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Background: Recently, there have been many studies initiated to validate robotic TME. Also, there have been a variety of minimally invasive extraction techniques for protocolectomy ranging from trans-abdominal to trans-vaginal. However, there has been little comparison of robotic techniques combined with completely minimally invasive approach. The goal of this study was to describe our experience with robotic TME for very low rectal adenocarcinoma and compare trans-abdominal vs. trans-anal extraction.

Methods: This is a single institution, retrospective review comparing patients from December 2005 till August 2011who underwent robotic TME for rectal adenocarcinoma with coloanal anastomosis. The patients were stratified into two groups, trans-abdominal extraction or trans-anal extraction. Data were then collected on operative outcomes, complications, pathological specimen, etc. These groups were then compared using chi-square and t-test.

Results: Fifty four patients underwent robotic TME with low anastomosis. 40 had a trans-abdominal extraction and 14 a trans-anal extraction. Patient demographics, BMI, blood loss, ileus, anastomotic leak rate, hospital stay, and days to regular diet were not significantly different. However, there was a significant difference observed in operative time and distance from the anal verge (p-value < 0.05). Operative time for trans-anal was 350 ± 71 minutes compared to 290 ± 80 minutes for trans-abdominal. The trans-anal group average distance from the anal verge was 4.8cm while the average distance for the trans-abdominal group 6.8cm for the with a p-value of 0.0196. Hospital stay differed from 4.6 ± 3 days vs. 7.7 ± 8 days for the trans-anal and trans-abdominal groups respectively but did not reach clinical significance.

Conclusions: The feasibility of robotic TME has already been proven while its validity although early is comparable to laparoscopic TME. Furthermore, very low tumors amenable to sphincter preservation can lend themselves to a trans-anal extraction without compromising on operative and short term outcomes. In light of these equivocal results, this technique may be a more favorable option in patients when it is more difficult to get an adequate distal margin such as patients with a narrow pelvis (men), patient subsets with larger body habitus, or very low tumors. While the feasibility of trans-anal extraction is clear, larger numbers, prospective data, and patient stratification will be required to prove if there exists patient benefit to this technique.

Demographic and Operative Comparisons

		Anal Extraction	Abdominal Extraction	p-value
Age		56.9 (±9.1)	59.6 (±12.2)	0.4468
AJCC Stage	0	3 (21.4%)	9 (22.5%)	0.9045
	1	5 (35.7%)	11 (27.5%)
	2	1 (7.1%)	4 (10%)
	3	5 (35.7%)	14 (35%)
	4	0 (0%)	2 (5%)
ASA	2	6 (42.9%)	21 (52.5%)	0.5346
	3	8 (57.1%)	19 (47.5%)
BMI		29.7(±4.6)	27.6 (±4.6)	0.1499
Conversion to Open		0 (0%)	3 (7.5%)	0.2917
Days to Regular Diet		1.5 (±0.5)	2.8 (±3.3)	0.1413
EBL		241.1 (±146)	235.1 (±179.5)	0.9117
Nodes Harvested		14.3 (±4.7)	13.8 (±5.6)	0.7545
Length of Stay		4.6 (±2.9)	7.7 (±8)	0.1678
Distance from Anal Verge		4.8 (±2.2)	6.8 (±2.7)	0.0196
Operative Time		351.1 (±71.6)	290.9 (±83.7)	0.0200
Positive Nodes		1.1 (±3.7)	1.7 (±3.1)	0.6046
Complications		3 (21.4%)	15 (37.5%)	0.2723
Robotic Time			64.4 (±26.6)
Gender	Male	12 (85.7%)	27 (67.5%)
	Female	2 (14.3%)	13 (32.5%)
Tumor Size		1.7 (±2.3)	2.6 (±1.4)	0.1089