The pattern of radionuclide scrotal scan in torsion of testicular appendages

The aim of this study was to define the radionuclide scrotal imaging (RSI) pattern in cases of torsion of testicular appendages and to correlate it with the duration of symptoms. Two hundred and seventeen patients with acute scrotal pain were evaluated prospectively during the past 13 years. Two groups of patients were defined according to the interval between the onset of symptoms and the performance of RSI: group A comprised patients in whom RSI was performed within 5 h after the onset of symptoms, while group B comprised patients in whom RSI was performed between 5 and 24 h after the onset of symptoms. An SPX-4 Elscint or an Apex 405 gamma camera with a parallel hole or converging collimator was used. Between 5 and 15 mCi of technetium-99m pertechnetate was injected as a bolus intravenously. The radionuclide angiogram consisted of six to eight consecutive 5-s frames. The scrotal static scan was obtained immediately following the radionuclide angiogram. The hot dot sign, which is a small spot of increased tracer perfusion and uptake on RSI, was not present during the first hours after the onset of symptoms. Therefore, RSI is inaccurate and is not indicated for the diagnosis of torsion of testicular appendages of less than 4–5 h duration. The hot dot sign was, however, demonstrated on the RSI in 45% of the patients with scrotal pain lasting between 5 and 24 h. The overall sensitivity and accuracy of RSI in diagnosing torsion of testicular appendages in this group of patients were 68% and 79%, respectively. In all the patients with a positive hot dot sign, torsion of testicular appendages was found at exploration (specificity 100%). Therefore, the hot dot sign was found to be pathognomonic of torsion of testicular appendages.