Haematuria

Haematuria refers to the presence of blood in the urine. We distinguish between microscopic haematuria, when the concentration of blood is too low to be macroscopically visible, and macroscopic haematuria, where the concentration is so high that the urine is visible coloured red.

Haematuria may be a sign of kidney or urinary tract pathology, including glomerulonephritis, urinary tract infection, and bladder cancer. In many, however, haematuria is transient or no underlying pathology can be found.

Etiology

We distinguish two types of haematuria, glomerular haematuria and nonglomerular haematuria. Glomerular haematuria is secondary to glomerular disease. Nonglomerular haematuria is much more common.

• Glomerular haematuria - due to glomerulonephritis
  • Lupus nephritis
  • IgA nephropathy
  • Other glomerulonephritides
• Nonglomerular haematuria
  • Bladder cancer
  • Kidney cancer
  • Urinary tract infection
  • Urolithiasis
  • Benign prostatic hyperplasia

Classification

Macroscopic haematuria, also called macrohaematuria or gross haematuria, is the name of haematuria where the reddish colour change of the urine is visible to the naked eye. This is due to a high concentration of blood per unit urine.

Microscopic haematuria, also called microhaematuria, where the urine is mixed with so little blood that it cannot be seen macroscopically but it can be measured on biochemical tests.

Clinical features

Aside from severe haematuria being macroscopically visible, there are rarely any clinical features. Haematuria is rarely severe enough to cause anaemia. If due to glomerulonephritis, there may be oedema and hypertension, called nephritic syndrome.

Diagnosis and evaluation

The gold standard is microscopic evaluation of the urine, with 3 or more RBCs per high-power field usually being thought of as pathological. A urine dipstick test can also be used to semiquantitatively evaluate haematuria.

Glomerular and non-glomerular haematuria have some differing features. Glomerular haematuria usually has RBC casts in the urine, as well as dysmorphic RBCs in the urine. These dysmorphic RBCs have blebs on the surface and irregular morphology. In case of glomerular disease, there is often also concomitant proteinuria. RBC casts are absent for non-glomerular haematuria, and the RBCs in this type have normal morphology.

Other causes of bleeding, like menstruation and haemorrhoids, should be excluded. To rule out transient microhaematuria, microhaematuria should be confirmed with a second analysis after 1 month.

Because malignancy may be an underlying cause, patients with otherwise unexplained haematuria must be thoroughly evaluated for malignancy. The first step is usually to rule out bladder malignancy with cystoscopy.