Comparison Between Posterior Retroperitoneoscopic Adrenalectomy and Laparoscopic Adrenalectomy

Inclusion Criteria: * Patients who are expected to have benign adrenal disease at preoperative exams * Patients who have pheochromocytoma measured less than 5cm, and the other benign adrenal tumors less than 7cm in diameter in preoperative CT scan * Patients who do not have previous surgery history at the interested quadrant * Patients who is I or II grade in ASA classification(American society of anesthesiologists' physical status classification) * Patients who has tolerable liver function and renal function(bilirubin\<2.0mg/dl and AST, ALT, serum creatinine within twice of upper normal range, coagulation panel : within normal limit) * Patients whose BMI(body mass index) is less than 35 * Patients who are supposed to have normal cognitive function * Patients who signed the consent paper. Exclusion Criteria: * Patients who are expected to have malignant or metastatic adrenal tumor at preoperative exams * Patients who have bilateral adrenal tumors * Patients who have condition to undergo the other operation at the abdomen together with adrenalectomy * Pregnant patients * Patients who have active or uncontrolled infection * Patients who have medical problems as below * Uncontrollable hypertension with medication(Systolic BP\>150 or diastolic BP\>100) * Angina, congestive heart failure, acute myocardial infection * History of coronary angioplasty or Coronary artery bypass graft surgery * History of stroke, transient ischemic attack with sequela