Predictive utility of computed tomography‐derived renal parenchymal volume for long‐term postoperative renal function in cats with hydronephrosis

OBJECTIVES: To evaluate the utility of preoperative feline renal parenchymal volume derived from computed tomography in predicting the serum creatinine concentration during the long-term postoperative period. MATERIALS AND METHODS: In this retrospective clinical study, we included 13 client-owned cats with normal kidneys and 24 cats with hydronephrosis (16 with chronic kidney disease and 8 without chronic kidney disease). The renal parenchymal volume was derived from CT images and normalised to the body weight. The reference intervals for renal parenchymal volume/body weight and total renal parenchymal volume/body weight were calculated from the control group. We performed between-group comparisons of the preoperative hydronephrotic renal parenchymal volume, contralateral renal parenchymal volume and total renal parenchymal volume/body weight; additionally, we analysed the relationships among hydronephrotic renal parenchymal volume/body weight, contralateral renal parenchymal volume/body weight, total renal parenchymal volume /body weight and serum creatinine concentration during the preoperative and long-term postoperative periods (>3 months). The long-term postoperative chronic kidney disease stages were classified based on the International Renal Interest Society guidelines. RESULTS: The non-chronic kidney disease subgroup had a significantly greater hydronephrotic renal parenchymal volume/body weight than the control group. The non-chronic kidney disease subgroup had a significantly greater contralateral renal parenchymal volume/body weight than the control group and the chronic kidney disease subgroup. In the non-chronic kidney disease subgroup, contralateral renal parenchymal volume/body weight showed a strong negative relationship with postoperative serum creatinine concentration (r = -0.79). In the hydronephrosis group, total renal parenchymal volume /body weight showed a moderate negative correlation with postoperative serum creatinine concentration (r = -0.46). In the non-chronic kidney disease subgroup, contralateral renal parenchymal volume/body weight was significantly greater in International Renal Interest Society stages I-II than in International Renal Interest Society stages III-IV. CLINICAL SIGNIFICANCE: The preoperative contralateral renal parenchymal volume/body weight in non-chronic kidney disease cats with hydronephrosis is associated with the long-term postoperative serum creatinine concentration. CT-based quantification of renal parenchymal volume may be useful for predicting postoperative chronic kidney disease staging based on serum creatinine concentration in cats with hydronephrosis.