An intact female, 5-year old, Shihtzu, weighing 3.2 kg with a history of depression, hypersalivation, dullness, and ataxia for 3 days was referred. Radiographic findings included microhepatica, bilateral renal calculi, and a cystic calculus. Ultrasonography showed microhepatica, decreased visibility of portal veins in the liver, bilateral renal calculi, a cystic calculus, and an abnormal tortuous dilated vessel in the craniodorsal abdomen. A single congenital extrahepatic portoazygous shunt was confirmed through operative mesenteric portography. The patient received surgery using an ameroid constrictor ring and recovered well.