The Vermiform Appendix - Bailey & Love's Short Practice of Surgery (28th Ed.), Chapter 76

EMBRYOLOGY

• Bailey and Love's Short Practice of Surgery, 28th Ed., Ch. 76

SURGICAL ANATOMY

Position of the Base

Positions of the Tip (Frequency)

1. Retrocaecal / retroileal - most common (~65%)
2. Pelvic / descending - 2nd most common (~31%)
3. Subcaecal / preileal
4. Pre-ileal
5. Right paracolic (extraperitoneal)
6. Left-sided (in situs inversus or malrotation)

Arteries

Veins

Lymphatics

Nerves

Microscopic Anatomy

• Average length: 7.5-10 cm; lumen is irregular with longitudinal folds
• Mucosa: columnar cell intestinal epithelium of colonic type with crypts
• Base of crypts: argentaffin (Kulchitsky) cells - precursors of neuroendocrine tumours (NETs)
• Submucosa: rich in lymphatic follicles

ACUTE APPENDICITIS

Epidemiology

• Most common cause of the acute abdomen in young adults
• Lifetime risk: 8.6% males, 6.7% females
• Peak incidence: teens and early 20s
• M:F ratio rises to 3:2 at age 25
• Relatively rare in infants; also less common after middle age

Aetiology

• No single unifying hypothesis; mixed aerobic and anaerobic bacterial proliferation
• Luminal obstruction is the main initiating event - by:
  • Faecolith (appendicolith) - most common
  • Lymphoid hyperplasia (especially in young adults after viral/GI infection)
  • Stricture, foreign body, rarely tumour
• Low dietary fibre / high refined carbohydrate diet is associated

Pathological Sequence

1. Obstruction → increased intraluminal pressure → mucosal ulceration
2. Bacterial invasion of wall → acute appendicitis (congestion, oedema, polymorphonuclear infiltrate)
3. Venous and lymphatic obstruction → ischaemia → gangrenous appendicitis
4. Full-thickness necrosis → perforation → local or generalised peritonitis

Risk Factors for Perforation

• Extremes of age (very young, elderly)
• Retrocaecal position (delayed diagnosis - "silent appendix")
• Faecolith obstruction
• Delay in presentation / diagnosis

Symptoms

• Central / periumbilical colicky pain - initial (visceral, T10 referred)
• Migration to RIF - somatic as parietal peritoneum is involved (hours later)
• Anorexia (almost invariable)
• Nausea and vomiting (after pain onset - contrast with gastroenteritis where vomiting precedes pain)
• Low-grade fever

Clinical Signs

• McBurney's point tenderness - point of maximum tenderness located 1/3 of the way along a line from ASIS to umbilicus
• Guarding and rigidity in RIF
• Rebound tenderness (Blumberg's sign) - peritoneal irritation
• Rovsing's sign - palpation of the left iliac fossa causes pain in the RIF (indicates peritoneal irritation)
• Psoas sign - pain on hyperextension of right hip (retrocaecal appendix on psoas)
• Obturator sign (Zachary Cope) - pain in hypogastrium when right hip is flexed and internally rotated (pelvic appendix)
• Low-grade fever (37.2-37.7°C typically); higher suggests perforation
• Pointing sign - patient locates maximal tenderness with one finger

Summary: Signs to Elicit

• Pointing sign
• Rovsing's sign
• Psoas sign
• Obturator sign

Position-Specific Features

CONDITIONS: ACUTE AND CHRONIC

Acute Appendicitis

Appendix Mass (Phlegmon)

• Based on premise that inflammation is already localised; surgery is difficult and dangerous
• IV antibiotics, fluid balance monitoring, 4-hourly pulse and temperature
• Mark limits of mass with skin pencil; contrast-enhanced CT
• Radiological drainage if abscess present
• Approximately 90% resolve without surgery

• Rising pulse rate
• Increasing or spreading abdominal pain
• Increasing size of the mass

Appendix Abscess

Recurrent / Chronic Appendicitis

• Rare; characterised by recurrent episodes of lower abdominal pain
• Arises from incomplete, self-limiting obstruction of the appendix lumen
• Attacks every few months; majority ultimately culminate in severe acute appendicitis
• Appendix is thickened with fibrosis from previous inflammation
• Many patients with acute appendicitis recall prior milder similar episodes

Appendicitis in Pregnancy

• Incidence: 0.5-1 per 1000 pregnancies; slightly more common in second trimester
• More likely to be complicated (perforated) when compared with non-pregnant
• Diagnosis difficult: early symptoms attributed to pregnancy; right lower quadrant pain remains the most common presentation (the classical upward displacement of the appendix is less dramatic than once thought)
• Requires surgical treatment regardless of trimester; laparoscopy is appropriate in first and second trimesters

Appendicitis in Special Groups

• Children: higher perforation rate; mesenteric adenitis and gastroenteritis are common differentials
• Elderly: higher perforation and complication rates; diagnose diverticulitis, malignancy
• Immunocompromised: atypical presentation, higher complication rates

DIFFERENTIAL DIAGNOSIS (Table 76.1)

INVESTIGATIONS

Preoperative Investigations (Summary Box 76.5)

• Full blood count (leukocytosis with neutrophilia - WCC usually 11,000-17,000)
• Urinalysis (exclude UTI; note: a few RBCs/WBCs may be present with retrocaecal appendicitis)

• Pregnancy test (all females of reproductive age)
• Urea and electrolytes
• C-reactive protein (CRP) - raised; a normal CRP AND normal WCC makes appendicitis unlikely
• Supine abdominal radiograph - limited value but may show faecolith, loss of psoas shadow, sentinel loop
• Ultrasound abdomen/pelvis - useful, especially in children and women; non-compressible appendix >6 mm diameter; sensitivity ~75-85%
• Contrast-enhanced CT abdomen/pelvis - gold standard for diagnosis; use low-dose protocol in young adults; sensitivity ~94-98%; also excludes other pathology

Alvarado (MANTRELS) Score - Table 76.2

PREOPERATIVE MANAGEMENT

• IV access, IV fluids (correct dehydration)
• IV antibiotics (prophylactic or therapeutic depending on severity) - typically metronidazole + a cephalosporin/co-amoxiclav
• DVT prophylaxis assessment
• Bladder must be empty before laparoscopic approach (ensure patient has voided)
• Palpate RIF for mass before draping - if mass is palpable, consider conservative approach
• Consent: laparoscopic or open; possibility of conversion; stoma (very rare)
• Mark the abdomen to plan incision

SURGICAL TECHNIQUE AND INCISIONS

Open / Conventional Appendicectomy

• Made at right angles to a line joining the ASIS to the umbilicus
• Centred at McBurney's point (junction of lateral 1/3 and medial 2/3 of this line)
• Muscles split in direction of their fibres (external oblique, internal oblique, transversus abdominis)
• Can be extended to Rutherford Morison incision by cutting the internal oblique and transversus in the line of the incision (not in the direction of their fibres) - useful for retrocaecal appendix or when wider access is needed

• Now more popular: better cosmesis, better healing, easier extension
• Made approximately 2 cm below the umbilicus, centred on the midclavicular-midinguinal line
• Can be extended medially with retraction or division of rectus abdominis

• When diagnosis is in doubt, especially if intestinal obstruction is suspected
• Preferred over right lower paramedian (which is difficult to extend, close, and provides poor pelvic access)

• Useful when appendix is difficult to locate (e.g. retrocaecal)

Operative Steps (Open)

1. Enter peritoneum; identify caecum (follow the anterior taenia coli to the base of the appendix)
2. Divide and ligate the mesoappendix including appendicular artery
3. Crush the base of the appendix with a haemostat; religate; transect
4. Stump burial with a purse-string or Z-stitch into caecal wall (invagination of the stump)
5. Irrigate if peritoneal contamination; close in layers

Laparoscopic Appendicectomy

• Bladder must be empty
• Three-port technique standard; umbilical camera port
• Mesoappendix divided using diathermy/stapler/clips; appendix base stapled or ligated with endoloops
• Superior for diagnosis in women of reproductive age (can inspect ovaries/tubes)
• Lower wound infection rate; earlier return to normal activities
• Slightly higher risk of intra-abdominal abscess post-op compared to open

Problems Encountered at Operation

• Normal appendix found: exclude terminal ileitis (Crohn's), Meckel's diverticulitis, gynaecological causes; remove appendix anyway if gridiron/Lanz incision used to avoid future diagnostic confusion (~1/4 of macroscopically normal appendices show microscopic inflammation)
• Cannot find appendix: mobilise caecum, trace taeniae coli to their confluence - the base of the appendix is always at this point
• Appendix mass at operation: may be safer to abandon (especially laparoscopically) - drain any abscess, give IV antibiotics, monitor
• Crohn's disease found: if caecal wall is healthy at base, appendicectomy is safe; if appendix itself involved, conservative management with corticosteroids/antibiotics
• Frankly necrotic appendix / extensive caecal necrosis: may require caecectomy or partial right hemicolectomy

POSTOPERATIVE COMPLICATIONS

Early

Late

NEOPLASMS OF THE APPENDIX (Brief)

• Incidence up to 0.97 per 100,000
• NETs (neuroendocrine tumours, formerly carcinoids): ~30% of appendix neoplasms; arise from Kulchitsky (argentaffin) cells; most are benign if <2 cm; found incidentally at appendicectomy
  • <2 cm: simple appendicectomy is curative

  • 2 cm: right hemicolectomy

• Epithelial tumours (mucinous or non-mucinous): range from low-grade appendiceal mucinous neoplasm (LAMN) to invasive adenocarcinoma with signet-ring features; may cause pseudomyxoma peritonei (jelly-belly)
• Mesenchymal: lymphoma, GIST, Kaposi's sarcoma, granular cell tumour

SUMMARY TABLE

• Bailey and Love's Short Practice of Surgery, 28th Ed., Chapter 76: The Vermiform Appendix