The kidneys are working throughout life to remove toxins and wastes from the bloodstream as well as balancing the fluid and electrolyte levels within healthy limits. These are essential processes for maintaining life. Both kidneys share this workload and each kidney does not have to function at full capacity all of the time. While the kidney can continue to function with minor damage, it can eventually reach a point where kidney function becomes impaired.
Impairment of kidney function may not always lead to obvious signs and symptoms. Many people with minor kidney damage may not even know of this problem. They may be largely asymptomatic. However, as the kidney damage becomes extensive and there is prolonged kidney impairment then various signs and symptoms will arise. This may include abnormal urine production, alterations in blood pressure and swelling of body parts.
Read more on signs of kidney failure.
Causes of Kidney Damage
Apart from obvious causes of kidney damage like trauma during a car accident or contact sports, there are many other causes of kidney damage. Some of these conditions are becoming common in the general population like diabetes, hypertension (high blood pressure) and high blood cholesterol. Kidney damage is one of many possible complications that arise in these conditions. Depending on the cause it can lead to acute kidney failure or chronic kidney disease.
Read more on strained kidneys.
Diabetes is one of the leading causes of kidney damage in developed nations. It is a result of long term diabetes, rarely arising before 10 years of having diabetes. However, it can arise earlier when there is poorly controlled diabetes. In fact about 3% of newly diagnosed type 2 diabetics already have kidney damage. It does not affect every diabetic but as many as 50% of diabetics having had diabetes for more than 20 years have kidney damage.
Diabetic kidney damage is known as diabetic nephropathy. The elevated blood glucose levels causes thickening of the membrane of the filtration units (glomeruli) of the kidney. There is also damage to the tiny blood vessels in the kidney. Ultimately these changes hamper the filtration of blood by the kidneys. It is further impacted by the high blood pressure and risk of infections which are more likely to arise with diabetes.
High Blood Pressure
High blood pressure (hypertension) is another leading cause of kidney damage. The persistently elevated blood pressure damages the blood vessels and filtration units of the kidney. This hampers the filtering of blood to remove wastes while stabilizing water and electrolyte levels. In fact the kidneys play a central role in regulating blood pressure and high blood pressure can damage this function of the kidney.
High blood pressure is on the rise globally but especially in developed countries. It is closely associated with the rise in obesity, high sodium intake in processed foods, other dietary factors and a sedentary lifestyle. A family history of hypertension is another major risk factor. However, the majority of blood pressure cases are primary hypertension where this elevation is not due to any underlying disease. The exact cause of primary hypertension is unknown.
High Blood Cholesterol
Another common condition that can cause kidney damage is high blood cholesterol. It narrows the arteries that carry blood to the kidneys and slowly impairs kidney function. In addition high blood cholesterol may contribute to high blood pressure and diabetes as well as being caused by these conditions. Collectively, all of these conditions eventually damage the kidneys
High blood cholesterol occurs due to a combination of factors. Some of these are modifiable, meaning that it can be controlled or prevented, such as a sedentary lifestyle, poor dietary habits and being overweight or obese. Other factors are non-modifiable, such as genetics. In the early stages, reversing high blood cholesterol may prevent any permanent damage to the kidneys.
Urinary Tract Obstruction
Any obstruction to the passage of urine can lead to kidney damage. This blockage may be due to kidney stones, prostate enlargement (men), blood clots and tumors, including both benign (non-cancerous) and malignant (cancerous) tumors such as bladder, prostate and colon cancer. Diseases or damage of the nerves that control the bladder can also cause an obstruction if the bladder cannot be emptied.
Polycystic Kidney Disease
Polycystic kidney disease is an uncommon chronic kidney condition where clusters of cysts develop in the kidney. It is due to genetic defects and therefore often runs in families. These cysts may also develop in other organs like the liver. Some people have no symptoms but it depends on the severity of the condition. Polycystic kidney disease can lead to hypertension (high blood pressure) which in turn can cause further kidney damage.
Infections of the kidney (pyelonephritis) can be serious and severe. Mostly urinary infections are limited to the urinary tract and particularly the urethra and bladder (UTIs). However, these infections may ascend up the ureter to the kidneys. Sometimes the infectious agent, like bacteria, may reach the kidney through the bloodstream or even spread directly from neighboring organs. Prompt treatment will usually prevent permanent kidney damage.
There are conditions where the kidney can become inflamed without any infection. Two such conditions are glomerulonephritis and interstitial nephritis. Glomerulonephritis is where the tubules of the kidney are inflamed where as interstitial nephritis is where the tissue between the tubules becomes inflamed. These conditions may occur due to the use of certain drugs, autoimmune diseases, diabetes and allergic reactions. Infections can also be a cause.
- Allergic reactions including drug allergies and severe reactions such as anaphylaxis.
- Autoimmune disease like systemic lupus erythematosus (SLE).
- Blood clots and blood disorders like thrombotic thrombocytopenic purpura and hemolytic uremic syndrome.
- Blood loss from severe injuries or following major surgery.
- Cancers that may cause urinary obstructions (discussed above) or blood cells like multiple myeloma.
- Chronic conditions like heart disease, liver failure or scleroderma.
- Drugs like aspirin, acetaminophen, certain antibiotics, ibuprofen and lithium among other drugs.
- Fluid loss which may occur with conditions that cause severe diarrhea and vomiting.
- Kidney tumors, including benign (non-cancerous) and malignant (cancerous) tumors.
- Toxins including alcohol in excess, illicit drugs and heavy metals.