Which is the MOST common biochemical abnormality seen in congenital pyloric stenosis?

Neonates with congenital pyloric stenosis develop projectile postprandial vomiting between 2 and 4 weeks of age but may sta as late as 12 weeks. Due to this vomiting they develop hypokalemic hypochloremic metabolic alkalosis. Congenital pyloric stenosis is more commonly found in males. Projectile vomiting occurring in neonate is nonbilious. On examination, the upper abdomen gets distended after feeding, and prominent gastric peristaltic waves can be seen from left to right. An oval mass in the shape of an olive can be palpated in the right upper abdomen, especially after vomiting. USG done in them shows a hypoechoic muscle ring greater than 4 mm thick with a hyperdense center and a pyloric channel length greater than 15 mm. Ref: CURRENT Diagnosis & Treatment: Pediatrics, 21e chapter 21.