Abstract： Objective To explore the application of laparoscopy for diagnosing and treating contralateral patent processus vaginalis and elucidate the relationship of contralateral patent processus vaginalis (CPPV) and metachronous inguinal hernia (MIH) through laparoscopy and hemiorrhaphy in children with unilateral inguinal hernia.Methods At two pediatric surgical centers between January 2011 and December 2013,a total of 2,538 patients with unilateral inguinal hernia underwent open repair while 2,855 patients received laparoscopic evaluations of contralateral inguinal region for determining whether or not CPPV co-existed during unilateral inguinal hemia repair.All CPPVs were repaired.The parameters of demographics,initial hernia sideness and number of CPPV/MIH cases were recorded.Meanwhile interval time between initial repair and an onset of MIH and recurrence rates after initial operation were compared.Follow-ups were conducted until December 2014.Results Among 2,538 cases of initial unilateral inguinal hernia,there were 2,122 (83.6％) boys and 416 (16.4％) girls with a mean age of 2.45 + 2.18 years.Initial hernia occurred at right (66％) and left (34 ％) sides.Among 62 MIH cases,there were 51 (2.4 ％) boys and 11 (2.6 ％) girls (P =0.77).The average interval time between initial repair and an onset of MIH was 18.71 + 13.80 months and the rate of recurrence 1.02％ at 9.93 ± 8.58 months after initial operation.Among 2,855 laparoscopic cases,there were 2,356(82.5％) boys and 499(17.5％) girls with a mean age of 2.44 ± 2.15 years.Laparoscopic examination identified CPPV in 1,469 (51.5 ％) cases,including 603 (41.0 ％) at right side and 866(59.0％) at left side.The incidence of CPPV was 53.4％ at right side and 50.2％ at left side (x2 =2.73,P＞0.05).No association existed between genders in CPPV (50.7％ vs 55.1％,P＞ 0.05).As compared with recurrence rate of open repair,a lower incidence exhibited for laparoscopic repair (0.25％ vs 1.02％,P＜0.01).However the time of postoperative recurrence had no statistical significance (t =1.04,P＞0.05).Furthermore,the incidence of MIH was 0.1％ after negative laparoscopy.And the risk ratio between the incidence of MIH and CPPV was 0.05 (95％CI:0.03-0.06).Conclusions The recurrence rate and incidence of MIH decreases more in laparoscopy than herniorrhaphy after repairing of pediatric unilateral inguinal hernia.Laparoscopy can easily detect contralateral patent processus vaginalis during hernia repairing.However,excessive treatment occurs during routine procedures.Despite a lower incidence of MIH,routine open contralateral inguinal exploration is not recommended for all cases of initial unilateral inguinal hernia.