Congenital chloride diarrhea misdiagnosed as pseudo-Bartter syndrome
A 15-month-old girl presented to our department (Al-zahra Hospital, Isfahan, Iran) for failure to thrive and poor feeding in 2011. She was born with polyhydramnios from healthy non-consanguineous parents at 32 weeks of gestation. She had a birth weight of 2050 g and body length of 42 cm, which were appropriate for her age. Following birth, she was admitted to the neonatal surgery department due to abdominal distention, lack of meconium and dilated bowel loops in abdominal X-rays and abdominal sonography (include figures), with suspection to intestinal obstruction and received conservative treatment. Hirschprung disease, hypertrophic stenosis of pylorus and intestinal obstructions were ruled out. She was discharged after 7 weeks with feeding tolerance and normal defecation. Serum levels of sodium (Na+), potassium (K+), blood urea nitrogen (BUN) and creatinine (Cr) at the time of discharge were 139 mEq/L (normal: 135-145), 3.7 mEq/L (normal: 3.5-5.5), 19 mg/dL (normal: 6-20) and 0.9 mg/dL (normal: 0.3-1.2), respectively. In the abdominal ultrasonography, both kidneys had normal parenchymal echotexture without any stone or hydronephrosis. Liver and spleen were normal in size and echotexture. Intestinal loops were dilated.\nAfter 2 months, she was admitted to a hospital because of moderate dehydration suspecting polyuria. Serum levels of Na+, K+, BUN and Cr were 110 mEq/L, 2.7 mEq/L, 40 mg/dL and 0.5 mg/dL, respectively. Urine analysis was normal with a pH of 6. After 5 days, she was discharged in a stable condition. However, she was presented to another hospital due to poor feeding and anuria after 10 days. Regarding her past medical history, she was referred again to our center for specific workup.\nAt the time of admission, physical examination showed severe dehydration, severe failure to thrive without organomegaly and low grade fever with mild diarrhea. Laboratory data revealed white blood cell count, hemoglobin, platelets, serum Na+, serum K+, BUN and Cr, 5800/mm3, 10.6 g/dL, 880 × 103/mm3, 133 mEq/L, 2.6 mEq/L, 130 mg/dL and 5.1 mg/dL, respectively. Blood gas analysis showed a normal anion gap acidosis with a pH of 6.9, carbon dioxide partial pressure (pCO2) of 10 mmHg and HCO3− of 4 mEq/L (normal: 22-26). The enzymes alanine aminotransferase and aspartate aminotransferase, as liver function indicators, were normal. Finally, she underwent peritoneal dialysis. After 4 days, Cr level decreased to 1.1. Shohl's solution (polycitra) was then prescribed for her. Distal renal tubular acidosis (type I) was considered as the main diagnosis and she was discharged home in a stable condition.\nWhile being treated with Shohl's solution, thiazide and zinc sulfate, the patient was followed-up for 6 months in the nephrology clinic. She did not gain weight within this period and returned with severe dehydration. She was resuscitated with 40 cc/kg normal saline. New laboratory findings showed a serum Na+ level of 134 mEq/L, K+ level of 2.1 mEq/L and chloride (Cl−) level of 82 mEq/L (normal: 98-108). Metabolic alkalosis (pH = 7.57, pCO2 = 32 mmHg and HCO3- = 34 mEq/L) and hyperreninemia (129 μIU/ml) and hyperaldosteronemia (317 pg/ml) was also observed. At this point, pseudo-Bartter syndrome was suspected and the treatment began promptly. She had a dramatic response to intravenous (IV) therapy and hypokalemia resolved quickly (despite what is normally seen in pseudo-Bartter syndrome), urine electrolytes on admission were: Na+ 67 mEq/L, K+ 28.3 mEq/L and Cl− 2 mEq/L. Consequently, all treatments were halted and a new diagnostic workup was planned to reach the definite diagnosis. A new history from the mother revealed that the patient has had loose defecation during the past months which has been considered as normal by the mother and she had never passed normal stools; watery content of diarrhea since infancy had been confused with that of urine.\nFollowing consultation with our gastroenterologist, measuring stool electrolytes showed Na+ of 64 mEq/L (normal: 20-30 mEq/L), K+ of 50 mEq/L (normal: 55-65 mEq/L) and Cl− of 120 mEq/L (normal: 5-20 mEq/L) were confirmed with repeated analyses. Stool pH was 5. Upper gastrointestinal endoscop, rectosigmoidoscopy, histopathology of duodenoum and rectosigmoid were normal. Stool microscopy and cultures were normal. Stool reductant material and fat were negative. Celiac serologic tests were negative. Cystic fibrosis was ruled out by normal sweat test. With these findings, CCD was established for her and treatment began by IV fluid replacement and total parentral nutrition, which resulted in a 1-kg weight gain after 1 month. Fortunately, the patient was discharged after 1 month with oral omeprazole, 3 mg/kg/day, potassium chloride (KCl 2 mEq/kg/day), sodium chloride (NaCl 3 mEq/kg/day), cholestyramine (150 mg/kg/day), multivitamin (as recommended daily allowance [RDA]) and mineral pills (as RDA). She was followed with gastroenterological, nutritional and nephrological services for 1 year. Her condition gradually improved and she does not have a major problem except mild to moderate delayed growth and development at the present time. Her food tolerance is also acceptable.