Acute Colonic Pseudoobstruction (Acute Megacolon, Ogilvie Syndrome) Workup

Updated: Jan 24, 2020
  • Author: Roberto M Gamarra, MD; Chief Editor: BS Anand, MD  more...
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Laboratory Studies

Laboratory studies are directed at establishing the etiology of the acute megacolon (acute colonic pseudoobstruction [ACPO], Ogilvie syndrome), assessing the patient’s fluid status, as well as evaluating the presence of any complications. These studies include the following:

  • Complete blood cell (CBC) count
  • Electrolyte levels (including calcium, magnesium, and phosphorus)
  • Serum lactate level
  • Blood urea nitrogen (BUN) and creatinine measurements
  • Levels of aminotransferases, alkaline phosphatase, bilirubin, amylase, and lipase (to evaluate for other potential causes of abdominal pain)
  • Thyroid studies
  • Stool studies (including leukocytes, ova and parasites, and  C difficile toxin assay)
  • Blood cultures

Imaging Studies

Imaging studies are used to determine the severity of acute colonic pseudoobstruction (ACPO) (acute megacolon, Ogilvie syndrome), to exclude free intraperitoneal air (perforation) as well as other etiologies (eg, extrinsic compression), and to follow the clinical course. [17]

Plain x-ray films of the abdomen demonstrate the massive gaseous distention of the colon. Generally, the small bowel is not seen. Dilation of all segments of the colon support the diagnosis of pseudoobstruction.

Other imaging studies, such as hypaque (water soluble radiopaque contrast material) enema, computed tomography (CT) scanning, or magnetic resonance imaging (MRI), may also be used to exclude obstruction.



Perform other tests only to rule out a mechanical obstruction. Depending on the setting, severity, and condition of the patient, these tests may include either a colonoscopic examination (which also may be therapeutic) or a water-soluble contrast enema. Colonoscopy is preferred because of its diagnostic and therapeutic potential.