Association between intraoperative irrigation volume and postoperative abdominal abscess in perforated peptic ulcer

Abstract

Background

Perforated peptic ulcer is a critical emergency disease requiring surgery, and postoperative intra-abdominal abscess (IAA), an organ/space surgical site infection (SSI), is a common complication. Intraoperative irrigation is a common IAA prevention approach; however, scientific evidence supporting its effectiveness is lacking. We aimed to investigate the association between intraoperative irrigation volume and IAA using multicentre data.

Methods

This multicentre retrospective cohort study was conducted between January 2011 and December 2023. The study included patients aged ≥ 18 years who underwent laparotomy or laparoscopy for perforated peptic ulcer, defined as perforation of a gastric or duodenal ulcer. The primary and secondary outcomes were IAA incidence and superficial incisional SSI, respectively, and their association with the intraoperative irrigation volume was determined through multivariable logistic regression analyses.

Results

The study included 478 patients with a median age of 66 years (interquartile range [IQR]: 54–75 years), 344 (72.0%) of whom were males. The median irrigation volume was 7.0 (IQR: 5–10) L. Among the 478 patients, IAA and superficial incisional SSI occurred in 52 (10.9%) and 71 (14.9%), respectively. The irrigation volume and the outcomes exhibited no significant association (for IAA: adjusted odds ratio [AOR] = 1.04, 95% confidence interval [CI] = 0.97–1.11, p = 0.25; for superficial incisional SSI: AOR = 1.07, 95% CI = 1.00–1.14, p = 0.053).

Conclusions

There was no statistically significant association between increased intraoperative irrigation volume and a decreased incidence of postoperative IAA formation. These findings suggest that alternative strategies, rather than uncontrolled high-volume irrigation, are required for IAA prevention.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12893-026-03813-3.

Background

The prevalence of peptic ulcer disease has decreased recently [1], whereas the incidence of its common complication, perforated peptic ulcer [2, 3], has remained relatively stable [4, 5]. Perforated peptic ulcer has been associated with approximately 40% of all ulcer-related deaths, and it is an emergency that requires surgery [6, 7]. Intra-abdominal abscess (IAA), an organ/space surgical site infection (SSI), is a common postoperative complication that occurs in approximately 4.5% of cases [8]. In the field of emergency abdominal surgery for cases such as perforated peptic ulcers, intraoperative peritoneal lavage has long been performed to reduce IAA, based on the concept that dilution alleviates pollution [8]. Peritoneal lavage is common in surgical interventions; however, its volume and type vary among surgeons [9].

Despite being common, the use of peritoneal lavage to reduce IAA is controversial owing to the limited evidence regarding its use in emergency abdominal surgeries [9, 10]. Several studies have reported that peritoneal irrigation may not prevent abscess formation [11, 12]. Moreover, the intraoperative irrigation volume, which is determined by the surgeon, may be associated with an increased incidence of postoperative intraperitoneal infections in appendicitis [13].

The effectiveness of irrigation during surgery for perforated peptic ulcers remains unclear [4]. Therefore, we aimed to examine the association between irrigation volume and abscess formation during surgery for perforated peptic ulcer and evaluate the effectiveness of routine intraoperative irrigation.

Methods

Study design and setting

We performed a retrospective cohort study using data from the Perforated Peptic Ulcer Analysis Project (PPAP) [14]. The PPAP was a multicentre retrospective observational study on perforated peptic ulcers in Japan conducted between January 2011 and December 2023. This study included seven centres with expertise in emergency abdominal surgery. Patients aged ≥ 18 years who were diagnosed with a perforated peptic ulcer, defined as perforation of a gastric or duodenal ulcer, were included. Patients with malignancies or iatrogenic ulcers and pregnant women were excluded from the study. The participating facilities collected data from the electronic medical records of their respective hospitals. The collected data included patients’ demographics (age, sex, time from symptom onset to hospital visit, and meals consumed within 6 h of onset). Admission physiologic and laboratory values included the presence and severity of sepsis, peritoneal irritation signs, ascites on computed tomography (CT), body temperature, systolic blood pressure, white blood cell count, C-reactive protein (CRP) levels, and the Boey score. Intraoperative details included the surgical approach (laparotomy, laparoscopy or transition from laparoscopy to laparotomy), intraoperative irrigation volume, perforation diameter, number of drains, and operation time. Postoperative outcomes included postoperative leakage, IAA, superficial incisional SSI, length of hospital stay, and 28-day survival. At each participating facility, data entry personnel entered anonymised information. Because we used anonymised data, the requirement for informed consent was waived. Institutional review board approval was obtained from the National Hospital Organization Mito Medical Center before conducting the study (Ethics Committee of Mito Medical Center; approval number: 2024—39).

Patient selection and exposure

This study included patients aged ≥ 18 years who underwent laparotomy or laparoscopy for perforated peptic ulcers. Patients who received conservative treatment were excluded. In addition, we excluded those with missing intraoperative irrigation volume data. The exposure factor was the irrigation volume during laparotomy, laparoscopy, or transition from laparoscopy to laparotomy. Data on the irrigation volume during surgery were retrieved from electronic medical records.

Primary and secondary outcomes

The primary outcome was postoperative IAA during hospitalisation or after discharge. The secondary outcome was postoperative superficial incisional SSI during hospitalisation or after discharge. The diagnosis was made comprehensively by clinicians based on CT and physical examination findings.

Covariables

We extracted items that could be considered clinically significant confounding factors from the PPAP. The covariates included age, sex, time from onset to hospital visit (within 6, 6–12, 12–24, or > 24 h), sepsis (none, sepsis, or septic shock), peritoneal irritation signs (none, limited to the upper abdomen, or generalised), ascites on CT (none, limited to the upper abdomen, or generalised), body temperature, systolic blood pressure, CRP levels, Boey score (0–3), surgical approach (laparotomy, laparoscopy, or transition from laparoscopy to laparotomy), and perforation diameter.

Statistical analysis

We recorded the characteristics of patients with perforated peptic ulcers who underwent surgery. Continuous variables are presented as median (interquartile range [IQR]), and categorical variables are presented as numbers (%). In addition, to clarify the background of intraoperative irrigation volume, we divided the patients into four equal groups according to the irrigation volume: quartile 1 (Q1) to quartile 4 (Q4). For comparisons, we used Mann–Whitney U-tests and Kruskal–Wallis tests for continuous variables, and Pearson's chi-square tests were used for categorical variables. To assess the effect of irrigation volume, we performed multivariable logistic regression analyses after adjusting for the aforementioned confounding factors. We assumed the missing mechanism as missing at random and imputed missing values using a random forest-based method [15]. The missForest algorithm was used to impute missing values through an iterative procedure in which random forest models trained on observed covariates were used to predict missing data for each variable. The adjusted odds ratios (AOR) with 95% confidence intervals (95% CI) were calculated. Additionally, we performed subgroup analyses based on the following variables: presence or absence of sepsis (none or sepsis + [sepsis or septic shock]), presence or absence of generalised peritoneal irritation signs (not generalised [none or limited to the upper] or generalised), surgical approach (laparotomy + [laparotomy or transition from laparoscopy to laparotomy] or laparoscopy), presence or absence of ascites on CT (none or ascites + [limited to the upper abdomen or generalised]), arrival time from onset of symptoms (within 24 or > 24 h), and Boey score (1–2 and 2–3). To check the potential impact of centre-level variation, we performed a sensitivity analysis in which we included the seven institutions in the regression model as categorical variables. To check for potential non-linear or threshold effects, we performed another sensitivity analysis in which we converted the exposure variable, i.e., irrigation volume, to a categorical variable at 5 L intervals and included it in the regression model. Analyses were conducted using STATA MP4 version 18 software (StataCorp, College Station, TX, USA). The random forest-based method for imputation was performed using the missForest package in the R software version 4.3.3 (R Foundation for Statistical Computing, Vienna, Austria). A two-sided p-value < 0.05 was considered significant.

Results

Baseline characteristics

We reviewed 703 patients enrolled in the PPAP [14]. A total of 225 patients were excluded because of conservative treatment or missing intraoperative irrigation volume data. Finally, 478 patients met the inclusion criteria (Fig. 1). Baseline patient characteristics are presented in Table 1. The median age of the population was 66 (IQR: 54–75) years, and 72.0% (n = 344) were men. The median irrigation volume was 7.0 (IQR: 5–10) L (Supplementary Table 1).

Fig. 1.

Participant flow chart

Table 1.

Characteristics of the 478 eligible patients

	Overall
Characteristics	n = 478	Missing, n (%)
Age, median (IQR)	66 (54–75)	1 (0.2)
Sex, n (%)		1 (0.2)
Male	344 (72.0)
Time from onset to hospital visit, n (%)		5 (1.0)
Within 6 h	204 (42.7)
6–12 h	104 (21.8)
12–24 h	60 (12.6)
> 24 h	105 (22.0)
Meals before hospital visit, n (%)		80 (16.7)
No food within 6 h of onset	320 (66.9)
Meals eaten within 6 h of onset	78 (16.3)
Sepsis, n (%)		0
None	413 (86.4)
Sepsis	31 (6.5)
Septic shock	34 (7.1)
Peritoneal irritation signs, n (%)		7 (1.5)
None	54 (11.3)
Limited to the upper abdomen	158 (33.1)
Generalised	259 (54.2)
Ascites on CT, n (%)		6 (1.3)
None	69 (14.4)
Limited to the upper abdomen	73 (15.3)
Generalised	330 (69.0)
Temperature (°C), median (IQR)	36.8 (36.3–37.3)	15(3.1)
Systolic blood pressure (mmHg), median (IQR)	132 (112–151)	7(1.4)
White blood cell (/mm3), median (IQR)	10,700 (7,100–14,870)	0
C-reactive protein, median (IQR)	1.38 (0.23–8.63)	2(0.4)
Surgical approach, n (%)		1 (0.2)
Laparotomy	377 (78.9)
Laparoscopy	80 (16.7)
Transition from laparoscopy to laparotomy	20 (4.2)
Irrigation volume (L), median (IQR)	7 (5—10)
Number of drains, median (IQR)	3 (2—3)	2(0.4)
Perforation diameter (mm), median (IQR)	9 (5—15)	29(6.0)
Operation time (min), median (IQR)	102 (76–144)	0
Boey score		0
0	267 (55.9)
1	161 (33.7)
2	44 (9.2)
3	6 (1.3)
Leakage, n (%)	29 (6.1)	0
Intra-abdominal abscess, n (%)	52 (10.9)	0
Superficial incisional surgical site infection, n (%)	71 (14.9)	0
Hospital stay (days), median (IQR)	14 (10–23)	1(0.2)
The 28-day survival, n (%)	395 (82.6)	64 (13.4)

IQR interquartile range, CT computed tomography

Association between intraoperative irrigation volume and outcomes

The clinical outcomes of the study are summarised in Table 1. IAA and superficial incisional SSI occurred in 52 (10.9%) and 71 (14.9%) of the 478 patients, respectively. A multivariable logistic regression analysis was used to examine the association between intraoperative irrigation volume and the occurrence of IAA (Fig. 2). The analysis indicated no significant association between the irrigation volume and IAA (AOR, 1.04; 95% CI, 0.97–1.11; p = 0.25). Regarding the secondary outcome, multivariable analyses revealed the impact of irrigation volume on superficial incisional SSI (Fig. 2), indicating that the irrigation volume was not significantly associated with superficial incisional SSI (AOR, 1.07; 95% CI, 1.00–1.14; p = 0.053).

Fig. 2.

Association between irrigation volume and intra-abdominal abscess incidence and superficial incisional surgical site infection. SSI, surgical site infection; AOR, adjusted odds ratio

Subgroup analysis of IAA

We performed exploratory subgroup analyses using multivariable logistic regression to assess the potential heterogeneity in the association between intraoperative irrigation volume and IAA. The subgroup analyses are presented in Fig. 3. The irrigation volume and IAA showed no significant interaction across the following subgroups: sepsis (p = 0.86), peritoneal irritation signs (p = 0.95), surgical approach (p = 0.88), ascites on CT (p = 0.87), time from onset to hospital visit (p = 0.60), and Boey score (p = 0.31).

Fig. 3.

Forest plot: Subgroup analysis of the association between irrigation volume and intra-abdominal abscess. Sepsis +, sepsis or septic shock; Laparotomy +, laparotomy or transition from laparoscopy to laparotomy; Ascites +, limited to the upper abdomen or generalised; AOR, adjusted odds ratio; CT, computed tomography

Sensitivity analysis

We performed a multivariable regression analysis adjusting for inter-institutional variation, the results of which are presented as Sensitivity Analysis (Model 1) in Supplementary Fig. 1 and showed no substantial difference from the results of the primary analysis. We also conducted a multivariable logistic regression analysis with irrigation volume categorised at 5 L intervals to evaluate potential non-linear or threshold effects; the results are presented as Sensitivity Analysis (Model 2) in Supplementary Fig. 2. Based on the results of the Sensitivity Analysis, no obvious non-linear or threshold effect was observed.

Discussion

We performed a retrospective cohort study using multicentre data and found no significant association between intraoperative irrigation volume and IAA formation. To our knowledge, this is the first large-scale multicentre study on the effect of peritoneal irrigation volume on surgical outcomes in patients undergoing surgery for perforated peptic ulcers.

In the field of emergency abdominal surgery, postoperative IAA is of clinical significance because it affects patient prognosis. It subsequently causes non-infectious surgical complications, promotes the proliferation of antimicrobial-resistant organisms, and leads to increased hospitalisation costs and mortality [16]. Surgeons usually irrigate the abdominal cavity during emergency surgery for acute abdomen (including perforated peptic ulcers) to prevent IAA formation. Since its proposal in 1905 [9], this has become a frequent approach among surgeons. There is a notion that “dilution is the solution to pollution.” However, this practice remains controversial owing to the lack of conclusive evidence. Some studies have reported the role of intraoperative irrigation during appendectomies. Irrigation with saline during laparoscopic appendectomy was not associated with a decreased IAA risk [11, 12]. Recent studies on laparoscopic appendectomy have not definitively supported the role of intraoperative irrigation in reducing abscess formation.

In perforated peptic ulcers, evidence-based support for the routine use of intraoperative peritoneal lavage is lacking [8], and the volume and type of lavage fluid used vary among surgeons [9]. A previous review article recommended irrigation with 6–10 L and up to 30 L of warm saline [17]. However, our results do not support the notion that more intraoperative irrigation is effective. Tsao et al. [18] showed that the group that received peritoneal irrigation had a higher IAA risk than did the group that received gauze wiping and suction only during laparoscopic repair. The pathophysiological mechanisms may include the spread of contaminants and the dilution of phagocytic mediators caused by peritoneal lavage, as well as a limited reduction in the microbial load owing to the adherence of microorganisms to the peritoneal membrane [19]. The results of the present and previous studies suggest that alternative preventive strategies should be considered, such as removing contaminants with gauze, followed by lavage with an appropriate volume of water before uncontrolled high-volume intraperitoneal lavage. Further evidence is required to determine the optimal intraoperative irrigation volume and approach for preventing IAA formation.

We performed subgroup analyses for several factors to assess potential heterogeneity in IAA using multivariable logistic regression. The risk of postoperative IAA formation may vary depending on a patient's preoperative and intraoperative conditions. In perforated peptic ulcers, the Boey score is associated with increased morbidity and mortality [20]. Furthermore, a study reported that patients with perforated peptic ulcers who presented within 24 h of symptom onset did not experience postoperative complications, whereas those who presented at > 48 h after symptom onset had postoperative complications [21]. However, we conducted subgroup analyses based on these patient characteristics and found no differences in the association of intraoperative irrigation volume with IAA between these subgroups. Our analysis of a cohort that is considered to be at an elevated risk for complications (such as IAA) based on the literature revealed no heterogeneity in the intraoperative irrigation volume used to prevent IAA formation. Thus, further research addressing patient heterogeneity is warranted.

In this study, we found no evidence that the volume of intraoperative irrigation was associated with the occurrence of superficial incisional SSI. Similar findings were reported in the previously mentioned study [18]. In a different surgical context, a study conducted in patients undergoing elective liver surgery reported that intraoperative peritoneal lavage did not reduce the incidence of superficial/deep SSI, and noted that peritoneal lavage may delay mesothelial cell healing and remove inflammatory mediators [22]. In patients with perforated peptic ulcer, further research is warranted to clarify the impact of intraoperative irrigation volume on superficial incisional SSI.

The strengths of our study lie in its multicentre design and access to detailed clinical information. We used data from seven high-volume emergency medical centres and included a larger sample size than those in previous studies. Detailed clinical data, including the intraoperative irrigation volume, were incorporated to evaluate their association with clinical outcomes. Additionally, detailed pre-admission and preoperative data, such as time from onset to hospital visit and ascites on CT, were collected, enabling a rigorous adjustment for potential confounding factors. Most surgeons determine the irrigation volume based on various preoperative clinical factors.

Despite its promising results, our study has some limitations. First, this was an observational study, and there may have been unmeasured confounding factors. A potential unmeasured confounder in the association between intraoperative lavage and postoperative IAA formation is the degree of intraoperative contamination, which may influence the amount of lavage performed and the subsequent incidence of abscess development. In this study, we adjusted for confounding factors by including variables, such as preoperative ascites on CT, time from onset to hospital visit, and perforation diameter; however, these adjustments may have been insufficient. In addition, because information on specific antibiotics was not available, the possibility of residual confounding cannot be excluded. Therefore, future randomised controlled trials and prospective observational studies that rigorously quantify the degree of intraoperative contamination are warranted. Second, the possibility of a Type II error cannot be excluded; however, the relatively large sample size compared with those of previous studies remains a strength. Third, we excluded cases with missing irrigation volumes, which may have introduced selection bias; however, the proportion of missing irrigation data was small and is unlikely to have substantially affected our findings. Fourth, as this study was retrospective, we could not predefine detailed diagnostic criteria for outcomes. Therefore, diagnostic decisions were made based on each surgeon’s clinical expertise, which might have resulted in misclassification. However, the surgeons at the participating institutions were highly experienced and likely made clinically appropriate diagnoses based on mostly similar criteria. Finally, this study included only Japanese patients with perforated peptic ulcers, which may limit the generalisability of the findings to other countries. Further studies are warranted to assess the generalisability of these results to broader patient populations.

Conclusions

This study demonstrated no significant association between increased intraoperative irrigation volume and a decreased incidence of postoperative IAA formation. These findings suggest that alternative strategies, rather than uncontrolled high-volume irrigation, are essential for IAA prevention. Further evidence is required to determine the optimal intraoperative irrigation volume and approach for preventing IAA formation.

Abbreviations

AOR

Adjusted odds ratios

CRP

C-reactive protein

CT

Computed tomography

IAA

Intra-abdominal abscess

PPAP

Perforated Peptic Ulcer Analysis Project

SSI

Surgical site infection

Authors’ contributions

Atsushi Tabeta: writing-original draft, formal analysis, methodology. Yusuke Tsutsumi: supervision, writing - methodology, review and editing. Hiromasa Hoshi: conceptualisation, investigation, supervision. Akira Endo: supervision, writing - review and editing. Koji Ito: investigation, supervision. Tomohiro Akutsu: investigation, supervision. Hikaru Odera: investigation, supervision. Hideto Shiraki: investigation, supervision. Kei Ito: investigation, supervision. Takeshi Yokoyama: investigation, supervision. Yasukazu Narita: investigation, supervision. Taro Masuda: investigation, supervision. Akira Suekane: investigation, supervision. Koji Morishita: supervision.

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Data availability

The data underlying this study are available from the corresponding author on reasonable request.

Declarations

Ethics approval and consent to participate

This study was conducted in accordance with the principles of the Declaration of Helsinki. This study was approved by the Ethics Committee of Mito Medical Center (approval number: 2024—39). The requirement for informed consent was waived by the board because the study was retrospective and used anonymised patient data.

Competing interests

The authors declare no competing interests.