The small bowel faeces sign can be observed on abdominal CT scans. The sign has been described as a finding indicative of small bowel obstruction or another severe small bowel abnormality (e.g. metabolic or infectious disease). While the reported prevalence of the sign in small bowel obstruction is low (7-8%) 1, the combination of small bowel faeces sign and moderate to severe bowel obstruction is fairly suggestive of obstruction, particularly when associated with distal bowel collapse 7.
Defined by the presence of particulate feculent material mingled with gas bubbles in the lumen of the small intestine (resembling colonic content on CT), it is believed to be the result of delayed intestinal transit caused by incompletely digested food, bacterial overgrowth, or increased water absorption of the distal small-bowel contents due to obstruction 1.
The small bowel faeces sign is most often present in distal small intestine loops, for a length of between 4 and 200 cm.
The small-bowel faeces sign has shown a high specificity for subacute or low-grade small bowel obstruction because, in a progressively developing obstruction with slowed intestinal transit, there is enough time for increased water absorption to subsequently form the faeces-like intestinal content. 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 6.
- non-obstructive causes of abdominal pain 7
- small bowel obstruction caused by a phytobezoar, usually necessitating surgery 4-5
Detection of the small bowel faeces sign should prompt you to:
- look for possible bowel dilatation and/or distal collapse 6-7
- distinguish it from phytobezoar (rare), using lung windows and length measurements. Features favouring a phytobezoar include 4-5:
- higher grade of obstruction
- absence of hazy mesentery and interloop ascites
- length below ~10 cm
- mean attenuation below ~-12 HU
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- 3. Lazarus DE, Slywotsky C, Bennett GL et-al. Frequency and relevance of the "small-bowel feces" sign on CT in patients with small-bowel obstruction. AJR Am J Roentgenol. 2004;183 (5): 1361-6. AJR Am J Roentgenol (full text) - Pubmed citation
- 4. Delabrousse E, Lubrano J, Sailley N et-al. Small-bowel bezoar versus small-bowel feces: CT evaluation. AJR Am J Roentgenol. 2008;191 (5): 1465-8. doi:10.2214/AJR.07.4004 - Pubmed citation
- 5. Chen YC, Liu CH, Hsu HH et-al. Imaging differentiation of phytobezoar and small-bowel faeces: CT characteristics with quantitative analysis in patients with small- bowel obstruction. Eur Radiol. . doi:10.1007/s00330-014-3486-1 - Pubmed citation
- 6. Santillan CS. Computed tomography of small bowel obstruction. Radiol. Clin. North Am. 2013;51 (1): 17-27. doi:10.1016/j.rcl.2012.09.002 - Pubmed citation
- 7. Jacobs SL, Rozenblit A, Ricci Z et-al. Small bowel faeces sign in patients without small bowel obstruction. Clin Radiol. 2007;62 (4): 353-7. doi:10.1016/j.crad.2006.11.007 - Pubmed citation