Postoperative Ileus Differential Diagnoses

Updated: Nov 01, 2021
  • Author: Burt Cagir, MD, FACS; Chief Editor: Vinay K Kapoor, MBBS, MS, FRCSEd, FICS, FAMS  more...
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Diagnostic Considerations

The common differentials for ileus are pseudo-obstruction, also referred to as Ogilvie syndrome, and mechanical bowel obstruction.


Pseudo-obstruction is defined as acute, marked distention of the large bowel. As with ileus, it occurs in the absence of a definable mechanical pathology. Several texts and articles tend to use ileus synonymously with pseudo-obstruction or refer to "colonic ileus." However, the two conditions are definitely distinct entities. Pseudo-obstruction is clearly limited to the colon alone, whereas ileus involves both the small bowel and colon. The right colon is involved in classic pseudo-obstruction, which typically occurs in elderly bedridden patients with serious extraintestinal illness or in trauma patients. Pharmacologic agents, aerophagia, sepsis, and electrolyte discrepancies may also contribute to this condition.

The condition termed chronic intestinal pseudo-obstruction is also observed in patients with collagen-vascular diseases, visceral myopathy, or neuropathy. This chronic form of pseudo-obstruction involves dysmotility of both the large and small intestine. This dysmotility is due to loss of the migrating motor complex and bacterial overgrowth. This entity manifests as clinical small bowel obstruction.

Physical examination usually reveals marked abdominal distention without pain or tenderness; however, patients may have symptoms mimicking obstruction. Plain abdominal radiography reveals isolated, proximal large bowel dilatation, as shown in the image below, and contrast imaging distinguishes this from mechanical obstruction.

Ogilvie pseudo-obstruction in a septic elderly pat Ogilvie pseudo-obstruction in a septic elderly patient. Note the massive dilatation of the colon, especially the right colon and cecum.

The colonic distention may lead to perforation of the cecum, especially if the cecal diameter exceeds 12 cm. The mortality rate for pseudo-obstruction is 50% if patients progress to ischemic necrosis and perforation. [17]

Initial treatment includes hydration, rectal and nasogastric tube placement, correction of electrolyte imbalances, and discontinuation of medications that hinder bowel motility. Decompression via colonoscopy is quite effective in relieving pseudo-obstruction. Intravenous neostigmine may also be effective, resulting in resolution of pseudo-obstruction within 10-30 minutes. [24] A 2.5-mg dose of neostigmine is slowly infused over 3 minutes under close cardiac monitoring, particularly in patients with known cardiac conditions, to observe for bradycardia. If bradycardia occurs, atropine should be administered. Laparotomy with ostomy creation and bowel resection for peritonitis and ischemia is the last resort.

Mechanical obstruction

Mechanical bowel obstruction can be caused by postoperative adhesions, volvulus, hernias, intussusception, foreign bodies, or neoplasms. Patients present with severe cramping abdominal pain that is paroxysmal in nature. Physical examination reveals borborygmi coincident with the abdominal cramping. In thin patients, peristaltic waves may be visualized. Auscultation may reveal high-pitched, tinkling sounds associated with gurgles and rushes, which is in marked contrast to the hypoactive or absent bowel sounds of ileus. If obstruction is complete, patients report constipation or obstipation. Vomiting may or may not occur if the ileocecal valve is competent and prevents reflux. Peritoneal signs manifest if patients develop a strangulated obstruction or perforation.

Endoscopy and contrast imaging aid in the diagnosis of mechanical bowel obstruction. In mechanical obstruction, imaging reveals enlarged bow-shaped loops of small intestine with steplike air-fluid levels; the colon may have a paucity of gas distal to the lesion on plain radiographs, as demonstrated in the images below.

Mechanical bowel obstruction due to a left colon c Mechanical bowel obstruction due to a left colon carcinoma. Note the paucity of bowel gas throughout the colon.
Contrast study, in the same patient as in the prev Contrast study, in the same patient as in the previous image with mechanical bowel obstruction due to a left colon carcinoma. This image shows the classic "apple-core" lesion of colon carcinoma.

The following table summarizes the differences between ileus, pseudo-obstruction, and mechanical obstruction.

Table. Characteristics of Ileus, Pseudo-obstruction, and Mechanical Obstruction (Open Table in a new window)




Mechanical Obstruction (Simple)


Mild abdominal pain, bloating, nausea, vomiting, obstipation, constipation

Crampy abdominal pain, constipation, obstipation, nausea, vomiting, anorexia

Crampy abdominal pain, constipation, obstipation, nausea, vomiting, anorexia

Physical Examination Findings

Silent abdomen, distention, tympanic

Borborygmi, tympanic, peristaltic waves, hypoactive or hyperactive bowel sounds, distention, localized tenderness

Borborygmi, peristaltic waves, high-pitched bowel sounds, rushes, distention, localized tenderness

Plain Radiographs

Large and small bowel dilatation, diaphragm elevated

Isolated large bowel dilatation, diaphragm elevated

Bow-shaped loops in ladder pattern, paucity of colonic gas distal to lesion, diaphragm mildly elevated, air-fluid levels