Nephrotic Syndrome
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Introduction
Nephrotic syndrome is characterized by increased glomerular permeability due to basement membrane damage and increased pore size. This leads to proteinuria above 3.5 g/day, leading to hypoalbuminemia, edema, and hyperlipidemia, and hyerlipiduria.
The Case of...
a simple case introducing clincial presentation and calling for a differential diagnosis to get students thinking.
Causes and Risk Factors
Many cases are idiopathic.
Causes include glomerular diseases with 'bland' urine sediment, without RBCs:
- minimal change disease (85-90% pediatrics, 15-20% of adults)
- focal segmental glomerulosclerosis (10-15% of pediatrics, most common in adults)
- membranous glomerulonephropathy (25-30% of adults)
- diabetic nephropathy (secondary)
- amylodosis (secondary)
Mixed nephritic/nephrotic syndromes, with RBC casts present, can be caused by:
- membranoproliferative glomerulonephropathy
- systemic lupus erythmatosus (SLE) (secondary)
- postinfectious glomerulonephritis
- mixed essential cryoglobulinemia
Other secondary causes include drugs (ie penicillimine, gold), malignancy, bacterial endocarditis.
Pathophysiology
Capillary walls become permeable to proteins of higher molecular weight as the severity of injury increases. A limited amount of protein can be reabsorbed by endocytosis, but f this is exceeded, protein is lost in the urine.
Albumin within the body's capillaries helps maintain colloid osmotic pressure, but if this decreases, less fluid moves back into the capillaries, causing peripheral edema.
Decreased circulating volume activates the renin-angiotensin-aldosterone system, leading to further sodium/water retention and further edema.
Signs and Symptoms
- history
- physical exam
History
Physical Exam
Investigations
- lab investigations
- diagnostic imaging
Lab Investigations
Oval fat bodies, coarse granular casts, and occasional cells may be present.
As people lose proteins, they are at increased risk of thrombosis (clotting factors), infections (immunoglobulins), and dyslipidemia (lipoproteins).
ANA, RF, etc
Evaluate for HIV, HBV.
Biopsy is an important test to do.
Diagnostic Imaging
Differential Diagnosis
Treatments
Management includes:
blood pressure control
sodium restriction
reduction of proteinuria using ACE inhibitors
control of hyperlipidemia
anticoagulation if hypercoagulable (risk of thrombosis increases as albumin decreases)
treatment of underlying causes when possible, ie high-dose corticosteroids for minimal change disease
Consequences and Course
Complications include:
- hypercoagulable state, with increased risk of DVT, pulmonary embolus, and renal vein thrmobosis
- hyperlipidemia, with increased risk of vascular disease and ischemic heart disease
- immunosuppresion, and risk of infection
Resources and References
Topic Development
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