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Nephrology - Proteinuria
Whiteboard Animation Transcript
with Manish Suneja, MD
medskl.com/Mod...
Proteinuria occurs when urinary excretion of protein is abnormally high (>150mg/day). It is important to distinguish transient and persistent proteinuria as it helps us to distinguish benign, self-limiting etiologies from more significant illnesses.
In fact the presence of proteinuria for more than three months with or without a decrease in glomerular filtration rate is diagnostic of chronic kidney disease.
The list of differential diagnoses for proteinuria includes almost any etiology of kidney disease.
Although there might be exceptions, the following framework is helpful in evaluating proteinuria:
1. Hematuria with overt proteinuria suggests glomerulonephritis
2. Significant proteinuria typically suggests glomerular diseases and plasma cell dyscrasias like multiple myeloma
3. Minimal to low-grade proteinuria indicates diseases that affect blood vessels
Proteinuria itself typically has few signs or symptoms. When there is significant proteinuria (especially nephrotic-range proteinuria), patients may notice edema in the extremities and face along with foamy urine.
Nephrotic range proteinuria may also result in volume overload and patients can present with pleural effusion and ascites. The presence of nephrotic-range proteinuria with edema, hypoalbuminemia, and hyperlipidemia is defined as nephrotic syndrome.
Proteinuria is often diagnosed incidentally on routine qualitative dipstick testing of urine sample. However, quantitative testing is important in evaluating proteinuria. The gold standard for confirming and quantifying proteinuria is a 24-hour urine collection. More recently, an acceptable alternative is calculating the protein-to-creatinine ratio and/or the albumin-to-creatinine ratio in a random urine sample.
Patients with chronic kidney disease, edema, acute kidney injury, hematuria, or suspected vasculitis should be tested for proteinuria. Moderately increased albuminuria (formerly called microalbuminuria) is particularly important because it signifies early stages of kidney disease. This should be a routine measurement in people with systemic conditions, like diabetes and hypertension, to screen for and detect nephropathy.
Management of proteinuria depends on the underlying pathology. For patients with intrinsic renal disease or systemic illnesses, treatment with Angiotensin Converting Enzyme inhibitors and Angiotensin Receptor Blockers are associated with improved renal outcomes. In instances where the diagnosis is not obvious or if there is significant proteinuria (3.5g/day), referral to nephrology is essential for further testing and management.
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