Hypersensitivity Nephropathy Workup

Updated: Dec 01, 2015
  • Author: Micah L Thorp, DO, MPH; Chief Editor: Vecihi Batuman, MD, FASN  more...
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Workup

Laboratory Studies

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  • Urine is often examined for eosinophils, but this method lacks adequate sensitivity and specificity. One study found a positive predictive value of 38%. Regular urine microscopy must be supplanted with specific stains for eosinophils (Hansel stain).
  • Eosinophilia may be present, but this is also an unreliable diagnostic finding.
  • Urinalysis often reveals sterile pyuria with microscopic hematuria. Proteinuria is often present, but the quantity varies greatly, ranging from nephrotic levels in patients with NSAID-associated acute interstitial nephritis (AIN) to less than 1 g/d in others.
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Imaging Studies

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  • Renal ultrasound is of minimal value. Normal-sized kidneys with a slight increase in echogenicity are typically noted.
  • Gallium scans often show diffuse bilateral uptake. This can be helpful in differentiating acute interstitial nephritis and acute tubular necrosis, which has a uniformly negative scan result.
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Procedures

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  • The criterion standard diagnostic test for acute interstitial nephritis is renal biopsy. Unfortunately, little else is available to help make a definitive diagnosis. Biopsy frequently reveals either a diffuse or segmental mixed infiltrate.
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