In a patient with eosinophils and decreased urine output, what is the likely diagnosis?

• A. Acute kidney injury
• B. Interstitial nephritis
• C. Acute tubular necrosis
• D. Nephrotic syndrome

Answer: (B)

In a patient presenting with eosinophils and decreased urine output, the likely diagnosis is interstitial nephritis. This condition is characterized by inflammation of the renal interstitium and can lead to acute kidney injury. A common cause of interstitial nephritis is an allergic reaction to medications, leading to an accumulation of eosinophils in the kidney tissues. The presence of these eosinophils is a hallmark of this type of nephritis and indicates an immune-mediated response.

Decreased urine output occurs due to impaired kidney function resulting from the inflammatory process affecting the renal interstitium. Unlike in acute tubular necrosis, where urine output can vary, interstitial nephritis typically leads to a more consistent reduction in urine due to the direct involvement of the interstitial area of the kidneys rather than the tubules.

While acute kidney injury is a general term that encompasses various causes, interstitial nephritis specifically refers to this inflammatory condition with eosinophilia. Other conditions like nephrotic syndrome primarily present with proteinuria and edema, diverging from the profile established by eosinophils and reduced urine output. Thus, the presence of eosinophils in the context of decreased urine output strongly points towards interstitial nephritis as the diagnosis.