Diabetic Nephropathy (Diabetic Kidney Disease, DKD)

Proteinuria is a cardiac finding - Albuminuria is an independent risk factor for cardiovascular mortality, so protein on the urinalysis tells you as much about the heart as the kidney. Look for the coronary artery disease, hypertension, and peripheral vascular disease that travel with it, and for diabetic retinopathy on the eye exam — retinopathy and nephropathy run together, and its absence in type 1 diabetes makes DKD less likely.

Autonomic neuropathy - Look for resting tachycardia, orthostatic hypotension, painless myocardial ischemia, and loss of heart rate variability (normal variability during voluntary deep breathing at 6 breaths/min is more than 10 beats/min). A diabetic patient with hypertension has roughly a 50% chance of coexisting autonomic neuropathy. It blunts the heart's ability to compensate for volume shifts, so expect post-induction hypotension and an exaggerated pressor response to intubation, and expect intraoperative hypothermia.

Treat the stomach as full - Autonomic dysfunction slows the stomach and puts these patients at risk of aspiration, and it can involve the gut with no cardiac signs at all. Ask about early satiety. Premedication with an antacid and metoclopramide is prudent, particularly in an obese diabetic with signs of cardiac autonomic dysfunction.

Insulin dosing changes with the kidney - The kidney clears insulin, so as renal function falls insulin lingers and the dose has to come down or the patient goes hypoglycemic. The same is true of most renally cleared oral agents; be cautious below an eGFR of 45 and more so below 30.

Keep the perfusion pressure up - Autoregulation is already impaired in chronic renal disease, which magnifies the effect of any hypotension. The depth and duration of intraoperative hypotension track with postoperative AKI, and pre-incision hypotension is the preventable half.

Potassium and the ECG - Reduced renal excretion is a core mechanism of hyperkalemia, and the first test in a suspected case is an ECG, because conduction abnormalities and dysrhythmias are the lethal complication. The rate of rise matters more than the absolute number. In renal disease also check serum calcium — hypocalcemia worsens the cardiac effects of hyperkalemia.

Avoid the second hit - These kidneys are primed for acute kidney injury, so be deliberate about NSAIDs (interstitial nephritis) and IV contrast. Hydroxyethyl starch is not recommended when AKI risk is elevated, and a large 0.9% saline load produces hyperchloremia and reduces renal blood flow.

RAS blockade - Most of these patients are on an ACE inhibitor or ARB, prescribed to slow progression and cut proteinuria. Guideline pressure targets sit at less than 140/90, with diabetic society targets of 130/80. Know which agent they're on: RAS blockade affects renal autoregulation, and whether to hold it perioperatively is still debated.

Nephrotic-range disease - Once urine protein exceeds 3.5 g/day, expect hypoalbuminemia, pedal edema, and fatigue. That changes the volume picture and the tolerance for supine positioning.

Dialysis-dependent patients - Renal replacement therapy generally becomes necessary around a GFR of 10 to 15 mL/min. Find out whether they are on dialysis and when they last ran before you plan fluids or dose renally cleared drugs.

Diabetic nephropathy, or diabetic kidney disease (DKD), is the leading cause of end-stage kidney disease in the developed world and develops in 30% to 40% of patients with diabetes. Chronic hyperglycemia generates reactive oxygen species and advanced glycation end products and drives inflammatory signaling through IL-6, MCP-1, TGF-beta, and VEGF, producing fibrosis and increased vascular permeability. Podocytes are injured, albumin leaks, and the resulting systemic and intraglomerular hypertension worsens proteinuria and drives chronic tubular injury. The kidney shows Kimmelstiel-Wilson nodules, thickened glomerular basement membrane, and glomerulosclerosis.

Perioperatively the point is that DKD never travels alone. It marks a patient who also carries coronary artery disease, hypertension, peripheral vascular disease, and retinopathy — and a kidney whose autoregulation is already impaired.