The Coloanal Anastomosis

The goals of restorative surgery in low rectal cancer are three-fold, ensuring high-quality clinical outcomes by addressing and minimising the risk of anastomotic leak, ensuring optimal distal oncological clearance and proactively managing the long-term functional consequences of low anterior resection syndrome (LARS). I believe in practising the principles of evidence-based medicine and shared decision-making, discussing these key facets with my patients pre-operatively. This inevitably leads to personalised decision-making for my patients with rectal cancer, based on their values and priorities, whilst taking into account their tumour and clinical characteristics and the technical aspects of performing a coloanal anastomosis. This blog post highlights my approach to risk stratification, decision making and technical approaches to the coloanal anastomosis.

Risk Stratification

The first step is to provide patient-specific risk stratification for anastomotic leak. My preference is to use the Anastomotic Failure Observed Score (AFORS), which was validated through the TaTME registry in 1594 patients. This score calculates the risk of anastomotic leak based on five pre-operative risk factors; gender, body mass index, diabetes, smoking and tumour size. The score provides a cumulative score of 0-6 which corresponds to an AL rate of 6.3 – 50%. This provides me with a guide and I use this in conjunction with other established risk factors such as neoadjuvant treatment, cardiac comorbidity etc to inform the patient of their specific risk of anastomotic leak.

Figure taken from Ann Surg. 2019 Apr;269(4):700-711


The second key aspect of risk stratification is predicting the risk of longterm bowel dysfunction or LARS. I use the validated Polars score to provide patients with an insight into their risk of LARS. The Polars score uses key predictive factors to determine the risk of LARS including age, tumour height, total versus partial mesorectal excision, stoma and preoperative radiotherapy. It is readily available on the Pelican website. Patient at high risk of LARS are enrolled into the BOREAL (Bowel Rehabilitation Programme) immediately post-operatively.

Distal Oncological Margin

With very low tumours, approximately 1-2cm from the anorectal junction, my preference is to employ a combined transanal and robotic approach. In these cases I prefer to start with a full thickness distal rectotomy transanally, this allows for a controlled distal oncological margin under vision. Following on from this, I dock my robot and perform my TME dissection aiming to join my two planes of dissection, following which I extract my specimen transanally and perform a coloanal anastomosis.

Coloanal Anastomotic Techniques

I think its important to have a range of coloanal anastomotic techniques in your armamentarium ranging from the traditional transabdominal double stapled anastomotic technique, to transanal single stapled anastomosis to hand sewn coloanal anastomosis and the delayed coloanal anastomosis. Again, I employ a very personalised approach to the anastomotic technique taking into account the risk of anastomotic leak, patient and tumour characteristics, distal oncological margin and functional consequences. From a technical perspective my choice of anastomotic technique is based on the distance of the lower border of the tumour from the anorectal junction and my ability to achieve a clear distal oncological margin. Check out my talk at the ROCS2022 symposium on coloanal anastomotic techniques to see my videos and understand my approach. You can also check out the recent ESCP Robotic Surgery webinar on ‘Anastomosis after rectal resection’ which showcases a range of anastomotic techniques.

Anastomotic techniques in low rectal have evolved significantly over the last few years. Understanding these techniques, their indications and implications is essential in delivering a high quality, cutting edge rectal cancer practice. Future technological advances coupled with an improved understanding of anastomotic leak and function will lead to improved clinical and functional outcomes for our patients with lower third rectal cancer.

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