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Acute interstitial nephritis, abbreviated as AIN, is a condition in which there is inflammation and damage to the tissue surrounding the filtering units of the kidneys. AIN is the result of many different causes.

The tissues in the kidney involved include the tubules that carry and process urine as well as the cells that make erythropoietin, a hormone that stimulates the formation of red blood cells. The injury can result in a sudden and severe decline in the kidney function.

What is going on in the body?

In AIN, different types of white blood cells invade the tissue surrounding the filtering system of the kidney. This causes it to swell and become inflamed.

The rise in white blood cells is most often a result of an immune reaction to a medicine, an inherited abnormality, a toxic substance, infections, some blood cancers, electrolyte problems, and other rare diseases.

Most people who have AIN recover completely. Sometimes, however, scarring results. If that happens, the kidney may have irreversible damage and progress to complete failure over time.

What are the signs and symptoms of the disease?

Symptoms of AIN may include:

• flank pain
• blood in the urine
• fever
• joint pain
• decrease in urine flow
• rash on the trunk, upper arms, and legs
• evidence of infection
• anemia causing fatigue and loss of energy
• Symptoms of kidney failure (see chronic renal disease and ESRD)

What are the causes and risks of the disease?

AIN may be caused by:

• medications such as methicillin and other antibiotics, NSAIDS,, phenytoin (used for seizures), lithium (used for manic depressive disorders), as well as medicines used to treat AIDS/HIV infection, prevent transplant rejection, and treat cancer (called chemotherapy).
• heavy metals such as lead or cadmium
• immune disorders, such as systemic lupus erythematosus (SLE), sarcoidosis, and Sjögren syndrome
• infection, such as chronic pyelonephritis or reflux of urine up the collecting system, and mononucleosis.
• blood disorders like multiple myeloma and sickle cell disease
• electrolyte disturbances like low potassium or a high calcium in the blood
• inherited diseases like cystinosis
• radiation to the kidney to treat cancer.

Sometimes the cause is unknown.

What can be done to prevent the disease?

Prevention of AIN is not always possible. Contact with an offending medicine or substance has to be avoided. Other prevention depends on the underlying cause of infection, such fixing "reflux" with surgery.

How is the disease diagnosed?

The healthcare professional can usually diagnose AIN by doing the following:

• taking a history
• doing a complete physical exam
• noting the symptoms related to kidney injury

Urine and blood tests are done to assess the kidney function. A blood count sometimes contains elevated eosinophils, a particular type of blood cell. Diseases such as SLE or sarcoidosis have other blood tests that help diagnose them and identify them as the cause for AIN.

Sometimes a skin biopsy of the rash and/or a kidney biopsy are needed.

What are the long-term effects of the disease?

Most cases of kidney damage can be reversed with removal of the offending agent and treatment which may include dialysis. But a few cases of AIN may lead to lasting kidney failure.

What are the risks to others?

AIN is not contagious and cannot be spread to others. The inherited causes can be passed to children from parents. AIN due to mononucleosis may be spread.

What are the treatments for the disease?

Treatment will depend on what has caused the disease. If the AIN was caused by an allergic reaction to a medicine, the kidney function usually returns to normal once the medicine is stopped. If the kidney function does not return or if the damage is severe, steroids may be used. They can help decrease the inflammation.

Sometimes short-term dialysis may be needed. This can help remove toxins until the kidney function returns. If the damage to the kidneys can't be reversed, the person may need permanent dialysis. Or, in some cases, a kidney transplant may be needed.

What are the side effects of the treatments?

• feeling shaky
• weight gain
• insomnia
• infection
• softening of the bones calles osteoporosis

• bleeding
• infection
• reactions to anesthesia

What happens after treatment for the disease?

Usually the kidney heals completely and the AIN symptoms disappear. If surgery is needed, recovery will depend on the extent of surgery. Some diseases cannot be treated and symptoms related to that disease (sarcoid lung disease) may cause disability.

How is the disease monitored?

The healthcare professional will generally advise regular visits and kidney function tests. Any new or worsening symptoms should be reported to the healthcare professional.