Primary Diagnostic Test for Achalasia
High-resolution esophageal manometry is the gold standard and required diagnostic test for achalasia, demonstrating the two cardinal features: absent esophageal peristalsis and failure of the lower esophageal sphincter to relax. 1, 2, 3
Diagnostic Algorithm
Step 1: Clinical Suspicion
- Suspect achalasia when patients present with dysphagia to both solids and liquids simultaneously from disease onset—this pattern distinguishes achalasia from mechanical obstruction 1, 4
- Additional red flags include postprandial regurgitation of undigested food, chest pain (especially in Type II and III), and pulmonary symptoms from nocturnal aspiration 1, 4
Step 2: Initial Evaluation
- Upper endoscopy must be performed first to exclude mechanical obstruction (tumors, strictures) and other structural causes 2, 3
- Look for retained saliva and puckering of the gastroesophageal junction as diagnostic clues 2
- Barium esophagram provides complementary anatomic information, showing dilated esophagus with "bird beak" appearance and assessing for end-stage changes 5, 2
Step 3: Confirmatory Testing
- High-resolution manometry (HRM) is mandatory to establish the diagnosis 1, 6, 7
- HRM must demonstrate:
- HRM also classifies the Chicago Classification subtype (I, II, or III), which directly determines treatment selection and prognosis 1, 8, 2
Critical Diagnostic Pitfalls
Early Disease
- In early achalasia, the IRP may fall below the upper normal limit, potentially causing a false-negative manometry result 1, 4
- Functional luminal imaging probe (FLIP) or timed barium esophagram may be needed when clinical suspicion remains high despite borderline manometry 1
Late/End-Stage Disease
- In advanced Type I achalasia, both LES pressure and IRP can be paradoxically very low, mimicking absent contractility rather than achalasia 1, 4
- Timed barium esophagram becomes essential in these cases to demonstrate impaired esophageal emptying and confirm the diagnosis 1, 5
EGJ Outflow Obstruction
- This entity can mimic achalasia but may represent incomplete/early disease or a distinct pathology 1, 8
- Before committing to permanent interventions, perform endoscopic ultrasound and CT imaging of the esophagogastric junction to exclude secondary causes (malignancy, infiltrative disease) 9, 1
- Many cases resolve spontaneously; observation may be appropriate 9
Complementary Diagnostic Tools
- Timed barium esophagram (TBE) quantitatively assesses esophageal emptying and is useful for diagnosis when manometry is equivocal and for monitoring treatment response 5, 3
- Functional luminal imaging probe (FLIP) measures distensibility and supports achalasia diagnosis when manometry shows borderline findings 9
Why Manometry is Essential
High-resolution manometry with esophageal pressure topography is more sensitive than conventional water-perfused manometry and provides detailed pressure patterns that identify the three clinically relevant subtypes 7:
- Type I (minimal pressurization): end-stage disease with variable treatment success 1, 8
- Type II (pan-esophageal pressurization): best prognosis with 90-100% treatment success 1, 8
- Type III (premature spastic contractions): poorest response to standard therapy (29-33% success), requires extended myotomy via POEM 9, 8
Without manometric confirmation and subtype classification, optimal treatment selection is impossible. 1, 8, 2