Clinical Significance of Renal Allograft Urothelial Thickening Identified by Ultrasound

Objectives To assess the etiology and clinical implications of ultrasound (US)-diagnosed urothelial thickening (UT) in renal transplants. Methods Patients with renal transplants who had UT diagnosed by US from January 2000 to December 2018 were retrospectively identified and compared to patients with transplants without UT scanned during the study period. Medical records were reviewed for demographics, US findings, pathologic results, laboratory values, and clinical outcomes and compared between groups by Fisher exact and t tests. Results A total of 143 patients with UT and 128 controls comprised our cohorts. The patient age in the UT group versus controls (mean ± SD, 50.2 ± 16.5 versus 51.2 ± 15.3 years) and the time since transplant (2.9 ± 4.2 versus 2.4 ± 5.8 years) were similar. Patients with UT were more likely to be female than controls (76 of 143 [53.1%] versus 53 of 128 [41.4%]; P = .07), but the difference was not statistically significant, and patients with UT were more likely to have indwelling stents (31 of 143 [21.7%] versus 9 of 128 [7.0%]; P = .001) and hydronephrosis (25 of 143 [17.4%] versus 11 of 128 [8.6%]; P = .03). At biopsy, rejection and vascular sclerosis were more likely in patients with UT compared to controls (24 of 25 [49.0%] versus 11 of 43 [25.6%]; P = .031; 42 of 49 [85.7%] versus 22 of 43 [51.2%]; P = .0005, respectively), whereas acute tubular necrosis was similar. The sensitivity (50.0%) and specificity (74.4%) of UT for rejection were low. Conclusions Urothelial thickening correlates with US findings of urinary obstruction and indwelling stents, suggesting a possible mechanical component to UT's etiology. Although transplant rejection and vascular sclerosis were more frequent at biopsy in the UT group than controls, UT had low sensitivity and specificity for rejection.