What is interstitial nephritis?
Interstitial nephritis is an inflammation of the connective tissue of the kidney.
There is little or no involvement of the filtering units of the kidneys (glomeruli).
Acute interstitial nephritis is most often caused by the reaction to a drug.
Drugs commonly associated with this condition include antibiotics, diuretics, and nonsteroidal anti-inflammatory drugs (NSAIDs).
Less common causes of acute interstitial nephritis include systemic infections (strep, diphtheria, leprosy, syphilis), primary kidney infections, and immune disorders (systemic lupus erythematosus, necrotizing vasculitis).
Ongoing (chronic) interstitial nephritis is most often associated with chronic urinary tract obstruction, abuse of pain relievers (analgesics), lithium (a drug used to treat psychiatric illnesses), abnormal concentrations of substances normally present in the kidney (uric acid, calcium oxalate, calcium, potassium), chronic bacterial kidney infections (pyelonephritis), persistent or progressive acute interstitial nephritis, immune disorders (systemic lupus erythematosus, necrotizing vasculitis), cancers (leukemia, lymphoma), abnormal proteins (amyloid, multiple myeloma), diabetes, sickle cell anemia, and exposure to environmental agents (lead, cadmium).
How is it diagnosed?
History: In acute interstitial nephritis, the individual may report a sudden decrease in kidney function after taking a new medication or a recent bacterial or viral infection. Symptoms characteristic of an allergic reaction are common, including fever and skin rash. Pain in the side (flank) may occur, and blood may be present in the urine. Individuals with chronic interstitial nephritis may have a history of chronic analgesic abuse, prolonged immunosuppressant (cyclosporine) therapy, or occupational exposure to lead or cadmium.
Physical exam: The physical exam in both acute and chronic interstitial nephritis may be normal. Occasionally, individuals with acute interstitial nephritis may have a rash and flank pain.
Tests: Urinalysis may reveal blood, increased protein (proteinuria), pus (pyuria) and increased white blood cells. Ultrasound and retrograde pyelography (x-ray of urinary tract wherein the radiopaque dye has been injected up into the kidneys from the ureters) may be used to rule out other conditions, such as renal lesions, obstructions, or tumors. If the diagnosis is unclear, a kidney biopsy (small sample of tissue surgically removed for microscopic examination) may be indicated.
How is interstitial nephritis treated?
If the acute interstitial nephritis is due to a specific drug, the drug may be discontinued, changed or the dosage modified. Antibiotics are used if the condition is due to infection. Both acute and chronic interstitial nephritis may be treated with anti-inflammatory drugs (corticosteroids). Dialysis (process of removing toxic materials from the blood by passing it through a filter) may be used to treat reduced kidney function or to restore fluid and electrolyte balance.
What might complicate it?
Complications include renal failure, tissue death in areas of the kidney (papillary necrosis), gouty arthritis, increased risk of atherosclerotic diseases (especially coronary artery disease), narrowing or constricting of the renal artery (stenosis), sodium and fluid retention, metabolic acidosis, and nephrotic syndrome.
Outcome is dependent on the cause or type of the nephritis. Most individuals with acute interstitial nephritis recover completely in a few weeks. Individuals with prolonged and severe acute interstitial nephritis may progress to renal failure. While most individuals with chronic interstitial nephritis will recover some function with treatment, a few of the individuals will progress to chronic renal failure. Recovery from renal failure in individuals with chronic interstitial nephritis is rare. Individuals with interstitial nephritis associated with analgesic abuse will recover some function if the drug is stopped. If it is not stopped, progression to renal failure occurs. Finally, individuals with interstitial nephritis have an increased risk of transitional cell carcinoma (cancer).
Other possibilities include tumors, diabetes, renal tuberculosis, and acute or chronic obstructive uropathy (disease resulting from obstruction of the urinary tract).
Nephrologist and urologist.
Last updated 6 April 2018