Adynamic Ileus

Adynamic ileus results in the dilatation of loops of bowel from smooth muscle dysfunction, as opposed to mechanical obstruction. Dilatation may be localized or diffuse, depending on the etiology. The colon may or may not also be involved. The etiologies of ileus are numerous, ranging from inflammation (pancreatitis) to metabolic (hypokalemia) to drugs (opiates).

Like SBO, ileus manifests on imaging studies as dilated loops of bowel with air-fluid levels. As we discussed previously, it can sometimes be impossible to distinguish between SBO and ileus on imaging studies. Focal ileus can even have a transition point, similar to SBO. In contrast to SBO, however, ileus tends to have non-differential air-fluid levels (all air-fluid levels are at the same height).

A “sentinal loop” (localized dilated loop of bowel) represents a focal ileus and may be seen in localized abdominal inflammation (e.g. pancreatitis, cholecystitis).

Focal Ileus - Abdominal x-ray of patient with focal ileus associated with pancreatitis. 
Patient had lipase of 591.