Renomegaly severity and prevalence differ by shunt type and inversely correlate with CT-assessed portal perfusion in cats with extrahepatic portosystemic shunt

This retrospective study evaluated 83 cats with a single extrahepatic portosystemic shunt (PSS)—Portocaval (n=1), Left gastroazygos (n=2), Left gastrocaval (n=9), Left gastrophrenic (n=24), and Splenosystemic (n=47)—to evaluate whether the prevalence and severity of renomegaly in cats with extrahepatic PSS differ by shunt type, and to assess associations with computed tomography (CT)-based portal perfusion, and serum biochemical parameters. Renal size was quantified using the kidney length-to-the second lumbar vertebral length ratio (K/L2 ratio), and portal perfusion by the portal vein diameter-to-aortic diameter ratio (PV/Ao ratio). These indices were compared between shunt types and correlated with biochemical parameters. The Left gastrocaval group showed the highest mean K/L2 ratio (2.88 ± 0.24) and 100% prevalence of renomegaly, compared to the Left gastrophrenic (2.39 ± 0.23; 37.5%) and Splenosystemic groups (2.21 ± 0.16; 12.8%). Conversely, the median PV/Ao ratio was the lowest in the Left gastrocaval group (0.56 [0.47–0.61]), intermediate in the Left gastrophrenic group (0.89 [0.60–0.95]), and highest in the Splenosystemic group (1.12 [0.90–1.15]), indicating varied severity of portal hypoperfusion. Renal size and portal perfusion showed a significant inverse correlation (r_s= −0.521, P<0.001). Renomegaly was also associated with higher ammonia and lower blood urea nitrogen, and creatinine concentrations. In conclusion, renomegaly severity is inversely correlated with portal perfusion and varies significantly among shunt types. These findings, combined with associations with hepatic dysfunction markers, suggest that renomegaly may serve as a clinically relevant indicator of disease severity in cats with extrahepatic PSS.