Absence and retention of small bowel gas in infants with midgut volvulus: mechanisms and significance.

The radiographic pattern of high intestinal obstruction--gastric and duodenal distension with absence of small bowel gas (ASBG) or a completely gasless abdomen--may be present in infants with midgut volvulus. In most instances, ASBG is associated with viable small bowel. However, when associated with abdominal distension and tenderness ASBG usually reflects strangulated midgut volvulus and bowel necrosis. In some patients with midgut volvulus there is a radiographic pattern of low small bowel obstruction; this is generally associated with necrotic bowel. These seemingly opposite observations can be explained by reviewing the dynamics of gas absorption in normal bowel and in closed loop intestinal obstruction. Impaired blood supply can result in either gaslessness or gaseous distension under differing conditions. Key words: Infant, intestinal tract, intestinal gas, intestinal obstruction, intestinal volvulus, malrotation, gasless abdomen.