Small Left Colon Syndrome

Small left colon syndrome is a transient functional obstruction in newborns in which the colon from the splenic flexure to the rectum is narrow, with dilated colon proximal to it.

It is rare and presents in the first days of life. It is seen most often in infants of mothers with diabetes. Most cases resolve within days to a week.

Associations include maternal diabetes, maternal magnesium sulphate treatment, prematurity, and occasionally Hirschsprung disease and cystic fibrosis.

Pathophysiology.

The cause is not fully defined. Immaturity of left colonic motility and the effects of maternal hyperglycaemia and altered gut hormone signalling are proposed.

The narrowed segment is functionally hypoactive. It contains little meconium, giving the appearance of microcolon distally and an abrupt change at the splenic flexure.

• Failure to pass meconium, abdominal distension and bilious vomiting in the first 48 hours.
• Hypoglycaemia and macrosomia in infants of mothers with diabetes.

Red flags.

• Persistent obstruction beyond a week, or recurrent distension after initial improvement, indicating Hirschsprung disease or cystic fibrosis.
• Fever, bloody diarrhoea or shock suggesting enterocolitis or perforation.

• Abdominal X-ray shows low obstruction with dilated loops.
• Water soluble contrast enema is diagnostic: a narrow calibre rectum, sigmoid and descending colon, dilated proximal colon and a transition at the splenic flexure. The study often triggers evacuation.
• Blood glucose, calcium and thyroid function.
• Persistent disease: suction rectal biopsy at least 2 cm proximal to the dentate line, and sweat chloride (over 60 mmol/L is diagnostic) or genetic testing for cystic fibrosis once the infant is over 2 weeks old and 2 kg.

Differential diagnosis. Hirschsprung disease, meconium plug syndrome, ileal atresia, meconium ileus, anorectal malformation and sepsis with ileus.

• Nil by mouth, nasogastric decompression and IV maintenance fluids of 60 to 80 mL/kg on day 1.
• Contrast enema using isotonic or diluted low osmolar contrast often resolves the obstruction. Repeat rectal washouts with 10 mL/kg of warm 0.9% sodium chloride if stools stay scanty.
• Treat hypoglycaemia in infants of mothers with diabetes: feed or give IV glucose 10% 2 mL/kg when plasma glucose is under 2.6 mmol/L, then infuse glucose at 5 to 8 mg/kg/min.
• Reintroduce feeds slowly once stool passes and distension settles.

Monitoring. Stool passage, abdominal girth, glucose and feed tolerance. Review at 4 to 6 weeks.

Referral and escalation. Refer to paediatric surgery for perforation, failure to resolve within a week, or histological concern. Optimise maternal glycaemic control in later pregnancies.