Colorectal Surgery JC060: Intestinal Obstruction: Colorectal Cancer

Question 1

Questions to Intestinal obstruction

Answer 1

1. **Paralytic ileus vs **Mechanical obstruction
   - Small bowel: Mechanical usually
2. Site + Cause of obstruction
   - ***Small vs Large bowel
3. Simple / ***Strangulated (blood supply compromised)
   - indication for surgery
4. What investigations
5. Treatment
   - conservative?
   - duration
6. Indications for surgery
7. Surgical options

Question 2

***Intestinal obstruction

Answer 2

Mechanical obstruction:
- Physical barrier to aboral progress of intestinal contents

Paralytic ileus:
- Failure of peristalsis to propel intestinal contents with no mechanical barrier

Question 3

***Causes of Paralytic ileus

Answer 3

記: Post-op, Peritonitis, Ischaemia, Metabolic, Medication

Intra-peritoneal (insult to peritoneal cavity):
1. **Post-op
2. **Peritonitis / Intra-abdominal abscess (e.g. perforated ulcer / appendicitis)
3. Inflammatory / Infective conditions
4. ***Intestinal ischaemia (e.g. atherosclerosis)

Retroperitoneal (insult to Retroperitoneal cavity / Autonomic NS controlling peristalsis):
1. **Retroperitoneal haematoma / infection
2. Aortic, Spinal, Urological operations
3. **Pancreatitis

Extra-abdominal conditions
1. **Metabolic abnormalities
- Electrolyte imbalance
- Sepsis
- Uraemia
- Hypothyroidism
- Lead poisoning
- Prophyria
2. **Medications: Opioids, Anticholinergics, Antihistamines, Catecholamines
3. Spinal injury / operation

Question 4

Clinical features of Paralytic ileus

Answer 4

1. Abdominal pain
   - **Diffuse, Constant, Less severe (vs **Colicky pain in Mechanical obstruction)
2. Abdominal distension
3. Vomiting
4. Constipation
5. **Sluggish / Absent bowel sound (vs **Hyperactive in Mechanical obstruction)
6. Features associated with cause
   - e.g. peritoneal signs in peritonitis

Question 5

Mechanical bowel obstruction

Answer 5

Pathophysiology:
Proximal bowel distended with gas and fluid
—> Hypersecretion + Loss of fluid to gut / extracellular space / peritoneal cavity
—> **Pressure buildup (↑ luminal pressure) + **Bacterial overgrowth in proximal bowel (+ **Edematous bowel wall)
—> **Compromised blood supply
—> ***Necrosis + Perforation of bowel (accelerated in closed loop / strangulating obstruction)

Classification:
- Partial / Complete
- Acute / Chronic
- Simple (obstruction of lumen, usually at 1 point)
- **Strangulating (blood supply to bowel impaired)
- **Closed loop obstruction (lumen occlusion in >=2 points)

Question 6

Clinical features of Mechanical obstruction

Answer 6

1. ***Colicky pain (Gripping pain)
   - if ischaemia —> Constant severe pain
2. Abdominal distension (depend on level of obstruction)
   - upper level obstruction: less prominent distension
   - colonic obstruction: ***more prominent distension
3. Vomiting
   - upper level obstruction
4. Constipation
5. ***Hyperactive bowel sounds

Severity of each symptom depends on the level of obstruction

Question 7

History taking of Intestinal obstruction

Answer 7

1. Previous episodes bowel obstruction
2. Previous Abdominal / Pelvic ***operation
3. History of **cancer / abdominal / pelvic **radiation —> damage to bowel
4. History of Abdominal ***inflammatory condition

Question 8

Physical examination

Answer 8

1. General
   - **Fever
   - **Vital signs: Temp, BP, Pulse, RR
   - ***Hydration status
2. Abdomen
   - Distension (symmetrical / asymmetrical)
   - Tenderness, Guarding, Rebound tenderness (Peritoneal signs)
   - Mass (on deep palpation)
   - **Bowel sound (hyperactive / hypoactive)
   - **Hernia (cough impulse)
   - Scars
3. Rectal + Vaginal examination (+ Urine dipstix + External genitalia)

Question 9

***Investigations

Answer 9

1. Bedside tests
   - **Urinalysis (Urine R/M: UTI, Microscopic RBC)
   - **Pregnancy test
2. Blood tests
   - CBC + D/C (e.g. **Leukocytosis in strangulation, ischaemic bowel, diverticulitis, acute appendicitis, peritonitis)
   - LRFT
   - Electrolytes
   - **Amylase (acute pancreatitis)
   - **ABG (bowel ischaemia: metabolic acidosis, vomiting: alkalosis)
   - **VBG (lactate)
   - Clotting profile (planning for invasive procedures)
   - Type and screen (planning for invasive procedures)
3. Imaging
   - Erect CXR (pneumoperitoneum / free gas under diaphragm: perforated viscus)

• **Erect + Supine AXR
  —> **free gas (pneumoperitoneum)
  —> **dilated bowel (e.g. massive dilatation of colon)
  —> **air-fluid levels
  —> **evidence of strangulation:
  ——> thumb printing (large bowel wall thickening)
  ——> pneumatosis cystoides intestinalis (presence of multiple gas-filled cysts in submucosa / subserosa of the small intestine, signify necrotising enterocolitis, impending bowel perforation)
  ——> free peritoneal gas
  —> **air in biliary tree
• USG (pelvis)
• CT (more sensitive than AXR)
  —> **level of obstruction (transition between dilated and collapsed loop)
  —> lesions (tumour, foreign body)
  —> **viability of bowel (by IV contrast)
• Contrast studies
  —> water soluble contrast
  —> differentiate complete vs partial obstruction
  —> Ba study: precipitate complete obstruction + barium peritonitis
  —> therapeutic effect?

4. Endoscopy
   - Colonoscopy
   - Upper endoscopy

Question 10

***Small bowel vs Large bowel obstruction

Answer 10

Small bowel obstruction:
- Colicky abdominal pain with **visible peristaltic wave in upper / middle abdomen
- Upper / Epigastric abdominal distension
- **Early N+V
- ***Severe fluid + electrolyte imbalance
- Metabolic alkalosis

Large bowel obstruction:
- Longer spasm of lower abdomen
- Lower abdominal distension
- **Early constipation
- **No major fluid + electrolyte imbalance

Question 11

***Causes of Small bowel obstruction

Answer 11

Intraluminal
- Foreign bodies
- Gallstones
- Bezoars (food bolus)
- Worms

Intramural
- Tumour (primary / secondary)
- **Strictures (Crohn’s disease, Radiation, Anastomotic, Drug induced)
- *Intussusception (Gastrointestinal stromal tumor (GIST), Carcinoids, ***Meckel’s diverticulum)

Extramural
- **Adhesions (most common)
- **Hernia (common in HK)
- ***Volvulus
- Intraperitoneal malignancy (invading the small bowel)

Question 12

***Management decision

Answer 12

Conservative treatment vs Urgent surgery

Conservative (Non-operative) treatment:
1. Partial obstruction
- Adhesions (70% resolved its own)
- Crohn’s disease
- Radiation stricture (unless very tight)
- Disseminated malignant disease (∵ multiple levels of obstruction)

Indications for urgent surgery (記: Perforation, Inflammation, Ischaemia):
1. Incarcerated, **strangulated hernia
2. Suspected / proven strangulation
3. **Peritonitis
4. **Pneumoperitoneum (indicate viscus perforation)
5. **Pneumatosis cystoides intestinalis (presence of multiple gas-filled cysts in submucosa / subserosa of the small intestine, signify necrotising enterocolitis, impending bowel perforation)
6. **Closed loop obstruction
7. **Volvulus (a type of closed loop obstruction) with peritoneal signs

Question 13

Features suggestive of Strangulation

Answer 13

1. ***↑↑ Abdominal pain (Constant)
2. ***Blood in vomitus
3. **Fever, **↑ WBC
4. Imaging
   - ***Thumb printing (large bowel wall thickening)
   - Loss of mucosal pattern
   - Gas within bowel wall / within Intrahepatic branches of portal vein (may be seen in strangulation)

Question 14

1. ***Adhesive obstruction

Answer 14

• Most common cause of small bowel obstruction in western countries
• Clinical features of small bowel obstruction with previous abdominal surgery
• Success rate of non-operative treatment: ~50%

Causes:
1. Congenital
2. Post-inflammatory
3. ***Post-abdominal surgery (a defence mechanism after trauma / infection to peritoneal cavity)

Prevention:
1. **Gentle handling of bowel during surgery
2. Removal of powder from gloves
3. **Anti-adhesive film: Sodium hyaluronate bioresorbable membrane (Seprafilm)
4. Saline lavage
5. ***Minimally invasive surgery

Treatment:
1. Conservative
2. **Gastrografin
3. **Enterolysis / ***Adhesiolysis

Indications for surgery:
- Non-responsive to conservative treatment (after a few days)
- Clinical features of strangulation

Controversies:
- Duration of conservative treatment
- Administration of ***water soluble contrast (Gastrografin)
—> differentiate partial vs complete obstruction
—> therapeutic effect? (may resolve partial obstruction) reduced operating rate, shorten hospital stay

Question 15

2. ***Intussusception

Answer 15

• Mainly in childhood
• Idiopathic
• ***IC region
• Small bowel: **Gastrointestinal stromal tumor (GIST), Carcinoids, **Meckel’s diverticulum, ***Hypertrophic Peyer’s patches
• Large bowel: cancer
• Other causes: **Intraluminal polyp, **Lymphoma, ***Peutz–Jeghers syndrome (Polyp in small intestine)

Adults:
- lesion usually found as the leading point
- **pneumatic reduction unlikely useful
- **surgery usually indicated

Question 16

***Non-operative treatment

Answer 16

1. ***IV fluid + electrolytes + acid-base balance
2. ***NG tube decompression
3. ***Nil by mouth: Nutrition when prolonged fasting anticipated (Parenteral)
4. Frequent monitor vital signs, abdominal signs, X-ray

Question 17

***Operative treatment for Small bowel obstruction

Answer 17

1. **Enterolysis / **Adhesiolysis
   - lysis of adhesions + release of constricting band
2. ***Hernia: Repair
3. Foreign bodies (Bezoars, Gallstones)
   - **Break down and milk down to colon
   - **Enterotomy + removal
4. ***Bowel resection —> Anastomose with healthy bowel
   - strangulation with gangrenous bowel
   - unhealthy bowel

Question 18

Clinical features of Resolution of Obstruction

Answer 18

1. Less abdominal distension
2. Reduction of NG output
3. Passage of flatus + bowel movement
4. Resolution in AXR

Unresolved obstruction —> Surgical treatment (duration of Conservative treatment controversial: usually ***48 hours)

Prognosis of Small bowel obstruction:
Mortality:
- Non-strangulating obstruction: 2%
- Strangulating obstruction: 10-30%

Question 19

***Colonic obstruction

Answer 19

• 15% of IO
• ***Sigmoid colon usually
• Lesion at IC valve
  —> can present as Small bowel obstruction
  —> ***Competence of IC valve determines clinical features of distal colon obstruction

Competent IC valve:
- Large bowel shadow

Incompetent IC valve:
- Large bowel + Small bowel shadow

Causes:
1. **Cancer (most common)
2. **Volvulus
3. Diverticulitis
4. ***Stricture
- Anastomotic
- Radiation
- Ischaemic
- Endometriosis

5. ***Extrinsic compression
   - Metastasis
   - Pelvic / Extraperitoneal tumour (e.g. PoD tumour)

(6. Faecal impaction
- Digital evacuation)

Question 20

1. ***Obstructing Colorectal cancer

Answer 20

• 15-20% Colorectal cancer present with IO

Features:
- More advanced cancer (***>=Stage 2 ∵ through bowel wall)
- Elderly patients with comorbidity
- High operative mortality / morbidity
- Worse prognosis

Diagnosis:
1. Clinical
2. AXR
3. **CT scan
- IV contrast, **Rectal contrast
—> Site of obstruction (transition of dilated loop and collapsed loop)
—> Mass lesion
—> Perfusion of bowel wall
—> Distant disease in case of malignancy

4. **Sigmoidoscopy / Colonoscopy / Lower GI endoscopy
   - **Diagnostic
   - ***Therapeutic: Decompression in sigmoid volvulus + pseudo-obstruction, Stenting
   - Cautions: avoid excessive insufflation of gas
5. Contrast enema (less used now)

Management (記: Resuscitation, Decompression, Surgery, Non-surgery):
1. **Resuscitation
2. **Decompression with endoscopy
3. Operation
- ***Resection
—> Primary anastomosis
—> Without anastomosis

• Non-resection
  —> Proximal **stoma
  —> **Bypass

4. Non-surgical treatment
   - Insertion of metallic stent

Question 21

Determinants of procedures

Answer 21

Patient factors:
1. **General condition and nutritional status
2. **Haemodynamic status
3. ***Sepsis
4. Condition of remaining bowel

Tumour factors:
1. **Site of lesion (right colon vs left colon vs rectum)
2. **Invasion to adjacent structures
3. ***Perforation / contamination of peritoneal cavity

Surgeon factors:
1. Experience in bowel resection and anastomosis in emergency

Question 22

***Operative treatment of CRC

Answer 22

Right-sided obstruction: Caecum to Splenic flexure
1. Resection with Anastomosis (Ileocolic anastomosis)
- if patient stable (Right / Extended right colectomy)

2. ***Resection without Anastomosis
   - if patient / bowel condition not favourable
3. Non-resection: **Stoma / **Bypass
   - if advanced tumour

Left-sided obstruction:
Factors to consider:
- **Competence of IC valve (closed loop obstruction —> perforation)
- **Heavy bacterial + faecal load in proximal colon (higher chance of infective episodes at anastomosis / surgical site)
- **Edematous unhealthy proximal colon (if unprepared)
- Poor general condition of patient:
—> malignancy + malnutrition
—> dehydration
- **Primary anastomosis (colon to colon) is risky —> bowel compromised

1. 3-stage operation (old fashioned, not commonly performed today):
   - Transverse colostomy —> decompression
   - Resection + Anastomosis
   - Closure of colostomy
2. Hartmann’s operation
   - Resection without anastomosis
3. Primary resection and anastomosis
   - Segmental resection with primary anastomosis (on table lavage to wash out faeces in proximal colon)
   - Subtotal colectomy with anastomosis of Ileum and Distal colon / Rectum

Prognosis of emergency surgery for colonic obstruction:
- Mortality >10%
- Depend on:
—> Comorbidity
—> Advanced malignancy

Question 23

***Non-surgical treatment of CRC

Answer 23

Insertion of metallic stent
- made of metal alloys
- self-expanding mechanism
- insert + deploy under endoscopic / fluoroscopic guidance
- for definitive ***palliation (unresectable, metastatic disease)
—> avoid surgery
—> avoid stoma

• as a bridge to surgery
  —> avoid emergency surgery
  —> ***elective operation with more time for bowel preparation
  —> more time to stage the disease
  —> lower operative mortality and morbidity
  —> reduces stoma rate

Question 24

2. ***Volvulus of colon

Answer 24

• Rotation of colon along axis formed by its ***mesentery
• Commonly at Sigmoid (65%) / Caecum (30%)
• Colon obstruction with ***Impairment of circulation —> Prone to perforation / Ischaemia —> Surgical emergency

Investigations
- X-ray: Dilated sigmoid (**Coffee bean sign)
- Barium enema: **Bird’s beak / Ace of spade sign

Treatment:
1. **Sigmoidoscopic decompression (successful rate: 80%, recurrence 50%)
2. **Resection (if perforation, strangulation, failed decompression)

Question 25

3. ***Pseudo-obstruction (Ogilvie’s syndrome)

Answer 25

• Massive ***Colon dilatation in the absence of mechanical obstruction
• Usually associated with bedridden patients with severe ***extracolonic diseases / trauma
• Distended abdomen ***without pain
• X-rays: Severe gaseous distension of colon

Management:
- Exclude mechanical obstruction
1. NG tube feeding / enemas
2. **Colonoscopic decompression
3. **Rectal tube decompression
4. **Neostigmine (AChE inhibitor, cardiac SE)
5. **Caecostomy

Question 26

Summary

Answer 26

• Intestinal obstruction is a common surgical emergency
• Management: Initial resuscitation —> determination of site + cause of obstruction
• Decision on surgery + timing of surgery is important
• High mortality if complications occur

Question 27

JC Interactive Tutorial: Intestinal obstruction

Answer 27

Causes:
- Extramural: Adhesions, Hernia, Volvulus, Intussusception
- Mural: Stricture, Malignancy
- Intraluminal: Faecal impaction, Foreign body, Bezoars, Gallstones
- Mechanical vs Functional
Small intestine: **Adhesion
Large intestine: **Colon cancer

Cardinal signs:
- Abdominal pain
- Abdominal distension
- Vomiting
- Absolute constipation
- Visible peristalsis
- Focal tenderness (e.g. guarding, rebound tenderness)
- Lack of abdominal tenderness (obstruction with tenderness may indicate bowel strangulation)

Small intestine:
- Colicky, cramping, intermittent pain
- Spasms for a few minutes
- Central / Mid-abdominal pain
- Early vomiting (before constipation) (Gastric —> Biliary (indicate distal to Ampulla of Vater), Pancreatic —> Faeculent) —> Nature of vomitus hint level of obstruction
- Late constipation

Large intestine:
- Longer spasm
- Lower abdomen pain
- Late / Less prominent vomiting
- Earlier constipation
- Proximal obstruction may present as small bowel IO (e.g. incompetent IC valve)

Complications:
- Bowel strangulation —> ischaemia
- Perforation —> Pneumoperitoneum
- Dehydration
- Electrolyte imbalance
- Pressure on diaphragm —> respiratory compromise
- Vomitus aspiration

Closed loop obstruction:
- Surgical emergency
- Second obstruction proximally (e.g. volvulus / large bowel obstruction with competent IC valve)
- Strangulation —> Ischaemia —> Necrosis + Perforation

Investigations:
- CBC (anaemia)
- LFT
- RFT (U+C: hydration status)
- Electrolyte imbalance
—> Recurrent vomiting: Hypochloremic hypokaelmic metabolic alkalosis, Hyponatraemia
—> Bowel strangulation: Metabolic acidosis, Hyperkalaemia
- Arterial blood gas (Metabolic acidosis)
- Venous blood gas (High lactate: ischaemia)
- Amylase (leaked bowel)

Imaging:
- AXR (supine + erect)
—> Multiple air-fluid levels
—> 3, 6, 9 rule
—> Pneumoperitoneum (Rigler sign)
—> Thumb printing (indicate strangulation)
—> Stepladder sign
—> Intramural, Intraperitoneal, Extraperitoneal gas
- Contrast CT

General management (“Drip and suck”):
- NPO (Bowel rest)
- NG tube to decompress stomach
- IV fluid Resuscitation —> correct electrolyte
- Fecal impaction: Stool evacuation
- Rigid / flexible sigmoidoscopic detorsion (for Sigmoid Volvulus)

Surgical management:
- Laparotomy

Question 28

SpC Interactive tutorial: Intestinal obstruction
***Causes of of Small bowel obstruction

Answer 28

Classification according to Adhesion, External hernia, Virgin abdomen (∵ Management is different!!!)

1. ***Adhesion
   - Appendicectomy
   - Colorectal surgery
   - Cholecystectomy
   - Gastroduodenal surgery
   - Gynaecological surgery
2. ***External hernia (Give sedation —> Try reduce hernia at bedside —> Early elective surgery —> Emergency surgery)
   - Inguinal hernia
   - Femoral hernia
   - Incisional hernia
3. **Virgin abdomen (Conservative management usually not successful —> Require laparotomy)
   **Intraluminal:
   - **Gallstone (AXR show **pneumobilia, Treatment: Laparotomy + crushing and milk down / Enterotomy (try to avoid ∵ risk of anastomotic leak and stricture))
   - Bezoars
   - Parasites (e.g. ascaris)
   - Foreign body

**Intramural:
- **Tumour
—> Primary
——> Small bowel tumour (carcinoma, stromal tumour, lymphoma)
——> Carcinoma of caecum
—> Secondary
- ***Benign stricture
—> Crohn’s disease
—> Radiation enteritis

**Extraluminal:
- Internal hernia
- Congenital adhesion
- **Intussusception (Adult usually pathological because of tumour, resection always required, pneumatic reduction unlikely useful)
- ***Volvulus (Meckel’s diverticulum, Malrotation)

Question 29

Investigations of Small bowel obstruction

Answer 29

1. AXR
   - **Dilated small bowel
   - **Multiple air-fluid levels
2. CXR
   - ***Aspiration pneumonia
   - Atelectasis
3. CT scan
   - Dilated proximal and collapsed distal small bowel
   - **May identify the cause of obstruction
   - **May detect bowel ischaemia (intramural gas suggesting impending perforation)

Question 30

Management of Small bowel obstruction

Answer 30

General:
1. NPO
2. **IV fluid
3. **NG tube decompression
4. Correction of electrolytes

Adhesive obstruction:
1. **Conservative treatment (70% usually resolve on its own)
2. **Gastrografin meal and follow through (if no response to conservative treatment within 48 hours)
3. **Operative treatment (if suspicion of bowel strangulation / Gastrografin shows complete obstruction
- **Enterolysis +/- ***Bowel resection

External hernia:
1. ***Hernia repair
2. Bowel resection

Virgin abdomen:
1. **Laparotomy
- **Enterotomy and removal of obstructive material
- ***Bowel resection
- Bypass
- Enterolysis
- Stricturoplasty

Question 31

***Causes of Large bowel obstruction

Answer 31

1. ***Colorectal carcinoma (90%)
   - ~10% of patients with colorectal carcinoma present with acute obstruction
   - CA sigmoid and descending colon (58%)
   - CA ascending and transverse colon (38%)
   - CA rectum (4%)
2. **Volvulus
   - **Sigmoid (80%)
   - Caecum
   - Transverse colon
   - Ileosigmoid knotting
3. ***Pseudo-obstruction
4. Diverticular disease
5. Inflammatory bowel disease
6. Irradiation stricture
7. Ischaemic stricture
8. ***Faecal impaction (Treatment: Digital evacuation)

Question 32

Investigations of Large bowel obstruction

Answer 32

1. AXR
   - **Distended large bowel +/- small bowel (depending on competence of ileocaecal valve)
   - Colonic cut off point at level of obstruction
   - **Multiple air-fluid levels
2. CXR
   - **Aspiration pneumonia
   - Atelectasis
   - **Lung metastasis
3. Colonoscopy
   - Localization of obstructive tumour
   - **Exclude synchronous tumour / polyps distal to level of obstruction
   - **Stenting
4. CT
   - Useful if colonoscopy fails to locate obstructive tumour
   - **Staging
   - Dilated proximal and collapsed distal large bowel
   - **May identify the cause of obstruction
   - ***May detect bowel ischaemia (intramural gas suggesting impending perforation)

Question 33

Management of Large bowel obstruction

Answer 33

1. ***Stenting
   - Insertion of self expanding metallic stent
   - Up to 22 mm diameter on full expansion
   - Performed under colonoscopic and fluoroscopic guidance
   - Avoids emergency operation and stoma
   - Most commonly performed for sigmoid and rectal tumours
   - Technically difficult for more proximal tumours
2. Surgery
   **Right sided obstruction:
   (obstruction at **ascending and **transverse colon)
   - Right / Extended right hemicolectomy with **primary anastomosis
   - Right / Extended right hemicolectomy with ***exteriorisation of bowel ends
   - Ileocolic bypass
   - Diverting stoma

**Left sided obstruction:
(obstruction distal to **splenic flexure)
- 3 stage procedure
- 2 stage procedure
- 1 stage procedure

Question 34

3 stage procedure

Answer 34

1st stage: Diverting stoma
2nd stage: Resection of tumour + Anastomosis
3rd stage: Closure of stoma

Advantage:
- Treatment of choice for patients who are unfit for resection at presentation

Disadvantage:
- ***Decreased long term survival

Question 35

2 stage procedure

Answer 35

1st stage: Resection of tumour + End colostomy (Hartmann’s operation)
2nd stage: Reanastomosis

Advantage:
- **Early removal of tumour
- **Anastomosis and its attendant risk of failure are avoided in the 1st stage operation

Disadvantage:
- Reanastomosis can be very difficult
- Up to 40% of patients did not have bowel continuity restored due to various reasons

Question 36

1 stage procedure

Answer 36

1st stage:
- Segmental resection (Left hemicolectomy / Sigmoid colectomy / Anterior resection) + On table irrigation + Primary anastomosis
- Subtotal / Total colectomy + Primary anastomosis

Advantage:
- ***Avoidance of stoma

Disadvantage:
- Risk of anastomotic leakage 5-10%

Question 37

Sigmoid volvulus

Answer 37

• Elderly
• 1/3 of patients either have mental illness / institutionalised
• Narrowed sigmoid mesocolon, redundant and faecal loaded sigmoid colon

Treatment:
1. **Colonoscopic decompression +/- Insertion of **flatus tube (80% success rate)
2. **Early sigmoid colectomy to prevent recurrence
3. **Urgent laparotomy
- peritonitis
- bowel ischaemia on colonoscopy
- colonoscopic decompression fails

Question 38

Pseudo-obstruction (Ogilvie’s syndrome)

Answer 38

• S/S of large bowel obstruction in the absence of mechanical obstruction

Causes:
Surgical:
- pelvic surgery (15%)
- trauma (11%)
- orthopaedic surgery (7%)
- caesarian section (4%)
- cardiovascular surgery (4%)

Medical:
- infection (10%)
- cardiac disease (10%)
- neurological disease (9%)
- pulmonary disease (6%)
- metabolic disease (5%)
- renal failure (4%)

Treatment:
1. **Colonoscopic decompression +/- Insertion of **flatus tube
2. **Adrenergic blocker (Guanethidine)
3. **Parasympathomimetic agent (Neostigmine)
4. ***Caecostomy

Question 39

SpC Interactive tutorial: Colorectal malignancy
Risk factors for CRC

Answer 39

1. Age
2. Race
3. **Personal history of colorectal polyps / cancer
   (Colonic adenoma: (SpC Medicine)
   - Two-thirds of all colonic polyps
   - Variable disease course
   - Risk of progression increased in advanced adenoma:
   —> **High-grade dysplasia
   —> **Villous histology
   —> **>=1 cm
   —> Advanced adenoma: earlier surveillance colonoscopy)
4. ***Personal history of IBD (Crohn’s, UC)
5. Type 2 DM
6. **Family history
   - **Family history without polyposis syndrome
   - **FAP
   - **HNPCC
   - Other polyposis syndrome (MYH-associated polyposis, Hamartoma polyposis)
7. Lifestyle
   - **Diet
   —> ↑ risk: Red meat, Processed meat, Fat
   —> ↓ risk: Dietary fibres
   - **Obesity
   - Alcohol
   - ***Smoking
   - Lack of exercise
   - Other dietary factors: Ca, Folate, NSAIDs

Question 40

Pathogenesis of Sporadic cancer

Answer 40

1. **Chromosomal instability pathway (MSS pathway)
   - 60-70% of sporadic cases (“classical” adenoma carcinoma sequence)
   - **APC mutation (Early adenoma) —> K-ras mutation (Late adenoma) —> p53 mutation (Carcinoma)
   —> potential targets for Targeted therapy
2. **Microsatellite instability pathway (MSI pathway)
   - 15% of sporadic cancer (not belong to HNPCC)
   - **DNA mismatch repair gene mutation / silencing (Microsatellite instability) —> Mutations in regulatory genes (Carcinoma)
   —> potential targets for Targeted therapy

Pathophysiology:
- Adenoma carcinoma sequence (most common pathway)
- Stepwise manner
—> Polyp take ***7-10 years to progress to cancer
—> Allow screening
- Numerous genetic mutations involved (tumour suppression genes and oncogenes)
- Invasion of the bowel wall
- Spread to regional LN and distant organ by lymphatic / haematogenous / peritoneal spread

Question 41

Site distribution of CRC

Answer 41

Rectum: 30%
Sigmoid: 20%
Left colon: 15%
Transverse colon: 10%
Right colon: 25%

Rectum + Sigmoid + Left colon = 65%
- Sigmoidoscopy: can screen up to 70% of cancer

Other countries: Right shift of colon cancer (more Right colon cancer)
—> sigmoidoscopy less effective as a screening tool

Question 42

Screening for CRC

Answer 42

Options:
1. Detect cancer
- Stool for occult blood
—> Guaiac based
—> Faecal immunochemical test
—> Stool for DNA

2. Detect cancer + polyp
   - Colonoscopy
   —> expensive + invasive
   —> require bowel preparation
   —> anaesthesia
   —> introduce discomfort

• Sigmoidoscopy
• CT / MR colonography
  —> can detect extra colonic lesion
• Barium enema (obsolete)

Recommendations for average risk persons:
- After 45 years old
- Colonoscopy every 10 years (if normal)
- Sigmoidoscopy every 5 years —> Colonoscopy for abnormal test
- CT colonography every 5 years* —> Colonoscopy for abnormal test
- Barium enema every 5 years* —> Colonoscopy for abnormal test
- Annual stool test (FOB or FIT)

Question 43

***Clinical features of CRC

Answer 43

Asymptomatic:
- Detected by screening

Locoregional symptoms:
1. Rectal bleeding
2. Tenesmus
3. Mucus
4. ***Change in bowel habits (Spurious / Overflow diarrhoea)
5. Abdominal pain (if cause obstruction)
6. Abdominal mass
7. Anaemia
- Anaemia in elderly: suspect GI bleeding —> need to exclude CRC

Systemic symptoms (Late):
1. Weight loss
2. Loss in appetite

Metastatic symptoms:
1. Abdominal masses (liver, omentum)
2. Jaundice
3. Bone pain, pathological fracture
(4. Lung)

Acute symptoms:
1. Obstruction
2. Perforation
- Localized abscess
- Peritonitis
3. Severe bleeding (uncommon)

Question 44

***Investigations for CRC

Answer 44

1. Blood tests (workup for surgery, chemo)
   - Hb
   - LRFT
2. Tumor marker
   - CEA: as baseline
   —> **FU of patients after curative resection
   —> **Earlier detection of recurrence / metastasis
   —> ***Monitor treatment progress
   —> A glycoprotein present in primitive endoderm
   —> Serum level elevated usually in advanced disease
   —> In early disease, normal serum in 30-40% of patients
   —> NOT as screening / diagnosis
   —> Other malignant causes: gastric, pancreatic, lung cancer
   —> Benign causes: smoking
3. Colonoscopy
   - Diagnosis of tumour with biopsy (esp. important for distal rectal cancer since anal cancer will have different treatment!)
   - Removal of polyps
   - Detection of synchronous cancer
4. CT, MRI, (USG), PET scan
   - Extent of local disease
   —> Determine Surgical options, Neoadjuvant therapy
   - Distant metastasis

Question 45

CT, MRI, PET scan for CRC

Answer 45

CT:
- Less accurate in assessing local diseases
- Assessment of ***distant metastasis (Liver, Lung, Pelvis)

MRI:
Accurate in the assessing **Rectal cancer
1. **Mesorectal margins (distance accurately defined)
—> Determine Surgical options + **Neoadjuvant therapy + **Prognosis of rectal cancers
2. ***Lymph nodes within and outside mesorectum (e.g. pelvic sidewall)
3. Extramural vascular invasion
4. After chemoradiation
5. For recurrent disease

PET scan:
- FDG is used in patients with colorectal cancer
- Detects hypermetabolic lesions (both **primary tumour, **metastases, ***recurrences)
- Helps to differentiate recurrence from scarred tissues
- Helps in surgical decision in the management of recurrent / metastatic diseases

Question 46

***Staging in CRC

Answer 46

Purpose:
1. Guide treatment
2. Prognostication

AJCC TNM staging:
Stage I: **T1-2, N0, M0
Stage II: **T3-4, N0, M0
Stage III: any T, **N1-2, M0
Stage IV: any T, any N, **M1

T:
- T1: invades **submucosa (anything more superficial —> benign, other names: CIS, intraepithelial neoplasm, severe dysplasia)
- T2: invades to **muscularis propria but not through it
- T3: invades through the muscularis to **subserosa
- T4 (a/b): invades **through the serosa and to other organs

N:
- N0: no lymph node involved
- N1: 1-3 lymph nodes
- N2: 4 or more lymph nodes

M:
- M0: no distant metastasis
- M1: distant metastasis

Dukes’ staging:
- Dukes’ A: tumor within the wall of the bowel
- Dukes’ B: tumor invades through the wall of the bowel
- Dukes’ C: presence of regional lymph node metastasis
- (Dukes’ D: presence of distant metastasis)

Question 47

***Treatment for CRC

Answer 47

1. Surgery
   - ***Curative resection
   —> Resection of bowel segment which bears the tumor + Adequate lymphadenectomy
   —> Resection of distant metastasis (e.g. liver / lung metastasis)

• ***Palliative resection
  —> Palliation of symptoms (e.g. obstruction and bleeding) (when removal of all cancer tissue not possible)
• **Non-resection
  —> **Stoma / ***Bypass surgery for palliation

2. Adjuvant therapy
   - Depends on stage
   - Recommendations:
   —> **Postoperative chemotherapy for Stage 3 cancer
   —> Regimen: 5 FU based
   —> New agents: Oxaliplatin, Xeloda
   —> Stage 2: controversial (consider if have other poor prognostic features: **lymphovascular permeation, emergency surgery, no. of LN harvested)

Question 48

***Surgery for CRC

Answer 48

Principles:
1. **Resection of the bowel segment + **lymphadenectomy (allow pathologist for staging + prevent local recurrence)
2. Resection depends on the **site of tumour
3. Site of resection usually determined by **vascular anatomy (∵ lymphatics follow arteries (from Andre Tan))
4. A mural **margin of **5 cm is usually adequate
5. Restoration of bowel ***continuity

Emergency operation:
1. Obstruction
2. Perforation
- Higher operative mortality and morbidity
- Worse prognosis (stage for stage)

Peri-operative preparation:
1. Mechanical bowel preparation?
- mechanical prep + oral antibiotics (not GI absorbable e.g. Neomycin)
2. Prophylactic antibiotics
- single dose of IV antibiotics on induction +/- 2-3 postoperative doses
- prolonged antibiotics not necessary (∵ risk of Clostridium difficile)
3. Prophylactic therapy against DVT
- Mechanical: Stocking
- Pharmacological: Anticoagulant

Question 49

Laparoscopic colon resection

Answer 49

Benefits:
- ***similar oncological outcome to open
- less pain
- shorter duration of ileus
- quicker recovery
- less inflammatory response
- shorter hospital stay

Disadvantages:
- expensive instrument
- longer operating time
- technically more difficult

Question 50

***Complications of CRC surgery

Answer 50

General:
1. Cardiopulmonary
2. DVT, PE —> Early mobilisation
3. Infections —> Early feeding + remove catheter early
- Wound
- Pneumonia
- Urinary tract
- Phlebitis

Acute:
1. Bleeding
- **Splenic injury
- Injury to major vessels (uncommon)
2. Injury to neighbouring structures (rare now)
- **Ureter (left side cancer)
- ***Duodenum (hepatic / splenic flexure)
- Spleen (splenic flexure)

Late:
1. **Anastomotic leakage +/- Intra-abdominal abscess / collection
- Tumour factors
—> Sites of anastomosis (colon vs rectum (higher risk esp. extraperitoneal anastomosis))
—> Timing of operation (emergency (no bowel prep) vs elective)
- Patient factors
—> Comorbidities affect healing
—> Steroid, medication affect healing
- Surgeon factors
—> No tension
2. **Prolonged ileus
3. ***Intestinal obstruction (Adhesive IO)

Question 51

***Surgery for Rectal cancer

Answer 51

Principles:
1. Adequate **circumferential margin (e.g. **Total mesorectal excision —> presence of radial spread determine **prognosis)
2. **Narrow distal margin (2 cm) is adequate provided mesorectal dissection is performed (∵ aim to preserve anal sphincter (different from colon surgery))
3. **Sphincter preservation
4. **Autonomic nerve preservation (e.g. bladder, sexual function)

Treatment:
1. **Anterior resection (aka Low anterior resection)
2. **Abdominoperineal resection
3. ***Hartmann’s operation (resection +/- anastomosis)
- Temporary (2 stage) / Permanent
- Temporary: Emergency situation when a primary anastomosis is not safe
- Permanent: Patients with poor sphincter function + do not want low anorectal anastomosis ∵ associated with bowel problems)
4. Local excision (for very early disease, different approaches)

Preparation for rectal cancer surgery:
1. Medical consultation if necessary
2. Mechanical bowel preparation (Controversial)
3. Prophylactic IV antibiotics
4. ***Prophylaxis against DVT (∵ prolonged operation + operation in pelvis)
- Mechanical: Stocking
- Pharmacological: Anticoagulant
5. Consultation to enterostomal therapist and marking of stoma sites

Question 52

Determinants of sphincter preservation

Answer 52

Tumour factor:
1. ***Level of tumor (most important)
2. Position and fixity of tumor
3. Differentiation (poorer differentiation —> want to obtain a more distal mural margin)

Patient factor:
1. Body build
2. Gender (female: wider pelvis —> easier dissection)

Surgeon factor:
1. Technique and experience

Question 53

Anterior resection

Answer 53

• More common now than APR (∵ better anastomotic technique)
• **Resection of rectum + **Colorectal anastomosis (連接番肛門)
• Lower anterior resection: mobilisation down to distal rectum and anastomosis at the level below the peritoneal reflexion

Question 54

Abdominoperineal resection

Answer 54

• For very distal rectal cancer (<5 cm from anal verge)
• Synchronous **abdominal + **perineal resection
• ***Permanent colostomy
• Less used with better techniques in sphincter preservation

Question 55

***Complications of Rectal surgery

Answer 55

General:
1. Cardiopulmonary
2. DVT, PE —> Early mobilisation
3. Infections —> Early feeding + remove catheter early
- Wound (**perineal wound, RT can also impair healing)
- Pneumonia
- Urinary tract (associated with **urine retention)

Acute:
1. Bleeding
- **Splenic injury (∵ splenic fluexure mobilisation)
- Pre-sacral venous plexus
2. Injury to neighbouring structures (higher risk than Colon surgery)
- Ureter
- **Urethra
- ***Bladder
- Spleen

Late:
1. **Anastomotic leakage +/- Intra-abdominal abscess
- **high risk ∵ distal + extraperitoneal
- depends on level of anastomosis (<5% for high anterior resection, ~10% with low anterior resection)
—> **Proximal diversion by loop colostomy / loop ileostomy
2. **Prolonged ileus
3. **Intestinal obstruction
4. Urinary retention
5. **Sexual dysfunction
6. ***Bowel disturbance (anterior resection: LAR syndrome)
- Incontinence
- Clustering of bowel movement
- Urgency

Stoma-related (permanent/ temporary):
1. Ischaemia
2. Retraction
3. Prolapse
4. Skin problem
5. Parastomal hernia

Question 56

Adjuvant vs Neoadjuvant therapy

Answer 56

Adjuvant:
1. **Reduces local recurrence
2. **Improves survival

Options:
1. Chemo + RT

Current:
**Neoadjuvant ChemoRT preferred:
1. **Less toxicity
2. ***Downstage tumour (convert sphincter losing to sphincter saving surgery)
- Regime of RT
—> long course ChemoRT: 5-6 weeks (wait another 8-10 weeks for surgery for downstaging)
—> short course RT: 1 week

Complications:
1. Radiation cystitis
2. Radiation proctitis

Question 57

Advanced disease

Answer 57

Liver metastasis
1. ***Curative resection
- Absence of extra hepatic disease
- Location + Number of metastasis (anatomical resection not necessary)
- Hepatic reserve
- Synchronous vs Sequential resection with Colon surgery

2. ***Ablative therapy
   - RFA
   - Cryosurgery
   - Alcohol injection
   - Etc.
3. Palliative chemotherapy
   - ***Systemic (Chemotherapy, Targeted, Immunotherapy)
   —> Hepatic arterial infusion
   —> Embolisation

Question 58

Prognosis of CRC

Answer 58

5-year survival:
Stage 1: 80-100%
Stage 2: 60-80%
Stage 3: 30-50%
Stage 4: 10%