🩺 Diabetic Nephropathy
Kidney disease caused by diabetes – stages, pathophysiology, and evidence‑based management.
📊 Overview
Approximately 20% to 40% of patients with type 1 or type 2 diabetes mellitus develop diabetic kidney disease. This clinical syndrome is characterised by:
- Persistent albuminuria (> 300 mg/24 h, or > 300 mg/g creatinine)
- Relentless decline in glomerular filtration rate (GFR)
- Raised arterial blood pressure
- Enhanced cardiovascular morbidity and mortality
- Characteristic histopathology
📈 Natural History & Clinical Course
- First clinical sign: moderately increased urine albumin excretion (microalbuminuria: 30–300 mg/24 h or 30–300 mg/g creatinine; albuminuria grade A2).
- Untreated microalbuminuria worsens to clinical proteinuria (grade A3) over 5–15 years.
- GFR then begins to decline; without treatment, end‑stage kidney failure results in 5–7 years.
- First symptom is usually peripheral oedema – appears at a very late stage.
- Regular systematic screening is essential: annual urinary albumin‑to‑creatinine ratio, eGFR, and blood pressure monitoring.
📚 Stages of Diabetic Nephropathy
Stage One – Renal hyperperfusion and hypertrophy. Starts with diabetes onset before insulin treatment. Changes partly reversible with insulin. GFR increased.
Stage Two – Clinical silence with morphological changes (glomerulosclerosis). GFR still higher than normal. Normal albumin excretion with good glycaemic control; exercise or poor control may unmask albuminuria. Some patients remain in this stage lifelong.
Stage Three – Incipient nephropathy. Microalbuminuria (UAE >30 mg/d, >20 μg/min, or ACR >30 mg/g). Initially GFR increased, then begins consistent decline. Progression to overt nephropathy as UAE exceeds 300 mg/d or ACR >300 mg/g.
Stage Four – Overt nephropathy. Progressive blood pressure rise. Without antihypertensive treatment, GFR declines ~1 mL/min/month. Long‑term BP treatment reduces fall rate by ~60%, postponing uraemia considerably.
Stage Five – End‑stage kidney failure (uraemia). Up to 25% of the ESKD population have diabetic nephropathy as cause.
Diagram: Progression of diabetic nephropathy
🛠️ Management of Diabetic Nephropathy
- Control of blood pressure (target <130/80, lower if proteinuria)
- Control of blood sugar (individualised HbA1c target)
- Quitting smoking
- Dietary salt restriction
- Hypolipidemic treatment (statins)
- Treatment of hyperuricemia
- Phosphate handling (low phosphate diet, binders)
💊 Approved Interventions to Prevent Progression
| Drug class | On‑target action | Off‑target actions | Remarks |
|---|---|---|---|
| Antihypertensive RAS blockers | Blood pressure control | UAE↓, GTP↓, K⁺↑, AT1-7↑, cytokines↓, Klotho↑ | Failed to prevent DN; can accelerate progression in advanced CKD & old age |
| Blood sugar control | Normalise blood sugar | UAE↓, incident CKD↓, CKD progression↓ | Hypoglycaemia increases morbidity/mortality risk (especially with SU & insulin) |
| Metformin | – | AMPK↑, mTOR↓ | ↓ dose by 50% if GFR<60 mL/min; stop if GFR<30 |
| Pioglitazone | – | UAE↓, NF‑κB↓, CKD progression↓ | Salt/water retention, osteopenia, weight gain |
| GLP‑1 agonists | – | BW↓, UAE↓, ROS↓, TGF‑β1↓, CCN2↓ | Nausea, vomiting; stop if GFR<30 |
| DPP‑4 inhibitors | – | UAE↓, ROS↓, CCN2↓, EndMT↓, CKD progression↓ | Hypoglycaemia less likely; dose adjust except linagliptin |
| SGLT2 inhibitors | – | Hyperfiltration↓, BW↓, BP↓, UA↓, ROS↓ | Stop if GFR<30 |
| Statins | ↓ Serum cholesterol | ↓ CVD | No effect on stroke, CKD progression, or mortality |
| Quitting smoking | – | ↓ DN progression | – |
| Diet: salt restriction | ↓ BP, ↓ UAE | ↓ DN progression | Salt paradox in very low salt |
| Protein restriction | ↓ DN progression | – | Of value only in type 1 DM |
| Hypouricemic agents | ↓ UA | ↓ UAE, ↓ DN progression | – |
| Phosphate handling (↓P intake + sevelamer) | ↓ Serum P | ↓ DN progression, ↓ mortality | – |
| HCO₃ supplement | Treat acidosis | ↓ DN progression | May ↑BP, may ↑ oedema |
| Pentoxifylline | RBC rheology | ↓ UAE, ↓ DN progression | 1200 mg/day |
| Sarpogrelate | ↓ thromboxane A2 | ↓ UAE, ↓ MCP1 | – |
| Paricalcitol | ↓ PTH | ↓ UAE | – |
UAE = urinary albumin excretion; GTP = glomerular filtration rate? (likely GFR); AT1-7 = angiotensin 1‑7; ROS = reactive oxygen species; EndMT = endothelial‑to‑mesenchymal transition; UA = uric acid.