Achalasia (primary achalasia) refers to a failure of organised oesophageal peristalsis with impaired relaxation of the lower oesophageal sphincter (LOS), resulting in often marked dilatation of the oesophagus and food stasis. Obstruction of the distal oesophagus (often due to tumour) has been termed "secondary achalasia" or "pseudoachalasia".
Primary achalasia 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.
Typically patients present with dysphagia (which is for both solids and liquids, in comparison to dysphagia for solids only in cases of esophageal carcinoma 7), 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
- candida oesophagitis
- acute airway obstruction: this is a rare complication requiring immediate oesophageal decompression with nasogastric tube
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 abnormality may also occur in the vagus nerve or in the dorsal motor nucleus of the vagus nerve.
The LOS eventually fails to relax, either partially or completely, with elevated pressures demonstrated manometrically 4. Early in the course of achalasia, this LOS tone may be normal or changes may be subtle.
Achalasia characteristically involves a short segment (less than 3.5 cm) of the distal oesophagus.
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.
Fluoroscopy: 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:
- bird beak sign
- oesophageal dilatation
- incomplete LOS relaxation that is not coordinated with oesophageal contraction
- pooling or stasis of barium in the oesophagus when the oesophagus has become atonic or non contractile (late feature in the disease)
- uncoordinated, non-propulsive, tertiary contractions (see case 1)
- failure of normal peristalsis to clear the oesophagus of barium when the patient is in the recumbent position, with no primary waves identified
- when barium column is high enough (patient standing) the hydrostatic pressure can overcome the LOS pressure allowing passage of oesophageal content
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% of patients develop gastro-oesophageal reflux, and thus it is often combined with a Nissen fundoplication
History and etymology
The word achalasia stems from the Greek term "does not relax".
A number of entities may mimic achalasia, forming the so called 'achalasia pattern'.
- achalasia: distal segment of narrowing is <3.5 cm
- central and peripheral neuropathy
- scleroderma: GOJ will be open; less severe dilatation
- oesophageal malignancy or gastric carcinoma: commonly referred as pseudoachalasia
- oesophageal stricture
- Chagas disease
- anti-Hu antibodies from lung cancer
Other oesophageal disorders should also be considered:
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