Acute Postinfectious Glomerulonephritis

Acute postinfectious glomerulonephritis (APIGN) is an acute nephritic syndrome that follows an infection. The classic post-streptococcal form follows group A streptococcal pharyngitis or impetigo, while other bacterial infections can produce related infection-associated patterns. In the classic pattern, nephritic symptoms appear after the infection rather than at its onset: about 1–2 weeks after pharyngitis or 4–6 weeks after impetigo. Antigen–antibody immune complexes form or become deposited in the glomeruli, activate complement, and cause inflammation. The inflamed filtration barrier permits red blood cells and protein to enter the urine. Reduced glomerular filtration also promotes sodium and water retention. Together, these changes explain the linked findings of smoky, tea-coloured, or reddish-brown urine; proteinuria; periorbital or dependent edema; hypertension; and reduced urine output. The pattern is nephritic rather than an isolated urinary tract problem. Volume retention can affect the lungs, heart, and brain, while glomerular injury can progress to acute kidney injury. Most post-streptococcal cases improve with supportive management, but an adult or any patient with severe kidney dysfunction, hypertensive target-organ injury, pulmonary edema, or a complicated active infection needs close medical and nephrology...