Inter-ischial spine distance is a simple index of narrow pelvis that may predict difficulty during laparoscopic low anterior resection: a retrospective study

Abstract Background A narrow pelvis makes laparoscopic rectal resection difficult. This study aimed to evaluate whether a simple measurement on computed tomography can predict procedural difficulty. Methods A total of 62 patients with low rectal cancer underwent conventional laparoscopic low anterior resection. The inter-ischial spine (IS) distance (i.e., distance between the ischial spines) was measured on an axial computed tomography slice. Operative time, blood loss, and time from insertion of linear staplers to completion of clamping on the distal end of the rectum (clamp time) were compared. Results Overall, 42 men and 20 women with low rectal cancer were assessed. The mean tumor size was 34.5 mm. Total or tumor-specific mesorectal excisions were performed in all cases; high ligation and resection of the inferior mesenteric arteries were carried out in 92% of patients. The mean operative time, and blood loss were 206 min, and 15 mL respectively. Four patients (6.5%) experienced postoperative complications, including two anastomotic leaks (3.2%). The mean IS distance was 93.3 mm. With simple linear regression, shorter IS distance correlated with longer operative time (R2 = 0.08, P = 0.030) and clamp time (R2 = 0.07, P = 0.046). Using an receiver operating characteristic curve, a narrow pelvis was defined as IS distance < 94.7 mm. Multivariate regression analysis revealed that IS distance < 94.7 mm (odds ratio, 3.51; P = 0.04) was independently associated with a longer clamp time. Conclusions The IS distance is a simple and useful measurement for predicting the difficulty of laparoscopic low anterior resection.