Interstitial nephritis is a kidney condition characterized by inflammation of the spaces between the kidney tubules, known as the interstitium. This inflammation can disrupt the kidney's ability to filter waste and maintain fluid balance. Common causes include certain medications, infections, and autoimmune diseases. Symptoms of interstitial nephritis may include fever, rash, and changes in urine output. Diagnosis typically involves blood tests, urine tests, and imaging studies. Treatment focuses on addressing the underlying cause, which may involve stopping offending medications or managing infections, and in some cases, corticosteroids may be prescribed to reduce inflammation.