Diabetic Nephropathy Quiz

See Clinical Signs and Symptoms. Option B is correct: microalbuminuria, also called moderately increased albuminuria, is the earliest clinical marker of diabetic nephropathy. It means a small but abnormal leak of albumin (the main protein in blood) into the urine, between 30 and 300 mg a day. High pressure and flow inside the glomerulus (the kidney's filtering tuft of capillaries) thicken the glomerular basement membrane, the thin sheet the filtrate must cross, and expand the mesangium, the supporting tissue between the capillary loops. The barrier then lets a little albumin through while the overall filtering rate is still normal or even raised. A routine urine dipstick usually only detects protein above about 300 mg of albumin a day, so this early leak is found with a urine albumin to creatinine ratio instead. Spotting it matters because tight glucose and blood pressure control and blocking the renin-angiotensin-aldosterone system (RAAS, the hormone pathway that raises blood pressure and glomerular pressure) can slow what follows. The exam trap is choosing a feature that is easy to see but late. Overt proteinuria and a falling GFR (the volume of plasma the glomeruli filter each minute) come afterwards. Memory aid: the filter leaks before it fails.

• Earliest marker: Microalbuminuria, a leak of 30 to 300 mg of albumin a day.
• Mechanism: High glomerular pressure thickens the basement membrane and expands the mesangium, so a little albumin leaks.
• Detection: A urine albumin to creatinine ratio, because a dipstick usually misses it.
• Timing: Overt proteinuria and a falling GFR come afterwards.