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 (rs=–0.521, P