|
|
|
Home > Patient Information > Nephrology Division > Physician Page > Proteinuria
Proteinuria
Please call the Nephrology Clinic at (757) 953-2051 or fax (757) 953-0827 for
questions
Proteinuria may be the first and only evidence of renal disease. Most healthy persons excrete up to 150mg of urinary protein daily, which may vary on urine dipstick analysis from negative to 2+. Although the prevalence of proteinuria on routine screening of healthy individuals has been as high as 3.5%, the incidence of real disease in this population is very low. It is clear that the discovery of proteinuria necessitates a thorough evaluation to separate these healthy individuals form those with significant renal disease.
The reagent strip method (dipstick) is the most commonly employed method to test for proteinuria. It tests mainly for albumin, is sensitive to 10-30 mg/dl and is read out by a color change. The intensity of the color change is proportional to the concentration of protein, with trace + 10-30 mg/dl, 1+ = 30 mg/dl, 2+ = 100 mg/dl, 3+ = 500 mg/dl, and 4+ = >1000 mg/dl. Highly concentrated or alkaline(pH > 8) specimens may give a false positive reaction, while very dilute urine and globulins may give a false negative reaction.
Once proteinuria is detected by dipstick, the next step should be to obtain a detailed history, physical exam, and urine microscopy. This includes family history as well as prior evaluations and medications (i.e. NSAID's). The exam should look for evidence of renal or systemic disease, focusing on blood pressure, pulse, fundi, cardiovascular, skin, abdominal (palpable kidneys or bruits) and the presence or absence of edema.
If no such evidence is found, repeat dipstick analysis should be done two or three times. If these subsequent qualitative tests, in well concentrated specimens, are negative for protein, the initial proteinuria was transient of functional. Functional proteinuria may be seen in conditions such as high fever, emotional stress, cold exposure, strenuous exercise, infection and other acute medical illnesses. Idiopathic transient proteinuria is a common cause of proteinuria in young adults, especially men. It is characterized by proteinuria on a routine urinalysis which then disappears on repeat testing and is found in a asymptomatic, healthy person with normal renal function.
Another entity seen in adolescents (rarely >30 yrs.) Is orthostatic proteinuria. This type of proteinuria increases in the upright posture. Approximately 90% of otherwise healthy young men with isolated proteinuria have orthostatic proteinuria. A simple evaluation follows. The patient voids in the evening and then retires immediately. The next morning a urine sample is obtained while still supine. The patient then ambulates and a third sample is obtained. The orthostatic proteinuria will be present in the first and last specimens and absent in the supine sample.
Any patient with proteinuria which is persistent or not associated with a functional cause should have their proteinuria quantified with a 24 hour urine collection. Patient with significant proteinuria (>150 mg/day) but less than 3 grams a day may have any of the above mentioned entities. Other considerations would include hypertensive nephrosclerosis, polycystic kidney disease, obstructive uropathy, interstitial nephritis, or glomerulonephritis. All of these would have pertinent history, physical exam, or lab abnormalities.
Higher grades of proteinuria are associated with other conditions as well, such as diabetic nephropathy, amyloidosis, lymphoma, lupus, NSAID's, AIDS, heroin use, myeloma, chronic hepatitis, syphilis, or idiopathic glomerulonephritis (minimal change disease, focal and segmental glomerulonephritis, membranous nephropathy, and membrano- proliferative glomerulonephritis). Evidence of greater than 3.4 grams proteinuria/day, edema, hyperalbuminemia, and hyperlipidemia defines the nephrotic syndrome.
Certainly, any person with a suspect history, abnormal physical exam, or lab evaluations, abnormal urine microscopy or proteinuria other than obvious functional proteinuria, should be returned to Internal Medicine, and preferably, Nephrology.
Quantification of the urine with a 24 hour sample, if available, is helpful but not required prior to consultation. Other lab studies indicated include determination of creatinine clearance, serum protein, electrophoresis, serum total cholesterol, and calcium. In selected cases, complement levels, ANA, cryoglobulin, hepatitis serologies, HIV, and RPR should be ordered. Renal biopsy is indicated for the differential diagnosis in most cases of Nephrotic syndrome or other atypical cases, even with lesser amounts of proteinuria.
Treatment of those with significant proteinuria and Nephrotic syndrome will be instituted by the specialist and may include dietary sodium restriction, diuretics, corticosteroids and/or cytotoxic agents.
Telephone consultation may be made with the Nephrology Division, Naval Medical Center, Portsmouth, Virginia. Telephone: (757) 953-2051.
Last Updated: 27 February 2002
