DOI: 10.1148/radiol.2252010976
The Small-Bowel Feces Sign1
Michael H. Fuchsjäger, MD
1 From the Department of Radiology, University of Vienna, Währinger Gürtel 18-20, A-1090 Vienna, Austria. Received May 29, 2001; revision requested July 10; revision received August 16; accepted September 7. Address correspondence to the author (e-mail: michael.fuchsjaeger@univie.ac.at).
Index terms: Intestines, CT, 74.723 • Intestines, stenosis or obstruction, 74.723 • Signs in Imaging
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APPEARANCE
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The small-bowel feces sign is a finding that can be observed on computed tomographic (CT) scans of the abdomen (1,2). It is defined by the presence of particulate (colonlike) feculent matter mingled with gas bubbles in the lumen of dilated loops of the small intestine (Fig 1).
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Figure 1. The small-bowel feces sign in a 55-year-old man with surgically verified small-bowel obstruction (SBO) due to adhesions (arrowhead). Transverse CT scan shows the typical appearance, with feceslike material in a prestenotic dilated small-bowel loop (arrow). At surgery, bandlike adhesions were found.
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EXPLANATION
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The particulate feculent material mingled with gas bubbles seen in the small-bowel feces sign resembles the appearance of stool in the colon on CT scans. It is the result of delayed intestinal transit and is believed to be caused by incompletely digested food, bacterial overgrowth, or increased water absorption of the distal small-bowel contents due to obstruction (1,2).
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DISCUSSION
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The small-bowel feces sign has been described as a finding indicative of SBO or another severe small-bowel abnormality (ie, metabolic or infectious disease) (1–3). Bowel obstruction accounts for approximately 20% of acute abdominal surgical interventions (4). In 60%–80% of cases of intestinal obstruction, the small bowel is involved (5). SBO occurs whenever intrinsic or extrinsic blocking of the normal flow of small-bowel contents is present.
SBO is associated with clinical signs of abdominal tenderness, distention, and increased high-pitched bowel sounds. However, in complete obstruction with predominantly fluid-filled bowel loops, there may be less distention and diminished sounds. Similar clinical presentations can be found in cases of paralytic ileus, intraabdominal abscess, malignant tumor, pancreatitis, peptic ulcer disease, or gastroenteritis (6). Thus, an early and accurate radiologic diagnosis of SBO is of major clinical importance (7).
SBO is often difficult to diagnose on the basis of conventional radiographic findings alone (8). Additional radiologic examinations are required (6). CT scans of the abdomen can show obstruction with a sensitivity of up to 100% and provide information about the specific cause and location of the obstruction, as well, which may influence the surgical approach (7). At CT, the presence of proximal small-bowel dilatation and the identification of a transition point and collapsed distal small bowel are indicative of acute high-grade SBO, which will lead to immediate surgical intervention (6,8).
In a more subacute clinical course without this specific CT sign, assigning an accurate diagnosis can be challenging. The CT diagnosis of low-grade or nonadhesive SBO is of higher clinical relevance than the confirmation of an obvious high-grade SBO (9).
The small-bowel feces sign is most often present in distal small intestine loops, seen at a length of 4–200 cm (1). The reported prevalence of the sign in SBO is low (7%–8%) (2).
The small-bowel feces sign has shown a high specificity for subacute or low-grade SBO, because in a progressively developing obstruction with slowed intestinal transit, there is enough time for increased water absorption to subsequently form the feceslike intestinal content (1,10). Recognition is important to prevent a delay in medical intervention. Since the sign is usually seen immediately proximal to the level of obstruction, it may be helpful in recognition of the exact site and cause.
The primary source of this sign is classic mechanical SBO due to adhesions (Fig 1), hernias, or tumors. Other causes are inflammatory stenoses (Fig 2) and infectious, metabolic, or ischemic disorders.
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Figure 2a. The small-bowel feces sign in a 20-year-old man with a history of Crohn disease who presented with acute abdominal pain. (a) Transverse CT scan demonstrates a stenotic segment of inflammatory bowel wall thickening (arrowheads) of the distal ileum. (b) Transverse CT scan shows a dilated loop of the small bowel (arrow) with feceslike material more proximal to the stenosis.
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Figure 2b. The small-bowel feces sign in a 20-year-old man with a history of Crohn disease who presented with acute abdominal pain. (a) Transverse CT scan demonstrates a stenotic segment of inflammatory bowel wall thickening (arrowheads) of the distal ileum. (b) Transverse CT scan shows a dilated loop of the small bowel (arrow) with feceslike material more proximal to the stenosis.
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Inhomogenous mottled material with small internal air collections in the small intestine may also be found in other conditions, such as cystic fibrosis, infectious or metabolic bowel disease, rapid jejunostomy tube feedings, or, rarely, bezoars (1,11,12). By definition, however, for the diagnosis of the small-bowel feces sign, a dilatation of bowel loops more than 2.5 cm in diameter must be present. Rarely, feculent material can be seen as a normal finding on CT scans in nondilated distal ileal loops, which presumably occurs as a result of reflux of fecal matter from the cecum into the terminal ileum (1).
The small-bowel feces sign is a useful adjunct to other more traditional signs of small-bowel obstruction, particularly in patients with low-grade or intermittent obstruction. Most patients demonstrating this radiologic feature require hospitalization and, frequently, surgical intervention (1,10). Knowledge of this sign is important for the radiologist, as it is helpful in the diagnosis of small-bowel obstruction.
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ACKNOWLEDGMENTS
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I thank Wolfgang Schima, MD, for assistance in preparing the manuscript.
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FOOTNOTES
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A trainee (resident or fellow) wishing to submit a manuscript for Signs in Imaging should first write to the Editor for approval of the sign to be prepared, to avoid duplicate preparation of the same sign.
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REFERENCES
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D. E. Lazarus, C. Slywotsky, G. L. Bennett, A. J. Megibow, and M. Macari
Frequency and Relevance of the "Small-Bowel Feces" Sign on CT in Patients with Small-Bowel Obstruction
Am. J. Roentgenol.,
November 1, 2004;
183(5):
1361 - 1366.
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