Near-infrared spectroscopy assessment of tissue saturation of oxygen in torsed and healthy testes.

OBJECTIVES: The objective was to assess whether testicular torsion is associated with low testicular tissue saturation of oxygen (StO2 ) as measured by transscrotal near-infrared spectroscopy (NIRS) and to compare the differences in NIRS values between testicles of the same patient, both in patients with testicular torsion and in healthy controls. METHODS: This was an observational study of healthy controls and patients with surgically confirmed testicular torsion who were recruited from males under 30 years of age presenting to the emergency department (ED). The hypothesis was that the difference in NIRS values for the control's two testicles would be zero, and that the difference between the torsed and healthy testicles on an individual patient would not be zero. Based on animal data, the study was powered to detect an absolute difference of StO2 of 47%. RESULTS: The mean StO2 for the left control patients' testicles was 73.6% (95% confidence interval [CI] = 68.0% to 79.1%) and the mean StO2 for the right controls' testicles for controls was 73.6% (95% CI = 66.9% to 80.4%; n = 17). The absolute difference in NIRS StO2 for left minus right for each individual was 3.5% (95% CI = 1.8% to 5.4%), which was significantly different (p = 0.0007), and refuted the hypothesis that there was no significant difference in StO2 between left and right testes in healthy patients. In the testicular torsion group, the torsed side had a mean StO2 of 82.8% (95% CI = 68.7% to 96.9%), and the contralateral nontorsed testes had a mean of 85.8% (95% CI = 72.3% to 99.3%). The mean StO2 difference, nontorsed minus torsed was 3.0% (range = -1% to 9%, 95% CI = -2% to 8%; p = 0.174), refuting the hypothesis that torsed testes would demonstrate significantly lower values for StO2 . CONCLUSIONS: While pilot animal investigations support a potential role for transscrotal NIRS for the detection of testicular torsion, this first clinical translation of animal findings reveals that the investigated, transcutaneous, reflectance geometry NIRS device failed to demonstrate symmetric oxygenation of left and right testes in healthy controls and also failed to demonstrate depressed tissue saturation of oxygen values in patients with confirmed testicular torsion. While limited by a small sample size, other problems such as inability to calibrate depth of measurement of StO2 may have led to falsely elevated readings in patients with torsion.