Paediatrics: Idiopathic hypertrophic pyloric stenosis

Idiopathic hypertrophic pyloric stenosis

The incidence of idiopathic hypertrophic pyloric stenosis (IHPS) is 73/1000 live births. Boys are affected more frequently than girls and IHPS is more common in Whites than in dark-skinned races. The pylorus enlarges as a result of hypertrophy of the circular muscle to produce the typical ‘tumour’. The cause remains unknown. Familial occurrence is well docu-mented, particularly in girls.

Clinical features (Fig. 23.6)

•   Vomiting: projectile, starting in the third or fourth week of life. The vomitus is always non-bilious, but it may contain altered blood (‘coffee ground’) or fresh blood from oesophagitis. Vomiting occurs within an hour of feeding and the baby is immediately hungry. Vomiting may not be projectile in babies who present early (first or second week); they are often misdiagnosed as suffering from GOR.

•   Constipation is common due to reduced fluid intake.

•   Dehydration, malnutrition, and jaundice are late signs.

•   IHPS is rare beyond 12wks of age.

Diagnosis

•   Test feed: the baby is allowed to feed from the breast or bottle whilst the examiner palpates the baby’s abdomen. This is best conducted with the baby resting on the mother’s lap, cradled on her left arm. The examiner sits opposite the mother, on the baby’s left. Visible waves of gastric peristalsis may be seen passing across the upper abdomen. The pyloric tumour is usually easiest to feel either early in the feed or after the baby has vomited. 60–90% tumours are palpable. The thickened pylorus is palpable as a firm, ‘olive-shaped’ mass, just above and to the right of the umbilicus during a ‘test feed’.

•   US: if a tumour cannot be felt, US will usually confirm or exclude the diagnosis.

•   Biochemistry: the biochemical abnormality of IHPS is a hypochloraemic, hypokalaemic metabolic alkalosis (Fig. 23.7). Assess degree of alkalosis at presentation and monitor correction prior to surgery.

Pre-operative management

•   Rehydrate and correct the alkalosis before surgery.

•   IV fluids should be started. 0.45% Saline with 5% dextrose and 20mmol/L potassium chloride at 120mL/kg/day.

•   Feeds: withhold. The stomach should be emptied with a NGT.

•   Electrolytes and capillary blood pH: should be checked regularly until they return to normal (usually 24–48h).

•   Blood glucose: should be monitored.

Surgery

•   Ramstedt’s pyloromyotomy: the treatment of choice (Fig. 23.8). This involves splitting the thickened pyloric muscle. Complications include perforation of the mucosa, which is not serious provided it is recognized and repaired, and wound infection.

•   Oral feeds are usually withheld overnight. Transient post-operative vomiting is common but invariably settles within 36h. There are no long-term sequelae.