Overview
Definition:
Low anterior resection (LAR) with total mesorectal excision (TME) is a surgical procedure to remove rectal cancer located in the mid to upper rectum
TME involves the en bloc removal of the rectum along with its surrounding mesorectal fat and lymph nodes, preserving the pelvic autonomic nerves
This technique is considered the gold standard for achieving optimal oncologic outcomes in rectal cancer surgery, aiming for clear surgical margins and reduced local recurrence rates.
Epidemiology:
Rectal cancer is a significant cause of cancer-related morbidity and mortality worldwide
Incidence varies geographically, with higher rates in Western countries
Approximately 40-50% of colorectal cancers occur in the rectum
The incidence of rectal cancer increases with age, with the majority diagnosed in individuals over 50 years old
Surgical resection remains the primary curative treatment modality for localized rectal cancer.
Clinical Significance:
LAR with TME is crucial for achieving curative intent in rectal cancer
It offers the potential for sphincter preservation, avoiding a permanent colostomy, and improving quality of life for patients
The oncologic principles of TME are vital for minimizing local recurrence, which is a major determinant of long-term survival
Understanding this procedure is paramount for surgical residents preparing for DNB and NEET SS examinations, as it is a frequently tested topic with significant implications for patient management and outcomes.
Indications
Surgical Indications:
Primary indication is resectable rectal adenocarcinoma located in the mid to upper rectum, typically more than 5 cm from the anal verge
Other indications include certain types of rectal polyps that are unresectable by colonoscopy, rectal adenomas with high-grade dysplasia, and selected rectal sarcomas or lymphomas
Absolute contraindications are rare and usually relate to unresectable disease or severe comorbidities.
Pre Operative Assessment:
Comprehensive pre-operative assessment includes detailed history, physical examination (including digital rectal examination), colonoscopy with biopsy, and staging investigations such as CT abdomen/pelvis and MRI pelvis
Endorectal ultrasound (EUS) may be used for local staging
Chest X-ray or CT thorax is performed to rule out distant metastases
Assessment of cardiopulmonary function, renal function, and nutritional status is essential
Multidisciplinary team (MDT) discussion is vital for treatment planning, especially for locally advanced disease.
Neoadjuvant Therapy:
Neoadjuvant chemoradiotherapy (nCRT) is recommended for most patients with T3 or T4 rectal tumors or those with involved lymph nodes (N+)
This aims to downstage the tumor, increase the rate of complete mesorectal excision, improve local control, and potentially increase sphincter preservation rates
The standard regimen involves concurrent fluoropyrimidine-based chemotherapy with pelvic radiation (45-50.4 Gy in 25-28 fractions)
Interval rest period of 6-10 weeks between nCRT and surgery is typically recommended.
Procedure Steps
Surgical Approach:
LAR with TME is most commonly performed using an open approach (laparotomy) or a minimally invasive approach (laparoscopic or robotic surgery)
Laparoscopic and robotic TME offer potential benefits such as reduced postoperative pain, shorter hospital stay, and faster recovery, with oncologic outcomes comparable to open surgery when performed by experienced surgeons.
Dissection Technique:
The core of TME is the meticulous dissection of the rectum within the mesorectal fascia
The dissection plane is developed anteriorly from the rectovesical pouch (in males) or rectovaginal septum (in females), laterally along the pelvic sidewall, and posteriorly along the sacrum and presacral fascia
Careful identification and preservation of the autonomic nerves (hypogastric plexus and pelvic splanchnic nerves) are crucial for preserving sexual and urinary function.
Anastomosis Technique:
Following resection of the diseased rectum, a tension-free colorectal or coloanal anastomosis is created
This can be achieved manually or using a circular stapling device
The choice of anastomosis technique depends on the level of resection, surgeon preference, and intraoperative findings
In very low rectal resections, a coloanal anastomosis with an upang colonic pouch (J-pouch) may be created to improve functional outcomes
Diverting stoma (ileostomy or colostomy) is often fashioned to protect the anastomosis and reduce the risk of anastomotic leak.
Postoperative Care
Immediate Postoperative Management:
Patients are monitored closely in the post-anesthesia care unit (PACU) and then transferred to a surgical ward
Pain management is crucial, often involving epidural analgesia or patient-controlled analgesia (PCA)
Intravenous fluids are administered, and early mobilization is encouraged
Nasogastric tube is typically removed once bowel function returns
Monitoring of vital signs, urine output, and drain output is essential.
Ostomy Care:
If a stoma is present, stoma care education is initiated early by a stoma nurse
Patients are taught how to manage their stoma, empty the appliance, and identify potential complications such as retraction, ischemia, or skin irritation
Regular stoma site assessment is performed.
Dietary Advancement:
Diet is advanced gradually as bowel function returns
Initially, clear liquids are offered, followed by a low-residue diet
Patients with stapled anastomoses may tolerate a regular diet sooner than those with hand-sewn anastomoses
Fiber intake is gradually increased as tolerated
Nutritional support may be required in patients with poor oral intake or malabsorption.
Complications
Early Complications:
Early complications include anastomotic leak, pelvic abscess, intra-abdominal sepsis, hemorrhage, wound infection, ileus, urinary retention, and sexual dysfunction
Anastomotic leak is a serious complication that can lead to sepsis and increased mortality
It may require re-operation, drainage, or conversion to a permanent stoma.
Late Complications:
Late complications can include incisional hernia, bowel obstruction due to adhesions, changes in bowel function (low anterior resection syndrome - LARS), sexual dysfunction, and urinary dysfunction
LARS is characterized by symptoms such as urgency, frequency, incomplete evacuation, and incontinence, which can significantly impact quality of life.
Prevention Strategies:
Meticulous surgical technique, especially in TME dissection and creation of a tension-free anastomosis, is paramount
Early detection and management of leaks through prompt diagnosis with imaging (CT scan) and appropriate intervention (drainage, antibiotics, re-operation) are critical
Prophylactic antibiotics, stoma formation for high-risk anastomoses, and careful patient selection for neoadjuvant therapy can help mitigate risks
Postoperative monitoring for signs of infection or leak is essential.
Prognosis
Factors Affecting Prognosis:
Prognosis is primarily influenced by the stage of the cancer at diagnosis, the completeness of the TME, the quality of the surgical margins (especially the circumferential resection margin - CRM), the presence of lymph node metastasis, and the patient's overall health
Achieving a clear CRM (>1 mm) is strongly associated with a lower risk of local recurrence and improved survival.
Outcomes With Treatment:
For early-stage rectal cancer treated with curative intent, the 5-year survival rates can be as high as 80-90%
For locally advanced disease, survival rates are lower but significantly improved with multimodal therapy including neoadjuvant treatment and TME
Long-term survivors may experience late complications affecting quality of life.
Follow Up Recommendations:
Postoperative follow-up is crucial for early detection of recurrence and management of long-term complications
This typically includes regular clinical examinations, CEA monitoring, colonoscopies, and CT scans
Surveillance schedules vary but usually involve more frequent visits in the first 2-3 years post-surgery, gradually becoming less frequent thereafter
Follow-up also addresses functional outcomes and quality of life.
Key Points
Exam Focus:
TME is the cornerstone of modern rectal cancer surgery
Key aspects for exams include indications for LAR, steps of TME dissection, importance of CRM, management of anastomotic leaks, and potential early/late complications like LARS
Understand the role of neoadjuvant therapy and its impact on surgical outcomes.
Clinical Pearls:
Achieving a good plane of dissection within the mesorectal fascia is critical
Identify and preserve pelvic autonomic nerves to minimize functional deficits
A diverting stoma is often a life-saver for high-risk anastomoses
Counsel patients thoroughly about potential functional outcomes and the possibility of LARS.
Common Mistakes:
Inadequate TME leading to positive CRM and local recurrence
Dissection outside the mesorectal fascia causing nerve damage or injury to adjacent organs
Inadequate bowel preparation or poor surgical technique leading to anastomotic leak
Failure to adequately counsel patients on functional outcomes and the need for a stoma.