CT kidney volume may predict postsurgical renal function in cats

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A new feline study suggests preoperative CT may do more than define anatomy in hydronephrosis cases: it may also help predict renal function months after surgery. In the Journal of Small Animal Practice, Nagumo and colleagues reported that CT-derived renal parenchymal volume, particularly the contralateral kidney volume normalized to body weight, was strongly associated with long-term postoperative serum creatinine in cats without chronic kidney disease. The work points to CT volumetry as a potential prognostic tool when evaluating cats with hydronephrosis for surgery. (onlinelibrary.wiley.com)

That question matters because feline hydronephrosis and ureteral obstruction can be clinically deceptive. Cats with unilateral obstruction may maintain acceptable serum values for a time if the opposite kidney compensates, which means the functional status of the contralateral kidney can be more important than the appearance of the affected side alone. Reviews and clinical guidance on feline ureteral obstruction consistently emphasize assessment of both kidneys, and prior studies have shown that preoperative imaging findings from the contralateral kidney are associated with longer-term renal outcomes after intervention. (pmc.ncbi.nlm.nih.gov)

The new report builds on that background by focusing on renal parenchymal volume measured on CT. Earlier feline imaging work established that CT can estimate renal volume accurately, and CT-based morphologic assessment has been proposed as a useful way to characterize feline kidneys before intervention. In that context, the Nagumo study’s main contribution is not simply that kidney size matters, but that quantified parenchymal volume in the remaining functional kidney may carry predictive value for postoperative renal performance. (pubmed.ncbi.nlm.nih.gov)

The study was retrospective, and the abstract indicates the strongest relationship was seen in cats without pre-existing chronic kidney disease. Specifically, contralateral renal parenchymal volume normalized to body weight showed a strong negative correlation with postoperative serum creatinine concentration, suggesting that greater preserved parenchymal volume in the opposite kidney tracked with better long-term renal function after surgery. Based on the abstracted findings, the authors propose CT-based renal volume quantification as a way to predict postoperative kidney disease staging in selected cats. (onlinelibrary.wiley.com)

There does not appear to be broad published expert commentary on this paper yet, but the findings align with the direction of recent feline obstruction research. A 2024 study on unilateral ureteral obstruction found that ultrasonographic abnormalities in the contralateral kidney were associated with long-term serum creatinine and IRIS stage after treatment, while another study of long-term survivors reported that preoperative ultrasonographic parameters alone should be interpreted cautiously when predicting renal recovery. Taken together, the literature suggests clinicians are still looking for better prognostic markers, and CT volumetry may become one more piece of that puzzle rather than a standalone answer. (pmc.ncbi.nlm.nih.gov)

Why it matters: For veterinary professionals, the practical value here is in preoperative decision support. In referral settings where CT is already being used to define obstruction, evaluate anatomy, or plan intervention, renal parenchymal volumetry could potentially help refine prognosis without requiring a separate modality. That may be especially relevant when discussing whether a cat is likely to tolerate nephrectomy or how much renal reserve remains if decompression succeeds but the obstructed kidney contributes little long term. It could also improve conversations with pet parents about expected postoperative creatinine, CKD risk, and the likelihood of needing ongoing renal monitoring. (vin.com)

The study also highlights an important access issue. CT is less available and more resource-intensive than ultrasound, and some existing guidance notes that CT is not routinely necessary in many feline ureteral obstruction cases. So even if CT volumetry proves predictive, adoption may be concentrated in specialty practice unless simplified workflows or automated segmentation tools make measurement faster and more reproducible. (ivis.org)

What to watch: The next step is external validation: larger prospective studies, clearer subgroup data for cats with concurrent CKD, and comparisons between CT volumetry and ultrasound-based prognostic markers will determine whether this becomes a research signal or a practical planning tool in feline renal surgery. (pmc.ncbi.nlm.nih.gov)