Case Study: The Man Who Stopped Urinating

Presentation: A 45-year-old man develops severe streptococcal throat infection. Three weeks later, he notices his ankles are swollen, his urine is tea-coloured, and his urine output has dropped to 300 mL/day. Blood tests show elevated creatinine.

Step-by-step Analysis:

Step 1 — Identify the Timeline Post-streptococcal infection (3 weeks later). This timing strongly suggests post-streptococcal glomerulonephritis.

Step 2 — Explain the Tea-Coloured Urine The glomerular filtration barrier is inflamed → blood cells (RBCs) leak into filtrate → haematuria → tea/cola-coloured urine. This is a hallmark of the NEPHRITIC syndrome.

Step 3 — Explain the Ankle Swelling (Oedema) Inflamed glomeruli leak proteins → proteinuria → hypoalbuminaemia → reduced plasma oncotic pressure → fluid shifts from capillaries into interstitial spaces → oedema. Also: reduced GFR → Na+ and water retention → more oedema.

Step 4 — Explain Oliguria $\frac{300 mL}{day}$ Normal = 1.5 L/day. 300 mL/day = oliguria. The inflamed glomeruli have reduced filtration surface area and increased capsular pressure → markedly reduced GFR → less filtrate → less urine produced.

Step 5 — Explain Elevated Creatinine Creatinine clearance ≈ GFR. If GFR is severely reduced, creatinine cannot be filtered and excreted at its normal rate → accumulates in blood → elevated serum creatinine.

Diagnosis: Post-streptococcal glomerulonephritis (Nephritic syndrome).

Treatment: Anti-inflammatory therapy, antibiotics if active infection, Na+ and fluid restriction, dialysis if GFR drops critically.

NEET Connection: This case tests: (1) post-streptococcal cause of glomerulonephritis, (2) haematuria as a sign of glomerular damage, (3) mechanism of oedema (oncotic pressure + Na+ retention), (4) oliguria from reduced GFR, (5) elevated creatinine from reduced GFR.