Diabetic Nephropathy

Diabetic Nephropathy (DN) is a clinical syndrome of albuminuria and declining renal function occurring in patients with long-standing Diabetes Mellitus (Types 1 or 2). It is the most common cause of ESRD in developed countries. The condition progresses through stages: Initially, there is glomerular hyperfiltration, followed by 'microalbuminuria' (ACR 3-30 mg/mmol), then 'macroalbuminuria' (ACR >30 mg/mmol), and finally a fall in eGFR. Pathologically, it is defined by glomerular basement membrane thickening, mesangial expansion, and pathognomonic Kimmelstiel-Wilson nodules on biopsy. Importantly, DN is almost always associated with diabetic retinopathy; if a patient has nephropathy but no retinopathy, an alternative cause for renal disease should be suspected. Management focuses on multi-factorial risk reduction: HbA1c control to <53 mmol/mol, blood pressure control (<130/80), and the use of ACE inhibitors or ARBs (regardless of BP if albuminuria is present). Recently, SGLT2 inhibitors (e.g., Dapagliflozin) have become a cornerstone of treatment due to their profound renoprotective effects and reduction in heart failure risk.

The pathogenesis of DN involves chronic hyperglycaemia leading to several damaging pathways. 1. Haemodynamic Factors: High glucose levels lead to afferent arteriole vasodilation and efferent arteriole vasoconstriction (mediated by Angiotensin II), causing glomerular hyperfiltration and hypertension. 2. Metabolic Factors: Hyperglycaemia leads to the formation of Advanced Glycation End-products (AGEs) and activation of Protein Kinase C, which increase oxidative stress. 3. Cytokine Activation: TGF-beta is upregulated, stimulating mesangial cells to produce extracellular matrix, leading to mesangial expansion and glomerulosclerosis. Morphologically, this manifests as thickening of the glomerular basement membrane and the development of nodular glomerulosclerosis (Kimmelstiel-Wilson nodules). This damage increases the permeability of the glomerular filter to albumin.

DN is a silent killer, often asymptomatic until late CKD. The earliest clinical indicator is an elevated Albumin:Creatinine Ratio (ACR) on screening. As it progresses, patients may develop nephrotic-range proteinuria and subsequent peripheral oedema. Hypertension usually develops or worsens as renal function declines. Because DN is a microvascular complication, most patients will also have evidence of peripheral neuropathy (loss of sensation, foot ulcers) and retinopathy (visual loss). If a diabetic patient presents with rapid renal decline or haematuria without retinopathy, consider an alternative 'intrinsic' renal disease. Complications include accelerated atherosclerosis (MI/Stroke) and the development of uraemic symptoms in Stage G5 (nausea, itching, fatigue).

Bedside: Annual urine ACR (first-void); BP check. Bloods: eGFR, U&Es, HbA1c. Monitoring: Annual screening from diagnosis in Type 2, and 5 years post-diagnosis in Type 1. Imaging: Renal ultrasound (kidneys are typically normal or large in DN, unlike other CKD where they are small). Special: Renal biopsy (rarely needed unless features are atypical, such as absence of retinopathy or sudden onset).

Medical: 1. Renoprotection: ACE inhibitor (e.g., Ramipril) or ARB (e.g., Losartan) should be started if ACR >3 mg/mmol, even if normotensive. Do not combine ACEi and ARB. 2. SGLT2 Inhibitors: (e.g., Dapagliflozin or Canagliflozin) for ACR >30 mg/mmol or eGFR decline, as per NICE TA. 3. BP Control: Aim for <130/80 mmHg. 4. Glycaemic Control: HbA1c target usually 48-53 mmol/mol (tailor if at risk of hypos). 5. Lipids: Atorvastatin 20mg for primary prevention. Conservative: Smoking cessation, weight management, and sodium restriction. End-stage: Referral for RRT (dialysis/transplant) when appropriate.