Characteristics and outcomes of postoperative peritonitis following gastrointestinal surgery

¹Ha Dong Hospital, Hanoi, Vietnam, ²Department of Surgery, Hanoi Medical University, Hanoi, Vietnam+Hanoi Medical University Hospital, Hanoi Medical University, Hanoi, Vietnam+Vinmec Times City International General Hospital, Hanoi, Vietnam, ³Department of Anatomy, Hanoi Medical University, Hanoi, Vietnam, ⁴Department of Forensic Medicine, Hanoi Medical University, Hanoi, Vietnam, ⁵National Children's Hospital, Hanoi, Vietnam, ⁶Bach Mai Hospital, Hanoi, Vietnam, ⁷National Otorhinolaryngology Hospital, Hanoi, Vietnam, ⁸Hanoi Children's Hospital, Hanoi, Vietnam, ⁹School of Preventive Medicine and Public Health, Hanoi Medical University, Hanoi, Vietnam

^&Corresponding author
Trinh Quoc Dat, Department of Surgery, Hanoi Medical University, Hanoi, Vietnam+Hanoi Medical University Hospital, Hanoi Medical University, Hanoi, Vietnam

Introduction    

Postoperative peritonitis (POP) is one of the most severe complications following abdominal surgery, particularly in gastrointestinal procedures. It is associated with high morbidity and mortality rates, prolonged hospital stay, and significant healthcare costs [1,2]. POP represents a complex and dynamic condition, often resulting from anastomotic leakage, bowel perforation, or intra-abdominal abscess formation [3]. Despite advances in surgical techniques and perioperative care, its management remains challenging, especially due to the variability in clinical presentation and the need for timely diagnosis and intervention [4].

The clinical features of postoperative peritonitis are often nonspecific and can be masked by postoperative physiological changes, making early recognition difficult [5]. Patients may present with fever, abdominal pain, leukocytosis, or signs of sepsis, but these are not always prominent or may be attributed to normal postoperative recovery [6]. Therefore, careful clinical assessment and close monitoring of patients who have undergone gastrointestinal surgery are essential for early detection. Studies have emphasised the importance of a high index of suspicion, particularly in high-risk patients or those with persistent postoperative deterioration [7,8].

Management strategies for POP typically involve a combination of antimicrobial therapy, hemodynamic support, and surgical or percutaneous source control [1,9]. Timeliness of intervention is crucial, as delays are linked to increased mortality [10]. Source control may require relaparotomy or image-guided drainage, depending on the severity and origin of the infection [11]. Outcome predictors include patient age, comorbidities, the severity of sepsis, and adequacy of source control [3,4,11].

Given these complexities, this study aims to describe the clinical and paraclinical characteristics as well as early treatment outcomes of patients with postoperative peritonitis following gastrointestinal surgery. By systematically analysing local data, the research intends to contribute to improved clinical awareness and inform strategies for early diagnosis and effective management.

Methods     

Study design: this study was conducted as a retrospective observational descriptive study with a subgroup description of patients with localised and generalised postoperative peritonitis following gastrointestinal surgery. The study aimed to characterise clinical features, diagnostic findings, treatment approaches, and short-term outcomes without performing inferential comparisons between subgroups.

Setting: the study was carried out at Hanoi Medical University Hospital, a tertiary referral and academic surgical centre in Hanoi, Vietnam, providing advanced gastrointestinal and critical care services. Patients treated between January 2021 and August 2022 were eligible for inclusion.

Participants: the study population comprised patients diagnosed with postoperative peritonitis occurring after gastrointestinal surgery and managed at Hanoi Medical University Hospital between January 2021 and August 2022. Patients were included if they had a confirmed diagnosis of postoperative peritonitis, received treatment at the hospital through medical, interventional, or surgical approaches, and had complete clinical and paraclinical data available.

Diagnostic criteria: postoperative peritonitis was diagnosed based on a combination of clinical manifestations, laboratory abnormalities, imaging findings, and intraoperative confirmation when applicable. Diagnostic criteria included at least one of the following clinical findings after gastrointestinal surgery: abdominal pain, fever, tachycardia, abdominal distension, abdominal wall reaction, peritoneal irritation, or signs of sepsis, together with supportive laboratory or imaging evidence such as leukocytosis, intra-abdominal abscess, free intraperitoneal fluid, or anastomotic leakage detected on ultrasound or computed tomography. Localised postoperative peritonitis was defined as a confined intra-abdominal infectious process limited to a specific anatomical region, typically characterised by localised abscess formation or localised fluid collection without diffuse peritoneal contamination or generalised peritoneal signs. Generalised postoperative peritonitis was defined as diffuse peritoneal inflammation involving multiple abdominal compartments, accompanied by generalised abdominal signs, diffuse free fluid, widespread contamination, systemic inflammatory response, or intraoperative evidence of diffuse peritoneal infection.

Variables: data were collected across epidemiological, clinical, paraclinical, treatment, and outcome domains. Epidemiological variables included age, comorbidities (e.g., diabetes mellitus), and prior surgical history involving the hepatobiliary tract, stomach, small intestine, or colorectal region. Clinical variables at diagnosis comprised fever, hemodynamic instability (hypotension, tachycardia), abdominal pain, nausea or vomiting, bowel dysfunction (constipation or obstipation), abdominal distension, peritoneal signs (guarding, rebound tenderness), and Douglas pouch tenderness. Paraclinical variables included white blood cell count, abdominal ultrasound findings (intra-abdominal abscess or free fluid), and computed tomography findings, particularly intra-abdominal collections and anastomotic leakage. Treatment variables recorded the management modality (medical therapy, image-guided percutaneous drainage, or surgery), and outcome variables included early postoperative complications and length of hospital stay.

Data sources/measurement: data were extracted retrospectively from archived hospital medical records using a structured data collection form developed for the study. Clinical and laboratory parameters were obtained from physician notes, operative reports, imaging reports, and laboratory databases. Imaging findings were based on official radiology interpretations, and treatment modalities were classified according to documented management decisions. All extracted data were cross-checked for completeness and consistency before entry into the study dataset.

Bias: potential selection bias was minimised by including all eligible patients with postoperative peritonitis during the defined study period. Information bias was reduced through use of predefined diagnostic criteria and standardised data extraction procedures. However, the retrospective design may have introduced misclassification or incomplete documentation bias, which was addressed by excluding records with missing essential variables.

Study size: the study size was determined by the total number of patients meeting inclusion criteria and having complete medical records during the study period. All eligible cases identified in the hospital archive between January 2021 and August 2022 were included in the analysis. The study included 33 patients diagnosed with postoperative peritonitis.

Quantitative variables: the primary outcome of the study was the description of early treatment outcomes according to treatment modality, including medical treatment, image-guided intervention, and surgical management. Secondary outcomes included clinical presentation, laboratory and imaging findings, treatment distribution according to disease severity, early postoperative complications, mortality, and length of hospital stay.

Statistical methods: data were entered and analysed using SPSS version 25.0 (IBM Corp., Armonk, NY, USA). Descriptive statistics were used to summarise demographic characteristics, clinical findings, imaging results, treatment methods, and outcomes. Continuous variables were presented as mean ± standard deviation, while categorical variables were expressed as frequencies and percentages. Comparisons between localised and generalised postoperative peritonitis groups were performed using the Chi-square test or Fisher's exact test, as appropriate, for categorical variables. Due to the small sample size, results of subgroup analyses were interpreted cautiously and considered exploratory in nature. A p-value <0.05 was considered statistically significant.

Ethical consideration statement: the study protocol was reviewed and approved by the Ethics Committee of Hanoi Medical University. Due to the retrospective design and use of existing medical records, the requirement for informed consent was waived. All patient data were anonymised before analysis and handled with strict confidentiality in accordance with institutional regulations and the principles of the Declaration of Helsinki.

Results     

Demographic characteristics: the study included 33 patients diagnosed with postoperative peritonitis, of whom 24 (72.7%) had localised peritonitis and 9 (27.3%) had generalised peritonitis. Table 1 shows that the mean age of patients with postoperative peritonitis was 51.74 ± 15.3 years, with 60.7% aged 50 years or older. The ?60 age group was most common in both localised (29.2%) and generalised (55.6%) peritonitis. No statistically significant difference in age distribution was observed between the two groups (p=0.832).

Clinical characteristics: Table 2 shows that the most common general symptom was fever, occurring in 39.4% of cases, followed by tachycardia (24.3%), while no patients exhibited hypotension. Abdominal pain was the predominant subjective symptom, present in 78.8% of all patients, with similar rates in both localised (79.2%) and generalised (77.8%) peritonitis. Nausea or vomiting and constipation/obstipation were less frequently reported, observed in only 9.1% and 3.0% of cases, respectively. Regarding physical signs, abdominal wall reaction and abdominal distension were more frequently observed in the generalised group. Tachycardia and abdominal wall reaction were significantly more common in generalised postoperative peritonitis than in localised cases (p=0.020 and p=0.028, respectively). Notably, all patients had undocumented findings for Douglas pouch tenderness, suggesting this clinical feature was not assessed or recorded in the study population.

Main outcomes: among the 33 patients with postoperative peritonitis, elevated white blood cell count was observed in 57.6% of cases, with similar rates between the localised (58.3%) and generalised (55.6%) groups (p=0.886). Ultrasound was indicated in 45.5% of patients, more commonly in the localised group, where abscess images were found in 27.3% compared to none in the generalised group. Free fluid on ultrasound appeared in 21.2% of cases overall. Computed tomography (CT) was more frequently performed, indicated in 75.8% of patients, including all generalised cases. CT findings included abscesses in 39.4% of localised cases only, free fluid in 36.4% of patients, predominantly in the generalised group, and anastomotic leaks in 15.2% of patients, also more frequent in generalised peritonitis. CT findings demonstrated statistically significant differences between groups regarding abscess images (p<0.01), free fluid images (p<0.01), and anastomotic leakage (p=0.013) (Table 3). Among the 33 patients with postoperative peritonitis, treatment strategies differed according to disease extent. In the localised group (n=24), the majority were managed non-surgically: 41.7% received medical treatment alone, and 54.2% underwent image-guided percutaneous drainage, accounting together for 69.7% of all patients. Only one patient (4.2%) with localised peritonitis required surgery. In contrast, all patients (100%) in the generalised peritonitis group (n=9) were treated surgically, representing 27.3% of the total cohort. The distribution of treatment methods differed significantly between localised and generalised postoperative peritonitis (p<0.01) (Table 4). Hospital stay duration varied according to treatment method. Patients who received only medical treatment (n=10) had the shortest stays, with 90% discharged within 3-5 days and only one patient staying longer than 7 days. Among those who underwent image-guided percutaneous drainage (n=13), the majority (53.8%) stayed 5-7 days, while 23.1% stayed for more than 7 days. Surgical patients (n=10) had the longest hospitalisations, with half staying 5-7 days and the other half over 7 days. Length of hospital stay differed significantly according to treatment modality (p<0.01). No cases of early postoperative complications or mortality were recorded in any treatment group (Table 5).

Discussion     

This study described the clinical and paraclinical characteristics, treatment approaches, and early outcomes of 33 patients with postoperative peritonitis (POP) following gastrointestinal surgery. Most patients were over 50 years old and had comorbidities such as diabetes mellitus. Localized POP was more commonly managed with conservative or minimally invasive approaches, whereas generalised POP was treated surgically. No early postoperative complications or mortality were documented during hospitalisation.

Our findings are generally consistent with previous literature showing that POP frequently occurs in older adults after gastrointestinal surgery. The mean age in our study (51.74 ± 15.3 years) was similar to that reported by Benlamkaddem et al., who observed a mean age of 53.3 years among POP patients [11]. Older age and comorbid conditions such as diabetes are recognised factors associated with impaired healing, increased susceptibility to infection, and higher risk of anastomotic complications. Similar to our findings, Bensignor et al. also identified hepatobiliary and colorectal procedures as common preceding surgeries in POP patients [12]. These observations support the need for close postoperative surveillance in patients with high-risk surgical and clinical profiles.

Clinically, abdominal pain was the most frequent symptom in our cohort, occurring in 78.8% of patients, while fever and tachycardia were observed less frequently. The prevalence of fever in our study (39.4%) was lower than that reported in other studies, including the series by Benlamkaddem et al., in which fever was observed in approximately 78% of cases [11]. This difference may partly reflect postoperative use of analgesics, antipyretics, and antibiotics, which can attenuate inflammatory manifestations and make early diagnosis more difficult. In our study, tachycardia and abdominal wall reaction were more commonly observed in generalized POP, findings that are compatible with previous reports describing more prominent systemic and peritoneal manifestations in diffuse intra-abdominal infection [13,14]. Nevertheless, the relatively nonspecific clinical presentation observed in this cohort highlights the diagnostic challenge of POP in the postoperative setting.

Paraclinical assessment, particularly CT imaging, played an important role in the evaluation of suspected POP. CT findings such as intra-abdominal abscesses, free fluid, and anastomotic leakage were frequently identified, especially among patients with generalised peritonitis. These findings are consistent with previous studies emphasising the utility of CT imaging in detecting postoperative intra-abdominal infection and guiding management decisions [14,15]. However, our study did not formally evaluate diagnostic performance metrics such as sensitivity, specificity, or accuracy; therefore, the role of CT should be interpreted as supportive rather than definitively diagnostic based on the present data. Ultrasound was used less frequently and appeared to identify fewer abnormalities, although no direct comparison of imaging performance was conducted.

Treatment patterns in this study reflected the extent of peritoneal involvement. Most patients with localised POP were managed conservatively or with image-guided percutaneous drainage, whereas all generalised cases underwent surgery. This management approach is broadly consistent with current recommendations emphasising source control according to disease severity [4,12,15]. However, given the descriptive nature of the study and limited sample size, these findings should not be interpreted as evidence of comparative treatment effectiveness. Instead, they provide insight into real-world management practices at a tertiary referral centre.

The absence of early postoperative complications and mortality in this cohort differs markedly from previous studies reporting mortality rates ranging from 14% to 60% in POP patients [4,12]. Several factors may explain this discrepancy. First, the present study included a relatively high proportion of localised POP cases, which generally have a more favourable prognosis than diffuse peritonitis. Second, patients may have benefited from timely imaging assessment, early therapeutic intervention, and multidisciplinary perioperative management at a tertiary academic centre. Third, severely unstable patients or patients transferred to other institutions may not have been fully represented in this retrospective hospital-based cohort. In addition, the relatively small sample size increases the possibility that adverse outcomes were underestimated due to random variation. Therefore, the absence of mortality and early complications should be interpreted cautiously and should not be generalised beyond the study setting.

The findings of this study suggest that careful postoperative monitoring, combined with appropriate imaging evaluation and individualised source-control strategies, may contribute to favourable short-term outcomes in selected POP patients. Nevertheless, because of the retrospective descriptive design, causal relationships and treatment superiority cannot be established. The study primarily provides descriptive clinical data that may support future hypothesis-generating research and contribute to local institutional experience in POP management.

This study has several important limitations. First, the small sample size and single-centre design substantially limit the generalizability of the findings and reduce the robustness of subgroup analyses. Second, the retrospective nature of the study may have introduced documentation bias and incomplete clinical recording, particularly regarding subjective symptoms and physical examination findings. Third, only short-term in-hospital outcomes were evaluated, and no long-term follow-up data regarding recurrence, reoperation, or delayed mortality were available. Fourth, the study did not include microbiological findings, antimicrobial resistance patterns, or severity scoring systems such as APACHE II or Mannheim Peritonitis Index, which may have provided additional prognostic information and improved characterisation of disease severity. Future multicenter prospective studies with larger sample sizes, standardised severity assessment, microbiological profiling, and extended follow-up are needed to better clarify prognostic factors and long-term outcomes in postoperative peritonitis.

Conclusion     

Postoperative peritonitis remains a serious postoperative complication, particularly among older adults with comorbidities and prior gastrointestinal surgery. Clinical manifestations may be nonspecific, and CT imaging may assist in identifying important intra-abdominal abnormalities associated with POP. In this cohort, localised cases were more commonly managed conservatively or with image-guided drainage, whereas generalised peritonitis required surgical intervention. Although no early postoperative complications or mortality were observed, these findings should be interpreted cautiously because of the small sample size and retrospective study design. Further prospective multicenter studies are required to validate these observations and better define optimal management strategies for POP.

Competing interests     

The authors declare no competing interests.

Authors' contributions     

Nguyen Thanh Vinh: Study conception, data collection, and manuscript drafting. Trinh Quoc Dat: Principal investigator, surgical oversight, and critical revision of the manuscript. Pham Duc Huan: Surgical expertise contribution and clinical data validation. Tran Bao Long: Case identification and data collection. Nguyen Duc Anh: Imaging data interpretation and verification. Tran Quoc Hoa: Anatomical and surgical analysis support. Nguyen Thi Thu Vinh: Clinical record extraction and data verification. Nguyen Tuan Anh: Statistical analysis and data processing. Dinh Anh Duc: Methodological consultation and interpretation of findings. Phung Tuan Anh: Clinical coordination and case screening. Mai Y Tho: Clinical documentation review and manuscript editing. Nguyen Hoai Nam: Clinical supervision and data validation. Nguyen Hoang Thanh: Methodological supervision and final manuscript review. All authors read and approved the final manuscript.

Acknowledgments     

The authors sincerely thank the leadership and surgical staff of Hanoi Medical University Hospital for their support in accessing medical records and facilitating data collection. We also acknowledge the contributions of clinicians and nurses involved in the diagnosis and management of postoperative peritonitis cases included in this study.

Tables     

Table 1: age distribution in patients with postoperative peritonitis

Table 2: clinical symptoms and signs in postoperative peritonitis patients

Table 3: laboratory and imaging findings in postoperative peritonitis patients

Table 4: treatment methods in postoperative peritonitis patients

Table 5: length of hospital stay by treatment type

References