Perforation of rectal diverticulum with amyloidosis secondary to rheumatoid arthritis: case report and review of the literature.

We report a case of perforation of a rectal diverticulum with amyloidosis secondary to rheumatoid arthritis (RA), and review the clinicopathologic features in 21 Japanese amyloidosis patients with colorectal perforation. A 62-year-old woman with amyloidosis secondary to RA suddenly complained of abdominal pain. Computed tomography (CT) showed ascites and free air in the abdominal cavity, and many diverticula with calculi in the sigmoid colon. Emergent surgery was performed for acute peritonitis. We observed the perforation, 5 mm in diameter, of a diverticulum in the upper rectum, and many diverticula located in the upper rectum and sigmoid colon. Anterior resection of the rectum combined with sigmoidectomy was performed. The resected specimen showed many diverticula including fecaliths, approximately 7 mm in size. Histopathologically, many inflammatory cells had infiltrated around the perforation. On Congo red staining, amyloid deposits were observed in or around the small blood vessels of the lamina propria mucosa and submucosa of the rectum. Although colorectal perforation with amyloidosis secondary to RA is rare, this complication was associated with poor prognosis. Furthermore, in patients with amyloidosis, we should be careful regarding the management of colorectal diverticula.