Renal Volume Reduction on Magnetic Resonance Imaging During Tolvaptan Therapy in Patients with ADPKD: A Case Series

The primary effect of tolvaptan therapy in autosomal dominant polycystic kidney disease (ADPKD) is to slow the rate of kidney volume increase and thereby delay progression to end-stage renal disease; however, an actual reduction in kidney volume has rarely been reported. We evaluated four patients with ADPKD who demonstrated a decrease in kidney volume on magnetic resonance (MR) imaging during tolvaptan treatment. This observational case series included four patients who underwent regular clinical and MR evaluations between 2020 and 2025. The diagnosis was confirmed by radiological findings and/or genetic analysis. Total kidney volume was calculated as height-adjusted total kidney volume (htTKV), and renal function was assessed using the estimated glomerular filtration rate (eGFR) calculated by the CKD-EPI equation. The most pronounced reduction in kidney volume was observed in the patient with the highest baseline htTKV. In contrast, biochemical changes were limited, with minimal differences in eGFR ranging from -9 to 0 mL/min/1.73 m2. None of the patients had a history of additional medication use, dialysis, transplantation, or interventional procedures during follow-up. These findings suggest that a decrease in kidney volume may occur in some patients with ADPKD during tolvaptan therapy, highlighting the heterogeneity of treatment response and indicating that changes in kidney volume do not always parallel other clinical parameters. Larger studies are needed to better elucidate the variability in treatment response among patients.