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Kidney Week

Abstract: SA-PO143

Erroneous Diagnosis of Acute Interstitial Nephritis on Gallium-67 Scintigraphy

Session Information

Category: Acute Kidney Injury

  • 102 AKI: Clinical, Outcomes, and Trials

Authors

  • Mahmood, Arslan, Lenox Hill Hospital, New York, New York, United States
  • Rosenstock, Jordan L., Lenox Hill Hospital, New York, New York, United States
Introduction

Acute interstitial nephritis (AIN) and acute tubular necrosis (ATN) are common etiologies for acute kidney injury (AKI) in a patient with infection being treated with antibiotics. Kidney biopsy is the gold standard to distinguish between these diagnoses, but gallium-67 scintigraphy is sometimes used if a biopsy is considered high risk. We report a case where the gallium scan gave an erroneous result.

Case Description

We present a case of a 32-year-old male admitted for right elbow swelling, associated with fever to 100.4 for one day. Physical exam was significant for chronic venous malformations on the right arm, one of which was now tender to touch and palpation. Thrombophlebitis was suspected. Creatinine was 1.62 mg/dl which improved to 1.19 after 2 Liters of normal saline. Piperacillin/Tazobactam and Vancomycin were started. Blood cultures grew Pasteurella Multocida. Antibiotics were tailored towards this infectious agent. However, the patient remained febrile for three days after the bacteremia had cleared. Meanwhile, his creatinine rose from 1.19 to 2.81 in 72 hours. Urinalysis showed 100mg/dl protein, sterile pyuria and few granular casts. Renal ultrasound showed normal size and echogenicity. A gallium scan was done to identify the source of ongoing fever and revealed intense activity in the kidneys suggestive of interstitial nephritis. Kidney biopsy was done to confirm the diagnosis. Empiric Prednisone 1mg/kg/day was started while waiting for biopsy results. The biopsy showed ATN. Prednisone was then discontinued. Creatinine improved to 1.0 one week after discharge.

Discussion

Kidney biopsy is the gold standard for diagnosing acute interstitial nephritis but is not always attainable. Gallium-67 scintigraphy has emerged as an alternative modality to diagnose AIN. Graham et al showed 100% specificity but poor sensitivity when using an uptake cutoff of grade 5, which means the intensity of radioisotope uptake in the kidney is higher than in the liver. Few older studies have shown varying degrees of sensitivity and specificity. Our patient had a grade 5 uptake, yet the biopsy did not show AIN. Thus, our case highlights the limitations of the gallium scan in diagnosing AIN and confirms that when the clinical picture is unclear, biopsy may be preferred.