What is interstitial nephritis?

Interstitial nephritis is a kidney condition characterized by swelling in between the kidney tubules.

The main functions of your kidneys are to filter your blood and to get rid of waste from your body. The kidney tubules reabsorb water and important organic substances from the filtered blood and secrete substances you don’t need into your urine for removal from your body. Swelling of these tubules can cause a number of kidney symptoms that range from mild to severe.

Interstitial nephritis can be acute (sudden) or chronic (long term).

The most common symptom of interstitial nephritis is a decrease in the amount a person urinates. In some cases, urine output may increase. At times, people can have no symptoms.

Other symptoms of interstitial nephritis include:

Acute interstitial nephritis (AIN) is frequently the result of an allergic reaction. Most cases of AIN are from bad reactions to drugs. More than 100 different medications may trigger AIN. Many of these medications fall into the following categories:

  • antibiotics
  • nonsteroidal anti-inflammatory drugs (NSAIDs), which are often used as pain relievers
  • proton pump inhibitors, which are medications used to treat excess stomach acid

Allergic drug reactions are more severe in older adults. They’re also more likely to involve permanent kidney damage in this group.

The causes of nonallergic interstitial nephritis include:

Nonallergic interstitial nephritis may be either chronic or acute. Chronic forms may last several months or longer. They’re usually caused by chronic underlying conditions.

Older adults are the main group that’s at risk for AIN. This 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 (OTC) pain relievers
  • have autoimmune diseases
  • have sarcoidosis, which is an inflammatory disease of the lungs

If your doctor suspects your kidneys aren’t functioning properly, they’ll take a detailed medical history. They’ll ask you about your family’s history of medical problems. They’ll also ask you:

  • which medications you take
  • how often you take them
  • how long you’ve been taking them

Make certain to tell your doctor about all drug use, including OTC 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, as well as weight changes.

The following blood tests are used to evaluate kidney function:

Other tests that can be used to detect kidney problems include:

If your doctor 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, 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.

Sometimes interstitial nephritis causes permanent damage to the kidneys before you can be diagnosed. This damage requires treatment as well. Removing salt from your diet can improve water retention and high blood pressure. Following a low-protein diet may also help improve kidney function.

If you have a severe case, dialysis may be needed to support kidney function. People who experience kidney failure may need a transplant.

The outlook for interstitial nephritis depends on what type you have and if any kidney damage was caused.

In most cases, you’ll make a full recovery if the allergic reaction or underlying condition is treated and no permanent kidney damage has been caused.