Asymptomatic isolated microscopic haematuria: long-term follow-up.
BACKGROUND
Evidence to support current diagnostic and management approaches to asymptomatic haematuria is lacking and based on short-term clinical observation.


AIM
To ascertain the natural history and long-term outcome of asymptomatic and isolated haematuria, and to determine the clinical correlates of adverse renal events.


DESIGN
Prospective observational referral-based study.


METHODS
We evaluated 90 consecutive patients with isolated microscopic haematuria, first seen between 1985 and 1996 at an out-patient nephrology clinic. We defined adverse renal events as the development of proteinuria (> 0.5 g/24 h) on two consecutive occasions, development of hypertension, or impaired renal function characterized by glomerular filtration rate (GFR) of <60 ml/min/1.73 m(2) for 3 months or more.


RESULTS
There were 24 males and 66 females, median follow-up 5.2 years (total 442 patient-years). Mean age at presentation was 39 +/- 13 years. Fifteen (17%) had complete resolution of microscopic haematuria. One (1%) had transitional cell carcinoma of urinary bladder 20 months after initial presentation. Twelve (13%) developed hypertension, and 10 (11%) proteinuria. Only one developed chronic renal failure, 2.3 years after initial presentation. Altogether, 16 (19%) developed at least one adverse event, after a mean 42 months. Neither history of renal biopsy nor histological diagnosis of glomerular disease was predictive of renal events. Three independent variables were predictive of adverse renal events: baseline proteinuria (RR per 0.1 g/day 2.04; 95%CI 1.13-3.68; p = 0.018); MDRD-estimated GFR at presentation (RR per 10 ml/min/1.73 m(2) decrement 2.01; 95%CI 1.09-3.71; p = 0.025); and baseline serum urate (RR per 100 micromol/l 1.02; 95%CI 1.01-1.03; p = 0.009).


DISCUSSION
Asymptomatic microscopic haematuria can lead to adverse renal events, and warrants nephrologist evaluation and regular follow-up. Its isolated microscopic haematuria is closely related to early hints of chronic kidney disease, such as low-grade proteinuria and renal insufficiency, as well as hyperuricaemia.