Can Left Pleural Effusion Be an Indicator of Gastric Leaks after Laparoscopic Sleeve Gastrectomy?

Background: Coincidental pleural effusion has been observed by computed tomography (CT) scans in individual patients with gastric leaks after laparoscopic sleeve gastrectomy; however, the frequency of this phenomenon has not been investigated in cohort studies. Objectives: This study aimed to assess the diagnostic accuracy of left pleural effusion as an indicator of gastric leaks after laparoscopic sleeve gastrectomy. Setting: University hospital and bariatric surgery center of excellence. Methods: This single-center retrospective analysis included consecutive patients who had undergone laparoscopic sleeve gastrectomy followed by CT scans to investigate suspected gastric leaks from September 2011 to September 2018. The sensitivity, specificity, Youden’s index, and predictive values were estimated using a 2 × 2 cross-tabulation. Results: The study involved assessing the CT scans of 148 patients; 80 patients (44 men and 36 women, mean age: 34 years, mean body mass index {BMI}: 46 kg/m 2 ) had positive findings of gastric leaks after laparoscopic sleeve gastrectomy, such as contrast leak, gas leak, and peri-gastric collection (either singly or in combination). The CT findings were negative for gastric leaks in 68 patients (38 men and 30 women, mean age: 33 years, mean BMI: 45 kg/m 2 ). Pleural effusion manifested as a fluid density in the dependent portion of pleural cavity on CT. The sensitivity of left pleural effusion to predict gastric leaks after laparoscopic sleeve gastrectomy was 73.8%, and the specificity was 91.2%. The positive and negative predictive values were 90.8% and 74.7%, respectively, and the Youden’s index was 64.9%. Conclusion: Left pleural effusion exhibits good diagnostic accuracy for gastric leaks after laparoscopic sleeve gastrectomy. Notably, the specificity (91.2%) was very high.


Introduction
Obesity is a worldwide pandemic, and it has a large impact on healthcare services [1] [2]. Bariatric surgery is an effective treatment for long-term weight reduction in patients with morbid obesity [3] [4] [5]. Laparoscopic sleeve gastrectomy is currently the most common bariatric surgery [6]. However, gastric leak after laparoscopic sleeve gastrectomy is a concerning potential complication, which is challenging to diagnose and treat [7]. This complication occurs in 1% -3% of patients [8]. Pleural effusion is another potential complication of bariatric surgery, and has a reported incidence rate of 2.63% [9].
There are few reports described pleural effusion as a thoracic complication of bariatric surgery or as a coincidental finding in post sleeve gastrectomy gastric leak [9] [10] [11].
To the best of our knowledge, there is no study to assess associations between left pleural effusion and gastric leaks after laparoscopic sleeve gastrectomy.
We hypothesized that left pleural effusion could be a diagnostic factor for gastric leaks after laparoscopic sleeve gastrectomy and investigated the associations between left pleural effusion and gastric leaks in patients who had undergone laparoscopic sleeve gastrectomy.

Study Design
This retrospective study included 161 consecutive patients who underwent abdominal computed tomography (CT) examinations after laparoscopic sleeve gastrectomy for suspected gastric leaks at a bariatric surgery center of excellence from September 2011 to September 2018. Patients presented within 1 -3 weeks after undergoing surgery with variable clinical signs and symptoms of gastric leakage. Institutional review board approval was obtained for this study. The requirement for obtaining informed consent was waived due to the retrospective nature of this study and the use of anonymized patient data.

Inclusion and Exclusion Criteria
All adult patients with suspected post sleeve gastrectomy gastric leaks who underwent CT scans during the study period were included. We exclude those who underwent invasive procedures (surgery, surgical drain, percutaneous drain, or endoscopic stent or drain) prior to undergoing CT scanning for the management of post sleeve gastrectomy gastric leaks.

CT Protocol
Abdominal CT scans were performed using approximately 60 mL water-soluble findings on the CT scans were assigned to the gastric leak group, and those with negative findings were assigned to the non-leak group. All CT scans derived from patients were evaluated for left pleural effusion in the included images of the lower chest ( Figure 1).

Statistical Analysis
Chi-square and t-tests were conducted to compare the gender, age, and body mass index (BMI) of the two groups. We also examined the ability of left pleural effusion to predict gastric leaks, using CT examination. The sensitivity, specificity, Youden's Index, and predictive values were estimated using a 2 × 2 crosstabulation. Asymmetric confidence intervals were also computed. The results were interpreted to determine the extent to which the diagnosis of left pleural effusion using CT examination exhibits good diagnostic accuracy for gastric leaks after laparoscopic sleeve gastrectomy.

Results
A total of 161 patients underwent CT examination for suspected gastric leaks during the study period; of these, 13 patients were excluded because they un- There were no significant demographic differences between the two groups. A contingency table test indicated that gastric leaks were not significantly associated with gender (χ 2 = 0.002; p = 0.964). Independent sample t-tests indicated that age (t = 0.205, p = 0.804) and BMI (t = 1.04, p = 0.301) were also not significantly different between the two groups ( Table 1).    In our study cohort, we found that the sensitivity of left pleural effusion to predict gastric leaks after laparoscopic sleeve gastrectomy was 73.8%, and the specificity was 91.2%. The positive and negative predictive values were 90.8% and 74.7%, respectively, and the Youden's index was 64.9% (Table 2).

Discussion
Post sleeve gastrectomy gastric leak is challenging to diagnose due to variable clinical presentations and laboratory findings. Debate is still existing regarding timing and modality of imaging to diagnose post sleeve gastrectomy leak. Misdiagnosis and delayed management can lead patient morbidity and mortality.
Whereas early recognition and treatment lead to better patient outcome [7] [10].
To the best of our knowledge, the present study is the first to assess the diagnostic accuracy of left pleural effusion to predict gastric leaks after laparoscopic sleeve gastrectomy.
Pleural effusion has been reported to occur after abdominal surgery at an incidence of 8%; higher rates have been observed after upper abdominal procedures due to the proximity of the surgical area to the chest [12]. Postsurgical pleural effusion can be secondary to thoracic or abdominal complications, or both, e.g., esophageal perforation or peritoneal fluid collection from gastric or anastomotic leaks [13]. Other common abdominal causes of pleural effusion include subdiaphragmatic abscesses, pancreatitis, biliary tract infections, and bowel anastomotic leaks [14]. However, the pathogenesis of pleural effusions secondary to abdominal pathology is poorly understood. According to Majid et al., the proposed mechanisms include the passage of fluid through the transdiaphragmatic lymphatics or defects caused by abdominal surgery, inflammation of the vascularized muscular portion of the diaphragm, and lung atelectasis [15]. Open Journal of Radiology  The present study included some limitations. Firstly, the study was retrospective in nature, and secondly, most of the patients were referred from other centers. All our patients were stable enough to undergo CT scanning and were managed conservatively. Critically sick patients are managed surgically in our institution and were not included in our study.

Conclusion
Left pleural effusion has good diagnostic accuracy with respect to gastric leaks after laparoscopic sleeve gastrectomy, with a specificity of 91% in patients with Open Journal of Radiology suspected gastric leaks. Further prospective studies evaluating left pleural effusion as an indicator for gastric leaks based on CT scanning or chest radiography are needed to validate this result.