Acute Glomerulonephritis (AGN)

Acute Glomerulonephritis (AGN)

Epidemiology:

• AGN is more common during winter and spring, often associated with pharyngitis.

• In summer, AGN can be linked to skin infections.

Pathogenesis:

• AGN is caused by group A beta-hemolytic streptococcus (GAS) or other bacteria.

• The bacteria do not directly attack the kidneys but trigger a cross-reactive immune response against components of the glomerular basement membrane.

• This immune response leads to the formation of immune complexes, activating the complement system and attacking the glomerular basement membrane.

• This results in:

• Reduced normal blood C3 and C4 levels.

• Increased IgG deposition and leukocyte recruitment to the kidneys, causing cell damage.

• Immune complex deposition in the kidney parenchyma, causing acute glomerulonephritis.

• In severe cases, the inflammatory process can activate coagulation, leading to increased growth factors and damage to the glomeruli and renal tubules.

Pathology:

• Glomerular basement membrane inflammation: thickens the glomerular basement membrane, leading to:

• Reduced glomerular filtration rate.

• Water and salt retention, causing edema, affecting the heart and nerves.

• Red blood cell leakage, causing hematuria.

Clinical Manifestations:

• Age of onset: 5-12 years old.

• Male-to-female ratio: 2:1.

• Classic triad: edema, gross hematuria, and hypertension (HTN) (approximately 40% of cases).

• 100% of patients have microscopic hematuria.

Diagnosis:

• History and physical examination: based on epidemiology and clinical manifestations of nephritis.

• Disease progression:

• The disease usually subsides after 10-14 days.

• No recurrence.

• Exclusion: Other conditions causing glomerulonephritis need to be ruled out.

Prognosis:

• 90-95% of patients recover spontaneously after one week.

• The acute phase is critical during the first 7-10 days.

• 10-25% of cases have a poor outcome.

Paraclinical Investigations:

• Reduced complement CH50 and C3 (70-94%).

• X-ray: increased pulmonary circulation, pulmonary edema. Note for Mycoplasma in case of pneumonia.

• Anti-GAS antibody test: ASO.

Treatment:

Renal function rehabilitation:

• Furosemide (diuretic).

• Antihypertensive drugs.

• Note: Digitalis and Morphine are ineffective.

Hypertension management:

• Always combined with diuretics.

• Maintain normal blood pressure within 48 hours.

• Calcium channel blockers:

• Nifedipine orally.

• Nicardipine intravenously.

• Avoid ACE inhibitors due to the risk of hyperkalemia.

Edema reduction:

• Low-salt diet.

• Fluid restriction.

• Furosemide.

• Do not use Spironolactone as it is ineffective.

Antibiotic treatment:

• Only used if pharyngitis or skin infection progresses.

• Penicillin V: 100,000 IU/kg.

• Erythromycin: 75 mg/kg/day for 10 days.

Referral Indications:

• Anuria for > 2 days.

• No decrease in serum creatinine for > 2 weeks.

• Hypertension for > 4 weeks.

• Nephrotic syndrome for > 4 weeks.

• Gross hematuria for > 3-4 weeks.

• Proteinuria for > 6 weeks.

• Decreased C3 for > 8 weeks.

• Recurrence.

• Extrarenal complications.