Добавил:
Sekretar
kiopkiopkiop18@yandex.ru
t.me/Prokururor I Вовсе не секретарь, но почту проверяю
Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз:
Предмет:
Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_911_Библиотеки_им_академика_М_И_Перельмана
.pdf
Colonoscopy and flexible sigmoidoscopy
large sessile polyps extending beyond 50% of
the bowel wall circumference, low rectal polyps
extending beyond the dentate line, or lesions
encircling the appendix orifice.
It is recognized that serrated lesions are also more
difficult to resect as they have indistinct edges.
55
56
Small polyps less than 4 mm in size can be removed
by cold forceps or cold snare. Hot biopsy is now
no longer recommended by either the American or
European endoscopy societies. Larger-stalked polyps
are best removed using a conventional large or minisnare. The stalk should be transected approximately
halfway between the polyp and the bowel wall.
This ensures a clear resection margin whilst leaving
sufficient stalk in place to facilitate endoscopic
treatment should post-polypectomy bleeding occur.
Diathermy unit settings should be chosen to ensure
enough coagulating current is applied to allow
adequate haemostasis of the blood vessels within
the polyp stalk. A validated Direct Observation
of Polypectomy Skills (DOPyS) assessment tool
has been developed to assist with the training and
evaluation of polypectomy technique,57 and is now
in clinical use for competency assessment of trainees
and in the Bowel Cancer Screening accreditation
processes in England.
Retrieval of the polyp is important to determine
the histology and grade of dysplasia. Small polyps
can be sucked through the scope into a polyp trap,
while larger polyps can be grasped or snared and
withdrawn with the scope. Retrieval baskets or nets
are particularly useful for retrieving more than one
piece of tissue or multiple polyps.
Endoscopic mucosal resection (EMR)
EMR involves injection of fluid into the submucosal
space to lift the mucosa (and the polyp) away from
the muscle layer of the bowel wall (Fig. 2.6). This
facilitates removal of sessile or flat lesions, reducing
the risk of thermal injury to the bowel wall.58 The
authors find the addition of adrenaline (1:200 000)
to improve haemostasis and a few drops of methylene
blue to differentiate the submucosal plane helpful.
Large lesions (>2 cm) can be removed in a piecemeal
fashion safely using a submucosal lift.
Polyp recurrence may be reduced following
piecemeal resection by the judicious use of argon
plasma coagulation (APC) to destroy small areas of
residual polyp around the resected margin.
59
Polyp
Figure2.6 • Technique for endoscopic mucosal resection.
Downloaded for Anonymous User (n/a) at Rutgers University - NERL from ClinicalKey.com by Elsevier on March 22, 2019.
For personal use only. No other uses without permission. Copyright ©2019. Elsevier Inc. All rights reserved.
Mucosa
Submucosa
Muscle
21
Chapter 2
Revised St Mark's Colonoscopic Tattooing Protocol 2011
Indications
• Prior to surgery to localise
pathology
• To mark lesions for endoscopic
surveillance
• Do not tattoo rectal lesions as
they disrupt surgical planes
• There is no need to tattoo lesions
in the caecum; however, if in
doubt, then place a tattoo
Equipment
• Primed variceal injection needle
with 10mL syringe filled with
normal saline
• 5mL syringe filled with Spot
0.9mL sterilised Black (Indian)
Ink made up to 5mL with normal
saline)
®
(or
Procedure
• Direct needle at an angle to
mucosa
• Raise a bleb using 1-2mL of
saline
• Swap to syringe filled with
®
Spot
• Inject 1mL into the bleb to create
tattoo
• Swap to syringe filled with saline
and flush ink out with 1mL saline
before removing needle
• Repeat process for 3 tattoos
or Indian Ink
Place 3 tattoos distal to lesion Place tattoos 120° apart as close
Remember: To document how many tattoos were placed and the position relative to the lesion
Figure2.7 • St Mark’s colonoscopic tattooing protocol.
The ‘non-lifting’ sign, when a polyp fails to lift with
a submucosal injection, should raise a suspicion of
malignant invasion of the submucosa. Lesions that
do not lift should be biopsied, tattooed (Fig2.7) and
referred for expert assessment and consideration of
surgical resection.
Investigation of acute lower
gastrointestinal (GI) bleeding
The lower GI tract accounts for a quarter to a
third of all hospitalised cases of GI bleeding,60 with
diverticular disease being by far the most common
cause. Colitis, cancer, polyps and angiodysplasia
account for the majority of the rest. Most lower
GI bleeding stops spontaneously and in those
cases an elective colonoscopy with standard bowel
Do not place tattoo below 20cm
but clearly record distance of
LESION from anal verge
preparation is appropriate. In the uncommon case
of continued bleeding, a rapid purge to allow
endoscopic therapy can be considered to decrease
both the recurrence of bleeding and the need for
surgical intervention.61 Surgery is reserved for cases
of recurrent, uncontrolled or massive bleeding.
Colonic decompression
The three main causes of bowel obstruction are
cancer, diverticular disease and sigmoid volvulus.
Flexible sigmoidoscopy with placement of a
decompression tube is the initial treatment of choice
for a volvulus. It has a high initial success rate (78%)
but is only a temporising measure as recurrence
is common and elective surgery is therefore still
considered the definitive treatment. Emergency
to lesion as possible but
separate from it
22
Downloaded for Anonymous User (n/a) at Rutgers University - NERL from ClinicalKey.com by Elsevier on March 22, 2019.
For personal use only. No other uses without permission. Copyright ©2019. Elsevier Inc. All rights reserved.
Colonoscopy and flexible sigmoidoscopy
surgery is reserved for a volvulus unresponsive
to endoscopic therapy or for patients with bowel
ischaemia or peritonitis.
Acute colonic pseudo-obstruction (Ogilvie's
syndrome) may mimic the signs and symptoms
of bowel obstruction. It may be initially treated
conservatively with removal of any triggering factors,
mobilisation and the use of a parasympathomimetic
agent such as neostigmine (if not contraindicated). If
this approach fails, then endoscopic placement of a
decompression tube is generally accepted as the first
invasive therapeutic manoeuvre. Emergency surgery
is again only indicated in resistant or complicated
cases, such as those with perforation or ischaemia.
Advanced therapy
Endoscopic submucosal dissection (ESD)
ESD is a technique that has been developed for ‘en
bloc’ resection of large lesions in the gastrointestinal
tract. A deep, submucosal lift is created using a
viscous solution such as sodium hyaluronate or
10% glycerine. Mucosal and submucosal incisions
are made using a modified needle knife to dissect
the mucosa from the submucosa. A transparent
hood is attached to the endoscope tip to help retract
tissue and maintain the submucosal field of view.
The benefit of this technique is that it produces
excellent specimens for histological analysis, but
the technique itself is difficult, and success depends
on excellent endoscopic and haemostatic skills. It is
also quite time-consuming, usually taking between
2 and 3 hours in expert hands, and should be
performed only when surgical backup is available.
It does achieve a higher rate of en bloc and R0
resection compared to EMR, at the cost of a higher
risk of complications.
Stricture dilatation and stenting
The dilatation of colonic strictures is generally
reserved for benign disease, whereas the use of selfexpandable metal stents (SEMS) is usually indicated
for malignant disease.
Through-the-scope (TTS) balloon dilators have
been used in the management of strictures associated
with inflammatory bowel disease, non-steroidal
anti-inflammatory drug (NSAID)-induced colonic
strictures and anastomotic strictures. Success rates
vary, with recent studies suggesting short-term relief in
70–100%, but with frequent recurrence. Complication
rates are significant, with a risk of perforation of 2%
and bleeding between 4% and 11%.
SEMS are usually inserted through the scope and
can be deployed as far as the proximal ascending
colon. Preoperative stenting of malignant strictures
can, in carefully selected cases, allow for onestage surgical procedures, but are mostly used
62
63
for palliation, with patency established up to a
year. SEMS can also be considered as a potential
therapy for selected benign strictures and has been
reported with anastomotic strictures unresponsive
to dilatation, Crohn's disease, diverticular disease
and radiation-induced strictures.
Novel therapies
As technology and endoscopic skill evolve, the
lines between what is possible endoscopically,
laparoscopically and traditionally have become
increasingly blurred. Although initial interest in Natural
Orifice Transluminal Endoscopic Surgery (NOTES)
was high, most studies have concluded that the
standard laparoscopic techniques are quicker and safer.
However, enthusiasts continue to innovate. A novel
trans-anal endo-surgical approach to large, complex
rectal polyps (TASER) may allow for minimally
invasive management of polyps that were previously
destined for surgery.64 Endoscopic full-thickness
resection (EFTR) techniques are being developed that
may allow for wider oncological resection, although
new platforms and prospective clinical trials are
required before they are taken up in routine clinical
practice.65 Balloon-assisted colonoscopy can be used
to provide a stable platform for advanced endoscopic
therapy and may enable access in cases that were
previously incomplete due to technical difficulties.
Competing technologies
Currently, optical colonoscopy remains the goldstandard test for examination of the colon due
to its relatively high pathology detection rate and
the ability to perform therapy. However, newer
techniques are emerging that may be considered
as ‘disruptive technologies’ that will undoubtedly
change the current position.
Computed tomography
colonography (or virtual
colonoscopy)
Computed tomography colonography (CTC),
also known as virtual colonoscopy (VC; or ‘CT
pneumocolon’), is now an established technique for
detecting colon cancer and colonic polyps. It comprises
two low-dose CT scans of the abdomen and pelvis,
and is less invasive than optical colonoscopy, requires
no conscious sedation and is better tolerated by
patients. The diagnostic performance characteristics are
potentially comparable to expert optical colonoscopy
with sensitivity for detecting large polyps (>10 mm
in maximal diameter) exceeding 90% and 96% for
Downloaded for Anonymous User (n/a) at Rutgers University - NERL from ClinicalKey.com by Elsevier on March 22, 2019.
For personal use only. No other uses without permission. Copyright ©2019. Elsevier Inc. All rights reserved.
23
Chapter 2
cancer,66 but it lacks the facility for mucosal biopsy or
polyp removal. It has, however, now superseded barium
enema as the radiological test of choice for the colon.
Self-propelling colonoscopes
One disadvantage of traditional optical colonoscopy
is the prolonged training required for expertise.
There would be significant advantages to providing
the same examination and potential for therapy
without the need for an experienced operator.
A number of self-propelling or self-navigating
colonoscopes have been developed, but these
have not been widely adopted despite initial tests
showing them to be safe and effective. The current
trend is clearly towards greater quality and accuracy
of traditional colonoscopy performance, rather than
widespread adoption of new technology.
Colon capsule
Wireless capsule endoscopy (WCE) is a safe,
minimally invasive, non-sedation requiring, patientfriendly modality to visualise the bowel, and is now
Key points
considered first line for investigation of small bowel
disease. The development of the PillCam colon
capsule (Given Imaging Ltd, Yoqneam, Israel) aims
to widen the application to investigation of colonic
disease. It is attractive for similar reasons and, unlike
optical colonoscopy, only requires expertise in image
interpretation. The second-generation PillCam
Colon Capsule 2 has a wider field of view and
adaptive frame rate than the first-generation, and a
meta-analysis has demonstrated high specificity for
polyps over 10 mm in a screening setting.
67
Conclusions
This chapter has given an overview of the role
of flexible sigmoidoscopy and colonoscopy
in the diagnosis, treatment and prevention of
colorectal disease. Traditional optical endoscopy
is becoming more refined and new technologies
are emerging that will impact on the need for open
or laparoscopic surgery. The current focus is on
quality assurance and improvements in training
with continual skill development essential for
all those endoscopists wishing to perform highquality, safe endoscopy.
• Good technique is vital for high-quality safe endoscopy.
• Sedation practice should be standardised and use the minimum amount of drug required for patient
comfort.
• Withdrawal times should be in excess of 6 minutes in normal colonoscopies.
• Advanced imaging techniques are now becoming more widely available and may impact on current
practice.
• All endoscopists should be familiar with basic therapeutic techniques (polypectomy, diathermy,
decompression) and indications for referral for advanced therapy (EMR, ESD, stenting).
• Competing technologies are evolving and need to be evaluated for their utility in clinical practice.
• Performance in technical skills should be considered in conjunction with non-technical skills and
team working.
Video resources:
• http://www.stmarksacademicinstitute.org.uk/resources/
colonoscopy-insertion-steering-and-examination/
• http://www.stmarksacademicinstitute.org.uk/
resources/colonoscopy-experts-in-action-part-1/
• http://www.stmarksacademicinstitute.org.uk/
resources/colonoscopy-experts-in-action-part-2/
• http://www.stmarksacademicinstitute.org.uk/
resources/colonoscopy-equipment-and-accessories/
• http://www.stmarksacademicinstitute.org.uk/
resources/olympus-scopeguide-3d-imager/
• http://www.stmarksacademicinstitute.org.uk/
resources/polypectomy-training-polypectomy-in-detail/
Full references available at http://expertconsult.
inkling.com
Key references
14. Rizk MK, Sawhney MS, Cohen J, et al. Quality
indicators common to all GI endoscopic procedures.
Gastrointest Endosc 2015;81(1):3–16. PMID:
25480102.
15. Barclay RL, Vicari JJ, Doughty AS, et al.
Colonoscopic withdrawal times and adenoma
detection during screening colonoscopy. N Engl J
Med 2006;355(24):2533–41. PMID: 17167136.
24
Downloaded for Anonymous User (n/a) at Rutgers University - NERL from ClinicalKey.com by Elsevier on March 22, 2019.
For personal use only. No other uses without permission. Copyright ©2019. Elsevier Inc. All rights reserved.
Colonoscopy and flexible sigmoidoscopy
Observational study of 12 experienced colonoscopists
over 7882 colonoscopies showing a 10-fold difference
in ADR between endoscopists and a significant
difference in those who spent more or less than 6
minutes during withdrawal in normal colonoscopies.
19. ASGE Standards of Practice Committee. Bowel
preparation before colonoscopy. Gastrointest
Endosc 2015;81(4):781–94. PMID: 25595062.
20. Connor A, Tolan D, Hughes S, et al. Consensus
guidelines for the safe prescription and administration
of oral bowel-cleansing agents. Gut 2012;61(11):
1525–32. PMID: 22842619.
43. HurlstoneDP, SandersDS, McAlindonME, etal. Highmagnification chromoscopic colonoscopy in ulcerative
colitis: a valid tool for in vivo optical biopsy and
assessment of disease extent. Endoscopy 2006;38(12):
1213–7. PMID: 17163321.
Biphasic examination with 1800 images from 300
patients obtained via conventional or magnification
imaging. Magnification imaging was significantly better
than conventional colonoscopy for predicting disease
extent invivo (P < 0.0001).
44. Kiesslich R, Fritsch J, Holtmann M, et al.
Methylene blue-aided chromoendoscopy for the
detection of intraepithelial neoplasia and colon
cancer in ulcerative colitis. Gastroenterology
2003;124(4):880–8. PMID: 12671882.
Randomised controlled trial of 165 patients showing a
significantly better correlation between the endoscopic
assessment of degree (P = 0.0002) and extent (89%
vs 52%; P <0.0001) of colonic inflammation and the
histopathological findings in the chromoendoscopy
group compared with the conventional colonoscopy
group. More targeted biopsies were possible and
significantly more neoplasias were detected (32 vs 10;
P = 0.003).
45. Rutter MD, Saunders BP, Schofield G, et al.
Pancolonic indigo carmine dye spraying for the
detection of dysplasia in ulcerative colitis. Gut
2004;53(2):256–60. PMID: 14724160.
Back-to-back colonoscopies in 100 patients
showing significantly more dysplasia detection with
chromoendoscopy and targeted biopsies (P = 0.02).
Chromoendoscopy required fewer biopsies (157 vs
2904) yet detected nine dysplastic lesions, seven of
which were only visible after indigo carmine application.
46. HurlstoneDP, KarajehM, CrossSS, etal. The role
of high-magnification-chromoscopic colonoscopy
in hereditary nonpolyposis colorectal cancer
screening: a prospective ‘back-to-back’ endoscopic
study. Am J Gastroenterol 2005;100(10):2167–73.
PMID: 16181364.
Back-to-back colonoscopies in 25 asymptomatic
HNPCC patients. Pan-chromoscopy identified
significantly more adenomas than conventional
colonoscopy (P = 0.001) and a significantly higher
number of flat adenomas (P = 0.004).
59. BrookerJC, SaundersBP, ShahSG, etal. Treatment
with argon plasma coagulation reduces recurrence
after piecemeal resection of large sessile colonic
polyps: a randomized trial and recommendations.
Gastrointest Endosc 2002;55(3):371–5. PMID:
11868011.
Patients with apparent complete excision of
adenomatous polyps were randomised to application
of APC to the margins or not. Postpolypectomy
application of APC reduced recurrence at 3 months
(1/10 APC, 7/11 no APC; P = 0.02).
Downloaded for Anonymous User (n/a) at Rutgers University - NERL from ClinicalKey.com by Elsevier on March 22, 2019.
For personal use only. No other uses without permission. Copyright ©2019. Elsevier Inc. All rights reserved.
25
3
3
Colorectal cancer
Robert J.C. Steele
Introduction
Colorectal cancer is a major health problem. In
the UK, it is the second most common cause of
cancer death, accounting for some 16 000 deaths
in 2014. In 2013 there were approximately 41 000
new cases, of which about 15 000 were rectal and
26 000 colonic.1 The overall numbers in men are
higher than in women, and this is more pronounced
in the rectum than in the colon. The 5-year relative
survival rate is currently in the region of 57% and
has improved over the last 30years from a figure of
around 20% in 1971–75.
Surprisingly, there is no precise definition of the
colon and the rectum. Although the colon comprises
the large bowel proximal to the rectum, the
definition of the rectum is unclear. Anatomical texts
describe the top of the rectum as the point where
the sigmoid mesocolon ends or that part of the large
bowel level with the third sacral vertebra.2 Surgeons,
on the other hand, prefer to think of the rectum as
the segment of large bowel lying within the true
pelvis. As far as rectal cancer is concerned, the UK
definition is a tumour within 15 cm of the anal verge
on rigid sigmoidoscopy,3 whereas authorities from
the USA have preferred 11 or 12 cm.4 Perhaps the
simplest definition is the intraoperative identification
of the fusion of the two antemesenteric taenia into
an amorphous area where the true rectum begins.
These distinctions are important for two
reasons. First, radiotherapy is not appropriate
for colonic tumours and, secondly, comparisons
between outcomes for colorectal cancer surgery
are impossible unless uniform definitions are
adopted. This problem has yet to be addressed by
international consensus.
1
Natural history
Within the large bowel, about 50% of cancers arise
in the rectum and left colon and 25% in the right
(Fig.3.1); in 4–5% of cases there are synchronous
lesions. It is now widely accepted that the majority
of colorectal cancers arise from pre-existing
adenomatous polyps, the supporting evidence being
as follows:
1. The prevalence of adenomas correlates well
with that of carcinomas, the average age of
adenoma patients being around 5years younger
than patients with carcinomas.
2. Adenomatous tissue often accompanies cancer,
and it is unusual to find small cancers with no
contiguous adenomatous tissue.
3. Most sporadic adenomas are identical
histologically to the adenomas of familial
adenomatous polyposis (FAP), and this
condition is unequivocally premalignant.
4. Large adenomas are more likely to display
cellular atypia and genetic abnormalities than
small lesions.
5. The distribution of adenomas throughout the
large bowel is similar to that of carcinomas.
6. Adenomas are found in up to one-third of
all surgical specimens resected for colorectal
cancer.
7. The incidence of colorectal cancer has been
shown to fall with a long-term screening
programme involving colonoscopy and
polypectomy.
5
26
Downloaded for Anonymous User (n/a) at Rutgers University - NERL from ClinicalKey.com by Elsevier on March 22, 2019.
For personal use only. No other uses without permission. Copyright ©2019. Elsevier Inc. All rights reserved.
3%
4%
Colorectal cancer
In a retroperitoneal colonic cancer, radial spread may
involve the ureter, duodenum and muscles of the
posterior abdominal wall; the intraperitoneal tumour
may involve small intestine, stomach, pelvic organs
or the anterior abdominal wall. Rectal tumours may
involve the pelvic organs or side walls.
3%
7%
14%
37%
Figure3.1 • Frequency of anatomical locations of
colorectal cancer.
Based on data from The Wales-Trent Bowel Cancer
Audit, 1993
Although the majority of adenomas diagnosed
in the West are polypoid or exophytic, the flat
adenoma, defined as an adenoma where the depth
of the dysplastic tissue is no more than twice that
of the mucosa, is now a recognised entity. These are
difficult to find, but may account for up to 40% of
all adenomas. In addition, the serrated lesion, which
is histologically distinct from the adenoma and
related to the hyperplastic polyp, is now recognised
as a premalignant condition, particularly on the right
side of the colon.6 Reliable diagnosis of these subtle
lesions requires a skilful, experienced colonoscopist
and the use of dye sprayed on to the colonic mucosa
to highlight the contours of the abnormal tissue.
When invasion has taken place, colonic cancer can
spread directly and via the lymphatic, blood and
transcoelomic routes.
5%
27%
Direct spread
Lymphatic spread
In general, the lymphatic spread of colonic cancer
progresses from the paracolic nodes along the main
colonic vessels to the nodes associated with either
cephalad or caudal vessels, eventually reaching
the para-aortic glands in advanced disease. This
orderly process does not always occur, however,
and in about 30% of cases nodal involvement can
skip a tier of glands.7 In contrast to rectal disease,
it is rare for a colonic cancer that has not breached
the muscle wall to exhibit lymph node metastases7
(overall, about 15% of cases confined to the bowel
wall will be found to have lymph node metastases).
In the rectum, drainage is via the mesorectal nodes.
Blood-borne spread
The most common site for blood-borne spread of
colorectal cancer is the liver, presumably arriving
by the portal venous system. Up to 37% of patients
may have occult liver metastases at the time of
operation, and around 50% of patients may be
expected to develop overt disease at some time. The
lung is the next most common site, with around
10% of patients developing lung metastases at some
stage; other reported sites include ovary, adrenal,
bone, brain and kidney.
Transcoelomic spread
Colonic cancer may spread throughout the
peritoneum, either via the subperitoneal lymphatics
or by virtue of viable cells being shed from the
serosal surface of a tumour, giving rise to malignant
ascites, which is relatively rare.
Aetiology
Knowledge of molecular genetics in sporadic
colorectal cancer has increased rapidly in recent
years, but the stimuli that lead to these carcinogenic
changes are still obscure.
Direct spread occurs longitudinally, transversely and
radially, but as adequate proximal and distal clearance
is technically feasible in the majority of colorectal
cancers, it is radial spread that is of most importance.
Downloaded for Anonymous User (n/a) at Rutgers University - NERL from ClinicalKey.com by Elsevier on March 22, 2019.
For personal use only. No other uses without permission. Copyright ©2019. Elsevier Inc. All rights reserved.
Genetic factors
The predisposing genetic factors and molecular
changes underlying colorectal cancer have been
27
Chapter 3
widely studied, and are dealt with in detail in
Chapter4. In summary, the most commonly inherited
forms of colorectal cancer are Lynch syndrome,
caused by mutations to the DNA mismatch repair
genes, and familial adenomatous polyposis (FAP),
caused by germline mutations in the APC gene.
However, any family history can confer a degree
of risk, which is presumably accounted for by a
combination of shared environmental factors and
inherited genetic polymorphisms. In all colorectal
cancers, there appear to be two main pathways to
carcinogenesis – chromosomal and microsatellite
instability – but more refined methods of classifying
the molecular pathways have recently been
developed that are consistent with this concept.
8
Diet and lifestyle
In 2007, the World Cancer Research Fund (WCRF)
published its report on Food, Nutrition, Physical
Activity and the Prevention of Cancer based on a
systematic review of the world literature.
With respect to colorectal cancer,9 evidence
for decreased risk was found for physical exercise,
dietary bre, calcium, garlic, non-starchy vegetables
and pulses. Evidence for increased risk was
uncovered for obesity, red meat, processed meat,
alcohol, animal fat and sugar. It is clear that being
overweight and underactive stand out as major risk
factors, and governments worldwide have recognised
this as an area for action. Smoking is also important
and long-term smoking is associated with relative
risks of between 1.5 and 3.0.
10
9
Predisposing conditions
Long-standing inflammatory bowel disease, both
ulcerative colitis and Crohn's disease, increases
the risk of colorectal cancer. Previous gastric
surgery has also been implicated, and although the
association is controversial, the risk may be about
twofold. Altered bile acid metabolism may play a
role in this process, both after gastrectomy and after
vagotomy. The risk after ureterosigmoidostomy is
well established, although this operation has now
been largely superseded by the use of an isolated
ileal conduit for urinary diversion.
Presentation
Colorectal cancer can present as an emergency or with
chronic symptoms that are well recognised. Rightsided cancer typically presents with anaemia, as the
liquid nature of the faeces and the wider diameter of
the colon make obstructive symptoms unusual. When
the tumour is situated in the descending or sigmoid
colon, change of bowel habit, colicky abdominal pain
and blood in the stool are the commonest symptoms.
In the rectum, bleeding is predominant, and with a
large tumour, tenesmus is common. Occasionally,
the patient may notice the primary tumour as a mass
and even more rarely a sigmoid cancer may cause
pneumaturia and urinary infection by fistulation into
the bladder, or a gastrocolic fistula may cause faecal
vomiting or severe diarrhoea.
Unfortunately, many of the symptoms of colorectal
cancer are common and non-specific, and although
there have been sustained public awareness
campaigns in the UK to increase the number of
patients consulting their GPs for these symptoms,
this has had the unfortunate effect of greatly
increasing the number of patients being investigated
with no effect on the stage at diagnosis. Guidelines
have been developed to classify those at high risk
warranting urgent investigation based on change in
bowel habit, rectal bleeding in the absence of anal
symptoms, palpable abdominal or rectal masses
and anaemia (Box3.1).11 These guidelines are not
Box3.1 • UK Department of Health criteria for high and
low risk of colorectal cancer
Higher risk
• Rectal bleeding with a change in bowel habit to looser
stools or increased frequency of defecation persisting for
6weeks (all ages)
• Change in bowel habit as above without rectal bleeding
and persisting for 6weeks (>60 years)
• Persistent rectal bleeding without anal symptoms*
(>60 years)
• Palpable right-sided abdominal mass (all ages)
• Palpable rectal mass (not pelvic) (all ages)
• Unexplained iron deficiency anaemia (all ages)
Low risk
• Patients with no iron deficiency anaemia, no palpable
rectal or abdominal mass
• Rectal bleeding with anal symptoms and no persistent
change in bowel habit (all ages)
• Rectal bleeding with an obvious external cause, e.g. anal
fissure (all ages)
• Change in bowel habit without rectal bleeding
(<60 years)
• Transient changes in bowel habit, particularly to harder
or decreased frequency of defecation
• Abdominal pain as a single symptom without signs and
symptoms of intestinal obstruction (all ages)
* Soreness, discomfort, itching, lumps, prolapse or pain.
Reproduced from Thompson MR, Heath I, Ellis BG, etal.
Identifying and managing patients at low risk of bowel cancer in
general practice. Br Med J 2003; 327:263–5. With permission
from BMJ Publishing Group Ltd.
28
Downloaded for Anonymous User (n/a) at Rutgers University - NERL from ClinicalKey.com by Elsevier on March 22, 2019.
For personal use only. No other uses without permission. Copyright ©2019. Elsevier Inc. All rights reserved.
Colorectal cancer
particularly discriminatory, however, and there
is currently great interest in developing the role
of sensitive faecal immunochemical testing (FIT)
for haemoglobin to assist in determining which
symptomatic patients warrant colonoscopy.
Investigation
Currently, the main investigative techniques
include sigmoidoscopy, colonoscopy and computed
tomography (CT) colonography. Barium enema,
formerly the mainstay of investigation, has fallen
out of favour owing to false-positive and falsenegative results occurring in up to 1% and 7% of
cases, respectively, with errors usually occurring in
the sigmoid colon and caecum.
Although rigid sigmoidoscopy may provide
satisfactory rectal visualisation, it has been
largely superseded by flexible sigmoidoscopy
for examination of the rectum and distal colon.
The extent to which the colon can be examined
by this means is highly variable, however, and it
can be argued that colonoscopy should be the
investigation of choice. However, it does carry a risk
of perforation, and even in good hands failure to
achieve caecal intubation can be expected in around
5% of cases. In addition, precise localisation of a
tumour seen at colonoscopy is difficult as the only
reliable landmarks are the anus and the terminal
ileum, although the use of magnetic scope guides
allows more accurate estimation of the site of a
lesion.
CT as a primary investigative modality is now
coming to the fore with the widespread introduction of
CT colonography or ‘virtual colonoscopy’, which is
effective in detecting polypoid lesions down to 6 mm
in diameter and superior to barium enema for the
detection of cancers and signicant polyps.
This is fast becoming a standard investigation and
has replaced the barium enema as the radiological
investigation of choice in the majority of centres.
Capsule endoscopy, until recently used only to
visualise the small bowel, has now been modified
to allow examination of the large bowel, and may
become a very important tool in the investigation
of colorectal symptoms and in screening and
surveillance.
When the diagnosis has been made, staging
of the primary tumour, liver and lungs is now
considered mandatory in the majority of cases.
A fit patient with metastatic disease may be
suitable for active treatment, whereas an elderly
patient with a relatively asymptomatic primary
and evidence of widespread dissemination may
escape resection.
12
13
CT of the chest and abdomen is now regarded as
the staging modality of choice, supplanting chest
X-ray and ultrasound. In a patient with a rectal
cancer, MRI of the rectum is now considered
mandatory to allow accurate preoperative staging
and treatment planning. Endorectal ultrasound is
used in some centres to assist with the assessment
of early rectal cancer as it is reasonably accurate in
distinguishing T1 from T2 tumours, but it is highly
operator-dependent and not universally employed.
PET-CT scanning has a limited role, but is
recommended when surgical resection of metastases
is being considered in order to exclude occult
14
disease.
Screening
Colorectal cancer is a suitable candidate for
screening. Prognosis after treatment is much better
in early stage disease and the polyp–carcinoma
sequence offers an opportunity to prevent cancer by
treating premalignant disease. The ideal screening
test should detect the majority of tumours without
a large number of false positives, i.e. it should have
high sensitivity and specificity. In addition, it must
be safe and acceptable to the population offered
screening. In colorectal cancer, the most widely
studied test is Haemoccult, a guaiac-based test that
detects the peroxidase-like activity of haematin
in faeces. Because this activity is diminished as
haemoglobin travels through the gastrointestinal
tract,15 upper gastrointestinal bleeding is less likely
to be detected than colonic bleeding. On the other
hand, false-positive results may be produced by
ingestion of animal haemoglobin or vegetables
containing peroxidase, and because of the
intermittent nature of bleeding from tumours, the
sensitivity of Haemoccult is only about 50–70%.
Screen-detected tumours are much more likely
to be at an early stage than symptomatic disease,
but this does not prove that screening is beneficial.
Even improved survival in patients whose tumours
are detected by screening is not conclusive because
of the biases inherent in screening. These biases are
threefold, and comprise selection bias, length bias
and lead-time bias.
Selection bias arises from the tendency of people
who accept screening to be particularly health
conscious and therefore atypical of the population
as a whole. Length bias indicates the tendency for
screening to detect a disproportionate number of
cancers that are slow growing, and thereby have
a good prognosis. Lead-time bias results from the
time between the date of detection of a cancer by
screening and the date when it would have been
diagnosed had the subject not been screened. As
survival is measured from the time of diagnosis,
16
Downloaded for Anonymous User (n/a) at Rutgers University - NERL from ClinicalKey.com by Elsevier on March 22, 2019.
For personal use only. No other uses without permission. Copyright ©2019. Elsevier Inc. All rights reserved.
29
Chapter 3
screening advances the date at which diagnosis is
made, thus lengthening the survival time without
necessarily altering the date of death.
Because of these biases, effectiveness can be
assessed only by comparing disease-specic
mortality in a population offered screening with that in
an identical population not offered screening. This
has to be done in the context of a well-designed
randomised controlled trial, and for colorectal cancer
three trials using faecal occult blood (FOB) have
reported mortality data.
carried out in Minnesota,17 and showed a signicant
33% reduction in colorectal cancer-specic mor tality
with annual FOB testing and a signicant 21%
reduction in a group offered biennial screening. In
Nottingham, a trial of biennial FOB testing
demonstrated a 15% reduction in cumulative
mortality18 and an almost identical study carried out
in Funen, Denmark, showed an 18% reduction in
mortality.
19
17–19
The rst of these was
There seems little doubt that FOB screening
can reduce mortality from colorectal cancer,
when applied to unselected populations, and the
challenges for the future are to increase uptake
and to improve the sensitivity and specificity of the
screening test. Worldwide there is increasing interest
in using faecal immunological testing (FIT) for
blood, which is not affected by dietary peroxidase or
animal haemoglobin and is therefore more accurate
than the indirect guaiac test.20 It is also associated
with higher uptake, as, unlike the guaiac test, only
one sample is required, and the collection device
is more hygienic. Of particular interest is the use
of quantitative FIT, which is automated (Fig. 3.2),
and therefore not subject to human observational
error, and provides the user with the facility to set
the performance characteristics to suit the screening
programme.
Another approach is to use endoscopy as a
primary screening test. As 70% of cancers and large
adenomas are found in the distal 60 cm of the large
bowel, flexible sigmoidoscopy has been proposed as
a screening test, and there is good evidence that it is
more sensitive than FOB testing.
Once-only exible sigmoidoscopy between the
ages of 55 and 64 has been investigated as a
screening modality in a multicentre randomised
study,21 and has been shown to reduce colorectal
cancer mortality and incidence, particularly in the
rectum and left colon; the incidence reduction is
undoubtedly due to adenoma removal at the time of
exible sigmoidoscopy. In the UK, exible
sigmoidoscopy is being introduced as part of the
national bowel screening programme, and the guaiac
test is being replaced by FIT.
Surveillance after adenoma
detection
Surveillance of patients diagnosed as having
adenomatous polyps poses a significant challenge
in terms of the use of colonoscopy resources,
particularly with the introduction of population
screening. For this reason, guidelines have been
developed that classify patients as being at low,
intermediate or high risk for adenoma recurrence.22
The low-risk category includes those with one or
two adenomas less than 1 cm in diameter, and either
no follow-up or a repeat colonoscopy at 5 years
is recommended. For those at intermediate risk,
defined as three to four adenomas or at least one
adenoma greater than 1 cm in diameter, colonoscopy
at 3years is recommended. High-risk patients, those
with five or more small adenomas or three or more
where at least one is greater than 1 cm in diameter,
should have another colonoscopy at 1year. While
the evidence upon which these guidelines is based is
not very strong, they represent a sensible approach,
and one that has been adopted widely in the UK.
The malignant polyp
After colonoscopic polypectomy, subsequent
histological examination of the specimen may
reveal a focus of invasive cancer (Fig. 3.3). A
relatively rare situation in the past, this has
rapidly become a common occurrence with the
introduction of colorectal population screening
Figure3.2 • A quantitative faecal immunochemical test
(FIT) analyser.
30
Downloaded for Anonymous User (n/a) at Rutgers University - NERL from ClinicalKey.com by Elsevier on March 22, 2019.
For personal use only. No other uses without permission. Copyright ©2019. Elsevier Inc. All rights reserved.
and it poses the problem of what to do next.
Clearly, if there is a risk of residual tumour, either
Соседние файлы в папке Библиотека им академика М.И. Перельмана