is the most important cause of proteinuria, and in some cases the discovery of proteinuria may be the first evidence of such disease. Almost any form of kidney disease will cause proteinuria, but the most frequent form to do this is glomerulonephritis (see under KIDNEYS, DISEASES OF). In the subacute (or nephrotic) stage of glomerulonephritis, the most marked proteinuria of all may be found. Proteinuria is also found in infections of the kidney (pyelitis) as well as in infections of the bladder (cystitis) and of the urethra (urethritis).

The development of proteinuria in pregnancy requires investigation, as it may be the first sign of toxaemia of pregnancy (see PRE-ECLAMPSIA and ECLAMPSIA). Proteinuria may also result from the contamination of urine with vaginal secretions. (See also PREGNANCY AND LABOUR.)

are commonly accompanied by proteinuria, particularly when the right side of the heart is failing. In severe cases of failure, accompanied by OEDEMA, the proteinuria may be marked. (See also HEART, DISEASES OF.)

often causes proteinuria, even though there is no actual kidney disease. The proteinuria disappears soon after the temperature becomes normal. (See also PYREXIA.)

These include arsenic, lead, mercury, gold, salicylic acid and quinine.

This type is present only when the person is upright, so is not usually present in the first urine sample collected on waking. It is important because, if its true cause is unrecognised, it may be wrongly taken as a sign of kidney disease.