Small bowel obstruction (SBO) is defined as a status that is a surgical emergency resulting from the inhibited passage of bowel contents [1]. SBO is a major cause of hospital admission [2]. The most common cause of SBO is adhesion, accounting for approximately 75% of all cases, followed by malignancy and inflammatory bowel disease [3]. Studies have aimed to prevent postoperative adhesion, but no appropriate method has been established [4]. Therefore, the appropriate treatment for SBO remains an important surgical issue. Most cases of SBO are successfully treated with conservative management. However, some demand opportune surgical interventions [5]. Failing to perform appropriate surgical interventions increases mortality and morbidity.

According to a study from 2013, the incidence rate of complications such as surgical site infection, pneumonia, and sepsis and mortality is significantly higher in groups of patients whose surgical treatment is delayed by > 24 hours compared to those who received early operative intervention for adhesive SBO [6].

Studies on SBO found some indications for emergency surgery. However, the analysis of specific clinical factors for delayed operation is lacking [7, 8]. Selecting operative management is difficult for patients who previously recovered through conservative care or who are at the boundary of indications for operative management. The aim of this study was to improve the therapeutic prognosis of SBO by identifying predictive factors for the early selection of patients who need operative management.

This was a single-center retrospective study conducted in the Surgery Department of our hospital from January 1, 2015, to December 31, 2016. The study protocol was reviewed and approved by the Institutional Review Board (IRB) of our hospital (approval number: SGPAIK 2018-03-024). The IRB waived the need for informed consent for this retrospective chart review.

We investigated the clinical features of patients who were diagnosed as having SBO between January 1, 2015, and December 31, 2016. During the study period, 172 patients were hospitalized for SBO. Patients with ileus within 1 month after surgery (n= 19); who underwent surgery within 3 days after admission because they met immediate surgery criteria such as ischemic change and closed loop on CT (n= 18); and patients with colon or rectal lesions (n= 27) were excluded. The 108 included patients were divided into a conservative care group (n = 96) and an operative management group (n= 12) (Fig. 1).

Baseline clinical data analysis showed no significant differences between groups on age, sex, height, history of smoking or alcohol consumption, diabetes mellitus, or hypertension. BMI (P= 0.013) (Table 1) was significantly higher in the conservative care group than the operative management group. The number of operations before index surgery was significantly higher in the operative management group than the conservative care group (P= 0.007) (Table 1).

No significant differences were found between the 2 groups in time to hospitalization for SBO after index surgery or characteristics of the index surgery such as malignancy, laparotomy, bowel resection, emergency, or intraperitoneal drainage tube (Table 2).

Initial vital signs and laboratory findings demonstrated no significant differences in systolic blood pressure, diastolic blood pressure, body temperature, heart rate, respiratory rate, hemoglobin level, or differential leukocyte count between the 2 groups. Initial leukocyte count (P= 0.004) (Table 3) and CRP level (P= 0.028) (Table 3) were significantly higher in the operative management group than the conservative care group.

The choice of surgical or conservative treatment for patients with SBO is still controversial [10]. Partial obstruction with no sign of strangulation usually necessitates conservative treatment for SBP. When complete obstruction or strangulation is confirmed, the treatment of choice is early surgery [11, 12].

This study was a retrospective analysis of clinical factors predicted to be associated with the therapeutic prognosis of SBO. We found several factors that could help identify patients who require early operative treatment.

A previous report suggested that patient age and ASA score are closely related to postoperative mortality in patients with SBO [13]. However, this factor was not statistically relevant in this study. In agreement with a 2014 study by Meier et al. [9], we found that the number and type of previous abdominal operations did not affect the therapeutic prognosis of SBO. However, Lee et al. [14] found that history of operation was associated with the occurrence of early postoperative SBO (P = 0.044). In that study, patients who underwent surgery more than 3 times were more likely to have surgery for SBO. However, no difference was observed according to surgical method. This finding was because patients who received the operation once had the operation to treat their disease and patients who received the operation more than 3 times had the operation for SBO. The most common cause of SBO is reported to be adhesion due to a previous surgery, and risk of adhesion is expected to rise as the number of operations increases [3].

In 2012, Angenete et al. [15] reported an increased incidence for SBO after open surgery compared to laparoscopic surgery. Similar to a previous study, we found that the percentage of SBO was significantly higher for open surgery than for laparoscopic surgery. Generally, colorectal surgery is the most frequent type of surgery associated with SBO, followed by gynecological surgery, herniorrhaphy, and appendectomy [16, 17]. This result seems to be related to the degree of small intestine manipulation.

BMI was significantly higher in the conservative treatment group than in the operative management group. A 2007 study by Davies on obesity and appendicitis in children compared a normal weight group with a very obese group, defined as > 2 standard deviations over the mean weight for age. The appendicitis perforation rate was 20.0% in the very obese group and 25.5% in the normal weight group [18]. This paradoxical positive effect of obesity can be explained by higher expression of anti-inflammatory cytokines and antibacterial peptides in human omental tissue [19]. According to a 1992 animal study by Adams et al. [20], omental wrap is protective and contributes to wound repair by preventing premature leakage of vulnerable anastomosis and becoming a source of granulation tissue and neovascularization. For this reason, omentum with abundant adipocytes is called an “abdominal policeman” [21]. Therefore, we hypothesized that at the time of index surgery, the adipocyte-induced anti-inflammatory response of adipocytes in patients with obesity would be effective in reducing risk of intestinal adhesion after surgery. Thus, the results of this study can be explained by the better therapeutic prognosis for SBO after index surgery for patients with obesity.

Initial leukocyte count and CRP level were significantly higher in the operative management group than in the conservative care group. In 2010, Schwenter et al. [22] suggested that clinicoradiological score predicts risk of strangulated SBO. In the study, small bowel resection was significantly more frequently required for leukocyte counts > 10⁴/μL or CRP levels exceeding 7.5 mg/dL. The results of these studies may be due to both leukocyte counts and CRP levels being proportional to inflammation severity.

A limitation of this study is that randomization among the comparative groups was not practical because of the innate characteristics of a retrospective study. Another limitation is the lack of a plan to set a cutoff value for each predictive factor that was found to be significant. In addition, the lack of a study of initial CT findings remains a limitation. Further studies are needed to overcome these limitations and establish more sophisticated SBO management guidelines.

In conclusion, we found that the number of operations before SBO, leukocyte count, CRP level, and BMI were statistically significant factors in patients with SBO treated surgically. By closely examining these factors, we inferred that early selection of patients who need surgery may help improve their therapeutic prognosis.