Nomogram predicting testicular torsion in Japanese patients with acute scrotal pain using physical examination findings and environmental conditions: Development and prospective external validation

Objectives To develop a prediction tool based on physical findings and environmental conditions without utilizing color Doppler ultrasonography to guide non-urologists and patients' families in determining the testicular torsion possibility among patients with acute scrotal pain. Methods Overall, 110 consecutive patients aged <= 30 years with acute scrotal pain at Saitama Medical Center between 2012 and 2014 were retrospectively evaluated. Physical examination results, including scrotal inspection, palpation and gait observation, and environmental conditions at pain onset (time range and ambient temperature) were collected. Multivariate analysis identified significant and independent risk factors for testicular torsion, and a nomogram predicting testicular torsion was constructed. The model underwent prospective validation in an independent set of 123 consecutive patients admitted with acute scrotal pain to our institution between 2015 and 2017. Results Testicular torsion diagnosis rates were 27% (30/110) and 26% (32/123) in the training and validation cohorts, respectively. Logistic regression analysis showed four risk factors for developing testicular torsion: abnormal testicular position, walking difficulty, midnight to early morning onset and ambient temperature <15 degrees C at pain onset. The constructed nomogram showed that the areas under the receiver operating characteristic curves were 0.92 and 0.84 for the training and validation cohorts, respectively. The calibration plot showed an acceptable fitness between the predicted probability and the observed rate of testicular torsion. Conclusions A novel nomogram was developed solely based on physical findings and environmental conditions to predict testicular torsion in Japanese patients with acute scrotal pain.