Proteinuria
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More Specific Terms
Introduction
- Defined as > 50-100 mg of protein in 24 hour urine; > 3.5 grams in 24 hour urine indicates nephrotic syndrome.
Etiology
- most renal parenchymal disease is associated with some degree of proteinuria
- glomerular
- minimal change disease
- membranous nephropathy
- diabetic nephropathy
- focal sclerosis
- amyloidosis
- postinfectious glomerulonephritis
- IgA nephropathy
- membranoproliferative glomerulonephropathy
- other causes: endocarditis, hepatitis, endocarditis, HIV, Wegener's granulomatosis, lymphoma, malignancy nail-patella syndrome, von Gierke's disease
- pharmacologic agents
- ACE inhibitors, i.e. captopril
- gold salts
- penicillamine
- phenindione
- probenecid
- NSAIDs
- tubular
- generally < 1.5 grams/24 hours
- components:
- mechanism: tubular cell damage with inability to resorb filtered proteins
- congenital disorders
- acquired
- associated systemic conditions
- overflow
- generally consists of immunoglobulin light chains
- secondary glomerular proteinuria may be present
- lysozyme
- inherited or acquired hemolytic disorders
- microangiopathic infection, i.e. malaria
- McArdle's disease
- crush injury
- succinylcholine toxicity
- prolonged seizures
- hyperthermia
- associated with ambulation
- resolves during sleep ( supine)
- generally self-limited
- transient
- mechanism
- stimulation of renin-angiotensin-aldosterone axis
- decreased renal plasma flow
- febrile illness
- hypertension
- exercise
- major motor seizures
- generally mild & self-limited
Clinical-manifestations
-
- albuminuria
- increased serum cholesterol (usually)
- thrombo- emboli & renal vein thrombosis are common
- hypertension may be present
- signs & symptoms of systemic lupus erythematosus
- signs & symptoms of systemic multiple myeloma
- signs & symptoms of diabetes mellitus
- hepatosplenomegaly associated with:
- gross hematuria may be present with glomerulonephritis
Laboratory
-
- significant proteinuria as determined by 24 hour urine with negative or trace protein by dipstick suggests overflow proteinuria
- microscopy
- evidence of glomerular disease: RBC, RBC casts
- proteinuria + hematuria suggests glomerular disease even in the absence of RBC casts
- urine protein/creatinine ratio (mg/mg)
- a value < 0.1 generally corresponds to 24 hour urine protein of < 100 mg/day
- a value of 1.0 corresponds to 24 hour urine protein of ~ 500-1000 mg/day
- a value of > 3.0 generally corresponds to > 3 g/day, nephrotic level proteinuria
- may be collected in 2 containers, recumbent & ambulating for assessment of orthostatic proteinuria
- urea nitrogen
- creatinine
- albumin
- protein
- cholesterol
- relatively safe
- indications
- small kidneys: suggests scarring & fibrosis
- tubular proteinuria: not helpful
- orthostatic proteinuria: not helpful
Complications
- proteinuria independently predicts mortality & other adverse outcomes, regardless of the estimated glomerular filtration rate ( GFR) [4]
Management
- proteinuria generally not treated
- tubular
- orthostatic
- transient
- overflow proteinuria
- amyloidosis: treated as myeloma or with colchicine
- glomerular proteinuria
- not all patients require therapy
- immunosuppressive therapy
- general measures
-
- lower intraglomerular pressure
- decrease proteinuria, especially in diabetics
- Ca+2 channel blockers, diltiazem & verapamil preferable to dihydropyridines [3]
- NSAIDs
- low dose, use with caution ( nephrotoxic)
- may reduce proteinuria
- may reduce glomerulosclerosis
- protein restriction/balance
- sodium restriction
- potassium restriction may be indicated
- no restrictions in activity
More General Terms
Additional Terms
- 24 hour urine protein
- glomerulonephritis (GN, nephritic syndrome)
- nephrotic syndrome
- uromodulin; Tamm-Horsfall urinary glycoprotein; THP (UMOD)
References
- Saunders Manual of Medical Practice, Rakel (ed), WB Saunders, Philadelphia, 1996, pg 520-521
- Medical Knowledge Self Assessment Program (MKSAP) 11, American College of Physicians, Philadelphia 1998
- Prescriber's Letter 11(8): 2004 Antihypertensives in Patients with Hypertension and Proteinuria Detail-Document#: [1] (subscription needed) [2]
- Hemmelgarn BR et al for the Alberta Kidney Disease Network Relation Between Kidney Function, Proteinuria, and Adverse Outcomes JAMA. 2010;303(5):423-429 <PubMed> PMID: [3] <Internet> [4]
