Interstitial nephritis is a kidney condition characterized by swelling in between the kidney tubules. The kidneys’ main function is to filter the blood. The kidney tubules are responsible for reabsorbing water and important organic substances from the kidney filtrate and secreting unneeded substances into the filtrate for urinary excretion. Swelling of these tubules can cause a number of kidney symptoms ranging from mild to severe.
Interstitial nephritis can be sudden (acute) or chronic. Acute interstitial nephritis (AIN) accounts for 10 to 15 percent of all hospitalizations due to kidney failure in the United States. (Abuhmaid, F. & Kumbar, L., 2011)
AIN is frequently the result of an allergic reaction. The majority of AIN cases (at least 70 percent) may be attributed to bad reactions to drugs. More than 100 different medications may trigger AIN. Many of these medications fall into the following categories:
- NSAIDs (nonsteroidal anti-inflammatory drugs)
- proton pump inhibitors (medications used to treat excess stomach acid disorders)
Allergic drug reactions are more severe in elderly patients. They are also more likely to cause permanent kidney damage. (Munar, M. & Singh, H., 2007)
Causes of no allergic interstitial nephritis include:
- autoimmune disorders, such as lupus erythematosus
- low blood potassium levels
- high blood calcium levels
- certain infections
Nonallergic interstitial nephritis may be either chronic or acute. Chronic forms may last several months or longer. They are usually caused by chronic underlying conditions.
The elderly are the main risk group for AIN. That is because they often take multiple medications. In addition, they may be confused about taking drugs in combination.
Other groups at high risk of interstitial nephritis include those who:
- chronically use over-the-counter pain relievers
- suffer from autoimmune diseases
- have sarcoidosis, an inflammatory disease of the lungs
The most common symptom of interstitial nephritis is a decrease in the amount a person urinates. In some cases, however, urine output may actually increase. (NIH, 2011) Other symptoms include:
- blood in the urine
- water retention, swelling
- weight gain (from water retention)
- feeling bloated
- elevated blood pressure
If your doctor suspects your kidneys are not functioning properly, a detailed medical history will be taken. You will be questioned about your family’s history of medical problems. You will also be asked about:
- which medications you take
- how often you take them
- how long you have been taking them
Make certain to tell your doctor about all drug use, including over-the-counter pain relievers and dietary supplements. These drugs can have significant impact on the kidneys.
Your doctor will also listen to your heart and lungs. Fluid in your lungs is a common sign of kidney failure. It can be detected by changes in breath sounds. High blood pressure is also a potential sign of kidney problems.
The following blood tests are used to evaluate kidney function:
- complete blood count (CBC)
- blood urea nitrogen (BUN)
- blood creatinine
- blood gases, which show the level of oxygen and carbon dioxide in the blood
Other tests that can be used to detect kidney problems include:
- kidney ultrasound
- kidney biopsy
If your physician suspects that your kidney problems are caused by a drug side effect or drug interaction, you may be asked to stop taking the suspected drug. In many cases, taking this measure will quickly return kidney function to normal.
Treatment for interstitial nephritis depends on the cause.
When AIN is caused by a drug allergy, the only treatment needed may be drug removal. Other cases of AIN can be treated with anti-inflammatory medications. Quick treatment often leads to a full recovery.
Some cases of interstitial nephritis cause permanent damage to the kidneys before they can be diagnosed. This damage requires treatment as well. Removing salt from the diet can improve water retention and high blood pressure. Following a low-protein diet may also help improve kidney function.
In severe cases, dialysis may be needed to support kidney function. People who experience kidney failure may need a transplant.