Near infrared spectroscopy to diagnose experimental testicular torsion: comparison with Doppler ultrasound and immunohistochemical correlation of tissue oxygenation and viability.

PURPOSE: Near infrared spectroscopy measures tissue oxygenation even when there is complete cessation of blood flow. We evaluated near infrared spectroscopy to diagnose testicular torsion and blindly compared its accuracy with that of Doppler ultrasound. We also compared it by immunohistochemical evaluation of hypoxia and cell viability.
MATERIAL AND METHODS: Rats were randomized to 4 groups, including group 1-720-degree unilateral torsion, group 2-360-degree unilateral torsion, group 4-sham operation and group 4-720-degree unilateral torsion followed by surgical torsion reduction at minute 180. Near infrared spectroscopy and Doppler ultrasound were done blindly at minutes 0, 5, 30, 60, 180 and 400. All torsed and contralateral testicles were excised for pathological examination using hypoxia inducible factor-α for hypoxia and the TUNEL test for apoptosis. We compared all groups with the contralateral testis and the sham operated group.
RESULTS: All blinded, near infrared spectroscopy measurements correctly identified the torsed testis after minute 5. Median oxygen saturation in groups 1 and 2 was significantly different compared to that in the sham operated group after minute 5. In group 4 near infrared spectroscopy detected detorsion with the loss of a significant oxygen saturation difference between the affected and the contralateral testicle after detorsion. At minute 400 median oxygen saturation in group 4 was not statistically different compared to that in the sham operated group (p = 0.09) but it was significantly different compared to that in groups 1 and 2 (p <0.001). In each torsed testis oxygen saturation was at least 18.75% lower than in the contralateral testis. In groups 1 and 2 hypoxia inducible factor-α staining in torsed testicles was significantly greater than that in the contralateral organ and the sham operated group. In group 4 hypoxia inducible factor-α staining after detorsion was significantly decreased compared to that in groups 1 and 2. There was no significant difference in the apoptotic index between the experimental and the contralateral testis or the sham operated group.
CONCLUSIONS: Near infrared spectroscopy is as effective but quicker than Doppler ultrasound for detecting testicular torsion without a radiologist. Near infrared spectroscopy accurately reveals oxygen saturation, which is more vital than blood flow, on which Doppler ultrasound focuses.