Can ¹¹¹In-labeled leukocyte imaging differentiate acute interstitial nephritis from acute tubular necrosis?

Objectives This study was conducted to determine if ¹¹¹In-labeled leukocyte imaging (InWBC) could be used to differentiate acute interstitial nephritis (AIN) from acute tubular necrosis (ATN).

Methods None rats were divided into 3 groups of 3 animals each: Controls, AIN, and ATN. AIN animals were imaged 14 days after a single injection of 150 mg/kg puromycin aminonucleoside. ATN animals were imaged 8 days after intraperitoneal injection of 6 mg /kg cisplatin. For all 3 groups, imaging was performed approximately 24 hours after injection of 3.7 MBq human ¹¹¹In-WBC. Static images were acquired at maximum magnification (zoom = 2.19, 5.9 mm/pixel) with high energy parallel hole collimators for 600 seconds. Manual regions of interest were drawn over each kidney and for a section of spine visualized between kidneys, and kidney:spine ratios were generated. A Nuclear Medicine physician viewed all images. After imaging, animals were euthanized and organs removed and sent to pathology. Renal tissue samples were evaluated by a pathologist for evidence of cellular infiltration.

Results Visual appearance of images was similar among the 3 Groups, and ratios of kidney:spine counts/pixel were similar among Controls (2.07±0.21), AIN (1.96±0.30), and ATN (1.69±0.10) Groups (ANOVA F-ratio=2.4, p=0.18). Ratios were similar for AIN and ATN (p=0.25). Cellular infiltration, which was predominantly mononuclear, was significantly higher in AIN than in ATN and controls (2.3±0.5 versus 0.6±0.5 cells, p=0.002).

Conclusions These results suggest that labeled leukocyte imaging is not useful for differentiating acute interstitial nephritis from acute tubular necrosis, probably because the cellular infiltrate in AIN is mononuclear rather than neutrophilic.