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.

Branch 2: The mechanism of progression

If asked why his kidney disease is worsening, the candidate should explain the hyperfiltration vicious cycle. Nephron loss from his dysplastic and scarred tissue forces the surviving nephrons to increase their individual filtration to preserve whole-organ function. Angiotensin two constricts the efferent arteriole more than the afferent, raising intraglomerular pressure, and the high-pressure overwork causes focal segmental glomerulosclerosis and proteinuria, which in turn destroys the compensating nephrons. This is why the disease accelerates once it has begun. [4]

The examiner may probe the therapeutic implication. The candidate should state that this mechanism is exactly why renin-angiotensin blockade works: an ACE inhibitor or ARB reduces efferent arteriolar tone, lowers intraglomerular pressure, and cuts albuminuria, breaking the loop. The candidate should also address why blood-pressure control matters at the glomerulus, linking systemic pressure to intraglomerular pressure and sclerosis.

Branch 3: The nephroprotective bundle

If asked to outline management, the candidate should present the bundle in priority order. First, rigorous blood-pressure control targeting a 24-hour mean arterial pressure below the 50th percentile for age, sex and height, confirmed on ambulatory monitoring, citing the ESCAPE trial as the evidence that this slows GFR decline in children with CKD. Second, an ACE inhibitor or ARB for his proteinuric CKD, with monitoring of creatinine and potassium and the caveat that a small rise on initiation is expected and acceptable. Third, elimination of reversible insults: prompt treatment of urinary tract infections, urological surveillance of his valve bladder (which may need anticholinergics or clean intermittent catheterisation), withdrawal of nephrotoxins, and avoidance of dehydration. [2]

The examiner may push on targets. The candidate should be precise: the blood-pressure target is below the 50th percentile, not simply normal, and it requires ambulatory monitoring to confirm because clinic readings miss nocturnal hypertension and blunted overnight dipping. The candidate should also volunteer that his complications, anaemia, acidosis, mineral-bone disease and growth failure, must each be controlled so he reaches end-stage kidney disease in the best condition, and that pre-emptive transplantation before dialysis is the goal, to be planned well before stage G5. [1]

If the examiner asks what might go wrong, the candidate should name the pitfalls: treating blood pressure to a normal-for-population target rather than the below-50th-percentile target, withdrawing the ACE inhibitor at the first small creatinine rise, missing the polyuric salt-wasting pattern of dysplastic kidneys, and failing to plan access and transplant work-up before G5 forces an emergency dialysis start. [4]