Overview
Definition:
Transanal Endoscopic Microsurgery (TEM) is a minimally invasive surgical technique used for the local excision of benign and early-stage malignant rectal lesions
It utilizes a rigid rectoscope and specialized instruments operated through a binocular microscope, allowing for precise dissection in the plane of the mesorectal fascia and the creation of a three-dimensional view.
Epidemiology:
TEM is primarily indicated for rectal adenomas and early T1 rectal cancers (Stage I) located within the middle and upper rectum
Its use is increasing as an alternative to traditional transanal excision or more invasive abdominoperineal resections for selected lesions, particularly in patients who are poor surgical candidates for major abdominal surgery.
Clinical Significance:
TEM offers the advantage of preserving the anal sphincter function and avoiding a colostomy for select rectal lesions, thus improving quality of life
It provides excellent visualization and precise dissection, leading to complete tumor resection with clear margins and enabling accurate pathological staging
This technique is crucial for managing early rectal pathology while minimizing morbidity.
Indications
Benign Lesions:
Large or sessile rectal adenomas that cannot be removed endoscopically or via traditional transanal excision
Polyps in the upper rectum requiring a more controlled excision.
Malignant Lesions:
Early-stage rectal adenocarcinoma (T1N0M0) with no lymphovascular invasion, grade 1 or 2 differentiation, and located within the reach of the TEM scope (typically up to 15-20 cm from the anal verge)
Lesions where the mesorectal fascia is clearly free of tumor involvement.
Other Indications:
Recurrent rectal tumors after previous surgery
Selected leiomyomas or neuroendocrine tumors of the rectum
Palliation of symptoms in unresectable rectal cancers.
Contraindications
Absolute Contraindications:
Distant metastatic disease
Large or deeply invasive rectal tumors (T2 or beyond)
Significant anal stenosis or sphincter dysfunction
Rectal obstruction that cannot be relieved
Untreated sepsis or peritonitis.
Relative Contraindications:
Previous pelvic radiation therapy (increases risk of fibrosis and difficult dissection)
Significant comorbidities that make prolonged surgery or anesthesia risky
Tumors extending beyond the mesorectal fascia
Significant scarring from previous rectal surgery.
Procedure Steps
Patient Positioning:
The patient is typically placed in the lithotomy position, or sometimes in a prone position with pelvic elevation to facilitate rectal access and instrument manipulation.
Instrumentation:
A rigid rectoscope (4-10 cm diameter) is inserted into the rectum, creating a pneumorectum
Specialized instruments, including dissectors, graspers, scissors, and a cautery device, are passed through the rectoscope under direct visualization via a stereoscopic microscope.
Dissection Technique:
The rectal mucosa is incised around the lesion
Dissection proceeds in the plane of the mesorectal fascia, allowing for the precise removal of the full-thickness rectal wall segment containing the tumor
Careful attention is paid to achieving adequate margins, especially posteriorly to avoid pelvic organs.
Specimen Handling:
The resected specimen is retrieved and sent for histopathological examination to assess tumor type, depth of invasion, and margin status
The rectal defect is typically closed in layers using absorbable sutures to prevent leakage and promote healing.
Postoperative Care
Pain Management:
Postoperative pain is managed with analgesics, often including patient-controlled analgesia initially, followed by oral medications
Epidural analgesia may be considered for enhanced pain control.
Dietary Management:
Patients are typically kept nil per os (NPO) initially and advanced to a clear liquid diet as tolerated
A low-residue diet is often recommended for the first week to minimize bowel irritation and promote healing.
Wound Care:
The perineal wound (if any) is kept clean and dry
Rectal packing may be used temporarily
Routine wound care instructions are provided to the patient and family.
Monitoring:
Vital signs are closely monitored
Fluid balance is maintained
Patients are observed for signs of infection, bleeding, anastomotic leak, or other complications
Bowel function is assessed, and early mobilization is encouraged.
Complications
Early Complications:
Bleeding from the operative site, hematoma formation, infection of the operative site or pelvic abscess, urinary retention, temporary fecal incontinence, ureteric injury (rare).
Late Complications:
Rectal stricture formation, chronic fecal incontinence, rectovaginal fistula, recurrence of tumor if margins are involved or inadequate
Persistent pain.
Prevention Strategies:
Meticulous surgical technique with clear visualization and dissection in the correct plane
Achieving adequate surgical margins
Careful closure of the rectal defect
Judicious use of pelvic drains if indicated
Preoperative antibiotics and adequate bowel preparation.
Key Points
Exam Focus:
TEM is indicated for selected T1 rectal cancers and large adenomas
It preserves sphincter function
The procedure involves rectoscope, microscope, and specialized instruments
Dissection is in the plane of the mesorectal fascia.
Clinical Pearls:
Adequate pneumorectum is crucial for visualization
Dissecting too close to the tumor can lead to positive margins
Closure of the rectal defect is important to prevent leakage
Accurate histopathology is vital for staging and adjuvant therapy decisions.
Common Mistakes:
Inadequate visualization leading to piecemeal resection or injury to adjacent structures
Failure to achieve clear margins
Incomplete closure of the rectal defect
Misinterpretation of intraoperative findings leading to inappropriate lesion selection for TEM.