(Radiographics. 1999;19:S179-S200.)
© RSNA, 1999
Nongynecologic Applications of Transvaginal US1
Nizar Damani, MB,BS, FFR(RCSI), FRCR, 2 and
Stephanie R. Wilson, MD, FRCP
1 From the Department of Medical Imaging, The Toronto Hospital, University of Toronto, 200 Elizabeth St, Toronto, Ontario M5G 2C4, Canada. Received January 7, 1999; revision requested February 15 and received March 21; accepted March 26. Address reprint requests to S.R.W.
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Abstract
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Transvaginal ultrasonography (US) is a noninvasive, readily available imaging technique that has greatly enhanced diagnostic sensitivity and accuracy for both gynecologic and nongynecologic disease. High-frequency US probes placed in the vagina allow high-resolution assessment of all the pelvic viscera, including portions of the gut and urinary tract. In addition, they allow visualization of the peritoneum of the pelvic pouch and the pelvic side walls without interference from bowel gas or adipose tissue. Evaluation of these areas requires a modified US technique that includes the use of the highest-frequency probes with angulation of the transducer to allow assessment of the region of interest. In women of childbearing age, the similarity of symptoms in gynecologic and gastrointestinal tract disease in particular underscores the potential utility of transvaginal US, which may, for example, help differentiate appendicitis in a pelvic appendix from pelvic inflammatory disease. Transvaginal US may also help determine the correct course of therapy, thereby improving patient management. Other indications for transvaginal US include assessment for pelvic appendicitis and diverticulitis, rectal and perianal complications of Crohn disease, and ureteric and bladder calculi and tumors as well as evaluation of the anal sphincters in women with fecal incontinence. Transvaginal US is also superior to routine US in the detection and characterization of ascites and peritoneal disease. Transvaginal US examination should include the entire pelvic cavity and contents, especially in women at risk for pelvic sepsis or peritoneal disease.
Index Terms: Bladder, diseases, 83.214, 83.3192 • Bladder neoplasms, 83.321, 83.328 • Gastrointestinal tract, diseases, 70.262, 75.273, 751.291, 757.40, 791.3196 • Gastrointestinal tract, neoplasms, 70.30 • Pelvic organs, diseases, 85.20, 85.30 • Pelvic organs, US, 85.12989 • Peritoneum, abnormalities, 791.3196 • Peritoneum, fluid, 791.77 • Ultrasound (US), utilization, **.129893 • Ureter, calculi, 82.811
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INTRODUCTION
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The value of transvaginal ultrasonography (US) in gynecologic diagnosis is well recognized. Less familiar is its potential diagnostic value in other organ systems. Transvaginal ultrasonography (US) with high-frequency US probes provides excellent resolution. Placement of these probes in the vagina close to the uterus and ovaries allows imaging without interference from interposed bowel gas or attenuation of the US beam by adipose tissue. The placement of the US probe in proximity to the region of interest and the high resolution of the transducers have led to many improvements in diagnosis involving the gynecologic organs. However, such improvements also apply to many other anatomic areas that can be accessed from the vaginal vault (1). These include portions of the urinary tract (distal ureters, bladder, urethra) and gastrointestinal tract (pelvic small bowel loops, sigmoid colon, rectum, anal canal, pelvic appendix), the peritoneum of the pelvic pouch, the pelvic vasculature, and the soft tissues of the retroperitoneum and pelvic side wall.
Since the introduction of transvaginal US at our institution, we have steadily increased the number of applications for this procedure. Some endeavors have proved particularly useful and are now part of our imaging protocol. In some cases, transvaginal US has largely replaced other US examinations (eg, transanal US in anal sphincter evaluation). In other areas, the addition of transvaginal US has led to marked improvement in our diagnostic capability while increasing the number of US procedures required. In some patients, definitive US findings have led to the institution of appropriate therapy following US without the need for further imaging (eg, computed tomography [CT], magnetic resonance imaging), which might otherwise be necessary if the US findings were equivocal or negative.
In this article, we describe and illustrate the spectrum of nongynecologic (ie, gastrointestinal, urinary tract, peritoneal, vascular) applications of transvaginal US with emphasis on those applications having the greatest impact on patient care.
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GASTROINTESTINAL APPLICATIONS
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Indications for routine abdominal and pelvic US in the investigation of gut disease include suspected acute appendicitis (2) and acute diverticulitis (3) as well as complications of Crohn disease (4). Although routine US generally has excellent diagnostic sensitivity and specificity (2–4), it may yield negative or misleading results in patients in whom the pathologic process is located deep in the pelvis. However, the addition of transvaginal assessment to a routine pelvic US examination in these patients may allow accurate diagnosis with differentiation of gastrointestinal from gynecologic disease.
Diagnosis may be especially problematic in women of childbearing age because nonspecific signs and symptoms including pelvic pain, fever, and a pelvic mass may be associated with a gynecologic condition or an inflammatory process related to the bowel (5). Patient treatment is significantly improved by correct noninvasive diagnosis with avoidance of unnecessary laparotomy and institution of appropriate therapy (6).
Evaluation of the gut with transvaginal US requires appreciation of both normal and abnormal US appearances of the gut as well as the appearances of inflamed perienteric fat, phlegmon, and abscess. At cross-sectional US, the normal gut wall appears as a series of alternating echogenic and hypoechoic concentric rings corresponding to the histologic layers of the wall ("gut signature") (7,8). Gut wall thickness in healthy patients varies with luminal distention but is generally 3 mm or less for both the small and large intestines. The collapsed rectum may appear slightly thicker. Alterations in the gut signature may include focal or diffuse wall thickening with or without wall layer preservation.
Inflammation of the perienteric fat is one of the most easily recognized and frequent manifestations of inflammatory processes in the gastrointestinal tract. Its identification at CT is well documented as a valuable indicator of a local inflammatory process even in the absence of other findings (9). Its US appearance may be less familiar but is equally valuable as an aid to diagnosis. At US, inflamed fat appears as a uniformly echogenic "mass effect," often with increased vascularity at color Doppler US. A phlegmon appears as a focal area of hypoechogenicity with irregular margins within an area of inflamed fat, whereas an abscess manifests as a fluid collection with or without gas bubbles within a mass (8).
Acute Appendicitis
Transabdominal US is reported to have a sensitivity of 80%–94% in the detection of appendicitis when the appendix is identified as a blind-ended, noncompressible, aperistaltic tubular structure with a gut signature arising from the base of the cecum (10). The diameter of an inflamed appendix is generally greater than 6 mm (10). False-negative diagnoses are usually due to either an unusual position or incomplete visualization of the appendix (10). This is particularly true when the appendix has a retrocecal or pelvic location. A retrocecal appendix can be seen at coronal US performed with the transducer parallel to the iliac wing to optimize visualization posterior to the cecum (11). In contrast, a pelvic appendix, which extends medially into the pelvis toward the pouch of Douglas, is best depicted at transvaginal US in most women (Fig 1).
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Figure 1a. Acute appendicitis. (a) Suprapubic US image shows inflamed fat surrounding an abnormal loop of gut (arrows), which leaves the visualized field of view. The loop cannot be definitely confirmed as blind-ended. (b) Transvaginal US image helps confirm that the tubular area (ie, the appendix) is blind-ended (arrows).
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Figure 1b. Acute appendicitis. (a) Suprapubic US image shows inflamed fat surrounding an abnormal loop of gut (arrows), which leaves the visualized field of view. The loop cannot be definitely confirmed as blind-ended. (b) Transvaginal US image helps confirm that the tubular area (ie, the appendix) is blind-ended (arrows).
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As with routine US, identification of the appendix at transvaginal US as a blind-ended, aperistaltic tubular structure constitutes a positive diagnosis for acute appendicitis. A threshold diameter of 6 mm, above which acute appendicitis is likely to be present, is equally diagnostic regardless of transducer placement. Compression of the appendix and confirmation that the appendix originates from the base of the cecum are often difficult with transvaginal probes. However, the high-resolution assessment of the appendix makes these limitations seem unimportant. Discontinuity in the echogenic submucosa of the appendix is suggestive of mural necrosis and impending perforation (12). Inflamed adjacent mesenteric or omental fat is seen with extension of the inflammation to the serosal surface. If perforation occurs, a localized periappendiceal fluid collection or abscess may be seen.
Appendicitis of a pelvic appendix is relatively uncommon, accounting for only 21% of cases (13); however, it is also the type of appendicitis that is most frequently confused with gynecologic disease and consequently misdiagnosed (14). Furthermore, coexistent gynecologic disease may be present in a patient with acute appendicitis and may lead to an incorrect diagnosis if some of the findings are missed or misinterpreted. Therefore, we recommend transvaginal US for women of childbearing age with fever, pelvic pain, or a pelvic mass whenever gynecologic and gastrointestinal disease cannot be clearly differentiated at routine transabdominal and pelvic US.
Acute Diverticulitis
Acute diverticulitis typically manifests at clinical examination with left lower quadrant pain and tenderness, elevated white blood cell count, and fever (15). The diagnosis is readily confirmed with cross-sectional CT or US (3,16). Because most affected patients are in the 5th or 6th decade of life or older, confusion with gynecologic disease with resulting misdiagnosis occurs much less frequently than in acute appendicitis. Nonetheless, we have encountered many premenopausal as well as postmenopausal women who were not previously suspected of having acute diverticulitis that was demonstrated at transvaginal US: In the vast majority of these patients, gut disease was not evident at routine transabdominal US. As with appendicitis, this occurs when the diseased segment of the colon is located deep within the true pelvis.
At US, acute diverticulitis is associated with thickening of long segments of the gut wall with prominence of the outer hypoechoic layer (muscularis propria) (3,17). Inflamed diverticula manifest as bright echogenic foci with acoustic shadowing that usually project beyond the wall of the thickened gut (3) (Fig 2). Localized perforation is accompanied by inflammation of the perienteric fat, phlegmon, and abscess formation (Fig 3).
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Figures 2, 3. (2) Acute diverticulitis. Cross-sectional transvaginal US image of a thickened sigmoid colon shows an inflamed diverticulum as a shadowing echogenic focus projecting beyond the margin of the gut (arrow). (3) Diverticular abscess. A suprapubic US image (not shown) was inconclusive although findings were suggestive of inflammatory change. (a) Transvaginal US image shows an abscess as an ill-defined mass with multiple bright echoes representing gas (arrows). The abscess is adjacent to the margin of a loop of sigmoid colon (arrowheads). (b) CT scan helps confirm the gas-containing abscess (arrows). (c) Transvaginal US image shows a J-shaped catheter coiled within the abscess cavity. (d) CT scan obtained following US-guided transvaginal insertion of the drainage catheter helps confirm correct placement of the catheter within the abscess cavity.
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Figures 2, 3. (2) Acute diverticulitis. Cross-sectional transvaginal US image of a thickened sigmoid colon shows an inflamed diverticulum as a shadowing echogenic focus projecting beyond the margin of the gut (arrow). (3) Diverticular abscess. A suprapubic US image (not shown) was inconclusive although findings were suggestive of inflammatory change. (a) Transvaginal US image shows an abscess as an ill-defined mass with multiple bright echoes representing gas (arrows). The abscess is adjacent to the margin of a loop of sigmoid colon (arrowheads). (b) CT scan helps confirm the gas-containing abscess (arrows). (c) Transvaginal US image shows a J-shaped catheter coiled within the abscess cavity. (d) CT scan obtained following US-guided transvaginal insertion of the drainage catheter helps confirm correct placement of the catheter within the abscess cavity.
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Figures 2, 3. (2) Acute diverticulitis. Cross-sectional transvaginal US image of a thickened sigmoid colon shows an inflamed diverticulum as a shadowing echogenic focus projecting beyond the margin of the gut (arrow). (3) Diverticular abscess. A suprapubic US image (not shown) was inconclusive although findings were suggestive of inflammatory change. (a) Transvaginal US image shows an abscess as an ill-defined mass with multiple bright echoes representing gas (arrows). The abscess is adjacent to the margin of a loop of sigmoid colon (arrowheads). (b) CT scan helps confirm the gas-containing abscess (arrows). (c) Transvaginal US image shows a J-shaped catheter coiled within the abscess cavity. (d) CT scan obtained following US-guided transvaginal insertion of the drainage catheter helps confirm correct placement of the catheter within the abscess cavity.
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Figures 2, 3. (2) Acute diverticulitis. Cross-sectional transvaginal US image of a thickened sigmoid colon shows an inflamed diverticulum as a shadowing echogenic focus projecting beyond the margin of the gut (arrow). (3) Diverticular abscess. A suprapubic US image (not shown) was inconclusive although findings were suggestive of inflammatory change. (a) Transvaginal US image shows an abscess as an ill-defined mass with multiple bright echoes representing gas (arrows). The abscess is adjacent to the margin of a loop of sigmoid colon (arrowheads). (b) CT scan helps confirm the gas-containing abscess (arrows). (c) Transvaginal US image shows a J-shaped catheter coiled within the abscess cavity. (d) CT scan obtained following US-guided transvaginal insertion of the drainage catheter helps confirm correct placement of the catheter within the abscess cavity.
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Figures 2, 3. (2) Acute diverticulitis. Cross-sectional transvaginal US image of a thickened sigmoid colon shows an inflamed diverticulum as a shadowing echogenic focus projecting beyond the margin of the gut (arrow). (3) Diverticular abscess. A suprapubic US image (not shown) was inconclusive although findings were suggestive of inflammatory change. (a) Transvaginal US image shows an abscess as an ill-defined mass with multiple bright echoes representing gas (arrows). The abscess is adjacent to the margin of a loop of sigmoid colon (arrowheads). (b) CT scan helps confirm the gas-containing abscess (arrows). (c) Transvaginal US image shows a J-shaped catheter coiled within the abscess cavity. (d) CT scan obtained following US-guided transvaginal insertion of the drainage catheter helps confirm correct placement of the catheter within the abscess cavity.
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Optimal guidance for drainage of a deep pelvic abscess is often achieved with transvaginal techniques (18) (Fig 3). The procedure is performed with the patient supine with the legs widely separated as for all transvaginal examinations. A transvaginal probe equipped with a biopsy guide is placed in the vagina such that the most direct approach to the abscess is identified. The guidance path must avoid all of the pelvic organs and vascular structures. A long coaxial needle is advanced through the guide into the abscess, and fluid is aspirated to confirm the presence of pus. A decision is then made, often based on the size of the abscess, as to whether drainage can be accomplished with US alone or if fluoroscopy is required. Contrast material may be injected into the abscess and fluoroscopy used to confirm encapsulation of the fluid. A J wire is then advanced through the needle into the abscess, after which the probe, the guide, and the needle are removed. The tract is dilated to the appropriate size, and a drain is inserted.
Depending on the size of the abscess, simple aspiration may be preferable to drainage because transvaginal drainage procedures are painful for the patient. In considering this procedure, one must weigh the advantage of accessibility against the need for significant analgesia and sedation.
Crohn Disease
Crohn disease is a chronic, granulomatous inflammatory process that affects the gastrointestinal tract. The disease is characterized by multiple remissions and exacerbations and is diagnosed most often in young patients (19). US does not involve the use of ionizing radiation and can help assess the mural and extramural abnormalities in Crohn disease and help identify patients in whom the need for surgery or intervention would justify the use of CT (4,20).
Gut wall thickening (21) (Fig 4), inflammation of the mesenteric fat, mesenteric lymphadenopathy, strictures, and fistulas can all be appreciated at US (23,24). In addition, inflammatory masses can be characterized as abscess or phlegmon. As with other gastrointestinal diseases, Crohn disease involvement of parts of the gut in the true pelvis lends itself to transvaginal evaluation (25). Furthermore, the high prevalence of perianal disease in patients with Crohn disease makes transvaginal US an optimal and usually painless technique for characterizing this pathologic condition in women. In contrast, transrectal and transanal US are often less helpful and may cause the patient considerably more discomfort.
Imaging evaluation of the sigmoid colon and pelvic small intestine is performed with routine transvaginal technique, whereas perianal disease and Crohn disease of the rectum require a modified approach. The extreme proximity of the rectum and anal canal to the vagina allows use of a higher-frequency probe (up to 10 MHz) than is used in routine transvaginal procedures (5.0–7.5 MHz). The rectum is visualized by elevating the examining hand toward the symphysis pubis to achieve extreme angulation of the probe in a posterior direction. This will usually allow evaluation of the region of the rectosigmoid and of the more cephalic part of the rectum itself. Gradual withdrawal of the transvaginal probe while maintaining the posterior angulation will allow progressive visualization of the entire rectum and ultimately the anal canal. Rotation of the transducer 90° will produce both longitudinal and cross-sectional images. The anal canal itself is often better seen with a side-fired biplane transvaginal probe than with the more traditional end-fired probe. Evaluation of perianal fistula is accomplished with a combined transvaginal and transperineal approach, which allows examination of the tract from its point of origin in the gut to its cutaneous opening. In most patients, a transvaginal probe can be used for the entire examination.
Gut wall thickening in Crohn disease is usually symmetric with partial or total loss of the gut signature, findings that indicate transmural edema, inflammation, or fibrosis. Like inflamed fat from any other cause, inflamed perienteric fat in Crohn disease manifests as an echogenic mass effect (9). Complications of Crohn disease such as strictures manifest as luminal narrowing. Fistula formation is seen as a hypoechoic linear tract, often containing gas bubbles, between the involved organ and the gut. Rectovaginal and enterovesical fistulas in particular are seen much more clearly at transvaginal US than at routine US (Figs 5, 6). Palpation of the abdomen at the time of the procedure may prove helpful by causing gas to percolate through the fistula, thus making the fistula easier to detect because the bright bubbles of gas outside the lumen of the gut are readily appreciated at US.
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Figures 5, 6. (5) Crohn disease with an enterovesical fistula. (a) Suprapubic US image shows a superficial abscess (a). A tract is seen running from the abscess to the bladder dome and appears as a thin, hypoechoic line (arrows). (b) Transvaginal US image shows the tract entering the bladder (arrows). There is evidence of marked mucosal edema (arrowheads). (6) Permission to reprint this figure electronically was denied by the publisher. See print version.
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Figures 5, 6. (5) Crohn disease with an enterovesical fistula. (a) Suprapubic US image shows a superficial abscess (a). A tract is seen running from the abscess to the bladder dome and appears as a thin, hypoechoic line (arrows). (b) Transvaginal US image shows the tract entering the bladder (arrows). There is evidence of marked mucosal edema (arrowheads). (6) Permission to reprint this figure electronically was denied by the publisher. See print version.
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Figures 5, 6. (5) Crohn disease with an enterovesical fistula. (a) Suprapubic US image shows a superficial abscess (a). A tract is seen running from the abscess to the bladder dome and appears as a thin, hypoechoic line (arrows). (b) Transvaginal US image shows the tract entering the bladder (arrows). There is evidence of marked mucosal edema (arrowheads). (6) Permission to reprint this figure electronically was denied by the publisher. See print version.
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Neoplasms
Detection of gastrointestinal neoplasms is a very uncommon indication for US. However, many primary as well as secondary neoplasms, including those of the rectosigmoid colon and even of the small intestine, may be seen at transvaginal US depending on their locations relative to the vaginal vault. Transrectal imaging is the most efficient noninvasive method of evaluating rectal cancer preoperatively (26). However, staging accuracy may be enhanced with transvaginal imaging, which provides more adequate visualization of rectovaginal space infiltration and lymph node enlargement (27,28) (Figs 7, 8). Furthermore, transvaginal imaging may improve assessment of stenosing rectal cancers that are inaccessible to the transrectal probe. Although transvaginal imaging cannot always help visualize all the rectal wall layers or their neoplastic infiltration, we have achieved better results in preoperative staging of rectal cancer in women by combining transrectal and transvaginal imaging.
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Figure 7a. Annular constricting carcinoma of the rectum. (a) Transrectal US image shows a rectal carcinoma end on as a black mass surrounding the narrowed lumen (arrows). The probe could not be advanced into the narrowed segment. (b, c) Long-axis (b) and cross-sectional (c) transvaginal US images of the rectum show nodular annular thickening of the rectal wall with total layer destruction. The lumen appears as a white central area (L), whereas the tumor appears black (arrows). Transvaginal US images are superior to transrectal images for assessing the length of annular lesions and the invasion of perirectal fat.
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Figure 7b. Annular constricting carcinoma of the rectum. (a) Transrectal US image shows a rectal carcinoma end on as a black mass surrounding the narrowed lumen (arrows). The probe could not be advanced into the narrowed segment. (b, c) Long-axis (b) and cross-sectional (c) transvaginal US images of the rectum show nodular annular thickening of the rectal wall with total layer destruction. The lumen appears as a white central area (L), whereas the tumor appears black (arrows). Transvaginal US images are superior to transrectal images for assessing the length of annular lesions and the invasion of perirectal fat.
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Figure 7c. Annular constricting carcinoma of the rectum. (a) Transrectal US image shows a rectal carcinoma end on as a black mass surrounding the narrowed lumen (arrows). The probe could not be advanced into the narrowed segment. (b, c) Long-axis (b) and cross-sectional (c) transvaginal US images of the rectum show nodular annular thickening of the rectal wall with total layer destruction. The lumen appears as a white central area (L), whereas the tumor appears black (arrows). Transvaginal US images are superior to transrectal images for assessing the length of annular lesions and the invasion of perirectal fat.
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Figure 8a. Rectal carcinoma with transmural invasion of the wall and perirectal nodes in a 51-year-old woman with rectal bleeding that was originally thought to be related to hemorrhoids. (a) Transverse transvaginal US image of the rectum shows a hypoechoic tumor mass (m) involving the left lateral wall of the rectum (arrows). The tumor involves the mucosa between the 2-o'clock and 3-o'clock positions. (b) On a transvaginal US image of the rectum, a tumor seed (s) is seen separate from the primary tumor (m) in the rectovaginal septum.
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Figure 8b. Rectal carcinoma with transmural invasion of the wall and perirectal nodes in a 51-year-old woman with rectal bleeding that was originally thought to be related to hemorrhoids. (a) Transverse transvaginal US image of the rectum shows a hypoechoic tumor mass (m) involving the left lateral wall of the rectum (arrows). The tumor involves the mucosa between the 2-o'clock and 3-o'clock positions. (b) On a transvaginal US image of the rectum, a tumor seed (s) is seen separate from the primary tumor (m) in the rectovaginal septum.
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Differential diagnosis of gut wall masses includes mesenchymal tumor, lymphoma, gut metastasis, and adenocarcinoma. If present, the tumor can be seen as focal mural thickening or as a localized, round, solid, hypoechoic or heterogeneous intra- or extraluminal mass. Identification of specific layer involvement may be helpful in differential diagnosis. For example, adenocarcinoma demonstrates mucosal involvement in contrast to both mesenchymal tumors and gut wall metastases, which more commonly involve the outer layers of the gut wall. On magnified views, mesenchymal tumors are often seen to have outgrown their blood supply and demonstrate ulceration and necrosis (29). Annular carcinoma manifests as a pseudokidney or target sign at US, with the black outer margin representing the thickened gut wall and the white inner region representing the gut lumen (28). Nonneoplastic masses may also involve the gut wall and mimic a primary or secondary neoplasm. Transvaginal imaging may depict endometriomas involving the rectal or small bowel wall that are indistinguishable from mesenchymal tumors (Fig 9).
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Figure 9a. Endometrioma of the rectal wall in a 47-year-old woman with dyspareunia. Long-axis (a) and cross-sectional (b) transvaginal US images of the rectum show a focal hypoechoic mass (M) involving and protruding from the outer layer of the rectal wall.
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Figure 9b. Endometrioma of the rectal wall in a 47-year-old woman with dyspareunia. Long-axis (a) and cross-sectional (b) transvaginal US images of the rectum show a focal hypoechoic mass (M) involving and protruding from the outer layer of the rectal wall.
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Fecal Incontinence
Because the anus is in proximity to the posterior vaginal wall, damage to the anal sphincters is a well-documented sequela of complicated vaginal delivery (30,31). Fecal incontinence is the most common indication for US evaluation of the anus. Although the majority of affected patients are young women of childbearing age, older women may have similar problems due to muscular dysfunction (32,33). Occasionally, patients (both men and women) may have sphincter damage following surgery for fistula or even for hemorrhoid repair.
Transanal US has been the technique of choice for the assessment of the anorectum and anal sphincters in patients with fecal incontinence (34,35). However, this technique requires special adapters for transrectal probes and may compress the sphincters and distort the anatomic arrangement of the sphincter muscles. In addition, it scans the sphincters in the extreme near field of the transducer and consequently does not always provide optimal resolution of the muscle layers (32).
In contrast, imaging the anal canal with transvaginal probes positioned close to the introitus affords excellent evaluation of the anal sphincters and surrounding muscles in their resting state. Placing the probe in the vagina rather than within the anal canal itself allows positioning of the area of interest between 3 and 5 cm from the transducer crystal, which is the optimal zone for resolution, as compared with the extreme near field used with a transanal approach.
A comparison study of transvaginal and transanal US performed in women at our institution showed the two procedures to be in excellent agreement and to have similar reliability (36). In addition to preferring the transvaginal technique for assessment of the anal sphincters themselves, we also prefer the technique for its clearer assessment of the perineal body and puborectal sling. Transperineal imaging is also optimal in a patient shown to have perianal inflammatory disease if a transvaginal probe is used because these probes may be placed anywhere, always offering the advantages of high-frequency resolution.
Transducers used for anal sphincter evaluation may include side-fired transvaginal probes, which have limited availability on most conventional US imagers, or the more traditional end-fired probe, which is commonly used for transvaginal imaging. If the end-fired probe is selected, the examining hand must be markedly elevated toward the symphysis pubis so that the crystal is firing toward the anal canal. Imaging is performed with the patient in the dorsal lithotomy position with the probe inserted about 3 cm into the vagina. Gradual withdrawal of the probe will produce serial axial images of the anal canal. Long-axis images of the canal are produced by imaging in the perpendicular plane if a biplane transducer is used. More commonly, rotation of the end-fired transvaginal probe 90° from the plane in which the optimal axial image was obtained will show the anal canal and anorectal junction in long axis. Depression of the examining hand toward the table is often helpful for imaging the anal canal in a plane perpendicular to the transducer crystal. Imaging is also optimized with use of a water-filled balloon surrounding the transducer crystal.
The internal anal sphincter appears as a hypoechoic ring encircling the anal canal in continuity with the outer muscular layer of the rectum (Fig 10). The external sphincter appears as a less well-defined hyperechoic ring that blends imperceptibly with the perienteric fat (33). The anorectal junction is easily recognized by a change in shape: The more cephalic rectum appears flattened and oval, whereas the more caudal anal canal appears circular or round (Fig 10). The normal anal canal is approximately 3 cm in length. The puborectal muscle is a slinglike structure that diverges anteriorly and is related to the posterior and lateral margins of the anal canal (37).
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Figure 10a. Normal anal canal. (a) On a transverse transvaginal US image, the rectum (seen at the anorectal junction) has an oval, multilayered appearance. The outer black ring represents the muscularis propria (m). The puborectal muscle is echogenic and diverges anteriorly. (b) On a transverse US image, the normal anal canal appears round. The distance between the vaginal probe and the anal canal is greater than that between the probe and the rectum because of the depth of the perineal body. The internal anal sphincter (IS), which appears as a thick black ring, is continuous with the muscularis propria of the rectal wall. The external anal sphincter is echogenic and less well defined. (c) US image obtained with rotation of the end-fired transvaginal probe shows the anal canal in long axis. The anorectal junction (R) is on the left side of the image with the external opening on the right side. The thick black bands seen anteriorly and posteriorly represent the internal sphincter (IS).
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Figure 10b. Normal anal canal. (a) On a transverse transvaginal US image, the rectum (seen at the anorectal junction) has an oval, multilayered appearance. The outer black ring represents the muscularis propria (m). The puborectal muscle is echogenic and diverges anteriorly. (b) On a transverse US image, the normal anal canal appears round. The distance between the vaginal probe and the anal canal is greater than that between the probe and the rectum because of the depth of the perineal body. The internal anal sphincter (IS), which appears as a thick black ring, is continuous with the muscularis propria of the rectal wall. The external anal sphincter is echogenic and less well defined. (c) US image obtained with rotation of the end-fired transvaginal probe shows the anal canal in long axis. The anorectal junction (R) is on the left side of the image with the external opening on the right side. The thick black bands seen anteriorly and posteriorly represent the internal sphincter (IS).
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Figure 10c. Normal anal canal. (a) On a transverse transvaginal US image, the rectum (seen at the anorectal junction) has an oval, multilayered appearance. The outer black ring represents the muscularis propria (m). The puborectal muscle is echogenic and diverges anteriorly. (b) On a transverse US image, the normal anal canal appears round. The distance between the vaginal probe and the anal canal is greater than that between the probe and the rectum because of the depth of the perineal body. The internal anal sphincter (IS), which appears as a thick black ring, is continuous with the muscularis propria of the rectal wall. The external anal sphincter is echogenic and less well defined. (c) US image obtained with rotation of the end-fired transvaginal probe shows the anal canal in long axis. The anorectal junction (R) is on the left side of the image with the external opening on the right side. The thick black bands seen anteriorly and posteriorly represent the internal sphincter (IS).
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Tears in the internal sphincter are seen as defects or discontinuity of the hypoechoic ring (Figs 11, 12). Defects in the external ring are harder to appreciate and usually appear hypoechoic or black compared with the more echogenic muscular fibers (Figs 12, 13). Defects secondary to birth trauma most commonly involve the anterior aspect of the anal canal, as one might expect given their mechanism of production. They may also be associated with loss or destruction of the perineal body, in which case the anal canal will be abnormally close to the transducer placed in the vagina (Fig 14). With nontraumatic dysfunction of the anal sphincters, there may be thinning or the sphincter may look entirely normal.
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Figures 11-14. (11) Scar tissue in the rectovaginal septum in a young woman with fecal incontinence following traumatic obstetric delivery. Transvaginal US image shows a defect in the hypoechoic black ring of the internal anal sphincter anteriorly from the 10-o'clock to the 12-o'clock position. A large mass of scar tissue (S) is seen expanding the rectovaginal septum and increasing the distance from the anal canal to the vaginal probe. (12) Tear of the anal sphincter in a 40-year-old woman with fecal incontinence following a fourth-degree tear at obstetric delivery. Transvaginal US image shows a deficiency in the hypoechoic black ring of the internal anal sphincter anteriorly at the 12-o'clock position. The tear in the external anal sphincter appears as a hypoechoic wedge in the normal echogenic muscle (arrows). (13) Permission to reprint this figure electronically was denied by the publisher. See print version. (14) Tear of the internal and external anal sphincters with loss of the perineal body. Transvaginal US image shows a large defect in the internal anal sphincter anteriorly between the 9-o'clock and 2-o'clock positions. The external anal sphincter is extremely thin anteriorly. There is virtually no rectovaginal septum or perineal body between the anal canal and the posterior wall of the vagina (arrows), which is outlined by the rim of a fluid-filled condom covering the transducer.
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Figures 11-14. (11) Scar tissue in the rectovaginal septum in a young woman with fecal incontinence following traumatic obstetric delivery. Transvaginal US image shows a defect in the hypoechoic black ring of the internal anal sphincter anteriorly from the 10-o'clock to the 12-o'clock position. A large mass of scar tissue (S) is seen expanding the rectovaginal septum and increasing the distance from the anal canal to the vaginal probe. (12) Tear of the anal sphincter in a 40-year-old woman with fecal incontinence following a fourth-degree tear at obstetric delivery. Transvaginal US image shows a deficiency in the hypoechoic black ring of the internal anal sphincter anteriorly at the 12-o'clock position. The tear in the external anal sphincter appears as a hypoechoic wedge in the normal echogenic muscle (arrows). (13) Permission to reprint this figure electronically was denied by the publisher. See print version. (14) Tear of the internal and external anal sphincters with loss of the perineal body. Transvaginal US image shows a large defect in the internal anal sphincter anteriorly between the 9-o'clock and 2-o'clock positions. The external anal sphincter is extremely thin anteriorly. There is virtually no rectovaginal septum or perineal body between the anal canal and the posterior wall of the vagina (arrows), which is outlined by the rim of a fluid-filled condom covering the transducer.
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Figures 11-14. (11) Scar tissue in the rectovaginal septum in a young woman with fecal incontinence following traumatic obstetric delivery. Transvaginal US image shows a defect in the hypoechoic black ring of the internal anal sphincter anteriorly from the 10-o'clock to the 12-o'clock position. A large mass of scar tissue (S) is seen expanding the rectovaginal septum and increasing the distance from the anal canal to the vaginal probe. (12) Tear of the anal sphincter in a 40-year-old woman with fecal incontinence following a fourth-degree tear at obstetric delivery. Transvaginal US image shows a deficiency in the hypoechoic black ring of the internal anal sphincter anteriorly at the 12-o'clock position. The tear in the external anal sphincter appears as a hypoechoic wedge in the normal echogenic muscle (arrows). (13) Permission to reprint this figure electronically was denied by the publisher. See print version. (14) Tear of the internal and external anal sphincters with loss of the perineal body. Transvaginal US image shows a large defect in the internal anal sphincter anteriorly between the 9-o'clock and 2-o'clock positions. The external anal sphincter is extremely thin anteriorly. There is virtually no rectovaginal septum or perineal body between the anal canal and the posterior wall of the vagina (arrows), which is outlined by the rim of a fluid-filled condom covering the transducer.
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Figures 11-14. (11) Scar tissue in the rectovaginal septum in a young woman with fecal incontinence following traumatic obstetric delivery. Transvaginal US image shows a defect in the hypoechoic black ring of the internal anal sphincter anteriorly from the 10-o'clock to the 12-o'clock position. A large mass of scar tissue (S) is seen expanding the rectovaginal septum and increasing the distance from the anal canal to the vaginal probe. (12) Tear of the anal sphincter in a 40-year-old woman with fecal incontinence following a fourth-degree tear at obstetric delivery. Transvaginal US image shows a deficiency in the hypoechoic black ring of the internal anal sphincter anteriorly at the 12-o'clock position. The tear in the external anal sphincter appears as a hypoechoic wedge in the normal echogenic muscle (arrows). (13) Permission to reprint this figure electronically was denied by the publisher. See print version. (14) Tear of the internal and external anal sphincters with loss of the perineal body. Transvaginal US image shows a large defect in the internal anal sphincter anteriorly between the 9-o'clock and 2-o'clock positions. The external anal sphincter is extremely thin anteriorly. There is virtually no rectovaginal septum or perineal body between the anal canal and the posterior wall of the vagina (arrows), which is outlined by the rim of a fluid-filled condom covering the transducer.
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URINARY TRACT APPLICATIONS
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Ureteric Calculi
US has proved to be highly sensitive in the detection of renal calculi (38,39); however, opinions vary with regard to the optimal method for detection of ureterolithiasis (40). Some clinicians favor intravenous urography, whereas others advocate the use of US in conjunction with kidney-ureter-bladder radiography (41). None of these techniques is 100% sensitive. Because detection of ureteric stones can be difficult at US, indirect criteria are often used to support a clinical impression of passage of a urinary calculus. These include unilateral pelvicaliectasis corresponding to the side of pain, an abnormally elevated resistive index in the affected kidney, and unilateral absent ureteric jet on the affected side (42,43).
The ureterovesical junction is the most common site for a passing urinary calculus to lodge. At transabdominal US, experience and knowledge of the exact location and orientation of the intramural ureter allows detection of many stones at this site. However, overdistention of the bladder may cause caudal displacement of the trigone, making it difficult to visualize a calculus. In some patients, underdistention of the bladder may make it difficult to see anything. This is particularly true in large or pregnant patients and in patients in whom urinary frequency is related to the irritation associated with passage of a urinary stone. In such cases, transvaginal US may be optimal in the detection of distal ureteric calculi (44). The procedure is easy to perform and is well tolerated by most patients. Furthermore, it can be performed in patients for whom intravenous pyelography and radiography are contraindicated due to renal insufficiency, sensitivity to iodinated contrast material, or pregnancy.
Optimal transvaginal technique in searching for ureteric stones includes retention of a small amount of urine in the patient's bladder, although high-quality images can still be obtained if the bladder is empty. The intramural and distal ureter is generally located slightly anterior and lateral to the vaginal vault.
If the ureter is dilated, it can easily be seen as an elongated tubular structure entering the bladder obliquely. A distal ureteric calculus manifests as an echogenic focus, usually with sharp acoustic shadowing (Fig 15). There may be thickening or irregularity of the distal ureter and bladder at the ureterovesical junction due to edema caused by stone irritation (Fig 15).
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Figure 15a. Ureteric calculus with edema. (a) Transvaginal US image shows a dilated ureter (U) and the edge of an obstructing stone. B = bladder. (b) US image obtained perpendicular to a shows the stone (calipers) with sharp acoustic shadowing and surrounding soft-tissue edema.
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Figure 15b. Ureteric calculus with edema. (a) Transvaginal US image shows a dilated ureter (U) and the edge of an obstructing stone. B = bladder. (b) US image obtained perpendicular to a shows the stone (calipers) with sharp acoustic shadowing and surrounding soft-tissue edema.
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The interpretation of images that show a stone but no dilated ureter or urine-filled bladder may be difficult because the only US finding may be the shadowing echogenic focus representing the calculus. Again, knowledge of the expected location of the ureterovesical junction is critical for correct interpretation.
Bladder Abnormalities
Cystoscopy is routinely performed in patients with unexplained hematuria. In young women, however, hematuria is most often benign and associated with urinary tract infection. We believe that US of the kidneys and bladder is an excellent screening modality in this patient population for detection of more significant disease. Stones, infections, and tumors of the bladder are the abnormalities most likely to be detected at both routine and transvaginal pelvic US. The transvaginal approach is particularly helpful in patients with poor bladder filling or with bladder diverticula, which are blind areas at cystoscopy (Fig 16).
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Figure 16a. Transitional cell carcinoma of the bladder with a diverticulum. (a) Suprapubic US image shows a poorly filled bladder (b) with a left lateral diverticulum (d). (b) Transvaginal US image shows a carpet of tiny polyps arising from the wall of the bladder (b). Low-level echoes are seen within the diverticulum (d). (c) Transvaginal US image demonstrates tiny polyps on the wall of the diverticulum (arrows); these proved to be transitional cell carcinoma at histologic analysis.
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Figure 16b. Transitional cell carcinoma of the bladder with a diverticulum. (a) Suprapubic US image shows a poorly filled bladder (b) with a left lateral diverticulum (d). (b) Transvaginal US image shows a carpet of tiny polyps arising from the wall of the bladder (b). Low-level echoes are seen within the diverticulum (d). (c) Transvaginal US image demonstrates tiny polyps on the wall of the diverticulum (arrows); these proved to be transitional cell carcinoma at histologic analysis.
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Figure 16c. Transitional cell carcinoma of the bladder with a diverticulum. (a) Suprapubic US image shows a poorly filled bladder (b) with a left lateral diverticulum (d). (b) Transvaginal US image shows a carpet of tiny polyps arising from the wall of the bladder (b). Low-level echoes are seen within the diverticulum (d). (c) Transvaginal US image demonstrates tiny polyps on the wall of the diverticulum (arrows); these proved to be transitional cell carcinoma at histologic analysis.
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Optimal transvaginal technique for bladder assessment includes retention of a small to moderate amount of urine in the patient's bladder. Anterior orientation of the probe and partial withdrawal of the probe from the vagina to evaluate the bladder base and urethra are recommended.
Inflammatory and neoplastic masses as well as miscellaneous masses may be seen (45). Transitional cell carcinoma is a solid mass that may demonstrate superficial calcification (Figs 16, 17). Bladder wall invasion and extension to the perivesical soft tissues (Fig 17) may be seen in transitional cell carcinoma and other adjacent tumors, especially cervical cancer (46). Pheochromocytoma is a tumor that is rarely seen in the bladder; when present, however, it manifests as a solid mass with normal and intact overlying mucosa (Fig 18). Inflammatory masses may be associated with generalized pelvic inflammatory disease or may reflect localized bladder inflammation. In contrast to neoplastic bladder processes, inflammation causes edema with thickening of the tissue planes and, often, localized intramural fluid pockets. Endometriomas may manifest as complex bladder wall masses (47,48) that are not as uniformly solid as transitional cell tumors and do not demonstrate superficial calcification (Fig 19). Affected patients are invariably young women with hematuria accompanying the menses.
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Figure 17a. Transitional cell carcinoma of the bladder. (a) Transvaginal US image shows a partially filled bladder. A large tumor is seen projecting into the lumen. There is obvious extension of the tumor beyond the bladder wall (arrows). (b) CT scan helps confirm the tumor and the transmural spread.
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Figure 17b. Transitional cell carcinoma of the bladder. (a) Transvaginal US image shows a partially filled bladder. A large tumor is seen projecting into the lumen. There is obvious extension of the tumor beyond the bladder wall (arrows). (b) CT scan helps confirm the tumor and the transmural spread.
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Figure 18a. Unsuspected pheochromocytoma of the bladder wall in a woman with cardiac palpitations and a full urinary bladder. (a) Transvaginal US image obtained with the bladder moderately full shows a solid mass projecting from the bladder wall into the lumen. (b) Repeat US image obtained with the bladder virtually empty shows the mass as intramural with an intact overlying mucosa.
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Figure 18b. Unsuspected pheochromocytoma of the bladder wall in a woman with cardiac palpitations and a full urinary bladder. (a) Transvaginal US image obtained with the bladder moderately full shows a solid mass projecting from the bladder wall into the lumen. (b) Repeat US image obtained with the bladder virtually empty shows the mass as intramural with an intact overlying mucosa.
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Figure 19a. Endometrioma of the bladder in a 28-year-old woman with hematuria accompanying the menses. (a) Sagittal suprapubic US image of the bladder shows a mass (calipers) arising from the posterior wall of the bladder. (b) Transvaginal US image of a partially full bladder shows features of a solid intramural mass (m) with multiple superficial cysts.
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Figure 19b. Endometrioma of the bladder in a 28-year-old woman with hematuria accompanying the menses. (a) Sagittal suprapubic US image of the bladder shows a mass (calipers) arising from the posterior wall of the bladder. (b) Transvaginal US image of a partially full bladder shows features of a solid intramural mass (m) with multiple superficial cysts.
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Urethral Abnormalities
At US, the normal urethra appears as an elongated, hypoechoic tract that is more pronounced at transvaginal or transperineal imaging; therefore, its appearance may be misinterpreted. Calculi, tumors, and diverticula in this location can be evaluated with transvaginal US.
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PERITONEAL APPLICATIONS
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The pouch of Douglas is the most dependent portion of the peritoneal cavity and as such often demonstrates abnormality in diffuse peritoneal disease. Although suprapubic US may demonstrate evidence of either masses or fluid in this area, transvaginal imaging is superior in the characterization of both entities. Furthermore, even minute quantities of peritoneal fluid may be identified in this location with transvaginal imaging.
Meticulous technique is of great importance in imaging the pouch of Douglas. To ensure evaluation of the entire pouch, the transducer should be angled from anterior to posterior by elevating and depressing the examining hand. The lateral margins of the pouch should be examined by angling the transducer toward both pelvic side walls. The latter are optimally assessed in the transverse plane.
Fluid Collections
Characterization of free fluid in the pouch of Douglas in conjunction with clinical findings often allows correct diagnosis of the underlying process. Small amounts of clear fluid are believed to be a normal finding at pelvic US in premenopausal women. Increasing amounts of fluid and the presence of particles, strands, and air are suggestive of complications. Blood, pus, inflammatory exudate, crystalline particles, and neoplastic cells may all produce particulate ascites. Inflammatory cells or neoplasia that are suspected at pelvic US may be confirmed with aspiration of fluid via either the transvaginal or suprapubic route.
Use of high-frequency transducer crystals and increased gain settings can help identify particles within ascitic fluid. Therefore, technical considerations for transvaginal study of the peritoneum should include selection of the highest-frequency transducer available and use of a gain setting higher than that which provides optimal gray-scale imaging.
Blood.—Gynecologic US practitioners are familiar with the appearance of blood in the peritoneal cavity (most commonly associated with rupture that occurs during an ectopic pregnancy) at transvaginal US. Particulate ascites in a patient with suspected ectopic pregnancy has a strong association with this condition (49). Similarly, blood in the peritoneal cavity, whether of gynecologic or nongynecologic origin, will often demonstrate particulate material in the dependent pelvic pouch. In addition to particulate ascites, blood clots also collect in the dependent pouch, where they appear as solid or complex masses, often with mixed echogenicity. Spontaneous organ rupture, recent surgery or trauma, and malignant ascites should all be considered as potential causes of hemoperitoneum.
Inflammatory Exudate.—Particulate ascites in association with pelvic inflammatory disease is usually easily recognized as part of the local inflammatory process. In contrast, diffuse peritoneal inflammation may be more difficult to recognize, especially if clinical findings are not considered. Frank purulent peritonitis is usually associated with known or suspected disease of the gastrointestinal tract (Fig 20). H
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Abstract
INTRODUCTION
