Risk Factors of Postoperative Infections in Adults withComplicated Appendicitis

Poon Chi Ming, MBBS, HK, FRCS Edin, General Surgery FHKAM,Tsang Yvonne Yee Yan, MBChB, MRCS Edin,

and Leong Heng Tat, MBBS, HK, FRCS Edin, FHKAM

Background: Acute appendicitis is the most common surgicalemergency. Infectious complications are uncommon but carrysignicant morbidity especially in complicated appendicitis. Thisstudy aimed to determine predictive factors of postoperativeinfections in adults with complicated appendicitis.

Method: Retrospective review of clinical records from CDARS ofHong Kong Hospital Authority was performed in all patients aged18 or above, operated with the diagnosis of gangrenous appendi-citis, acute appendicitis with generalized peritonitis or peritonealabscess from January 2003 to December 2005 in a regionalhospital. Primary end point was postoperative infections, includingwound infection and postoperative intra-abdominal abscess(PIAA). Independent predictors were determined by logisticregression analysis.

Results: One seventy-three patients were operated with thediagnosis of complicated appendicitis. Postoperative infectionsoccurred in 40 patients (23.1%). Thirty-two patients had woundinfection and 10 patients had PIAA. Two patients had bothinfectious complications. There were 2 deaths. Diabetes mellituswas the only signicant factor associated with PIAA in univariateanalysis (odds ratio, 6.6; 95% condence interval, 1.67-25.9). Noindependent factors can be identied in multivariate analysis.Successful laparoscopic appendicectomy was the only independentnegative risk factor of wound infection in logistic regression.

Conclusions: Laparoscopic appendicectomy is the rst choice ofprocedure in complicated appendicitis. Patients with diabetesmellitus need close monitoring of postoperative infections.

Key Words: complicated appendicitis, postoperative intra-abdom-

inal abscess, laparoscopic appendicectomy

(Surg Laparosc Endosc Percutan Tech 2009;19:244248)

Acute appendicitis is the one of the most commonsurgical emergencies we encounter in daily practice.Despite its favorable outcome, signicant morbidity canoccur especially in complicated appendicitis. Complicatedappendicitis which is dened as presence of acute appendi-citis with peritonitis, rupture, gangrene, or intra-abdominalabscess, accounts for 14% to 55% of all appendicitis.17

Complications, namely postoperative infection is morecommon in this group of patients.4,8,9 The high proportion

of complicated appendicitis has been evaluated in pastliteratures. Prehospital delay either due to patients delay oraccess to medical care is the major factor leading to theprogression from acute to perforated appendicitis.10 Re-search on postoperative infection has been performed in thepast with the aim to reduce its incidence and identifyreversible risk factors. Antibiotics prophylaxis is commonlygiven as 3-dose or a 5-day regimen depending on theseverity of appendicitis. This is shown to be eective in thereduction of postoperative infections in patients undergoingappendicectomy.11 Schmit et al9 reported that young ageand perforated appendicitis were signicant risk factorsof postoperative intra-abdominal abscess (PIAA) in acuteappendicitis. In an analysis of children with perforatedappendicitis, only intraoperative nding of fecolith anddiarrhea upon presentation were 2 risk factors of PIAA.12

As complicated appendicitis carries signicantly morecomplication than simple acute appendicitis, we aim toidentify risk factors of postoperative infections and analyzethe clinical outcomes of complicated appendicitis in thisstudy.

PATIENTS AND METHODSThis was a retrospective study in a regional hospital.

Patients aged 18 or above with the operative diagnosis ofgangrenous appendicitis, acute appendicitis with general-ized peritonitis (ICD 9 code of 540.0), acute appendicitiswith peritoneal abscess (ICD 9 code of 540.1) were retrievedfrom Clinical Data and Reporting System (CDARS) ofHong Kong Hospital Authority from 1 January 2003 to 31December 2005. Clinical and operative records werereviewed systematically.

Preoperative Diagnosis and PostoperativeManagement

Acute appendicitis was mainly diagnosed clinicallywith full history and physical examination. Preoperativeimaging would not be performed in patients with typicalhistory of right lower quadrant pain, localized tendernessor guarding at right lower quadrant. Ultrasound abdomenand pelvis may be performed in female if signs andsymptoms were equivocal to the concurrent diagnosis.Appendicular abscess and intra-abdominal abscess diag-nosed in preoperative imaging were all treated with surgeryin our hospital. Standardized intravenous antibiotics regi-men (Clavulenic acid plus amoxicillin 1.2 g) was given to allpatients on induction of general anesthesia. Patients withclinical diagnosis of peritonitis would receive same anti-biotics immediately and in regular regimen before surgery.Glucose levels of patients with diabetes mellitus (DM) wereCopyright r 2009 by Lippincott Williams & Wilkins

Received for publication June 9, 2008; accepted February 3, 2009.From the Department of Surgery, North District Hospital, Sheung

Shui, Hong Kong SAR, China.Reprints: Poon Chi Ming, MBBS, HK, FRCS, Edin, General Surgery

FHICAM, Associate Consultant, Department of Surgery, NorthDistrict Hospital, Sheung Shui, N.T., Hong Kong SAR, China(e-mail: mcmpoon@yahoo.com.hk).

ORIGINAL ARTICLE

244 | www.surgical-laparoscopy.com Surg Laparosc Endosc Percutan Tech Volume 19, Number 3, June 2009

controlled by dextrose-potassium-insulin intravenous infu-sion according to hospital guideline.

Upon discharge from hospital, occurrence of woundinfection was reported by nursing sta according to surgicalsite infection surveillance. All patients would be seen inoutpatient clinic in 3-4 weeks time to see the pathologyreport and any delayed wound infection.

Variables and StatisticsSix preoperative variables including patients sex, age

more than 65, clinical presentation of peritonitis, ASAclass, presence of DM and presence of comorbidity wereidentied. Operative variables included level of operatingsurgeons, duration of operation, start time of operationbefore or after midnight, operative ndings of ruptured organgrenous appendix, presence of appendicular abscess orintra-abdominal abscess, positive culture of peritonealswab, type of surgical procedures, and intraoperativeperitoneal lavage. Primary end point was postoperativeinfections, which included wound infection and PIAA. Therelationship between the above variables and postoperativeinfections were analyzed by w2 test or Fisher exact test asappropriate in univariate analysis. Signicant variableswere entered into logistic regression analysis to identifyindependent risk factors of postoperative infections. A Pvalue

appendicitis.4,8,9 In our hospital, complicated appendicitisaccounts for 26% of total appendicitis. Wound infectionoccurs in one-fth of patients with complicated appen-dicitis, which is comparable to other publications.8,1315

Successful LA is the only independent negative risk factorof wound infection. The protective eect of LA in woundinfection is not a new nding. Compared with openappendicectomy (OA), LA has signicantly reduction ofwound infection by 60%, and decreased the absolute riskfor wound infection by 3.2% in meta-analysis.3,1618 Suchprotective eect in wound infection is also true incomplicated appendicitis. Comparison between LA versusOA in complicated appendicitis showed that LA group hassignicantly lower wound infection rate.1315 Incidence ofwound infection in OA was as high as 3 times more thanthat in LA (6.8% vs. 23%).14 Our study conrms only LAcan reduce wound infection in complicated appendicitis.Other common clinical factors including old age, DM andlong operative time were studied but they have noassociation with wound infection. Contrary to the tradi-tional belief, diabetic patients are not increased in risk of

wound infection in our study. It may be explained by thecomparable positive peritoneal swab culture betweenpatients with and without DM (14/19 vs. 88/154,P=0.17). DM is not associated with positive peritonealswab culture, which is one of the signicant factors inunivariate analysis. As wound contamination is similar inpatients with and without DM, it seems reasonable thatwound infection rate should be comparable. Rupturedappendix is commonly believed as a major factor ofpostoperative infection. Previous study suggested rupturedappendix was an independent predictor of PIAA.9 In ourstudy, gangrenous appendix is not a signicant factor ofwound infection in univariate analysis. Ruptured appendixis signicantly associated with wound infection, but it is notan independent factor in logistic regression. Thus, statusof appendix is not considered as a predictor of woundinfection in complicated appendicitis. Successful LA is thesingle independent factor to reduce wound infection.

Despite the advantage fore-mentioned in LA, the useof LA is still controversial in complicated appendicitiswith regard to the incidence of PIAA. Paik et al foundLA signicantly increased PIAA rate (9% vs. 2.6%) inperforated appendicitis compared with OA in adults.3

TABLE 3. Demographic Variables and Operative Findings inRelation to Wound Infection

Wound Infection

Variables No Yes P

Sex Male 75 24 0.024Female 66 8

Age >65 No 109 25 0.92Yes 32 7

Peritonitis No 102 17 0.036Yes 39 15

ASA 1 or 2 126 28 0.763 or 4 15 4

Comorbidity No 117 28 0.51Yes 24 4

Diabetes mellitus No 126 28 0.76Yes 15 4

Ruptured appendix No 45 3 0.009Yes 96 29

Gangrenous appendix No 92 15 0.053Yes 49 17

Appendicular abscess No 70 15 0.78Yes 71 17

Pelvic abscess No 121 23 0.057Yes 20 9

Intra-abdominal abscess No 118 20 0.008Yes 23 12

Total intra-abdominalabscess (including

No 49 8 0.29

Appendicular and pelvicabscess)

Yes 92 24

Positive peritoneal swabculture

No 63 8 0.04

Yes 78 24Surgical specialists aschief surgeon

No 95 22 0.88

Yes 46 10Operation time morethan 60min

No 55 10 0.44

Yes 86 22Operation start timeafter midnight

No 112 22 0.17

Yes 29 10

P

Similar nding was also noted in children, with a relativerisk of 5.6.6 The increase in PIAA was signicantly raised inLA group by 2.26 folds in a recent meta-analysis.19 On thecontrary, recent studies suggested a comparable or even lessincidence of PIAA in LA.20,21 In an international study of1017 patients with complicated appendicitis managed withLA, only 2.8% had PIAA.7 Mancini et al also hadencouraging results in a retrospective cohort of 92 patientswith complicated appendicitis receiving LA. Total compli-cation rate was 8.9%, compared with 50% in historicalcontrol of OA.22 The advantage of LA over OA wasconsolidated in an analysis of 43757 patients from a largeadministrative database. After covariates adjustment, LAwas associated with lower rate of infections and loweroverall complications.23 Thus, LA should be the rst choiceof procedure in complicated appendicitis.

The common thought of peritoneal irrigation andpresence of intra-abdominal abscess as causes of PIAA isdisproved in our study. Peritoneal irrigation was blamedcausing PIAA due to incomplete suction of irrigated uid.However, both the use of peritoneal irrigation and thevolume of warm saline consumed in irrigation are notassociated with PIAA in univariate and multivariateanalysis. Operative nding of intra-abdominal abscess wasthought to increase the risk of PIAA due to contaminationof peritoneal cavity. In our study, patients with intra-abdominal abscess, appendicular abscess or pelvic abscessare not associated with PIAA. DM is the only signicantfactor associated with PIAA. Risk of PIAA in DM patientswas increased by 6.6 folds. Diabetic patients are known tohave increased risk of infection and failure of woundhealing. A study on surgical site infections showed DM wasone of the signicant predictors.24 Our study suggestsdiabetic patients are more prone to deep infection insteadof supercial infection. Despite the signicant associationbetween DM and PIAA, no independent predictors can befound in logistic regression. This is similar to the ndings inchildren by Henry et al.12 Common clinical factors were notreliable predictors of PIAA. Nevertheless, Diabetic patientsshould be closely monitored for PIAA in postoperativecourse.

We had a high conversion rate of 54.3% in LA group.Of the 116 patients receiving LA, 33 patients wereconverted to midline laparotomy and 30 patients were

converted to gridiron incision. The reasons of conversionincluded (1) gross contamination that was not amendableto clean up by laparoscopy (2) severe inammation ledto dicult dissection, and (3) unhealthy appendicealstump which required additional procedure to secure. Openconversion has been suggested to account for postoperativeinfection. Piskun et al25 found converted group had asignicantly higher rate of PIAA and wound infectioncompared with LA group. Long operative time and spreadof infection within peritoneal cavity before wound incisionand protection were hypothesized to explain more post-operative infection in converted group. In our study,conversion to midline laparotomy from laparoscopy wasalso signicantly associated with wound infection, but it isnot an independent factor to predict wound infection.Intention-to-treat analysis of LA group, which includedconversion from LA to either gridiron incision or midlinelaparotomy is not associated with either wound infectionor PIAA. Open conversion should not be considered asthe reason to avoid LA in complicated appendicitis. Toconclude, LA is safe and eective in prevention of wound

TABLE 5. Logistic Regression Analysis to Predict Wound Infection

95% CI for Exp (B)

Factors P Exp (B) Lower Upper

Sex 0.13 0.48 0.18 1.24Peritonitis 0.76 1.15 0.46 2.88Ruptured appendix 0.059 3.79 0.95 15.11Intra-abdominalabscess

0.61 1.3 0.48 3.52

Laparoscopicappendicectomy

0.022 0.08 0.009 0.695

Conversion to midlinelaparotomy fromlaparoscopy

0.38 1.73 0.52 5.83

Positive peritonealswab culture

0.41 0.63 0.21 1.88

Total midlinelaparotomy

0.58 1.4 0.43 4.62

P 65 No 127 7 0.56Yes 36 3

Peritonitis No 111 7 0.92Yes 51 3

ASA 1 or 2 146 8 0.353 or 4 17 2

Comorbidity No 138 7 0.22Yes 25 3

Diabetes mellitus No 148 6 0.002Yes 15 4

Ruptured appendix No 46 2 0.57Yes 117 8

Gangrenous appendix No 102 5 0.43Yes 61 5

Appendicular abscess No 79 6 0.53Yes 84 4

Pelvic abscess No 135 9 1.0Yes 28 1

Intra-abdominal abscess No 129 9 0.69Yes 34 1

Total intra-abdominalabscess

No 51 6 0.08

(including appendicularand pelvic abscess)

Yes 112 4

Positive peritoneal swabculture

No 65 6 0.32

Yes 98 4Surgical specialists aschief surgeon

No 111 6 0.60

Yes 52 4Operation time morethan 60min

No 59 5 0.50

Yes 103 5Operation start timeafter midnight

No 124 10 0.12

Yes 38 0

P

infection in complicated appendicitis. Open conversion willnot increase the risk of postoperative infection. None ofclinical factors can predict PIAA in complicated appendi-citis. DM patients are more prone to PIAA and should becarefully monitored in their postoperative course.

REFERENCES

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2. Chung KM, Lee SW, Chia NH, et al. Acute appendicitisa recent audit of an old problem. Hong Kong Med J. 1997;3:149152.

3. Paik PS, Towson JA, Anthone GJ, et al. Intra-abdominalabscesses following laparoscopic and open appendectomies.J Gastrointest Surg. 1997;1:188192.

4. Reid RI, Dobbs BR, Frizelle FA. Risk factors for post-appendicectomy intra-abdominal abscess. Aust N Z J Surg.1999;69:373374.

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6. Krisher SL, Browne A, Dibbins A, et al. Intra-abdominalabscess after laparoscopic appendectomy for perforatedappendicitis. Arch Surg. 2001;136:438441.

7. Cueto J, DAllemagne B, Vazquez-Frias JA, et al. Morbidity oflaparoscopic surgery for complicated appendicitis: an inter-national study. Surg Endosc. 2006;20:717720.

8. Wullstein C, Barkhausen S, Gross E. Results of laparoscopicversus conventional appendectomy in complicated appendici-tis. Dis Colon Rectum. 2001;44:17001705.

9. Schmit PJ, Hiyama DT, Swisher SG, et al. Analysis of riskfactors of postappendectomy intra-abdominal abscess. J AmColl Surg. 1994;179:721726.

10. Temple CL, Huchcroft SA, Temple WJ. The natural historyof appendicitis in adults. A prospective study. Ann Surg. 1995;221:278281.

11. Andersen BR, Kallehave FL, Andersen HK. Antibiotics versusplacebo for prevention of postoperative infection afterappendicectomy. Cochrane Database Syst Rev. 2005;20:CD001439.

12. Henry MC, Walker A, Silverman BL, et al. Risk factors for thedevelopment of abdominal abscess following operation forperforated appendicitis in children: a multicenter case-controlstudy. Arch Surg. 2007;142:236241.

13. Lin HF, Wu JM, Tseng LM, et al. Laparoscopic versus openappendectomy for perforated appendicitis. J Gastrointest Surg.2006;10:906910.

14. Yagmurlu A, Vernon A, Barnhart DC, et al. Laparoscopicappendectomy for perforated appendicitis: a comparison withopen appendectomy. Surg Endosc. 2006;20:10511054.

15. So JB, Chiong EC, Chiong E, et al. Laparoscopic appendect-omy for perforated appendicitis. World J Surg. 2002;26:14851488.

16. Sauerland S, Lefering R, Holthausen U, et al. Laparoscopicversus conventional appendectomya meta-analysis of rando-mised controlled trials. Langenbecks Arch Surg. 1998;383:289295.

17. Garbutt JM, Soper NJ, Shannon WD, et al. Meta-analysis of randomized controlled trials comparing laparo-scopic and open appendectomy. Surg Laparosc Endosc. 1999;9:1726.

18. Chung RS, Rowland DY, Li P, et al. A meta-analysis ofrandomized controlled trials of laparoscopic versus conven-tional appendectomy. Am J Surg. 1999;177:250256.

19. Bennett J, Boddy A, Rhodes M. Choice of approach forappendicectomy: a meta-analysis of open versus laparoscopicappendicectomy. Surg Laparosc Endosc Percutan Tech. 2007;17:245255.

20. Ball CG, Kortbeek JB, Kirkpatrick AW, et al. Laparoscopicappendectomy for complicated appendicitis: an evaluation ofpostoperative factors. Surg Endosc. 2004;18:969973.

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22. Mancini GJ, Mancini ML, Nelson HS Jr. Ecacy oflaparoscopic appendectomy in appendicitis with peritonitis.Am Surg. 2005;71:14.

23. Guller U, Hervey S, Purves H, et al. Laparoscopic versus openappendectomy: outcomes comparison based on a largeadministrative database. Ann Surg. 2004;239:4352.

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25. Piskun G, Kozik D, Rajpal S, et al. Comparison oflaparoscopic, open, and converted appendectomy for perfo-rated appendicitis. Surg Endosc. 2001;15:660662.

TABLE 7. Surgical Procedures in Relation to Postoperative Intra-abdominal Abscess

Wound Infection

Variables No Yes P

Total Laparoscopy No 54 3 1.0Yes 109 7

Midline laparotomy No 126 8 10Yes 37 2

Gridiron incision No 146 9 1.0Yes 16 1

Successful laparoscopicappendicectomy

No 114 6 0.50

Yes 49 4Conversion to midlinelaparotomy from

No 130 10 0.21

laparoscopy Yes 33 0Conversion to gridironincision from

No 136 7 0.38

laparoscopy Yes 27 3Total midlinelaparotomy (include

No 92 8 0.19

conversion group fromlaparoscopy

Yes 71 2

Total gridiron incision(include conversion

No 118 6 0.47

group from laparoscopy) Yes 45 4Right hemicolectomy No 158 10 1.0

Yes 5 0Peritoneal lavage morethan 6L of

No 130 10 0.21

normal saline Yes 32 0Peritoneal lavage lessthan 6L of

No 75 4 0.76

normal saline Yes 88 6Peritoneal lavage No 43 4 0.46

Yes 120 6

Ming et al Surg Laparosc Endosc Percutan Tech Volume 19, Number 3, June 2009

248 | www.surgical-laparoscopy.com r 2009 Lippincott Williams & Wilkins