Proteinuria

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Introduction

 

A healthy adult will normally secrete 40-150 mg/L of protein daily in the urine, with <20 mg/L albumin and <x mg uromodulin (Tamm-Horsfall mucoprotein). Assessing protein can be done in a number of ways, with differences in sensitivity and ease of use. Common means include urine dipsticks and 24 hour urine collection.

 

Microalbuminuria (30-300 mg/day) can be an early sign of renal disease in people with diabetes or hypertension, suggesting higher rates of cardiovascular morbidity and mortality. It can be picked up be radioimmunoassay, but most dipsticks are not sensitive enough to register microalbuminuria.

 

Proteinuria becomes abnormal at >300 mg/d. People with more than 3.5g/day have, in most cases, glomerular disease. ACE inhibitors, or ACE-ARB combinations, are useful at preventing progression of protein levels (need ref here).

 

 

The Case of...

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Differential Diagnosis

 

Functional proteinuria can occur following fever, exercise, congestive heart failure, or stress. It is benign and transient, lasting for hours to a few days.

 

Orthostatic/postural proteinuria is a benign, intermittent condition in which protein is usually present at <1 g/day and only when upright. It can be confirmed by nocturnal urine collection when the patient is supine.

 

Nephrotic syndrome is characterized by increased glomerular permeability and over 3.5 g protein/day, and has a long list of differential diagnoses.

 

Overflow proteinuria is due to an increased serum level of small MW proteins which overwhelms tubular reabsorption capacity. It results from...

 

Causes of proteinuria, with suggested further investigations, include:

cause

investigation(s)

exercise

urine sample on waking to be repeated without exercise 1-2 days before

diabetic nephropathy

blood glucose levels; other evidence of diabetic complications

urinary tract infection

mid-stream urine sample and culture

congestive heart failure

breath sounds; edema; JVP

multiple myeloma

CBC; serum/plasma protein electrophoresis

amyloid

biopsy; Congo red staining to look for associated splenomegaly

pregnancy

hCG pregnancy test

vaginal mucous contaminant

repeat, with sterile technique

 

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History and Physical Exam

  • history
  • physical exam

History

Physical Exam

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Investigations

  • lab investigations
  • diagnostic imaging

Lab Investigations

Diagnostic Imaging

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Management

 

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Pathophysiology

 

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Resources and References

 

 

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Topic Development

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