The Small Intestine and Colon

Question 1

Meckel’s Diverticulum - Description

Answer 1

A remnant of the vitello intestinal duct which normally disappears during embryological development. It is found in approximately 2% of the population and occurs approximately 2ft proximal to the ileocaecal valve on the antimesenteric border (the border that is not attached to the mesentery).

The length is variable - it can extend as far back of the umbilicus on the anterior abdominal wall and occasionally it may even present as mucosa protruding at the umbilicus (a vitello intestinal fistula).

Question 2

Meckels - Features, Investigation and Management

Answer 2

• Presentation – usually completely asymptomatic but can present with bleeding (if it contains ectopic gastric mucosa), volvulus or intussusception or if it becomes inflamed if may present like appendicitis.
• Diagnosis – often at laparotomy – if appendix appears normal in appendectomy look for a Meckel’s.
• Management – surgical excision of the affected bowel.

Question 3

SI Tumours - Benign

Answer 3

Rare comprising <5% of all gastrointestinal tumours – can be primary, secondary, benign or malignant

Benign tumours – can arise from any elements of the bowel wall – lipomas (from fat), leiomyomas (from smooth muscle), neurofibromas (from nerves), adenomas (arise from glandular mucosa) or adenomatous polyps (may be premalignant or associated with Peutz-Jegher’s or polyposis syndromes).

Question 4

SI Tumours - Malignant

Answer 4

• Lymphomas – can occur in the small bowel.
• Adenocarcinomas – rare and thought to arise from pre-existing adenomatous polyps.
• Carcinoid tumours – low grade malignancies that are believed to arise from neuroectodermal cells embryologically. The commonest site is in the appendix but they can occur anywhere in the gastrointestinal tract or in the lungs. They release serotonin (5-HT) and kinins which can cause symptoms if they enter the circulation but they are normally broken down by first pass metabolism in the liver. However if metastases are present there is no first pass metabolism and carcinoid syndrome can occur – flushing, bronchospasm and diarrhoea.

Question 5

Acute Appendicitis - Incidence and Pathology

Answer 5

• Incidence – most common surgical emergency with a life time incidence of 6% (rare before 2 years).
• Pathogenesis – gut organisms invade the appendix wall after lumen obstruction by faecolith, lymphoid hyperplasia or filarial worms. This leads to oedema, ischaemia, necrosis and perforation.

Question 6

Acute Appendicitis - Clinical features

Answer 6

• Symptoms – classically periumbilical pain that moves to the right iliac fossa, anorexia is an important feature but vomiting is rarely prominent until later. Constipation is usual but diarrhoea may also occur.
• Signs – pyrexia (37.5-38.5°C), tachycardia, flushing, foetor, a furred tongue, shallow breaths and lying still. There is also pain, guarding, rebound and percussion tenderness in the right iliac fossa.

Question 7

Acute Appendicitis - Special Signs

Answer 7

• Rovsing’s sign – pain in the right iliac fossa is greater than pain in the left iliac fossa when the LIF is pressed
• Psoas sign – pain on extending the hip if retrocaecal appendix.
• Cope sign – pain on flexion and internal rotation of right hip if appendix is close to obturator internus.

Question 8

Acute Appendicitis - Investigations

Answer 8

• Blood tests – FBC will reveal a neutrophil leucocytosis and elevated CRP.
• Ultrasound or CT scan if diagnosis is unclear – will reduce rate of negative appendectomy but may cause fatal delay.

Question 9

Acute Appendicitis - Management and Surgery

Answer 9

• Management – prompt appendectomy and give 500mg Metronidazole TDS and 1.5g Cefuroxime TDS – 1 to 3 doses IV starting 1 hour pre-op reduces wound infections (give a longer course if perforated).
• Appendectomy approach - Gridiron incision over McBurneys point at 90° to a line between umbilicus and ASIS. Alternative approach is a Lanz incision – more horizontal in Langer’s lines gives a better scar.

Question 10

Acute Appendicitis - Complications

Answer 10

• Perforation – more common if a faecolith is present and in young children due to delay in dx.
• Appendix mass – may occur when an inflamed appendix becomes covered in omentum – an ultrasound or CT can help with diagnosis. It is important to exclude a colonic tumour.
• Appendix abscess – may occur if an appendix mass fails to resolve but enlarges as the patient becomes increasingly unwell. Management is with percutaneous or surgical drainage.

Question 11

Obstruction - Features

Answer 11

Cardinal features - vomiting, colic, constipation and abdominal distension. Fermentation of intestinal contents in established obstruction causes ‘faeculent’ vomiting.

Constipation is absolute (i.e. no faeces or flatus passed) in distal obstruction but in high obstruction this may not be the case.

Abdominal distension becomes more marked as obstruction progresses. There are active tinkling bowel sounds.

Question 12

Obstruction - small or large bowel

Answer 12

In small bowel obstruction vomiting occurs earlier, distension is less and pain is higher in the abdomen. In addition the abdominal x-ray will show central gas shadows with valvulae conniventes that completely cross the lumen and no gas in the large bowel.

In large bowel obstruction pain is more constant and the x-ray shows peripheral gas shadows proximal to the blockage but not in the rectum (unless you have done a PR which is essential). Remember that large bowel haustra do not cross all the lumens width.

Question 13

Obstruction - Ileus or Mechanical Obstruction

Question 14

Obstruction - 3 Types

Answer 14

• Simple – there’s 1 point of obstruction and not accompanied by vascular compromise.
• Closed loop – there is obstruction at 2 points forming a loop of grossly distended bowel that is at risk of perforation – often occurs at the caecum where the bowel is thinnest and widest. A caecum diameter greater than 12cm requires urgent decompression.
• Strangulated – the blood supply is compromised producing sharper and more constant pain which tends to be more localised than the central colic of obstruction. There may be peritonism, fever, a raised WCC and other signs of mesenteric ischaemia.

Question 15

Obstruction - Causes

Answer 15

• Extramural - adhesions, strangulated hernia, volvulus (gastric, caecal or sigmoid) or extrinsic compression.
• Intramural - tumours, inflammation e.g. Crohn’s, infarction or strictures.
• Luminal - constipation, gallstone ileus, intussusception, large polyps or foreign body.

Question 16

Obstruction - Initial Management

Answer 16

• General principles – site, speed of onset and completeness of obstruction will determine definitive management – strangulation and large bowel obstruction will require surgery whereas ileus and incomplete small bowel obstruction can initially be managed conservatively.
• Immediate action – drip and suck technique – insert a NG tube, give IV fluids to rehydrate, analgesia, correct electrolyte imbalance, bloods – FBC, U+Es and amylase, abdominal x-ray, erect chest x-ray and catheterise to monitor fluid status.

Question 17

Obstruction - Further Management

Answer 17

• Further imaging – colonscopy may be done in some cases of mechanical obstruction although there is a danger of inducing perforation. A gastrograffin follow through study may be helpful in determining the level of obstruction and may also have some therapeutic action.
• Surgery – strangulation and closed loop obstruction require immediate emergency surgery.

Question 18

Coloractal Ca - Incidence and Sites

Answer 18

• Incidence – the 3rd most common cancer and the 2nd most common cause of UK cancer deaths. The majority are adenocarcinomas and 56% of presentations will be in patients aged 70 years and over.
• Affected sites – 15% ascending, 10% transverse, 5% descending, 25% sigmoid colon and 45% rectum.

Question 19

Colorectal Ca - Predisposing Factors

Answer 19

Neoplastic polyps, inflammatory bowel disease, familial adenomatous polyposis, HNPCC (hereditary non-polyposis colorectal cancer), previous malignancy, low fibre diet and smoking.

Non-steroidal anti-inflammatory’s and aspirin are known to be protective factors.

Genetics – if no close relatives are affected risk is 1 in 50, if 1 is affected risk is 1 in 17 and if 2 are affected risk is 1 in 10. The patient should be referred when they are 10 years younger than the youngest affected relative.

Question 20

Colorectal Ca - Presentation

Answer 20

Depends on the site – left sided causes bleeding and mucus excretion, altered bowel habit, obstruction, tenesmus or a mass on PR.

Right sided causes weight loss, anaemia, abdominal pain and obstruction is less likely.

Either can cause a palpable mass, perforation, haemorrhage or fistula.

Question 21

Colorectal Ca - Investigations

Answer 21

• Faecal occult blood test to confirm the diagnosis and also used for screening.
• Bloods – FBC (microcytic anaemia), Us and Es, LFTs and CEA (carcino-embryonic antigen).
• Imaging – sigmoidoscopy (allows visualisation and biopsy of the first 15cm), barium enema or colonscopy (which can be done ‘virtually’ by CT). Ultrasound or CT can be also used for staging.

Question 22

Colorectal Ca - Dukes Staging

Answer 22

Stage - Description - 5 year survival

• Stage A - confined to the mucosa and submucosa - 90%.
• Stage B - extension through the muscularis mucosae - 65%.
• Stage C - involvement of regional lymph nodes - 30%.
• Stage D - distant metastases are present - <10%.

Question 23

Right Hemicoloectomy

Answer 23

For caecal, ascending or proximal transverse colon malignancies.

Question 24

Left Hemicolectomy

Answer 24

For tumours in the distal transverse colon or in the descending colon.

Question 25

Sigmoid Colectomy

Answer 25

Exclusively for sigmoid tumours.

Question 26

Anterior Resection

Answer 26

For low sigmoid or high rectal tumours – usually a primary anastomosis is performed using either sutures or a staple gun.

If the immediate strength of the anastomosis is in doubt then a temporary proximal stoma (e.g. ileostomy or transverse colostomy) may be constructed and closed a few weeks later (defunctioning - to divert faeces from anastomosis).

Question 27

Abdomino-Perineal Resection

Answer 27

For tumours low in the rectum (<8cm from the anus) where an incision would damage the anal sphincters – a permanent colostomy is created following removal of the rectum and anus. A much more extensive operation than anterior resection.

Question 28

Hartmann’s Procedure

Answer 28

The sigmoid colon is resected and the rectal stump is left inside and closed with sutures. A temporary end colostomy is brought out in the left lower quadrant.

This is most often performed for perforated diverticulum where the affected portion of bowel is resected but the contamination makes it unsafe to form an immediate anastomoses

Question 29

Ileostomy

Answer 29

Usually in the right lower quadrant and because small bowel content is irritant to the skin ileostomies are constructed with a spout which stands clear of the skin by a few cm.

It may be an end ileostomy (with 1 opening) following total colectomy or a loop ileostomy (with 2 openings) for defunctioning – to give anastomosis time to heal before restoring continuity.

Question 30

Defunctioning Transverse Colostomy

Answer 30

In the right upper quadrant again with 2 openings.

Question 31

Colostomies

Answer 31

Usually found in the left lower quadrant:

• End colostomy – produced after resection of the rectum or sigmoid colon. Temporary after a Hartmann’s procedure or permanent following abdomino-perineal excision.
• Loop colostomy – when the apex of the sigmoid is brought out as a stoma without a resection being performed. Used for inoperable rectal carcinoma that may obstruct.
• Double-barrelled colostomy – if after a resection it’s thought to be unsafe to join bowel ends together but distal end is not long enough then both ends may be brought out.