Diagnosis of congenital portosystemic shunts (CPSS) in dogs remains challenging, despite advances in diagnostic imaging. Surgical correction is recommended for CPSS, but contraindicated in dogs with multiple acquired portosystemic shunts and hepatic microvascular dysplasia, which have presentations similar to CPSS. Patients presented for diagnosis of CPSS are typically small breed dogs less than two years of age. Clinical signs and biochemical abnormalities consistent with hepatic disease are common, placing these dogs at risk both during and after anesthesia and surgery. The ideal diagnostic tool should be sensitive for the presence, number and location of CPSS, but not require general anesthesia. This prospective clinical study is designed to evaluate a novel scintigraphic imaging tool for diagnosis of CPSS in dogs. Trans-splenic portal scintigraphy (TSPS) is a minimally invasive technique performed under light sedation that clearly delineates the portal system with a substantially lower dose of radioisotope than other scintigraphic techniques. This allows for early clearance, increased staff safety and better patient care. Results will be compared with surgical findings to determine accuracy of both techniques in detecting the presence, number and location of shunts.