Isolated microhematuria in potential kidney donors: evaluating kidney biopsy findings with dipstick urinalysis and urine microscopy results.

Background: Isolated microhematuria (IMH) can signal hidden glomerular disease, necessitating detailed evaluations for potential kidney donors, including kidney biopsies. The optimal strategy for deciding on kidney biopsies remains unclear. While the British Transplant Society supports dipstick analysis, KDIGO focuses solely on urine microscopy. This study explored the correlation between kidney biopsy outcomes and results from dipstick urinalysis and urine microscopy in potential kidney donors.

Methods: This retrospective study encompassed all potential kidney donors who received kidney biopsies following a positive urine dipstick result for IMH, irrespective of whether red blood cells (RBCs) were found on urine microscopy. We performed sensitivity and specificity analyses to assess the effectiveness of microscopy and dipstick urinalysis in identifying histological abnormalities in the kidney biopsies.

Results: Approximately 49% of potential donors-133 out of 271-who had kidney biopsies due to positive dipstick tests showed negative results in urine microscopy for RBCs. In total, 168 donor candidates, or 62%, had abnormal findings in their biopsies, with nearly half of those diagnosed with immunoglobulin A nephropathy having negative urine microscopy results. Furthermore, 58% of potential donors with negative urine microscopy results-77 out of 133-also exhibited abnormal biopsy findings. The urine microscopy test displayed a sensitivity of 54.2% (95% confidence interval 46.6-61.5) and a specificity of 54.4% (95% confidence interval 44.8-63.7) for detecting abnormal biopsy results.

Conclusion: This study highlighted a significant presence of donors with IMH with underlying glomerular lesions. Using urine microscopy showed limited sensitivity and specificity in identifying abnormal histopathological results. Relying solely on urine microscopy may miss critical pathologies like IgAN in prospective kidney donors. The persistence of IMH during dipstick urinalysis calls for kidney biopsy in potential donors. These findings suggest that our results be incorporated into future global guideline formulations.