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WHAT IS INTERSTITIAL NEPHRITIS?

Interstitial nephritis is a condition where there is inflammation within the kidneys. It is the same in both kidneys, and can only be seen under the microscope. There is swelling and scarring inside the kidneys, although this is not usually painful. 'Interstitial' means that the inflammation does not affect the blood vessels or filters in the kidney, but only the parts in between them. Nephritis means kidney disease.

WHAT CAUSES INTERSTITIAL NEPHRITIS?

1. THE IMMUNE SYSTEM

Interstitial nephritis is caused by the body’s immune system (natural defences). The usual job of the immune system is to fight invaders into the body. These might be germs or bugs, or foreign objects such as splinters. The body recognises these invaders, and tries to eliminate them from the body. The blood contains two main types of defence system. One is white blood cells, which stick to germs and kill them. The other type of defence is antibodies, which are smaller than the white blood cells, and by sticking onto germs either make them burst apart, or help the white blood cells to stick to them.

The immune system is very powerful, and is normally very good at recognising what is part of the body and what is not. However, sometimes it makes a mistake and attacks the body as if that part of the body was an invader. There are many different diseases caused by the immune system, and they can affect any part of the body. There are several kidney diseases caused by the immune system. Some of them affect only the kidneys, some can affect other parts of the body as well as the kidneys.

It is not clear why the immune system causes diseases such as interstitial nephritis. There may be some trigger that makes the immune system go wrong, such as an infection or stress. Sometimes, interstitial nephritis can be caused by a drug. Often it is not known why interstitial nephritis occurs.

2. INFECTIONS AND OTHER CAUSES OF INTERSTITIAL NEPHRITIS

Some infections, including tuberculosis, can cause interstitial nephritis, and doctors will test for this and other infections in patients. Rarely, interstitial nephritis can be seen with diseases that affect other parts of the body, and the kidney specialist will check for these. An example would be IgG4 disease which can be associated with a history of fibrosis around the urinary tract (retroperitoneal fibrosis), pancreatic disease or cancers in an extremely rare group of patients.

HOW IS INTERSTITIAL NEPHRITIS DIAGNOSED?

Interstitial nephritis is usually suspected because blood tests show an abnormality in the kidney function. Urine and X-ray tests are first performed to make sure there is no infection or blockage to the flow of urine. If this does not explain the kidney disease, a Kidney biopsy is then performed. A biopsy is the removal of a fragment of kidney with a needle. When the kidney tissue is examined under a microscope, interstitial nephritis may be diagnosed.

WHAT ARE THE SYMPTOMS OF INTERSTITIAL NEPHRITIS?

There are often no symptoms directly connected with the kidneys. It is rare to have pain. Urine is usually passed in normal quantities even when the kidneys are removing little waste product from the body. It is common to pass more urine at night. In some cases, the urine volumes are excessive so you feel dry and thirsty all the time.

Interstitial nephritis can damage the kidneys so much that kidney failure develops. This is a severe build-up of waste products in the body. If severe kidney failure develops, tiredness, sickness, vomiting and itching may occur.

In some people with interstitial nephritis the bowel is affected by inflammation as well as the kidneys. If this is the case, there may be tummy pain or vomiting. In severe cases there may be vomiting of blood. Rarely there is also a blotchy red rash on the skin.

WHAT ARE THE TREATMENTS FOR INTERSTITIAL NEPHRITIS?

It often gets better on its own, especially if the interstitial nephritis was due to a drug that has been stopped. However, in many cases recovery is not immediate and the kidney specialist will consider giving you a course of tablets called steroids (prednisolone). The value of steroids in interstitial nephritis has not been proven conclusively by research, so that most doctors are cautious about starting this treatment. Steroids may help some, but not all, cases of interstitial nephritis. The problem with steroids is the risk of side effects (reduced resistance to infection, weight gain and so on), so that the value of steroids needs to be evaluated in individual cases.

In the rare group of patients, if there is fibrosis (scarring) around the urinary tract then they may benefit from stent to maintain uninterrupted flow of urine.

WILL THE KIDNEYS GET BETTER?

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.

IS INTERSTITIAL NEPHRITIS INFECTIOUS?

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.

IS INTERSTITIAL NEPHRITIS INHERITED?

It is extremely rare for interstitial nephritis to run in families.

DO REPEATED ATTACKS OF INTERSTITIAL NEPHRITIS OCCUR?

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.

IS NORMAL LIFE POSSIBLE?

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.

Last reviewed September 2022
Next review September 2025

Reviewed by Dr Oshini Shivakumar 'Specialist Renal Registrar'

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The National Kidney Federation cannot accept responsibility for information provided. The above is for guidance only. Patients are advised to seek further information from their own doctor.