Interstitial nephritis

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at December 1, 2016
StartDiseasesInterstitial nephritis

Interstitial nephritis is a medical condition that describes swelling or inflammation in the spaces between the kidney tubules. It can cause the kidneys permanent damage, but in most cases the patient can make a full recovery. It is usually caused by certain medications.

Contents

Definition & Facts

In addition to regulating the body's balance of electrolytes and producing certain hormones, the kidneys filter blood, remove waste, and form urine. Interstitial nephritis is a condition in which swelling occurs in the kidney interstitium, interfering with these functions. In rare cases, this condition can cause severe complications including acute kidney failure.

Interstitial nephritis can be acute or chronic. Most cases of acute interstitial nephritis are caused by either an allergic reaction to a medication or overuse of medications. Some studies show that the number of cases of acute interstitial nephritis is increasing, perhaps due to the increase in people using multiple medications. Acute interstitial nephritis that is caused by drugs is more common among people over the age of 65.

Symptoms & Complaints

The most common symptoms of interstitial nephritis are urinary problems. In most cases, the patient will urinate substantially less than normal (oliguria). There may also be blood in the urine (hematuria).

Other warning signs include fever, a general feeling of exhaustion, nausea, vomiting, and water retention which might lead to weight gain. The patient also might develop a rash or have high blood pressure (hypertension).

Some patients will develop edema, which is when fluid collects in areas of the body. Those with edema will often have a swollen face or ankle swelling. Additional warning signs are a feeling of being confused and disoriented. Those symptoms are indicators of potentially severe kidney problems. A doctor should be contacted immediately. 

Causes

Most acute cases of interstitial nephritis are caused by an allergic reaction to drugs. It is believed that over 100 prescription drugs can lead to interstitial nephritis. The most common culprits are antibiotics such as penicillin, methicillin, sulfonamide; diuretics like furosemide and thiazide; and proton pump inhibitors like lansoprazole and omeprazole.

It is also linked to long-term use of over-the-counter pain relievers like acetaminophen, aspirin, and nonsteroidal inflammatory drug (NSAID's) of which ibuprofen is a common drug. When these pain relievers cause interstitial nephritis, it is considered analgesic nephropathy.

Interstitial nephritis can also be caused by conditions that are unrelated to adverse drug reactions. These include autoimmune disorders such as Kawasaki disease, systemic lupus erythematosus, and Sjögren's syndrome.

Other prominent causes include a blood potassium deficiency (hypokalemia) and high calcium levels in the system. Infections can also cause interstitial nephritis. Bacterial infections, viral infections, parasitic infections, and fungal infections can affect the kidneys and trigger interstitial nephritis. 

Diagnosis & Tests

The doctor will begin with the understanding that there is a problem with the kidneys. The doctor will ask about a family history of medical problems as well as which medications the patient is taking. They will want to know how long the patient has been taking medications and how often. It is very important to inform the doctor about any type of drug use, including dietary supplements.

The doctor will listen to the patient's lungs to detect fluid build-up (pulmonary edema), which is a sign of kidney failure. High blood pressure and changes in body weight are also warning signs. The physician will run a complete blood count and examine the arterial blood gas levels to see how much oxygen is in the blood. Blood tests will reveal elevated levels of creatinine.

The physician will also run clinical urine tests which will reveal white blood cells. Imaging studies like renal ultrasounds may be done to examine the structure and size of the kidneys. The kidney biopsy is the most definitive diagnostic tool.

Treatment & Therapy

Sometimes treatment is as simple as identifying the drug that is causing the problem and refraining from using it. Patients who stop taking the drug that causes the condition often quickly regain full kidney function. If that doesn't work, the physician might prescribe an anti-inflammatory medication. Doctors can sometimes treat interstitial nephritis with corticosteroids or cyclophosphamide.

Swift treatment tends to lead to a more complete recovery. If it is caught in the latter stages, the risk of permanent damage increases. The patient will be advised to refrain from ingesting too much salt and to follow a diet low in protein.

In extreme cases, the patient will need dialysis or a kidney transplant. In the vast majority of cases, people who develop interstitial nephritis make a full recovery and resume their lives as normal.

Prevention & Prophylaxis

Proper care and caution ought to be exercised among those who take medications. People who regularly use pain relievers, have an autoimmune disease, and have sarcoidosis are at a higher risk for having interstitial nephritis than other populations.

To the extent that certain infections can cause this condition, vaccinations and prompt diagnosis and treatment can help mitigate the risk of developing interstitial nephritis.