Clinical Quiz

A 9-year-old boy, known to have Crohn disease, presented to the emergency room with a one-week history of increasing, colicky abdominal pain. He was diagnosed at four years of age with severe perianal and rectal disease. His disease was refractory to extensive medical management, and he required a diversion sigmoid colostomy and the establishment of a Hartmann pouch at seven years of age because of persistent anal stenosis and severe dyschezia. In addition to his abdominal pain, he reported the passage of flatus, but no stool, into his colostomy bag. His vital signs were stable; he was apyrexial and had a normal urine analysis. On examination, his abdomen was protuberant with a 15 by 12 cm mass in the hypogastric region extending down into the pelvis. The colostomy site in the left flank appeared healthy. Anal inspection revealed extensive scarring, and no anal orifice was readily identified. Imaging included an abdominal radiograph (Fig. 1), abdominal and pelvic sonography (Fig. 2), and retrograde colon study via his colostomy.FIG. 1. No Caption AvailableFIG. 2. No Caption AvailableWhat is the most likely diagnosis? A. Colostomy stenosis and obstruction B. Pelvic abscess C. Rectal mucocele D. Distended bladder due to outlet obstruction Answer: C. Rectal Mucocele The mucosal lining of a Hartmann's pouch secretes mucus, which must drain or it will accumulate over time. Inflammation, scarring and epithelialization of the anal canal obstructed the drainage in this case, causing a mucocele, which progressively enlarged. The abdominal radiograph indicated a soft-tissue mass arising from the pelvis, displacing bowel superiorly and to the right. Sonography demonstrated a markedly dilated hollow viscus arising from the deep pelvis and extending up to the left hypochondrium. There was no obvious connection to the stoma site. The mass was causing mild, left-sided hydronephrosis. Retrograde enema via the colostomy filled a normal caliber colon. The anus was probed open under general anesthesia and 1100 ml of mucus was evacuated. A Penrose drain was left across the anus to maintain patency. Comment: Mucoceles are commonly associated with the appendix and cranial sinuses. Rectal mucoceles are rare. The first reported pediatric case was an extraluminal pelvic mucocele in a patient with an imperforate anus following an endorectal pull-through operation with incomplete mucosal excision (1). There are case reports of rectal mucoceles following Hartmann's procedure for ulcerative colitis, and secondary to high anal sphincter tone following spinal trauma (2,3). Mucoceles have developed in defunctioned colon after pull-through surgery due to stenosis and retraction of the colonic stump (4,5). Scarring of the mucus fistula, or failure to creat a mucus fistula are other described contributing factors. In our patient, obstruction of the isolated distal colon was caused by severe, long-standing anorectal Crohn disease which caused scarring, stricture and epithelialization of the anal orifice. Treatment requires effective drainage or removal of the mucus-producing epithelium. This case illustrates a rare but interesting complication of Crohn disease.

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