Dr. Ahmed Saleem
FICMS
TUCOM / 4th Year
THE SMALL AND LARGE INTESTINES
Anatomy
Small intestine
The length of the small bowel may vary from 300 to 850 cm between the duodenojejunal (DJ)
flexure to the ileocecal valve.
The jejunum tends to have a wider diameter and a thicker wall, with more prominent mucosal
folds (valvulae conniventes).
The ileum has a thicker, more fatty mesentery with more complex arterial arcades. The ileum
also contains larger aggregates of lymph nodes (Peyer’s patches), which can occasionally
become lead points in intussusception in childhood.
Large intestine
The large intestine begins at the ileocecal valve and extends to the anus. It is approximately 1.5
m long.
The large intestine is less mobile than the small bowel as the ascending and descending colon
are fixed to the retroperitoneum. The colon is also distinguished by having fat-filled peritoneal
tags known as appendices epiploicae and the presence of taeniae. The taenia coli are three flat
bands of longitudinal muscle that run the length of the large intestine from the appendix base to
the rectosigmoid junction and they act to pull the colon into its typical sacculated state,
producing a series of haustrations.
Physiology
Small intestine
The jejunum is the principal site for digestion and absorption of fluid, electrolytes, iron, folate, fat,
protein and carbohydrate, but the absorption of bile salts and vitamin B12 occurs in the terminal
ileum where there are specific transporters. If the jejunum is resected, the ileum can assume all the
required absorptive functions, but resection of the terminal ileum will result in a diminished bile salt
pool, B12 deficiency and may lead to deficiency of the fat-soluble vitamins A, D and K.
Large intestine
The principal function of the colon is absorption of water; 1000 mL of ileal contents enter the cecum
every 24 hours of which only about 150–250 mL is excreted as feces. Fermentation of dietary fiber in
the colon by the normal colonic microflora leads to the generation of short chain fatty acids (SCFAs)
such as butyrate, which is an important metabolic fuel for the colonic mucosa and may also
contribute to normal daily energy requirements.
Inflammatory Bowel Disease
By definition, the term ‘inflammatory bowel disease’ is reserved for conditions characterized by the
presence of idiopathic intestinal inflammation, i.e. ulcerative colitis (UC) and Crohn’s disease (CD). Although
the availability of population genetics and molecular biology has contributed to our understanding of the
pathogenesis of inflammatory bowel disease, the cause of these conditions remains unknown.
Ulcerative Colitis
Ulcerative colitis is a disease of the rectum and colon with extraintestinal manifestations. It is most
commonly diagnosed between the ages of 20 and 40. There is a marked geographical distribution of the
disease which is far more common in the United States and Western Europe, but relatively rare in the Far
East and the Tropics.
Pathological features
Rectum, always involved unless already on topical treatment. Disease spreads proximally with
increasing extent of disease.
Acute neutrophil infiltration of the colonic mucosa and submucosa; mucosal crypt abscesses
with goblet cell mucin depletion.
With more severe inflammation, there are multiple aphthous ulcers, which may become
confluent with only islands of inflamed mucosa and granulation tissue remaining
(pseudopolyposis).
Chronic “burnt-out” disease leads to a pale, featureless, ahaustral pattern to the colon.
Clinical features
Proctitis: Commonest presentation. Symptoms of urgency and frequency of defecation due to
rectal irritability; bloody mucus mixed with loose stools.
Left-sided colitis: Disease up to the splenic flexure. Symptoms of rectal irritation plus extensive
bloody mucus in stools, often leading to bloody diarrhea; mild associated systemic features.
Pancolitis: Disease involving the entire colon. May be associated with mild secondary
inflammation of the terminal ileum (backwash ileitis). Bloody diarrhea predominant feature;
systemic features common (fever, malaise, anorexia, tachycardia). May be associated with
anemia (due to blood loss), hypoalbuminemia, and hypokalemia (due to mucus loss).
Extraintestinal manifestations
Sacroiliitis and ankylosing spondylitis are 20 times more common in patients with UC than the
general population and are associated with HLA-B27. Sclerosing cholangitis is associated with UC
and can progress to cirrhosis and hepatocellular failure. The skin lesions erythema nodosum and
pyoderma gangrenosum normally get better with good colitis control. The eyes can also be affected
with uveitis and episcleritis.
Investigations
Endoscopy: Rigid/flexible sigmoidoscopy can detect proctitis in the outpatient setting.
Colonoscopy and biopsy has a key role in diagnosis and management:
to establish the extent of inflammation.
to distinguish between UC and Crohn’s colitis.
to monitor the response to treatment
to assess long-standing cases for malignant change.
Radiology: A plain abdominal X-ray is valuable in demonstrating the development of toxic
megacolon. Barium enema has been replaced by computed tomography (CT), although a
contrast study will give an excellent view of loss of haustra, especially in the distal colon,
pseudopolyps and in chronic cases a narrow, featureless, shortened ‘hosepipe’ colon. CT findings
in pancolitis may show significant thickening of the colonic wall, as well as inflammatory
stranding in the colonic mesentery.
Bacteriology: A stool specimen should be sent for microbiology analysis when UC is suspected,
in order to exclude infective colitides.
Treatment
Effective treatment of UC requires a multidisciplinary approach to management.
Medical treatment: Principles are to reduce inflammation and prevent complications. Acute
derangements in blood results should be corrected (e.g. blood transfusion for severe anemia,
potassium supplementation, nutritional support for hypoalbuminemia).
Medical therapy is based on anti-inflammatory agents. The 5-aminosalicylic acid (5-ASA)
derivatives can be given topically (per rectum) or systemically. They can be used long term as
maintenance therapy. Corticosteroids are the mainstay of treatment for any ‘flare up’, either
topically or systemically and have a widespread anti-inflammatory action. The
immunosuppressive drugs azathioprine and cyclosporin can be used to maintain remission and
as ‘steroid-sparing’ agents.
Surgical treatment: The greatest likelihood of a patient with UC requiring surgery (colectomy) is
during the first year after diagnosis. Indications for surgery in UC are:
severe or fulminating disease failing to respond to medical therapy.
chronic disease with anemia, frequent stools, urgency and tenesmus.
steroid-dependent disease (remission cannot be maintained without substantial doses of
steroids).
inability of the patient to tolerate medical therapy required to control the disease.
neoplastic change: patients who have severe dysplasia or carcinoma on review colonoscopy.
extraintestinal manifestations.
rarely, severe hemorrhage or stenosis causing obstruction.
Complications
Acute
Acute fulminant colitis and Toxic dilatation: Around 5 per cent of patients present with severe
acute (fulminant) colitis characterized by frequent bloody diarrhea, weight loss and dehydration.
Intensive medical treatment and fluid resuscitation leads to remission in 70 per cent, but the
rest will require urgent surgery. Toxic dilatation should be suspected in patients with active
colitis who develop severe abdominal pain and confirmed by the presence on a plain abdominal
radiograph of colon with a diameter of more than 6 cm.
Perforation
Hemorrhage
Chronic
Cancer: The risk of cancer in ulcerative colitis increases with duration of disease. At ten years
from diagnosis, it is around 1 per cent. This increases to 10–15 per cent at 20 years and may be
as high as 20 per cent at 30 years.
Extra-alimentary manifestations.
Crohn’s Disease (Regional Enteritis)
It is characterized by a chronic full thickness inflammatory process that can affect any part of the
gastrointestinal tract from the lips to the anal margin. It is most common in North America and Northern
Europe It is slightly more common in women than in men, and is most commonly diagnosed in young
patients between the ages of 25 and 40 years. There does, however, seem to be a second peak of incidence
around the age of 70 years.
Pathological features
The terminal ileum is most commonly involved, either in isolation or in combination with colonic
disease. Colitis alone occurs in up to a third of cases and the remainder are patients with more
proximal small bowel involvement. The stomach and duodenum are affected in around 5 per
cent, but perianal lesions are common, affecting up to 50–75 per cent of patients.
CD is characteristically discontinuous, with inflamed areas separated from normal intestine, so-
called ‘skip’ lesions.
Affected bowel looks blue-grey, thickened, with spiral surface vessels and encroachment of the
mesenteric fat around the bowel (fat wrapping).
Transmural inflammation in the form of lymphoid aggregates, particularly in the subserosal
tissues (Crohns rosary), mucosal crypt ulceration, and fissuring ulceration.
Non-caseating giant cell granulomas are found in 60 per cent of patients and clearly define
Crohn’s disease.
Mucosal thickening and serpiginous longitudinal ulceration combine to give the appearance of
cobblestoning.
Perforation, fistulation, and abscess formation are occasional fistulizing sequelae of transmural
inflammation.
Extensive fibrosis and smooth muscle hyperplasia may occur, giving rise to stenosis.
Clinical features
Inflammatory features: Fever, malaise, abdominal pain (often RIF), change in bowel habit
(usually diarrhea without blood), and weight loss. Children and adolescents may have failure to
thrive or have retarded growth. Rectal bleeding is rare except in Crohns colitis.
Fistulizing features: Para-enteric abscess formation often with a tender abdominal mass, fistula
formation (ileocolic, ileoileal, ileocutaneous); rarely free perforation with features of peritonitis.
Stenosing features: Colicky abdominal pain, weight loss due to poor food intake (food fear),
palpable or visible distended small bowel loops.
Anal disease: Atypical severe anal fissures, fistula in ano, anal mucosal thickening, and
discoloration.
Investigations
In acute presentations, an abdominal CT may show an inflammatory mass, abscess formation,
localized or free perforation.
In subacute or chronic presentations, small bowel disease may be shown by a small bowel
contrast study (shows mucosal irregularity and narrowing).
Crohns colitis is diagnosed by endoscopy and biopsy.
Anal disease may require anal ultrasound or MRI scanning for assessment.
OGD and biopsies may show features of Crohns in gastric mucosa.
Treatment
Medical treatment:
Principles are to reduce inflammation and control complications. Acute
derangements in blood results should be corrected.
Systemic (5-ASA) drugs are first-line acute and long-term treatment.
Systemic steroids (hydrocortisone, prednisolone) control acute exacerbations of
inflammation and steroids with very high first pass metabolism (budesonide) can be used
chronically.
Immunosuppressives (azathioprine, 6-mercaptopurine) are used as maintenance therapy
and anti-TNFA antibodies (infliximab) may be effective in fistulizing complications.
Dietary manipulation (elemental diet) may reduce inflammatory factors.
Surgical treatment: Surgical resection will not cure CD. Surgery therefore focuses on the
complications of the disease. Principles are to deal with septic complications, relieve significant
bowel obstruction, and remove as little bowel as possible. Complications of the disease which
are indications for surgery include the following:
recurrent intestinal obstruction
bleeding
perforation
failure of medical therapy
intestinal fistula
fulminant colitis
malignant change
perianal disease.
Infections of the Small and Large Intestine
Intestinal amebiasis
Amebiasis is an infestation with Entameba histolytica. This parasite has a worldwide distribution and is
transmitted mainly in contaminated drinking water. It can cause colonic ulcers, which are described as
‘bottlenecked’ because they have considerably undermined edges. The ulcers typically also have a yellow
necrotic floor, from which blood and pus exude. In the majority of cases, they are confined to the distal
sigmoid colon and the rectum. Clinically amebiasis can mimic UC, most commonly causing bloody diarrhea
but more severe colonic complications can occur, including severe hemorrhage, stricture formation or
perforation. A pericolitis is not uncommon and results in adhesions and may cause intestinal obstruction.
Amebiasis may cause liver abscesses or an amebic mass (ameboma) of the cecum or sigmoid which is
difficult to distinguish from a carcinoma. Surgery is fraught with danger as the bowel is extremely friable.
Endoscopic biopsies or fresh hot stools are examined to look for the presence of amebae. It is especially
important to exclude amebic infection in patients suspected of having UC. Treatment is by metronidazole in
the acute setting, three times daily for 7–10 days. Diloxanide furoate is effective against chronic infections
associated with the passage of cysts in stools.
Typhoid fever
Typhoid fever is caused by S. typhi and presents with fever and abdominal pain after an incubation period
of 10–20 days. Over the next week, the patient can develop distension, diarrhea, splenomegaly and
characteristic ‘rose spots’ on the abdomen caused by a vasculitis. Diagnosis is confirmed by culture of blood
or stool. Treatment is by antibiotics.
Perforation of a typhoid ulcer usually occurs during the third week and is sometimes the first sign of the
disease. The ulcer is parallel to the long axis of the gut and is usually situated in the distal ileum.
Perforation requires surgery to wash out and close the perforated ulcer; resection is usually avoided. In
unstable patients, notably with evidence of septic shock, the bowel should be exteriorized and the
perforation closed after recovery.
Tuberculosis of the intestine
Tuberculosis, like Crohn’s disease, can affect any part of the gastrointestinal tract from the mouth to the
anus. The sites affected most often are the ileum, proximal colon and peritoneum.
There are two principal presentations.
Ulcerative tuberculosis
Ulcerative tuberculosis is secondary to pulmonary tuberculosis and arises as a result of swallowing
tubercle bacilli. Multiple ulcers, lying transversely, develop in the terminal ileum and the overlying
serosa is thickened, reddened and covered in tubercles. Patients typically present with diarrhea and
weight loss, although subacute obstruction and even local perforation and fistula formation can
occur. A barium follow-through or CT examination show absent filling of the lower ileum, caecum
and the ascending colon as a result of narrowing of the ulcerated segment.
A course of chemotherapy (antituberculous antibiotics) usually leads to cure, provided the
pulmonary tuberculosis is adequately treated. Surgery is usually undertaken only in the rare event of
a perforation or complete intestinal obstruction.
Hyperplastic tuberculosis
This is caused by the ingestion of Mycobacterium tuberculosis by patients with a high resistance to
the organism. The infection usually occurs in the ileocaecal region. The infection establishes itself in
lymphoid follicles, and the resulting chronic inflammation causes thickening of the intestinal wall
and narrowing of the lumen. There is early involvement of the regional lymph nodes, which may
caseate. Unlike in Crohn’s disease, abscess and fistula formation is rare. Patients usually present
with attacks of abdominal pain and intermittent diarrhea. There is incomplete ileal obstruction,
leading to stasis and bacterial overgrowth. This in turn causes steatorrhea, anemia and loss of
weight. Patients may present with a mass in the right iliac fossa and vague ill health. The differential
diagnosis is that of an appendix mass, lymphoma, carcinoma of the caecum, CD, tuberculosis or
actinomycosis. A barium follow-through or small bowel enema will show a long narrow filling defect
in the terminal ileum. CT will also demonstrate the narrowed segment with proximal distension and
can also demonstrate the lymphadenopathy. When the diagnosis is certain and the patient has not
yet developed obstructive symptoms, treatment with chemotherapy is advised and may be curative.
Where obstruction is present, surgery with ileocecal resection is often required.
Pseudomembranous colitis
Clostridium difficile is a toxin producing Gram-positive bacillus. Although normally present in around 2 per
cent of the population, it seems to proliferate after antibiotic treatment (especially cephalosporins) and can
cause antibiotic-associated diarrhea and pseudomembranous colitis. Clinically, C. difficile infection presents
with diarrhea, abdominal pain and fever. It may progress to pseudomembranous colitis, so called because
on visualization of the bowel, plaques of inflammatory exudate between edematous mucosa are seen.
Treatment is by metronidazole or vancomycin alongside supportive care. If the colitis does not settle, an
emergency subtotal colectomy and ileostomy may be necessary.
Tumors of the Small Intestine
Small bowel tumors are rare and in total account for less than 10 per cent of gastrointestinal neoplasia.
Benign
The majority of small bowel neoplasms are benign, comprising adenomas, lipomas, hemangiomas
and neurogenic tumors. They are frequently asymptomatic and identified incidentally, but can
present with intussusception, small bowel obstruction and bleeding that may cause anemia or may
even be overt.
Malignant
These are rare and classically present late, most often diagnosed after surgery for small bowel
obstruction. Four types account for over 99 per cent of small bowel malignancies: adenocarcinoma,
carcinoid tumors, lymphomas and mesenchymal tumors (gastrointestinal stromal tumors (GIST)).
Adenocarcinoma
Small bowel adenocarcinoma is more often found in the jejunum than the ileum and though the
etiology is unknown they are more common in patients with Crohn’s disease, coeliac disease and
familial adenomatous polyposis (FAP) and Peutz-Jeghers syndrome. They present with anemia,
overt gastrointestinal bleeding, intussusception or obstruction. Prognosis is poor.
Carcinoid tumor
These neuroendocrine tumors occur throughout the gastrointestinal tract, most commonly in
the appendix, ileum and rectum in decreasing order of frequency. Appendicular carcinoid
tumors are most commonly noted as an incidental finding at appendectomy. Carcinoid tumors
arise from Kulchitsky cells at the base of intestinal crypts (of Lieberkuhn). The tumors can
produce a number of vasoactive peptides, most commonly 5-hydroxytryptamine (serotonin), but
also histamine, prostaglandins and kallikrein. When they metastasize to the liver, the carcinoid
syndrome can become evident, because the vasoactive substances escape the filtering actions of
the liver. The clinical syndrome itself consists of reddish-blue cyanosis, flushing attacks, diarrhea,
borborygmi, asthmatic attacks and, eventually, pulmonary and tricuspid stenosis. Classically, the
flushing attacks are induced by alcohol. Surgical resection is usually sufficient for patients with
primary disease, but the incidence of recurrence is significant. The extent of disease can be
assessed preoperatively using octreotide scanning, which may detect otherwise clinically
apparent primary and secondary tumors. Plasma markers of tumor bulk, such as chromogranin A
concentrations, may be useful markers of disease recurrence, as well as of prognostic value.
In patients with metastatic disease, hepatic resection can be carried out. The treatment has
been transformed by the use of octreotide (a somatostatin analogue), which reduces both
flushing and diarrhea, and octreotide cover is usually used in patients with a carcinoid syndrome
who have surgery to prevent a carcinoid crisis. Carcinoid tumors are not usually sensitive to
chemo- or radiotherapy.
Primary lymphoma
Arise from the lymphoid tissue of the small bowel wall. It is more common in patients with
Crohn’s disease and immunodeficiency syndromes. Almost always non-Hodgkin’s; commonest
are B-cell lymphomas arising from the mucosa-associated lymphoid tissue (MALTomas). Presents
with malaise, abdominal pain, diarrhea; may present with acute perforation or small bowel
obstruction. The mainstay of treatment for these conditions is chemotherapy; however surgery
may be required for obstruction, perforation or bleeding.
Gastrointestinal Stromal Tumors (GISTs)
GISTs arise from interstitial cells of Cajal (ICC) and are distinct from leiomyoma and
leiomyosarcoma, which arise from smooth muscle. Prognosis in patients with GIST tumors
depends mostly on tumor size and mitotic count, and metastasis, when it occurs, is typically by
the hematogenous route. Any lesion >1 cm can behave in a malignant fashion and may recur.
Thus, all GISTs are best resected along with a margin of normal tissue. Almost all GISTs (and
almost no smooth muscle tumors) express c-KIT (CD117) as well as CD34; almost all smooth
muscle tumors (and almost no GISTs) express actin and desmin. These markers can often be
detected on specimens obtained by fine-needle aspiration and are useful in differentiating
between GIST and smooth muscle tumor histopathologically. Lesions that are definitively
leiomyoma by current histopathologic criteria are adequately treated by enucleation. Lesions
that are definitively GIST or leiomyosarcoma are best treated by resection with negative
margins. They occur most commonly in the 50- to 70-year age group. Patients may be
asymptomatic. Symptoms include lethargy, pain, nausea, hematemesis or melena. Surgery is the
most effective way of removing GISTs, as they are radioresistant. Glivec (imatinib) is a tyrosine
kinase inhibitor that has been shown to be effective in advanced cases and may also have an
adjuvant role.
Tumors of the Large Intestine
Colorectal polyps
The term ‘polyp’ is a clinical description of any protrusion of the mucosa. It encompasses a variety of
histologically different tumors. Polyps can occur singly, synchronously in small numbers or as part of a
polyposis syndrome. It is important to be sure of the histological diagnosis because colonic adenomas have
significant malignant potential.
Hyperplastic Polyps
Hyperplastic polyps are extremely common in the colon. These polyps usually are small (<5 mm) and
show histologic characteristics of hyperplasia without any dysplasia. They are not considered
premalignant. In contrast, large hyperplastic polyps (>2 cm) may have a slight risk of malignant
degeneration. Moreover, large polyps may harbor foci of adenomatous tissue and dysplasia.
Hamartomatous Polyps
Juvenile polyp is a bright-red glistening pedunculated sphere (‘cherry tumor’), which is found in
infants and children. Occasionally, it persists into adult life. It can cause bleeding, or pain if it
prolapses during defecation. It often separates itself, but can be removed easily with forceps or
a snare. A solitary juvenile polyp has virtually no tendency to malignant change, but should be
treated if it is causing symptoms
.Familial juvenile polyposis is an autosomal dominant disorder in which patients develop
hundreds of polyps in the colon and rectum. Unlike solitary juvenile polyps, these lesions may
degenerate into adenomas and, eventually, carcinoma. Annual screening should begin between
the ages of 10 and 12 years. Treatment is surgical and depends, in part, upon the degree of
rectal involvement.
Peutz-Jeghers syndrome is an autosomal dominant disease characterized by melanosis of the
mouth and lips and multiple hamartomatous polyps in the small bowel and colon. Melanin spots
can also occur on the digits and perianal skin. It is associated with increased risk of a wide range
of cancers. It is logical to perform regular colonic surveillance and encourage female patients to
attend breast and cervical screening. Malignant change in the polyps rarely occurs and, in
general the polyps can be left alone. Resection may be indicated for heavy and persistent or
recurrent bleeding or intussusception.
Adenomatous polyps
True neoplastic polyps formed by excessive growth of the colorectal epithelium; divided by the
morphology of the glandular tissue into tubular, tubulovillous, and villous types. May be sessile,
pedunculated or mixed. Thought to be the precursor of most colorectal cancers; the risk of
cancerous change within an adenomatous polyp increases with size (particularly >1cm), villous
morphology, and sessile form. Majority are sporadic (either isolated or in small numbers), although
occasionally part of a hereditary syndrome. Solitary adenomas are usually found during the
investigation of colonic symptoms and may be the cause of rectal bleeding. Villous tumors can cause
diarrhea, mucous discharge and, occasionally, hypokalemia and hypoalbuminemia.
* Familial adenomatous polyposis (FAP)
FAP caused by an autosomal dominant defect in the APC gene on chromosome 5 and characterized
by between dozens and thousands of adenomatous polyps in the colorectum and an increased risk
of polyp formation in the stomach and duodenum. The risk of cancerous transformation in any given
polyp is similar to that in normal polyps, but the overall risk is very high due to the vastly increased
number present. Associated with:
• Desmoid formation, particularly in the abdominal tissues.
• Multiple osteomata, fibromata, and thyroid inflammation (called Gardner’s syndrome).
FAP is usually treated by proctocolectomy.
* Hereditary non-polyposis colorectal cancer (HNPCC). Lynch syndrome
This syndrome is characterized by increased risk of colorectal cancer and also cancers of the
endometrium, ovary, stomach and small intestines. It is an autosomal dominant condition that is
caused by a mutation in one of the DNA mismatch repair genes. The most commonly affected genes
are MLH1 and MSH2. The lifetime risk of developing colorectal cancer in Lynch syndrome is 80 per
cent, and the mean age of diagnosis is 45 years. Most cancers develop in the proximal colon.
Females with HNPCC have a 30–50 per cent lifetime risk of developing endometrial cancer. Patients
with HNPCC are subjected to regular colonoscopic surveillance.
Classification of intestinal polyps
Inflammatory
Inflammatory polyps (pseudopolyps in ulcerative colitis)
Metaplastic
Metaplastic or hyperplastic polyps
Harmartomatous
Peutz–Jeghers polyp
Juvenile polyp
Neoplastic
Adenoma
Tubular
Tubulovillous
Villous
Adenocarcinoma
Carcinoid tumor
Colorectal cancer (CRCa)
In the UK, colorectal cancer is the second most common cause of cancer death; but seems to occur less
frequently in the developing world than in industrialized countries.
Pathology
The accepted model of colorectal cancer development is that it arises from adenomatous polyps
after a sequence of genetic mutations influenced by environmental factors (adenoma–
carcinoma sequence)
The predominant type is adenocarcinoma.
Predisposing factors include:
Polyposis syndromes (including FAP, HNPCC, juvenile polyposis).
Strong family history of colorectal carcinoma.
Previous history of polyps or CRCa.
Chronic ulcerative colitis or colonic Crohn’s disease.
Low dietary fibers.
CRCa may occur as a polypoid, ulcerating, stenosing, or infiltrative tumor mass. The majority lie
on the left side of the colon and rectum. Three to five per cent have a synchronous carcinoma at
time of diagnosis.
Clinical features
Rectal location
PR bleeding. Deep red on the surface of stools.
Change in bowel habit. Difficulty with defecation, sensation of incomplete evacuation, and
painful defecation (tenesmus).
Descending-sigmoid location
PR bleeding. Typically dark red, mixed with stool, sometimes clotted.
Change in bowel habit. Typically increased frequency, variable consistency, mucus PR,
bloating, and flatulence.
Right-sided location
Typically present late with iron deficiency anemia or a mass.
Emergency presentations
Up to 40% of colorectal carcinomas will present as emergencies.
Large bowel obstruction (colicky pain, bloating, bowels not open).
Perforation with peritonitis.
Acute PR bleeding.
Diagnosis and investigations
Elective diagnosis by PR examination or rigid sigmoidoscopy for rectal carcinoma. Colonoscopy is
the preferred diagnostic investigation (alternatives are barium enema and CT colonography).
Emergency presentations commonly diagnosed by abdominal CT scan. Single contrast enema
may be used when the diagnosis of large bowel obstruction is possible and CT scanning is
unavailable. Acute PR bleeding is sometimes investigated by urgent colonoscopy.
Staging investigations
Assessment of the presence of metastases (liver, lung, or para-aortic):
Thoracoabdominopelvic CT scanning is gold standard; CT PET scan may be used to evaluate
equivocal lesions.
Assessment of local extent: For colonic carcinoma, CT scanning is adequate; for rectal cancer,
pelvic MRI and transrectal US are commonly used.
Assessment of synchronous tumors: If not diagnosed by colonoscopy or barium enema, one
of these two tests is usually performed to identify synchronous tumors.
Tumor marker (CEA) is of no use for diagnosis or staging, but can be used to monitor disease
relapse if raised at diagnosis and falls to normal after resection.
Dukes’ staging for colorectal cancer
TNM classification for colonic cancer
A , confined to bowel wall only
B , through bowel wall
C , any with +ve lymph nodes
D , any with metastases
T1–4 , stages of tumor invasion of bowel wall
N, Nodal stage
N0, No nodes involved
N1, 1–3 nodes involved
N2, Four or more nodes involved
M, Metastases: M0, No metastases, M1, Metastases
Treatment
Potentially curative treatment
Suitable for technically resectable tumors with no evidence of metastases (or metastases
potentially curable by liver or lung resection).
• Surgical resection (with lymphadenectomy) is the only curative treatment.
• Preoperative (neoadjuvant) chemoradiotherapy may be used to increase the chance of
curative resection.
• Adjuvant chemotherapy (5-FU based) is offered for tumors with positive lymph nodes or
evidence of vascular invasion.
• Hepatic or lung resection may be offered to patients with suitable metastases and a clear
resected/resectable primary tumor.
Palliative treatment
For unresectable metastases or unresectable tumors.
• Chemotherapy may effectively extend life expectancy with a good quality of life.
• Obstructing tumors may be endoluminally stented with self-expanding metal stents or
transanally ablated (e.g. with laser) if rectal.
• Palliative surgery reserved for untreatable obstruction, bleeding, or severe symptoms.
Intestinal Diverticula
Diverticula (hollow out-pouching) are a common structural abnormality that can occur from the esophagus
to the rectosigmoid junction (but not usually in the rectum). They can be classified as:
• Congenital. All three coats of the bowel are present in the wall of the diverticulum, e.g. Meckel’s
diverticulum.
• Acquired. There is no muscularis layer present in the diverticulum, e.g. sigmoid diverticula.
Jejunal diverticula
These arise from the mesenteric side of the bowel as a result of mucosal herniation at the point of entry of
the blood vessels. They can vary in size and are often multiple. They are most often asymptomatic and an
incidental finding at surgery or on radiological imaging; however, they can result in malabsorption, as a
result of bacterial stasis, or present as an acute abdominal emergency if they become inflamed or
perforate. Bleeding from a jejunal diverticulum is a rare complication.
Meckel’s diverticulum
A Meckel’s diverticulum is a persistent remnant of the vitellointestinal duct and is present in about 2 per
cent of the population. It is found on the antimesenteric side of the ileum, commonly at 60 cm from the
ileocecal valve and is classically 5 cm long. A Meckel’s diverticulum contains all three coats of the bowel
wall and has its own blood supply. It is vulnerable to obstruction and inflammation in the same way as the
appendix; indeed, when a normal appendix is found at surgery for suspected appendicitis, a Meckel’s
diverticulum should be looked for by examining the small bowel particularly if free fluid or pus is found. In
around 20 per cent of cases, the mucosa of a Meckel’s diverticulum contains heterotopic epithelium of
gastric, colonic or pancreatic type. A Meckel’s diverticulum can present clinically in the following ways:
Hemorrhage. If heterotopic gastric mucosa is present, peptic ulceration can occur and present as
painless maroon rectal bleeding or melaena. If the stomach, duodenum and colon are cleared by
endoscopy, radioisotope scanning with technetium-99m may demonstrate the heterotopic
tissue in a Meckel’s. (A Meckel’s is notoriously difficult to see with contrast radiology.)
Diverticulitis. Meckel’s diverticulitis presents like appendicitis, although if perforation occurs the
presentation may resemble a perforated duodenal ulcer.
Intussusception. A Meckel’s can be the lead point for ileoileal or ileocolic intussusception.
Chronic ulceration. Pain is felt around the umbilicus, as the site of the diverticulum is midgut in
origin.
Intestinal obstruction. A band between the apex of the diverticulum and the umbilicus (also part
of the vitellointestinal duct) may cause obstruction directly or by a volvulus around it.
Perforation with peritonitis.
The vast majority of Meckel’s are asymptomatic.
When found in the course of abdominal surgery, a Meckel’s can safely be left alone provided it has a wide
mouth and is not thickened. When there is doubt, it can be resected. The finding of a Meckel’s diverticulum
in an inguinal or femoral hernia has been described as Littre’s hernia.
Diverticular disease of the large intestine
Colonic diverticula are acquired outpouchings of colonic mucosa and overlying connective tissue through
the colonic wall. Tend to occur along the lines where the penetrating colonic arteries traverse the colonic
wall between the taenia coli. Associated with hypertrophy of the surrounding colonic muscle with
thickening of the colonic mucosa. This is probably due to the underlying pathological process, which is high
pressure contractions of the colon, causing chronic pressure on the colonic wall. Peak age of presentation is
50–70y. Diverticular disease is rare in Africa and Asia where the diet is high in natural fibers.
Vascular Diseases of the Intestine
Mesenteric ischemia
Mesenteric ischemia can present as one of two distinct clinical syndromes: acute mesenteric ischemia and
chronic mesenteric ischemia.
Acute mesenteric ischemia
Four distinct pathophysiologic mechanisms can lead to acute mesenteric ischemia:
1. Arterial embolus: Embolus is the most common cause of acute mesenteric ischemia. The embolic
source is usually in the heart; most often the left atrial or ventricular thrombi or valvular lesions.
Embolism to the superior mesenteric artery accounts for 50% of cases; most of these emboli
become wedged and cause occlusion at branch points in the mid- to distal superior mesenteric
artery, usually distal to the origin of the middle colic artery.
2. Arterial thrombosis: In contrast, acute occlusions due to thrombosis tend to occur in the proximal
mesenteric arteries, near their origins. Acute thrombosis is usually superimposed on pre-existing
atherosclerotic lesions at these sites.
3. Vasospasm (also known as non-occlusive mesenteric ischemia): is the result of vasospasm and
usually is diagnosed in critically ill patients receiving vasopressor agents.
4. Venous thrombosis: Mesenteric venous thrombosis accounts for 5 to 15% of cases of acute
mesenteric ischemia and involves the superior mesenteric vein in the majority of cases. The inferior
mesenteric vein is only rarely involved. Mesenteric venous thrombosis is classified as primary if no
etiologic factor is identifiable, or as secondary if an etiologic factor, such as heritable or acquired
coagulation disorders, is identified.
Regardless of the pathophysiologic mechanism, acute mesenteric ischemia can lead to intestinal mucosal
sloughing within 3 hours of onset and full-thickness intestinal infarction by 6 hours.
Severe abdominal pain, out of proportion to the degree of tenderness on examination, is the hallmark of
acute mesenteric ischemia, regardless of the pathophysiologic mechanism. The pain typically is perceived to
be colicky and most severe in the mid-abdomen. Associated symptoms can include nausea, vomiting, and
diarrhea. Physical findings are characteristically absent early in the course of ischemia. With the onset of
bowel infarction, abdominal distention, peritonitis, and passage of bloody stools occur.
Chronic mesenteric ischemia
In contrast, chronic mesenteric ischemia develops insidiously, allowing for development of collateral
circulation, and, therefore, rarely leads to intestinal infarction. Chronic mesenteric arterial ischemia results
from atherosclerotic lesions in the main splanchnic arteries (celiac, superior mesenteric, and inferior
mesenteric arteries). A chronic form of mesenteric venous thrombosis can involve the portal or splenic
veins and may lead to portal hypertension, with resulting esophagogastric varices, splenomegaly, and
hypersplenism.
Chronic mesenteric ischemia presents insidiously. Postprandial abdominal pain is the most prevalent
symptom, producing a characteristic aversion to food ("food-fear") and weight loss. These patients are
often thought to have a malignancy and suffer a prolonged period of symptoms before the correct
diagnosis is made.
Angiodysplasia
Vascular lesions of unknown etiology, most frequently found in the right colon, occasionally associated with
cutaneous and oral lesions. They occur with increasing age and present with bleeding that may be
torrential, but more often as a series of small bleeds.
Stomas
A colostomy (or ileostomy) stoma is an artificial opening made in the colon (or small intestine) to divert
feces and flatus outside the abdomen where they can be collected in an external appliance. Depending on
the purpose for which the diversion has been necessary, a stoma may be temporary or permanent.
Temporary or defunctioning stomas are usually fashioned as loop stomas, while end stomas usually as a
result of surgical removal of distal bowel.
Ileostomy: Formed from any part of the mid- or distal small bowel. Ileostomies (loop or end) are usually
spouted, have prominent mucosal folds, tend to be dark pink/red in color, and are most common in the
right side of the abdomen. Ileostomy effluent is usually liquid; patients are more likely to develop fluid and
electrolytes problems.
Colostomy: Formed from any part of the large bowel. Colostomies (loop or end) are usually flush, have flat
mucosal folds, tend to be light pink in color. A colostomy effluent is usually solid and they are most
common in the left side of the abdomen.
Stoma complications
- Skin irritation
- Prolapse
- Retraction
- Ischemia
- Stenosis
- Parastomal hernia
- Bleeding
- Fistulation
Enterocutaneous Fistula
An abnormal connection between small bowel and skin can occur in fistulating Crohn’s disease or as a result
of radiotherapy or abdominal trauma, but most commonly follows a surgical complication – either a leak
from an anastomosis or an inadvertent enterotomy during dissection. This can be very challenging to
manage in patients with a high-output fistula (>500 mL/day). Low-output fistulae (<500 mL/day) can be
expected to heal spontaneously, provided there is no distal obstruction.
Reasons for failure of spontaneous healing also include:
• Epithelial continuity between the gut and the skin.
• The presence of active disease where, for example, there is Crohn’s disease or carcinoma at the
site of the anastomosis or in the fistula track.
• An associated complex abscess.
The management of high output fistulae is based on well-established principles (SNAP), as an early return to
theatre to try and fix the problem in a septic, malnourished patient is doomed to failure.
Principles of management of enterocutaneous fistulae (SNAP)
_ S, elimination of Sepsis and skin protection
_ N, Nutrition – a period of parenteral nutrition may well be required
_ A, Anatomical assessment
_ P, definitive planned surgery
The Rectum
Anatomy
The rectum begins where the tenia coli of the sigmoid colon join to form a continuous outer longitudinal
muscle layer at the level of the sacral promontory. The rectum follows the curve of the sacrum, and ends at
the anorectal junction. The adult rectum is approximately 12–18 cm in length and is conventionally divided
into three equal parts: the upper third, which is mobile and has a peritoneal covering anteriorly and
laterally; the middle third, where the peritoneum covers only the anterior and part of the lateral surfaces;
and the lowest third, which lies deep in the pelvis surrounded by fatty mesorectum and is separated from
adjacent structures by fascial layers.
Injuries
The rectum or anal canal may be injured in a number of ways, all uncommon:
• by falling in a sitting posture onto a pointed object.
• by penetrating injury (including gunshots) to the buttocks.
• by sexual assault.
• by the fetal head during childbirth.
Diagnosis
The anus should be inspected and the abdomen palpated. If rigidity or tenderness is present, early
laparotomy or laparoscopy is indicated.
A water-soluble contrast enema or computed tomography (CT) scan with rectal contrast is useful to
identify perforation.
Prior to the operation, a urethral catheter is passed, but if there is any possibility of urethral injury
(suggested by difficulty passing urine, hematuria or high prostate on digital examination), an
urethrogram should be performed first.
Treatment
If perforation is suspected, the rectum is examined under general anesthetic with a finger and a
sigmoidoscope, particular attention being directed to the anterior wall. If penetrating injury is confirmed,
laparotomy or laparoscopy is then performed.
If an intraperitoneal rupture of the rectum is found, the perforation is closed with sutures. A
defunctioning colostomy is usually required, constructed in the left iliac fossa.
If the rectal injury is below the peritoneal reflection, wide drainage from below is indicated, with
rectal washout and a defunctioning colostomy.
If the defect in the rectum is very large, resection may have to be contemplated, usually in the form
of a Hartmann’s procedure.
Antibiotic cover must be provided against both aerobic and anaerobic organisms.
Prolapse
Rectal prolapse may be partial thickness (usually just mucosa) or full thickness involving all the layers of the
rectal wall.
Mucosal prolapse (partial thickness)
The mucous membrane and submucosa of the rectum protrude outside the anus for approximately 1–4 cm.
When the prolapsed mucosa is palpated between the finger and thumb, it is evident that it is composed of
no more than a double layer of mucous membrane.
In infants
The direct downward course of the rectum, due to the as-yet undeveloped sacral curve, predisposes to this
condition, as does the reduced resting anal tone, which offers diminished support to the mucosal lining of
the anal canal.
In children
Mucosal prolapse often commences after an attack of diarrhea, or from loss of weight and consequent loss
of fat in the ischiorectal fossae. It may also be associated with cystic fibrosis, neurological causes and
maldevelopment of the pelvis.
In adults
The condition in adults is often associated with third-degree hemorrhoids. In the female, a torn perineum,
and in the male straining from urethral obstruction, predispose to mucosal prolapse. In old age, both
mucosal and full-thickness prolapse are associated with weakness of the sphincter mechanism. Partial
prolapse may follow an operation for fistula in ano where a large portion of muscle has been divided. Here,
the prolapse is usually localized to the damaged quadrant and is seldom progressive.
Clinical features
Prolapsed mucous membrane is pink; prolapsed internal hemorrhoids are plum colored and more
pedunculated. Discharge of mucus and small volume fecal staining, pruritus ani, and occasionally small
volume bright red rectal bleeding.
Treatment
In infants and young children
• Digital repositioning. The parents are taught to replace the protrusion, and any underlying causes
are addressed.
• Submucosal injections. If digital repositioning fails after 6 weeks’ trial, injections of 5 per cent
phenol in almond oil are carried out under general anesthetic. As a result of the aseptic
inflammation following these injections, the mucous membrane becomes tethered to the muscle
coat.
• Surgery. Occasionally, surgery is required.
In adults
• Local treatments. Submucosal injections of phenol in almond oil or the application of rubber
bands are sometimes successful in cases of mucosal prolapse.
• Excision of the prolapsed mucosa. When the prolapse is unilateral, the redundant mucosa can be
excised or, if circumferential, an endoluminal stapling technique can be used.
Full-thickness prolapse
Full-thickness prolapse (synonym: procidentia) is less common than the mucosal variety. The protrusion
consists of all layers of the rectal wall and is usually associated with a weak pelvic floor. It is more than 4 cm
and commonly as much as 10–15 cm in length. On palpation between the finger and thumb, the prolapse
feels much thicker than a mucosal prolapse, and obviously consists of a double thickness of the entire wall
of the rectum. Any prolapse over 5 cm in length contains anteriorly between its layers a pouch of
peritoneum. Complete prolapse is uncommon in children. In adults, it can occur at any age, but it is more
common in the elderly. Women are affected six times more often than men, and it is commonly associated
with prolapse of the uterus. In approximately 50 per cent of adults, fecal incontinence is also a feature.
Differential diagnosis
In the case of a child with abdominal pain, prolapse of the rectum must be distinguished from ileocaecal
intussusception protruding from the anus. In rectosigmoid intussusception in the adult, there is a deep
groove (5 cm or more) between the emerging protruding mass and the margin of the anus, into which the
finger can be placed.
Treatment
Surgery is required, and the operation can be performed via the perineal or the abdominal approaches. An
abdominal rectopexy has a lower rate of recurrence but, when the patient is elderly and very frail, a
perineal operation, sometimes performed under spinal anesthetic, is usually safer. As an abdominal
procedure risks damage to the pelvic autonomic nerves, resulting in possible sexual dysfunction, a perineal
approach is often preferred in young men.