How can diabetes lead to microalbuminuria?

Kidney damage: Uncontrolled diabetes primarily affects the kidneys in that it causes damage to the gromerular membrane which serves as filter in the kidneys. Initial subtle damage results in increased permeability of the membrane, through which the finest Albumin particles known as microalbumin is expelled in the urine.

Damage: By damaging the "filtering" system in the kidneys by causing "hardening of the arteries" of the filtering system. Microalbumin is important because it can be the earliest sign that the diabetes is starting to harm the kidney. Aggressive treatment when this is noted can save your kidneys and save your life. Most all adult onset diabetics have some degree of microalbumin in the urine.