Lupus peritonitis mimicking acute surgical abdomen in a patient with systemic lupus erythematosus: report of a case.

A 25-year-old Japanese woman who had been suffering from systemic lupus erythematosus (SLE) for 12 years was admitted to our hospital with a suspected diagnosis of peritonitis after suddenly developing severe abdominal pain and distention which could not be relieved by treatment with anodyne. Noninvasive examinations did not provide enough evidence to rule out acute appendicitis, bowel perforation, or ischemia due to vasculitis. Therefore, in consideration of the severity of her uncontrollable abdominal pain, an exploratory laparotomy was performed. The operative findings revealed nonbacterial peritonitis with a large amount of ascites and an edematous small bowel. No perforation of the intestine was found. On post-operative day (POD) 3, the severe abdominal pain redeveloped, but responded well to steroid pulse therapy. Based on the operative findings and her clinical course, the most likely diagnosis was thought to be acute lupus peritonitis. It is often difficult to ascertain whether abdominal pain in an SLE patients is due to lupus peritonitis or to an underlying cause requiring surgery. Thus, it is essential that continuous and careful assessment of the surgical abdomen is performed when a patient with SLE develops acute abdominal pain, and if a surgical condition cannot be ruled out, a laparotomy should be performed without delay.