Overview
Definition:
Transanal Minimally Invasive Surgery (TAMIS) is a technique that utilizes specialized rigid and flexible instruments inserted through the anus for local excision of rectal lesions
It allows for a transanal approach to rectal tumors, offering visualization and maneuverability similar to laparoscopic or endoscopic procedures but with enhanced tissue handling and specimen retrieval capabilities
TAMIS aims to achieve complete tumor resection with clear margins, facilitating oncological safety and functional preservation.
Epidemiology:
TAMIS is increasingly utilized for benign and early-stage malignant rectal lesions
Its application is growing for adenomas with high-grade dysplasia, early rectal cancers (T1, selected T2), and polyps that are difficult to resect endoscopically due to size, location, or morphology
Patient selection is crucial, with lesions generally limited to the middle and upper rectum, and tumor size typically not exceeding 3-4 cm in diameter for optimal outcomes.
Clinical Significance:
TAMIS offers a minimally invasive alternative to traditional transanal excision (TAE) and transabdominal resections for select rectal tumors
It provides improved visualization, triangulation, and dissection capabilities compared to standard TAE, leading to higher rates of complete resection and reduced recurrence for appropriately selected lesions
This technique is particularly valuable in preserving sphincter function and avoiding the morbidity associated with abdominoperineal resection (APR) or low anterior resection (LAR) for early rectal malignancies.
Indications
Benign Lesions:
Large or complex rectal adenomas
Villous adenomas
Adenomas with high-grade dysplasia
Sessile polyps that are difficult to snare or forceps biopsy
Lesions in the middle to upper rectum (above the peritoneal reflection).
Malignant Lesions:
Selected T1 rectal adenocarcinomas with favorable histology (e.g., well-differentiated, no lymphovascular invasion, clear margins on initial biopsy)
Selected T2 rectal adenocarcinomas where sphincter preservation is paramount and oncological safety can be ensured
Lesions amenable to complete excision with a negative margin via a transanal approach.
Other Indications:
Recurrent polyps after previous endoscopic removal
Localized submucosal tumors (e.g., GISTs) that are suitable for local excision
Palliative treatment for symptomatic rectal tumors when curative resection is not feasible.
Contraindications
Absolute Contraindications:
Distant metastatic disease
Locally advanced rectal cancer (T3/T4) with invasion into surrounding structures
Significant anal stenosis precluding instrument insertion
Active severe inflammatory bowel disease in the anal canal or rectum
Unreconstructable anal sphincter incompetence.
Relative Contraindications:
Lesions extending beyond the middle rectum (higher recurrence risk)
Tumors with suspected deep muscularis propria invasion
Patients with a history of multiple pelvic surgeries or radiation therapy
Obesity with difficulty in anal access
Poor anesthetic risk
Large or bulky tumors exceeding TAMIS capabilities for complete resection.
Procedure Steps
Patient Positioning And Anesthesia:
Patient is typically positioned in the lithotomy position
General anesthesia or spinal anesthesia is usually employed
Anal preparation and sterile draping are performed.
Rectal Access And Visualization:
A rigid rectoscope or specialized TAMIS retractors are used to expose the lesion
The TAMIS platform, comprising rigid cannulas, is inserted transanally to create a stable working channel and provide a triangulation effect for dissection.
Dissection And Excision:
CO2 insufflation is used to improve visualization and create a pneumorectum
Specialized articulating instruments (graspers, dissectors, scissors) are passed through the TAMIS platform
Dissection is performed circumferentially around the lesion, extending into the submucosa or muscularis propria as dictated by the lesion type and depth
Careful attention is paid to achieving adequate margins and identifying critical structures.
Specimen Retrieval:
The excised specimen is typically retrieved intact using endoscopic retrieval bags or specialized specimen pouches to ensure complete specimen containment and prevent fragmentation, which is crucial for accurate pathological staging.
Closure And Hemostasis:
Hemostasis is achieved using electrocautery or other hemostatic agents
The rectal defect may be closed with sutures, particularly if it is large or involves the deeper layers of the rectal wall, to reduce the risk of pelvic sepsis
The anus is then inspected for any injury.
Postoperative Care
Pain Management:
Postoperative pain is managed with analgesics, typically including NSAIDs and opioid medications as needed
Local anesthetic infiltration at the surgical site can also provide prolonged pain relief.
Bowel Management:
Patients are usually kept on a clear liquid diet initially and advanced as tolerated
Stool softeners are often prescribed to prevent straining and facilitate bowel movements
Bowel preparation may be administered before the first bowel movement.
Monitoring:
Vital signs are monitored closely
Patients are observed for signs of bleeding, infection, or anastomotic leak (if a closure was performed)
Urine output is monitored, and urinary retention is a potential concern.
Discharge Criteria:
Discharge typically occurs once the patient is tolerating oral intake, has adequate pain control, is able to ambulate, and has no signs of complications
Clear instructions regarding wound care, diet, activity, and follow-up appointments are provided.
Complications
Early Complications:
Bleeding from the surgical site
Rectal pain and tenesmus
Urinary retention
Anal discomfort or irritation
Infection of the surgical site.
Late Complications:
Incomplete resection or local recurrence of the lesion
Anal stenosis or stricture
Fecal incontinence or altered bowel function
Pelvic sepsis if the rectal defect is not adequately managed
Rectovaginal or rectourethral fistula (rare).
Prevention Strategies:
Meticulous patient selection
Thorough preoperative assessment of the lesion's characteristics
Careful surgical technique with adequate visualization and margins
Complete specimen retrieval
Appropriate management of the rectal defect post-excision
Judicious use of stool softeners and pain management.
Prognosis
Factors Affecting Prognosis:
Histological grade of the tumor
Depth of invasion (T stage)
Presence of lymphovascular invasion
Completeness of surgical resection (margin status)
Skill and experience of the surgeon
Location and size of the lesion.
Outcomes:
For benign lesions like adenomas, TAMIS offers a high rate of complete eradication with minimal morbidity
For selected early rectal cancers, TAMIS can achieve oncological outcomes comparable to radical surgery, with the significant advantage of sphincter preservation and reduced functional deficits
Recurrence rates are dependent on lesion characteristics and adherence to oncological principles.
Follow Up:
Follow-up typically involves regular rectal examinations and endoscopic surveillance (colonoscopy and/or flexible sigmoidoscopy) to detect local recurrence or metachronous lesions
The frequency and duration of follow-up depend on the initial diagnosis and risk factors
Imaging modalities may be used for staging and restaging in cases of malignancy.
Key Points
Exam Focus:
TAMIS is a valuable technique for local excision of selected rectal lesions, offering improved visualization and dissection over traditional TAE
Key indications include large adenomas and early-stage rectal cancers where sphincter preservation is desired
Complete resection with negative margins is paramount for oncological outcomes
Complications include bleeding, pain, and potential recurrence.
Clinical Pearls:
Always assess the lesion's size, location, and depth of invasion meticulously preoperatively
Ensure adequate visualization by CO2 insufflation and proper rectoscope positioning
Use articulating instruments for optimal dissection
Retrieve the specimen intact in a bag to prevent fragmentation and ensure accurate pathology
Close large defects in the rectal wall to minimize sepsis risk.
Common Mistakes:
Attempting TAMIS for lesions that are too large or deeply invasive
Inadequate visualization leading to incomplete resection or injury to surrounding structures
Failure to achieve clear margins
Poor specimen retrieval leading to fragmented pathology
Neglecting to close significant rectal wall defects, increasing the risk of pelvic sepsis.