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63
on multivariate analysis was a shorter anastomotic distance from
the anal verge (p=0.001 and p<0.001, respectively). Based on
this study, many surgeons including me favor stoma diversion for
all colorectal anastomoses within the distal 7cm from the anal
verge, regardless of previous radiotherapy or other risk factors. I
realize it is possible to be more selective and that ileostomy man-
agement and ileostomy closure are associated with their own mor-
bidity. However, a stoma diversion, typically an ileostomy in my
case, at least reduces the degree of morbidity should an anasto-
motic leak occur. An anastomotic leak following an undiverted
low colorectal or coloanal anastomosis easily leads to permanent
colostomy. It is true that diffuse peritonitis after diverting ileos-
tomy closure can be a challenging situation, especially in a high-
risk patient, but this complication does not lead to permanent
colostomy. This study carries inevitable limitations. Most of the
anastomoses in the analysis were created using the single-stapled
technique, while most of us prefer the double-stapled technique,
which both in the present and in many other subsequent studies
has not been associated with an increased risk of anastomotic fail-
ure. Some important variables such as preoperative use of radia-
tion therapy or steroid use were not signicant factors in the
analysis but seemed underpowered to provide reliable data.
Importantly, the study population is obviously limited to open sur-
gery and does not provide information on colorectal anastomoses
performed using minimally invasive techniques. A recent review
examining 25 studies indicated a median anastomotic leak rate of
7.3%, ranging from 0.7% to 24.5%. The most commonly reported
predictors of anastomotic leak after the double-stapled technique
were low tumor location, multiple stapler rings, male sex, longer
operation time, and perioperative blood transfusion [1]. While
there is still debate on the relationship between multiple staple
rings for rectal transection and colorectal or coloanal anasto-
motic leak, all other variables are widely accepted as risk factors,
although they were not clearly identied in the present article.
Despite its limitation, this work establishes a useful, practical
guideline based on clear numbers to inform a surgeon’s decision
on when to create a stoma diversion in addition to low anterior
resection.
LS
64
Reference
1. Emile SH, Barsom SH, Elfallal AH, Wexner SD.Comprehensive
literature review of the outcome, modications, and alterna-
tives to double-stapled low pelvic colorectal anastomosis.
Surgery. 2022;172(2):512–21.
Discussion
DC
My comments on this article are similar to the Mathiessen article
(Chap. 17). The distance from the anal verge of a potential anas-
tomosis is a marker for multiple factors that increase the risk of a
leak, which are surgery-specic factors (tension, blood supply,
how much distal bowel is left), patient factors (immunosuppres-
sion, general health), and what a leak would entail for the specic
patient in question. I might not divert if the patient has no history
of radiotherapy, the anastomosis had no tension, and there was
good blood supply.
MD
What is your cutoff?
DC
Well, there are patients where the colon does not reach well, or the
operation is just more difcult.
MD
This paper nicely demonstrates risk factors associated with the
anastomotic leak, particularly with regard to the level of the anas-
10 Distance from the Anal Verge and Anastomotic Leak…
65
tomosis. Being trained at Cleveland Clinic, this was always a
guide for when to divert patients undergoing low anterior resec-
tion, and I continue to use this in my practice today. Dr.
Colibaseanu mentioned that for him, regardless of the height of
the anastomosis, he is comfortable with a primary anastomosis
and not diverting if there is no tension, adequate blood supply, and
optimal patient characteristics (no immunosuppression, not mal-
nourished, etc.). Diverting loop ileostomy comes with its signi-
cant potential complications, particularly dehydration, electrolyte
abnormalities, and acute renal failure.
In my opinion, the risk of long-term consequences of an anas-
tomotic leak and pelvic sepsis with a low pelvic anastomosis (less
than 5cm) that could result in a permanent stoma or signicant
functional compromise outweighs the benets of avoiding fecal
diversion in these cases. Though patients may suffer short-term
complications from a diverting loop ileostomy, this fecal diver-
sion may ultimately aid in salvaging their rectum or preserving
anorectal function should an anastomotic leak occur. While again
it is not just a strict cutoff, even in a healthy individual who may
have no other medical issues and an anastomosis at 4–5cm, even
when everything looks great. I am more liberal in diverting. More
so because at the same time, I would not want my young, healthy
patient to leak and then end up needing a permanent stoma or hav-
ing very poor function because of an undiverted leak.
The main drawbacks I nd in this study that do not apply to my
practice are the primary use of a single-stapled technique and
open surgery. That being said, the quality of surgery reported in
this large study from a high-volume institution speaks to the
validity of their ndings, and so I continue to use a 7cm cutoff for
when to consider fecal diversion in patients undergoing low ante-
rior resection.
AM
I think similarly to the comments we had on other papers. To me,
it is never really a height number because the measurement from
the anal verge can be very variable, as everyone’s kind of stated,
Discussion
66
and we have all encountered that, and everyone’s anuses are a
little bit of a different length. Just picking a cutoff to me does not
really make much sense, and it is instead a number of factors we
put back together to make a judgment regarding whether we think
the risk of diversion is lower than the risk of a leak.
LS
This is an old article that presents evidence supporting the idea of
different risks based on the distance of the anastomosis from the
anal verge, although I recognize that the decision to add a stoma
diversion remains multifactorial. As we are discussing this article,
I feel we go through themes which recur in the discussion of other
articles about anastomotic leak risk factors or when we should
divert. I agree that these were all open cases, and a single-stapled
technique was used in the majority of patients, which might not
relate to many contemporary cases.
DC
From my perspective, there are very specic factors that are asso-
ciated with a higher leak rate in lower anastomosis. Those are
very practical ones. Reach (and therefore tension) is almost
always the primary culprit here. A mid rectal anastomosis with no
tension, in an otherwise unremarkable operation, in a healthy
patient should have a very low risk of a leak. I do not think there
is anything mysterious at all about how low an anastomosis exists;
as long as the blood supply is great, there is no tension on the
anastomosis in an otherwise technically adequate surgery.
You make the point of focusing on what to do if they leak. If I
can reach the anastomosis and over-sew it, I think about not
diverting, but obviously all the other factors I’ve mentioned above
need to be considered.
I concede the point to Michelle that a low anastomotic leak
without diversion is very difcult to rescue if a permanent stoma
is to be avoided.
10 Distance from the Anal Verge and Anastomotic Leak…
67
© The Author(s), under exclusive license to Springer Nature
Switzerland AG 2025
D. Colibaseanu et al., Essential Articles in Colorectal Surgery,
https://doi.org/10.1007/978-3-031-77745-5_11
11
The Fundamental Role
ofMagnetic Resonance
inRectal Cancer Staging
MERCURY Study Group. Diagnostic accuracy of preoperative
magnetic resonance imaging in predicting curative resection of
rectal cancer: prospective observational study. BMJ.
2006;333(7572):779.
Abstract
Objective: To assess the accuracy of preoperative staging of rec-
tal cancer with magnetic resonance imaging to predict surgical
circumferential resection margins.
Design: Prospective observational study of rectal cancers
treated by colorectal multidisciplinary teams between January
2002 and October 2003.
Setting: 11 colorectal units in four European countries.
Participants: 408 consecutive patients presenting with all
stages of rectal cancer and undergoing magnetic resonance imag-
ing before total mesorectal excision surgery and histopathological
assessment of the surgical specimen.
Main outcome measures: Accuracy of magnetic resonance
imaging in predicting a curative resection based on the histologi-
cal yardstick of presence or absence of tumor at the margins of the
specimen.
Results: 354 of the 408 patients had a clear circumferential
resection margin (87%, 95% condence interval 83–90%). Speci-
city for prediction of a clear margin by magnetic resonance
68
imaging was 92% (327/354, 90–95%). High-resolution scans
were technically satisfactory in 93% (379/408). Surgical speci-
mens were histopathologically graded as complete or moderate in
80% (328/408), and the median lymph node harvest was 12 (range
0–49). Magnetic resonance imaging predicted clear margins in
349 patients. At surgery, 327 had clear margins (94%, 91–96%).
Conclusion: High-resolution magnetic resonance imaging
accurately predicts whether the surgical resection margins will be
clear or affected by tumor. This technique can be reproduced
accurately in multiple centers to predict curative resection and
warns the multidisciplinary team of potential failure of surgery,
thus enabling selection of patients for preoperative treatment.
DC
This was a prospective observational study originating from 11
hospitals in 4 European countries. The primary objective of this
study was to assess the accuracy of Magnetic Resonance Imaging
(MRI) to predict negative surgical resection margins. This study
enrolled 408 patients from January 2002 to October 2003.
In addition to MRI evaluation by the 18 radiologists (5–20years
experience in abdominal MRI) who underwent workshops in
preparation for this study, 30 colorectal surgeons evaluated the
tumors with a digital rectal examination and exible sigmoidos-
copy. All patients were discussed preoperatively at multidisci-
plinary tumor team meetings. For patients with threatened
margins, they had either extended resections, radiation, or chemo-
radiation prior to surgery. All pathologists were experienced GI
histopathologists who underwent specialized workshops to pre-
pare for this study.
Ultimately, in patients who went straight to surgery (i.e., they
were predicted to have a negative margin), the accuracy of predict-
ing a clear margin was 91% with a negative predictive value of
97%. In those who had received radiation or chemoradiation ther-
apy, the accuracy was 77% with a negative predictive value of 98%.
The difculty with the MRI was in distinguishing those
patients who had tumor or treatment scarring at the margin, over-
11 The Fundamental Role ofMagnetic Resonance inRectal…
69
calling tumor even in cases where there was treatment effect but
no residual tumor.
I think that this was a pivotal study in the treatment of rectal
cancer. Prior to this point—and the results of this did not trickle
down for a few years—it seemed that staging could be assessed
with either endorectal ultrasound or MRI; now, nearly universally,
I will obtain an MRI.The only addition (and not exception) would
be adding EUS for a case where MRI cannot distinguish between
a T1 and T2, and I am considering a transanal approach, or if there
is a node in a T1 tumor that looks suspicious and is accessible
transanally.
So, from my perspective, the proverbial horse is out of the
barn. I do not see us ever not using MRI as the primary modality
for local staging of rectal cancer. In fact, multiple (and I lost count
of how many) MERCURY babies (f/u studies) have proven the
utility of MRI by showing that the depth of extramural tumor is
also predictable [1], and MRI is also very good for determining
circumferential margin and distal margin in post chemoradiation
treatment [2]. So, I think the matter is settled for me. Maybe the
second biggest advance since total mesorectal excision (TME).
References
1. MERCURY Study Group. Extramural depth of tumor invasion
at thin-section MR in patients with rectal cancer: results of
MERCURY study. Radiology. 2007;43(1):132–9.
2. Patel UB, etal. MRI after treatment of locally advanced rectal
cancer: how to report tumor response—the MERCURY expe-
rience. AJR. 2012;199:486–95.
Discussion
DC
If I do not have an MRI ready for a case presentation at the tumor
board, I will have to relist the case until I get the MRI.It is very
Discussion
70
rare that we could even think of a situation where we would not
use MRI.
MD
Yes, I completely agree; this study marked a pivotal change in
how we approach the staging of rectal cancer, to the extent that it’s
now integrated into the NCCN guidelines, advocating MRI as the
preferred imaging tool. It’s remarkable that the study compared
MRI to a digital rectal exam, a comparison almost unfathomable
today. Regardless, the study effectively supplanted ultrasound in
our staging protocols, except in the smaller T1 and T2 lesions
where ultrasound has improved accuracy.
Now, we have to remember, this study was published in 2006…
Fast forward to today, in the era of total neoadjuvant therapy
(TNT), where nonoperative management and a watch-and-wait
approach are increasingly utilized and often preferred. Now, the
conversation surrounding MRIs revolves around staging tumors or
predicting a complete clinical response, post-neoadjuvant chemo-
radiation, and TNT which differs signicantly from its accuracy in
staging untreated tumors, as evidenced by newer literature. Though
the accuracy of ultrasound is notoriously operator-dependent,
there is also signicant variability in MRI which is dependent on
factors like machine quality, software, and technique.
LS
I agree, it is impressive how this study still denes the manage-
ment of rectal cancer over 20years after the enrollment of the
original study patients. Reading that the accuracy of the MR was
compared to digital rectal examination speaks to how revolution-
ary this study was. Our weekly tumor board discussions on neo-
adjuvant treatment and surgery for rectal cancer remain centered
around MR images. In addition, the role of MR is critical when
deciding on pelvic lymphadenectomy or intraoperative radiother-
apy. One aspect that is also problematic to me is to note a persis-
11 The Fundamental Role ofMagnetic Resonance inRectal…
71
tent difference in quality among MRs performed in different
institutions, despite the original impetus to establish workshops
for radiologists, for which the original authors of this multicenter
study advocated. At the same time, similar workshops involved
pathologists and, of course, surgeons, to standardize rectal cancer
management. I feel that rectal cancer treatment in general is better
today than it was 20years ago, and part of the credit for it should
go to the MERCURY trial. However, I wish that the quality of MR
pelvis to stage rectal cancer was as consistent as a CT chest, abdo-
men, and pelvis, for example.
I admire those who designed this trial because I think that con-
ceiving MR as a staging modality comes along with conceiving
circumferential radial margin as the critical regional staging mea-
surement, and I think that our oncologists feel the same. However,
circumferential radial margin is not the only factor, because I
think that lymph node involvement in the mesorectum is an inde-
pendent factor associated with risk of recurrence. The other issue
that has been investigated through the MR images is the involve-
ment of the pelvic lymph nodes, and MR remains suboptimal in
assessing lymph nodes. So, there is still a subset of patients who
have silent, invisible involvement of pelvic lymph nodes, and they
ultimately recur because of that.
Discussion
73
© The Author(s), under exclusive license to Springer Nature
Switzerland AG 2025
D. Colibaseanu et al., Essential Articles in Colorectal Surgery,
https://doi.org/10.1007/978-3-031-77745-5_12
12
Preoperative vs.
Postoperative
Chemoradiotherapy
forRectal Cancer
Sauer R, Becker H, Hohenberger W, etal., German Rectal Cancer
Study Group. Preoperative versus postoperative chemoradiother-
apy for rectal cancer. N Engl J Med. 2004;351(17):1731–40.
Abstract
Background: Postoperative chemoradiotherapy is the recom-
mended standard therapy for patients with locally advanced rectal
cancer. In recent years, encouraging results with preoperative
radiotherapy have been reported. We compared preoperative
chemoradiotherapy with postoperative chemoradiotherapy for
locally advanced rectal cancer.
Methods: We randomly assigned patients with clinical stage
T3 or T4 or node-positive disease to receive either preoperative or
postoperative chemoradiotherapy. The preoperative treatment
consisted of 5040cGy delivered in fractions of 180cGy per day,
5days per week, and uorouracil, given in a 120-h continuous
intravenous infusion at a dose of 1000mg per square meter of
body-surface area per day during the rst and fth weeks of radio-
therapy. Surgery was performed 6weeks after the completion of
chemoradiotherapy. One month after surgery, four 5-day cycles of
uorouracil (500 mg per square meter per day) were given.
Chemoradiotherapy was identical in the postoperative-treatment
group, except for the delivery of a boost of 540cGy. The primary
endpoint was overall survival.