Transanal Minimally Invasive Surgery (TAMIS) for Mid Rectal Carcinoma in Situ
A 56-year-old man underwent a screening program. On colonoscopy, 8 cm from the anal verge, an 8-mm tumor was found. Histopathology showed a well-differentiated adenocarcinoma, without lymphovascular invasion. Whole-body CT showed no distant metastasis, and no tumor was visible on pelvic MRI. The patient was placed in a prone jackknife position. Full-thickness tumor excision was performed using transanal minimally invasive surgery. Final histopathology showed a well-differentiated carcinoma in situ and R0 resection.
- Patient preparation: In a 56-year-old man, an 8-mm ulcerated lesion 8 cm from the anal verge, on the anterior rectal wall, was found. The histopathology report showed well-differentiated adenocarcinoma, without lymphovascular invasion. Whole-body CT showed no distant metastasis, and no tumor was visible on pelvic MRI. The patient underwent bowel preparation with enemas and thrombosis prophylaxis the day before surgery. Just before the surgery, patient took antibiotics (500 mg of metronidazole and 1.5 g of cefuroxime).
- Patient position: The patient was placed in a prone jackknife position, but just a simple lithotomy position may be used in all the cases depending on the localization. The disadvantage of the prone jackknife position is a possibility of repositioning the patient in the case of peritoneal entry. For the surgeon more familiar with transanal endoscopic microsurgery, the patient can be placed in a position so that the tumor is always on the posterior side: if the tumor is in the ride side of the rectum wall, the patient is placed on the right lateral side; if the tumor is in anterior wall, the patient is placed in prone jackknife position. A lesion located on the posterior wall can be reached with the patient in the lithotomy position.
- Critical steps: The Trendelenburg position can be added if needed. A video monitor is placed over the abdomen between the patient’s legs. The patient can then be prepared and draped in the normal fashion. If peritoneal entry is anticipated, the abdomen can be prepared preemptively as well. Initial pressure settings should be between 8 and 18 mm Hg and can be increased if needed. Routine placement of a Foley catheter can be considered. If peritoneal entry is anticipated, the steep Trendelenburg position is suggested. Simple cautery can be used or an advanced sealing device. If a vessel sealer is used, extra care should be taken when dissecting the tumor on the anterior wall. There is a high risk of damaging the vagina (in women) and the urethra (in men).
- Technical pearls/tips: The procedure starts with marking the safe margin (for cancer it should be 10 mm; for a benign lesion, 5 mm). Then we recommend starting dissection at the right posterior angle. Full-thickness or partial-thickness dissection should be performed. If the cancer is suspected, full-thickness excision is recommended; of a benign tumor, partial thickness is enough. Yellow tissue is the mesorectum; this is a mark showing that you have removed all the layers of the bowel wall. It is worth mentioning that excessive tumor manipulation should be avoided. We recommend gentle manipulation to avoid disruption of the specimen or spreading of tumor cells. In most of the cases, we intend to close the defect. For suturing the defect, we use 3/0 STRATAFIX (Ethicon US, LLC) suture. If the defect is wide, start by placing a single suture in the middle of the wound to compress both edges. When the tumor is in the extraperitoneal part of the rectum or the defect is wide, it is possible to leave it open.
- Potential areas for injury/complication: A very important pitfall is entering the peritoneal cavity. This is more common when the tumor is in the upper third of the rectum, or in the middle third on the anterior wall. It is not a complication, but the peritoneum has to be sutured securely. If the tumor is lower, and the peritoneum was not entered, the wound can be left open. If the tumor is on the anterior wall, the vagina (in women) or urethra (in men) can be injured if the dissection is performed too deeply. In addition, caution should be taken if a vessel sealer device is used (due to a thermal lesion within close proximity). In the lower third of the rectum, injury to the sphincter is possible.