Diagnosing portosystemic shunts (PSS) can be challenging in veterinary patients. Multiple imaging techniques have been described to diagnose PSS. The aim of the study was to investigate whether a novel multi-slice computed tomography (CT) angiographic protocol could be used for diagnosis of PSS in dogs utilizing only patient sedation and without the need of test injection. Independent, blinded reviewers evaluated CT studies in a randomized order for study quality, shunt presence, number, and location of shunt origin and termination. Twenty two confirmed dogs were included in the study including 16 dogs with single extrahepatic congenital PSS, one dog with single intrahepatic congenital PSS, and two dogs with multiple acquired PSS. Three of the dogs (3/22) were surgically and histologically confirmed free of shunts. Final diagnosis was confirmed by surgery or necropsy. The new CT angiography protocol was shown to be diagnostic in dogs with PSS with no need for general anesthesia, test injections, delay times or timing determinations. Specificity and sensitivity were good (100%). The quality of the studies was considered good in the majority of cases (20/22). The amount of motion artifact in the CT scans was minimal, and had no effect on the diagnostic quality. The CT protocol was found to be a useful, fast, and accurate tool for diagnosing portosystemic shunts with a 16-slice system.