Anatomy of the Oesophagus, Achalasia Cardia: Investigations, Management Principles, and Comparative Treatment Options

PART I: ANATOMY OF THE OESOPHAGUS

Overview

Figure: Longitudinal and circular muscle arrangement of the oesophagus and lower oesophageal sphincter

Segments

Three Anatomical Constrictions

1. Upper (cricopharyngeal/pharyngo-oesophageal junction) - at 15 cm from incisors - site of Killian's triangle, most common site for foreign body impaction
2. Middle (aorto-bronchial) - at ~25 cm from incisors - where aortic arch and left main bronchus cross
3. Lower (diaphragmatic) - at ~38 cm from incisors - at oesophageal hiatus

Figure: Oesophageal subsite descriptions and constrictions with distances from incisors

Wall Structure (Layers)

• Mucosa: Stratified squamous epithelium (changes to columnar at Z-line/squamocolumnar junction)
• Submucosa: Contains mucous glands
• Muscularis externa: Two layers - inner circular + outer longitudinal
  • Upper 1/3: striated (voluntary) muscle
  • Middle 1/3: mixed striated and smooth muscle
  • Lower 1/3: smooth muscle
• No serosa - this has important surgical implications (spread of malignancy, anastomotic leak risk)

Blood Supply

• Cervical: Inferior thyroid artery
• Thoracic: Oesophageal branches of descending thoracic aorta, bronchial arteries
• Abdominal: Left gastric artery, left inferior phrenic artery

Venous Drainage

• Cervical → inferior thyroid veins → brachiocephalic vein
• Thoracic → azygos and hemiazygos veins → superior vena cava
• Abdominal → left gastric (coronary) vein → portal vein (portosystemic anastomosis - clinically important in portal hypertension causing oesophageal varices)

Lymphatic Drainage

• Cervical → deep cervical nodes
• Thoracic → posterior mediastinal nodes, tracheobronchial nodes
• Abdominal → coeliac nodes
• Note: submucosal lymphatics run longitudinally, allowing spread of malignancy over long distances before transmural invasion

Nerve Supply

• Parasympathetic: Vagus nerve (CN X) - forms oesophageal plexus around the lower thoracic oesophagus
• Sympathetic: From T5-T10 sympathetic ganglia via splanchnic nerves
• Intrinsic plexus: Auerbach's (myenteric) plexus between muscle layers; Meissner's (submucosal) plexus - loss of Auerbach's plexus neurons (particularly inhibitory nitrergic neurons) is the pathological basis of achalasia

Lower Oesophageal Sphincter (LES)

• Intrinsic circular smooth muscle tone
• Extrinsic crural diaphragm compression
• Angle of His (acute angle between oesophagus and stomach)
• Intra-abdominal segment of oesophagus

PART II: ACHALASIA CARDIA - INVESTIGATIONS AND PRINCIPLES OF MANAGEMENT

Definition and Pathophysiology

1. Failure of LES relaxation (impaired LES relaxation on swallowing)
2. Absent peristalsis in the oesophageal body

Investigations

1. Barium Swallow (Upper GI Contrast Study)

• Classic finding: "Bird's beak" or "rat-tail" appearance at the gastro-oesophageal junction
• Dilated, baggy oesophagus with tapered narrowing distally
• Absent primary peristalsis
• Food debris visible in dilated oesophagus
• In advanced disease: massively dilated, sigmoid-shaped oesophagus ("megaoesophagus")

Barium swallow showing classic bird's beak appearance and massive oesophageal dilatation in achalasia

2. High-Resolution Manometry (HRM) - Gold Standard

• Most sensitive diagnostic test - identifies disease before dilatation occurs
• Mandatory findings: (1) impaired LES relaxation (elevated integrated relaxation pressure, IRP > 15 mmHg) + (2) absent peristalsis
• Subclassifies achalasia into 3 types per the Chicago Classification:

HRM subtypes of achalasia - clinically important as they guide treatment selection

3. Upper GI Endoscopy (OGD)

• Mandatory to exclude pseudoachalasia (secondary achalasia due to carcinoma at cardia - especially if age >60, rapid weight loss, short symptom duration)
• Findings: dilated oesophagus, food/fluid retention, "popping" sensation as endoscope passes through LES (pathognomonic), inflamed mucosa from stasis
• Biopsies from GEJ to rule out malignancy

4. CT Chest/Abdomen

• When pseudoachalasia is suspected (malignancy, external compression, e.g., lymphoma, lung cancer)
• Assess degree of dilatation and any mediastinal involvement

5. Timed Barium Oesophagram

• Column height of barium measured at 1, 2, and 5 minutes
• Used to monitor treatment response objectively

6. FLIP (Functional Lumen Imaging Probe)

• Newer modality assessing distensibility of the EGJ
• Useful when HRM results are inconclusive

Principles of Management

1. Reduce LES pressure (pharmacological, endoscopic, or surgical)
2. Prevent complications (aspiration, oesophageal dilatation, carcinoma)
3. Preserve oesophageal mucosa and avoid iatrogenic reflux
4. Select treatment modality based on patient fitness, achalasia subtype, centre expertise

• Sublingual nifedipine 30-40 mg before meals (calcium channel blocker - reduces LES pressure)
• Isosorbide dinitrate sublingually (nitrate - smooth muscle relaxant)
• Sildenafil (PDE-5 inhibitor)
• Significant side effects (headache, hypotension, flushing), poor long-term efficacy; used as bridge to definitive therapy or in frail patients

PART III: COMPARATIVE ANALYSIS OF TREATMENT OPTIONS (15 Marks)

Overview Summary Table

1. Pneumatic Dilation (PD)

• Patient fasted (liquid diet 1-2 days pre-procedure)
• Savary guidewire placed endoscopically into stomach
• Rigiflex balloon (3.0 cm first; 3.5 cm, then 4.0 cm in graded approach) inflated to 7-15 psi for 60 seconds under fluoroscopy
• Patient monitored for 2-6 hours post-procedure; gastrografin swallow if perforation suspected

• First-line definitive therapy (especially type II achalasia - 100% efficacy in European trial)
• Good fit for most achalasia patients as initial treatment
• Preferred when surgical risk is high
• Type I and II achalasia

• Initial success rates: 60-90%
• European Achalasia Trial (multicenter RCT): ~90% efficacy at 5 years when graded dilation used - equivalent to laparoscopic Heller myotomy
• Type II: 100% efficacy with PD vs 93% with LHM
• Type III: only ~40% efficacy - NOT preferred
• Repeat dilation improves cumulative success rates

• Perforation: ~1-5% (most serious; identified by pain, subcutaneous emphysema, gastrografin leak - managed surgically or endoscopically)
• GERD: ~10-20% (less than after POEM, more than after LHM with fundoplication)
• Mucosal haematoma, post-procedure chest pain
• Recurrence requiring repeat dilation (~25-30% need repeat within 5 years)

2. Laparoscopic Heller's Myotomy (LHM)

• General anaesthesia, 5 laparoscopic ports
• Circumferential dissection of distal oesophagus
• Myotomy extended 6-8 cm proximally on oesophagus and 2.5-3 cm onto stomach
• Partial fundoplication added: Dor (anterior, 180°) or Toupet (posterior, 270°) fundoplication to prevent GERD without obstructing the myotomised segment. Complete Nissen fundoplication is NOT recommended as it recreates functional obstruction.

• Gold standard surgical treatment for achalasia
• Preferred for type III (spastic) achalasia (86% success vs 40% with PD)
• Failed or repeated pneumatic dilation
• Young patients (more durable than PD)
• Patients with tortuous/sigmoid oesophagus
• Preference for single definitive procedure

• Systematic review of >3000 LHMs: ~90% clinical success
• Boeckxstaens et al review (2264 patients, 42-month follow-up): 84% efficacy
• European Achalasia Trial: 84% success at 5 years
• With partial fundoplication: GERD rate 8.8% vs 31.5% with myotomy alone
• Equivalent to PD when graded dilation approach used

• Oesophageal perforation/mucosal tear: ~1% (managed intraoperatively by direct suture repair)
• GERD if no fundoplication added (~30-47% without fundoplication)
• Dysphagia (incomplete myotomy, too tight fundoplication)
• Pneumothorax, mediastinal emphysema
• Splenic injury, bleeding (~1-2%)
• Conversion to open: rare

3. Peroral Endoscopic Myotomy (POEM)

• General anaesthesia, patient supine
• Mucosal incision made ~12 cm proximal to GEJ on anterior wall
• Submucosal tunnel created distally to extend 2-3 cm onto gastric cardia
• Selective inner circular muscle layer divided using electrocautery knife (~10-12 cm myotomy)
• Mucosal entry site closed with endoscopic clips
• No external incision; hospital stay 1-2 days

• Type III (spastic) achalasia - POEM allows longer myotomy proximally compared to LHM, ideal for spastic type
• Failed pneumatic dilation or LHM
• High surgical risk patients (avoids laparotomy)
• Younger patients desiring minimal invasiveness
• Prior surgery making laparoscopic approach difficult
• Re-do procedures

• Short-term success: ~90%
• RCT (JAMA 2019): POEM vs pneumatic dilation - POEM was superior in treatment-naive patients (83% vs 72% success at 2 years)
• RCT (NEJM 2019): POEM vs LHM - POEM was non-inferior to LHM + Dor fundoplication for dysphagia control at 2 years; however, GERD rates significantly higher with POEM
• Particularly effective for type III: myotomy can be extended more proximally than LHM
• Long-term data (>5 years) still accumulating

• GERD: Major drawback - 40-50% develop pathological reflux (vs ~10% with LHM + fundoplication). No fundoplication is added during POEM. Requires long-term PPI therapy.
• Capnoperitoneum/capnomediastinum (CO2 insufflation during tunnelling): usually self-limiting
• Mucosal perforation: ~1%
• Bleeding: rare
• Mediastinitis: rare
• Barrett's oesophagus risk with chronic reflux (long-term surveillance needed)

4. Botulinum Toxin Injection (BTX)

1. Elderly or frail patients who are high surgical risk and cannot tolerate PD, LHM, or POEM
2. Diagnostic uncertainty - if positive response confirms functional LES obstruction and identifies candidates for definitive therapy
3. Bridge therapy before definitive treatment
4. Patients with recurrent symptoms after LHM or POEM (residual short sphincter segment)
5. Chest pain-predominant achalasia with spasm features
6. Patients refusing invasive procedures

• Initial response: ~90% at 1 week (double-blind RCT data)
• Sustained response: ~66% at 6 months; only ~35% at 1 year
• Repeat injections can work but effectiveness diminishes with time
• Dose >100 units does not improve efficacy

• Chest pain/discomfort (transient, several days)
• Occasional skin rash at injection site
• Generally very safe - no perforation risk
• Important: Repeated injections cause local fibrosis and inflammatory reaction, which can increase technical difficulty and complication rates if subsequent LHM or POEM is needed
• Rare: mediastinitis, pleural effusion

Head-to-Head Comparative Points

• Type I & II: PD is preferred first-line (low cost, 90-100% efficacy, equivalent to LHM at 5 years with graded approach); LHM equally valid
• Type III: POEM or LHM preferred (PD only 40% success; POEM allows longer proximal myotomy)

When to Escalate / End-Stage Disease

• Massively dilated sigmoid oesophagus (megaoesophagus)
• Severe dysphagia unresponsive to all LES-directed therapy
• Peptic stricture or carcinoma
• Procedure: subtotal oesophagectomy with gastric pull-up; mortality ~2.7%; significant morbidity. Last resort. - Clinical Gastrointestinal Endoscopy 3e

Key Takeaway Points (Exam Summary)

1. Anatomy: Oesophagus is 25 cm, no serosa, three constrictions (15/25/38 cm from incisors), dual nerve supply via vagus and sympathetic chain; submucosal venous plexus forms portosystemic anastomosis.
2. Achalasia pathology: Loss of inhibitory (nitrergic) ganglion cells in Auerbach's plexus → absent LES relaxation + aperistalsis.
3. Investigations: HRM (gold standard), barium swallow (bird's beak), OGD (exclude pseudoachalasia), CT (if malignancy suspected).
4. Achalasia subtypes (HRM): Type I (classic), II (compression, best prognosis), III (spastic, hardest to treat).
5. Treatment choice:
   • Type I/II + fit patient: PD (first-line, graded) or LHM
   • Type III: POEM or LHM (long myotomy)
   • Frail/elderly: BTX injection
   • Failed LHM or PD: POEM or re-do LHM
   • End-stage megaoesophagus: oesophagectomy
6. POEM vs LHM: Non-inferior efficacy, but POEM has higher GERD (requires PPI); LHM adds fundoplication for reflux control.
7. BTX: Safe, short-acting, non-curative; fibrosis from repeated use complicates future surgery.