Diabetic kidney disease — UACR interpretation, modern four-pillar therapy, and SGLT2i euglycaemic DKA viva

Interpretation

The examiner presents the annual review of a 56-year-old man with a 12-year history of type 2 diabetes and asks: "His UACR is 145 mg/g on two of three samples, eGFR 62, BP 140/86, HbA1c 8 percent. The dipstick is negative for protein. Walk me through your interpretation and your management plan." ^[1]

• Albuminuria. A UACR of 145 mg/g is microalbuminuria (A2, 30 to 300 mg/g) — confirmed by two of three samples over 3 to 6 months. The dipstick is negative because it does not detect microalbuminuria (it becomes positive only once UACR exceeds roughly 300 mg/g). This is the earliest clinically detectable marker of DKD and the therapeutic window.^[1]
• Staging. KDIGO G2/A2 = moderate risk for progression. The natural history is glomerular hyperfiltration -> microalbuminuria -> macroproteinuria -> declining GFR -> ESKD (Mogensen stages I-V); this patient is at Mogensen Stage III (incipient nephropathy).^[1]
• Diagnosis. Classical DKD: long-standing T2DM + retinopathy + microalbuminuria — no atypical features to mandate biopsy.

Key points

The examiner will probe each of these; be ready to defend them at viva depth:

1. Definition and classification — DKD = commonest single cause of ESKD worldwide; histological hallmark = Kimmelstiel-Wilson nodules (nodular glomerulosclerosis); KDIGO albuminuria categories A1/A2/A3 and GFR categories G1-G5 heat-map.^[1]
2. Pathophysiology — three axes: haemodynamic (hyperglycaemia -> RAAS -> efferent arteriolar constriction -> intraglomerular hypertension -> hyperfiltration); metabolic (AGEs, PKC, polyol, hexosamine -> ROS -> TGF-beta/CTGF); structural (basement membrane thickening, mesangial expansion, Kimmelstiel-Wilson nodules, arteriolar hyalinosis of BOTH afferent and efferent arterioles).
3. Screening — T2DM annually from diagnosis; T1DM 5 years after diagnosis (or puberty, whichever first), with UACR + eGFR.^[1]
4. Four-pillar combination therapy (R-S-F-M mnemonic):^[3][5][9]
   • RAAS blockade — ACE inhibitor (e.g., ramipril 10 mg) or ARB (losartan 100 mg, irbesartan 300 mg) at max tolerated dose; first-line only in albuminuric DKD; never combine ACEi + ARB (ONTARGET); a creatinine rise under 30 percent is benign.
   • SGLT2 inhibitor — dapagliflozin 10 mg, empagliflozin 10 mg, or canagliflozin 100 mg daily; disease-modifying, glucose-independent down to eGFR 20; mechanism = restore tubuloglomerular feedback -> afferent constriction -> lower intraglomerular pressure. Trials: CREDENCE (canagliflozin, T2DM), DAPA-CKD (dapagliflozin, mixed), EMPA-KIDNEY (empagliflozin, broad CKD).^[3][5]
   • Finerenone — non-steroidal MRA; 10 mg daily if eGFR 25-60, 20 mg if eGFR over 60, titrate to 20 mg at 4 weeks if potassium under 4.8 mmol/L; FIDELIO-DKD 18 percent kidney-outcome reduction; do not combine with steroidal MRAs.^[9]
   • Multifactorial — HbA1c individualised (~7 percent / 53 mmol/mol; relax in advanced CKD); BP under 130/80 in albuminuric DKD; statin in all diabetics with CKD aged 40-75; smoking cessation; diet (protein 0.8 g/kg/day, sodium under 2 g/day); exercise; Steno-2 21-year follow-up gained a median of 7.9 years of life.
5. Diabetes drug choice as eGFR falls — metformin dose-reduce to 1000 mg/day at eGFR 30-45 and stop below 30; avoid glibenclamide (hypoglycaemia) and saxagliptin/alogliptin (heart failure); GLP-1 RA (liraglutide, semaglutide, dulaglutide) preferred second-line; insulin doses reduced 25-50 percent as eGFR falls.
6. Biopsy indications — short diabetes duration, absent retinopathy (strong in T1DM), rapid GFR decline, haematuria, sudden heavy proteinuria, over 30 percent eGFR fall on ACEi/ARB, systemic features.
7. SGLT2i euglycaemic DKA — glucose often under 14 mmol/L; triggers: fasting, acute illness, surgery, very low carbohydrate intake; management: stop the drug, IV fluids, IV insulin with co-infused dextrose, treat the precipitant.^[3]
8. The triple whammy — NSAID + ACEi/ARB + diuretic -> AKI; avoid NSAIDs in any CKD patient.

Escalation questions

• "How would your plan change if his eGFR fell to 28 with potassium 5.3?" — Continue SGLT2i (benefit persists to eGFR 20); consider finerenone if potassium tolerable (under 4.8 ideally); address hyperkalaemia (dietary potassium, bicarbonate if acidotic, patiromer or SZC); continue RAAS unless potassium over 6.0; refer to nephrology for RRT planning. ^[1]
• "When do you initiate dialysis?" — When eGFR is under 10 with symptoms or complications (fluid overload refractory to diuretics, hyperkalaemia, metabolic acidosis, uraemic symptoms). Plan AV fistula at eGFR under 20.
• "If he develops atrial fibrillation?" — Continue SGLT2i (cardiorenal benefit, may reduce AF); statin already on; DOAC (apixaban preferred in CKD) dose-adjusted to eGFR over warfarin.

References

1. Thomas MC, et al. Diabetic kidney disease. Nat Rev Dis Primers 2015.^[1]
2. Perkovic V, et al. CREDENCE — Canagliflozin. N Engl J Med 2019.^[3]
3. EMPA-KIDNEY Collaborative Group. N Engl J Med 2023.^[5]
4. Bakris GL, et al. FIDELIO-DKD — Finerenone. N Engl J Med 2020.^[9]

References4ShowHide

1. [1]Thomas MC, Brownlee M, Susztak K, et al. Diabetic kidney disease. Nature Reviews Disease Primers, 2015.PMID 27188921
2. [3]Perkovic V, Jardine MJ, Neal B, et al. CREDENCE — Canagliflozin and Renal Outcomes in Type 2 Diabetes and Nephropathy. New England Journal of Medicine, 2019.PMID 30990260
3. [5]Herrington WG, Staplin N, Wanner C, et al. Empagliflozin in Patients with Chronic Kidney Disease. New England Journal of Medicine, 2023.PMID 36331190
4. [9]Bakris GL, Agarwal R, Anker SD, et al. Effect of Finerenone on Chronic Kidney Disease Outcomes in Type 2 Diabetes. New England Journal of Medicine, 2020.PMID 33264825