Intussusception in children: current concepts in diagnosis and enema reduction.

Intussusception cannot be reliably ruled out with clinical examination and plain radiography. However, a contrast material enema study and ultrasonography (US) allow definitive diagnosis of intussusception. The components of an intussusception produce characteristic appearances on US scans. These appearances include the multiple concentric ring sign and crescent-in-doughnut sign on axial scans and the sandwich sign and hayfork sign on longitudinal scans. Indicators of ischemia and irreducibility are trapped fluid at US and absence of blood flow at Doppler imaging. The aim of enema therapy is to reduce the greatest number of intussusceptions without producing perforation. Barium, water-soluble contrast media, water, electrolyte solutions, or air may be used with radiographic or US guidance. The differences in reduction and perforation rates between the various types of enemas are probably due more to perforations that occurred before enema therapy and the pressure exerted within the colon than to the contrast material used. The pressure within the colon is more constant with hydrostatic reduction than with air reduction; this fact may explain the lower risk of perforation with hydrostatic reduction. Radiation exposure is lower with air enema therapy than with barium enema therapy and is absent in US-guided enema therapy.