Wound infection following appendicectomy: The effect of extraperitoneal wound drainage and systemic antibiotic prophylaxis Abdominal Drainage Following Appendectomy and Cholecystectomy Laparoscopic Appendectomy Using Endoloops: A Prospective, Randomized Clinical Trial Initial laparoscopic appendectomy versus initial nonoperative management and interval appendectomy for perforated appendicitis with abscess: a prospective, randomized trial. Resource utilization and outcomes from percutaneous drainage and interval appendectomy for perforated appendicitis with abscess. Practical experience of a no abdominal drainage policy in patients undergoing liver resection. Peritoneal lavage versus drainage for perforated appendicitis in children Small lateral access--an alternative approach to appendicitis in paediatric patients: a randomised controlled trial. Appendiceal mass: conservative therapy followed by interval laparoscopic appendectomy. Subcuticular Skin Closure as a Standard Approach to Emergency Appendectomy in Children: Prospective Clinical Trial Safety of incidental appendectomy. Conservative approach versus urgent appendectomy in surgical management of acute appendicitis with abscess or phlegmon. Laparoscopy reduces unnecessary appendicectomies and improves diagnosis in fertile women The utility of peritoneal drains in children with uncomplicated perforated appendicitis Early appendectomy for perforated appendicitis in children should not be abandoned. Laparoscopy in children with complicated appendicitis. Prospective evaluation of nonsurgical versus surgical management of appendiceal mass.
The value of extraperitoneal wound drainage and a 3‐day course of prophylactic systemic cephaloridine used both separately and together have been assessed in a prospect i ve controlled r and omized trial involving 246 patients undergoing appendicectomy at the Leicester Royal Infirmary .  Extraperitoneal wound drainage was shown to reduce significantly the incidence of post‐operative wound infection in patients with a gangrenous or perforated appendix ( P<0·025 ) . Prophylactic cephaloridine significantly reduced the overall incidence of wound infection ( P<0·02 ) and was also effective when the appendix was gangrenous or perforated ( P<0·01 ) . A highly significant reduction in wound infection was achieved when the appendix was gangrenous or perforated by the addition of wound drainage to the antibiotic regimen ( P<0·001 ) Consecutive patients undergoing emergency appendectomy ( 283 ) or urgent cholecystectomy ( 51 ) were prospect ively studied for the development of postoperative incisional or peritoneal sepsis . Severity of the original peritoneal infection was carefully recorded , while use of a Penrose dam to drain the peritoneum was r and omized according to pre-assigned hospital number . Both aerobic and anaerobic cultures were taken from the abdomen at the time of operation as well as from all postoperative infectious foci . Results demonstrated no essential differences in incidence of wound and peritoneal infection following  appendectomy  for simple or suppurative appendicitis ( 187 ) or following  cholecystectomy  for acute cholecystitis ( 51 ) . However , with gangrenous or perforative appendicitis ( 94 ) , incisional and intra-abdominal infection rates were 43 % and 45 % , respectively , when a drain was used ; yet only 29 and 13 % , respectively , without a drain . These latter differences were significant ( p < 0.001 ) . In addition , intra-abdominal abscesses were three times as likely to drain through the incision than along any tract provided by the rubber conduit . Cultures revealed that hospital pathogens accounted for a greater proportion of wound and peritoneal sepsis after cholecystectomy and appendectomy for simple or suppurative appendicitis if a drain had been inserted than if managed otherwise . By contrast , a mixed bacterial flora was responsible for most infections following appendectomy for gangrenous or perforated appendicitis , irrespective as to use of a drain Background Inadequate closure of the appendix stump can lead to abscess formation or peritonitis . This prospect i ve r and omized clinical trial was performed to evaluate the number of endoloops needed in  laparoscopic appendectomy .  Methods A total of 208 patients were r and omized in two groups : 109 in group 1 using one and 99 in group 2 using two proximal endoloops . The groups were compared in terms of intra- and postoperative complications . Results Postoperative complications were found in five patients ( 4.6 % ) in group 1 , consisting of intraabdominal abscesses ( three patients ) , pulmonary embolism ( one patient ) , and persisting port-site pain ( one patient ) . In group 2 , postoperative complications were found in five patients ( 5.1 % ) , consisting of intraabdominal abscesses ( four patients ) and prolonged percutaneous drainage ( one patient ) . There was no significant difference between the two groups . Discussion In acute appendicitis , a minimal inflamed appendix base can be safely divided using one endoloop INTRODUCTION Perforated appendicitis is a common condition in children , which , in a small number of patients , may be complicated by a well-formed abscess . Initial nonoperative management with percutaneous drainage/aspiration of the abscess followed by intravenous antibiotics usually allows for an uneventful interval appendectomy . Although this strategy has become well accepted , there are no published data comparing initial nonoperative management ( drainage/interval appendectomy ) to appendectomy upon presentation with an abscess . Therefore , we conducted a r and omized trial comparing these 2 management strategies . METHODS After internal review board approval ( # 06 11 - 164 ) , children who presented with a well-defined abdominal abscess by computed tomographic imaging were r and omized on admission to laparoscopic appendectomy or intravenous antibiotics with percutaneous drainage of the abscess  ( when possible ) , followed by interval laparoscopic appendectomy approximately 10 weeks later . This was a pilot study with a sample size of 40 , which was based on our recent volume of patients presenting with appendicitis and abscess . RESULTS On presentation , there were no differences between the 2 groups regarding age , weight , body mass index , sex distribution , temperature , leukocyte count , number of abscesses , or greatest 2-dimensional area of abscess in the axial view . Regarding outcomes , there were no differences in length of total hospitalization , recurrent abscess rates , or overall charges . There was a trend toward a longer operating time in patients undergoing initial appendectomy ( 61 minutes versus 42 minutes mean , P = .06 ) . CONCLUSIONS Although initial laparoscopic appendectomy trends toward a requiring longer operative time , there seems to be no advantages between these strategies in terms of total hospitalization , recurrent abscess rate , or total charges OBJECTIVE Given the perceived technical dem and s of laparoscopic appendectomy and the expected postoperative morbidity in patients with a well-defined abscess , initial percutaneous drainage has become an attractive option in this patient population . This strategy allows for a laparoscopic appendectomy to be performed in an elective manner at the convenience of the surgeon . However , the medical burden on the patient and on the quality of patient outcomes has not been described in the literature . Therefore , we audited our experience with initial percutaneous drainage followed by laparoscopic interval appendectomy to evaluate the need for a prospect i ve trial . METHODS After institutional review board approval , a retrospective chart review was performed on all children who presented with perforated appendicitis and a well-defined abscess and were treated by initial percutaneous aspiration/drainage followed by interval appendectomy between January 2000 and September 2006 . Continuous variables are listed with st and ard deviation . RESULTS There were 52 patients with a mean age of 9.0 + /- 3.9 years and weight of 34.4 + /- 18.8 kg . The  mean duration of symptoms at presentation was 8.4 + /- 7.6 days . Percutaneous aspiration only was performed in 2 patients . The mean volume of fluid on initial aspiration/drain placement was 76.3 + /- 81.1 mL. The mean time to appendectomy was 61.9 + /- 25.2 days . The laparoscopic approach was used in 49 patients ( 94.2 % ) , of which one was converted to an open operation . The mean length of hospitalization after interval appendectomy was 1.4 + /- 1.4 days . A recurrent abscess developed in 17.3 % of the patients . Six patients ( 11.5 % ) required another drainage procedure . The mean total charge to the patients was $ 40,414.02 . There were 4 significant drain complications ( ileal perforation , colon perforation , bladder perforation , and buttock/thigh necrotizing abscess ) . The child with the ileal perforation after drain placement is the only patient who failed initial nonoperative therapy . CONCLUSIONS The use of initial percutaneous aspiration/drainage of periappendiceal abscess followed by interval appendectomy is an effective approach . However , this management poses complication risks and uses considerable re sources . Therefore , this strategy should be compared with early operation in a prospect i ve trial BACKGROUND / AIMS Routine use of abdominal drainage after liver resection is controversial . The aim of this study was to investigate the practical application of a " no abdominal drainage " policy for consecutive patients undergoing hepatic resection . METHODOLOGY The present trial included 60 consecutive patients who underwent elective hepatic resection . Fifty-two patients underwent no abdominal drainage  , and in the remaining eight drainage was necessary because of gross contamination of the surgical field associated with bilioenteric anastomosis , uncontrollable bile leakage from the cut surface of the liver , or the surgeon 's preference . Patient demographics , intraoperative data , and postoperative complications and mortality were evaluated . RESULTS There was no hospital death . Eight complications occurred in 8 patients in the no-drainage group ( morbidity rate 15.4 % , 8/52 ) : bleeding , abscess , ascites requiring peritoneal tap , pleural effusion requiring thoracentesis , and pneumonia in one case each , and three cases of wound infection . Three complications were encountered in 2 patients in the drainage group ( morbidity rate 25 % , 2/8 ) : bleeding , infected biloma and pleural effusion in one case each . Postoperative hospital stay tended to be shorter in the no-drainage group ( 10.7 + /- 3.9 days ) than in the drainage group ( 15.6 + /- 6.4 days ) ( p = 0.07 ) . Considering early uneventful removal of the drain on the morning of postoperative day 1 , half of the drained patients might have not required drainage . Furthermore , in the setting of concomitant bilioenteric anastomosis ( n=4 ) , one patient underwent hepatectomy uneventfully without drainage , and two of three patients with drainage had their drains removed successfully on day 1 . The third patient retained the drain for an unnecessarily long period , but did not develop subsequent complications . CONCLUSIONS Our data support the view that prophylactic abdominal drainage is unnecessary in most patients who undergo elective hepatic resection . Bilioenteric anastomosis may not be a contraindication for a no abdominal drainage policy A total of 231 children with acute appendicitis were treated at our hospitals during the 10 years between 1984 and 1993 , 53 of whom had a perforated appendix . These 53 patients were r and omly assigned to two groups at the time of surgery according to the different procedures performed . Thus , 29 children were managed by appendectomy followed by peritoneal lavage using a large amount of saline , and intravenous antibiotic therapy consisting of aminoglycoside and cephem ( lavage group ) , while the other 24 children were treated by appendectomy with silicon tube drainage and the same systemic antibiotic therapy ( drainage group ) . The mean length of hospitalization , and the mean duration s of fever and the need for fasting after laparotomy in the lavage group were significantly less than those in the drainage group : 10.1 versus 18.8 days , 2.8 versus 7.7 days , and 1.8 versus 3.5 days , respectively . The operation wounds healed well in the lavage group due to the fact that there was no drain . Wound infections occurred in two children from the lavage group and six from the drainage group . Intra-abdominal abscesses occurred in two children from the drainage group . Accordingly , peritoneal lavage appears to be superior to intraperitoneal tube drainage for the management of perforated appendicitis in children BACKGROUND Conventionally the appendix is removed through a right lower quadrant transverse incision or a gridiron incision approximately 5 cm in length . In this modern era of minimally invasive surgery , there is a lot of emphasis on cosmesis and early recovery . We performed a prospect i ve , double blind , r and omised trial to evaluate a new incision for appendectomy to compare with conventional appendectomy . METHODS One hundred and twenty patients , aged between 3 and 18 years , were r and omized to receive either small access appendectomy ( SAA ) ( n=60 , 53 acute appendicitis and 7 interval appendectomy ) or conventional appendectomy ( CAP ) ( n=60 , 55 acute appendicitis and 5 interval appendectomy ) .  SAA was performed through an incision in the lateral 1/3 of the spino-umbilical line , lateral to McBurney 's point . The caecum along with the appendix could be delivered through this small incision easily as the ileal loops did not interfere with the delivery . All patients suspected of acute appendicitis were evaluated by the modified Alvarado 's system to reduce the rate of negative appendectomies .  Patients with diffuse peritonitis were excluded . RESULTS The demographic data for the two groups were similar . The SAA group required less analgesics ( p<0.001 ) , had earlier ambulation and shorter hospital stay ( p<0.001 ) , and better cosmetic score ( p<0.001 ) , but the operation took longer ( p<0.001 ) compared to the CAP group . CONCLUSION We conclude that SAA can be done safely without the need for any special equipment , with definite advantages over conventional appendectomy BACKGROUND Current therapy of patients with appendiceal abscess or phlegmon is in evolution . Controversial areas include initial conservative therapy , drainage of periappendiceal abscesses , and the role of interval appendectomy . OBJECTIVE To evaluate the safety and efficacy of conservative therapy and of interval laparoscopic appendectomy ( ILA ) . PATIENTS AND METHODS Patients with signs and symptoms of acute appendicitis and a palpable right lower quadrant mass were included . Abscess/phlegmon was documented with ultrasound or computerized tomography . After initial therapy with antibiotics , patients were discharged to home . ILA was performed 6 to 12 weeks later . RESULTS Twelve patients were included . Four patients had phlegmonous appendicitis and eight had an abscess , but only four had percutaneous drainage . All patients improved without surgical exploration and were subjected to ILA . ILA was successful in 11 of 12 patients ; a median hospital postoperative stay of 1 day was required , and no perioperative morbidity was encountered . All patients returned to routine activities within 2 weeks of surgery . CONCLUSIONS 1 ) Initial conservative management of patients with appendiceal abscess/phlegmon is prudent , safe , and effective . 2 ) Interval laparoscopic appendectomy can be performed safely and effectively Abstract . We evaluated the morbidity associated with primary closure by interrupted subcuticular absorbable sutures  following emergency appendectomy .  In a prospect i ve clinical trial over a 12-month period , 216 children who underwent emergency appendectomy had skin closure using subcuticular interrupted absorbable polyglactin 4 - 0 sutures . Preoperative prophylactic antibiotics consisting of metronidazole alone or in combination with gentamicin were used in patients with suspected phlegmonous appendicitis ; a combination of metronidazole , gentamicin , and ampicillin was used when perforation of the appendix was suspected . Postoperatively , in patients with phlegmonous appendicitis  metronidazole was given for 24 hours , whereas in those with peritonitis the triple antibiotics were continued for 7 to 10 days . All patients were assessed for complications result ing from the technique of wound closure . No intraabdominal abscesses or serious complications were recorded . The overall incidence of wound infection was 1.8 % . Among children with a perforated appendix the rate of superficial wound infection was 5.7 % . There was no difference in the rate of wound infection between patients who received metronidazole alone or metronidazole plus gentamicin preoperatively . All the patients and their families were satisfied with the cosmetic results and with the fact that removal of skin sutures was unnecessary . We conclude that the use of prophylactic antibiotics permits st and ard skin closure by interrupted absorbable subcuticular suture Reports in the surgical literature are conflicting as to whether appendectomy " in passing " during laparotomy for trauma or for some other disease state does or does not significantly increase patient morbidity or mortality . A chart survey of all appendectomies ( 342 for acute appendicitis and 146 as incidental procedures ) performed on the trauma service of Grady Memorial Hospital over a 40 month period appeared to indicate that the wound infection rate ( 6.8 percent ) was the same as that for acute simple or suppurative appendicitis ( 6.7 percent ) , whereas the intraabdominal sepsis rate ( 17.5 percent ) paralleled that for more advanced gangrenous or perforative appendicitis ( 18.6 percent ) . Since the validity of a retrospective review is always open to question , a prospect i ve , r and omized trial was carried out only on patients with a negative abdominal exploration for trauma over a 22 month interval at the same trauma service . An odd second from the last digit hospital number dictated appendectomy , provided the appendix was readily accessible ; an even digit in the same locus dictated retention of the appendix . In no patient did intraperitoneal sepsis develop , regardless of the procedure chosen . Wound infection rates were 1.8 percent for appendectomy ( 1 of 56 ) , if local anatomic considerations precluded an easy appendectomy ( 0 of 45 ) , and 3.6 percent for the control subjects without appendectomy ( 3 of 83 ) . There were no deaths . These data cast considerable doubt on the reliability of retrospective review s and support the generally accepted dictum that incidental appendectomy , especially in the trauma patient , can be a relatively innocuous procedure BACKGROUND Surgical management of acute appendicitis with appendiceal abscess or phlegmon remains controversial . We studied the results of initial conservative treatment ( antibiotics and percutaneous drainage if necessary , with or without interval appendectomy ) compared with immediate surgery . METHODS We undertook an observational , retrospective cohort study of patients with a clinical and radiological diagnosis of acute appendicitis with an abscess or phlegmon , treated in our hospital between January 1997 and March 2009 . Patients younger than 14 , with severe sepsis or with diffuse peritonitis were excluded . A study group of 15 patients with acute appendicitis complicated with an abscess or phlegmon underwent conservative treatment . A control group was composed of the other patients , who all underwent  urgent appendectomy  , matched for age and later r and omized 1:1 . The infectious risk stratification was established with the National Nosocomial Infections Surveillance System ( NNIS ) index . Dependent variables were hospital stay and surgical site infection . Analysis was with SPSS , with p < 0.05 considered significant . RESULTS Interval appendectomy  was performed in 7 study group patients . Surgical site infection episodes were more frequent in the control group ( 6 vs. 0 , p < 0.001 ) . A greater percentage of high risk patients ( NNIS ≥ 2 ) was identified in the control group ( 80 vs. 28.7 % , p < 0.03 ) , mostly related with contaminated or dirty procedures in this group ( p < 0.001 ) . No significant difference between groups was found in hospital stay . CONCLUSION Initial conservative treatment should be considered the best therapeutic choice for acute appendicitis with abscess or phlegmon Background The aim of this study was to study the value of diagnostic laparoscopy prospect ively in fertile women scheduled for acute appendectomy . Methods For this study , 110 women , with acute abdominal pain ages 15 to 47 years , in whom the surgeon had decided to perform an appendectomy  , were r and omized to either open appendectomy or diagnostic laparoscopy , then open appendectomy if necessary . Results Appendicitis was diagnosed in 66 % of the women after open surgery , and in 73 % after laparoscopy . During laparoscopy , was appendicitis misdiagnosed in only 7 % of the women , from whom the appendix unnecessarily removed , whereas 34 % in the open surgery group had a healthy appendix removed . No appendicitis was missed in the laparoscopic group . The relative risk of removing a healthy appendix in open surgery was 6.6 relative risk ( range , 2–21 C.I. ) as compared with laparoscopy . Among the women with a healthy appendix , a gynecologic diagnosis was found in 73 % after laparoscopy , as compared with 17 % after open surgery . Conclusions Laparoscopy reduces unnecessary appendectomies and improves diagnosis in fertile women Peritoneal drainage in children with uncomplicated perforated appendicitis ( UPA ) is still controversial . Many pediatric surgeons prefer not to drain the peritoneal cavity in such cases . However , there is no r and omized controlled study performed in children . We aim ed to study the effects of peritoneal drainage in children with UPA in a r and omized prospect i ve trial . One hundred and forty consecutive patients with UPA were divided r and omly into 2 groups . Group I ( 70 patients ) consisted of cases with peritoneal drainage , and group II ( 70 patients ) without drainage . UPA is defined as perforated appendicitis with no more discoloration of peritoneal fluid after peritoneal wash out . Cases with localized abscess in the peritoneum were excluded from the study . In all patients , the ages , duration of symptoms , nasogastric drainage and hospitalization , and complications after surgery were recorded . The duration of hospitalization and nasogastric draining time were significantly lower in patients without peritoneal drainage . There was no difference in postoperative complications between the two groups . The onset of oral intake after surgery was significantly earlier in group II patients . Placing drains in the peritoneum does not improve outcome in UPA . Therefore , we do not recommend routine drainage of children with UPA Appendectomy for the diagnosis of appendicitis was prospect ively performed upon 133 children from 1 July 1982 to 30 June 1985 with no mortality . The pathologic diagnosis revealed 11 normal appendices ( 8.3 per cent ) , 54 instances of acute appendicitis ( 40.6 per cent ) , 16 instances of gangrenous appendicitis ( 12.0 per cent ) and 52 instances of perforated appendicitis ( 39.1 per cent ) . There were no complications in those patients with normal appendices , acute appendicitis and gangrenous appendicitis and the mean length of hospitalization for these groups was 3.27 , 3.37 and 4.75 days , respectively . The mean length of hospitalization for patients with perforated appendicitis was significantly longer , 9.45 days ( p less than 0.05 ) . Thirteen complications developed in 11 patients with perforated appendicitis . Eight patients required a reoperation ( a major morbidity rate of 15.4 per cent ) . There was only one readmission which occurred three and one-half weeks after discharge for intestinal obstruction . Early appendectomy in children with a presumed diagnosis of either acute or perforated appendicitis result ed in low morbidity rates and is more cost effective than nonoperative management proposed by others due to shorter hospitalization and no planned readmission BACKGROUND / PURPOSE Laparoscopic appendectomy is an accepted way of dealing with suspected uncomplicated appendicitis in children . The role of laparoscopy in complicated acute appendicitis is more controversial . The purpose of this trial was to compare laparoscopic appendectomy with open appendectomy in children with complicated appendicitis . METHODS A total of 102 children with suspected acute appendicitis were selected r and omly to undergo either a laparoscopic or an open appendectomy . The outcomes of 25 children with complicated appendicitis , 13 in the laparoscopic group and 12 in the open appendectomy group , were analyzed . Children , their parents , and research nurses were blinded to which procedure had been performed and remained blinded until the control visit 7 days after the operation . All 25 children completed a 30-day follow-up . RESULTS There were no differences in terms of patients ' age , sex , weight , height , and appendiceal histology between the 2 groups . All laparoscopic procedures were completed without conversion . The mean ( + /-SD ) operating time was 63 ( + /-31 ) minutes in the laparoscopic group and 37 ( + /-18 ) minutes in the open appendectomy group ( mean difference 26 minutes , 95 % CI 5 to 47 minutes , P = .02 ) . There were 2 major complications in the laparoscopic group in children with appendiceal masses . One child had an entero-cutaneous fistula of the residual appendiceal tip that needed open reoperation . Another child had a pelvic abscess that resolved with antibiotic treatment . Superficial wound infections were encountered in 2 patients in the open appendectomy group . CONCLUSIONS Laparoscopic appendectomy is an alternative to open procedure in children with complicated appendicitis . Good surgical judgement is necessary in patients with an established appendiceal abscess PURPOSE Prospect i ve evaluation was undertaken of surgical findings , complications , morbidity , and hospital stay between initial nonsurgical management versus early surgical intervention of an appendicular mass . METHODS A prospect i ve , nonr and omized study was conducted of 82 consecutive patients ( mean age , 6.9 + /- 3.3 years ) presenting with an appendicular mass over a 5-year period . They were categorized as group 1 , 58.5 % ( 48 of 82 ) nonsurgically managed and an interval appendectomy performed at a mean period of 8.6 + /- 4.6 weeks and group 2 , 41.5 % ( 34 of 82 ) appendectomy at presentation . RESULTS An appendix was identified in all 82 patients in both groups at operation . In-group 1 , recurrent episodes of abdominal pain necessitated interval appendectomy in 39.6 % ( 19 of 48 ) patients at a mean 4.3 + /- 0.8 versus 11.5 + /- 3.7 weeks in 60.4 % ( 29 of 48 ) who underwent scheduled interval appendectomy .  Periappendiceal abscesses present at interval appendectomy in group 1 was ( 38 of 48 ) 79.2 % versus 100 % ( 34 of 34 ) at appendectomy in group 2 . Adhesions at interval appendectomy  in group 1 was 81.3 % ( 39 of 48 ) versus 100 % ( 34 of 34 ) at appendectomy in group 2 . In-group 1 , superficial wound infection was observed in 0 versus 4 wound infections in group 2 . Overall morbidity rate between group 1 and group 2 was statistically significant ( P < .05 ) . Total mean hospital stay in group 1 was 13.2 + /- 1.5 versus 4.8 + /- 0.4 days in group 2 . Of the 48-interval appendectomy specimens , 37 of 48 ( 77 % ) appendices had a patent lumen , and 11 of 48 ( 23 % ) showed fibrosis and obliteration of appendicular lumen . There was no correlation ( r = 0.22 ) between the histopathologic findings and the interval between abscess treatment and interval appendectomy . CONCLUSIONS Early surgical intervention was beneficial over nonoperative management in this cohort of patients . Interval appendectomy is recommended after nonsurgical management of an appendicular mass
There were no significant differences between the two groups in the rates of intra-peritoneal abscess or wound infection .
It is not clear whether routine abdominal drainage has any effect on the prevention of intra-peritoneal abscess after open appendectomy for complicated appendicitis .
Abdominal drainage after an emergency open appendectomy may be associated with delayed hospital discharge for patients with complicated appendicitis
BACKGROUND Appendectomy , the surgical removal of the appendix , is performed primarily for acute appendicitis .
Patients who undergo appendectomy for complicated appendicitis , defined as gangrenous or perforated appendicitis , are more likely to suffer from postoperative complications .
The routine use of abdominal drainage to reduce postoperative complications after appendectomy for complicated appendicitis is controversial .
OBJECTIVES To assess the safety and efficacy of abdominal drainage to prevent intra-peritoneal abscess after open appendectomy for complicated appendicitis .