Chronic kidney disease and progression: Viva

Branch 1: Definition, staging and GFR estimation

The candidate should define chronic kidney disease as abnormalities of kidney structure or function present for more than three months, with either a glomerular filtration rate below 60 mL per minute per 1.73 square metres or markers of kidney damage such as albuminuria, abnormal sediment, tubular disorders, structural abnormalities, transplantation history, or inherited or cystic disease. A strong candidate should then estimate this boy's GFR using the bedside Schwartz equation, 0.413 multiplied by height in centimetres divided by creatinine in mg per dL, yielding about 39 mL per minute per 1.73 square metres, which is GFR category G3b. His albumin-to-creatinine ratio of 85 mg per g is category A2, so he sits in a higher-risk cell of the KDIGO grid. ^[3]

If the examiner presses on why albuminuria matters so much, the candidate should explain that albuminuria is the single strongest predictor of progression because it is both a marker of glomerular damage and a mechanism of further injury: filtered protein taken up by proximal tubular cells triggers inflammation and interstitial fibrosis, destroying the nephrons that are compensating. A rising ratio is therefore a signal to intensify renin-angiotensin blockade, not to watch and wait. ^[4]

If asked to distinguish this from acute kidney injury, the candidate should note the chronic context of his congenital valve disease and reflux, the duration of his decline over years, and the presence of complications such as acidosis and growth failure that point to chronicity, while remaining alert to reversible insults that may have acutely worsened his function.