' mnemonic device: Fat, Fluid, Flatus, Fetus, Feces, and Fatal growths.21–23
Palpable or discrete masses should always be localized with respect to the previously described landmarks (see above), and they should, if possible, be described in terms of size, shape, consistency, contour, presence or absence of tenderness, pulsatility, and fixation. Knowledge of the location of the mass in the abdomen shortens the list of structures or organs to be considered and may give insight into the nature and extent of the pathologic process. Frequently, however, the mass's location can only be vaguely outlined, particularly when fluid is present, when the abdomen is tender or tense, or when the patient is obese. Gastric neoplasms, pancreatic neoplasms, colonic neoplasms, sarcomas, pancreatic cysts, and distended gallbladders may be palpable, typically at advanced stages of disease. Recognition of such masses can be facilitated by repeating the abdominal examination after analgesics have been administered or after the patient has been anesthetized in preparation for a procedure.
Working or Presumed DiagnosisOnce a thorough clinical history has been obtained and a careful physical examination conducted, it is usually possible to generate a working diagnosis. Once the working diagnosis has been established, subsequent management is considered in light of its appropriateness for the presumed condition. Sometimes, however, the diagnosis remains unknown even after a comprehensive clinical history and physical examination; in such cases, further studies are required. A wide range of laboratory and imaging studies are now available for establishing the diagnosis. If these studies do not resolve the diagnostic uncertainty, additional procedures, including image-guided percutaneous biopsy, diagnostic laparoscopy, and exploratory laparotomy, may be employed as necessary.
Investigative StudiesSurgeons are in a unique position to care for patients presenting with an abdominal mass and should guide the collaborative management effort and the choice of appropriate investigative studies. It is therefore essential that surgeons be familiar with every available method for efficient and cost-effective diagnosis of an abdominal mass. For any given situation, the selection of investigative studies should be based on the preferences of the patient, the knowledge and judgment of the surgeon, and the capabilities of the institution. In this way, surgeons who practice outside large, specialized referral centers will still be able to provide integral leadership for most disease management efforts arising from the diagnosis of an abdominal mass.
Laboratory Studies
The diagnostic workup of an abdominal mass usually includes laboratory evaluation. If the cause of the mass remains unknown, preliminary laboratory analysis should include a chemistry profile (electrolyte, blood urea nitrogen [BUN], and creatinine concentrations, as well as liver function tests), a complete blood count (CBC) with differential, and urinalysis. An abnormal laboratory value sometimes plays an important role in establishing the identity or pathogenesis of an abdominal mass. For example, an elevated alkaline phosphatase or liver transaminase level may suggest metastasis to the liver. Likewise, an elevated serum amylase concentration may be suggestive of a pancreatic pseudocyst rather than a cystic neoplasm or an adenocarcinoma; however, an elevated total serum bilirubin level (i.e., > 10 mg/dl) may be more suggestive of a malignant process secondary to adenocarcinoma of the pancreatic head or cholangiocarcinoma. Routine testing for occult blood in the stool should not be overlooked. Tumor markers (e.g., carcinoembryonic antigen [CEA], the cancer antigens CA 19-9 and CA 125, and a-fetoprotein [AFP]) may also help differentiate between benign disease processes and malignant ones, distinguish high-level disease from low-level disease, and, in some cases, establish a disease diagnosis (e.g., elevated AFP levels in patients with hepatocellular carcinoma). Similarly, an elevated serum lactate dehydrogenase (LDH) level may prove invaluable in the staging and prognosis of certain diseases (e.g., melanoma) connected with an abdominal mass.
24 Furthermore, the ability to distinguish between functional abdominal masses and nonfunctional ones (e.g., adrenal tumors) also has important implications for evaluation and management.In some cases, when the type of mass remains unknown, needless and expensive laboratory analysis can and should be avoided if it appears that other studies may prove more beneficial.
Imaging
Diagnostic radiology is a dynamic specialty that has undergone rapid change in conjunction with the ongoing evolution of imaging technology. Not only has the number of imaging modalities increased, but each modality continues to be improved and refined for use in evaluating abdominal masses. In particular, advances in cross-sectional imaging techniques, such as ultrasonography (US), computed tomography, magnetic resonance imaging, and positron emission tomography (PET), have made it possible to assess these lesions more precisely. Consequently, whenever the surgeon is confronted with the scenario of a clinically suspected or palpable abdominal mass, accurate diagnostic imaging is of paramount importance. The appropriate use of different imaging modalities in the evaluation of the palpable abdominal mass is well described by the American College of Radiology guidelines,
25,26 which are updated every 6 years.The use of noninvasive US and CT as first-line procedures for the evaluation of palpable masses has received considerable clinical attention.6,27–30 Investigators have found both US and CT to be excellent for affirming or excluding a clinically suspected abdominal mass, with sensitivity and specificity values exceeding 95%. This finding is particularly noteworthy because in only 16% to 38% of patients referred for a suspected abdominal mass will the diagnosis be corroborated by an imaging study.31 Both US and CT are also capable of visualizing the organ from which the mass arises: US successfully determines the organ of origin approximately 88% to 91% of the time, and CT does so approximately 93% of the time. Prediction of the pathologic diagnosis of an abdominal mass, however, remains a challenge for both modalities. US correctly predicts the pathologic diagnosis in 77% to 81% of cases, whereas CT suggests the diagnosis in 88% of cases. Further advancements in cross-sectional imaging (e.g., multidetector CT [MDCT] with three-dimensional reconstruction and magnetic resonance angiography [MRA]) and the addition of molecular and functional imaging modalities (e.g., PET) will undoubtedly improve the predictive abilities of CT and US. At any rate, the current state of imaging technology affords clinicians the ability to distinguish benign from malignant processes, to assess tumor biology, and to detect lesions that impose a minimal disease burden. As a consequence, clinicians are more likely to detect clinically occult disease or discover it incidentally.
Employing an integrative assessment approach (which includes clinical history, physical examination, and investigative studies) should lead to more targeted, efficient, and cost-effective strategies for evaluating abdominal masses. For example, the surgeon can correlate the clinical location of the abdominal mass with pertinent findings from the history and laboratory studies to determine which imaging modality is the most expeditious and cost-effective for a given circumstance. Each imaging modality has unique strengths and weaknesses.
Plain Abdominal Radiographs
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| Figure 2. Radiograph: adrenocortical carcinoma |
By definition, a plain film is a radiograph made without the use of an artificially introduced contrast substance.32 Commonly employed for initial surveillance of the abdomen, the plain film still has an important place within the investigative armamentarium. Otherwise known as a KUB (kidney-ureter-bladder) study, this low-cost technique may reveal nonspecific or indirect evidence of an abdominal mass, such as variations in the size and density of an organ or displacement of normal structures or fat planes. Furthermore, the radiolucency of air within the bowel may also prove helpful for recognizing worrisome displacement of viscera as a result of a large abdominal mass. Occasionally, a simple plain radiograph can assist the surgeon in making a specific diagnosis, such as calcified aortic aneurysm, acute gastric distention, fecal impaction, porcelain gallbladder, and certain malignancies [see Figure 2].
Conventional Gastrointestinal Imaging
As a consequence of the technical advances in cross-sectional imaging and endoscopy, conventional GI contrast studies are now largely relegated to more adjunctive roles in the evaluation of abdominal masses. In the upper and middle portions of the abdomen, we occasionally use upper GI studies, small bowel follow-through (SBFT), or enteroclysis to evaluate inflammatory masses (e.g., lesions arising from Crohn disease), masses that are inaccessible to endoscopy, or unusual masses with uncertain diagnoses. For such lesions, we employ single- or double-contrast barium protocols to ensure that significant pathology is not missed; however, these studies are notoriously insensitive and do not provide an opportunity for tissue diagnosis. In the lower portion of the abdomen, barium studies still play a significant role in the evaluation of masses whose history includes GI symptoms (e.g., anemia and weight loss) suggestive of a colonic neoplasm, as well as for evaluating inflammatory masses arising from diverticular disease. In certain cases, we employ a single-contrast barium enema for masses that are causing near-complete obstruction; this study is also helpful for assessing the remaining large bowel for synchronous disease. For small lesions (masses < 1 cm), we typically favor a double-contrast barium enema.
Currently, in the evaluation of an abdominal mass, barium studies are used mainly to complement colonoscopy and CT. Novel approaches (e.g., CT virtual colonoscopy), in conjunction with advances in cross-sectional imaging, may eventually render conventional GI imaging unnecessary.
Ultrasonography
Compared with other modalities, US has several advantages in the evaluation of suspected abdominal masses, including widespread availability, speed of use, the absence of ionizing radiation, low cost, and the ability to document the size, consistency (solid or cystic), and origin of a mass with real-time images.27,33 When directed at solving a specific clinical problem, US generally provides more diagnostic information. Moreover, the necessary equipment can easily be transported to the patient's bedside or another clinical setting; thus, no patient preparation is required, and only minimal patient cooperation is needed.
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| Figure 3. Ultrasonogram showing pancreatic mass |
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| Figure 4. Ultrasonogram showing hepatoma |
We consider US indispensable in the assessment of abdominal masses. At the same time, we acknowledge that one disadvantage of US is the extent to which the quality of the results depends on the technical proficiency and diligence of the operator or technician (though this disadvantage can actually become an advantage when personnel are well trained and experienced). In the hands of an inexperienced operator, US may yield inconclusive or untrustworthy results that contribute to delayed diagnosis or even misdiagnosis. In an effort to help minimize this problem, we encourage the surgeons at our institution (who are trained in US) to perform their own studies in the clinic and the operating room. This approach further expedites recognition of disease [see Figure 3], positively influences management, and facilitates operative decision making regarding abdominal masses [see Figure 4].
Another disadvantage of US is its inability to visualize the entire abdominal cavity as a consequence of the acoustic barriers presented by gas-containing structures (e.g., the bowel) and the absorptive interfaces (acoustic shadowing) provided by soft tissue and bone. For optimal visualization of abdominal masses, US should be performed through 'acoustic windows' that allow adequate transmission of sound. Accordingly, US is most effective as a tool for evaluating masses in those regions of the abdomen where an acoustic window exists (e.g., the right and left upper quadrants and the pelvis). Fortunately, the shortcomings of US can be compensated for by employing other cross-sectional imaging modalities.
Computed Tomography
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| Figure 5. CT scan: retroperitoneal leiyomyosarcoma |
At present, helical (spiral) CT is the most efficient and cost-effective imaging modality for the evaluation of abdominal masses.6,27,34,35 Unlike US, CT provides cross-sectional images with excellent spatial resolution and exquisite density discrimination that are unaffected by bowel gas, bone, or excessive abdominal fat. CT routinely visualizes the abdominal wall, the viscera, the mesentery, and the retroperitoneum, clearly defining important tissue planes and delineating the relations between the abdominal mass and adjacent structures [see Figure 5]. Such data are essential for guiding diagnostic procedures, determining whether operative management is indicated, and selecting the optimal operative approach. Although modalities such as MRI, PET, and endoscopic ultrasonography (EUS) have advantages over CT in one area or another, CT continues to be superior overall for assessing abdominal masses and remains our preferred imaging method for this purpose.
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| Figure 6. CT angiography: vascular invasion from pancreatic mass |
The use of contrast during the acquisition of CT scans is vital. Opacification of the bowel enables the examiner to distinguish the abdominal mass from surrounding viscera or other adjacent structures. Contrast-enhanced scans also allow delineation of the relevant vascular anatomy; in fact, CT angiography has now relegated conventional angiography to a minimal role in the evaluation of certain abdominal masses.36,37 Triple-phase or multiphase scanning that includes noncontrast images is now recommended. Such scans achieve optimal definition and characterization of liver and pancreatic masses. This achievement is of significant clinical value: state-of-the-art CT imaging of malignant pancreatic masses, as well as of other malignancies, has the potential to improve outcome not only by correctly detecting the mass but also by accurately assessing the extent of disease, thereby helping determine which patients may benefit from surgical management or neoadjuvant therapy [see Figure 6].
The advent of MDCT technology offers the possibility of even better imaging of abdominal masses than standard contrast CT provides. MDCT scanners can image specific organs or masses with 1 mm slices in less than 20 seconds, and the resultant data can be displayed not only as an axial image but also in a three-dimensional representation that includes detailed vascular mapping.35 Studies suggest that MDCT may be the most useful modality for preoperative assessment of the resectability of pancreatic and other abdominal masses.36 MDCT has a sensitivity of 90% and a specificity of 99%, respectively, and it is not observer dependent.
Currently, although MRI (see below) offers unique tissue contrast and inherent multiplanar capabilities for imaging abdominal masses, CT has several advantages—high resolution, short scan times, and fast patient throughput—that make it a more widely preferred imaging modality for this purpose.
Magnetic Resonance Imaging
Since its introduction in the mid-1980s, MRI has become one of radiology's great success stories (though, because it still is not as widely available as US or CT, its cost-effectiveness has yet to be determined). Few would dispute the enormous impact MRI has had on our ability to diagnose pathologic conditions of the brain, the spine, and the musculoskeletal system. Whereas MRI has clear advantages over CT in these areas of the body, this is not the case in the abdomen. Nevertheless, there are situations in which MRI is a better choice than CT for evaluating an abdominal mass. An example is a case in which the use of iodinated contrast material is contraindicated. The extracellular gadolinium chelates used in MRI are very safe and can be given to patients with mild to moderate azotemia without causing renal impairment. MRI has unique characteristics that can be effectively employed to distinguish normal from pathologic tissue in a patient with an abdominal mass.38
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| Figure 7. MRI showing large mass |
Detailed information about the principles and practices of abdominal MRI is beyond the scope of this chapter and is readily available elsewhere.39 A brief technical summary may, however, be worthwhile. The abdomen and its contents are subjected to a momentary radiofrequency pulse, then allowed to return to a state of equilibrium. During the return to equilibrium, the nuclei within each specific tissue will emit specific radiofrequency signals. The strength and type of the emitted signal determine the image intensity. The way in which the different tissues are visually rendered depends on (1) the longitudinal relaxation time (T1) and the transverse relaxation time (T2) of the nuclei in the tissues and (2) the method of image weighting employed. By convention, tissues with short T1 values (such as solid structures) appear bright on T1-weighted images, whereas structures with long T2 values (e.g., fluid-containing tissues) appear bright on T2-weighted images. The tissue contrast and multiplanar capabilities of MRI allow surgeons and radiologists to distinguish not only obvious but also subtle differences between abdominal masses and normal anatomy. For example, T1-weighted images may be valuable for detecting abdominal masses that contain fluid (e.g., cystic masses or masses containing necrotic tissue), whereas T2-weighted images may be useful for characterizing these masses as either benign or malignant [see Figure 7]. Similarly, magnetic resonance cholangiopancreatography (MRCP) uses T2-weighted images to distinguish masses with different signal intensities in the pancreas, the liver, and the biliary tract.40
Positron Emission Tomography
In 1930, Warburg reported that cancer cells show higher rates of glycolysis than normal cells do.41 This discovery has stood the test of time and now serves as the theoretical rationale for the use of 18F-fluorodeoxyglucose (18FDG) PET imaging to assess abdominal masses caused by cancer. Briefly, 18FDG is a glucose analogue that crosses the cell membrane by sharing the glucose transporter molecules used by glucose. Like glucose, it undergoes phosphorylation by the enzyme hexokinase. The resulting molecule, 18FDG-6-phosphate, is polar and is unable to cross cell membranes or serve as a substrate for metabolism. The net effect is that 18FDG both accumulates in and is retained by cancer cells.
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| Figure 8. PET scan: abdominal mass in non-Hodgkin lymphoma |
The molecular information obtained from PET, as measured by standard uptake values (SUV), allows identification of hypermetabolic (18FDG-avid) abdominal masses (typically arising from lymphomas, melanomas, or certain GI malignancies [see Figure 8]).42 PET may also prove to be an important surrogate modality for distinguishing malignant abdominal masses from benign ones.43 When PET is used alone, it has the disadvantage of being unable to provide sufficient anatomic information to guide biopsy or further therapy. When PET is used with CT in PET/CT fusion imaging, however, the functional advantages of PET and the structural advantages of CT combine to enhance the detection rate for abdominal masses.42 If a mass is anatomically evident but metabolically inactive, it will be detected by CT. If it shows increased glycolysis but few or no CT abnormalities, it will be detected by PET. The apparent advantages of PET/CT notwithstanding, prospective, randomized validation is necessary before the widespread application of this approach to the evaluation of abdominal masses can be justified. At present, the use of PET/CT is mostly restricted to large tertiary referral centers.
Biopsy
In many cases, the pathologist is the surgeon's greatest teacher. Despite the surgeon's most strenuous efforts, the biology of the disease or lesion will inevitably dictate the outcome. Nowhere is this statement more true than in the evaluation of the abdominal mass, and its truth becomes increasingly evident as ongoing refinements in molecular diagnosis permit ever more sophisticated discrimination among different tumor types and their respective behaviors.
44 Aside from the treatment of lymphoma, in which the surgeon is frequently called on to provide technical assistance in obtaining tissue for diagnosis, the decision whether to perform a biopsy (as well as when and how to do so) rests on the surgeon's understanding of the probable disease. For example, surgeons who treat pancreatic cancer usually proceed to surgery without biopsy if the evidence for malignancy is strong. In other cases, biopsy is performed to confirm what is already suspected on the basis of clinical and radiographic findings. Moreover, establishing the type of tumor or mass present has important implications for the use of neoadjuvant or adjuvant therapy, as well as for the planning of the surgical approach. We view the biopsy of an abdominal mass as the first stage of surgery. This procedure, though seemingly innocuous, has the potential to contaminate tissue planes and must therefore be performed carefully. Accordingly, in order to make the appropriate choice when confronted with an abdominal mass, the surgeon must possess a thorough understanding of the various methods of obtaining an accurate and safe biopsy. Factors related to the size and location of the abdominal mass, as well as factors related to institutional preference and experience, may influence the choice of biopsy technique.Image-Guided Percutaneous Biopsy
The value of image-guided percutaneous biopsy in the evaluation of the abdominal mass is well established.45,46 In practice, the procedure begins with identification of the mass by means of a cross-sectional imaging modality such as US, CT, or MRI. Often, three-dimensional imaging reconstructions are generated to detail the relations of the abdominal mass to the surrounding anatomy. Once the mass is identified, decisions are made regarding the safest approach and the most appropriate technique. The biopsy needle is then inserted percutaneously under the guidance of US, CT, or MRI. The choice among the different modalities depends on several factors, including the size and location of the mass, the surgeon's judgment regarding which method is best in the circumstances, and the availability of the various modalities at a particular institution. The most important consideration, however, is the personal preference and experience of the radiologist performing the biopsy. We favor either US or CT, both of which yield good results.
In general, we prefer US-guided biopsy for large, superficial, and cystic masses. This technique is also appropriate for lesions lying at moderate depths in thin to average-size persons. In some cases, US can be employed to guide biopsy of small, deep, and solid abdominal masses; however, US-guided biopsy of these deep-seated masses (as well as of masses in obese patients) often proves difficult because of inadequate visualization resulting from sound attenuation in the soft tissues. Similarly, lesions located within or behind bone or gas-filled bowel cannot be easily visualized (a consequence of the nearly complete reflection of sound from bone or air interfaces).
US possesses several strengths as a guidance modality for percutaneous biopsy. It is readily available, inexpensive, and portable, and it provides guidance in multiple transverse, longitudinal, or oblique planes. Moreover, it offers real-time visualization of the needle tip as it passes through tissue planes into the target area,47 thereby allowing the surgeon to place the needle precisely and to avoid important intervening structures. In addition, color flow Doppler imaging can help prevent complications of needle placement by identifying the blood vessels involved with the mass, as well as any vessels lying within the needle path. Because of its real-time capabilities, US guidance has the potential to allow quicker, more accurate, and less expensive biopsies than CT guidance does.48 In theory, any mass that is well visualized with US should be amenable to US-guided biopsy. In practice, however, this modality remains best suited for superficial to moderately deep abdominal masses and for patients with a thin to average body habitus.
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| Figure 9. Percutaneous biopsy of large abdomina mass |
The utility of US notwithstanding, CT remains indispensable at our institution as a guidance method for percutaneous biopsy of most regions in the body. It is particularly useful when an abdominal mass is in a location that is inaccessible to US as a result of bowel gas or body habitus. In the abdomen, CT provides excellent spatial resolution of all structures between the skin and the mass, regardless of body habitus or lesion depth, and it provides an accurate image of the needle tip. We favor CT guidance for abdominal masses that are located deep in the abdomen or in the retroperitoneum. The only limitation of CT in this setting is that it does not offer continuous visualization of the needle during insertion and biopsy. In most cases, however, CT guidance can reliably establish the direction and depth of the needle [see Figure 9].
Numerous different needles, covering a broad spectrum of calibers, lengths, and tip designs, are commercially available for use in percutaneous image-guided fine-needle aspiration (FNA) biopsy. For convenience, these needles can be grouped into two main size categories: small caliber (20 to 25 gauge) and large caliber (14 to 19 gauge). Small-caliber needles are used primarily for cytologic analysis but may also be employed to obtain small pieces of tissue for histologic analysis. The flexible shaft of small-caliber needles allows them to be passed with minimal risk of tissue or organ laceration or of damage from tearing. Such needles are often used to confirm tumor recurrence or metastasis in patients with a pathologically confirmed primary malignancy. Large-caliber needles are typically used to obtain greater amounts of material for histologic or cytologic analysis.49 In practice, the choice of a biopsy needle is often influenced by whether the suspected pathology is benign or malignant. For example, large-caliber needles may be necessary to obtain a sufficiently large histologic specimen when certain types of malignancies (e.g., lymphoma) are suspected. When an inflammatory mass is suspected and material is needed for culture, however, a small-caliber needle may be preferred.
Additional considerations for image-guided biopsy include the accuracy, safety, and potential complications of the proposed technique. These considerations are essential for an evidence-based approach to diagnosis of an abdominal mass.
The reported accuracy of US-guided biopsy ranges from 66% to 97%. The location, size, and histologic origin of the abdominal mass appear to influence the diagnostic accuracy of the procedure.47 In a series that included 126 consecutive small (< 3 cm) solid masses distributed among various anatomic locations and histologic types, US-guided biopsies showed an overall accuracy of 91%.47 Biopsy results improved as the size of the mass increased: accuracy rose from 79% in masses 1 cm or less in diameter to 98% in masses 2 to 3 cm in diameter. The accuracy of US-guided biopsy in the liver, where most of the biopsies were performed, exceeded 96%. Another study found US-guided biopsy to be 91% accurate for abdominal masses less than 2.5 cm in diameter.50 Two organ-specific reviews concluded that US-guided biopsy of hepatic masses had an accuracy of 94%51 and that US-guided biopsy of pancreatic masses had an accuracy of 95%.52
The reported accuracy of CT-guided biopsy ranges from 80% to 100%. As with US-guided biopsy, the size, location, and histologic origin of the mass influence the results.53–55 In a study of 200 consecutive CT-guided needle biopsies, the overall accuracy for all sites biopsied was 95%. The reported organ-specific accuracy was as follows: kidneys, 100%; liver, 99%; retroperitoneum, 87.5%; and pancreas, 82%.56 In a prospective study of 1,000 consecutive CT-guided biopsies, the reported sensitivity was 91.8% and the specificity 98.9%.55 At our institution, as well as others, CT-guided biopsy is now considered a reliable tool for the diagnosis and classification of malignant abdominal lymphomas.57
The safety of image-guided percutaneous biopsy is well documented. Several large multi-institutional reviews reported major complication rates ranging from 0.05% to 0.18% and mortalities ranging from 0.008% to 0.031%.58–60 A large prospective study of 3,393 biopsies (1,825 US-guided; 1,568 CT-guided) documented an overall mortality of 0.06%, a major complication rate of 0.34% (0.3% with US; 0.5% with CT), and a minor complication rate of 2.9% (2.4% with US; 3.3% with CT).47 Procedure-related morbidity and mortality appear to be largely unaffected by whether a small-caliber or a large-caliber biopsy needle is used. A review of 11,700 patients who underwent percutaneous abdominal biopsy with 20- to 23-gauge needles found an overall complication rate of only 0.05% and an overall mortality of only 0.008%.58 A single-institution review of 8,000 US-guided needle biopsies performed with both small- and large-caliber needles reported equivalent results: a major complication rate of 0.187% and a mortality of 0.038%.61 Of the rare major complications that occur, hemorrhage is the most frequently reported; pneumothorax, pancreatitis, bile leakage, peritonitis, and needle track seeding may also develop.
Needle-track seeding remains an important theoretical consideration when an abdominal mass appears likely to be malignant. According to some investigators, percutaneous needle biopsy has the potential to seed between 103 to 104 tumor cells into the needle track.62,63 Nevertheless, tumor dissemination after percutaneous biopsy remains exceedingly rare: with fewer than 100 cases reported in the world literature, it has an estimated frequency of 0.005%,64–66 mostly occurring after biopsy of pancreatic, hepatic, or retroperitoneal masses. Poorly planned biopsies of malignant abdominal masses have the potential to exert adverse effects on subsequent surgery and to compromise local tumor control; fortunately, such negative consequences remain rare.
EUS-Guided Imaging and Biopsy
EUS provides unique imaging information because it involves the close apposition of a high-frequency ultrasound transducer, called an echoendoscope (whereby image resolution is directly related to frequency), to the structures being studied. As a result, it can delineate abdominal masses and associated structures with greater anatomic detail than standard transcutaneous ultrasonography can. In general, EUS-guided biopsy is well suited for abdominal masses that are too small for visualization by means of other cross-sectional imaging modalities or that are inaccessible to percutaneous biopsy.67 The most frequently used EUS device is the radial echoendoscope, which creates a 360° tomographic image perpendicular to the scope. The circumferential view obtained with this instrument facilitates orientation and therefore is more efficient for diagnostic imaging. Alternatively, the linear-array echoendoscope, which generates an image parallel to the shaft of the scope, may be used. This instrument produces high-quality gray-scale images, as well as color and duplex images. EUS-guided biopsy with a linear scanning system offers clear and consistent visualization of the biopsy needle along its entire path in real time, with excellent delineation of intervening tissues and without any interference from intestinal gas.
Advantages notwithstanding, EUS technology has several important limitations. As with all forms of ultrasonography, a substantial period is required before the operator achieves proficiency. EUS is highly operator dependent; when it is done by an inexperienced operator, the potential exists for serious misinterpretations. For example, if an operator obtains only one view of a mass in the head of the pancreas, the mass may appear to be invading vascular structures when it is not actually doing so. In the evaluation of pancreatic masses around vessels, the operator should always obtain multiple views. It cannot be overemphasized that EUS and EUS-guided biopsy require personnel with sufficient experience and skill in both ultrasonography and endoscopy.
EUS is frequently employed for diagnosis and staging of upper GI malignancies. In a large single-institution study of 267 pancreatic masses that were sampled by means of EUS-guided biopsy and subsequently resected, the overall diagnostic accuracy was 95.6%, the sensitivity was 94.6%, and the specificity was 100%.73 In studies of gastric and esophageal masses, diagnostic accuracy was related to the location of the biopsy,74 the histology of the disease,75 and the number of samples obtained. In one series that included more than 200 patients with esophageal or gastric masses, a diagnosis was made in 70% of patients after the first biopsy, 95% of patients after the fourth biopsy, and 98.9% of patients after the seventh biopsy.76 Several other studies have confirmed the high sensitivity and specificity of EUS-guided biopsy (especially for the diagnosis of extraluminal abdominal masses) and verified the safety of the procedure (reported complication rates range from 0.3% to 2%).68–71,77 It is worth noting that in the resection of a potentially curable abdominal mass, concern about needle-track contamination is obviated when the path of the needle is removed as part of the surgical specimen (as in pancreaticoduodenectomy for a pancreatic head mass or gastrectomy for a stomach mass).
We consider EUS-guided biopsy for the diagnosis of masses that are not readily accessible to percutaneous biopsy, on the grounds that it can obviate more invasive procedures (e.g., laparoscopy and laparotomy). In a 10-year study of the impact of EUS on patient management, 86% of patients required no further imaging, and 25% were able to avoid unnecessary laparotomy.77 Overall, EUS changed clinical management significantly in as many as one third of the 537 patients studied.77 Nevertheless, despite the high diagnostic yield achieved with EUS-guided biopsy, results that are negative for tumor should not always be interpreted as proving that no tumor is present; laparoscopic or open biopsy may still be indicated.
Diagnostic Laparoscopy
The available evidence now clearly supports the role of laparoscopy in the diagnosis and management of abdominal masses. We and others advocate the liberal use of laparoscopy as a primary staging tool for upper and lower GI malignancies, believing it to be a safe, cost-effective tool that offers a clear benefit in more than 20% of patients with these diseases.
78,79 Preventing unnecessary laparotomy in selected patients by performing diagnostic laparoscopy is associated with shorter hospital stays and earlier initiation of locoregional or systemic therapy. Moreover, laparoscopic ultrasonography80 and peritoneal cytology81 are known to provide added value in the staging of disease. Furthermore, diagnostic laparoscopy can safely provide tissue samples from suspected lymphomatous masses for full diagnostic analysis.82 With the growth of dedicated minimally invasive fellowships and the improved quality and availability of laparoscopic training for general surgery residents and related subspecialties, the skill sets required for diagnostic laparoscopy are coming to be more widely mastered, and the concerns once commonly expressed regarding intra-abdominal adhesions and effective biopsy techniques for abdominal masses now appear to be less problematic.Indications for Exploratory LaparotomyAdvances in diagnostic imaging, endoscopy, and minimally invasive surgery have nearly eliminated the need for open exploration for the sole purpose of establishing a diagnosis in patients with an abdominal mass. In selected cases, however, exploratory laparotomy may still help in the assessment of abdominal masses that were initially misinterpreted on preoperative evaluation. In general, exploratory laparotomy should be reserved for those rare instances in which other modalities have failed to yield crucial information needed for evaluation and diagnosis of an abdominal mass.
AcknowledgmentsFigure 1 Tom Moore.
Figure 2 Courtesy of Bimal C. Ghosh, M.D., F.A.C.S.
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Section 5 Gastrointestinal Tract and Abdomen
3 JaundiceJeffrey S. Barkun, MD, FACS
Approach to the jaundiced patient, including clinical evaluation and investigative studies, workup and management of posthepatic jaundice, and postoperative jaundice, is described.
Role of Spiral CT in Assessing ResectabilityPossible causes of posthepatic obstruction (other than choledocholithiasis) may be classified into three categories, depending on the location of the obstructing lesion (as suggested by the pattern of gallbladder and biliary tree dilatation on the ultrasonogram): the upper third of the biliary tree, the middle third, or the lower (distal) third. Once it has been determined that choledocholithiasis is unlikely, the most common cause of such obstruction is pancreatic cancer.
Assessment of the resectability of a tumor usually hinges on whether the superior mesenteric vein, the portal vein, the superior mesenteric artery, and the porta hepatis are free of tumor and on whether there is evidence of significant local adenopathy or extrapancreatic extension of tumor. Unfortunately, the majority of lesions will be clearly unresectable, either because of tumor extension or because of the presence of hepatic or peritoneal metastases.
Many imaging modalities are currently used to determine resectability, and several of these have been established as effective alternatives to direct cholangiography because they involve little if any morbidity. Their accuracy varies according to the underlying pathology and the expertise of the user. They have been studied mostly with respect to the staging and diagnosis of pancreatic, periampullary, and biliary hilar cancers.
For determining resectability and for staging lesions before operation, we rely mainly on spiral computed tomography. The advent and widespread availability of multidetector CT have made this modality the dominant second-line imaging method in cases of suspected pancreatic masses. For optimal evaluation of the pancreas, a fine-cut dual-phase (arterial phase and portal venous phase) scan should be obtained. Oral administration of water allows better evaluation of the duodenum and the ampulla.1
1. Stroszczynski C, Hunerbein M: Malignant biliary obstruction: value of imaging findings. Abdom Imaging 30:314, 2005 [PMID 15965779]
In patients with a suspected pancreatic tumor, direct fine-needle aspiration of the lesion at the time of endoscopic ultrasonography has become the gold standard for obtaining a tissue diagnosis. In the case of potentially resectable lesions, however, this measure adds very little to the decision-making process. The limited data currently available suggest that assays of tumor markers in serum and pancreatic fluid are useful, particularly for cystic lesions of the pancreas.1
At this point in the evaluation, patients can be referred either for cholangiography (endoscopic retrograde cholangiopancreatography [ERCP] or magnetic resonance cholangiopancreatography [MRCP]) to clarify a still-unclear diagnosis or for biliary decompression. MRI of the pancreas with MRCP continues to improve rapidly. It is a noninvasive modality that evaluates the pancreas, vasculature and the pancreatobiliary ductal system in a single examination, with the additional benefit of avoiding ionizing radiation and iodinated contrast agents.2 MRCP remains our test of choice for evaluation of middle- and upper-third lesions in cases in which decompression is not required.
In the event that none of these modalities point to a diagnosis, the use of 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) may be considered to help differentiate benign pancreatic conditions from malignant ones.3,4 Besides facilitating diagnosis, FDG-PET provides information regarding occult metastases and can be useful in detecting recurrent disease. Experience with FDG-PET is growing rapidly as this imaging modality becomes more readily accessible.
1. Brugge WR, Lauwers GY, Sahani D, et al: Current concepts: cystic neoplasms of the pancreas. N Engl J Med 351:1218, 2004 [PMID 15371579]
2. Keppke AL, Miller FH: Magnetic resonance imaging of the pancreas: the future is now. Semin Ultrasound CT MR 26:132, 2005 [PMID 15987063]
3. Delbeke D, Pinson CW: Pancreatic tumors: role of imaging in the diagnosis, staging and treatment. J Hepatobiliary Pancreat Surg 11:4, 2004 [PMID 15747028]
4. Heinrich S, Goerres G, Schafer M, et al: Positron emission tomography/computed tomography influences in the management of resectable pancreatic cancer and its cost-effectiveness. Ann Surg 242:235, 2005 [PMID 16041214]
When a patient has advanced malignant disease, drainage of the biliary system for palliation is not routinely indicated, because the risk of complications related to the procedure may outweigh the potential benefit. Indeed, the best treatment for a patient with asymptomatic obstructive jaundice and liver metastases may be supportive care alone. Biliary decompression is indicated if cholangitis or severe pruritus interferes with quality of life.
We consider a stent placed with ERCP to be the palliative modality of choice for advanced disease, though upper-third lesions may be managed most easily through the initial placement of an internal/external catheter at the time of percutaneous transhepatic cholangiography. Metal expandable stents remain patent longer than large conventional plastic stents, but the high price of the metal stents has kept them from being widely used, and their overall cost-effectiveness has yet to be clearly demonstrated. Whether plastic biliary stents should be replaced prophylactically or only after obstruction has occurred remains controversial; however, results from a randomized, controlled trial (RCT) favor the former approach. In another RCT, the use of prophylactic ciprofloxacin did not prolong stent patency but did reduce the incidence of cholangitis and improve quality of life scores.1
Because the left hepatic duct has a long extrahepatic segment that makes it more accessible, the preferred bypass technique for an obstructing upper-third lesion is a left (or segment 3) hepaticojejunostomy. This operation has superseded the Longmire procedure because it does not involve formal resection of liver parenchyma. Laparoscopic bypass techniques that make use of segment 3 have been developed, but their performance has yet to be formally assessed, and they cannot yet be incorporated into a management algorithm.2
1. Chan G, Barkun J, Barkun AN, et al: The role of ciprofloxacin in prolonging polyethylene biliary stent patency: a multicenter, double-blinded effectiveness study. J Gastrointest Surg 9:481, 2005 [PMID 15797227]
2. Date RS, Siriwardena AK: Current status of laparoscopic biliary bypass in the management of non-resectable peri-ampullary cancer. Pancreatology 5:325, 2005 [PMID 15980662]
The hilar plate is taken down to lengthen the hepatic duct segment available for subsequent anastomosis. Often, a formal hepatectomy or segmentectomy is required to ensure an adequate proximal margin of resection. If the resection must be carried out proximal to the hepatic duct bifurcation, several cholangiojejunostomies will have to be done to anastomose individual hepatic biliary branches. Frozen-section examination of the proximal and distal resection margins is important because of the propensity of tumors such as cholangiocarcinoma to spread in a submucosal or perineural plane.
The results of aggressive hilar tumor resections that included as much liver tissue as was necessary to obtain a negative margin appear to justify this approach. In cases of left hepatic involvement, resection of the caudate lobe (segments 1 and 9) is indicated as well.1
1. Jarnagin W, Shoup M: Surgical management of cholangiocarcinoma. Seminars in liver disease 24:189, 2004 [PMID 15192791]
An Expert Panel on Gastrointestinal Imaging evaluated various imaging strategies in the initial radiologic examination of patients with jaundice. They gauged the utility in differential diagnosis of the following modalities: ultrasound, endoscopic retrograde cholangiopancreatography, percutaneous transhepatic cholangiography, computed tomography, nuclear medicine, cholescintigraphy, and magnetic resonance imaging with magnetic resonance cholangiopancreatography. To view the complete guidelines, click on the following link: http://www.guideline.gov/summary/summary.aspx?doc_id=8294&nbr=004626
For further information, see Section 5, Chapter 3, Jaundice.
Abdominal Mass
Question 1 A 60-year-old woman presents to the office complaining of abdominal pain and distention. She states that her abdomen has been enlarging over the past 6 months. She has had some associated nausea and admits to a 15-lb weight loss over this period. Physical examination reveals a fixed, mildly tender, 7 cm mass in the right upper quadrant. An ultrasound is planned for further evaluation of this right upper quadrant abdominal mass.
Which of the following is a disadvantage of ultrasonography (US) in the evaluation of abdominal masses?
Please choose the single most appropriate answer to the question - Extended preparation time
Sorry, this is incorrect. Try again!
- High cost
- Limited availability
- Quality of results depends on the operator's technical proficiency
This is correct.
Objective: To understand the role of US in the evaluation of an abdominal massCompared with other modalities, US has several advantages in the evaluation of suspected abdominal masses. These include its widespread availability, speed of use, the absence of ionizing radiation, low cost, and the ability to document the size, consistency, and origin of a mass with real-time images. One disadvantage of US is the extent to which the quality of the results depends on the technical proficiency and diligence of the operator or technician. In the hands of an inexperienced operator, US may yield inconclusive or untrustworthy results that contribute to delayed diagnosis or even misdiagnosis. Another disadvantage of US is its inability to visualize the entire abdominal cavity as a consequence of the acoustic barriers presented by gas-containing structures (e.g., the bowel) and the absorptive interfaces (acoustic shadowing) provided by soft tissue and bone. For optimal visualization of abdominal masses, US should be performed through "acoustic windows" that allow adequate transmission of sound. Accordingly, US is most effective as a tool for evaluating masses in those regions of the abdomen where an acoustic window exists (e.g., the right and left upper quadrants and the pelvis). The shortcomings of US can be compensated for by employing other cross-sectional imaging modalities.
Question 2 A 62-year-old man presents for his routine yearly physical examination. He is very healthy and has no specific complaints. Physical examination of the abdomen, however, reveals a firm, nontender, 5 cm mass in his left upper quadrant. A computed tomography scan shows a lesion isolated to the stomach. A CT-guided biopsy is planned to confirm a diagnosis.
Which of the following statements regarding CT-guided percutaneous biopsy is true? Please choose the single most appropriate answer to the question - Procedure-related morbidity increases when a large-caliber needle is used
- Tumor dissemination after percutaneous biopsy is relatively common
- Hemorrhage is the most frequently reported major complication
Objective: To know the complications associated with CT-guided percutaneous biopsy - All of the above
Question 3 A 50-year-old man presents to the office complaining of intermittent left upper quadrant pain, which he has been experiencing for 3 months. He also complains of associated nausea and vomiting after eating. His physical examination is unremarkable; however, laboratory work reveals elevations in the amylase and lipase levels. A subsequent CT scan reveals a mass in the head of the pancreas. Endoscopic ultrasonography (EUS) with possible biopsy is scheduled to better delineate this lesion.
Which of the following statements regarding EUS-guided biopsy is true? Please choose the single most appropriate answer to the question - It is superior to other cross-sectional imaging modalities for detection and staging of pancreatic, gastric, and esophageal masses
Objective: To understand the advantages of EUS-guided biopsyEUA has proved to be superior to other cross-sectional imaging modalities for the detection and staging of pancreatic, gastric, and esophageal masses. For instance, in a patient with a pancreatic mass, EUS not only identifies the size of the mass and the peripancreatic lymph nodes but also delineates the relations of these structures to major blood vessels. EUS has also proved to be helpful in selecting patients for various neoadjuvant protocols. It is well suited for abdominal masses that are too small for visualization by means of other cross-sectional imaging modalities and offers clear and consistent visualization of the biopsy needle along its entire path in real time without any interference from intestinal gas. As with all forms of US, a substantial period is required before the operator achieves proficiency, and it is highly operator dependent. When it is done by an inexperienced operator, the potential exists for serious misinterpretations. For example, if an operator obtains only one view of a mass in the head of the pancreas, the mass may appear to be invading vascular structures when it is not actually doing so. In the evaluation of pancreatic masses around vessels, the operator should always obtain multiple views. - It tends to be hampered by the interference from intestinal gas
- It increases the risk of seeding the needle track with malignant cells
- It is quickly learned and highly operator independent
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