at the end of the beginning ... but in the end........ does it matter

The sigmoid begins at the pelvic brim and ends opposite the third sacral piece (not the sacral promonotory as mistakenly thought)

First of all , what is your aim for this question?

for us, from the view of rectal cancer, the treatment plan of recutm and sigmoid is completely different. And the best way to answer is rigid rectosigmoidoscope,

Up to 15- 20 cm from anal verge, we consider it as rectum.

Phylosophically speeking I agree with dr Fedorowicz

Anatomically, it as question of blocos supply.

Thank you Zacharoula... in the end is it important does it matter what impact will this information have on patients and anyway dont we have some far more serious healthcare matters to address and solve? ....irrespective of anatomical 'dissonance'  on the colon

Hi Zbys. It matters in so far as staging and management of rectal and sigmoid cancer are completely different. If you have a tumour at 14 cm by rigid proctoscopy-- in Korea/the US, that's classified as a sigmoid cancer. If you're in Europe/Germany-- that's classified as a rectal cancer. And you'll be managed completely differently. Studies have also shown, as you would have guessed, that people have different lengths of rectum... so the measurement from the anal verge is actually very arbitrary.

Chaos reigns ....as usual no consistency in agreemet or disagreement ... but it keeps the research community busy

Dear Nigel,

Based on the local recurrence rate of rectal tumors, the National Cancer Institute establish the length of the rectum to be 12 cm above the anal verge (> 12 cm, local recurrence same with colon cancer; < 12 cm local recurrence similar with middle rectum).

From a classical & surgical point of view, the upper limit of the rectum is at the third sacral vertebra, and the inferior limit is represented by the anal verge.

However, a universally accepted length is 15 cm from the anal verge, and may be divided into three segments:

• Upper rectum: 11 – 15 cm from the anal verge, covered by peritoneum on its anterior and lateral sides.
• Middle rectum 7 – 11 cm from the anal verge, covered by visceral peritoneum only on its anterior surface.
• Lower rectum: 0-7 cm from the anal verge.

Other clinicians are considering 0-5 cm, 5-10 cm, 10-15 cm as boundaries for lower, middle and upper rectum, respectively. 

On the other hand, in Gray's anatomy there are two different anatomical structures: anal canal and rectum.

The anatomic anal canal is 2 cm long (anal verge-dentate line), while the surgical anal canal has a length of 4 cm from the anal verge (anal verge - puborectal muscle).

Measurement of rectal tumors from the anal verge should be done with a rigid proctosigmoidoscope and not with a flexible instrument which introduces an important degree of variability.

https://www.amazon.com/SURGICAL-ANATOMY-ABDOMEN-Mircea-Beuran-ebook/dp/B01NBK86YD/ref=sr_1_fkmr0_3?ie=UTF8&qid=1487080767&sr=8-3-fkmr0&keywords=negoi+i

Dear Dr Negol,

Thank you for your reply. I also read the NCI rationale for the 12cm cut-off. What was even more interesting were the dates of the studies they cited-- mid 1980s! TME, imaging, radiotherapy, chemotherapy, pathology have come on a long time since then. Not sure we can trust that data.

I think the other question is-- do you think a cancer at 13cm is definitely a sigmoid cancer in all patients?

BW

Nigel

Nigel

in your own words  "the measurement from the anal verge is actually very arbitrary" if this issue is so vital to Tx strategy as you indicate then why hasnt the 'arbitrariness" been resolved seems to me that some form of consensus should be reached and in any event does the data show that the discrepancy in the location  of the 'end' has any impact on survival in the end?

Nigel,

The answer of Ionot is very useful to have global insight. I would insist on the fact that 15 cm from anal verge is the common base to determine the end of sigmoid and the beginning of rectum (3cm anus + 12 cm rectum).

But anatomically, when I operate, the mobile part is the sigmoid as we know that left and rectum are normally fixed. That's why management of cancer is different because we can irradiate fixed part and not mobile part. That can solve some of your matter.

Best regards.

Hi Luc,

Do none of your patients have rectums shorter than 12 cm?

BW

Nigel

Basically, I would also agree with Luc, namely to consider the anus being between 2-4 cm (average 3) and the rectum 12 cm (lower, middle and upper rectum each 4 cm). However, individual anatomy certainly does not abide to cm, so the promontory may be a more generic reference for the recto-sigmoidal transition.

BR

Roman

Hi Nigel,

Most of the time we have patients with rectum longer than 12 cm instead of shorter. Very few patients had less than 12 cm.

BR

Luc

Dear Nigel, during my daily clinical practice I am using as a standard the 15 cm definition (0-7, 7-11, 11-15 cm).

A tumor located at 13 cm is a upper rectal tumor. > T2 and/or N 0 on pelvic MRI - neoadjuvant chemotherapy. If obstructive - laparoscopic loop colostomy.

I think that anatomical landmarks that point the embriological development should be taken into account, especially in oncological situations and diverticulitis. So, rectum begins where the taenia  coli disappears.

For the purposes of my PhD I am looking at factors associated with anterior resection  complexity. I have to say that even though there is variance in the reported length of the rectum, most papers I've read define the rectum to extend 4 to 16 cm from the anal verge. Having said that I agree that the measurement from the anal is arbitrary, we see that in clinical practice where the measurements on the pre-op MRI do not always coincide with peri-operative findings. The rather obvious answer would be the peritoneal covering - e.g. a tumour below/crossing that should be considered rectal. From a surgical point of view, if a tumour is resectable, either in the sigmoid or rectum a high anterior resection or partial mesorectal excision will take place. After that, the answer whether there is need for additional oncological treatment, as well as if the tumour is located in the rectum or sigmoid that would be given by the specimen retrieved. It would be interesting though if we had a radiologist, a pathologist and an oncologist answering this question, especially in the scenario of the patient being treated by medical oncology.

According to gross anatomy, at the proximal end, the rectum is the point where the taenia coli no longer exist and inferiorly, the anal canal is the portion between the verge and puborectalis. 

However, as everyone has mentioned, the relevance is when managing cancer. Rather than using one tool, it is essential to take all available information into account when managing individual patients; hence the importance of the MDT where radiologists, oncologists and pathologists contribute to the information that guide our clinical decisions. Yes, standardisation of description is essential when international exchange of ideas is considered and for this reason, I would use the 5-5-5cm marks when examining a patient in clinic with a rigid scope (which should be described as a proctoscope and not a sigmoidoscope; the shorter scope that examines the anal canal being labelled an anuscope).

What subset data analysis has shown us over the years is that upper rectal cancers, those whose lower limits are between 15-10cms from the verge do not require neoadjuvant radiotherapy, similar to sigmoid cancers. As we all know, MRI and further definition of pathology has allowed us to classify tumours into good and bad T3s, which classification, as surgeons we should now insist upon for decision-making, irrespective of AJCC's omission of this. (See the paper in this month's Colorectal disease by N Haboubi and R Nicholls, with which I agree). Thus, if I had a patient of Acromegalic proportions (who we know, is genetically predisposed to colorectal neoplasia) who had a "bad" T3, situated between 10cm to 13cms from the verge, all within the accessible bony pelvis, of course I would push for radiotherapy. I could keep varying the depth/length/pathology findings and come up with different recommendations in this particular case. Height is but one description of a tumour in an individual patient; as clinicians I hope we all see beyond the numbers(pun intended)!

Overtreatment with radiotherapy, we all now agree is not a substitute for quality of surgery in T1-3as; Habr-Gabba's work will influence the management of the approx 22% "responders" in the advanced stages and I believe we are not using the Papillion technique enough in early T1 tumours. 

In the U.K. we do classify ultralow resection-anastomoses as those where the staple line is within the last couple of cms from the verge. I find even this definition varies in the Antipodes, and in a young fit patient with an intact, muscular anal canal (which, by the way can vary between 2 & 5 cms in length), it is always a joy to see just how much length one gains after TME mobilisation such that one cannot doom a patient to an APER preoperatively. Research in Leeds, UK did try to volumise the rectum and anal canal on MRI, but as far as I know, direct clinically relevant correlations between scans and surgery was not found. Further, in patients undergoing new-adjuvant treatment, tissues do not remain as supple which should be remembered. Thus, patients are consented for "best-outcome-achievable", where the sole outcome of importance is a clear resection margin if possible; continuity is an added, undeterminable bonus for the patient. Even in young patients undergoing IPAA for mucosal disease e.g. UC, we always consent them for the 1% possibility of being unable to get a pouch to reach. 

Thus, I give a long version of the initial response to this answer - what difference does it make clinically, for an individual patient with a rectal cancer, where it is but one of many factors that must be considered in decision-making? The importance of absolute clarity when communicating, of course, remains indisputable and is essential to aavoid"big data" becoming no more than a "Big mess". 

There appears to be no end.... in sight to end this topic ;-)

No straight answer as I see, it is certainly important from therapy point of view.