Which electrolyte abnormality is commonly seen in gastric outlet obstruction?

In gastric outlet obstruction, persistent vomiting leads to the loss of large volumes of gastric fluid rich in hydrochloric acid (HCl). This results in a decrease in serum chloride and hydrogen ions, causing a hypochloremic metabolic alkalosis. Additionally, volume depletion activates the renin-angiotensin-aldosterone system, promoting renal retention of sodium and bicarbonate, further worsening the alkalosis. This characteristic electrolyte disturbance helps in the clinical diagnosis and management prior to surgical correction.

Reference: Schwartz's Principles of Surgery, 11th Edition.