Diverticulitis Workup

Updated: Aug 06, 2019
  • Author: Elie M Ghoulam, MD, MS; Chief Editor: BS Anand, MD  more...
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Laboratory Studies

The diagnosis of acute diverticulitis can usually be made on the basis of the history and physical examination. Laboratory tests may be helpful when the diagnosis is in question.

A hemogram may reveal leukocytosis and a left shift, indicating infection. However, the absence of leukocytosis does not rule out diverticulitis, as 20%-40% of patients have a normal white blood cell count. This is particularly true in patients who are immunocompromised, who are elderly, and who have less severe disease. A hemoglobin level is important when the patient reports hematochezia.

Measurement of blood chemistries may be helpful in the patient who is vomiting or has diarrhea to assess electrolyte abnormalities. Assess renal function prior to the administration of most intravenous contrast material.

Liver function tests and lipase levels may help to exclude other causes of abdominal pain.

If a colovesical fistula is suspected, a urinalysis may reveal red or white blood cells. However, inflammation and infection due to diverticulitis adjacent to the ureters or the bladder may be the source of these cells. A urine culture may confirm sterile pyuria due to inflammation versus polymicrobial infection in the case of a fistula.

Blood cultures should be obtained prior to the administration of empiric parenteral antimicrobial therapy in patients who are severely ill or in those with complicated disease.

A pregnancy test must be performed in any female of childbearing age who presents with abdominal pain to rule out ectopic pregnancy, as well as prior to radiologic studies and before administering certain antibiotics to protect a viable fetus.


Imaging Studies

Although the diagnosis of diverticulitis can be made on clinical grounds, a computed tomography (CT) scan of the abdomen is considered the best imaging method to confirm the diagnosis. The American College of Radiology (ACR) appropriateness criteria for left lower quadrant pain support this recommendation because of the specificity and sensitivity of CT scans, which allow for the diagnosis of the causes of left lower quadrant pain that resembles diverticulitis. [29]

Note the following:

  • CT scans are preferred over intraluminal examinations (eg, barium enema), because the bulk of the inflammation is extraluminal. CT scans can help clinicians assess disease severity, the presence of complications, and clinical staging. In the acute setting, CT scans are safer than contrast studies. Sensitivity and specificity, especially with helical CT scanning and colonic contrast, can be as high as 97%.

  • Possible CT scan findings include the following: pericolic fat stranding due to inflammation, colonic diverticula, bowel wall thickening, soft-tissue inflammatory masses, phlegmon, and abscesses. Peritonitis, fistula formation, and obstruction can also be assessed. In addition, CT scanning can be used to guide percutaneous drainage of an abscess.

Barium contrast enema is not the imaging modality of choice during an acute episode of abdominal pain and should only be considered in mild to moderate uncomplicated cases of diverticulitis when the diagnosis is in doubt, or for follow-up evaluation for suspected fistula. [29] A water-soluble contrast medium should be used, as leakage of barium into the peritoneum would be catastrophic.

Plain radiograph films are not helpful in making the diagnosis of diverticulitis. However, plain abdominal radiograph series with supine and upright films can demonstrate bowel obstruction or ileus. If free air is present, this can indicate bowel perforation.



Endoscopy is not recommended in the acute setting given the risk of worsening diverticulitis and bowel perforation. After the diverticulitis has subsided, colonoscopy can be used to evaluate the extent of diverticulosis or to rule out a malignancy masquerading as a benign postinflammatory stricture.

Similarly, when findings on computed tomography scan demonstrate are suspicious for colonic carcinoma, colonoscopy is the imaging modality of choice. [29]



Several staging schemes have been proposed for diverticulitis based on the clinical findings, disease extent on imaging studies, and the presence of complications. The simplest method may be to differentiate among asymptomatic diverticulosis, uncomplicated diverticulitis, and complicated diverticulitis.

Clinical staging by Hinchey's classification is based on computed tomography findings and directed toward selection of the proper surgical procedure when diverticulitis is complicated, as follows:

  • Stage I disease: Phlegmon or localized pericolic or mesenteric abscess

  • Stage II disease: Walled-off pelvic, intra-abdominal, or retroperitoneal abscess

  • Stage III disease: Perforated diverticulitis causing generalized purulent peritonitis

  • Stage IV disease: Rupture of diverticula into the peritoneal cavity, with fecal contamination causing generalized fecal peritonitis

Table. Modified Hinchey Classification Stage and Diverticulitis Category (Open Table in a new window)

Modified Hinchey Classification Stage



Clinically mild diverticulitis, or diverticula with colonic wall thickening on CT



Colonic reaction with inflammatory reaction in the pericolic fat (phlegmon)



Pericolic or mesenteric abscess



Intra-abdominal abscess, pelvic or retroperitoneal abscess



Generalized purulent peritonitis



Generalized fecal peritonitis