Glomerulonephritis — Diagnosis & Investigations

Definition & Clinical Presentation

• Glomerular hematuria — dysmorphic RBCs and/or RBC casts in urine
• Hypertension
• Edema
• Reduced GFR (with or without oliguria)
• Non-nephrotic-range proteinuria

Classification (Etiology-Based)

Diagnosis

History & Physical Exam

• Recent throat/skin infection (1–4 weeks prior) → post-streptococcal GN
• Concurrent infection (active) → infection-associated GN
• Systemic symptoms (joints, skin, lungs) → vasculitis, lupus
• Family history → hereditary nephritis (Alport syndrome)
• Drugs (gold, penicillamine, NSAIDs) → secondary membranous nephropathy

Investigations

1. Urinalysis & Urine Microscopy

• Dysmorphic RBCs (acanthocytes) and RBC casts — pathognomonic for glomerular origin of hematuria
• Proteinuria — usually sub-nephrotic in nephritis; nephrotic range warrants evaluation for podocytopathy
• Urine culture — to exclude infection

"In glomerulonephritis, the urinalysis demonstrates macroscopic or microscopic hematuria, RBC casts, and proteinuria. Microscopic examination of urinary sediment shows dysmorphic RBCs and RBC casts." — Tintinalli's Emergency Medicine

2. Blood Tests

Basic Panel

Serological Panel (Key to Subtype Diagnosis)

3. Complement — A Key Diagnostic Discriminator

"When hematuria accompanies AKI, acute glomerulonephritis should be suspected and can diagnostically be divided into low-complement GN (immune complex-mediated lesions such as lupus nephritis, postinfectious GN, and cryoglobulinemic GN) and normocomplementemic GN (classically seen in RPGN due to ANCA and anti-GBM antibody)." — Goldman-Cecil Medicine

4. Urine Quantification

• 24-hour urine protein — nephrotic range (>3.5 g/day) vs. nephritic range (<3.5 g/day)
• Urine protein:creatinine ratio (PCR) — practical alternative to 24-hour collection
• Split urine collection — to exclude orthostatic proteinuria (supine vs. upright)

5. Imaging

• Renal ultrasound — assess kidney size, echogenicity, hydronephrosis, structural abnormalities; guides biopsy safety
• Chest CT — in suspected pulmonary-renal syndrome (ANCA vasculitis, anti-GBM disease); shows lung nodules, infiltrates, cavities, or alveolar hemorrhage

6. Renal Biopsy — Definitive Investigation

• Proteinuria with declining GFR
• Nephrotic-range proteinuria (>3.5 g/day)
• Proteinuria + features of glomerular source (albuminuria, acanthocytes, RBC casts)
• Persistent proteinuria with SLE or other rheumatologic condition
• Unexplained hematuria with proteinuria

"Specific diagnoses of renal disease require targeted immunofluorescent techniques for demonstrating a variety of antigens, antibodies, and complement fractions. Electron microscopy has complemented these immunologic methods." — Smith & Tanagho's General Urology, 19e

Immunofluorescence Patterns by GN Type

Diagnostic Algorithm Summary

Hematuria + AKI
     │
     ├─ Low complement ──► Immune complex GN
     │                      (Lupus, PSGN, Cryo)
     │
     └─ Normal complement ──► ANCA-associated GN (check MPO/PR3)
                               Anti-GBM disease (check anti-GBM Ab)
                               IgA nephropathy

Hematuria WITHOUT AKI ──► Chronic GN (IgA, thin GBM disease)

Proteinuria > 3.5 g/day ──► Nephrotic syndrome
                              (Biopsy if ANA, anti-PLA2R, viral serologies)

Specific Types at a Glance

Non-Pharmacological Treatment of Glomerulonephritis

1. Dietary Modifications

Salt (Sodium) Restriction

"Hypervolemia usually responds to salt restriction and loop diuretics. Volume control is often sufficient to manage the new-onset hypertension." — National Kidney Foundation Primer on Kidney Diseases, 8e

• Target: <2 g/day sodium (low-salt diet)
• Reduces edema, controls BP, and lessens the need for diuretics

Protein Restriction

"Symptomatic treatment should include bed rest and protein restriction (if the blood urea nitrogen or creatinine level is elevated)." — Swanson's Family Medicine Review

• Reduces the production of nitrogenous waste
• Helps manage uremia and reduces glomerular hyperfiltration
• Typical target: 0.6–0.8 g/kg/day in significant renal impairment

Fluid Restriction

• Indicated when significant edema or oliguria is present
• Works synergistically with salt restriction and diuretics
• Prevents volume overload and worsening hypertension

Potassium & Phosphate Restriction

• Required in advanced renal failure (GFR significantly reduced)
• Prevents hyperkalemia and hyperphosphatemia
• Limit high-potassium foods (bananas, oranges, potatoes) and phosphate-rich foods (dairy, processed foods)

2. Rest

• Bed rest is recommended during the acute phase of GN, particularly in PSGN
• Helps control hypertension and reduces metabolic demand on kidneys
• Activity can be gradually resumed as edema, hematuria, and hypertension resolve

3. Fluid & Edema Management (Non-Drug)

• Fluid restriction combined with sodium restriction
• Elevation of oedematous limbs where applicable
• Monitoring daily weight and urine output to track fluid balance
• Loop diuretics are the pharmacological adjunct to these measures — but the dietary sodium restriction is the non-pharmacological foundation

4. Blood Pressure Control (Non-Pharmacological Components)

• Salt restriction alone can normalize BP in many patients with PSGN
• Weight management and reduced alcohol intake are standard lifestyle modifications
• In most acute GN cases, BP resolves within 1–2 weeks as volume overload is corrected

5. Treatment/Control of the Underlying Infection (Infection-Associated GN)

• In post-streptococcal GN: penicillin treats the streptococcal infection but does not alter the course of GN itself
• Antibiotic prophylaxis of household/community contacts in epidemic PSGN can reduce disease incidence
• For GN associated with active infection (e.g., endocarditis, abscesses): treating the source infection is the primary non-immunosuppressive strategy

"Although penicillin will eradicate the carrier state of group A β-hemolytic streptococci, it will not influence the course of the glomerulonephritis." — Swanson's Family Medicine Review

6. Renal Replacement Therapy (Dialysis)

• Haemodialysis or peritoneal dialysis may be required for:
  • Persistent volume overload unresponsive to diuretics
  • Severe uraemia (encephalopathy, pericarditis)
  • Severe hyperkalemia or metabolic acidosis refractory to medical management
• Need for dialysis is more frequent in adults than children

"Dialysis may be necessary, and the need for dialysis is more frequent in adults." — National Kidney Foundation Primer on Kidney Diseases, 8e

7. Plasmapheresis (Plasma Exchange)

• Used as an adjunct in anti-GBM disease (Goodpasture syndrome) and select cases of ANCA-associated RPGN
• Also reported as adjunct therapy in infective endocarditis-related GN when kidney function fails to improve despite antibiotics
• Removes circulating antibodies (anti-GBM, ANCA, cryoglobulins) and immune complexes

8. Lifestyle Modifications (Long-Term / CKD Prevention)

Summary by Phase