Before spinal anesthesia is performed, patients are randomized into one of the 3 study groups (no preload, preload with Ringers' Lactate 14 ml/kg, preload with HES 6% 7 ml/kg). Spinal anesthesia is administerd with lidocaine 2% 70mg. Hypotension is treated with vasopressors, atropine or additional intravenous fluid. Bladder scans will be performed on the recovery unit and day-case unit. Total urinary volume is measured until sensory function at dermatome S2/3 is restored and spontanous voiding is possible.