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What is Proteinuria and explain in detail?
Proteinuria is the presence of excess proteins in the urine. In healthy persons, urine contains very little protein; 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 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 in the urine (bilirubinuria), retrograde ejaculation, pneumaturia (air bubbles in the urine) due to a fistula, 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)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.Proteinuria may be a sign of renal (kidney) damage.  Since serum proteins are readily reabsorbed from urine, the presence of excess protein indicates either an insufficiency of absorption or impaired filtration. People with diabetes may have damaged nephrons and develop proteinuria.  The most common cause of proteinuria is diabetes, and in any person with proteinuria and diabetes, the cause of the underlying proteinuria should be separated into two categories: diabetic proteinuria versus the field.
With severe proteinuria, general hypoproteinemia can develop which results in
diminished oncotic pressure.  Symptoms of diminished oncotic pressure may include ascites, edema and hydrothorax.

Conditions with proteinuria
Proteinuria may be a feature of the following conditions:
Nephrotic syndromes (i.e. intrinsic kidney failure)
Pre-eclampsia
Eclampsia
Toxic lesions of kidneys
Amyloidosis
Collagen vascular diseases (e.g. systemic lupus erythematosus)
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. Bergers disease)
IgM nephropathy
Membranoproliferative glomerulonephritis
Membranous nephropathy
Minimal change disease
Sarcoidosis
Alport syndrome
Diabetes mellitus (diabetic nephropathy)
Drugs (e.g. NSAIDs, nicotine, penicillamine, lithium carbonate, gold and other heavy metals, ACE inhibitors, antibiotics, or opiates (especially heroin)
Fabry disease
Infections (e.g. HIV, syphilis, hepatitis, poststreptococcal infection, urinary schistosomiasis)
Aminoaciduria
Fanconi syndrome in association with Wilson disease
Hypertensive nephrosclerosis
Interstitial nephritis
Sickle cell disease
Hemoglobinuria
Multiple myeloma
Myoglobinuria
Organ rejection:
Ebola virus disease
Nail–patella syndrome
Familial Mediterranean fever
HELLP syndrome
Systemic lupus erythematosus
Granulomatosis with polyangiitis
Rheumatoid arthritis
Glycogen storage disease 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
Multiple myeloma
Waldenströms macroglobulinemia
Other malignancies
Chronic lymphocytic leukemia
Rare cases of other Lymphoid leukemias
Rare cases of Lymphomas

Pathophysiology
Protein 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 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 theres 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. Trace results may be produced in response to excretion of Tamm–Horsfall mucoprotein.
More recently developed technology detects human serum albumin (HSA) through the use of liquid crystals (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 level in a spot urine sample