Screening a living kidney donor for polycystic kidney disease using heavily T2-weighted MRI

Autosomal dominant polycystic kidney disease (ADPKD) accounts for approximately 8% of those awaiting renal transplantation. Living related kidney donors for these patients require screening for ADPKD, most commonly by ultrasonography. Ultrasound has a negative predictive value (NPV) of 100% in patients aged older than 30 years, but only 96% for donors aged 20 to 30 years. This case shows that heavily T2-weighted magnetic resonance imaging (HT2MRI) may be a more sensitive screening method for ADPKD in younger kidney donors. Despite a normal screening ultrasound result, a kidney donor with a family history of ADPKD was found to have renal cysts intraoperatively, and the transplantation was canceled. Afterward, the donor was imaged with HT2MRI. In addition, the mathematical relationship between sensitivity, specificity, and NPV for ADPKD screening tests was derived. After the canceled transplantation, a second ultrasound still could not identify renal cysts. However, HT2MRI showed multiple small ( approximately 3-mm) cysts in both kidneys and a 2.5-cm cyst on the right kidney. Mathematical analysis showed that the NPV of a screening test for ADPKD was most closely related to sensitivity and that only tests with 100% sensitivity would have a 100% NPV. We conclude that ultrasound is not a sufficiently sensitive screening test for ADPKD in younger living related renal donors. HT2MRI has improved sensitivity and may be the best screening test for ADPKD in this population.