Description
Achalasia is a primary oesophageal motility disorder characterised by the absence of coordinated peristalsis in the smooth muscle of the oesophagus and failure of the lower oesophageal sphincter (LES) to relax in response to swallowing. It results in progressive dysphagia, regurgitation of undigested food, and chest pain.
Pathogenesis
Achalasia is thought to be due to the degeneration of inhibitory ganglion cells in the myenteric plexus of the oesophagus. The precise cause of this degeneration remains unclear but may involve autoimmune, genetic, and infectious factors. Loss of these inhibitory neurons leads to an imbalance between excitatory (acetylcholine) and inhibitory (nitric oxide and vasoactive intestinal peptide) neurotransmitters, causing unopposed excitation and subsequent failure of the LES to relax and loss of peristalsis in the oesophageal body.
Subtypes
Three subtypes of achalasia have been identified based on high-resolution manometry (Chicago classification):
- Type I (classic achalasia): absence of peristalsis and no pressurisation.
- Type II (achalasia with compression): absence of peristalsis but with pan-oesophageal pressurisation.
- Type III (spastic achalasia): absence of peristalsis and spastic contractions in the distal oesophagus.
Epidemiology, Risk Factors & Associations
- Affects men and women equally and can occur at any age (typical age of presentation is 25-60 years).
- Not associated with any specific risk factors or lifestyle choices.
- Rare familial cases have been reported.
Clinical Features
- Dysphagia (to both solids and liquids)
- Regurgitation of undigested food
- Chest pain
- Weight loss due to reduced food intake
- Nighttime coughing or aspiration (from regurgitation when lying down)
Complications
- Aspiration pneumonia
- Oesophageal perforation
- Increased risk of oesophageal squamous cell carcinoma
Pathological Features
Histopathology
- Macroscopic: Dilatation and elongation of the oesophagus, with possible presence of retained food material.
- Microscopic: Chronic inflammation, degeneration, or absence of ganglion cells in the myenteric plexus, muscle fibre hypertrophy.
Radiological Features
General Features
- Characteristically demonstrates a dilated oesophagus with fluid and food debris, tapering towards the gastro-oesophageal junction (“bird-beak” appearance).
- Minimal or no peristalsis and poor relaxation of the LES on dynamic study.
Radiological Features
General Features
- Characteristically demonstrates a dilated oesophagus with fluid and food debris, tapering towards the gastro-oesophageal junction (“bird-beak” appearance).
- Minimal or no peristalsis and poor relaxation of the LES on dynamic study.
FL
Barium Swallow
- Initial stage shows dilation of the oesophagus with fluid and food debris, smooth tapering towards the gastro-oesophageal junction – the characteristic bird-beak appearance.
- Delayed images demonstrate poor emptying of the barium due to non-relaxation of the LES.
- A corkscrew or rosary bead appearance may be seen in the later stages due to oesophageal muscle hypertrophy and spasm, more common in Type III achalasia.
XR
- Chest X-ray may show a dilated oesophagus filled with an air-fluid level in the posterior mediastinum, but is often normal.
CT
- Non-contrast: Dilated oesophagus with fluid level.
- Contrast-enhanced: Bird-beak appearance of the oesophagus at the gastro-oesophageal junction.
MRI
- T1WI: Dilated oesophagus with hypointense fluid level.
- T2WI: Hyperintense fluid within the dilated oesophagus.
- T1 C+: No significant enhancement.
- DWI/ADC: No diffusion restriction.
Grading and Staging
Achalasia does not have a specific grading or staging system.
Diagnosis
Diagnosis typically involves manometry showing absent peristalsis and incomplete relaxation of the LES, barium swallow demonstrating dilated oesophagus with ‘bird-beak’ sign, and endoscopy to rule out other causes of obstruction.
Differential Diagnosis
- Scleroderma – Similarly affects lower two-thirds of oesophagus. Assess for changes of NSIP (non-specific interstitial pnuemonia) in lungs.
- Mechanical causes of obstruction (oesophageal cancer, gastro-oesophageal reflux disease) – LES eventually relaxes with achalasia, allowing slow passage of food.
Management
The aim of treatment is to relieve symptoms by reducing the pressure within the LES. Options include pneumatic dilatation, surgical myotomy (Heller myotomy), and endoscopic myotomy (peroral endoscopic myotomy or POEM). Botulinum toxin injections may be used in patients not suitable for other treatments.