***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: INTRODUCTION Since 1994 we perform laparoscopic total extraperitoneal hernia repair ( TEP ) for primary and recurrent inguinal hernias at our institution . The aim of this study was to investigate and compare the results of TEP in primary inguinal hernias and recurrent inguinal hernias and to determine whether there are differences in patient data , complication rates and outcome between these two groups . METHODS In a prospect i ve trial 338 patients were analyzed who underwent 500 laparoscopic TEP repairs .  In all , 431 TEP repairs were performed for primary inguinal hernias , and 69 for recurrent inguinal hernias . For data acquisition the SALTC study protocol was used . All patients were clinical ly examined 3 and 12 months after the operation . RESULTS The mean operation time was 67.3 min for TEP repair of primary hernias and 68.1 min for TEP repair of recurrent hernias , respectively . The conversion rate to an open procedure was 0 % . Conversion from TEP into TAPP was required in 0.5 % of patients with primary inguinal hernias and 1.4 % of patients with recurrent inguinal hernias . As the sole difference between the two groups the intraoperative complication rate could be identified . In the TEP repair group of recurrent inguinal hernias a higher incidence of injury to the peritoneum and a higher occurrence of bleeding from the epigastric vessels was found ( P = 0.03 ) . The postoperative complication rate was identical in the two groups , amounting to 5.1 % and 5.7 % , respectively . No differences were found in the 1 year follow-up between the two groups . The 1-year recurrence rate was 0.5 % for primary hernias . However , in the group of recurrent hernias there have been no recurrences to date . CONCLUSIONS The use of laparoscopic TEP repair has proven to be a safe and effective treatment in patients with primary and recurrent inguinal hernias . Because of scar tissue with possible adhesions a higher intraoperative complication rate was observed in the TEP repair of recurrent hernias than in TEP repair of primary inguinal hernias . However , no single recurrence was observed in the TEP repair group of recurrent hernias . In our opinion TEP is the optimal hernia repair for recurrent and bilateral inguinal hernias BACKGROUND For many years it has been cl aim ed that observational studies find stronger treatment effects than r and omized , controlled trials . We compared the results of observational studies with those of r and omized , controlled trials . METHODS We search ed the Abridged Index Medicus and Cochrane data bases to identify observational studies reported between 1985 and 1998 that compared two or more treatments or interventions for the same condition . We then search ed the Medline and Cochrane data bases to identify all the r and omized , controlled trials and observational studies comparing the same treatments for these conditions . For each treatment , the magnitudes of the effects in the various observational studies were combined by the Mantel-Haenszel or weighted analysis -of-variance procedure and then compared with the combined magnitude of the effects in the r and omized , controlled trials that evaluated the same treatment . RESULTS There were 136 reports about 19 diverse treatments , such as calcium-channel-blocker therapy for coronary artery disease , appendectomy , and interventions for subfertility .  In most cases , the estimates of the treatment effects from observational studies and r and omized , controlled trials were similar . In only 2 of the 19 analyses of treatment effects did the combined magnitude of the effect in observational studies lie outside the 95 percent confidence interval for the combined magnitude in the r and omized , controlled trials . CONCLUSIONS We found little evidence that estimates of treatment effects in observational studies reported after 1984 are either consistently larger than or qualitatively different from those obtained in r and omized , controlled trials Background : A variety of procedures with substantial differences in results are employed to treat recurrent inguinal hernia . The advantages of totally extraperitoneal patch repair ( TEP ) are even more evident when it is applied to recurrent compared to primary hernias . To investigate the superiority of this method more closely , we review ed our results obtained for recurrent inguinal hernias over a period of 2 years . Methods : We performed a prospect i ve single-center study using data obtained in consecutive patients with recurrent inguinal hernia who were operated on in 1997 and 1998 . Results : A total of 179 patients with recurrent inguinal hernia were recruited . Overall , 1329 patients with inguinal hernia were treated in the 2-year period , of whom 1270 underwent TEP .  The percentage of recurrent hernias was 14 % . The average age of the patients was 56 years . The follow-up rate was 87.5 % , and the mean follow-up period was 2.3 years . The 154 patients who were followed up underwent a total of 225 hernia repairs  , of which 181 were for recurrent hernias . The average operating time was 57 min . In 68 % ( 104/154 ) of the patients , adhesions , adherent epigastric vessels , or cicatricial changes were found , which result ed in the inadvertant opening of the peritoneum in 26.3 % of the patients . All the openings in the peritoneum were closed by endoscopic suturing . Intraoperative complications developed in 4 patients ( 2.3 % ) , including one injury to the bladder and three cases of bleeding from side branches of the epigastric vessels . The conversion rate was 0 % . The sole postoperative complication was treatment requiring hematomas in 7 patients , in 2 of whom reoperation became necessary . In both cases , a diffuse hemorrhage due to a preoperatively undiagnosed coagulation disorder was found . No cases of wound or patch infection were observed . In a patient undergoing both primary and recurrent hernia repair , displacement of a mesh led to a recurrence on the primary hernia side ( recurrence rate , 0.4 % ; re-recurrence rate , 0 % ) . Conclusions : Although for its definitive management , recurrent hernia requires a reliable operative technique , current data do not support the recommendation of any of the currently available procedures as the gold st and ard . In a representative patient population with recurrent hernia , we were able to demonstrate that TEP achieves very good results in terms of re-recurrence rate , intraoperative and postoperative complications , and rehabilitation . Prerequisites for the reliable and low-complication application of the method are a high level of st and ardization of the procedure and an advanced learning curve Evidence -based medicine ( EBM ) ranks different medical research methods on a hierarchy , at the top of which are r and omized controlled trials ( RCTs ) and systematic review s or meta-analyses of RCTs . Any study that does not r and omly assign patients to a treatment or a control group is automatically placed at a lower level on the hierarchy . This article argues that what matters is whether the treatment and control groups are similar with respect to potential confounding factors , not whether they got that way through r and omization . Moreover , nonr and omized studies tend to have other characteristics that make them useful sources of evidence , in that they tend to last longer and to enroll more patients than do r and omized trials . Replacing the sharp dichotomy between r and omized and nonr and omized studies with a continuum from “ clean ” studies ( which have high internal validity but whose results do not readily generalize to clinical practice ) to pragmatic studies ( which are design ed to more closely reflect clinical practice ) would also make a place for outcomes research and research using clinical data bases , which are not included in the current hierarchy of evidence but which can provide important information about the safety and efficacy of treatments Background : The aim of this study was to investigate the outcome of preperitoneal repair using laparoscopic ( TEP ) and open ( OPM ) approach in recurrent inguinal hernia . Methods : We performed a prospect i ve controlled nonr and omized clinical study in 188 patients with 207 recurrent inguinal hernias over a period of 5 years .  TEP repair was employed for 86 repairs , and OPM was used in 121 procedures . The main outcome measurements were : recurrence rate , operating time , hospital stay , and postoperative complications . Results : There were three recurrences ( 1.7 % ) . Two in the OPM group ( 1.8 % ) and one ( 1.3 % ) in the TEP group [ P = NS ( not significant ) ] . The TEP procedure was faster than OPM for unilateral repair ( 40.8 vs 46.3 min ) ( P<0.001 ) . Postoperative complications were more frequent in the OPM group ( 23.9 % ) than the TEP group ( 13.9 % ) ( P = NS ) . Hospital stay was significantly shorter in the TEP group ( 1.2 vs 3.9 days ) ( P<0.001 ) . Conclusions : Preperitoneal approach ( open or laparoscopic ) seems to be a good option in recurrent inguinal hernia when these procedures are done by experienced surgeons Introduction The Lichtenstein hernioplasty for the repair of primary inguinal hernia in male patients is well established and constitutes the current gold st and ard . However a gold st and ard technique for the repair of recurrent inguinal hernia has not been established . The aim of this study was to analyze the outcomes of Lichtenstein hernioplasty for the repair of primary inguinal hernia and recurrent inguinal hernia , applying for that purpose the Qualitative and Quantitative Measurement Instrument ( QQMI ) . Methods We studied 75 recurrent inguinal hernia patients and 287 primary inguinal hernia patients with a follow-up period ranging from 60 to 107 months . Results The final QQMI score demonstrated that most patients in both groups reached scores between 8 and 11 points , with a significant difference in the maximum score ( 11 points ) favoring primary hernia patients . Conclusions All evaluated parameters showed better outcomes in primary hernia patients . Applying the QQMI , we have demonstrated that the outcomes of  Lichtenstein hernioplasty  are not similar between primary and recurrent inguinal hernia ; there is a tendency toward better outcomes for primary inguinal hernia patients , although the Lichtenstein hernioplasty st and s as a safe option for repair of recurrent inguinal hernias Objective : To compare the Lichtenstein hernioplasty with a totally extraperitoneal preperitoneal laparoscopic technique ( TEP ) in treatment of recurrent inguinal hernias . Summary Background Data : Only a few studies thus far have compared an open and laparoscopic approach with the treatment of recurrent inguinal hernia in a prospect i ve r and omized study setting . Methods : Ninety-nine patients undergoing surgery for recurrent inguinal hernia were prospect ively r and omized into having either open or laparoscopic mesh repair .  Pre , peri- and postoperative factors were recorded in addition to 3-year follow-up data at the outpatient clinic . At 5–10 years , the patients were interviewed via telephone for recurrent symptoms . The primary end-points chosen were hernia recurrence and chronic pain . Results : Preoperative factors did not differ between the 2 groups . Rerecurrence rates were 3 in the Lichtenstein group and none in the TEP group ( 6.4 % versus 0.0 % , respectively ) , but this difference was statistically not significant . Chronic pain was more prevalent in the Lichtenstein group compared with the TEP group ( 13 [ 27.7 % ] versus 4 [ 8.2 % ] patients , respectively , P = 0.02 ) . Postoperatively , the Lichtenstein group needed more pain medication than the TEP group ( 4.4 versus 3.0 doses , respectively , P = 0.02 ) and returned to work later ( 17.9 versus 14.8 days , respectively , P = 0.05 ) . Conclusions : The laparoscopic technique with mesh in the treatment of recurrent inguinal hernia was proven superior to the open mesh repair in several important clinical aspects , with concomitant improvement in patient satisfaction Background Recurrences continue to be seen after repair of inguinal hernias . The repair of these recurrent hernias is a more complex and dem and ing procedure , with a high re-recurrence rate . Definite advantage has been demonstrated with endoscopic repair of these hernias . Methods The results for this prospect i ve study from January 2003 to December 2006 were evaluated after  laparoscopic repair of 65 recurrent hernias in 61 patients . The patients were followed up for 1 year . Longer follow-up evaluation was performed for the patients who underwent surgery in the initial 3 years . Results In this study , 37 recurrent hernias were managed using the transabdominal preperitoneal technique ( TAPP ) technique and 28 using the totally extraperitoneal ( TEP ) technique .  There was no conversion and no cases of postoperative wound infection . Of the 12 metachronous hernias repaired simultaneously , 3 were occult . Seroma developed in five patients . At a follow-up assessment after 1 year , one patient had groin pain , and there was one re-recurrence . A longer follow-up period with a mean of 35.11 months failed to show any new re-recurrence . Conclusions Laparoscopic repair of recurrent inguinal hernia is safe and effective . The morbidity and recurrence rates for the procedure are as low as for laparoscopic repair of primary hernias . Laparoscopic repair should be the gold st and ard for these hernias Background The optimal treatment for recurrent inguinal hernia is of concern due to the high frequency of recurrence . Methods This r and omized multicenter study compared the short- and long-term results for recurrent inguinal hernia repair by either the laparoscopic transabdominal 
    Output:
    
Comparisons of all outcomes in N RCTs and RCTs failed to show statistical significance .
Prospect ive/retrospective cohort studies , case series , and RCTs did not differ significantly in their estimates .
Adjusted testing for metaregression disclosed that rerecurrence among N RCTs was independent of the study design .
The number of included patients and study setting were independent predictors of outcome .