Small Left Colon Syndrome in Infants

Affected infants present shortly afterbirth with a large bowel obstructionsecondary to transient dysmotility inthe descending colon. Although thecause is unknown, immaturity of thecolonic myenteric plexuses has beendemonstrated in some cases. Morethan 50% of affected infants are bornto mothers with diabetes. Other predisposingfactors include hypoglycemiaand sepsis.Hypoglycemia stimulates thesympathetic nervous system and thevagus nerve. Sympathetic stimulationresults in decreased peristalsis in theleft colon, and vagal stimulation leadsto increased motility to the level ofthe splenic flexure. Hyperglucagonemia,which may result from hypoglycemiaor sepsis, also leads to decreasedperistalsis in the left colon.Decreased motility results in increasedabsorption of water from thecolon, which eventuates in the formationof abnormal meconium.Infants with small left colon syndromepresent with progressive abdominaldistention, vomiting, and failureto pass meconium. Unusual latecomplications include bowel perforationand peritonitis.Plain abdominal radiographsshow dilated intestinal loops; air-fluidlevels are seen frequently (A). A bariumenema shows a small left colon,usually to the level of the splenic flexure,with proximal dilatation of thelarge bowel (B). The contrast enemais usually followed by rapid evacuationof meconium and decompressionof the bowel, which relieves the condition.A rectal biopsy is warranted ifsymptoms of intestinal obstructionpersist.