Achalasia

Achalasia essentialy refers to a failure of organized peristalsis with impaired relaxation at the level of lower oesophageal sphincter (LOS) resulting in often marked dilatation of the oesophagus and food stasis.

Epidemiology

It is most frequently seen in middle and late adulthood (30 - 70 years of age) with no gender predilection ⁶. In most cases achalasia is idiopathic, however an identical appearance is seen in patients with Chagas disease. Authors differ as to whether they reserve the term achalasia for idiopathic cases, or whether they include Chagas disease.

Clinical presentation

Typically patients present with dysphagia, chest pain / discomfort and eventual regurgitation. Initially symptoms are intermittent. Patients may also present with a complication of long standing achalasia:

• oesophageal carcinoma : is the most dreaded complication and is seen in approximately 5%, and most often in the mid oesophagus. It is thought to relate to the chronic irritation of the mucosa by stasis of food and secretions.
• aspiration pneumonia and eventually abscess formation
• candida oesophagitis
• acute airway obstruction: this is a rare complication requiring immediate oesophageal decompression with nasogastric tube

Pathology

Peristalsis in the distal smooth muscle segment of the oesophagus may be lost due to an abnormality of Auerbach plexus (responsible for smooth muscle relaxation), resulting in weak contractions that are uncoordinated and as a result non propulsive. The LOS fails to relax, either partially or completely, with elevated pressures demonstrated manometrically ⁴.

Radiographic features

Chest radiograph

Chest x-ray findings include :

• right convex opacity behind right cardiac border; occasionally left convex opacity if thoracic aorta tortuous
• air-fluid level due to stasis in thoracic oesophagus filled with retained secretions and food
• small / absent gastric air bubble
• anterior displacement and bowing of trachea on the lateral view

The chronic presence of fluid debris in the oesophagus makes patients very prone to aspiration and thus patchy bilateral alveolar opacities representing acute or chronic aspiration pneumonia may be seen.

Barium swallow

A barium swallow is able to not only confirm that the oesophagus is dilated but is also able to assess for mucosal abnormalities. 

Findings include:

• failure of normal peristalsis to clear the oesophagus of barium when the patient is in the recumbent position, with no primary waves identified
• uncoordinated, non-propulsive, tertiary contractions (see case 1)
• oesophageal body dilatation, which is typically maximal in the distal esophagus
• pooling or stasis of barium in the oesophagus when the oesophagus has become atonic or non contractile (late feature in the disease)
• when barium column is high enough (patient standing) the hydrostatic pressure can overcome the LOS pressure allowing passage of oesophageal content
• incomplete LOS relaxation that is not coordinated with oesophageal contraction
• bird beak sign

CT

Patients with uncomplicated achalasia demonstrate a dilated thin walled oesophagus filled with fluid / food debris. 

Overall CT has little role in directly assessing patients with achalasia, but is useful in assessing common complications. Careful assessment of the wall of the oesophagus should be undertaken to identify any focal regions of thickening which may indicate malignancy. The lungs should be inspected for evidence of aspiration. 

Treatment and prognosis

Treatment is aimed at allowing adequate drainage of the oesophagus into the stomach. Options include ^4-5 :

• calcium channel blockers
  • ineffective in long term
  • may be used while preparing for definitive treatment
• pneumatic dilatation
  • effective in 85% of patients
  • 3-5% risk of bleeding / perforation
• botulinum toxin injection
  • lasts only ~ 12 months per treatment
  • may scar the submucosa leading to increased risk of perforation during subsequent myotomy
• surgical myotomy (Heller myotomy)
  • 10-30% op patients develop gastrooesophageal reflux, and thus it is often combined with a Nissen fundoplication

Etymology

The word achalasia stems from the Greek term "does not relax".

Differential diagnosis

A number of entities may mimic achalasia, forming the so called 'achalasia pattern'. 

• achalasia : distal segment of narrowing is less than 3.5 cm
• central and peripheral neuropathy
• scleroderma
• oesophageal malignancy or gastric carcinoma : commonly referred as pseudoachalasia
• oesophageal stricture
• Chagas disease