Interstitial nephritis

Definition

Interstitial nephritis is a kidney disorder in which the spaces between the kidney tubules become swollen (inflamed). This can cause problems with the way your kidneys work.

Alternative Names

Tubulointerstitial nephritis; Nephritis - interstitial; Acute interstitial (allergic) nephritis

Causes, incidence, and risk factors

Interstitial nephritis may be temporary (acute), or it may be long-lasting (chronic) and get worse over time.

The acute form of interstitial nephritis is most often caused by side effects of certain drugs.

The following can cause interstitial nephritis:

• Allergic reaction to a drug (acute interstitial allergic nephritis)
• Autoimmune disorders such as anti-tubular basement membrane disease, Kawasaki?s disease, Sjogren syndrome, systemic lupus erythematosus, or Wegener?s granulomatosis
• Infections
• Long-term use of medications such as acetaminophen (Tylenol), aspirin, and nonsteroidal anti-inflammatory drugs (NSAIDS). This is called analgesic nephropathy.
• Side effect of certain antibiotics (including penicillin, ampicillin, methicillin, sulfonamide medications, and others)
• Side effect of other medications such as furosemide, thiazide diuretics, omeprazole, triamterene, and allopurinol
• Too little potassium in your blood
• Too much calcium or uric acid in your blood

Symptoms

Interstitial nephritis can cause mild to severe kidney problems, including acute kidney failure. In about half of cases, people will have decreased urine output and other signs of acute kidney failure.

Symptoms of this condition may include:

• Blood in the urine
• Fever
• Increased or decreased urine output
• Mental status changes (drowsiness, confusion, coma)
• Nausea, vomiting
• Rash
• Swelling of the body, any area
• Weight gain (from retaining fluid)

Signs and tests

The health care provider will perform a physical exam. This may reveal:

• Abnormal lung or heart sounds
• High blood pressure
• Fluid in the lungs (pulmonary edema)

Common tests include:

• Arterial blood gases
• Blood chemistry
• BUN and blood creatinine levels
• Complete blood count
• Kidney biopsy
• Kidney ultrasound
• Urinalysis

Treatment

Treatment depends on the cause of the problem. Avoiding medications that lead to this condition may relieve symptoms quickly.

Limiting salt and fluid in the diet can improve swelling and high blood pressure. Limiting protein in the diet can help control the buildup of waste products in the blood (azotemia) that can lead to symptoms of acute kidney failure.

If dialysis is necessary, it usually is required for only a short time.

Corticosteroids or stronger anti-inflammatory medications such as cyclophosphamide can sometimes be helpful.

Support Groups

Expectations (prognosis)

Most often, interstitial nephritis is a short-term disorder. In rare cases, it can cause permanent damage, including chronic kidney failure.

Acute interstitial nephritis may be more severe and more likely to lead to long-term or permanent kidney damage in elderly people.

Complications

Metabolic acidosis can occur because the kidneys aren't able to remove enough acid. The disorder can lead to acute or chronic kidney failure or end-stage kidney disease.

Calling your health care provider

Call your health care provider if you have symptoms of interstitial nephritis.

If you have interstitial nephritis, call your health care provider if you get new symptoms, especially if you are less alert or have a decrease in urine output.

Prevention

In many cases, the disorder can't be prevented. Avoiding or reducing your use of medications that can cause this condition can help reduce your risk.

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References

Neilson EG. Tubulointerstitial diseases. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 123.

Remuzzi G, Perico N, DeBroe ME. Tubulointerstitial diseases. In: Brenner BM, ed. Brenner and Rector's the Kidney. 8th ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 33.