Case 1: Progressive vomiting in a three-week-old infant

Abstract

A 20-day-old female infant was transferred from a peripheral hospital with progressive vomiting and weight loss. The infant was born to a 31-year-old primiparous mother at 37 weeks’ gestation by spontaneous vaginal delivery. The pregnancy was uncomplicated, apart from a positive screen for group B streptococcus, which was adequately treated during labour. The infant’s birth weight was approximately 3 kg. Vomiting began at seven days of age, when nystatin was started for treatment of oral thrush. The vomiting progressively became more frequent and projectile in nature. By the time of admission, at three weeks of age, the infant had projectile nonbilious vomiting that occurred 1 h to 2 h after every attempted feeding. She appeared hungry immediately after vomiting. The infant had been offered two different formulas (Enfamil [Mead Johnson Nutritionals, Ottawa, Ontario] and Goodstart [Nestle Canada]), and minimal expressed breastmilk by bottle since birth. The formula changes did not result in symptomatic improvement. She was offered approximately 60 mL of feed every 2 h to 3 h. Her bowel movements were normal, apart from a few loose, nonbloody stools on the day of admission. Her parents reported that there had been four to five wet diapers per day before admission. The infant was otherwise healthy, with no fever, rash or systemic symptoms. Both parents were healthy and of Italian descent. Family history was not contributory. The infant’s admission weight was 2180 g (25% less than her birth weight), with the clinical appearance of significant dehydration and malnutrition (little subcutaneous fat and muscle wasting). She was afebrile, with stable vital signs for her age, including a pulse rate of 120 beats/min after initial fluid resuscitation of 20 mL/kg of 0.9% saline followed by isotonic fluid at a maintenance rate. Her abdomen was soft, scaphoid and nontender, with no organomegaly. There were no palpable masses, including no palpable ‘olive’ when the baby was quiet. The remainder of the examination was normal, apart from slight oral thrush. Initial laboratory investigations revealed severe metabolic alkalosis with venous pH 7.64, PCO2 50 mmHg, bicarbonate 54 mmol/L and base excess +26 mmol/L. Electrolytes were abnormal with serum sodium 119 mmol/L, potassium 4.7 mmol/L, chloride lower than 50 mmol/L and glucose 10.9 mmol/L. Both urea and creatinine concentrations were significantly elevated (blood urea nitrogen 22.7 mmol/L and creatinine 261 μmol/L). The infant’s complete blood count was normal, apart from thrombocytosis (767×109/L). Her urine pH was greater than 9.0 and specific gravity was 1.010 g/L; she had normal microscopy, except for 2+ protein. Her abdominal ultrasound revealed stomach contents passing through a nonhypertrophied pylorus that was seen to open and close normally. The infant’s abdominal radiograph showed a small amount of gas in a single, mildly prominent structure in the mid-abdomen and a paucity of bowel gas in the remainder of the abdomen. An additional investigation revealed the diagnosis.