It is often caused by inherited thinning of the glomerular membrane

Haematuria is often detected incidentally by “dipstick” tests in clinical practice, and much recent discussion in the BMJ has centred round whether haematuria in asymptomatic individuals should always be investigated or whether it can be disregarded. 1 2 Certainly haematuria can sometimes be dismissed as due to contamination with menstrual blood or to a urinary tract infection, but in other cases, as one correspondent chided, why do the test if you are going to ignore the result?

In most cases of dipstick haematuria the next step should be to examine the urine by phase contrast microscopy to confirm the haematuria and determine whether the red cells have originated from the glomerulus or elsewhere in the urinary tract.3 “Dysmorphic” or “glomerular” red cells are present when there is glomerulonephritis with proliferative features and “non-glomerular” red cells when bleeding is from elsewhere in the urinary tract, usually resulting from infections, stones, a tumour, or contamination. Finding haematuria without proteinuria cannot be used to infer a non-glomerular origin since glomerular bleeding is not necessarily accompanied by proteinuria.3

What is the usual source of haematuria in asymptomatic individuals? The …