Blood in the Urine: That JAMA Study
Back in August a publication in JAMA (Journal of the American Medical Association) made the news. Vivante et al examined the risk of end-stage kidney failure in Israeli military recruits with and without isolated asymptomatic microscopic hematuria twenty years after screening.
What is this diagnosis?
Isolated: Hematuria was the only abnormality identified; no proteinuria, high blood pressure, or abnormal kidney function
Asymptomatic: The subject had no complaints
Microscopic: The urine never looked bloody; blood cells could only be detected by dipstick or microscopic examination
Hematuria: At least 5 red blood cells in every high power field of urine examined.
In addition, patients have undergone studies to rule-out malformations or disorders that may produce blood in the urine
What is the study?
The screening scheme for the study is shown in the figure. Well over one million Israeli military recruits had screening physicals with urinalysis prior to military conscription. Of these, 96.9% had no evidence of kidney problems or disorders that might lead to kidney failure (controls). Another 2.8% had chronic diseases that could produce kidney failure or damage. Only 3,690 individuals met the criteria for isolated asymptomatic microscopic hematuria (0.3% of overall population). Twice as many hematuria patients were male as female.
After 20 years, the risk of kidney failure requiring dialysis or transplant was 2.05 per 100,000 person-years in the control group. The hematuria patients risk was increased to 34.0. Diabetes was the most common cause of kidney failure in controls; a variety of glomerular disorders presented in the hematuria group.
What does this mean?
Only 0.7% of asymptomatic microscopic hematuria subjects required kidney failure treatment after 20 years of follow-up, even though this is substantially higher than individuals with no evidence of kidney problems at screening (0.04%). Children with this degree of hematuria should know their long-term prognosis is generally good.
The results of this study may not be applicable to children who are not Israeli Jews. Other ethnic groups may show different risk with this condition. Also, screening and work-up tests have changed over time. Today we screen affected children for a number of disorders that would not have been tested in the 1970s. Since longitudinal data on development of other signs and symptoms are not available, it is not clear how these tests might alter the results.
The study is strong because of the large numbers initially enrolled and the linkage with the end-stage kidney failure database of the country.
The bottom line: people with isolated asymptomatic microscopic hematuria should have periodic monitoring of urinalysis and other measures of kidney function because they do have an increased risk of kidney failure when compared with the general population.