Merck Manual

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Asymptomatic Proteinuria and Hematuria


Frank O'Brien

, MD, Washington University in St. Louis

Reviewed/Revised Aug 2023

Asymptomatic proteinuria and hematuria syndrome is the result of diseases of glomeruli (clusters of microscopic blood vessels in the kidneys that have small pores through which blood is filtered). It is characterized by steady or intermittent loss of small amounts of protein and blood in the urine.

Small amounts of protein excreted in the urine (proteinuria) or blood excreted in the urine (hematuria Blood in Urine Blood in the urine (hematuria) can make urine appear pink, red, or brown, depending on the amount of blood, how long it has been in the urine, and how acidic the urine is. An amount of blood... read more ) are sometimes discovered in people without symptoms when urine tests are done for some routine purpose. The presence of clumps of red blood cells (red blood cell casts) or abnormally shaped red blood cells is a clue for doctors that the blood in the urine came from glomeruli. Casts and proteinuria may be present because the person is recovering from a recent undiagnosed episode of kidney inflammation (nephritis Glomerulonephritis Glomerulonephritis is a disorder of glomeruli (clusters of microscopic blood vessels in the kidneys with small pores through which blood is filtered). It is characterized by body tissue swelling... read more ). If this situation seems likely, a doctor needs only to recheck the person over the next weeks or months to make sure that the abnormalities resolve.

If red blood cells (particularly casts) and proteinuria persist, the cause is usually one of 3 disorders:

Thin basement membrane disease tends to cause red blood cells in the urine, but causes excretion of smaller amounts of protein than IgA nephropathy or Alport syndrome and may not cause excretion of red blood cell casts. This disorder follows a mild and nonprogressive course. The diagnosis can usually be made with a kidney biopsy Tissue and Cell Sampling Site-specific biopsies and cell sampling are also used in the evaluation of people with suspected kidney and urinary tract disorders. (See also Overview of the Urinary Tract.) A kidney biopsy... read more . However, a kidney biopsy is rarely done because the likelihood of finding a treatable disease is very low.

Doctors usually recommend that people with asymptomatic proteinuria and hematuria have a physical examination and undergo urine testing once or twice a year. Additional tests are done if the amount of protein or blood increases much, or if symptoms occur that suggest the development of a specific disease. Most people with asymptomatic proteinuria and hematuria syndrome do not worsen, and the condition may persist indefinitely.

More Information

The following English-language resources may be useful. Please note that THE MANUAL is not responsible for the content of these resources.

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