BACKGROUND: Urinary retention after anorectal surgery is thought to be a mild complication but has a high incidence. Since anal pain and distention can contribute to the urethral spasm reflex which may cause urinary retention, we investigated the effect of absorbable gelatin sponge (Gelfoam(R)) used for anal packing postoperatively on urinary retention after hemorrhoidectomy under spinal anesthesia. METHODS: One hundred and nineteen ASA Physical Status I patients scheduled for hemorrhoidectomy were selected. Patients were randomly divided into Group A, postoperative anal packing free group and Group B, postoperative anal packing group and studied prospectively. Spinal anesthesia was performed with the bevel of 25 gauge Quincke needle parallel to dura fibers at lumber 3 4 intervertebral space and the injection of hyperbaric 0.5% tetracaine 6 mg (1.2 ml) to patients in sitting position. After hemorrhoidectomy, all patients were permitted to ambulate as soon as possible and urinate spontaneously. If urinary retention occurred, urinary catheterization was done temporarily. The number of patients who received urinary catheterization were recorded. Surgical technique and the total amount of intravenous fluid during the operation were controlled. RESULTS: The incidence of urinary retention in Group A (11/57, 19.3%) was similar to that in Group B (10/62, 16.1%) (P = 0.651, chi 2 = 0.205, degree of freedom = 1). CONCLUSIONS: Our study did not indicate the clue that the absence of anal packing helped to reduce the incidence of urinary retention after hemorrhoidectomy under spinal anesthesia.