Case  dd -  Mesenteric tear and necrotic bowel

There is a small amount of hemoperitoneum around the liver, spleen, in the right paracolic gutter, and in the pelvis.  There is a focal collection of fluid in the root of the mesentery, seen inferior to the duodenum.  A single loop of small bowel in the right abdomen is distended and air filled.  While the mucosa of this loop is not thickened, it enhances less than the mucosa in other portions of the bowel (1, 2).  If you follow this loop down and to the left on the cine images you can see it transition from normally enhancing bowel to underperfused bowel.  There are surrounding wedge shaped regions of peritoneal fluid.  Lastly, there is fecalization of this loop inferiorly.

This constellation of findings indicates bowel injury.  Bowel necrosis secondary to a mesenteric tear was found at surgery.

Fluid and stranding localized to the mesentery should raise suspicion for bowel or mesenteric injury.  The findings of bowel ishemia and necrosis are generally nonspecific, but are more specific in the setting of trauma.  These findings include

• underperfusion of a focal segment of bowel
• stranding surrounding a focal loop of bowel
• wedged shaped fluid collections in the mesentery which interdigitate between loops of bowel.
• focal bowel wall thickening
• pneumatosis
• portal venous air

It is unlikely a MVC victim also has acute gastroenteritis or Crohns disease.

In a previous case focal mesenteric hematoma was presented as a sign of mesenteric injury.  This case shows the more direct signs of bowel injury.  The bowel is ischemic secondary to a mesenteric tear which is not, itself, identified. However, the other findings of bowel injury are well demonstrated.  Notice how the peritoneal fluid is localized to the mesentery (1, 2).  It takes a wedged or triangular appearance where it interdigitates between loops of ischemic bowel.  This is a good finding for ischemia, especially if the adjacent loops are abnormal.  

The affected loops of bowel also enhance to a lesser degree than the nonaffected loops (1, 2).  The appearance is partly secondary to distension, which thins the mucosa and makes the enhancement more diffiuclt to see.  However, I think these loops really do enhance less.  Lastly, fecalization is seen inferiorly.  Fecalization of the small bowel refers to a pattern of intraluminal air with the appearance of stool.  This is seen in small bowel obstruction and ischemia and is not a specific finding.  However, in the appropriate clinical setting, i.e. trauma, it should suggest the diagnosis of post traumatic ischemia. 

Did you notice the right adnexal cyst.  In a premenopausal woman, this subcentimeter, simple appearing cyst represents normal follicular activity.

Take home points:

• Post traumatic signs of bowel injury or ischemia include:
  • extravasation of enteric contrast
  • pneumoperitoneum
  • focal mesenteric hematoma
  • underperfusion of a focal segment of bowel
  • stranding surrounding as focal loop of bowel
  • wedged shaped fluid collections in the mesentery which interdigitate between loops of bowel.
• Focal mesenteric hematoma suggests a mesenteric tear which can lead to bowel ischemia.  The direct signs of ischemia may not be seen acutely. In this case they are present.  In a previous case they were not.
• Findings on CT suspicious for bowel injury are indication for surgical exploration, even in the absence of arterial hemorrhage or bowel wall thickening.