Cancers of the kidney and bladder kill nearly as many people in the UK as breast cancer yet they have nothing like its profile, and the cardinal sign of trouble – blood in the urine – isn’t always taken as seriously as it should be.

Obvious blood in the urine (haematuria) should never be ignored and always warrants further investigation, but there still seems to be some confusion as to what to do with people with traces which are invisible to the naked eye and only detected on testing with a dipstick. And this microscopic haematuria is a common finding, occurring in as many as 1 in 20 healthy individuals tested during medicals such as those done routinely for life insurance and licences / certification to race, fly or dive.

The National Institute for Health and Care Excellence (NICE) has issued guidance on how to manage microscopic haematuria but in my experience it is often ignored. The latest reminder that it is a potentially worrying finding comes from a study into whether invisible blood suggests an underlying cancer. In what the team describe as “the first robust study” into the link, researchers from the University of Exeter Medical School have just published findings showing that people over sixty testing positive for blood on dipstick have a 1 in 60 chance of having bladder cancer.

Of course that means 59 out of every 60 don’t – and that pick up rate will be much lower in younger patients – but even so it warrants further investigation irrespective of age. Causes range from cystitis to kidney disease, but if no obvious cause can be found microscopic haematuria should prompt referral to a specialist, and as matter of some urgency in patients over-50 who are more likely to have cancer of the kidney or bladder.

Obvious blood in the urine is a much easier problem to manage. It can occur normally with some infections of the urinary tract – other tell tale signs of which include needing to pee more often and stinging when you do – but if it is painless it should immediately raise a red flag and the patient be referred urgently.

Although bladder and kidney cancer are more common in the elderly they can strike much earlier as I have learned to my cost. My father-in-law died from kidney cancer when he was 79, but I have also lost two of my friends to the disease, one of whom was younger than me, so it now features prominently on my radar. And kidney cancer is on the increase with rates doubling in the UK over the last 40 years.

White middle-aged and elderly men are most at risk of kidney and bladder cancer. One in twenty-five men will develop one or other at some stage of their life, compared to around 1 in 50 women. Smoking remains the most important cause of both and the risk continues for some time after giving up (up to 20 years later in the case of bladder cancer), but obesity and high blood pressure are two other all too common risk factors for kidney cancer.

As with nearly all cancers the survival rates are much better if the disease is caught early, but if blood in the urine is missed or ignored then the diagnosis is often delayed complicating treatment and worsening the prognosis. Overall survival rates for both cancers are just over 50% (compared to 85% for breast cancer) and they kill around 10,000 people every year in the UK.

NICE currently advises against general screening using dipsticks to test for invisible blood in the urine because pick-up rate for underling disease is so low, but that doesn’t mean a positive test should be dismissed even if it is just part of an insurance medical. In most cases there will be a simple explanation, but for a small minority invisible blood can be the first sign of a serious problem. Don’t ignore it.

For more details on the Exeter study visit www.exeter.ac.uk/news/featurednews/title_408171_en.html

• Painless blood in your urine always requires urgent specialist referral
• If the blood is accompanied by pain, and causes like kidney stones or infection suspected, then these must be confirmed with further testing. If the results comes back as negative then the patient should be referred for a specialist opinion to rule out other problems
• And persistent infections associated with bleeding in patients over 40 require urgent investigation too
• Visit nice.org.uk for the full guidance on haematuria