Proteinuria
Background
- Normal protein excretion <150mg/24 hours
- >3.5g/24h is nephrotic range
- Dipstick: more sensitive to albumin, less sensitive to Bence-Jones protein and globulins
- "Trace" protein on dipstick is approximately normal
- Key EM role: identify proteinuria associated with emergent conditions (preeclampsia, nephrotic syndrome, glomerulonephritis)
- Incidental proteinuria on UA often requires outpatient follow-up, not ED workup
Differential Diagnosis
Transient/Functional (Benign)
- Fever, acute illness, strenuous exercise, orthostatic proteinuria
- Dehydration, cold exposure
- Usually resolves when precipitant corrected — no further workup needed in ED
Renal
- Glomerulonephritis: hematuria + proteinuria + RBC casts
- Nephrotic syndrome: massive proteinuria, hypoalbuminemia, edema, hyperlipidemia
- Diabetic nephropathy: most common cause of chronic proteinuria
- Tubular dysfunction, IgA nephropathy, membranous nephropathy
- Pyelonephritis, malignant hypertension
Pregnancy-Related
- Preeclampsia / eclampsia / HELLP: proteinuria + hypertension after 20 weeks
- Acute fatty liver of pregnancy
Other
- CHF, shock (functional/prerenal)
- Drug-induced: NSAIDs, aminoglycosides, amphotericin, penicillamine
- Multiple myeloma (Bence-Jones protein — may be missed by dipstick)
Evaluation
When to Evaluate in ED
- Pregnant patient with proteinuria → check BP, labs for preeclampsia
- Proteinuria + hematuria + RBC casts → glomerulonephritis workup
- Proteinuria + severe edema → nephrotic syndrome workup
- Isolated trace/1+ proteinuria without above features → outpatient follow-up
Workup
- BMP: creatinine, albumin
- CBC
- Urine protein-to-creatinine ratio (spot urine — correlates with 24h protein)
- Urine microscopy: RBC casts (GN), oval fat bodies (nephrotic syndrome)
- If preeclampsia: LFTs, uric acid, LDH, platelet count
Management
- Treat underlying cause
- Preeclampsia: magnesium sulfate, antihypertensives, OB consultation
- Nephrotic syndrome: diuretics for edema, nephrology referral
- Most isolated proteinuria: outpatient nephrology follow-up
Disposition
- Admit: preeclampsia/eclampsia, acute GN with renal failure, severe nephrotic syndrome
- Discharge: incidental proteinuria with normal renal function — arrange outpatient repeat UA and nephrology referral