Postattenuation neurologic signs (PANS) are serious complications following surgical ligation of congenital portosystemic shunts (cPSS) in dogs, but their pathogenesis remains incompletely understood. We hypothesized that surgical ligation alters hepatic tryptophan metabolism through increased substrate delivery and inflammation, leading to changes in kynurenine pathway metabolites that may contribute to PANS. Ten dogs diagnosed with cPSS between April 2019 and December 2023 underwent surgical ligation. Serum samples were collected preoperatively and on postoperative days 1, 2, and 3. Serum concentrations of quinolinic acid (QA) and 3-hydroxykynurenine (3OHKYN) were measured using ELISA in this retrospective observational study. Dogs exhibiting neurological signs within 3 days postoperatively were classified as having PANS. Serum QA concentrations showed no significant postoperative changes and did not differ between dogs with and without PANS. In contrast, serum 3OHKYN concentrations decreased significantly after surgery (p = 0.002). Dogs that developed PANS had significantly lower serum 3OHKYN concentrations on postoperative day 1 (p = 0.048) and exhibited greater reductions from baseline on postoperative days 1 and 3 (p = 0.024 and 0.017, respectively). These preliminary findings suggest that postoperative reductions in 3OHKYN, rather than increases in QA, are associated with PANS development, indicating that altered tryptophan metabolism may play a role in its pathogenesis and warrant further investigation in larger studies.
