Blood In Urine - What is the Connection with Chronic Kidney Disease?

Hematuria is defined as blood in the urine. The most common causes of blood in the urine are stones or bladder infections. Microscopic hematuria is commonly defined as the presence of three or more RBCs per high-power field in a spun urine sediment. The question is whether microscopic hematuria that persists over time is linked to kidney disease.

In a retrospective cohort study published in the American Journal of Kidney Diseases, researchers examined data for 232,220 Korean adults who did not have Chronic Kidney Disease (CKD) at baseline. They specifically looked at whether persistent or one-time episodes of microscopic hematuria and the development of CKD.

The researchers did measurements of hematuria on 2 occasions, 1.7 years apart. They categorized participants into 4 groups:

1. no hematuria at both examinations (reference group)

2. hematuria followed by no hematuria (regressed hematuria group)

3. no hematuria followed by hematuria (developed hematuria group)

4. hematuria at both examinations (persistent hematuria)

The study had a 4.8-year median follow-up. During this time, 2,392 participants developed CKD. Looking at the data, the hazard ratio for developing CKD was as follows in the 3 groups:

1. HR 1.85 for the regressed group (hematuria followed by no hematuria)

2. HR 3.18 for the developed group (no hematuria followed by hematuria)

3. HR 5.23 for the persistent group (hematuria at both examinations)

Interestingly, the association of CKD was stronger in men than women. This raises the importance of always following up with your doctor if you have hematuria.

Reference: Um YJ, et al. Am J Kidney Dis. 2022;doi:10.1053/j.ajkd.2022.09.012