[Analysis on clinical factors affecting transrectal natural orifice specimen extraction in rectal cancer surgery]

Objective: To identify the factors associated with successful transrectal specimen extraction after laparoscopic rectal cancer resection. Methods: A retrospective case-control study was conducted. Clinical data of rectal cancer patients who did or did not successfully undergo transrectal specimen extraction in Shanghai East Hospital between January 2017 and December 2017 were retrieved through the rectal cancer database of Shanghai East Hospital. Case inclusion criteria: (1) tumor size ≤7 cm by pelvic MRI; (2) body mass index (BMI)≤ 30 kg/m(2); (3) no history of neoadjuvant chemoradiotherapy; (4) no anal stenosis. Clinical data including age, gender, BMI, tumor obstruction, distance from tumor to anal verge, history of abdominal operation, maximal diameter of tumor and width of mesorectum in the anteroposterior dimension measured by pelvic MRI, etc. were collected. The χ(2) test was used to perform univariate analysis. Multivariate logistic regression was used to identify factors affecting transrectal specimen extraction. Results: A total of 208 patients were included in the analysis. Of 208 patients, 132 were men and 76 were women; mean age was (63±11) years old and median tumor size was 3.8 (IQR, 3.0 to 5.0) cm. Sixty-six (31.7%) patients completed transrectal specimen extraction successfully. Univariate analysis showed that patients who completed transrectal specimen extraction were more likely to have a lower BMI (χ(2)=7.420, P=0.006), be free from malignant obstruction (χ(2)=8.972, P=0.003), have a shorter distance from tumor to the anal verge (<5.0 cm) (χ(2)=14.960, P<0.001), a smaller tumor size (≤5.0 cm) (χ(2)=18.495, P<0.001) and a thinner mesorectum in the anteroposterior dimension (≤6.0 cm) (χ(2)=34.612, P<0.001) than those who failed to perform transrectal specimen extraction. Gender, age or history of abdominal operation were not associated with the successful extraction (all P>0.05). Multivariate analysis revealed that BMI ≤25.0 kg/m(2) (OR=2.32, 95% CI: 1.06 to 5.06, P=0.034), free from malignant obstruction (OR=3.01, 95% CI: 1.82 to 6.69, P<0.001), the distance from tumor to the anal verge <5.0 cm (OR=3.73, 95% CI: 1.22 to 11.43, P=0.021), tumor size ≤ 5.0 cm (OR=4.43, 95% CI: 1.39 to 14.09, P=0.012), and the anteroposterior width of mesorectum ≤ 6.0 cm (OR=4.30, 95% CI: 2.02 to 9.18, P<0.001) were independent protective factors for successful transrectal specimen extraction. Conclusion: Preoperative assessment of BMI, malignant obstruction, distance from tumor to the anal verge, tumor size and anteroposterior width of mesorectum is beneficial to choose appropriate patients with rectal cancer to undergo transrectal specimen extraction.