Acute Interstitial Nephritis (AIN): Causes, Risk Factors, Symptoms, Treatment, Prognosis

This article discusses about a pathological condition of the kidneys caused by inflammation of interstitial tissue. Interstitial tissue is the connective tissue between cells of most of the organs. The interstitial inflammation causing swelling in kidney results in several complications.  This swelling and inflammation of renal (kidney) interstitial tissue often involves the renal tubules. The disease is known as Interstitial Nephritis.  In this article, we will discuss about the various causes, symptoms, and treatments given for Interstitial Nephritis. 

• Interstitial Nephritis is caused by inflammation and swelling of interstitial connective tissue between renal tubules.¹  
• The main function of the glomerulus of the kidney renal tubule is to filter the blood to remove water, electrolytes and metabolic waste products. 
• The function of the convoluted tubules in the kidney is to reabsorb water, carbohydrate, protein and electrolytes, which are filtered by glomerulus.   
• Important filtered organic (protein and carbohydrate) and inorganic (sodium, potassium, chloride and phosphate) substances are reabsorbed by the renal tubule and excess water and metabolic waste are excreted. 
• Interstitial nephritis can be acute or chronic. 
• Acute Interstitial Nephritis is the more common form of Interstitial Nephritis in the United States.
• Swelling of interstitial tissue and renal tubules in the kidney can result in a number of symptoms, which can be moderate to severe.
  

These adverse drug reactions are more acute in the elderly population and have the potential to cause permanent kidney damage.

• Acute Interstitial Nephritis is usually caused as a result of an allergic reaction to medications. 
• There are many medications, which can cause Acute Interstitial Nephritis, some of them are:
  • Antibiotics- Sulfonamide and methicillin²
  • NSAIDs³
  • Proton pump inhibitors.
    

• Bacterial Pyelonephritis.
• Renal Tuberculosis.
• Fungal Nephritis.

• Depleted cell mediated immunity.
• Caused by anti-tubular basement membrane antibodies.
• Interstitial nephritis is often associated with Immune complex mediated diseases like Systemic Lupus Erythematosus and Sjogren’s Syndrome.

• Low potassium.
• Low calcium.

• Elderly Population- Retirees and older individuals are at a greater risk for developing Acute Interstitial Nephritis. 
• Antibiotic Treatment- Individual taking multiple medications and antibiotics are at risk to develop Interstitial Nephritis.
• Chronic use of over-the-counter pain medications.
• People who have autoimmune disorders.
• People suffering from sarcoidosis.

The most general symptom of Acute Interstitial Nephritis is decreased urinary output. Some of the other symptoms of Acute Interstitial Nephritis are:

• Fever.
• Fatigue and malaise.
• Anorexia.
• Nausea and vomiting.

• Hypersensitivity Symptoms
  • Fever.
  • Skin Rash.
  • Joint Pain.
• Kidney Symptoms
  • Flank Pain.
  • Hematuria.
  • Weight Gain.
  • Swelling and edema.
  • Hypertension.
• Confusion

• If a physician is suspicious of a renal dysfunction, then the physician will conduct a detailed physical examination where the affected individual will be asked about family history, medications taken and the frequency of it, since when are the medications being taken etc.
• Evaluate Fluid Retention- 
  • Peripheral Edema.
  • Pleural Effusion.
• Evaluate Autoimmune Symptoms-
  • Joint Pain.
  • Joint Swelling.
  • Fever.
  • Skin Rash.

• Blood Examination
  • CBS.
  • Erythrocyte sedimentation rate.
  • Electrolytes.
  • BUN and creatinine.
  • Blood gases.
• Urine Examination
  • Urine analysis.
• Evaluate Autoimmune
• Kidney Radiological Studies
• Renal Biopsy

• Discontinue antibiotics causing the interstitial nephritis.
• Discontinue over the counter medication.
• Discontinue pain medications and NSAIDs.

• Restrict Salt- Restricting salt from diet also helps with water retention and hypertension.  
• Water.
• Protein Diet- A low-protein diet is also very helpful in order to improve renal function.
• Salt.

• Interstitial nephritis caused by autoimmune disease responds to corticosteroids. Large dose is tried during initial phase and small dose is used as maintenance dose.

• Hyperkalemia not responding to diet control and medications.
• Mental Status Change- Mental status may change because of electrolyte or fluid imbalance. One of the treatments is to correct causative factors. Rapid correction is necessary to prevent permanent brain damage.

• Treatment of End Stage Renal Disease.

• Generally Acute Interstitial Nephritis is of a short duration. Only in rare instances doe it cause a permanent damage to the kidneys.
• Acute Interstitial Nephritis is found to be more severe in elderly and causes more damage in the elderly population.
• Appropriate timely correction of electrolyte and fluid imbalance prevents permanent kidney damage.

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