Acute Postinfectious Glomerulonephritis

Acute postinfectious glomerulonephritis (APIGN) is an acute nephritic syndrome caused by immune-complex deposition in the glomeruli after a bacterial infection, most often group A streptococcal pharyngitis or impetigo. The infection and the kidney injury are separated by a characteristic interval: approximately 7–15 days after pharyngitis and 4–6 weeks after impetigo. The immune complexes activate complement and inflame the glomerular capillary loops. The inflamed glomerulus becomes less effective at filtering plasma. Red blood cells can cross into the urine, while the reduced filtration rate promotes sodium and water retention. That combination produces the pattern nurses recognize: dark or tea-coloured urine, proteinuria, edema, reduced urine output, and hypertension. Protein loss is usually modest, often less than 2 g/day. This helps distinguish APIGN from a predominantly nephrotic process, in which heavy protein loss drives marked hypoalbuminemia and generalized edema. The blood pressure rise is not simply a symptom; it reflects retained volume and can become dangerous if it compromises the brain, heart, or lungs.