Approach

Acute diverticulitis should be suspected in patients who present with left lower quadrant abdominal pain or tenderness, with or without fever.[44][45]​​​ The onset of pain is usually acute or subacute.[44] Leukocytosis may be present, although the traditional triad of left lower quadrant pain, fever, and leukocytosis are all present in only around a quarter of cases.[44] Most cases occur in individuals who are >40 years of age.

Contrast computed tomography (CT) scan should be requested in a patient with suspected acute diverticulitis, particularly if this is a patient's first episode.[44] CT with contrast is highly accurate in confirming clinical suspicion of diverticulitis.[44] This is important in order to rule out alternative diagnoses, and in patients with more severe symptoms to rule out a complication of diverticulitis.​​[3][7][43][44][46][47]​​​​​​

History

Patients with acute diverticulitis usually have constant left lower quadrant abdominal pain, and may have fever, and change in usual bowel habits including bloating, constipation, or diarrhea.[27]​ Tenderness, rebound, and guarding may be present in the left lower quadrant of the abdomen.[1]

Although acute diverticulitis is the most common cause of left lower quadrant pain, it is a nonspecific symptom; clinical suspicion of diverticulitis is only correct in 40% to 65% of patients.[44]​ Other common causes include colitis, inflammatory bowel disease, epiploic appendagitis, bowel obstruction, hernia, ovarian and fallopian tube pathology, pyelonephritis, and urolithiasis.[44] Perforated colon cancer can also mimic diverticulitis.[44]

Complicated acute diverticulitis (e.g., with abscess, fistula, or perforation) should be suspected in patients with more severe, uncontrolled abdominal pain plus any of the following:[1]

  • Abdominal rigidity or guarding, which may indicate bowel perforation or peritonitis.

  • Signs of sepsis.

  • Colicky abdominal pain, absolute constipation, vomiting, or abdominal distention, as these may be symptoms of a diverticular stricture causing large bowel obstruction. See Large bowel obstruction.

  • Pneumaturia or fecaluria as these are symptoms of colovesical or colovaginal fistulas caused by diverticulitis.

For further information, see Complications within this topic, and the topic Evaluation of acute abdomen.

Atypical presentations of diverticulitis include right-sided lower abdominal pain associated with right-sided diverticulitis (more common in patients of Asian heritage) or a floppy redundant sigmoid colon that can be palpated in the right lower quadrant.[9][10]​​​ Right-sided diverticulitis may mimic acute appendicitis, but patients are unlikely to describe prodromal symptoms typical of appendicitis.[48]​ In a small number of cases, patients with diverticulitis will experience pain in a different area of the abdomen (suprapubic, left upper quadrant, epigastric, right lower quadrant).[49]

Diverticulosis is asymptomatic and often diagnosed incidentally, during screening colonoscopy or barium enema for other indications.[50]​ Physical exam and blood tests are usually normal in asymptomatic patients.

Physical exam

Physical findings depend on the clinical type and severity of diverticulitis. Systemic signs of inflammation, such as fever, may be present.[7]

In complicated diverticulitis, especially with abscess and peritonitis, patients will have signs of peritonitis (rebound tenderness, rigidity) and may have a palpable, tender abdominal mass. Patients with free perforation and generalized peritonitis may have diffuse abdominal tenderness. A fullness or mass may be palpable in cases of abscess formation. Pelvic tenderness on digital rectal exam is also a helpful sign.

Laboratory tests

All patients require complete blood count (CBC), looking for leukocytosis with neutrophilia, basic metabolic panel, and measurement of markers of inflammation including C-reactive protein (CRP). In acute diverticulitis, a CBC with differential usually reveals polymorphonuclear leukocytosis although blood tests may be normal or demonstrate only a mild leukocytosis in uncomplicated diverticulitis.[51]​ Nonspecific inflammatory markers are often elevated; an initial CRP concentration above 17 mg/dL (170 mg/L) can predict complicated diverticulitis, although a low CRP does not rule out complicated diverticulitis.​[2][7]​​​ In uncomplicated diverticulitis, CRP is usually elevated, though below 17 mg/dL (170 mg/L). An alternative diagnosis should be considered if inflammatory markers are not elevated.[1]

Assessing kidney function helps to determine whether a contrast computed tomography scan can be performed safely.[1]

Blood cultures and arterial blood gas with serum lactate should be considered in patients with signs or symptoms of systemic sepsis and those who are severely ill.

Imaging

In patients with suspected acute diverticulitis, a computed tomography (CT) scan of the abdomen with contrast is the standard diagnostic test to confirm clinical suspicion, evaluate the extent of disease, and rule out diverticular complications.​[3]​​[7][43][44][45][47]​​​​​​ CT scanning has largely replaced contrast enema for this scenario.​[3][7][43][44]​​​​[46]​​​ If a patient has typical symptoms of diverticulitis, a prior history of the condition with similar symptoms, and no evidence of complications, it may be reasonable to proceed to treatment without imaging.​[43][44]​ However, it is important to be aware of the risk of misdiagnosis based on clinical assessment alone.[44]

CT in patients with acute diverticulitis may show colonic diverticula with associated colon wall thickening, fat stranding, phlegmon, extraluminal gas, abscess formation, or intra-abdominal free fluid.[7] CT may help to rule out or confirm complications including pericolic and pelvic abscesses, and diverticular phlegmon. CT is also useful to exclude other diagnoses that can present in a similar way (e.g., ovarian pathology or leaking aortic or iliac aneurysm).[7]

If contrast CT is contraindicated, a noncontrast CT, magnetic resonance imaging, or an ultrasound scan should be considered and the local radiology team should be consulted.​[3][7][44][46]​​​[47][52]

An early colonoscopy or flexible sigmoidoscopy may be required to rule out underlying malignancy in patients who present with presumed diverticulitis but who develop rectal bleeding or recalcitrant inflammatory disease not responsive to conservative treatment.[53]​ A limited flexible sigmoidoscopy without air insufflation will help identify a locally perforated rectosigmoid carcinoma mimicking acute diverticulitis. Flexible sigmoidoscopy or colonoscopy can be considered when diagnosis of diverticulitis is unclear or when cancer or bowel ischemia is suspected. Great care is necessary during these endoscopic procedures to avoid perforation. See Colorectal cancer and Ischemic bowel disease.

Diagnostic or exploratory surgery

If the primary diagnosis is still unclear after laboratory tests and imaging, a diagnostic laparoscopy should be considered and may also provide therapeutic options.

Exploratory laparotomy may be required if the diagnosis is uncertain.

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