The role of the longitudinal muscle in the anal sphincter complex

Technical, functional, and oncological validity of robot-assisted total-intersphincteric resection (T-ISR) for lower rectal cancer

BACKGROUND

Few studies fairly compared anorectal function and prognostic outcomes between patients undergoing abdominoperineal resection (APR) and anorectal-function-saving operations (ASO) under the equivalent conditions. By contrast, surgeons used to be somewhat hesitant to conduct total intersphincteric resection (T-ISR) as maximal ASO, due to its technical complexity and potential anorectal dysfunction.

METHODS

Propensity-score matched cohorts undergoing robot-assisted R0 surgery [T-ISR vs APR vs partial-subtotal ISR (PS-ISR)/lower anterior resection (LAR)] for rectal cancer (n = 1361) were included. Operative outcomes, recurrence, and disease-free/overall survival (DFS/OS) were analyzed. Anorectal function was evaluated based on fecal incontinence score and high-resolution manometry between the T-ISR and other ASO groups.

RESULTS

Few differences were detected between the T-ISR and APR groups. More patients undergoing APR had T4 stage disease, while the lowest tumor margin was the same in both groups (mean, 1.5 cm from anal verge). Prognostic outcomes did not differ between the T-ISR and APR groups, including local (5.1% vs 7.7%, p = 1) or systemic (15.4% vs 25.6%, p = 0.401) recurrence, and 5-year DFS (78.7% vs 61.5%, p = 0.1) and OS (89% vs 82.1%, p = 0.434) rates, nor were there differences between the T-ISR and PS-ISR/LAR groups. The PS-ISR group generally showed less anorectal dysfunction than the T-ISR group, but maximal tolerance volume did not differ between these two groups and was within the range for the healthy population.

CONCLUSIONS

T-ISR can replace most traditional APR, except for advanced T4 disease with aggressive infiltration into the levator-sphincters, and can provide tolerable anorectal dysfunction.

Low muscle volume of the anal sphincter complex: A novel prognostic factor in children with anorectal malformations?

BACKGROUND/PURPOSE

The anal sphincter complex (ASC) plays a key role in continence and is often dysfunctional in infants born with anorectal malformations (ARM). The ASC is well depicted by magnetic resonance (MR) imaging but volumetric reference data are lacking in infants. Thus, we tested the feasibility of MR based ASC volumetry, collected reference data, and compared them with cases of favorableprognosis and unfavorable prognosis (as defined by the type of ARM).

METHODS

We determined ASC volume on T2 weighted MR images of seventy six infants (ARM n = 33; controls n = 43) by manual segmentation. Inter operator agreement was assessed by intraclass correlation coefficient. Linear regression was used to establish weight dependent reference data. Observed to expected ASC volumes of patients with unfavorable and favorable prognosis were compared (unpaired t test).

RESULTS

ASC volumetry was feasible in all cases. Patients with ARM had low 'observed to expected' ASC volume ( 18.1%; p = 0.006). 'Observed to expected' ASC volume differed significantly between patients with favorableand unfavorable prognosis (p < 0.001).

CONCLUSION

We confirmed the feasibility of MRI based ASC volumetry and provided initial reference data for infants. Although ASC volumes were lowest in infants with ARM of unfavorable prognosis for fecal continence, the value of ASC volume as prognostic parameter remains to be determined.

Anus-Preserving Surgery in Advanced Low-Lying Rectal Cancer: A Perspective on Oncological Safety of Intersphincteric Resection

The surgical management of low-lying rectal cancer, within 5 cm from the anal verge (AV), is challenging due to the possibility, or not, to preserve the anus with its sphincter muscles maintaining oncological safety. The standardization of total mesorectal excision, the adoption of neoadjuvant chemoradiotherapy, the implementation of rectal magnetic resonance imaging, and the evolution of mechanical staplers have increased the rate of anus-preserving surgeries. Moreover, extensive anatomy and physiology studies have increased the understanding of the complexity of the deep pelvis. Intersphincteric resection (ISR) was introduced nearly three decades ago as the ultimate anus-preserving surgery. The definition and indication of ISR have changed over time. The adoption of the robotic platform provides excellent perioperative results with no differences in oncological outcomes. Pushing the boundaries of anus-preserving surgeries has risen doubts on oncological safety in order to preserve function. This review critically discusses the oncological safety of ISR by evaluating the anatomical characteristics of the deep pelvis, the clinical indications, the role of distal and circumferential resection margins, the role of the neoadjuvant chemoradiotherapy, the outcomes between surgical approaches (open, laparoscopic, and robotic), the comparison with abdominoperineal resection, the risk factors for oncological outcomes and local recurrence, the patterns of local recurrences after ISR, considerations on functional outcomes after ISR, and learning curve and surgical education on ISR.

Complete intersphincteric longitudinal muscle excision May Be key to reducing local recurrence during intersphincteric resection

BACKGROUND

Although total mesorectal excision (TME) is regarded as a standard procedure for rectal cancer, technical definition and evaluation method have not yet been investigated for intersphincteric resection (ISR). This study was performed to introduce a complete ISR procedure, and to assess whether total intersphincteric longitudinal muscle excision (TILME) facilitated the completeness of ISR and reduced recurrence.

METHODS

A total of 1080 patients with rectal adenocarcinoma who underwent robot-assisted low anterior resection (LAR) over 10 years were consecutively enrolled. Propensity-score matching of the two LAR groups (ISR vs LAR group, 1:1) and three ISR subgroups (partial vs subtotal vs total ISR subgroup, 2:2:1) was performed by strict adjustment of baseline characteristics. Archived specimens and video-/photo-records were reevaluated to examine completeness of TILME.

RESULTS

Complete-TILME was performed in 84.5% of patients who underwent ISR. Multivariate analysis showed that incomplete-TILME was the only parameter independently associated with increased 5-year cumulative local recurrence (odds ratio = 23.385; 95% confidence interval = 1.492-366.421; p = 0.03), and that incomplete-TILME was independently associated with adipose tissue surrounding the intersphincteric longitudinal muscle, coloanal anastomosis, and total ISR (p < 0.001-0.05). Although mean incontinence scores and anorectal manometry deteriorated to some degree 12-24 months after surgery in all patients, they remained acceptable. The 5-year cumulative DFS (74.1% vs 60%, p = 0.18) and OS (85.9% vs 70%, p = 0.10) rates tended to be higher in patients with complete than incomplete-TILME.

CONCLUSIONS

The completeness of TILME appears to be an independent indicator of complete ISR, reducing local recurrence following lower rectal cancer surgery.