Tests
1st tests to order
CBC with differential
Test
Polymorphonuclear leukocytosis is usually present in acute diverticulitis.[51] CBC results should be considered at the first encounter with a patient when diverticulitis is suspected.
Result
polymorphonuclear leukocytosis
CRP
Test
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]
Result
usually elevated
basic metabolic panel
Test
Assesses kidney function and helps to determine whether a contrast CT can be performed.[1]
Result
uremia, elevated creatinine
contrast CT scan of abdomen
Test
The imaging modality of choice to confirm suspicion of acute diverticulitis, evaluate the presence of complications, and rule out other conditions that may present in a similar way.[7][43][44][45][47]
CT may reveal signs of inflammation including pericolic fat stranding in acute diverticulitis, and helps rule out complications such as pericolic and pelvic abscesses, and diverticular phlegmon. Other findings in patients with acute diverticulitis include colonic diverticula with associated colon wall thickening, fat stranding, phlegmon, extraluminal gas, abscess formation, or intra-abdominal free fluid.[7] CT may also exclude other diagnoses, such as ovarian pathology or leaking aortic or iliac aneurysm.[7]
If contrast CT is contraindicated, consider noncontrast CT, magnetic resonance imaging, or an ultrasound scan; this should be discussed with the local radiology team.[3][7][44][46][47]
Result
thickening of bowel wall, mass, abscess, streaky mesenteric fat; may show gas in the bladder in cases of fistula
Tests to consider
blood culture
Test
Should be considered prior to administration of antibiotics in patients with signs or symptoms of sepsis, and those who are severely ill.
Result
usually gram-negative rods, and anaerobic bacteria
ABG and serum lactate
Test
Should be considered in patients with signs or symptoms of sepsis and patients who are severely ill.
Result
acidosis, elevated serum lactate in patients with sepsis
noncontrast CT scan of abdomen
Test
Consider noncontrast CT if contrast CT is contraindicated; this should be discussed with the local radiology team.[47]
Result
thickening of bowel wall, mass, abscess, streaky mesenteric fat; may show gas in the bladder in cases of fistula
abdominal ultrasound (graded-compression)
abdominal MRI scan
colonoscopy or sigmoidoscopy
Test
An early colonoscopy or flexible sigmoidoscopy may be required to rule out underlying malignancy in patients presenting with presumed diverticulitis 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. In cases of recalcitrant or smoldering diverticulitis despite aggressive medical treatment, a limited flexible sigmoidoscopy without air insufflation will help identify a perforated rectosigmoid carcinoma mimicking acute diverticulitis. Great care is necessary during these endoscopic procedures to avoid perforation.
Result
single, multiple, or scattered diverticula, with or without acute mucosal inflammation; if coexistent, mucosal pathology such as ischemia, inflammatory bowel disease, and neoplasm may be seen
diagnostic laparoscopy/exploratory laparotomy
Test
Consider if primary diagnosis is unclear.
Result
diverticuli, abscess, perforation, obstruction, fistula
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