Incisional hernia is one of the most frequent complications of abdominal surgery. A meta-regression of 14,618 patients estimated its prevalence after midline laparotomy at 12.8% after about two years [1], and in two trial cohorts followed for three years the rate rose from 12.6% at one year to 22.4% at three years [2]. Early prospective studies had already shown that hernias continue to appear for many years after surgery. Bucknall and colleagues found incisional hernia in 7.4% of 1129 laparotomy wounds at one year [3], and Mudge and Hughes reported that 35% of hernias seen over 10 years first appeared at five years or later [4]. The burden of incisional hernia is considerable. Most hernias cause symptoms, and patients with a hernia report poorer physical function and body image than those without one [5]. Repair is not always durable: in a population-based study, 12.3% of patients needed another repair within five years [6], and in a randomised trial the 10-year recurrence rate was 63% after suture repair and 32% after mesh repair [7]. Large defects are difficult to reconstruct [8]. Prevention is therefore better than repair.

Several risk factors have been described. Patient factors include higher age, male sex, obesity, smoking, anaemia and chronic pulmonary disease [9-12]. Operative factors include emergency surgery, a midline rather than transverse incision, previous laparotomy and the closure technique [13-15]. Surgical site infection is one of the strongest and most consistent predictors [16,17]. Most of this evidence comes from Europe, North America and Japan [16,18]. In Indian public teaching hospitals, a large share of laparotomies are emergency procedures and anaemia, malnutrition and wound infection are common, so the incidence and the relative weight of each factor may differ. The aim of this study was to measure the incidence of incisional hernia after midline laparotomy in a tertiary care hospital in western India and to identify the factors associated with its development.

Study design and setting This prospective observational study was conducted in the Department of Surgery, Smt. Kashibai Navale Medical College and General Hospital, Pune, a tertiary care teaching hospital. Written informed consent was obtained from every participant, or from a relative when the patient could not consent before emergency surgery, in which case the patient’s own consent was taken after recovery. Participants All patients aged 18 years or more who underwent elective or emergency laparotomy through a midline incision were eligible. Patients were excluded if they had an existing incisional or ventral hernia at the operative site, had prophylactic mesh placed at closure, had the abdomen left open or closed with a temporary closure device, died within 30 days of surgery, or did not consent to follow-up. Sample size The sample size was calculated from an expected incidence of 12.8% at about two years after midline laparotomy [1]. With an absolute precision of 5% and a 95% confidence level, the formula n = Z² p (1 - p) / d² gave a minimum of 172 patients. Allowing for 10% loss to follow-up, the target sample size was 190 patients. Data collection Data were recorded on a predesigned proforma. Patient variables were age, sex, body mass index (BMI), smoking, diabetes mellitus, hypertension, chronic obstructive pulmonary disease, preoperative haemoglobin, serum albumin, American Society of Anesthesiologists (ASA) grade and previous abdominal surgery. Operative variables were the type of surgery (elective or emergency), indication, wound class, position of the incision (upper, lower or full-length midline), suture material, closure technique, duration of surgery and the suture length to wound length ratio where it was measured [19]. Postoperative variables were surgical site infection, burst abdomen, persistent cough, postoperative ileus, relaparotomy and length of hospital stay. Closure technique The fascia was closed by the operating surgeon. The standard technique in the unit was a continuous mass closure with a slowly absorbable polydioxanone or a non-absorbable polypropylene suture, as recommended by current guidelines [15]. The suture material and technique used in each patient were recorded rather than controlled. Definitions Incisional hernia was defined as any abdominal wall gap, with or without a bulge, in the area of a postoperative scar, perceptible or palpable on clinical examination or imaging [20]. Surgical site infection was defined according to the Centers for Disease Control and Prevention criteria and classified as superficial incisional, deep incisional or organ space [21]. Burst abdomen was defined as postoperative separation of the abdominal fascia requiring intervention [22]. Obesity was defined as BMI of 30 kg/m2 or more, and anaemia as a haemoglobin level of less than 10 g/dL. Hypoalbuminaemia was defined as a serum albumin level of less than 3.5 g/dL. Follow-up and outcome assessment Patients were reviewed at discharge and at 1, 3, 6 and 12 months after surgery. At each visit, the wound was examined with the patient standing and supine, and during a Valsalva manoeuvre or cough. Ultrasonography of the abdominal wall was done when the clinical examination was doubtful, in obese patients and at the final visit [23]. Patients who did not attend were contacted by telephone and asked to return. The primary outcome was the development of incisional hernia within the follow-up period. Secondary outcomes were the time to diagnosis of hernia, the size and site of the defect, and the association of each recorded variable with hernia. Statistical analysis Data were entered in Microsoft Excel and analysed with Python version 3.13 using the SciPy and statsmodels libraries. Continuous variables were expressed as mean and standard deviation or median and interquartile range, and categorical variables as number and percentage. Incidence was reported with an exact (Clopper-Pearson) 95% confidence interval. Patients with and without hernia were compared with the chi-square test, or the Fisher exact test when any expected cell count was below 5, for categorical variables and the independent t-test or Mann-Whitney U test for continuous variables. Variables with p < 0.20 on univariate analysis were entered into a multivariable logistic regression model, and results were expressed as adjusted odds ratios (aOR) with 95% confidence intervals. Model fit was assessed with the Hosmer-Lemeshow test. A p-value below 0.05 was considered significant.

Participants

A total of 190 eligible patients who underwent midline laparotomy were enrolled. Of these, 173 (91.1%) completed the 12-month follow-up and were included in the analysis, and 17 (8.9%) were lost to follow-up.

Baseline characteristics

The mean age of the patients was 46.2 ± 17.3 years, and 100 (57.8%) were men (Table 1). Thirty-one patients (17.9%) were obese, 33 (19.1%) were smokers and 25 (14.5%) had diabetes mellitus. Eighty operations (46.2%) were emergency procedures. The most common specified indications were malignancy (31.8%) and intestinal obstruction (19.1%), followed by perforation peritonitis (12.7%); the remaining 36.4% had other indications (Table 2). Surgical site infection occurred in 27 patients (15.6%): superficial incisional in 18, deep incisional in 7 and organ space in 2.

Table 1. Baseline characteristics of the study patients

BMI: body mass index; ASA: American Society of Anesthesiologists; SD: standard deviation.

Table 2. Operative and postoperative characteristics

IQR: interquartile range; SD: standard deviation. Incision and suture rows show numbers in the order listed.

Incidence and timing of incisional hernia

Incisional hernia developed in 18 of 173 patients, giving an incidence of 10.4% (95% CI 6.3 to 15.9). Thirteen hernias (72.2%) were diagnosed by clinical examination and 5 (27.8%) only on ultrasonography. Two (11.1%) were detected by 1 month, 8 (44.4%) by 3 months, 15 (83.3%) by 6 months and all 18 by 12 months. The most common site was the lower part of the incision (6 hernias), followed by the umbilical region (5), and the median defect width was 4.6 cm (Table 3). Ten hernias (55.6%) were symptomatic.

Table 3. Incidence, timing and features of incisional hernia

Incidence is expressed as a percentage of the 173 patients who completed follow-up; other percentages are of the 18 hernias. CI: confidence interval; IQR: interquartile range.

Factors associated with incisional hernia

On univariate analysis, incisional hernia was significantly more common after emergency surgery (17.5% vs 4.3%, p = 0.005), after interrupted fascial closure (21.9% vs 7.8%, p = 0.047) and in patients with surgical site infection (Table 4). Hernia occurred in 25.9% of patients with surgical site infection and in 7.5% of those without it (p = 0.010). Smoking (18.2% vs 8.6%, p = 0.117) and ASA grade III or IV (15.3% vs 7.9%, p = 0.133) showed non-significant trends. Age, sex, obesity, diabetes, anaemia, hypoalbuminaemia and wound class were not associated with hernia.

Table 4. Univariate analysis of factors associated with incisional hernia

Chi-square test, or Fisher exact test when any expected cell count was below 5. ASA: American Society of Anesthesiologists.

On multivariable logistic regression, surgical site infection (aOR 4.12, 95% CI 1.19 to 14.31; p = 0.026), emergency surgery (aOR 3.73, 95% CI 1.09 to 12.83; p = 0.037) and interrupted fascial closure (aOR 3.48, 95% CI 1.08 to 11.15; p = 0.036) remained independent risk factors (Table 5). Smoking showed a borderline association (aOR 3.44, 95% CI 1.00 to 11.87; p = 0.051), and ASA grade III or IV was not significant after adjustment.

Table 5. Multivariable logistic regression of risk factors for incisional hernia

Variables with p < 0.20 on univariate analysis were entered into the model. OR: odds ratio; CI: confidence interval; ASA: American Society of Anesthesiologists. Model fit: Hosmer-Lemeshow p = 0.69; area under the ROC curve 0.78.

In this prospective study of 173 patients, incisional hernia developed in 10.4% within 12 months of midline laparotomy. Surgical site infection, emergency surgery and interrupted fascial closure were independent predictors of hernia. The incidence in this study is within the range reported in most series. The meta-regression by Bosanquet and colleagues found a pooled prevalence of 12.8% at about two years, with a range from 0 to 35.6% across studies [1]. Itatsu and colleagues reported 5.2% at 12 months and 10.3% at 24 months in a prospective Japanese cohort of 3927 patients [16], and Hoer and colleagues found 9.8% at a mean of 21 months in 2983 patients [9]. Rates are higher when imaging is used and when follow-up is longer. In a pooled analysis of two trials, the hernia rate rose by more than 60% between the first and third year [2]. Because our follow-up was limited to 12 months, the true long-term incidence in our patients is likely to be higher. Our 12-month rate was twice the 5.2% reported by Itatsu and colleagues at the same interval [16]. Two features of our cohort probably explain this: almost half of the operations (46.2%) were emergency procedures, and ultrasonography at the final visit detected 5 of the 18 hernias (27.8%) that were not evident on clinical examination. Surgical site infection was a strong predictor in our study: hernia developed in 25.9% of patients with infection and in 7.5% of those without it, and infection remained independent after adjustment (aOR 4.12). This finding agrees with previous work. In the Japanese cohort, incisional surgical site infection increased the hazard of hernia by 1.68 times, and deep infection had a stronger effect than superficial infection [16]. Veljkovic and colleagues included deep surgical site infection in their hernia risk score [17], and a review of the French literature found infectious complications to be an independent risk factor [13]. Infection weakens the healing fascia and loosens the suture line. In our hospital, emergency operations for contaminated or dirty conditions are common, which may explain the 15.6% infection rate. Obesity was not a significant risk factor in our study, although the hernia rate was higher in obese patients (16.1% vs 9.2%, p = 0.325). A BMI of 25 kg/m2 or more increased the hazard of hernia by 1.76 times in one cohort [16] and by 1.74 times in the HERNIA Project [11], and BMI above 24.4 kg/m2 was one of four predictors in the score by Veljkovic and colleagues [17]. A thick subcutaneous layer raises tension on the closure and increases the risk of infection. Higher age and male sex were associated with hernia in several studies [9,10,12], but in our study neither age above 60 years (14.6% vs 9.1%, p = 0.379) nor male sex (11.0% vs 9.6%, p = 0.764) was significant. Smoking increased the risk four-fold in a Danish study [10]; in our study smokers had about twice the hernia rate of non-smokers (18.2% vs 8.6%), and the association was of borderline significance after adjustment (aOR 3.44, p = 0.051). Anaemia and chronic pulmonary disease, which were not significant in our analysis, have been linked both to incisional hernia [9,11] and to burst abdomen [22,24]. With only 18 hernias, our study had limited power to detect moderate effects of these patient factors. Emergency surgery was a significant factor: hernia developed in 17.5% of patients after emergency surgery and in 4.3% after elective surgery, and the association persisted after adjustment for wound infection (aOR 3.73). Emergency patients often have peritonitis, distension, malnutrition and poor general condition, all of which impair wound healing [22,24]. The European Hernia Society could give no recommendation on the best way to close emergency laparotomy incisions because of the lack of evidence [15]. Previous laparotomy, which was a risk factor in earlier studies [9,10], was not significant in our patients (8.6% vs 10.9%, p = 1.000). Closure technique is the risk factor that surgeons can change most easily. Continuous closure with a slowly absorbable suture reduces hernia compared with interrupted or rapidly absorbable sutures [25,26], although the type of slowly absorbable or non-absorbable suture made little difference in a large randomised trial [27]. The suture length to wound length ratio should be at least 4 [15,19]. In randomised trials, small stitches reduced incisional hernia from 18.0% to 5.6% [28] and from 21% to 13% [29], and with small stitches no other risk factor predicted hernia or infection [30]. In our study, 81.5% of wounds were closed with a continuous technique and 65.3% with polydioxanone. Interrupted closure was associated with a hernia rate of 21.9% compared with 7.8% after continuous closure, and it remained an independent risk factor (aOR 3.48). A suture length to wound length ratio below 4 was not associated with hernia in our data (7.8% vs 11.9%, p = 0.450), although the small number of events limits this comparison. The small bites technique is simple and cheap and should be adopted as the standard closure in our unit. Where possible, a transverse incision gives a lower hernia rate than a midline incision [14,15]. This study has clinical implications. Patients with the identified risk factors can be counselled before surgery, closed with the small bites technique and followed more closely. Prophylactic mesh can be considered in the highest-risk patients, as suggested by the European guidelines [15]. Many of the patient factors, such as obesity, smoking, anaemia and poor nutrition, can be improved before elective surgery. Better prevention and treatment of wound infection would also lower the hernia rate. Strengths and limitations The main strengths of this study are its prospective design, the use of standard definitions of hernia and wound infection [20,21], and the use of ultrasonography to confirm doubtful cases [23]. It also has limitations. It was done in a single centre, and the closure technique was not standardised. Follow-up was limited to 12 months, and almost half of incisional hernias appear after the first year [4,9], so the incidence is likely to be an underestimate. Ultrasonography was not done in every patient at every visit. Seventeen patients (8.9%) were lost to follow-up. With only 18 hernias, the number of variables that could be included in the regression model was limited, and the wide confidence intervals of the adjusted odds ratios should be interpreted with caution.

Incisional hernia developed in 10.4% of patients within 12 months of midline laparotomy at our tertiary care hospital. Surgical site infection, emergency surgery and interrupted fascial closure were independent risk factors. Careful continuous closure with the small bites technique, prevention and early treatment of surgical site infection, preoperative optimisation of modifiable factors and longer follow-up of high-risk patients are recommended. A larger multicentre study with follow-up of at least three years is needed.

DECLARATIONS

Acknowledgement: The author thanks the faculty, residents and nursing staff of the Department of Surgery, Smt. Kashibai Navale Medical College and General Hospital, Pune, and all patients who took part in the study.

Funding: None. This study received no specific grant from any funding agency.

Conflict of interest: The author declares no conflict of interest.

Author contribution: Dr. Rajesh Bhivsen Mali designed the study, collected and analysed the data, wrote the manuscript and approved the final version.

Data availability: The data supporting the findings of this study are available from the corresponding author on reasonable request.

1. Bosanquet DC, Ansell J, Abdelrahman T, Cornish J, Harries R, Stimpson A, et al. Systematic Review and Meta-Regression of Factors Affecting Midline Incisional Hernia Rates: Analysis of 14,618 Patients. PLoS One. 2015;10(9):e0138745. PMID: 26389785. doi: 10.1371/journal.pone.0138745 2. Fink C, Baumann P, Wente MN, Knebel P, Bruckner T, Ulrich A, et al. Incisional hernia rate 3 years after midline laparotomy. Br J Surg. 2014;101(2):51-4. PMID: 24281948. doi: 10.1002/bjs.9364 3. Bucknall TE, Cox PJ, Ellis H. Burst abdomen and incisional hernia: a prospective study of 1129 major laparotomies. Br Med J (Clin Res Ed). 1982;284(6320):931-3. PMID: 6279229. doi: 10.1136/bmj.284.6320.931 4. Mudge M, Hughes LE. Incisional hernia: a 10 year prospective study of incidence and attitudes. Br J Surg. 1985;72(1):70-1. PMID: 3155634. doi: 10.1002/bjs.1800720127 5. van Ramshorst GH, Eker HH, Hop WC, Jeekel J, Lange JF. Impact of incisional hernia on health-related quality of life and body image: a prospective cohort study. Am J Surg. 2012;204(2):144-50. PMID: 22579232. doi: 10.1016/j.amjsurg.2012.01.012 6. Flum DR, Horvath K, Koepsell T. Have outcomes of incisional hernia repair improved with time? A population-based analysis. Ann Surg. 2003;237(1):129-35. PMID: 12496540. doi: 10.1097/00000658-200301000-00018 7. Burger JW, Luijendijk RW, Hop WC, Halm JA, Verdaasdonk EG, Jeekel J. Long-term follow-up of a randomized controlled trial of suture versus mesh repair of incisional hernia. Ann Surg. 2004;240(4):578-83; discussion 583-5. PMID: 15383785. doi: 10.1097/01.sla.0000141193.08524.e7 8. Kingsnorth A. The management of incisional hernia. Ann R Coll Surg Engl. 2006;88(3):252-60. PMID: 16719992. doi: 10.1308/003588406X106324 9. Hoer J, Lawong G, Klinge U, Schumpelick V. [Factors influencing the development of incisional hernia. A retrospective study of 2,983 laparotomy patients over a period of 10 years]. Chirurg. 2002;73(5):474-80. PMID: 12089832. doi: 10.1007/s00104-002-0425-5 10. Sorensen LT, Hemmingsen UB, Kirkeby LT, Kallehave F, Jorgensen LN. Smoking is a risk factor for incisional hernia. Arch Surg. 2005;140(2):119-23. PMID: 15723991. doi: 10.1001/archsurg.140.2.119 11. Goodenough CJ, Ko TC, Kao LS, Nguyen MT, Holihan JL, Alawadi Z, et al. Development and validation of a risk stratification score for ventral incisional hernia after abdominal surgery: hernia expectation rates in intra-abdominal surgery (the HERNIA Project). J Am Coll Surg. 2015;220(4):405-13. PMID: 25690673. doi: 10.1016/j.jamcollsurg.2014.12.027 12. Caglia P, Tracia A, Borzi L, Amodeo L, Tracia L, Veroux M, et al. Incisional hernia in the elderly: risk factors and clinical considerations. Int J Surg. 2014;12 Suppl 2:S164-S169. PMID: 25157994. doi: 10.1016/j.ijsu.2014.08.357 13. Le Huu Nho R, Mege D, Ouaissi M, Sielezneff I, Sastre B. Incidence and prevention of ventral incisional hernia. J Visc Surg. 2012;149(5 Suppl):e3-14. PMID: 23142402. doi: 10.1016/j.jviscsurg.2012.05.004 14. Halm JA, Lip H, Schmitz PI, Jeekel J. Incisional hernia after upper abdominal surgery: a randomised controlled trial of midline versus transverse incision. Hernia. 2009;13(3):275-80. PMID: 19259615. doi: 10.1007/s10029-008-0469-7 15. Muysoms FE, Antoniou SA, Bury K, Campanelli G, Conze J, Cuccurullo D, et al. European Hernia Society guidelines on the closure of abdominal wall incisions. Hernia. 2015;19(1):1-24. PMID: 25618025. doi: 10.1007/s10029-014-1342-5 16. Itatsu K, Yokoyama Y, Sugawara G, Kubota H, Tojima Y, Kurumiya Y, et al. Incidence of and risk factors for incisional hernia after abdominal surgery. Br J Surg. 2014;101(11):1439-47. PMID: 25123379. doi: 10.1002/bjs.9600 17. Veljkovic R, Protic M, Gluhovic A, Potic Z, Milosevic Z, Stojadinovic A. Prospective clinical trial of factors predicting the early development of incisional hernia after midline laparotomy. J Am Coll Surg. 2010;210(2):210-9. PMID: 20113942. doi: 10.1016/j.jamcollsurg.2009.10.013 18. Baucom RB, Ousley J, Beveridge GB, Phillips SE, Pierce RA, Holzman MD, et al. Cancer Survivorship: Defining the Incidence of Incisional Hernia After Resection for Intra-Abdominal Malignancy. Ann Surg Oncol. 2016;23(Suppl 5):764-771. PMID: 27743227. doi: 10.1245/s10434-016-5546-z 19. Israelsson LA, Millbourn D. Prevention of incisional hernias: how to close a midline incision. Surg Clin North Am. 2013;93(5):1027-40. PMID: 24035074. doi: 10.1016/j.suc.2013.06.009 20. Muysoms FE, Miserez M, Berrevoet F, Campanelli G, Champault GG, Chelala E, et al. Classification of primary and incisional abdominal wall hernias. Hernia. 2009;13(4):407-14. PMID: 19495920. doi: 10.1007/s10029-009-0518-x 21. Mangram AJ, Horan TC, Pearson ML, Silver LC, Jarvis WR. Guideline for prevention of surgical site infection, 1999. Hospital Infection Control Practices Advisory Committee. Infect Control Hosp Epidemiol. 1999;20(4):250-78; quiz 279-80. PMID: 10219875. doi: 10.1086/501620 22. van Ramshorst GH, Nieuwenhuizen J, Hop WC, Arends P, Boom J, Jeekel J, et al. Abdominal wound dehiscence in adults: development and validation of a risk model. World J Surg. 2010;34(1):20-7. PMID: 19898894. doi: 10.1007/s00268-009-0277-y 23. Beck WC, Holzman MD, Sharp KW, Nealon WH, Dupont WD, Poulose BK. Comparative effectiveness of dynamic abdominal sonography for hernia vs computed tomography in the diagnosis of incisional hernia. J Am Coll Surg. 2013;216(3):447-53; quiz 510-1. PMID: 23357727. doi: 10.1016/j.jamcollsurg.2012.11.012 24. Makela JT, Kiviniemi H, Juvonen T, Laitinen S. Factors influencing wound dehiscence after midline laparotomy. Am J Surg. 1995;170(4):387-90. PMID: 7573734. doi: 10.1016/s0002-9610(99)80309-2 25. van 't Riet M, Steyerberg EW, Nellensteyn J, Bonjer HJ, Jeekel J. Meta-analysis of techniques for closure of midline abdominal incisions. Br J Surg. 2002;89(11):1350-6. PMID: 12390373. doi: 10.1046/j.1365-2168.2002.02258.x 26. Diener MK, Voss S, Jensen K, Buchler MW, Seiler CM. Elective midline laparotomy closure: the INLINE systematic review and meta-analysis. Ann Surg. 2010;251(5):843-56. PMID: 20395846. doi: 10.1097/SLA.0b013e3181d973e4 27. Seiler CM, Bruckner T, Diener MK, Papyan A, Golcher H, Seidlmayer C, et al. Interrupted or continuous slowly absorbable sutures for closure of primary elective midline abdominal incisions: a multicenter randomized trial (INSECT: ISRCTN24023541). Ann Surg. 2009;249(4):576-82. PMID: 19300233. doi: 10.1097/SLA.0b013e31819ec6c8 28. Millbourn D, Cengiz Y, Israelsson LA. Effect of stitch length on wound complications after closure of midline incisions: a randomized controlled trial. Arch Surg. 2009;144(11):1056-9. PMID: 19917943. doi: 10.1001/archsurg.2009.189 29. Deerenberg EB, Harlaar JJ, Steyerberg EW, Lont HE, van Doorn HC, Heisterkamp J, et al. Small bites versus large bites for closure of abdominal midline incisions (STITCH): a double-blind, multicentre, randomised controlled trial. Lancet. 2015;386(10000):1254-1260. PMID: 26188742. doi: 10.1016/S0140-6736(15)60459-7 30. Millbourn D, Cengiz Y, Israelsson LA. Risk factors for wound complications in midline abdominal incisions related to the size of stitches. Hernia. 2011;15(3):261-6. PMID: 21279664. doi: 10.1007/s10029-010-0775-8.