Lilianacb wrote:...The surgeon thinks it is cancer and suggested a Lower anterior resection. After looking in several websites, I noticed that 20 cm from anal verge is the sigmoid colon, not the rectum. Then why a LAR was suggested and not a sigmoid resection?...
I think the answer to your question probably revolves around the definition of “Complete Mesocolic
Excision (CME)”, which is the type of conservative surgery they would want to do if the tumor is clearly located in the sigmoid colon area . I think that this type of surgery is usually performed using a sigmoid resection or a left-hemicolectomy. On the other hand, the removal of a tumor in the mid or upper rectum would involve what is called Total Mesorectal
Excision (TME), and is usually performed using the LAR procedure – either open or laparoscopic
But it may be the case that the tumor is located low down in the sigmoid area close to the rectosigmoid junction, in which case the situation is a bit more complicated.
As discussed in the article below, the decision really depends on anatomy and where, exactly, the tumor is located, and where the nearby relevant lymph node ganglia are located.
I think that the overall constraints are probably something like the following:
They will want to remove the tumor with plenty of margin both above and below the tumor. If your tumor is located at 20cm above the anal verge, then the lower cut might be at around 15cm from the anal verge. The lower cut has to be well below where the tumor is located so that there is no chance that the tumor margin will be pierced by the scalpel. But the lower cut also has to be below where the relevant lymph nodes are located because they will want to remove all of the “at-risk” lymph nodes at the same time. Depending on where the tumor is located and what its drainage pattern is, the relevant lymph node ganglia might be high up or low down with respect to the tumor. This is what the surgeon has to figure out by using his knowledge of anatomy.
So, it might turn out that the best place to make the lower cut would actually be in the upper rectum area, even though the tumor itself is in the lower sigmoid area. This might be why the surgeon said “LAR” rather than “left hemi-colectomy”or “sigmoid resection," because LAR is typically used whenever any part of the rectum is going to be removed.
Ï think you would have to talk to the surgeon to ask what considerations are relevant for his decision about the type of surgery to use.
I don’t know the answer to your question. Maybe you can get some additional perspective by reading articles like the one below.Complete mesocolic excision: Lessons from anatomy translating to better oncologic outcomehttps://www.ncbi.nlm.nih.gov/pmc/articles/PMC4789608/
In any event,whatever the situation might be it is very important to have an experienced, Board-Certified colorectal surgeon doing the surgery, especially if the lower cut is likely to be in the upper-rectum area, since this is where some of the important muscles and control mechanisms for bowel movement are located, and which must be preserved if the patient hopes to have normal bowel movements after the surgery is finished.