Effect of spironolactone on MTO lateralization
DISEASE
AVS and MTO were performed with patients taking medications that did not interfere with the renin–angiotensin system. We also wanted to establish whether leaving patients on spironolactone at the time of their MTO would prevent the detection of unilateral disease. Six patients underwent MTO scanning on two separate occasions: once having discontinued spironolactone (as part of the standard protocol) and on a separate occasion while taking at least 50 mg spironolactone. The dose of spironolactone was not intended to achieve complete aldosterone blockade, but to reflect typical doses used in clinical practice. In five out of six patients, spironolactone did not change the scoring of MTO. In the sixth case, the MTO scan without spironolactone (the core protocol scan and the one used for analysis) was graded as a low probability of unilateral disease, whereas the scan performed while taking spironolactone indicated a high probability. AVS was concordant with the MTO results on spironolactone, as it too indicated unilateral PA. Post-adrenalectomy, this patient achieved complete biochemical and partial clinical success. Overall, there was no evidence that MTO performed while on spironolactone reduced the probability of detecting unilateral PA.