Preoperative Investigation

Preoperative investigations include radiological imaging to study the anatomical details and endocrinological investigation to determine the functional status. Elevated plasma or urinary aldosterone level indexed against urinary sodium excretion, and measured after sodium loading in combination with previously demonstrated low peripheral renin activity during sodium depletion, is the biochemical hallmark of hyperaldosteronism. Pre- and post-contrast computed tomography scan is the most accurate imaging modality. Conversely, small adrenal lesions are often not well visualized with adrenal magnetic resonance imaging (28). Twenty-four hour urine cortisol and plasma cortisol levels and adrenocorticotrophic hormone after dexamethasone suppression test are the cornerstone of biochemical diagnosis of cortisol-hypersecreting Cushing's adenoma. A 24-hour urine analysis for norepinephrine, epinephrine, and vanillylmandelic acid is mandatory whereas serum norepinephrine and epinephrine levels are less sensitive in diagnosing pheochromocytoma (29).

Combination of computed tomography, magnetic resonance imaging, and 131I metaiodo-benzylguanidine scintigraphy allows accurate localization of virtually all pheochromocytomas (30). The authors use surface- and volume-rendered three-dimensional spiral computed tomography datasets for preoperative planning of laparoscopic partial adrenalectomy. Interactive visualization of volume-rendered computed tomography images are helpful for preoperative planning and successful performance of the procedure, whereas color-coded surface-rendered computed tomography datasets are more accurate and convenient for intraoperative reference.

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