Background In neonatal units, increased output in nappies is recorded as urine output unless semi-formed or formed stools are noted. Watery stools are likely be recorded as increased urine output prompting renal line investigations delaying the diagnosis of congenital diarrhoeas.

Aim We present a case of congenital watery diarrhoea to highlight the diagnostic and treatment approaches in a neonate.

Subjects and Methods Reviewed the presentation and progress of a neonate admitted in NICU with abdominal distension and significant metabolic and electrolyte disturbance.

Results The neonate had diagnostic laparotomy for intestinal obstruction, he was suspected to have possible necrotising enterocolitis. By day 9 of life, he developed severe hyponatraemia, hypochloraemia and metabolic alkalosis and was identified to have high urine output. Had extensive renal investigations for polyuria which was unremarkable. With faltering of growth and need for TPN, gastrointestinal loss was suspected and profuse watery diarrhoea became apparent. Hypochloraemic, Hyponatraemic metabolic alkalosis with high stool chloride confirmed the diagnosis of congenital chloride diarrhoea. Treatment will involve (i) life-long salt substitution; (ii) management of acute dehydration and hypokalaemia during gastroenteritis or other infections; and (iii) recognition and treatment of other manifestations of the disease, such as intestinal inflammation, renal impairment and male sub fertility.

Summary and conclusion Congenital chloride diarrhoea is a rare autosomal recessive disease characterised by life-long watery diarrhoea of prenatal onset with high faecal chloride concentration. The diagnosis may easily be missed unless there is a high index of suspicion in a neonate with increased stool or presumed urine output.