Computed tomographic measures of renomegaly vary among dogs with different types of congenital portosystemic shunts

Renomegaly has been reported in dogs with congenital portosystemic shunts (PSS). However, no study has objectively evaluated the degree of renomegaly in dogs with different types of PSS. The purpose of this retrospective, analytical, cross-sectional study was to determine kidney size (renal length-to-L2 vertebral body ratio; RL/L2 ratio) using CT in dogs with different types of PSS and correlate with clinical information. A medical record search for dogs with a PSS diagnosed using CT between 2016 and 2020 was conducted. Breed, age, sex, body weight, and biochemistry results were recorded. Kidney and L2 vertebral body lengths were measured using multiplanar reformatted CT images, and the RL/L2 ratio was calculated. Dogs were categorized into four groups based on PSS morphology for comparisons: intrahepatic (IH; n = 19), extrahepatic portocaval (EHPC; n = 20), extrahepatic portoazygos (EHPA; n = 7), or extrahepatic portophrenic (EHPP, n = 7). The RL/L2 ratio (mean +/- SD) was largest in IH (3.55 +/- 0.38) and EHPC (3.55 +/- 0.38), followed by EHPP (3.10 +/- 0.23), and EHPA (2.78 +/- 0.18). RL/L2 ratio was significantly larger in EHPC and IH (vs. EHPA and EHPP [P < .01]). Significant correlations between kidney size and creatinine, alkaline phosphatase, albumin, total protein, and ammonia were present. Renomegaly was observed in 86.8% of dogs with PSS overall, but it was uncommon in dogs with EHPA and less common in dogs with EHPP, as these two groups showed clinical signs later in life, made evident by older age at presentation. The authors suggest that the severity of hepatic dysfunction and the shunted blood volume may influence the development of renomegaly in dogs with PSS.