Chronic diverticular disease is sometimes associated with patchy mucosal hemorrhage, congestion, and granularity in the sigmoid colon. An inflammatory infiltrate may be found on microscopic examination. These changes mimic Crohn's colitis, ulcerative colitis, or ischemic colitis. However, so-called diverticular colitis is limited to areas of diverticulosis. The objectives of diagnostic tests in suspected acute diverticulitis are to confirm the diagnosis of diverticulitis, to exclude other important conditions, to determine whether complications have occurred, and to plan treatment.
Leukocytosis is usually present in acute diverticulitis.
The urine may contain a modest number of white cells or red blood cells. A urinary tract infection, particularly a polymicrobial infection, should suggest the possibility of a colovesical fistula. Plain abdominal x-rays are most useful in excluding other abdominal conditions, such as intestinal obstruction. Occasionally, an inflammatory mass with gas may be noted, confirming the presence of an abscess. Free intra-abdominal air is unusual in acute diverticulitis.