IS Case 149: Case 1: Fecal Impaction; Case 2: Fecal Impaction with stercoral colitis
Imaging Sciences URMC 2008
Publication Date: 2009-05-21
Case 1 is a 90-year-old female, with multiple medical problems including chronic constipation, who presented with abdominal pain and recent development of diarrhea. Case 2 is a 54-year-old female, with developmental disability and epilepsy, who presented with dyspnea and change in mental status.
Fecal impaction is essentially a solid, immobile bulk of stool that cannot be passed. Fecal impaction leading to colonic obstruction is seen primarily in patients with chronic constipation, particularly the elderly and young patients who are neurologically impaired. There is also an association with opiates, tricyclic antidepressants and tranquilizers, which slow bowel transit time. As in our first case, diarrhea may occasionally occur paradoxically as a result of fecal impaction with the overflow of liquid colonic contents around the impacted stool .
Complications include the development of stercoral colitis. Stercoral colitis is an inflammatory colitis related to increased intraluminal pressure from impacted fecal material in the colon. If the fecal impaction is not promptly relieved, the condition can lead to colonic ulceration, necrosis, perforation, peritonitis and patient demise.
Radiographs may demonstrate signs of distal colonic obstruction and paucity of gas in the rectum, or a fecolith in the rectum. The dilated, air-filled sigmoid colon seen Case 1 is typical for distal obstruction in the setting of chronic constipation. Small bowel dilatation may also be seen .
The CT diagnosis of fecal impaction is usually straightforward. On CT, it is important to evaluate for findings of stercoral colitis. In uncomplicated fecal impaction, the colon is distended and the wall is thin (Case 1). Focal thickening or pericolonic fat stranding in a segment of colon that contains fecal impaction suggests ischemia or ulceration (Case 2) . The presence of extraluminal gas or an abscess suggests that perforation has already occurred.
Non-invasive treatments are similar to those for constipation and include increased intake of fluids and dietary fiber, and physical exercise. However, once fecal impaction occurs, these methods are usually not successful. The mainstay of treatment are enemas to soften the impaction and manual disimpaction. Use of laxatives may be dangerous because of the risk of stercoral perforation. Surgery may be necessary if the bowel becomes totally obstructed.
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