True statement regarding congenital hypertrophic pyloric stenosis

i.e. (Metabolic alkalosis): (78-79-Love & Bailey 25th) (174-75-CSDT 13th)Repititive vomiting leads to hypocholeremic hypokalemic metabolic alkalosis. The urine is alkaline initially but eventually it becomes acidic (paradoxical aciduria)**INFANTILE HYPERTROPHIC PYLORIC STENOSIS* Most commonly affects boys M>F (4:1) aged 2-8 weeks it is rare after 3 months of age* Characteristically the first born male child is affected* Projectile non bilious vomiting (Typically the baby feeds hungrily and vomits non-bilious milk curds towards the end of a feed). Blood may be seen in the vomitus in 5% of cases and coffee grounds or occult blood is frequently present* With dehydration infants often have sunken fontanelles with dry mucous membranes and poor skin turgor, weight loss following progressive feeding intolerance* Jaundice with indirect hyper bilirubinemia occurs in fewer than 10% of cases* Gastric peristaltic waves can usually be seen moving from the left costal margin to the area of the pylorus* In over 90% of cases the pyloric "tumor" or "olive" can be palpated when the infant is relaxed* Erythromycin in early infancy has been linked to the subsequent development of hypertrophic pyloric stenosis* Gastritis and reflux esophagitis occurs frequently, Aspiration of vomitus may produce pneumonia* Abdominal ultrasound is the most sensitive and specific test (when the muscle thickness is greater than 4 mm and length of the pylorus is greater than 16 mm)* Contrast upper gastrointestinal series is indicated(i) If an experienced ultrasonographer is unavailable(ii) If there is a reasonable chance that patients symptoms are not due to pyloric stenosis (eg a premature, 1 week old baby)* Treatment - Fredet - Ramstedt pyloromyotomy