Closed loop small bowel obstruction - internal hernia

Case contributed by Michael P Hartung
Diagnosis certain


Acute abdominal pain.

Patient Data

Age: 60 years
Gender: Male

Several loops of severely-abnormally appearing small bowel in the lower mid abdomen, with classic features of closed-loop obstruction. There is diminished wall enhancement, interloop fluid, and mesenteric edema. The mesenteric vessels have a "C" shaped with radial distribution of vessels towards the point of obstruction. On the sagittal images, they appear clustered. On the coronal "key image" in the midline at the level of the iliac bones, there is a faecalized, mildly dilated loop of small bowel which abruptly narrows as it enters this abnormal collection of small bowel, and there is also an adjacent normal-appearing segment of small bowel leaving the collection. 

Apparent laminar filling defect in the ileocolic vein, likely to represent flow artifact, rather than thrombosis.

OPERATIVE REPORT (edited excerpt):

POSTOPERATIVE DIAGNOSIS: Closed loop small bowel obstruction, ischemic bowel mid-ileum approximately 30 cm. The bowel untwisted from an omental adhesion, peristalsing viable bowel, violaceous in nature with minimal mesenteric edema, palpable pulses and Doppler signals.

Description: The violaceous 30-cm loop of mid-ileum greeted us upon entrance to the abdominal cavity. This de-torsed spontaneously and promptly. The bowel appeared violaceous, however, it was viable. After wrapping the bowel with warm, moist lap sponges, after a period of 10-15 minutes the bowel color improved. Peristalsis was observed. No areas of necrosis were seen. Palpable pulses in the mesentery were observed and palpated. To ensure good blood flow, Doppler signals throughout the loop inside the antimesenteric side were appreciated throughout the mesentery of the concerning area. No excessive wall thickening or edema was appreciated. Several small omental defects were seen. Electrocautery was used to open these defects as this was a concern for the suspected cause of an etiology of the closed loop obstruction. Omentum was seen attached to the sigmoid colon in an abnormal position. This was divided in an avascular plane with electrocautery with care to not injure the bowel with electrocautery. Hemostasis was noted. The bowel was run from the ligament of Treitz to the ileocecal junction. All the other bowel was viable and within normal appearance...


Case Discussion

The cluster of ischemic small bowel in the mid-lower abdomen is striking: hypo-enhancing, mesenteric edema, and fluid. That alone should raise the concern of ischemic small bowel, either due to embolic event or closed loop obstruction. The abnormal bowel has a C-shaped configuration with radial distribution of the vessels toward to the point of obstruction. 

At this point, you have to start running the proximal small bowel to figure it out: the proximal bowel appears normal, and transitions into a segment of faecalized small bowel, which abruptly tapers as it transitions into the abnormal bowel, the so-called "beak sign". Faecalization is a sign of slow transit and lower-grade obstruction and can be helpful to direct you toward the transition point. Immediately adjacent is a loop of normal caliber bowel leaving the collection, which can be best appreciated on the coronal reformats. This indicates that the bowel is obstructed at two points at the same location: as it enters and as it exits the hernia orifice. Thus, it is a closed loop obstruction due to an internal hernia. Multiple omental defects were seen at the time of surgery, which was felt to be the case of obstruction, confirming the imaging diagnosis. 


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