Nephritic Syndrome
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Introduction
Nephritic syndrome is defined by:
- hematuria with dysmorphic RBC's and casts
- proteinuria <2g/day
The Case of...
a simple case introducing clincial presentation and calling for a differential diagnosis to get students thinking.
Causes and Risk Factors
The most common cause of nephritic syndrome is proliferative glomerulonephritis.
Post-streptococcal glomerulornephritis (PSGN) is the most common cause of nephritic syndrome. It is most common in children but can also occur in adults.
Other causes include post-infectious reaction to bacteria (staphylococci, pneumococci), viruses (mumps, hepatitis B, varicella, coxsackievirus, EBV), protozoa (Toxoplasmia gondii, Plasmodium), and others
Idiopathic causes include IgA nephropathy, membranoproliferative glomerulonephritis, and focal proliferative GN, a less acute disease.
Drug induced causes include gold and penicillamine.
Secondary causes include multisystem diseases such as SLE, essential mixed cryoglobulinemia, vasculitis, Wegener's granulomatosis, and polyarteritis nodosa.
Rapidly progressive GN, or crescentic GN, occurs with severe glomerular injury, presenting with hematuria, oliguria, hypertension, and eventual renal failure.
Pathophysiology
Immune complex deposition in the basement membrane, followed by local and systemic cytokine release, leads to damage and reduced GFR. Salt and water retention with ECF volume expansion, hypertension, and edema.
Sodium avidity is increased in the face of decreased GFR, and plasma albumin generally remains normal; as such, hypertension, plasma volume dilution, circulatory overload, and congestive heart failure can result.
Hyperkalemia can result (how)?
In rapidly progressive glomerulonephritis, severe glomerular injury leads to leakage of fibrin, stimulating epithelial cells and macropages within Bowman's capsule to proliferate and form crescent shaped tissue deposits. This reduces glomerular blood supply.
Signs and Symptoms
- history
- physical exam
History
PSGN is a complication of nephritogenic strains of group A beta-hemolytic strep. It follows streptococcal pharyngitis, tonsilitis, or cellulitis in less than 5% of people, usually with a 7-28 day latent period.
Oligouria and flank pain can be present
Physical Exam
Hypertension and edema follow salt and water retention due to decreased GFR.
Investigations
- lab investigations
- diagnostic imaging
Lab Investigations
Clincial features of PSGN centre around decreased renal function, leading to rise in sCR and BUN.
Proteinura, hematuria, both (RBCs and RBC casts) can be present.
ASOT will be positive following 80% of strep infections.
ANA antibodies
Low serum complement during active disease
Diagnostic Imaging
Differential Diagnosis
Treatments
No treatment for PSGN has been developed, though antibiotics can be used if infection lingers.
Salt restriction, diuretics, and antihypertensive agents can be used to manage hypertension, edema, and heart failure.
For rapidly progressive glomerulonephritis, which is seen in systemic diseases such as SLE, Wegener's granulomatosis, and microscopic polyangiitis, promt diagnosis and treatment with high-dose steroids, immunosuppressants, and plasma exchange is necessary to prevent hypertension, renal scarring, and kidney failure.
Consequences and Course
Complete recovery occurs in over 90% of children, but only 60% of adults fully recover. The rest develop hypertension or renal impairment.
Progression to renal failure is uncommon, but can can occur over days to weeks - (rapidly progressive glomerulonephritis), or over months to years (chronic nephritic syndrome).
Resources and References
Topic Development
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