Mixed acid-base disturbances due to presumed congenital pyloric stenosis in a 7-month-old Holstein-Friesian calf.

A 7-month-old female Holstein-Friesian calf was presented with a lifelong history of failure to thrive. She was severely dehydrated on presentation. Venous blood gas and serum biochemistry analyses revealed mixed acid-base disturbances, including a hypochloremic metabolic alkalosis indicative of pyloric outflow obstruction. She also had acidic urine. The calf continued to decline and was euthanized. At necropsy, the pyloric opening was markedly narrowed and difficult to find. As there were no accompanying lesions such as inflammation, ulceration, or fibrosis, presumed congenital pyloric stenosis was diagnosed. Clinicians should include congenital pyloric stenosis on their list of differential diagnoses when examining a calf with pyloric outflow obstruction, even if the calf is older. Key clinical message: Hypochloremic metabolic alkalosis with paradoxic aciduria can occur with many causes of pyloric outflow obstruction. Other acid-base disturbances can also be present. In calves, congenital pyloric stenosis should be considered as a potential cause, even in animals that are no longer neonates.