Colorectal Surgery JC060: Intestinal Obstruction: Colorectal Cancer Flashcards
Questions to Intestinal obstruction
-
**Paralytic ileus vs **Mechanical obstruction
- Small bowel: Mechanical usually - Site + Cause of obstruction
- ***Small vs Large bowel - Simple / ***Strangulated (blood supply compromised)
- indication for surgery - What investigations
- Treatment
- conservative?
- duration - Indications for surgery
- Surgical options
***Intestinal obstruction
Mechanical obstruction:
- Physical barrier to aboral progress of intestinal contents
Paralytic ileus:
- Failure of peristalsis to propel intestinal contents with no mechanical barrier
***Causes of Paralytic ileus
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
Clinical features of Paralytic ileus
- Abdominal pain
- **Diffuse, Constant, Less severe (vs **Colicky pain in Mechanical obstruction) - Abdominal distension
- Vomiting
- Constipation
- **Sluggish / Absent bowel sound (vs **Hyperactive in Mechanical obstruction)
- Features associated with cause
- e.g. peritoneal signs in peritonitis
Mechanical bowel obstruction
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)
Clinical features of Mechanical obstruction
- ***Colicky pain (Gripping pain)
- if ischaemia —> Constant severe pain - Abdominal distension (depend on level of obstruction)
- upper level obstruction: less prominent distension
- colonic obstruction: ***more prominent distension - Vomiting
- upper level obstruction - Constipation
- ***Hyperactive bowel sounds
Severity of each symptom depends on the level of obstruction
History taking of Intestinal obstruction
- Previous episodes bowel obstruction
- Previous Abdominal / Pelvic ***operation
- History of **cancer / abdominal / pelvic **radiation —> damage to bowel
- History of Abdominal ***inflammatory condition
Physical examination
- General
- **Fever
- **Vital signs: Temp, BP, Pulse, RR
- ***Hydration status - Abdomen
- Distension (symmetrical / asymmetrical)
- Tenderness, Guarding, Rebound tenderness (Peritoneal signs)
- Mass (on deep palpation)
- **Bowel sound (hyperactive / hypoactive)
- **Hernia (cough impulse)
- Scars - Rectal + Vaginal examination (+ Urine dipstix + External genitalia)
***Investigations
- Bedside tests
- **Urinalysis (Urine R/M: UTI, Microscopic RBC)
- **Pregnancy test - 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) - 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?
- Endoscopy
- Colonoscopy
- Upper endoscopy
***Small bowel vs Large bowel obstruction
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
***Causes of Small bowel obstruction
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)
***Management decision
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
Features suggestive of Strangulation
- ***↑↑ Abdominal pain (Constant)
- ***Blood in vomitus
- **Fever, **↑ WBC
- 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)
- ***Adhesive obstruction
- 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
- ***Intussusception
- 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
***Non-operative treatment
- ***IV fluid + electrolytes + acid-base balance
- ***NG tube decompression
- ***Nil by mouth: Nutrition when prolonged fasting anticipated (Parenteral)
- Frequent monitor vital signs, abdominal signs, X-ray
***Operative treatment for Small bowel obstruction
-
**Enterolysis / **Adhesiolysis
- lysis of adhesions + release of constricting band - ***Hernia: Repair
- Foreign bodies (Bezoars, Gallstones)
- **Break down and milk down to colon
- **Enterotomy + removal - ***Bowel resection —> Anastomose with healthy bowel
- strangulation with gangrenous bowel
- unhealthy bowel
Clinical features of Resolution of Obstruction
- Less abdominal distension
- Reduction of NG output
- Passage of flatus + bowel movement
- 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%
***Colonic obstruction
- 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
- ***Extrinsic compression
- Metastasis
- Pelvic / Extraperitoneal tumour (e.g. PoD tumour)
(6. Faecal impaction
- Digital evacuation)
- ***Obstructing Colorectal cancer
- 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
-
**Sigmoidoscopy / Colonoscopy / Lower GI endoscopy
- **Diagnostic
- ***Therapeutic: Decompression in sigmoid volvulus + pseudo-obstruction, Stenting
- Cautions: avoid excessive insufflation of gas - 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
- Non-surgical treatment
- Insertion of metallic stent
Determinants of procedures
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
***Operative treatment of CRC
Right-sided obstruction: Caecum to Splenic flexure
1. Resection with Anastomosis (Ileocolic anastomosis)
- if patient stable (Right / Extended right colectomy)
- ***Resection without Anastomosis
- if patient / bowel condition not favourable - 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
- 3-stage operation (old fashioned, not commonly performed today):
- Transverse colostomy —> decompression
- Resection + Anastomosis
- Closure of colostomy - Hartmann’s operation
- Resection without anastomosis - 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
***Non-surgical treatment of CRC
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
- ***Volvulus of colon
- 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)
- ***Pseudo-obstruction (Ogilvie’s syndrome)
- 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
Summary
- 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
JC Interactive Tutorial: Intestinal obstruction
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
SpC Interactive tutorial: Intestinal obstruction
***Causes of of Small bowel obstruction
Classification according to Adhesion, External hernia, Virgin abdomen (∵ Management is different!!!)
- ***Adhesion
- Appendicectomy
- Colorectal surgery
- Cholecystectomy
- Gastroduodenal surgery
- Gynaecological surgery - ***External hernia (Give sedation —> Try reduce hernia at bedside —> Early elective surgery —> Emergency surgery)
- Inguinal hernia
- Femoral hernia
- Incisional hernia -
**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)
Investigations of Small bowel obstruction
- AXR
- **Dilated small bowel
- **Multiple air-fluid levels - CXR
- ***Aspiration pneumonia
- Atelectasis - CT scan
- Dilated proximal and collapsed distal small bowel
- **May identify the cause of obstruction
- **May detect bowel ischaemia (intramural gas suggesting impending perforation)
Management of Small bowel obstruction
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
***Causes of Large bowel obstruction
- ***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%) -
**Volvulus
- **Sigmoid (80%)
- Caecum
- Transverse colon
- Ileosigmoid knotting - ***Pseudo-obstruction
- Diverticular disease
- Inflammatory bowel disease
- Irradiation stricture
- Ischaemic stricture
- ***Faecal impaction (Treatment: Digital evacuation)
Investigations of Large bowel obstruction
- AXR
- **Distended large bowel +/- small bowel (depending on competence of ileocaecal valve)
- Colonic cut off point at level of obstruction
- **Multiple air-fluid levels - CXR
- **Aspiration pneumonia
- Atelectasis
- **Lung metastasis - Colonoscopy
- Localization of obstructive tumour
- **Exclude synchronous tumour / polyps distal to level of obstruction
- **Stenting - 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)
Management of Large bowel obstruction
- ***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 - 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
3 stage procedure
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
2 stage procedure
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
1 stage procedure
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%
Sigmoid volvulus
- 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
Pseudo-obstruction (Ogilvie’s syndrome)
- 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
SpC Interactive tutorial: Colorectal malignancy
Risk factors for CRC
- Age
- Race
-
**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) - ***Personal history of IBD (Crohn’s, UC)
- Type 2 DM
-
**Family history
- **Family history without polyposis syndrome
- **FAP
- **HNPCC
- Other polyposis syndrome (MYH-associated polyposis, Hamartoma polyposis) - Lifestyle
- **Diet
—> ↑ risk: Red meat, Processed meat, Fat
—> ↓ risk: Dietary fibres
- **Obesity
- Alcohol
- ***Smoking
- Lack of exercise
- Other dietary factors: Ca, Folate, NSAIDs
Pathogenesis of Sporadic cancer
-
**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 -
**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
Site distribution of CRC
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
Screening for CRC
Options:
1. Detect cancer
- Stool for occult blood
—> Guaiac based
—> Faecal immunochemical test
—> Stool for DNA
- 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)
***Clinical features of CRC
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)
***Investigations for CRC
- Blood tests (workup for surgery, chemo)
- Hb
- LRFT - 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 - 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 - CT, MRI, (USG), PET scan
- Extent of local disease
—> Determine Surgical options, Neoadjuvant therapy
- Distant metastasis
CT, MRI, PET scan for CRC
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
***Staging in CRC
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)
***Treatment for CRC
- 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
- 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)
***Surgery for CRC
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
Laparoscopic colon resection
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
***Complications of CRC surgery
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)
***Surgery for Rectal cancer
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
Determinants of sphincter preservation
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
Anterior resection
- 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
Abdominoperineal resection
- For very distal rectal cancer (<5 cm from anal verge)
- Synchronous **abdominal + **perineal resection
- ***Permanent colostomy
- Less used with better techniques in sphincter preservation
***Complications of Rectal surgery
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
Adjuvant vs Neoadjuvant therapy
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
Advanced disease
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
- ***Ablative therapy
- RFA
- Cryosurgery
- Alcohol injection
- Etc. - Palliative chemotherapy
- ***Systemic (Chemotherapy, Targeted, Immunotherapy)
—> Hepatic arterial infusion
—> Embolisation
Prognosis of CRC
5-year survival:
Stage 1: 80-100%
Stage 2: 60-80%
Stage 3: 30-50%
Stage 4: 10%
