The diagnosis of ulcerative colitis may be considered with a history of abdominal cramps, diarrhea, and mucoid stools. Laboratory findings are nonspecific, and may include leukocytosis, anemia, thrombocytosis, decreased serum albumin levels, abnormal liver function test results, and negative stool studies for ova, parasites, and enteric pathogens. Abdominal CT scanning is important for the diagnosis of nonspecific abdominal pain or for suspected colitis. Colonoscopy can confirm the diagnosis and define the extent of colonic involvement. The differential diagnosis includes infectious, ischemic, radiation, antineoplastic agent induced, pseudomembranous, and Crohn colitis. When the disease is limited to the rectum, consider sexually acquired diseases, such as rectal syphilis, gonococcal proctitis, lymphogranuloma venereum, and inflammation caused by herpes simplex virus, Entamoeba histolytica, Shigella, and Campylobacter.