What are the other Names for this Condition? (Also known as/Synonyms)

• Acute Interstitial Nephritis
• Chronic Interstitial Nephritis
• Tubulointerstitial Nephritis

What is Interstitial Nephritis? (Definition/Background Information)

• Interstitial Nephritis is a kidney disorder in which the kidney’s ability to filter waste and extra fluids is impaired. The condition may be temporary, acute, or if it persists for a long period of time, it can become chronic
• The most common cause of Interstitial Nephritis is an excessive use of over-the-counter medications, generally painkillers. An allergic reaction to certain drugs can contribute to its development
• The main symptom of Interstitial Nephritis is a decrease in urine output. Interstitial Nephritis causes inflammation of the interstitium of the kidney (spaces between the kidney tubules)
• Increased levels of waste products from the body (blood urea nitrogen and creatinine) and extra collection of fluid in the body (edema) can cause complications by accumulating in the body and adversely affect other areas of the body
• When diagnosing Interstitial Nephritis a urinalysis, blood testing, and a renal biopsy are generally performed to check kidney health and functioning
• Avoiding excessive OTC medication usage, bringing about certain dietary changes, and/or the administration of corticosteroids, are commonly used in the treatment of Interstitial Nephritis
• Often Interstitial Nephritis is only acute and near normal kidney function can be regained after a few months through appropriate therapy. The prognosis in chronic cases (Chronic Interstitial Nephritis) depends upon the extent of kidney damage

Who gets Interstitial Nephritis? (Age and Sex Distribution)

• Most commonly, Interstitial Nephritis occurs in individuals (adults) who use medications, such as acetaminophen and aspirin, in excessive amounts (ingesting more than the recommended dosage)
• Older adults are more likely to get Interstitial Nephritis, because they often take more medications and may even take combinations of medications
• There is no gender preference for those who are affected by Interstitial Nephritis; both males and females are prone to the condition
• All racial and ethnic groups are at risk for this condition and no specific predilection is observed

What are the Risk Factors for Interstitial Nephritis? (Predisposing Factors)

Risk factors for Interstitial Nephritis can include:

• Allergic drug reactions to about 100 different medications are known to have caused Interstitial Nephritis
• Often Interstitial Nephritis occurs in individuals who overuse certain medications, especially painkillers
• Bacterial infections affecting the kidneys
• Autoimmune diseases and disorders including anti-tubular basement membrane disease, Wegener’s granulomatosis, Sjögren’s syndrome, systemic lupus erythematosus, and Kawasaki’s disease
• Individuals with sarcoidosis, an inflammatory lung disease, are also at risk
• Individuals, who do not recover adequately from Acute Interstitial Nephritis, can progress to Chronic Interstitial Nephritis

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases ones chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Interstitial Nephritis? (Etiology)

The following are possible causes of Interstitial Nephritis:

• Any allergic reaction to a drug can result in Acute Interstitial Nephritis. It can be a side effect for various antibiotics and medications including:
  • Penicillin
  • Methicillin
  • Ampicillin
  • Sulfonamide medications
  • Furosemide
  • Thiazide diuretics
  • Triamterene
  • Allopurinol
  • Omeprazole
• Any bacterial, viral, or other types of infections, affecting the kidneys can result in this condition
• Multiple autoimmune disorders can cause Interstitial Nephritis and they include:
  • Anti-tubular basement membrane disease: Autoantibodies attack the kidney cells due to the presence of an abnormal immune system
  • Wegener’s granulomatosis: It is a disorder involving inflamed blood vessels
  • Sjögren’s syndrome: An autoimmune disease that causes dryness in the eye
  • Systemic lupus erythematosus: An autoimmune disease in which healthy tissue is attacked by the body
  • Kawasaki’s disease: A disease causing inflammation of the arteries  
• Use of the following medications for a long period of time:
  • Acetaminophen or paracetamol (Tylenol)
  • NSAIDs (non-steroidal anti-inflammatory drugs)
  • Aspirin
• Low levels of potassium in blood
• High levels of calcium or uric acid in blood

What are the Signs and Symptoms of Interstitial Nephritis?

The signs and symptoms of Interstitial Nephritis may include:

• Fever and exhaustion
• Traces of blood in urine; dark urine
• An increase or decrease in urine output (more often, a decrease)
• Drowsiness and confusion
• Nausea and vomiting
• Rash development on the skin
• Excessive fluid accumulation in the body (edema); this can result in swelling around the face and/or the ankles
• Weight gain as a result of fluid accumulation
• Abdominal bloating
• High blood pressure

How is Interstitial Nephritis Diagnosed?

The following tests and exams may be taken to diagnose Interstitial Nephritis:

• A physical examination with a healthcare provider is crucial for a diagnosis 
• The blood pressure is examined and blood tests are taken. The kidney function is assessed with the following tests:
  • Complete blood count (CBC)
  • Blood urea nitrogen (BUN)
  • Blood creatinine level testing 
• Blood gas levels can be checked to see if the levels of oxygen and carbon dioxide are abnormal
• A urinalysis may be performed
• A renal ultrasound may reveal abnormalities in the kidney size
• Renal biopsy is often very helpful; examination of the biopsy specimen by a pathologist is crucial to the diagnosis
• Examination of the lung for the presence of fluid, checking for regularity of heartbeat, checking the blood pressure, and examination of the whole body for fluid accumulation, helps in arriving at a diagnosis

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Interstitial Nephritis?

Complications of Interstitial Nephritis can include:

• Interstitial Nephritis can cause metabolic acidosis, because the kidneys are unable to filter out acids properly
• If the condition persists, chronic kidney failure or end-stage kidney disease can occur, in severe cases
• Allergic drug reactions can be worse in older adults; they are more likely to have permanent kidney damage

How is Interstitial Nephritis Treated?

Interstitial Nephritis can be treated with the following measures:

• Often, Acute Interstitial Nephritis is caused by certain medication(s) that the individual is taking. Thus, refraining from taking such medications can bring about a symptom-relief. Often an individual who has discontinued such medications, will have near normal kidney function within a few weeks
• Diet changes can help, such as limiting salts, fluids, and proteins, to improve the swelling, blood pressure, and buildup of wastes
• Dialysis may be needed for a brief period of time to filter blood, if kidney function is severely affected
• Corticosteroids may be prescribed in some cases
• Anti-inflammatory medications, such as cyclophosphamide, can be sometimes effective

How can Interstitial Nephritis be Prevented?

• It is generally very difficult to prevent Interstitial Nephritis
• However, limiting the use of medications that potentially cause Interstitial Nephritis, such as acetaminophen, aspirin, and NSAIDS, can help lower risks

What is the Prognosis of Interstitial Nephritis? (Outcomes/Resolutions)

• Interstitial Nephritis is often only a short-term condition
• Two phases of recovery are seen in those healing from Interstitial Nephritis. An initial phase that lasts from 6-8 weeks, and a slower phase of recovery that lasts for about a year, until near normal renal function occurs
• However, if Interstitial Nephritis becomes long-lasting, then it can lead to chronic kidney failure. The prognosis in such cases is poor
• Elderly individuals are more likely to have Chronic Interstitial Nephritis, which can cause permanent kidney damage

Additional and Relevant Useful Information for Interstitial Nephritis:

70-90% of Interstitial Nephritis cases are due to allergic reactions to medications, or due to an overuse of medications. Interstitial Nephritis, occurring due to autoimmune disorders or bacterial infections, is a much rarer occurrence.