Proteinuria
Proteinuria, also known as albuminuria, is a medical condition characterized by the excessive excretion of protein in the urine, typically defined as more than 150 milligrams of protein per day. This condition can arise from various causes, including dehydration, acute illness, pregnancy-induced hypertension, diabetes, and damage to the kidneys' filtering units, known as glomeruli. Initial symptoms may be subtle, often presenting as foamy urine, while more advanced stages can lead to edema, or swelling, in the hands, feet, and abdomen due to fluid accumulation.
Diagnosis is typically made through urine testing, which may include measuring the urine albumin-to-creatinine ratio. Chronic proteinuria can indicate underlying kidney disease and necessitates further kidney function tests. Treatment focuses on managing the root causes, often involving dietary changes and medications such as antihypertensives or diuretics. Individuals with diabetes, hypertension, and certain ethnic backgrounds may be at an increased risk for this condition. Understanding proteinuria is crucial, as it has historical significance dating back to ancient medical literature, highlighting its association with kidney health.
Proteinuria
ALSO KNOWN AS: Albuminuria
ANATOMY OR SYSTEM AFFECTED: Kidneys, urinary system
DEFINITION: Disorder involving the elimination of abnormally high amounts of protein in the urine; typically defined as the excretion of more than 150 milligrams of protein in the urine per day
CAUSES: Dehydration, fever, inflammatory process, medications, pregnancy-induced hypertension, hypertension, diabetes, glomerular disease
SYMPTOMS: Foamy urine earlier in disease; edema in hands, feet, abdomen later in disease
DURATION: Acute or chronic
TREATMENTS: Medication (antihypertensives), treatment of underlying disorders
Causes and Symptoms
Proteinuria is a disorder that does not have a unique cause. The excretion of abnormally high amounts of protein in the urine can have a number of benign causes, in which case the disorder is likely transient. These causes include dehydration, acute illness, and overexertion. In other instances, proteinuria is the result of a problem within the kidneys. This type of proteinuria is more severe, as well as chronic. Proteins play an important function in the body and are routinely carried in the bloodstream. Since proteins are large molecules, they are not routinely filtered out by the into the urine. When the glomeruli (the filtering mechanisms within the kidneys) are damaged for any reason, these large protein molecules do pass through the filters and into the urine to be eliminated.
Proteinuria has no symptoms early in its course. One of the earliest signs of proteinuria is the foamy appearance of urine in the toilet. This foamy appearance is caused by the abnormally high amount of protein. As the disorder progresses, the symptoms progress to the development of edema (an accumulation of fluid causing swelling). As a result of the loss of protein from the bloodstream, less is carried in the bloodstream, with more remaining in the tissues. As a result, appears in the hands and/or the feet and in the abdominal area.
People who have both types of diabetes, hypertension, and people of certain ethnic backgrounds are at a higher risk for proteinuria.
Treatment and Therapy
The diagnosis of proteinuria is made based on the collection of urine samples. In the past, it required the collection of a twenty-four-hour urine specimen, with the diagnosis of proteinuria being made if more than 150 milligrams of protein were excreted per day. More recently, the diagnosis of proteinuria has been made based on one urine by determining a urine albumin (protein) to (waste product) ratio. More than 30 milligrams of albumin per milligram of creatinine is indicative of proteinuria. Whenever proteinuria is present, additional tests of kidney function are indicated. Chronic proteinuria is often indicative of chronic kidney disease.
Treatment of proteinuria is dependent on treating the underlying problem. Dietary modifications may be made to control glucose, sodium, and protein intake. Medications may be used to treat diabetes and hypertension. The most commonly used medications are angiotensin-converting enzyme (ACE) inhibitors. Diuretics may be used as well in order to help the kidneys eliminate excess fluid.
Perspective and Prospects
Proteinuria was first alluded to, although unnamed, by Hippocrates around 400 B.C.E. when he described bubbly urine as a symptom of kidney disease. Over the next two thousand years, there were multiple allusions to foaming urine in the scientific and medical literature, indirectly linking it to kidney disease and to dropsy (tissue swelling because of retention of excessive amounts of fluid). In 1814, an English physician, John Blackall, published a book on dropsy in which he directly established a link between that condition and proteinuria (using the actual term). Shortly thereafter, fellow English physician Richard Bright published Reports of Medical Cases (1827), in which he identified edema and proteinuria as the major symptoms of nephritis (inflammation of the kidney, also known as Bright’s disease). Since that time, proteinuria has been considered to be an early and major symptom of kidney disease.
Bibliography
Brenner, Barry M., ed. Brenner and Rector’s The Kidney. 9th ed. Philadelphia: Saunders/Elsevier, 2012.
Glassock, R. J. “Focus on Proteinuria.” American Journal of Nephrology 10, suppl. 1 (1990): 88–93.
Haider, Mobeen Z., and Ahsan Aslam. "Proteinuria." StatPearls, 4 Sept. 2023, www.ncbi.nlm.nih.gov/books/NBK564390/. Accessed 8 Apr. 2024.
"Protein in Urine (Proteinuria)." Mayo Clinic, 5 May 2022, www.mayoclinic.org/symptoms/protein-in-urine/basics/causes/sym-20050656. Accessed 7 Aug. 2023.
"Proteinuria in Children." Family Doctor, American Academy of Family Physicians, June 2023, familydoctor.org/proteinuria-in-children/?adfree=true. Accessed 8 Apr. 2024.
Strasinger, Susan J., and Marjorie Schaub Di Lorenzo. Urinalysis and Body Fluids. 5th ed. Philadelphia: F. A. Davis, 2008.