Congenital sodium diarrhoea (CSD) is one of the rare causes of secretary diarrhoea that can present very early in life, and even in utero. It is due to an inborn defect of the intestinal sodium/proton exchanger localized in the apical membrane of small intestinal epithelial cells. To date, six isoforms of the sodium/proton exchanger has been identified. This defect leads to severe diarrhoea, voluminous alkaline stools with a high concentration of sodium, features that result in hyponatremic dehydration and normal anion gap metabolic acidosis.
It has been difficult to investigate the precise origin of CSD in a systematic manner due to its rarity. Early recognition, prevention of dehydration, and sodium and bicarbonate (citrate) supplementation are the mainstays of therapy. Lopeamide hydrochloride has been used to increase intestinal sodium absorption in a few cases with success.
We report a pre-term baby boy with a birth weight of 1.4 kg who was referred because of rapidly rising serum urea and creatinine. The initially reported high urine output was later found to be severe watery diarrhea with severe oliguria and acute renal failure. Associated findings were normal anion gap metabolic acidosis with hyponatremia that required >50 mmol/kg of sodium per day for correction and about 300 ml/kg per day of replacement fluid to correct fluid and electrolyte abnormalities. The patient continues to do well 8 months after diagnosis.