Disease, birth defects and injuries can all affect the kidneys’ ability to function. Diabetes frequently leads to a slow deterioration of the kidneys known as diabetic nephropathy. The end result of nephropathy is kidney failure, which is an inability to filter waste products or to regulate the body’s balance of salt and water.

More than 40 percent of all new cases of kidney failure are attributed to diabetes, according to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Nephropathy is more common in patients with type 1 diabetes but also occurs in those with type 2 diabetes (especially if diagnosed at a young age) and other forms of diabetes, such as maturity-onset diabetes of the young (MODY). Recent research shows that nephropathy can even affect people with prediabetes.

The damage associated with kidney disease occurs in and around the glomeruli, the tiny, globular vessels that serve as the blood-filtering units of the nephrons (the basic structure of the kidney). If the filtering efficiency of the glomeruli diminishes, then key blood proteins are lost to the urine. As the disease progresses, the kidneys lose their ability to remove waste products, including creatinine and blood urea nitrogen, from the blood.

Much of this damage can happen without the patient’s awareness. Symptoms often do not appear until the late stages of the disease, when kidney failure is a present danger. There are three kinds of kidney failure:

• Acute renal failure. The kidneys cease functioning properly because of a sudden illness, trauma, a medication or a medical condition. In some cases, this may go away on its own, with patients recovering within a few days. How long the illness lasts depends on the cause of the kidney problem.
  
  
• Chronic renal failure. Kidney function gradually declines, usually over a period of years. It is most often the result of illnesses such as diabetes, uncontrolled high blood pressure (hypertension) or chronic kidney inflammation.
  
  
• End-stage renal disease (ESRD). Kidney function declines until the point where the person will die without dialysis or a kidney transplant. This is usually the result of longstanding chronic renal failure, but can also follow acute renal failure.

Diabetes is the chief cause of kidney failure in the United States. More than 100,000 Americans are living with kidney failure brought on by diabetes, according to the NIDDK. Symptoms of the various forms of kidney failure include:

Acute kidney failure

• Fluid retention (edema)
• Confusion
• Seizures
• Coma

Chronic kidney failure

• High blood pressure
• Anemia
• Nausea or vomiting
• Malaise or fatigue
• Decreased urine output
• Unexplained weight loss
• Decreased alertness
• Sleep disorders
• Persistent itching
• Muscle twitches or cramps
• Headaches that appear unrelated to another cause
• Yellowish-brown cast to the skin

End-stage renal disease

• Anemia
• High blood pressure
• Congestive heart failure
• Bone disease
• Digestive tract problems
• Loss of mental function (dementia)

There are five stages that are generally recognized as belonging to the progression of nephropathy. It is important to note that acute kidney failure rarely progresses to ESRD. The five stages are:

• Stage I. The kidneys filter wastes at a level that is higher than normal. This process is known as hyperfiltration. Some patients remain at this level indefinitely, and others advance to the next stage after a period of years.
  
  
• Stage II. Filtration remains elevated, and damage to the glomeruli begins to appear. Small amounts of a blood protein called albumin can begin to leak into the urine. This condition is called microalbuminuria, and it usually becomes progressively worse. People with diabetes who maintain normal blood pressure and keep tight control over glucose (blood sugar) levels may remain in Stage II for years.
  
  
• Stage III. Also known as overt diabetic nephropathy, it occurs when albumin in the urine increases (a condition called proteinuria) and the kidneys’ ability to filter wastes usually begins to decrease, causing a buildup of wastes. High blood pressure is frequently a complication of this kidney damage. Increased levels of damage to the glomeruli are evident. Blood levels of creatinine and urea-nitrogen rise. Patients frequently remain at this stage for years.
  
  
• Stage IV. Kidney filtration is substantially impaired.  Large amounts of protein pass into the urine, and high blood pressure is almost always present. Levels of creatinine and urea-nitrogen in the blood continue to rise.
  
  
• Stage V. The final stage of kidney disease involves kidney failure as part of end-stage renal disease (ESRD). Filtration is seriously impaired, and the kidneys are unable to regulate the body’s balance of salt and water. Production of urine slows or stops. Waste products and water accumulate in the body, leading to a potentially life-threatening overload of these substances.

If damage becomes severe enough, patients may require either a kidney transplant or undergo dialysis treatment. Dialysis occurs in one of two forms:

• Hemodialysis.  A machine replaces the work of the kidneys by filtering blood. The cleaned blood is then returned to the body.
  

  

• Peritoneal dialysis. The lining of the patient’s abdomen (peritoneal membrane) is used as the filter. A catheter is surgically inserted through the wall of the abdomen, and a dialysis solution is introduced into the abdominal cavity. This solution removes waste products and excess fluids from the bloodstream.

Patients who undergo dialysis typically need to have the procedure done three times a week. Dialysis treatments continue until the kidneys start functioning normally again or until the patient receives a transplant.

Other kidney conditions include kidney stones (risk factors include type 2 diabetes, obesity and high blood pressure), infections, nephritis (inflammation, caused by conditions including lupus), nephrotic syndrome (a condition, sometimes caused by diabetic nephropathy, involving proteinuria, edema and high cholesterol) and polycystic kidney disease (genetic condition in which cysts form in the kidneys).