What is the recommended system for staging achalasia?

Achalasia Staging: The Chicago Classification System

The recommended system for staging achalasia is the Chicago Classification (now version 4.0), which uses high-resolution manometry (HRM) to categorize achalasia into three distinct subtypes (Type I, II, and III) based on esophageal body pressurization patterns and contractility, with Type II having the best treatment response and Type III the poorest. 1, 2

The Three Achalasia Subtypes

The Chicago Classification defines achalasia subtypes based on HRM patterns in patients with impaired deglutitive lower esophageal sphincter (LES) relaxation and absent peristalsis 1:

Type I (Classic Achalasia)

• Minimal or negligible pressurization within the esophageal body 1
• Represents a decompensated, dilated esophagus 1
• 100% failed peristalsis without panesophageal pressurization 2
• May have very low LES pressure and integrated relaxation pressure (IRP) late in disease 1

Type II (Compression Achalasia)

• Panesophageal pressurization with uniform simultaneous pressurization bands spanning from upper to lower sphincter 1
• Most common presenting subtype in multiple series 1
• Panesophageal pressurization in at least 20% of swallows 2
• Presumed precursor to Type I 1
• Best response to all forms of therapy (botulinum toxin, pneumatic dilation, or myotomy) 1, 3

Type III (Spastic Achalasia)

• Premature (spastic) contractions with distal latency <4.5 seconds between upper sphincter relaxation and arrival of rapidly propagated contraction 1
• Previously known as "vigorous achalasia" 1
• At least 20% of swallows premature with no appreciable peristalsis 2
• Poorest response to all treatments 1, 3
• POEM with longer myotomy is the preferred treatment option 1, 4

Diagnostic Criteria for Conclusive Achalasia

According to Chicago Classification version 4.0, conclusive achalasia requires 2:

• Abnormal median IRP in the primary position with wet swallows
• 100% failed peristalsis
• Subtype differentiation based on pressurization patterns described above

Inconclusive Achalasia Diagnoses

HRM may yield inconclusive results when 2:

• IRP is borderline or at upper limit of normal in at least one position
• Abnormal IRP in both positions but evidence of peristalsis with panesophageal pressurization or premature swallows
• Peristalsis appears in secondary position after apparent achalasia in primary position

In patients with dysphagia and inconclusive HRM, supportive testing with timed barium esophagram (TBE) or functional lumen imaging probe (FLIP) is recommended 2.

EGJ Outflow Obstruction: A Fourth Entity

The Chicago Classification also recognizes esophagogastric junction (EGJ) outflow obstruction as a distinct syndrome that can mimic achalasia 1:

• IRP greater than upper limit of normal, but "absent peristalsis" criterion not met 1
• Peristalsis may be fragmented or even normal 1
• Heterogeneous group with spectrum of etiologies including early/incomplete achalasia (12-40% of cases) 1
• 20-40% resolve spontaneously, but 12-40% ultimately treated as achalasia 1
• Always requires intense clinical evaluation (endoscopic ultrasound, CT, timed barium esophagram) to clarify etiology 1

Clinical Implications of Subtyping

Prognostic Value

• Type II achalasia shows overall success rate of 80.0% with treatment 3
• Type I shows 55.2% success rate 3
• Type III shows only 33.2% success rate 3

Treatment Selection

While subtyping provides prognostic information, there is insufficient evidence to recommend specific therapies based on subtype alone, especially between Type I and Type II 1. The exception is Type III achalasia, where POEM with longer myotomy is preferred 1, 4.

Treatment decisions should incorporate 1:

• Chicago Classification subtype
• Patient comorbidities
• Early versus late disease stage
• Primary or secondary causes
• Local expertise and therapeutic availability

Important Diagnostic Limitations

The Chicago Classification has inherent limitations 1:

• IRP sensitivity is <100%, particularly in Type I disease where LES pressure may be very low 1
• Specificity is <100% as instances with preserved peristalsis can occur 1
• Disease evolves over variable timespan, so testing may occur along continuum from normal to unequivocal achalasia 1
• Early disease may require provocative maneuvers (multiple rapid swallows, rapid drink challenge) to unmask impaired inhibitory innervation 1