(See also Overview of Kidney Filtering Disorders Overview of Kidney Filtering Disorders Each kidney contains about 1 million filtering units (glomeruli). The glomeruli are made up of many microscopic clusters of tiny blood vessels (capillaries) with small pores. These blood vessels... read more .)
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:
Immunoglobulin A (IgA) nephropathy, a type of glomerulonephritis 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 caused by deposition of immune complexes (combinations of antibodies and antigens) in the kidneys that can be very mild and nonprogressive or become a severe disease leading to kidney failure (loss of most kidney function).
Alport syndrome Alport Syndrome Alport syndrome is a hereditary (genetic) disorder that results in glomerulonephritis in which kidney function is poor, blood is present in the urine, and deafness and eye abnormalities sometimes... read more , a progressive hereditary glomerular disorder that can be severe and lead to kidney failure and decreased hearing and vision.
Thin basement membrane disease (benign familial hematuria), a hereditary disorder caused by thinning of a part of the glomerulus called the basement membrane.
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.
The following English-language resources may be useful. Please note that THE MANUAL is not responsible for the content of these resources.
American Kidney Fund, Proteinuria: Information and infographics on protein in the urine, including the connection between this symptom and chronic kidney disease
American Kidney Fund, IgA Nephropathy: General information on IgA nephropathy, including answers to frequently asked questions
American Kidney Fund, Blood in Urine (Hematuria): Information on blood in the urine, including the connection between this symptom and serious kidney disease