Microscopic haematuria (microhaematuria) is the presence of unseen but significantly high numbers of red blood cells in the urine. It is normal for urine to have very small amounts of blood (< 3 red blood cells per high power field). However if it exceeds 3 red cells, and remains high on repeat testing, it may indicate a kidney disease or some tumour growth in the urinary system.
Many people have microhaematuria for many years and yet do not have kidney or urinary tract disease. In fact, many seem to be related to physical exercise or vigorous sports (stress microhaematuria) or hypertension. However, before concluding that such persistent microhaematuria is benign in nature, it is important to exclude any significant urological disease. In order of importance, they are:
- tumours and cancers in kidney or bladder [Fig 1]
- kidney parenchymal disease (glomerulonephritis) [Fig 2]
- urinary stones [Fig 3]
- prostate inflammation (prostatitis) in men
- urethra inflammation (urethritis) in women
Fig 1. Kidney and bladder cancer as a cause for microhaematuria
Fig 2. Glomerular disease causes blood to leak into the urine
Fig 3. Urinary stones cause the urinary tract lining to bleed
Microhaematuria can only be regarded as idiopathic after the following investigations have been done:
- urine tests e.g. phase contrast study to determine if the blood is from glomerular disease or urinary tract lining, urine cytology to look for cancers of the urinary tract lining
- radiologic scans, e.g. xray, Ultrasound, IVU or CT scan
- endoscopy, eg. flexible cystoscopy [Fig 4] which is easily done under local anaesthesia and regarded as the most reliable way of seeing any small tumours / cancer in the bladder. Cystoscopy can also determine if the prostate is the likely source of bleed
Fig 4. Flexible cystoscopy can easily be done under local anaesthesia
Microhematuria can be an absolutely harmless occurrence or indicate a serious disease. Even if no apparent cause is found after extensive investigations, it is recommended that urine analysis be done at least once a year. This is because kidney stones ay initially be so small that the ultrasound or xray may not show it. Glomerular disease of the kidney may also not manifest in the initial years.