Hypertrophic pyloric stenosis is characterized by

Ans. b (Metabolic alkalosis). (Ref. LB, 25th/79)Hypertrophic pyloric stenosis of infancy (CHPS)Aetiology# The incidence of this condition is approximately three cases per 1000 births.# In some cases there seems to be a familial association.# The mucosa is compressed such that only a probe can be inserted.Clinical features# Characteristically it is a first-born male child that is most commonly affected.# The condition is most commonly seen at 4 weeks after birth ranging from the third week to, on rare occasions, the seventh. Most commonly affects boys aged 2-8 weeks.# Characterised by projectile vomiting after feeds and Gastric peristalsis can be seen and a lump felt# Weight loss is a striking feature and rapidly the infant becomes emaciated and dehydrated.Imaging# Ultrasonography is the investigation of choice. Contrast radiology is not now necessary.Treatment# Following diagnosis the first concern is to correct the metabolic abnormalities. Essentially this is the same situation that pertains in adults with the patient being dehydrated, with low sodium, chloride and potassium, and a metabolic alkalosis. The child should be rehydrated with dextrose--saline and potassium (2.5 per cent dextrose plus 0.45 percent sodium chloride plus 1 g of potassium chloride per 500 ml of fluid). This will restore the infant's clinical condition and electrolytes to normal. Following this operation is required.# Ramstedt's operation is surgery of choice.