Specific G protein activation and mu-opioid receptor internalization caused by morphine, DAMGO and endomorphin I

PURPOSE: This study investigates the usefulness of Gadolinium (Gd)-infusion magnetic resonance angiogram (MRA) in the detection of impalpable undescended testes. METHODS: Magnetic resonance (MRI) examination was performed in 14 patients with 17 impalpable undescended testes (unilateral, n = 11; bilateral, n = 3). MRAwasthen performed as follows: Gadolinium-DTPA-BMA (Omniscan) at 0.3 mmol/kg body weight was injected intravenously, and dynamic coronal examination using fast spoiled gradient recalled sequences was obtained with images taken at early arterial and delay venous phases. The testis was located by detection of the enhanced pampiniform venous plexus. RESULTS: Of the 17 undescended testes, 11 canalicular hypoplastic testes and 3 intraabdominal testes were detected in both routine MRI and MRA. Three atrophic testes were found in the scrotum by MRA but not detected by routine MRI. The detection rates of impalpable testes by MRI and MRA were 82.4% and 100%, respectively. All imaging findings were confirmed by surgical exploration. There was no morbidity associated with MRA. CONCLUSION: Gd-infusion MRA is an accurate and sensitive method of preoperative localization of impalpable testes and is superior to conventional MRI in the detection of atrophic testes.