The Small Intestine and Colon

Question 1

Colorectal Ca - Screening

Answer 1

Colonoscopy is the ideal investigation but is expensive and requires sedation.

The following patients should be regularly screened – those with familial adenomatous polyposis, strong family history, personal history of polyps or colorectal cancer or patients with ulcerative colitis for >10 years.

Question 2

Faecal Occult Blood

Answer 2

Relatively low sensitivity and gives a high false positive rate but has been shown to decrease mortality.

The NHS Bowel Cancer Screening Programme offers screening every 2 years to all men and women aged 60-69 years – abnormalities are given colonoscopy.

Question 3

Carcino-Embryonic Antigen

Answer 3

A serological marker for colorectal cancer – not elevated in early disease (raised in <5% with stage A) and raised in other conditions e.g. inflammatory conditions of the GI tract, smoking or renal impairment).

Therefore it used in follow up – should fall to within normal limits within weeks of surgical removal so can be used to identify reoccurrence.

Question 4

Prognosis

Answer 4

60% are amenable to radical surgery and 75% of these are alive at 7 years.

Post-operative anastomotic leakage is known to decrease survival rates in otherwise potentially curative surgery.

Question 5

Polyp - Definition

Answer 5

A lesion which projects into the lumen of the bowel some of which may become malignant.

Types of polyps - adenomatous, hamartomatous, mesenchymal, metaplastic or inflammatory.

Question 6

Adenomatous Polyps

Answer 6

Important due to their tendency to become adenocarcinoma – likelihood of this occurring appears to be related to increasing size.

Evidence for this is early stages of malignancy (severe dysplasia and carcinoma in situ) can be found in polyps and patient with familial adenomatous polyposis develop malignancy at an early age without prophylactic colectomy.

Sub-classification – 75% are well differentiated tubular adenomas which are often on a stalk, 10% are less well differentiated villous adenomas which are flat and 15% are tubulo-villous.

Question 7

Adenomatous Polyps - Presentation

Answer 7

Bleeding (can be frank or microscopic which presents as anaemia), PR mucus (polyps may secrete a large amount of mucus), tenesmus (due to a large benign polyp in the rectum), prolapse of the polyp through the anus or rarely a change in bowel habit.

Question 8

Adenomatous Polyps - Investigations

Answer 8

May be diagnosed on imaging the colon with barium enema but if suspected a colonoscopy provides an opportunity to biopsy or completely remove the polyp.

Histological investigation is required to exclude dysplasia (severe dysplasia can be classed as premalignant).

Question 9

Familial Adenomas

Answer 9

• Familial multiple polyposis coli – autosomal dominant – multiple neoplastic colonic polyps develop in the 2nd – 3rd decade – majority have prophylactic colectomy in 20’s.
• Gardener’s syndrome – multiple adenomas, bony osteomas and epidermoid cysts.

Question 10

Hamartomatous Polyps - Definition

Answer 10

A hamartoma is a lesion where there is overgrowth of one or more of the cell types which are normal constituents of the organ in which they arise. There are 2 types of colonic hamartomas - juvenile polyps and Peutz Jeghers syndrome.

Juvenile polyps – these have a low malignant potential and may present with bleeding or intussusception and sometimes slough off spontaneously and present with the material passed in a motion. It is usually possible to manage these polyps during colonoscopy.

Question 11

Peutz Jaghers Syndrome

Answer 11

Rare autosomal dominant condition where multiple hamartomatous polyps appear throughout the gastrointestinal tract. Affected individuals also have pigmentation of the skin around the lips and gums.

Again the malignant potential is small although overall these patients are at increased risk of malignancy (both GI and non-GI tract).

Question 12

Mesenchymal Polyps

Answer 12

Lipomas (benign fat tumours), leiomyomas (benign tumours of smooth muscle), neurofibromas (benign tumours of nerves) and haemangiomas (benign tumours of blood vessel origin) can all occur in the wall of the colon and if they protrude into the lumen they are by definition polyps. They are rare in practice but may mimic the presentation of carcinoma.

Question 13

Metaplastic Polyps

Answer 13

aka hyperplastic polyps are usually small, often multiple and raised above the surrounding mucosa.

They have no malignant potential and because of their size are usually asymptomatic. Their only relevance is differentiating them from adenomatous polyps.

Question 14

Inflammatory Polyps

Answer 14

Found in inflammatory bowel conditions e.g. pseudopolyps in ulcerative colitis.

Question 15

Diverticular Defintions

Answer 15

A gastrointestinal diverticulum is an outpouching of the gut wall usually at sites of entry of perforating arteries.

Diverticular disease means that diverticula are present and diverticular disease means they are symptomatic.

Diverticulitis means there is inflammation of a diverticulum.

Question 16

Diverticulosis - Pathology

Answer 16

Most occur in the sigmoid colon with 95% of complications occurring at this site but right sided and massive single diverticula can also occur.

Lack of dietary fibre is thought to lead to high intra-luminal pressure, which force the mucosa to herniate through the muscle layers of the gut at weak points adjacent to penetrating vessels.

30% of Westerners have diverticulosis by the age of 60 years.

Question 17

Diverticulosis - Diagnosis

Answer 17

PR examination (may reveal a pelvic abscess or colorectal cancer which is the chief competing diagnosis) and imaging e.g. sigmoidoscopy, barium enema, colonoscopy or a CT scan.

Question 18

Diverticular Disease

Answer 18

There may be altered bowel habit ± left sided colic relieved by defecation, nausea and flatulence.

A high fibre diet (e.g. wholemeal bread, fruit and vegetables) may be tried and antispasmodics e.g. Mebeverine may help.

Surgical intervention is an occasional last resort.

Question 19

Diverticulitis

Answer 19

Features of diverticular disease plus pyrexia, raised white cell count and CRP or ESR, tender abdomen ± localised or generalised signs of peritonism – worse on movement and may be guarding.

Question 20

Diverticulitis - Management

Answer 20

• Mild attacks – in most cases it can be managed at home with bowel rest – oral fluids only and antibiotics e.g. Co-amoxiclav (Ciprofloxacin if allergic) and Metronidazole.
• Severe attacks – if the patient cannot tolerate oral fluids or pain is not controlled they should be admitted for analgesia, kept nil by mouth, IV fluids and antibiotics e.g. IV Cefuroxime and Metronidazole until the results of cultures are available. Most cases resolve on this regime but abscess formation is possible and will require CT guided percutaneous drainage.

Question 21

Diverticulitis - Imaging and Surgery

Answer 21

• Imaging – erect chest x-ray and ultrasound to detect perforation, free fluid and collections.
• Surgery – may be required for generalised suppurative peritonitis or faecal peritonitis.

Question 22

Diverticulitis - Complications - Perforation and Haemorrhage

Answer 22

• Perforation – there is ileus, peritonitis and shock and the mortality rate is 40%. Manage as an acute abdomen and perform a Hartmann’s procedure. It is possible to do a colonic lavage via the appendix stump and an immediate primary anastomosis to avoid repeat surgery.
• Haemorrhage – usually sudden and painless. Bleeding usually stops with bed rest although a transfusion may be required. In severe cases embolisation or colonic resection may be necessary after locating bleeding points by angiography or colonscopy.

Question 23

Diverticulitis Complications - Abscess, Fistulas and Strictures

Answer 23

• Fistulae – can be enterocolic, colovaginal or colovesical and management is always surgical.
• Abscesses – cause a swinging fever, leucocytosis and localising signs e.g. a boggy rectal mass. If there are no localising signs perform an ultrasound to exclude a sub-phrenic abscess. Patients should be given antibiotics and ultrasound or CT guided drainage may be required.
• Post-infective strictures – these may form in the sigmoid colon and could lead to obstruction.