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Lab test update - microscopic haematuria

Chemical pathologist Dr Stuart Smellie and urologist Mr Carl Roberts discuss how best to manage a patient who has been found to have microscopic haematuria on a routine medical

Chemical pathologist Dr Stuart Smellie and urologist Mr Carl Roberts discuss how best to manage a patient who has been found to have microscopic haematuria on a routine medical

How accurate are dipstick tests for haematuria and what should the GP's initial action be?

41213603First, despite how often we test urine for blood and protein, there is no absolute answer to investigating asymptomatic microscopic haematuria in younger patients, so what follows is simply our opinion based on a review of the literature we did last year.

Urine dipsticks are a pretty accurate test for abnormal levels of red cells in urine and may partly distinguish erythrocytes from free haemoglobin – dots versus uniform colour. But this is only a guide and with a high blood content the strip may appear uniformly coloured.

The first thing to do if there is nothing to suggest muscle disease or haemolysis is to repeat it – and I would send a fresh urine sample to the lab for microscopy confirmation. The same test will identify bacteriuria and other cells.

In the absence of symptoms, conditions such as UTI and kidney stones are less likely, although it is important to exclude intrinsic kidney disease and haemolysis before going on to consider investigating the renal tract for possible tumours.

Obviously benign prostatic hyperplasia can cause haematuria, but we would expect him to have some symptoms. Think also about testicular or epididymal lesions.

There is little evidence on how the different semi-quantitative ‘levels' of microscopic haematuria should be investigated.

Macroscopic haematuria is a clearly recognised indication for urological investigation in the absence of an obvious cause. Common sense might suggest that three pluses on a dipstick, suggesting microscopic haematuria, is likely to be more clinically relevant than just one plus and should lower the threshold to investigate in the lower risk and younger patients. The higher risk patients and those over 50 will be investigated anyway.

What further tests would be recommended in a case such as this?

The lab microscopy test should confirm if red blood cells are present and whether there are any pathological cell casts or other indicators of kidney disease. The directions of investigations will then depend on the microscopy.

If intrinsic kidney disease is not suggested, and exercise (and menstruation in women)have been excluded as causes, then bladder tumours are the main concern here. But both ends of the renal tract need to be examined, using imaging (probably ultrasound, according to our radiologist) for the upper tract and cystoscopy for lower.

Free haemoglobin suggests haemolysis, which is investigated separately – haptoglobin, blood film and lactate dehydrogenase – and at a time when so many people are on statins it would be wise to consider asymptomatic myopathy, although this is very rare.

I would do a basic lab assessment before imaging, including renal function and a liver profile (for albumin and bilirubin). I would add an AST as this is often raised in asymptomatic renal cell carcinoma (a diagnosis always worth remembering), creatine kinase and an FBC with ESR (or viscosity) as indicators of renal, muscle and systemic inflammatory disease. Add in tests for haemolysis if this is suspected from the blood count. If the urine microscopy suggests renal disease I would add auto-antibodies pending an outpatient appointment.

Can we do any investigations to help in the decision whether to refer the patient to a urologist or nephrologist?

41213601To some extent. Unexplained microscopic haematuria in a patient over 50 or in younger patients with risk factors for bladder cancer should be referred urgently to a urologist if these tests do not otherwise suggest intrinsic renal disease or other non-urological causes.

Discuss the imaging required with your local radiologist, but it will probably be a kidney-ureter-bladder (KUB) plain abdominal radiograph and ultrasound to start with – although our haematuria clinic will do this in a ‘one-stop' visit. Send a fresh urine microscopy sample to the lab.

The 2007 Health Technology Assessment on microscopic haematuria concluded that sound evidence supporting any specific diagnostic pathways was lacking and questioned the utility of cytology in younger or lower risk patients.

The American Urological Association recommends full urological examination of patients over 40 – or younger with risk factors – with incidental asymptomatic microscopic haematuria.

Our reading of the guidelines suggests urine cytology would probably be worthwhile in this patient, as it would be informative if positive. He is well over 40 and the lab test did show quite heavy haematuria.

But if the other tests do not suggest a non-urological cause, I would still refer him to a urologist regardless of the cytology result.

Microscopic haematuria is sometimes attributed to patients being on anticoagulants – especially warfarin. Is this correct, dependent on the INR or simply wrong? Is aspirin ever relevant?

Patients on aspirin and warfarin may be more prone to bleeding, but it would be very unwise to write off macro- or microscopic haematuria as just being caused by one of these before excluding other possibilities. People on aspirin or warfarin also develop bladder tumours. They are not that rare and are eminently treatable if detected early.

If no cause is found, how should future positive urinalyses be managed?

If urinary tract investigations are negative, observation with repeat tests every six to 12 months, monitoring for any symptoms, would be reasonable.

Mr Carl Roberts is consultant urologist and Dr Stuart Smellie is consultant chemical pathologist at Bishop Auckland Hospital, County Durham

Competing interests: none declared

For more information on the use of lab tests in primary care go to which has 120 clinical scenarios for general practice

Bladder Ca risk factors Urine dipsticks are fairly accurate for detecting red cells in urine Urine dipsticks are fairly accurate for detecting red cells in urine The case

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