Overview
Definition:
Transanal Total Mesorectal Excision (taTME) is a minimally invasive surgical technique for removing the rectum and its surrounding mesorectal tissue through a transanal approach, often combined with laparoscopic or robotic assistance for abdominal dissection and reconstruction
It aims to achieve complete mesorectal excision (CME) with clear circumferential resection margins, particularly for mid and low rectal cancers, while potentially reducing the need for a permanent stoma in selected patients.
Epidemiology:
Rectal cancer incidence varies globally, with significant numbers diagnosed annually
taTME is a relatively newer technique gaining traction for specific rectal cancer cases, offering an alternative to traditional open, laparoscopic, or transabdominal robotic approaches
Its adoption is growing, with ongoing studies assessing its long-term oncologic and functional outcomes compared to established methods.
Clinical Significance:
taTME represents a significant advancement in rectal cancer surgery, enabling a more oncologically sound dissection of the mesorectum from below
It offers potential benefits such as improved visualization of the distal dissection plane, reduced operative time in some series, and potentially better functional outcomes (e.g., sexual and voiding function) by preserving autonomic nerves
It is crucial for surgical residents and DNB/NEET SS candidates to understand its indications, techniques, and place in the modern management of rectal cancer.
Indications
Surgical Indications:
Primary indication is rectal adenocarcinoma located in the mid to lower rectum (typically 5-15 cm from the anal verge)
Suitable for patients requiring anterior resection or abdominoperineal resection (APR) where complete mesorectal excision is oncologically mandated
It can be considered in cases where standard laparoscopic TME is technically challenging or for patients with specific comorbidities that might benefit from avoiding a large abdominal incision.
Patient Selection:
Careful patient selection is paramount
Factors include tumor stage, location, patient anatomy (pelvic depth, obesity), and surgeon experience
Imaging (MRI rectum) is critical for assessing resectability and mesorectal invasion
Patients with extensive local invasion or distant metastases may not be suitable candidates
Multidisciplinary team discussion is essential.
Contraindications:
Absolute contraindications include unresectable tumors, severe systemic illness, and extensive inflammatory bowel disease involving the rectum
Relative contraindications may include very low rectal tumors (below the levator ani muscles where transanal access is problematic), significant perineal sepsis, or previous pelvic radiation that makes dissection extremely difficult
Active anal canal pathology might also preclude this approach.
Preoperative Preparation
Neoadjuvant Therapy:
Patients with locally advanced rectal cancer typically receive neoadjuvant chemoradiotherapy (nCRT) or chemotherapy
This aims to downstage the tumor, improve resectability, and reduce local recurrence rates
The timing of surgery after nCRT needs careful consideration, usually between 8-12 weeks post-completion.
Bowel Preparation:
Standard mechanical bowel preparation with oral laxatives (e.g., polyethylene glycol) is performed the evening before surgery to clear the bowel lumen
Prophylactic antibiotics are administered intravenously before incision to cover common colonic flora.
Anesthesia And Positioning:
General anesthesia is typically employed
Patients are usually placed in the lithotomy position for the transanal portion and modified lithotomy or dorsal supine for the laparoscopic/robotic phase
Careful padding of pressure points is crucial to prevent nerve injuries.
Instrumentation:
Specialized transanal endoscopic instruments, such as rigid or flexible endoscopic platforms, are required for the transanal dissection
Laparoscopic or robotic instruments are used for the abdominal phase, including stapling devices for bowel transection and anastomosis.
Procedure Steps
Transanal Dissection:
A rigid or flexible anoscope is inserted into the anal canal
Dissection commences at the apex of the mesorectum or at the tumor level, depending on the approach
The plane of dissection is meticulously developed along the lateral border of the mesorectum, working proximally
CO2 insufflation may be used within the rectum to improve visualization and create pneumorectum
Dissection progresses upwards, often guided by laparoscopic/robotic instruments from above, defining the plane between the mesorectum and adjacent structures (pelvic sidewall, prostate/vagina, sacrum).
Abdominal Dissection:
Once the transanal dissection has created a sufficient window, laparoscopic or robotic instruments are introduced to complete the mobilization of the mesorectum from the abdominal or pelvic cavity
This involves ligating major vessels (superior rectal artery, middle rectal artery if present) and dividing the colon proximally for resection
The specimen is delivered through the anus or a specimen retrieval bag via a port site.
Anastomosis:
After specimen extraction and confirmation of adequate proximal and distal margins, a hand-sewn or stapled anastomosis is performed
The choice depends on the level of resection, bowel quality, and surgeon preference
Low anterior resection with coloanal anastomosis is common for distal rectal cancers
A defunctioning loop ileostomy is frequently created to protect the anastomosis, especially in low anastomoses or after nCRT, and is typically reversed 6-12 weeks later.
Specimen Handling:
The intact specimen is carefully oriented and sent for pathological examination, with particular attention to the circumferential resection margin (CRM), proximal and distal margins, and lymph node status
The quality of the mesorectal excision is a critical factor in predicting local recurrence.
Postoperative Care
Pain Management:
Adequate analgesia is provided, often using patient-controlled analgesia (PCA) or epidural analgesia, especially for low anastomoses
Regular oral analgesics are continued as the patient mobilizes.
Drainage And Monitoring:
Pelvic drains may be inserted and removed when output is minimal
Vital signs are monitored closely
Fluid balance is maintained, and urine output is observed
Ileostomy output is monitored, and stoma care education is provided.
Dietary Advancement:
Patients are typically kept nil by mouth initially and advanced to clear liquids as bowel function returns, followed by a progressive diet
Early mobilization is encouraged to prevent deep vein thrombosis and pulmonary complications.
Stoma Care:
If an ileostomy is created, patients receive comprehensive education on stoma management, including skin care, pouch application, and dietary adjustments to manage output
Follow-up with a stoma nurse is crucial.
Complications
Early Complications:
Bleeding (anastomotic or surgical site)
Anastomotic leak (most serious, leading to sepsis and peritonitis)
Ileus
Urinary retention
Wound infection
Bladder or sexual dysfunction
Injury to adjacent structures (e.g., sacrum, bladder, prostate, vagina, ureters).
Late Complications:
Anastomotic stricture
Chronic pelvic pain
Incisional hernia
Sexual dysfunction
Bowel dysfunction (low anterior resection syndrome - LARS, characterized by fecal urgency, frequency, and incontinence)
Rectal prolapse.
Prevention Strategies:
Meticulous surgical technique focusing on achieving a clear mesorectal plane and adequate margins
Careful identification and preservation of autonomic nerves
Appropriate use of neoadjuvant therapy
Creation of a defunctioning stoma for low anastomoses
Close postoperative monitoring
Prompt recognition and management of anastomotic leaks.
Prognosis
Factors Affecting Prognosis:
The most critical factor is the completeness of mesorectal excision and the status of the circumferential resection margin (CRM)
Tumor stage (TNM), lymph node involvement, tumor grade, vascular invasion, and the presence of extranodal extension significantly influence outcomes
Patient factors like age and comorbidities also play a role.
Outcomes:
When performed appropriately for selected patients, taTME can achieve oncological outcomes comparable to traditional TME approaches, with low local recurrence rates and good survival
Functional outcomes, particularly concerning bowel, bladder, and sexual function, are areas of ongoing research and are believed to be potentially favorable compared to some conventional methods, especially if nerve preservation is enhanced.
Follow Up:
Postoperative follow-up involves regular clinical examinations, CEA (carcinoembryonic antigen) blood tests, and cross-sectional imaging (CT scans) to detect recurrence
Endoscopic surveillance of the anastomosis is also performed
Follow-up schedules are guided by national guidelines, typically involving monthly CEA and clinical checks for the first 1-2 years, then quarterly, then annually
Imaging frequency decreases over time.
Key Points
Exam Focus:
taTME is a transanal approach for total mesorectal excision, primarily for mid-to-low rectal cancers
It aims for CME with negative CRM
Key steps involve transanal and abdominal dissection, specimen retrieval, and anastomosis
Complications include anastomotic leak, LARS, and sexual dysfunction
CRM status is the most important prognostic factor.
Clinical Pearls:
Emphasize meticulous dissection in the correct plane to avoid iatrogenic injury and ensure oncological safety
Intraoperative imaging or tactile feedback can be helpful
Consider a defunctioning stoma for low anastomoses
Careful patient selection is crucial for success
Collaboration with experienced colorectal surgeons and radiologists is vital.
Common Mistakes:
Failure to achieve adequate CRM due to inadequate distal dissection or dissection in the wrong plane
Incomplete mesorectal mobilization
Technical difficulties with stapler placement in very low anastomoses
Delayed recognition and management of anastomotic leaks
Poor patient selection leading to suboptimal outcomes.