As in hyperfiltration, some people may develop microalbuminuria but not progress to later stages of kidney disease, especially if it is caught and treated early. However, even if nephropathy does not develop, the presence of microalbuminuria is itself a risk factor for cardiovascular diseases in people with Type 2 diabetes.
In the third stage (sometimes called overt diabetic nephropathy or nephrotic syndrome), large amounts of albumin spill into the urine (a condition called macroalbuminuria), which can be detected even on routine urine tests. As more albumin passes into the urine, less remains in the bloodstream. Since these proteins normally help to retain fluid in the bloodstream, their loss allows fluid to begin leaking out of the arteries and capillaries. This fluid tends to build up in the tissues, a condition known as edema. Excess fluid can collect in the legs and feet and later even in the chest (pleural effusion), around the heart (pericardial effusion), and in the abdomen (ascites), causing symptoms such as fatigue, chest pain, and shortness of breath. Also at this stage, people tend to develop high blood pressure if they do not have it already (people who already have high blood pressure will find it worsens).
In the fourth stage, called advanced clinical nephropathy, the kidneys can no longer remove most of the body’s waste products. Toxins begin to build up in the bloodstream, and anemia (low red blood cell count) may develop, causing fatigue.
In the fifth stage, called kidney failure, the kidneys barely function at all, causing uremia, the buildup of urea and other waste products in the blood. Uremia causes symptoms such as nausea, vomiting, and fatigue. In 50% of people who have Type 1 diabetes and overt nephropathy, kidney failure develops within 10 years. Among people with Type 2 diabetes and overt nephropathy, 20% progress to kidney failure in 20 years. People with kidney failure require dialysis, a treatment that takes over the function of the kidneys by filtering waste products and removing water from the blood. In some cases, people with kidney failure can get a kidney transplant, but most must wait for a long time for a suitable donor kidney to become available.
If you work with a nephrologist (a physician who specializes in kidney diseases) to treat problems with diabetic nephropathy, he may refer to different stages than the ones described here because the National Kidney Foundation (NKF) has its own five-stage classification system for chronic kidney disease. The NKF bases its system on kidney filtering function alone, so it does not differentiate between the initial causes of the kidney disease. In the NKF’s model, people with diabetic nephropathy who show microalbuminuria would usually be grouped in “stage 1 chronic kidney disease.” Kidney failure occurs in “stage 5 chronic kidney disease.”
One of the best screening tools for the earliest stages of diabetic kidney disease is the urine microalbumin test, which can be done in one of three ways and also involves a check of urinary creatinine levels. (Creatinine is a by-product of normal muscle breakdown.) To monitor your albumin levels, your health-care team can order a one-time in-office check of urine (a “random spot collection,” often done first thing in the morning), a 24-hour urine collection (analyzing all the urine you produce in 24 hours), or a timed collection (analyzing all the urine you produce over a certain number of hours). The 24-hour sample is supposed to give the most accurate results (and may still be recommended for certain people with unusual protein intakes or extreme muscle loss), but because it can be a hassle and because the shorter tests offer good accuracy when corrected by checking creatinine levels, many health-care providers simply use the shorter tests. (Several companies sell home test kits that allow people to mail urine samples to a laboratory for microalbumin testing; however, you should discuss this option with your health-care team before trying one.)