Chronic kidney disease and progression: SAQ

This boy has chronic kidney disease from reflux and dysplastic change related to posterior urethral valves, and his numbers show progression with complications. Using the bedside Schwartz equation, his estimated GFR is 0.413 multiplied by 128 divided by 1.36, which is about 39 mL per minute per 1.73 square metres, placing him in GFR category G3b. His albumin-to-creatinine ratio of 85 mg per g is category A2 (moderately increased), which puts him in a higher-risk cell of the KDIGO grid and marks albuminuria as the modifiable target most closely linked to his decline. [3]

Question 1 (10 marks)

Outline your nephroprotective management to slow the progression of his kidney disease, including blood-pressure target, drug therapy, and the reversible insults you would address. [2]

The overriding principle is that every millilitre of GFR preserved is a millilitre the child does not need to replace with dialysis. The strongest evidence-based intervention is rigorous blood-pressure control. I would target a 24-hour mean arterial pressure below the 50th percentile for his age, sex and height, confirmed on ambulatory blood-pressure monitoring, because the ESCAPE trial showed that this strict target slowed the decline in GFR in children with CKD compared with a conventional higher target. His clinic blood pressure of 118 over 78 in a 7-year-old is above the 50th percentile and likely elevated, so I would arrange ambulatory monitoring to characterise it and confirm the target. [2]

For drug therapy I would start an angiotensin-converting enzyme inhibitor or angiotensin receptor blocker as first-line, because he has proteinuric CKD and these agents lower efferent arteriolar tone, reduce intraglomerular pressure, and cut albuminuria, interrupting the hyperfiltration vicious cycle that drives his decline. An example is enalapril at a starting dose of 0.1 mg per kg per day, titrated. I would warn the family that a small rise in creatinine and potassium is expected on initiation and does not automatically require cessation, but I would monitor both, and I would avoid these drugs in bilateral renal artery stenosis. [4]

I would address the reversible insults. Urinary tract infections must be treated promptly and considered for prophylaxis given his reflux and valves. Bladder function should be assessed urodynamically, because valve bladders often develop high storage pressures that back-pressure the upper tracts; he may need anticholinergics or clean intermittent catheterisation. I would withdraw non-steroidal anti-inflammatory drugs and other nephrotoxins, and ensure he is not dehydrated, because intravascular depletion worsens function. His dietitian would address sodium and phosphate restriction appropriate to his stage. [4]

Question 2 (10 marks)

Describe your management of his growth failure, anaemia, acidosis and mineral-bone disease, including the thresholds and targets you would use and the order in which you would intervene. [1]

For growth failure I would take a stepped approach. The first step is to correct the reversible drivers, because recombinant growth hormone only works well once these are addressed. His bicarbonate of 18 mmol per litre shows chronic metabolic acidosis, which dissolves bone and impairs growth; I would start oral sodium bicarbonate, typically 1 to 3 mmol per kg per day in divided doses, to maintain his bicarbonate at 22 mmol per litre or above. His haemoglobin of 96 g per litre is below the range at which anaemia of CKD is treated; I would check his iron studies and give oral elemental iron at 2 to 3 mg per kg per day, adding an erythropoiesis-stimulating agent if haemoglobin remains low despite adequate iron, to target 100 to 120 g per litre. I would also optimise his nutrition, which may require supplemental feeding. [5]

For his mineral-bone disease, his parathyroid hormone at three times the upper limit of normal with a phosphate of 1.7 mmol per litre indicates secondary hyperparathyroidism. I would measure his 25-hydroxyvitamin D and give native cholecalciferol to correct deficiency, because normal vitamin D levels are associated with less proteinuria and slower progression. I would apply dietary phosphate restriction and a phosphate binder, choosing a calcium-based binder such as calcium carbonate when the calcium-phosphate product allows, and I would add an active vitamin D analogue such as calcitriol to suppress parathyroid hormone, titrating to keep it within roughly two to nine times the upper limit of normal for his stage. [1]

Only after anaemia, acidosis, mineral-bone disease and nutrition are corrected would I consider recombinant human growth hormone, because his height has fallen across centiles despite these measures being addressed. The recommended dose is 28 IU per square metre per week, equivalent to about 0.05 mg per kg per day, given as a daily subcutaneous injection, and it improves growth velocity and final height in children with CKD whose growth remains impaired. I would also begin planning for the future: given his trajectory toward end-stage kidney disease, I would initiate transplant work-up and living-donor evaluation well before he reaches stage G5, because pre-emptive transplantation offers the best survival, growth and quality of life. [5]