Proteinuria is the presence of excess

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

s in the

urine Urine is a liquid by-product of metabolism in humans and many other animals. In placental mammals, urine flows from the Kidney (vertebrates), kidneys through the ureters to the urinary bladder and exits the urethra through the penile meatus (mal ...

. In healthy persons, urine contains very little protein, less than 150 mg/day; an excess is suggestive of illness. Excess protein in the urine often causes the urine to become foamy (although this symptom may also be caused by other conditions). Severe proteinuria can cause

nephrotic syndrome Nephrotic syndrome is a collection of symptoms due to kidney damage. This includes proteinuria, protein in the urine, hypoalbuminemia, low blood albumin levels, hyperlipidemia, high blood lipids, and significant edema, swelling. Other symptoms ...

in which there is worsening swelling of the body.

Signs and symptoms

Proteinuria often causes no symptoms and it may only be discovered incidentally. Foamy urine is considered a cardinal sign of proteinuria, but only a third of people with foamy urine have proteinuria as the underlying cause. It may also be caused by

bilirubin Bilirubin (BR) (adopted from German, originally bili—bile—plus ruber—red—from Latin) is a red-orange compound that occurs in the normcomponent of the straw-yellow color in urine. Another breakdown product, stercobilin, causes the brown ...

in the urine ( bilirubinuria),

retrograde ejaculation Retrograde ejaculation occurs when semen which would be ejaculated via the urethra is redirected to the urinary bladder. Normally, the sphincter of the bladder contracts before ejaculation, inhibiting urination and preventing a reflux of semen ...

, pneumaturia (air bubbles in the urine) due to a

fistula In anatomy, a fistula (: fistulas or fistulae ; from Latin ''fistula'', "tube, pipe") is an abnormal connection (i.e. tube) joining two hollow spaces (technically, two epithelialized surfaces), such as blood vessels, intestines, or other h ...

, or drugs such as pyridium.

Causes

There are three main mechanisms to cause proteinuria: * Due to disease in the glomerulus * Because of increased quantity of proteins in serum (overflow proteinuria) * Due to low reabsorption at proximal tubule (

Fanconi syndrome Fanconi syndrome or Fanconi's syndrome (, ) is a syndrome of inadequate reabsorption in the proximal renal tubules of the kidney. The syndrome can be caused by various underlying congenital or acquired diseases, by toxicity (for example, from t ...

) Proteinuria can also be caused by certain biological agents, such as bevacizumab (Avastin) used in cancer treatment. Excessive fluid intake (drinking in excess of 4 litres of water per day) is another cause.

Conditions with proteinuria

Proteinuria may be a feature of the following conditions: * Nephrotic syndromes (i.e. intrinsic

kidney failure Kidney failure, also known as renal failure or end-stage renal disease (ESRD), is a medical condition in which the kidneys can no longer adequately filter waste products from the blood, functioning at less than 15% of normal levels. Kidney fa ...

) *

Pre-eclampsia Pre-eclampsia is a multi-system disorder specific to pregnancy, characterized by the new onset of hypertension, high blood pressure and often a significant amount of proteinuria, protein in the urine or by the new onset of high blood pressure a ...

Eclampsia Eclampsia is the onset of seizures (convulsions) in a pregnant woman with pre-eclampsia. Pre-eclampsia is a hypertensive disorder of pregnancy that presents with three main features: new onset of high blood pressure, large amounts of proteinuria ...

* Toxic lesions of

kidney In humans, the kidneys are two reddish-brown bean-shaped blood-filtering organ (anatomy), organs that are a multilobar, multipapillary form of mammalian kidneys, usually without signs of external lobulation. They are located on the left and rig ...

s * Amyloidosis * Collagen vascular diseases (e.g.

systemic lupus erythematosus Lupus, formally called systemic lupus erythematosus (SLE), is an autoimmune disease in which the body's immune system mistakenly attacks healthy tissue in many parts of the body. Symptoms vary among people and may be mild to severe. Common ...

) * Dehydration * Glomerular diseases, such as membranous glomerulonephritis, focal segmental glomerulonephritis, minimal change disease ( lipoid nephrosis) * Strenuous exercise * Stress * Benign orthostatic (postural) proteinuria * Focal segmental glomerulosclerosis (FSGS) * IgA nephropathy (i.e. Berger's disease) * IgM nephropathy * Membranoproliferative glomerulonephritis * Membranous nephropathy * Minimal change disease *

Sarcoidosis Sarcoidosis (; also known as Besnier–Boeck–Schaumann disease) is a disease involving abnormal collections of White blood cell, inflammatory cells that form lumps known as granulomata. The disease usually begins in the lungs, skin, or lymph n ...

* Alport syndrome *

Diabetes mellitus Diabetes mellitus, commonly known as diabetes, is a group of common endocrine diseases characterized by sustained hyperglycemia, high blood sugar levels. Diabetes is due to either the pancreas not producing enough of the hormone insulin, or th ...

( diabetic nephropathy) * Drugs (e.g. NSAIDs,

nicotine Nicotine is a natural product, naturally produced alkaloid in the nightshade family of plants (most predominantly in tobacco and ''Duboisia hopwoodii'') and is widely used recreational drug use, recreationally as a stimulant and anxiolytic. As ...

, penicillamine,

lithium carbonate Lithium carbonate is an inorganic compound, the lithium salt of carbonic acid with the chemical formula, formula . This white Salt (chemistry), salt is widely used in processing metal oxides. It is on the WHO Model List of Essential Medicines, Wor ...

, gold and other

heavy metals upright=1.2, Crystals of lead.html" ;"title="osmium, a heavy metal nearly twice as dense as lead">osmium, a heavy metal nearly twice as dense as lead Heavy metals is a controversial and ambiguous term for metallic elements with relatively h ...

ACE inhibitors Angiotensin-converting-enzyme inhibitors (ACE inhibitors) are a class of medication used primarily for the treatment of hypertension, high blood pressure and heart failure. This class of medicine works by causing relaxation of blood vessels as ...

antibiotics An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting pathogenic bacteria, bacterial infections, and antibiotic medications are widely used in the therapy ...

, or

opiates An opiate is an alkaloid substance derived from opium (or poppy straw). It differs from the similar term ''opioid'' in that the latter is used to designate all substances, both natural and synthetic, that bind to opioid receptors in the brain ( ...

(especially

heroin Heroin, also known as diacetylmorphine and diamorphine among other names, is a morphinan opioid substance synthesized from the Opium, dried latex of the Papaver somniferum, opium poppy; it is mainly used as a recreational drug for its eupho ...

) * Fabry disease * Infections (e.g. HIV,

syphilis Syphilis () is a sexually transmitted infection caused by the bacterium ''Treponema pallidum'' subspecies ''pallidum''. The signs and symptoms depend on the stage it presents: primary, secondary, latent syphilis, latent or tertiary. The prim ...

hepatitis Hepatitis is inflammation of the liver parenchyma, liver tissue. Some people or animals with hepatitis have no symptoms, whereas others develop yellow discoloration of the skin and whites of the eyes (jaundice), Anorexia (symptom), poor appetite ...

, poststreptococcal infection, urinary

schistosomiasis Schistosomiasis, also known as snail fever, bilharzia, and Katayama fever is a neglected tropical helminthiasis, disease caused by parasitism, parasitic Schistosoma, flatworms called schistosomes. It affects both humans and animals. It affects ...

) * Aminoaciduria *

in association with Wilson disease * Hypertensive nephrosclerosis * Interstitial nephritis *

Sickle cell disease Sickle cell disease (SCD), also simply called sickle cell, is a group of inherited Hemoglobinopathy, haemoglobin-related blood disorders. The most common type is known as sickle cell anemia. Sickle cell anemia results in an abnormality in the ...

* Hemoglobinuria *

Multiple myeloma Multiple myeloma (MM), also known as plasma cell myeloma and simply myeloma, is a cancer of plasma cells, a type of white blood cell that normally produces antibody, antibodies. Often, no symptoms are noticed initially. As it progresses, bone ...

* Myoglobinuria *

Organ rejection Organ and organs may refer to: Biology * Organ (biology), a group of tissues organized to serve a common function * Organ system, a collection of organs that function together to carry out specific functions within the body. Musical instruments ...

: *

Ebola virus disease Ebola, also known as Ebola virus disease (EVD) and Ebola hemorrhagic fever (EHF), is a viral hemorrhagic fever in humans and other primates, caused by ebolaviruses. Symptoms typically start anywhere between two days and three weeks after infe ...

Nail–patella syndrome Nail–patella syndrome is a genetic disorder that results in small, poorly developed nail (anatomy), nails and kneecaps, but can also affect many other areas of the body, such as the elbows, chest, and hips. The name "nail–patella" can be very ...

* Familial Mediterranean fever * HELLP syndrome *

Systemic lupus erythematosus Lupus, formally called systemic lupus erythematosus (SLE), is an autoimmune disease in which the body's immune system mistakenly attacks healthy tissue in many parts of the body. Symptoms vary among people and may be mild to severe. Common ...

Granulomatosis with polyangiitis Granulomatosis with polyangiitis (GPA), formerly known as Wegener's granulomatosis (WG), after Nazi German physician Friedrich Wegener, is a rare, long-term, systemic disorder that involves the formation of granulomas and vasculitis, inflammatio ...

Rheumatoid arthritis Rheumatoid arthritis (RA) is a long-term autoimmune disorder that primarily affects synovial joint, joints. It typically results in warm, swollen, and painful joints. Pain and stiffness often worsen following rest. Most commonly, the wrist and h ...

Glycogen storage disease A glycogen storage disease (GSD, also glycogenosis and dextrinosis) is a metabolic disorder caused by a deficiency of an enzyme or transport protein affecting glycogen synthesis, glycogen breakdown, or glycolysis, glucose breakdown, typically in m ...

type 1 * Goodpasture syndrome * Henoch–Schönlein purpura * A urinary tract infection which has spread to the kidney(s) * Sjögren syndrome * Post-infectious glomerulonephritis * Living kidney donor * Polycystic kidney disease

Bence–Jones proteinuria

* Amyloidosis * Pre-malignant plasma cell dyscrasias: ** Monoclonal gammopathy of undetermined significance ** Smoldering multiple myeloma * Malignant plasma cell dyscrasias **

** Waldenström's macroglobulinemia * Other malignancies **

Chronic lymphocytic leukemia Chronic lymphocytic leukemia (CLL) is a type of cancer that affects the blood and bone marrow. In CLL, the bone marrow makes too many lymphocytes, which are a type of white blood cell. In patients with CLL, B cell lymphocytes can begin to colle ...

** Rare cases of other Lymphoid leukemias ** Rare cases of

Lymphoma Lymphoma is a group of blood and lymph tumors that develop from lymphocytes (a type of white blood cell). The name typically refers to just the cancerous versions rather than all such tumours. Signs and symptoms may include enlarged lymph node ...

Pathophysiology

Protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

is the building block of all living organisms. When kidneys are functioning properly by filtering the blood, they distinguish the proteins from the wastes which were previously present together in the blood. Thereafter, kidneys retain or reabsorb the filtered proteins and return them to the circulating blood while removing wastes by excreting them in the urine. Whenever the kidney is compromised, their ability to filter the blood by differentiating protein from the waste, or retaining the filtered protein then returning which back to the body, is damaged. As a result, there is a significant amount of protein to be discharged along with waste in the urine that makes the concentration of proteins in urine high enough to be detected by medical machine. Medical testing equipment has improved over time, and as a result tests are better able to detect smaller quantities of protein. Protein in urine is considered normal as long as the value remains within the normal reference range. Variation exists between healthy patients, and it is generally considered harmless for the kidney to fail to retain a few proteins in the blood, letting those protein discharge from the body through urine.

Albumin and immunoglobins

Albumin is a protein produced by the liver which makes up roughly 50%-60% of the total proteins in the blood while the other 40%-50% are proteins other than albumin, such as immunoglobins. This is why the concentration of albumin in the urine is one of the single sensitive indicators of kidney disease, particularly for those with diabetes or hypertension, compared to routine proteinuria examination. As the loss of proteins from the body progresses, the suffering will gradually become symptomatic. The exception applies to the scenario when there's an overproduction of proteins in the body, in which the kidney is not to blame.

Diagnosis

Conventionally, proteinuria is diagnosed by a simple dipstick test, although it is possible for the test to give a false negative reading, even with nephrotic range proteinuria if the urine is dilute. False negatives may also occur if the protein in the urine is composed mainly of globulins or Bence Jones proteins because the reagent on the test strips, bromophenol blue, is highly specific for albumin. Traditionally, dipstick protein tests would be quantified by measuring the total quantity of protein in a 24-hour urine collection test, and abnormal globulins by specific requests for protein electrophoresis. More recently developed technology detects

human serum albumin Human serum albumin is the serum albumin found in human blood. It is the most abundant protein in human blood plasma; it constitutes about half of serum protein. It is produced in the liver. It is soluble in water, and it is monomeric. Albumin ...

(HSA) through the use of

liquid crystal Liquid crystal (LC) is a state of matter whose properties are between those of conventional liquids and those of solid crystals. For example, a liquid crystal can flow like a liquid, but its molecules may be oriented in a common direction as i ...

s (LCs). The presence of HSA molecules disrupts the LCs supported on the AHSA-decorated slides thereby producing bright optical signals which are easily distinguishable. Using this assay, concentrations of HSA as low as 15 μg/mL can be detected. Alternatively, the concentration of protein in the urine may be compared to the

creatinine Creatinine (; ) is a breakdown product of creatine phosphate from muscle and protein metabolism. It is released at a constant rate by the body (depending on muscle mass). Biological relevance Serum creatinine (a blood measurement) is an impor ...

level in a spot urine sample. This is termed the protein/creatinine ratio. The 2005 UK Chronic Kidney Disease guidelines state that protein/creatinine ratio is a better test than 24-hour urinary protein measurement. Proteinuria is defined as a protein/creatinine ratio greater than 45 mg/mmol (which is equivalent to albumin/creatinine ratio of greater than 30 mg/mmol or approximately 300 mg/g) with very high levels of proteinuria having a ratio greater than 100 mg/mmol. Protein dipstick measurements should not be confused with the amount of protein detected on a test for microalbuminuria which denotes values for protein for urine in mg/day versus urine protein dipstick values which denote values for protein in mg/dL. That is, there is a basal level of proteinuria that can occur below 30 mg/day which is considered non-pathology. Values between 30 and 300 mg/day are termed microalbuminuria which is considered pathologic. Urine protein lab values for microalbumin of >30 mg/day correspond to a detection level within the "trace" to "1+" range of a urine dipstick protein assay. Therefore, positive indication of any protein detected on a urine dipstick assay obviates any need to perform a urine microalbumin test as the upper limit for microalbuminuria has already been exceeded.

Analysis

It is possible to analyze urine samples in determining

albumin Albumin is a family of globular proteins, the most common of which are the serum albumins. All of the proteins of the albumin family are water- soluble, moderately soluble in concentrated salt solutions, and experience heat denaturation. Alb ...

hemoglobin Hemoglobin (haemoglobin, Hb or Hgb) is a protein containing iron that facilitates the transportation of oxygen in red blood cells. Almost all vertebrates contain hemoglobin, with the sole exception of the fish family Channichthyidae. Hemoglobin ...

and

myoglobin Myoglobin (symbol Mb or MB) is an iron- and oxygen-binding protein found in the cardiac and skeletal muscle, skeletal Muscle, muscle tissue of vertebrates in general and in almost all mammals. Myoglobin is distantly related to hemoglobin. Compar ...

with an optimized MEKC method.

Treatment

The most common cause is diabetic nephropathy; in this case, proper glycemic control may slow the progression. Medical management consists of angiotensin converting enzyme (ACE) inhibitors, which are typically first-line therapy for proteinuria. In patients whose proteinuria is not controlled with ACE inhibitors, the addition of an aldosterone antagonist (i.e.,

spironolactone Spironolactone, sold under the brand name Aldactone among others, is classed as a diuretic medication. It can be used to treat edema, fluid build-up due to hepatic cirrhosis, liver disease or kidney disease. It is also used to reduce risk o ...

) or angiotensin receptor blocker (ARB) may further reduce protein loss. Atrasentan (Vanrafia) was approved for medical use in the United States in April 2025.

References

External links

{{Authority control Abnormal clinical and laboratory findings for urine