---

How to Score Full Marks (25/25)

1. Definition + Classification (2-3 marks) - always start here
2. Pathophysiology (3-4 marks) - the "why" behind the signs
3. Clinical features (4-5 marks) - use the comparison table
4. Investigations (3-4 marks) - name the gold standard first
5. Management (5-6 marks) - operative + non-operative
6. Diagram (2-3 marks) - even a rough but labelled diagram gets marks

• Dukes' staging - transverse bowel section with layers
• Intussusception components - the three-layer telescoping diagram
• Meckel's diverticulum - antimesenteric position with Rule of 2s
• Sigmoid volvulus X-ray - omega loop / coffee bean

• Sign of Dance, redcurrant jelly stool, Ladd's procedure, ileosigmoid knotting (compound volvulus), ICV competence in LBO, Tc-99m scan for Meckel's bleeding - these details show you read the textbook, not just memorized lists.

---

COMPLETE DISTINCTION-LEVEL NOTES

Intestinal Obstruction, Volvulus, Small & Large Bowel Pathology, Meckel's Diverticulum, Malrotation, Intussusception, Ca Caecum & Ca Colon

Final MBBS Examination - 25 Marks

---

---

SECTION 1: INTESTINAL OBSTRUCTION

Definition

---

Classification

┌─────────────────────────────────────────────────────┐
│            INTESTINAL OBSTRUCTION                    │
│                                                      │
│        DYNAMIC                 ADYNAMIC              │
│      (Mechanical)            (Functional)            │
│           |                       |                  │
│      ┌────┴────┐            ┌─────┴──────┐           │
│    Acute    Chronic    Paralytic    Pseudo-           │
│                           ileus   obstruction        │
└─────────────────────────────────────────────────────┘

• Paralytic ileus (postoperative, sepsis, metabolic)
• Pseudo-obstruction (Ogilvie's syndrome)

---

Pathophysiology

1. Proximal bowel dilates; distal bowel collapses and empties
2. Initially peristalsis increases (trying to overcome the block) → produces colicky pain and high-pitched bowel sounds
3. If unrelieved → flaccidity → paralysis → silent abdomen
4. Two sources of distension:
   • Gas (90% nitrogen + H₂S) from aerobic and anaerobic bacterial overgrowth
   • Fluid accumulation: saliva (500 mL) + bile (500 mL) + gastric juice (500 mL) + pancreatic + intestinal secretions = massive third-space fluid loss → dehydration + electrolyte imbalance
5. Strangulation = vascular compromise → ischaemia → gangrene → perforation → peritonitis → death
   • Closed-loop obstruction (both ends of loop blocked) → most rapid strangulation
   • ICV competence is critical: competent valve → closed loop in LBO → caecal distension → perforation risk when caecum ≥12 cm

---

Cardinal Clinical Features

╔═══════════════════════════════════════════════════════╗
║         THE QUARTET (Bailey Summary Box 78.7)         ║
║                                                       ║
║  1. PAIN            Colicky; umbilical (SBO),         ║
║                     lower abdomen (LBO)               ║
║                                                       ║
║  2. VOMITING        Early & bilious (high SBO),       ║
║                     faeculent (low SBO),              ║
║                     late/absent (LBO)                 ║
║                                                       ║
║  3. DISTENSION      Central (SBO);                    ║
║                     peripheral/flanks (LBO)           ║
║                                                       ║
║  4. ABSOLUTE        Neither flatus nor faeces passed  ║
║     CONSTIPATION                                      ║
╚═══════════════════════════════════════════════════════╝

Detailed Comparison: SBO vs LBO

---

Signs of Strangulation (SURGICAL EMERGENCY - Do not delay)

BEWARE STRANGULATION - signs to watch:
• Continuous severe pain (not relieved by IV opiates)
• Tenderness localised → peritonism → rigidity
• Pyrexia, tachycardia
• SHOCK (hypotension)
• In hernia: tense, tender, irreducible lump;
  NO cough impulse; skin erythema / purplish discolouration

---

Investigations

Radiological Features (Bailey Summary Box 78.9)

X-RAY IDENTIFICATION:
┌────────────────────────────────────────────────────┐
│ JEJUNUM: Valvulae conniventes                      │
│          ← completely cross full width →           │
│          Regular spacing; "concertina/ladder"      │
│          Central in abdomen                        │
├────────────────────────────────────────────────────┤
│ ILEUM:   Featureless (distal)                      │
├────────────────────────────────────────────────────┤
│ COLON:   Haustral folds                            │
│          Do NOT cross full width                   │
│          Irregularly spaced                        │
│          No opposite indentations                  │
│          Peripheral in abdomen                     │
└────────────────────────────────────────────────────┘

---

Treatment

The Three Main Measures (Bailey Summary Box 78.11)

╔══════════════════════════════════════════════════╗
║    TREATMENT OF ACUTE INTESTINAL OBSTRUCTION     ║
║                                                  ║
║  1. NGT → Gastrointestinal drainage              ║
║     (Ryle's tube or Salem sump;                  ║
║      free drainage + 4-hourly aspiration)        ║
║                                                  ║
║  2. IV fluids + electrolytes                     ║
║     (Hartmann's solution; correct Na+ and K+     ║
║      losses; monitor urine output)               ║
║                                                  ║
║  3. RELIEF OF OBSTRUCTION                        ║
║     (surgical or non-operative)                  ║
║                                                  ║
║  Surgery delayed until resuscitation complete    ║
║  UNLESS: strangulation or closed-loop suspected  ║
╚══════════════════════════════════════════════════╝

Principles of Surgical Intervention (Bailey Summary Box 78.12)

1. Manage the segment at the site of obstruction
2. Manage the distended proximal bowel (decompression)
3. Manage the underlying cause

---

Adynamic Obstruction

Paralytic Ileus (Bailey Ch. 78)

• No bowel sounds on auscultation
• No passage of flatus

1. NGT suction + nil by mouth until bowel sounds/flatus return
2. Correct electrolytes (especially K⁺)
3. Treat underlying cause
4. ERAS (Enhanced Recovery After Surgery) protocols - early oral fluids

Pseudo-obstruction (Ogilvie's Syndrome)

• Predominantly large bowel dilation without mechanical obstruction
• Causes: opiates, anticholinergics, spinal injury, retroperitoneal pathology
• AXR: massive colonic dilation (especially caecum)
• Danger: Caecal perforation when diameter >12 cm
• Treatment: colonoscopic decompression first; neostigmine (IV, 2 mg); if fails → caecostomy

---

---

SECTION 2: VOLVULUS

Definition

• 180° torsion = luminal obstruction

• 360° torsion = vascular occlusion (ischaemia/gangrene)

• Bacterial fermentation adds to distension; rising intraluminal pressure impairs capillary perfusion; mesenteric veins thrombose → ischaemia

Types

Primary vs Secondary

• Primary: congenital malrotation, abnormal mesenteric attachments, congenital bands (e.g. volvulus neonatorum, caecal volvulus)
• Secondary (more common): rotation around acquired adhesion or stoma

---

Sigmoid Volvulus

Predisposing factors

SIGMOID VOLVULUS - PREDISPOSING ANATOMY (Bailey Fig. 78.7):

    ┌────────────────────────────────────┐
    │  1. LONG pelvic mesocolon          │
    │  2. OVERLOADED pelvic colon        │
    │     (high-residue diet/constipation│
    │  3. BAND of adhesions at base      │
    │     tethering the two limbs        │
    └────────────────────────────────────┘
                    ↓
          Sigmoid twists anticlockwise
                    ↓
          ┌──────────────────────┐
          │   OMEGA LOOP forms   │
          └──────────────────────┘

Clinical Presentation

• Fulminant: sudden onset, severe pain, early vomiting, rapid deterioration
• Indolent: insidious onset, slow progression, less pain (more common in elderly)
• Early, progressive abdominal distension (may be visible through abdominal wall)
• Absolute constipation; hiccough/retching

Radiology

AXR APPEARANCES OF SIGMOID VOLVULUS:

SUPINE AXR:                      BARIUM ENEMA:
                                 
    ╱╲  Massively dilated         "BIRD'S BEAK"
   ╱  ╲  sigmoid loop             or "ACE OF SPADES"
  ╱    ╲  running diagonally      deformity at
 ╱  OMEGA╲  from RIGHT → LEFT     the twist
╱   LOOP   ╲                     
━━━━━━━━━━━━━━
PELVIS
                                 
"Coffee bean sign"               Bird's beak
Two fluid levels                 deformity
(one in each limb)               (if erect)

Treatment

SIGMOID VOLVULUS TREATMENT:

Step 1: Resuscitate (IV fluids, NGT)
Step 2: SIGMOIDOSCOPE / FLATUS TUBE per anum
        → decompresses >80% of cases
        → pass tube through twist; a gush of gas = success
Step 3: Elective surgery (after 48-72h, when patient optimised)
        → Hartmann's procedure (resect + end colostomy)
        OR
        → Sigmoid colectomy + primary anastomosis
           (if bowel viable + patient fit)

IF gangrenous / peritonitis at presentation:
        → IMMEDIATE surgery (Hartmann's procedure)

---

Caecal Volvulus

• Usually a clockwise twist; more common in females in 4th-5th decades
• Caecum twists → displaced to left upper quadrant
• May be partial initially (passage of flatus/faeces possible early)
• 25% → palpable tympanic swelling in midline or left abdomen
• Ischaemia common; diagnosis rarely made preoperatively

---

Compound Volvulus (Ileosigmoid Knotting)

• Rare; ileum twists around sigmoid colon
• Long pelvic mesocolon allows ileum to knot around sigmoid
• Gangrene of either or both bowel segments
• AXR: distended ileal loops within distended sigmoid colon
• Treatment: decompression + resection + anastomosis (both segments often need resection)

---

---

SECTION 3: SMALL INTESTINAL PATHOLOGY

A. Small Bowel Obstruction

B. Small Bowel Strictures

• TB and Crohn's disease - most common causes
• Malignant (lymphoma - uncommon; carcinoma/sarcoma - rare)
• Presentation: subacute or chronic
• Treatment:
  • Resection + anastomosis (preferred)
  • Strictureplasty for multiple short strictures in Crohn's (preserves bowel length)

C. Adhesions

• Most common cause of SBO (60%)
• From previous surgery, infection, or peritoneal inflammation
• First episode: non-operative management with "drip and suck" (success ~70%)
• Failure or strangulation: laparoscopic or open adhesiolysis
• Recurrent obstruction from adhesions: repeat adhesiolysis ± Noble's plication

D. Paralytic Ileus and Pseudo-obstruction

---

---

SECTION 4: MECKEL'S DIVERTICULUM

The Rule of 2s

╔═════════════════════════════════════════════════════╗
║              MECKEL'S RULE OF 2s                    ║
║                                                     ║
║  • 2% of the population                             ║
║  • 2 feet (60 cm) from the ileocaecal valve         ║
║  • 2 inches (5 cm) long                             ║
║  • 2x more common/symptomatic in MALES              ║
║  • 20% contain heterotopic mucosa                   ║
║    (gastric, colonic or pancreatic)                 ║
╚═════════════════════════════════════════════════════╝

Anatomy (Diagram - Draw this in the exam)

       UMBILICUS
           │
    fibrous band (remnant of
    vitello-intestinal duct)
           │
     ┌─────┴──────┐
     │  MECKEL'S  │ ← 5 cm (2 inches) long
     │DIVERTICULUM│ ← TRUE diverticulum (all 3 coats)
     │            │ ← own blood supply (vitelline artery)
     └──────┬─────┘
            │
────────────┴─────────────────────── ILEUM
            ←────60 cm (2 feet)────→ ICV

(Arises from ANTIMESENTERIC border of ileum)

Nature

• True diverticulum (all three layers: mucosa, muscularis propria, serosa)
• Arises from antimesenteric border of ileum
• Persistent remnant of the vitello-intestinal (omphalomesenteric) duct
• Has its own blood supply (persistent vitelline artery)
• 20% contain heterotopic mucosa (gastric > colonic > pancreatic)
• Heterotopic mucosa (especially gastric) predisposes to complications

Complications (Mnemonic: HOBIP)

Diagnosis

• Tc-99m pertechnetate scan - investigation of choice for bleeding Meckel's (detects gastric mucosa)
• CT scan + CT enterography
• Capsule endoscopy / enteroscopy
• Laparoscopy (gold standard for definitive diagnosis)

Treatment

TREATMENT OF MECKEL'S DIVERTICULUM:

SYMPTOMATIC (bleeding/obstruction/inflammation):
→ MECKEL'S DIVERTICULECTOMY
  (excision with wedge of ileal wall at the base
   OR segmental ileal resection if base is wide/indurated)

INCIDENTAL FINDING AT SURGERY:
→ CHILD: RESECT (lifetime risk of complications > risk of surgery)
→ ADULT: Generally LEAVE (risk-benefit ratio usually favours
          non-intervention unless inflammation, narrow neck,
          palpable heterotopic tissue or abnormal appearance)

KEY: When normal appendix found at surgery for
     "appendicitis" → ALWAYS look for Meckel's diverticulum
     (examine 60 cm of terminal ileum)

---

---

SECTION 5: MALROTATION

Embryology

• Normal gut undergoes 270° anticlockwise rotation around the superior mesenteric artery (SMA) during fetal development (weeks 6-12)
• This creates a broad, stable mesenteric base running from the DJ flexure (left upper quadrant) → caecum (right lower quadrant)
• Malrotation = incomplete rotation → narrow, unstable mesenteric base → risk of midgut volvulus

Ladd's Bands

• Fibrous peritoneal bands from a central/upper abdominal caecum to the right lateral abdominal wall
• These bands cross and compress the duodenum, causing duodenal obstruction

DIAGRAM (Draw in exam)

NORMAL vs MALROTATION:

NORMAL ROTATION:              MALROTATION:

DJ flexure (LUQ)              DJ flexure (midline/right)
     \                               |
      \  Broad, stable               | Narrow, unstable
       \  mesenteric base            | mesenteric base
        \                           /
    Caecum (RIF)              Caecum (central/upper)
                               + Ladd's bands crossing
                                 duodenum
                               + Risk of MIDGUT VOLVULUS

Result: STABLE                 Result: LIFE-THREATENING

Clinical Presentations

GOLD RULE: Any neonate vomiting bile = midgut volvulus until proved otherwise - this is a surgical emergency.

Investigations

• Upper GI contrast study: The DJ flexure should lie to the LEFT of the vertebral column at the level of the pylorus (stable). If central or right-sided → malrotation confirmed.
• USS: "Whirlpool sign" of SMA/SMV (vessels wrap around each other)
• AXR: Gasless abdomen (ischaemic midgut); dilated duodenal loop; scaphoid abdomen
• Acidotic baby vomiting bile with gasless AXR = IMMEDIATE LAPAROTOMY without further imaging

Treatment: Ladd's Procedure

LADD'S PROCEDURE (Steps):

1. REDUCE VOLVULUS (untwist anticlockwise)
          ↓
2. ASSESS BOWEL VIABILITY
   (warm saline packs; reassess at 2nd look if uncertain)
          ↓
3. DIVIDE LADD'S BANDS (relieve duodenal compression)
          ↓
4. BROADEN MESENTERIC BASE
   (separate duodenum from ascending colon)
          ↓
5. REPOSITION: Small bowel on RIGHT side
              Large bowel on LEFT side
              (non-rotated position - most stable)
          ↓
6. APPENDICECTOMY
   (caecum now in LUQ - avoids diagnostic confusion)
          ↓
7. If infarcted bowel: RESECT non-viable segments
   ± "SECOND-LOOK" LAPAROTOMY at 24-48 hours
    (if viability of remaining bowel in doubt)

---

---

SECTION 6: INTUSSUSCEPTION

Definition

DIAGRAM - Draw this (distinction marks guaranteed)

INTUSSUSCEPTION - COMPONENTS:

←──── Direction of advance ────

┌─────────────────────────────────────────────────┐
│  OUTER TUBE = INTUSSUSCIPIENS (sheath)           │
│  ┌───────────────────────────────────┐           │
│  │  MIDDLE TUBE (returning layer)    │           │
│  │  ┌─────────────────────────────┐  │           │
│  │  │  INNER TUBE = INTUSSUSCEPTUM│  │           │
│  │  │  ──────────── LEAD POINT ►  │  │           │
│  │  └─────────────────────────────┘  │           │
│  └───────────────────────────────────┘           │
└─────────────────────────────────────────────────┘
        NECK                  APEX

3 layers: 
• Entering/inner tube = INTUSSUSCEPTUM (the invaginated part)
• Returning/middle tube
• Sheath/outer tube = INTUSSUSCIPIENS (the receiving part)

Ischaemia occurs at the NECK (where it's tightest)
Most constriction is at the ILEOCAECAL VALVE

Types (Bailey Table 78.2, after RE Gross, n=702 children)

Age and Lead Points

Clinical Features

CLASSIC PRESENTATION OF INTUSSUSCEPTION IN INFANT:

Previously healthy MALE infant (2-12 months)
                ↓
SUDDEN COLICKY PAIN → screaming, draws up legs,
                       becomes PALE
                ↓
Between episodes: initially appears well / listless
                ↓
BILIOUS VOMITING (develops later)
                ↓
"REDCURRANT JELLY" STOOL
(blood + mucus = LATE sign → indicates gangrene!)
                ↓
ON EXAMINATION (between episodes):
• Abdomen not initially distended
• Sausage-shaped mass in RUQ (60% of cases)
• SIGN OF DANCE = EMPTINESS in RIF
  (caecum has migrated into the intussusception)
• PR exam → blood-stained mucus on finger
• Apex may protrude from anus (extensive colocolic)

Investigations

• Abdominal USS - "Target sign" / "Doughnut sign" - pathognomonic (concentric rings of bowel)
• CT scan - "Target sign" (Figure 78.6, Bailey) - also good for adults
• Plain AXR - SBO pattern; mass in RUQ; paucity of gas in RIF

Treatment Algorithm

MANAGEMENT OF INTUSSUSCEPTION:

STEP 1: RESUSCITATION
        IV fluids + broad-spectrum antibiotics + NGT
                    ↓
STEP 2: ASSESS CONTRAINDICATIONS to non-operative reduction:
        • Peritonitis?    →  YES → SURGERY
        • Perforation?    →  YES → SURGERY  
        • Profound shock? →  YES → SURGERY
        • Known pathological lead point? → YES → SURGERY
                    ↓ (if NO to all)
STEP 3: NON-OPERATIVE REDUCTION
        AIR ENEMA (preferred) or barium enema
        → Success = air/barium freely refluxes into small bowel
          AND symptoms/signs resolve
        → SUCCESS RATE: >70%
        → Colonic perforation during pneumatic reduction: rare
                    ↓
STEP 4: IF NON-OPERATIVE FAILS OR CONTRAINDICATED:
        SURGERY (open or laparoscopic)
        → Transverse right-sided abdominal incision
        → Reduce by COMPRESSING distal end towards origin
          (DO NOT PULL the intussusceptum out)
        → Last part of reduction is hardest (tightest at ICV)
                    ↓
STEP 5: IF IRREDUCIBLE / GANGRENOUS / PATHOLOGICAL LEAD POINT:
        RESECTION (e.g. right hemicolectomy for ileocolic)

RECURRENCE: 5-10% after non-operative reduction

---

---

SECTION 7: CARCINOMA OF THE CAECUM AND COLON

Epidemiology (Bailey, p.1380)

• In UK: 2nd most common cause of cancer death
• ~42,000 new cases/year in UK
• Colon (67%): caecum 12%, ascending 5%, transverse 5.5%, sigmoid 21%
• Rectum (33%)
• Males > Females (56% vs 44%)
• Peaks in 8th decade; emergency presentation in 20% (worse prognosis)

The Adenoma-Carcinoma Sequence (Bailey Summary Box 77.4)

ADENOMA → CARCINOMA SEQUENCE (Fearon-Vogelstein model):

Normal epithelium
        ↓  APC gene mutation (2/3 of colonic adenomas)
Early adenoma
        ↓  K-ras mutation (larger adenomas)
Late adenoma (↑ dysplasia)
        ↓  p53 mutation (marker of invasion)
Carcinoma (invasive)

Evidence for this sequence:
• Distribution of adenomas = distribution of cancers (70% left-sided)
• Larger adenomas more likely to be dysplastic
• 1/3 of resected cancer specimens contain adjacent adenoma
• Screening colonoscopy + polypectomy reduces cancer incidence

Aetiology / Risk Factors

RISK FACTORS FOR COLORECTAL CANCER:

DIETARY:     ↑ Red/processed meat (haem + N-nitroso compounds)
             ↓ Fibre → ↑ colonic transit time → ↑ carcinogen exposure
             ↑ Alcohol
             ↓ Aspirin/NSAIDs (protective - COX-2 inhibition)

GENETIC:     FAP (APC gene) - 100% lifetime risk without surgery
             Lynch syndrome (HNPCC) - 80% lifetime risk
               → MLH1, MSH2, MSH6, PMS2 mutations
               → Microsatellite instability (MSI)
               → Proximal colon predominance
             Family history of CRC (1st degree relative <50y)

PRE-MALIGNANT: Adenomatous polyps (villous > tubular)
               Long-standing UC (>10y, pancolitis - 30x risk)
               Crohn's colitis

LIFESTYLE:   Obesity, sedentary, smoking, type 2 diabetes

Lynch Syndrome (HNPCC) - Amsterdam II Criteria (Bailey Summary Box 77.3)

• ≥3 family members with Lynch-related cancer (CRC, endometrial, small bowel, ureter, renal pelvis)
• ≥2 successive generations affected
• ≥1 diagnosed before age 50 years
• FAP excluded; pathological confirmation of tumours
• Lifetime CRC risk: 80%; endometrial risk: 30-50% in females
• Surveillance: 2-yearly colonoscopy from age 25 (MLH1/MSH2) or 35 (MSH6/PMS2)

---

Pathology (Bailey, p.1380)

• Macroscopic forms:
  • Annular (napkin ring) → obstructive symptoms
  • Ulcerating → presents with bleeding
  • Polypoid → less obstructive
• Microscopy: Columnar cell adenocarcinoma
• Distribution: Rectum 38%, sigmoid 21%, caecum 12%, ascending 5%, transverse 5.5%, descending 4%

---

Spread of Colorectal Cancer (Bailey, p.1380)

ROUTES OF SPREAD:

1. LOCAL (DIRECT)
   • Radial: retroperitoneal (ureter, duodenum, posterior muscles)
             intraperitoneal (adjacent organs, anterior wall)
   • Longitudinal: 1-2 cm beyond gross tumour (excision margin)

2. LYMPHATIC
   • Pericolic nodes → intermediate nodes → central/aortic nodes
   • Follows course of blood supply (SMA for right colon,
     IMA for left colon)

3. HAEMATOGENOUS (via portal vein)
   • LIVER - 1/3 have liver mets at diagnosis
            - 50% develop mets eventually
   • Then: LUNG, bone, brain, ovary

4. TRANSPERITONEAL (TRANSCOELOMIC)
   • Peritoneum, omentum, ovary (Krukenberg tumour)
   • Indicates incurability

5. IMPLANTATION
   • Anastomotic recurrence
   • Port-site recurrence (laparoscopy)

---

Staging

Dukes' Classification (Bailey Summary Box 77.5)

DUKES' STAGING (DRAW THIS CROSS-SECTION):

┌─────────────────────────────────────────────────────┐
│ BOWEL LUMEN                                          │
├─────── Mucosa ──────────────────────────────────────┤ ←─┐
├─────── Submucosa ───────────────────────────────────┤   │ Dukes A
├─────── Muscularis propria ──────────────────────────┤ ←─┘ (confined to/not
│        ↑ Dukes A: invasion but NOT breaching this   │      breaching muscularis)
├─────── Serosa / Pericolic fat ──────────────────────┤ ←── Dukes B (beyond
│                                                      │     muscularis; NO nodes)
│   ○ Regional lymph node ────────────────────────────│ ←── Dukes C (nodes +ve)
│                                                      │     C1: apical node -ve
│                                                      │     C2: apical node +ve
│   LIVER / LUNG (distant metastasis) ────────────────│ ←── Dukes D (metastases)
└─────────────────────────────────────────────────────┘
   (Note: Dukes never described stage D himself)

TNM Classification (Bailey Summary Box 77.6 - UICC 8th edition)

---

Clinical Features (Bailey, p.1381)

SITE-DEPENDENT PRESENTATION:

RIGHT COLON (Caecum / Ascending colon):
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
  • IRON DEFICIENCY ANAEMIA (occult blood loss)
    → fatigue, pallor, breathlessness
  • RIF MASS (palpable in ~25% at diagnosis)
  • Dull, aching pain RIF (may mimic appendicitis)
  • Weight loss
  • LATE obstruction (liquid faeces + wide lumen
    → presents late)
  • Can present with perforation or appendix-like picture

LEFT COLON (Descending / Sigmoid):
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
  • CHANGE IN BOWEL HABIT
    (alternating constipation + diarrhoea)
  • Rectal bleeding (bright red blood ± mucus)
  • Colicky left iliac fossa pain
  • EARLY obstruction (solid faeces + narrow lumen)
  • "Apple core" / "napkin ring" on barium enema

RECTUM:
━━━━━━━
  • Rectal bleeding (fresh blood)
  • Tenesmus (feeling of incomplete evacuation)
  • Mucus discharge PR
  • Altered bowel habit

GENERAL (any site):
━━━━━━━━━━━━━━━━━━━
  • Weight loss, anorexia
  • Anaemia
  • Abdominal mass
  • Perforation → peritonitis (emergency)
  • Obstruction (20% emergency presentation)

---

Investigations (Bailey Ch. 77)

---

Surgical Treatment

OPERATION BY SITE (Bailey Ch. 77):

   Caecum / Ascending colon
         ↓
   RIGHT HEMICOLECTOMY
   (ligate ileocolic artery + right colic artery
    close to SMA origin - "high-tie" / CME)
   Anastomosis: ileum-to-transverse colon

   Hepatic flexure / Transverse colon
         ↓
   EXTENDED RIGHT HEMICOLECTOMY
   (divide right branch of middle colic artery)
   Anastomosis: ileum-to-descending colon

   Splenic flexure
         ↓
   EXTENDED RIGHT HEMICOLECTOMY
   OR LEFT HEMICOLECTOMY

   Descending colon
         ↓
   LEFT HEMICOLECTOMY
   (ligate left colic artery from IMA)

   Sigmoid colon
         ↓
   SIGMOID COLECTOMY / HIGH ANTERIOR RESECTION

   Upper rectum
         ↓
   ANTERIOR RESECTION (with anastomosis)

   Lower rectum
         ↓
   LOW ANTERIOR RESECTION (±covering loop ileostomy)
   OR
   ABDOMINOPERINEAL RESECTION (APR)
   → permanent end colostomy

• High ligation of vessels at origin from SMA/IMA
• Sharp dissection along embryological planes
• Removes entire mesocolic envelope
• Improves survival in node-positive disease (Hohenberger principle)

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Emergency Presentation: Obstructing Colorectal Cancer

TREATMENT OF ACUTE LARGE BOWEL OBSTRUCTION
(Bailey Ch. 78, Summary Box - Ch. 77):

Resuscitation → midline incision → assess

RIGHT COLON LESION (caecum, ascending, hepatic flexure):
→ Emergency RIGHT HEMICOLECTOMY
→ Primary anastomosis safe if patient condition reasonable

SPLENIC FLEXURE LESION:
→ Extended right hemicolectomy
   + ileo-descending colonic anastomosis

LEFT COLON / RECTOSIGMOID LESION:
→ Option 1: HARTMANN'S PROCEDURE
   (resect tumour + end colostomy + rectal stump)
   Reversal later (if fit)

→ Option 2: On-table lavage + primary anastomosis
   (if viable bowel + experienced surgeon)

→ Option 3: COLONIC STENT
   (self-expanding metallic stent, SEMS)
   - "Bridge to surgery" in fit patients
   - Palliative in unfit/metastatic patients

UNRESECTABLE LESION:
→ Proximal colostomy / ileostomy (if ICV incompetent)
   OR ileotransverse bypass (palliative)

CAECAL PERFORATION IMMINENT (caecum >12 cm):
→ Emergency caecostomy or loop transverse colostomy
   (to "buy time" for resuscitation before definitive surgery)

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Adjuvant and Palliative Therapy (Bailey, p.1383-1385)

ADJUVANT CHEMOTHERAPY:
Stage II (Dukes B): FOLFOX (5-FU + leucovorin + oxaliplatin)
                    - Benefit uncertain; offered selectively
Stage III (Dukes C): FOLFOX → improves 5y DFS by ~20% (to 67-70%)

METASTATIC DISEASE - FIRST LINE:
FOLFIRI (5-FU + leucovorin + irinotecan)
± BEVACIZUMAB (anti-VEGF monoclonal antibody)

SECOND LINE (KRAS wild-type):
CETUXIMAB or PANITUMUMAB (anti-EGFR)

MSI-HIGH tumours:
PEMBROLIZUMAB (immunotherapy - PD-1 inhibitor)

BRAF V600E mutation (~10%):
ENCORAFENIB (BRAF inhibitor) + BINIMETINIB (MEK inhibitor)

LIVER METASTASES:
- 1/3 present at diagnosis; 50% develop at some point
- Resectable mets → surgical resection (potentially curative)
- Chemotherapy ± downsizing → "convert to resectable"
- Ablation (radiofrequency, microwave) for small/peripheral mets

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Prognosis (Bailey, p.1384)

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Colorectal Cancer Follow-up (Bailey, p.1385)

• 3% have synchronous bowel tumours (missed at original diagnosis)
• 3% develop metachronous colonic cancer
• 50% develop liver metastases at some point
• NICE guidelines: CT chest/abdomen/pelvis + CEA measurement during first 3 years after curative treatment

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GIST and Carcinoid (Bailey, p.1385-1386)

• GIST: Arise from interstitial cells of Cajal; c-kit mutation; 30% malignant; treat with surgical resection ± imatinib (targeted therapy)
• Carcinoid: Well-differentiated neuroendocrine tumours; appendix most common site; may cause carcinoid syndrome if liver mets

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MASTER SUMMARY TABLE

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EXAM DIAGRAMS - QUICK REFERENCE SHEET

Diagram A: Intussusception (three-layer)

Diagram B: Meckel's Diverticulum

Diagram C: Dukes' Staging Cross-section

Diagram D: Sigmoid Volvulus X-ray

Diagram E: Normal vs Malrotation Mesentery

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EXAM STRATEGY FOR 25/25

1. Structure your answer as: Definition → Classification → Pathophysiology → Clinical features → Investigations → Management → Prognosis
2. Draw at least 2 diagrams per question (label everything - examiner loves labelled diagrams)
3. Quote Bailey's summary boxes word-for-word - examiners recognize them
4. Include the "distinction details" that others miss: Auerbach's plexus, Sign of Dance, Tc-99m scan, ICV competence, CME (complete mesocolic excision), MSI, BRAF mutation therapy
5. Never miss strangulation signs in any obstruction question - it's always worth marks
6. In colorectal cancer, always mention Dukes AND TNM staging - use both
7. For Meckel's: write "Rule of 2s" as a bullet list - it's instant marks