Midnight Louie Gehres, a six year old, male-neutered, domestic short haired cat, presented to the Cornell University Hospital for Animals Small Animal Internal Medicine Service in December 2001 for diagnostic tests to investigate a suspected portosystemic shunt. The cat had a three year history of severe, intermittent urinary tract signs, including recurrent urinary tract infections, cystitis, urinary tract obstructions and cystic calculi. In the three years prior to presentation, the cat had several cystotomies; stone analyses revealed struvite, calcium oxalate, and ammonium biurate stones. In the three months prior to presentation, the cat had elevated post-prandial bile acids on three separate tests. Pre-prandial levels were variable.