Interstitial nephritis is a disease that causes inflammation (swelling) and scarring around parts of your kidneys' filters called the tubules or renal tubules. The renal tubules are tiny tubes that filter blood and return nutrients and fluids back to the body. The remaining fluid and waste in the tubules become urine.
'Interstitial' means that the inflammation does not affect the blood vessels or filters in the kidney, but only the parts in between them.
Swelling of these renal tubules can cause a number of kidney symptoms that range from mild to severe. Interstitial nephritis can be acute (sudden) or chronic (long term).
There are two kinds of interstitial nephritis:
Acute interstitial nephritis, which lasts a short time. This is the most common type of interstitial nephritis.
Chronic interstitial nephritis, which lasts longer: weeks, months or years.
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:
A fever
Blood in the urine
Mental status changes (drowsiness, confusion, exhaustion)
Fatigue
Nausea, vomiting
A rash
Water retention
Swelling in your hands, feet or other parts of your body
Weight gain from water retention
Feeling bloated
Elevated blood pressure
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
Over-the-counter pain medicines called nonsteroidal anti-inflammatory drugs (NSAIDs), which are often used as pain relievers
Long-term use of medicines such as acetaminophen (Tylenol), aspirin, and nonsteroidal anti-inflammatory drugs (NSAIDs). This is called analgesic nephropathy.
Side effect of certain antibiotics such as penicillin, ampicillin, methicillin, and sulfonamide medicines.
proton pump inhibitors (PPIs), 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:
Autoimmune diseases (diseases that cause your body's immune system to attack its own tissues) such as lupus erythematosus, anti-tubular basement membrane disease or Kawasaki disease
low blood potassium levels
high blood calcium or uric acid levels
Sarcoidosis (a disease that causes inflammation, most commonly in the lungs and lymph nodes)
certain infections
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 a 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:
A complete blood count
A blood urea nitrogen test
A blood creatinine test
A blood gas test, used to check an acid-base imbalance and the levels of oxygen and carbon dioxide in the blood
Other tests that can be used to detect kidney problems include:
Urinalysis
Abdominal ultrasound
Kidney biopsy
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. Limiting salt and fluid in the diet can improve swelling due to water retention and high blood pressure. Limiting protein in the diet can help control the buildup of waste products in the blood (azotemia), which can lead to symptoms of acute kidney failure.
If you have a severe case, dialysis may be needed to support kidney function.
In most cases, some scarring develops in the kidneys, causing permanent damage. However, this may remain stable for years without causing problems. In some cases, however, the kidneys are so badly damaged that they fail completely and dialysis will need to be considered.
No. Although interstitial nephritis can be triggered by a viral infection, it is not infectious because the problem is your body's reaction to the infection, not the type of infection itself. So, if your partner or a family member has the same infection that triggered your interstitial nephritis, they will not get interstitial nephritis themselves.
It is extremely rare for interstitial nephritis to run in families.
This is unusual - most people have a single attack and the kidneys then stabilise. If the kidneys are badly damaged by the first attack, they can wear out even if the original disease does not come back. If a drug has caused the interstitial nephritis, it is very important not to take the drug again. Remember the name of the drug, and always tell doctors about your kidney disease and the drug reaction you have had.
Most people with interstitial nephritis continue to lead normal lives. Although there can be some sickness in the early stages of the condition, this normally settles and there is no chronic pain. It may be necessary to take medication for problems such as high blood pressure. Severe kidney damage or dialysis treatment will obviously affect your lifestyle, but it is possible to cope with these serious problems very well.