How do I interpret a high‑resolution esophageal manometry study and diagnose esophageal motility disorders?

How to Interpret High-Resolution Esophageal Manometry and Diagnose Esophageal Motility Disorders

Interpret HRM using spatiotemporal pressure topography plots to systematically assess three key components: oesophago-gastric junction (OGJ) relaxation via integrated relaxation pressure (IRP), esophageal body peristalsis via distal contractile integral (DCI) and distal latency (DL), and then apply the Chicago Classification to categorize motility disorders. 1

Essential Pre-Test Requirements

Before performing HRM, patients with dysphagia must undergo endoscopy with oesophageal biopsies to exclude mucosal disorders (particularly eosinophilic oesophagitis) and structural abnormalities. 1, 2 Barium swallow should be considered when endoscopy is not feasible or when structural disorders require additional characterization. 1

Standard HRM Protocol and Technique

Equipment Setup and Patient Positioning

• Perform catheter calibration and zeroing according to manufacturer specifications before each study. 1
• Staff performing HRM must be fully trained and accredited by AGIP or supervised by an accredited practitioner. 1
• Position the catheter transnasally to record from hypopharynx to stomach, then allow a 5-minute resting period to assess basal sphincter pressure. 3

Standard Swallow Protocol

• Obtain ten 5 mL room temperature water swallows with 20-30 seconds between each swallow. 1
• Studies can be performed in either supine or upright position, but you must use position-specific normal values. 1, 4 The supine position is conventional, but upright positioning is more physiological for solid-state catheters and may reduce false-positive diagnoses of outlet obstruction. 1, 4

Core HRM Parameters to Measure

1. Integrated Relaxation Pressure (IRP)

IRP measures OGJ relaxation and is calculated as the lowest mean OGJ pressure (referenced to gastric pressure) for 4 continuous or non-continuous seconds during a 10-second window after swallow onset, measured from UOS opening. 1 This is your primary metric for detecting achalasia and OGJ outflow obstruction. 1

Critical caveat: Normal IRP values are manufacturer and catheter-specific. 1 For example, Unisensor catheters yield markedly higher IRP values than Manoscan catheters, so you must apply the correct reference range for your equipment. 1

2. Distal Contractile Integral (DCI)

DCI quantifies esophageal contraction vigor by multiplying the amplitude of contraction (mm Hg) by duration (seconds) by length of the distal segment (cm) from the transition zone to the proximal LOS margin. 1 DCI >450 mm Hg×s×cm with no peristaltic breaks >5 cm within a 20 mm isobaric contour confirms intact peristalsis. 1

3. Distal Latency (DL)

DL is measured from the beginning of UOS swallow-induced relaxation to the contractile deceleration point (CDP). 1 The CDP is the inflection point along the 30 mm Hg isobaric contour where propagation velocity slows, and it must be localized within 3 cm of the proximal LOS margin. 1

Mandatory Adjunctive Testing to Unmask Hidden Pathology

Standard water swallows alone miss clinically significant motility disorders in up to 50% of patients with dysphagia. 1, 2 You must perform adjunctive testing because it reproduces normal eating behavior, is more likely to provoke symptoms, and doubles the diagnostic yield of major motor disorders. 1, 2

Rapid Drink Challenge (RDC)

Administer 200 mL of water drunk freely through a straw in the upright position. 1 RDC-IRP >12 mm Hg accurately identifies obstruction associated with achalasia, while RDC-IRP >8 mm Hg detects all-cause OGJ obstruction. 1

Multiple Rapid Swallows (MRS)

Give repetitive 2 mL volumes at 1-2 second intervals. 1 MRS is particularly sensitive for identifying peristaltic reserve in patients with fragmented or ineffective peristalsis on single swallows. 1

Solid Swallows or Test Meal

Use either a patient-provided culprit food or standardized cooked rice meal in the upright position. 1 For test meals, define achalasia/OGJ obstruction when ≥2 swallows have IRP >25 mm Hg, spasm when ≥2 swallows have DL <4.5 seconds, and hypercontractility when ≥2 contractions have DCI >8000 mm Hg×s×cm. 1

Compared to water swallows alone, test meals alter manometric classification in 67% of patients, change clinical diagnosis in 39%, and double the detection rate of major motor disorders. 1 Test meals are especially valuable after antireflux surgery, detecting dysmotility in 70% versus 30% with water swallows alone. 1

Diagnostic Algorithm Using Chicago Classification

Step 1: Assess OGJ Relaxation (IRP)

• Elevated IRP indicates achalasia or OGJ outflow obstruction. 1
• If IRP is borderline or diagnosis unclear, proceed to EndoFLIP for additional functional assessment. 5

Step 2: Evaluate Peristaltic Pattern

• Absent contractility (DCI <100 mm Hg×s×cm in all swallows) suggests type I achalasia. 2
• Premature contractions (DL <4.5 seconds) indicate spastic disorders. 1
• Hypercontractile esophagus shows DCI >8000 mm Hg×s×cm in ≥20% of swallows. 1

Step 3: Characterize Minor Disorders

Minor disorders (ineffective motility with >50% swallows DCI <450 mm Hg, or fragmented peristalsis with >50% swallows having breaks >5 cm) have uncertain clinical significance. 1 These findings are often false positives—70% of patients with minor disorders are asymptomatic at 5-year follow-up and rarely progress. 1

When minor disorders are detected on supine water swallows, resolve the diagnostic uncertainty by performing upright position testing and adjunctive maneuvers (RDC, MRS, or test meal). 1, 4 Patients demonstrating peristaltic reserve with solids or MRS do not have a major motor disorder. 1

Position-Specific Considerations

Diagnostic agreement between supine and upright positions is only 67.6% overall, but improves to 90% when ineffective motility is grouped with normal motility. 4 Key differences include:

• IRP is approximately 4 mm Hg higher in supine position. 4
• Supine position generates more false-positive diagnoses of outlet obstruction (16/20 versus 1/4 in upright). 4
• Upright position with solid test meal shows 85.7% concordance for OGJ obstruction/achalasia diagnosis versus only 41.4% with supine water swallows. 4

Role of High-Resolution Impedance Manometry (HRIM)

Adding impedance to HRM visualizes bolus movement and can identify impaired bolus clearance in patients with dysphagia but normal pressure measurements. 1 This subset comprises up to 50% of referrals for swallowing problems. 1

However, the International Manometry Working Group does not include impedance in the classification of motor disorders, stating it only "complements" functional analysis. 1 Its impact on therapeutic decision-making remains unestablished. 1

When to Use EndoFLIP as Adjunct

Order EndoFLIP when HRM shows borderline IRP or equivocal findings, in patients with persistent dysphagia despite histologic remission of eosinophilic oesophagitis with normal endoscopy, or for intra-operative guidance during POEM. 5

In achalasia, EndoFLIP typically shows DI <2.0 mm²/mm Hg (often around 1.2) and maximum diameter <12 mm at 60-70 mL fill volumes, compared to normal DI >9 mm²/mm Hg. 5 EndoFLIP can also identify sustained occluding contractions corresponding to type III achalasia and spastic disorders. 5

Critical limitation: EndoFLIP should never be used in isolation to justify permanent therapeutic interventions and must be interpreted alongside clinical and other diagnostic data. 5

Key Clinical Applications

• HRM is mandatory before antireflux surgery to exclude achalasia and major motor disorders. 2
• HRM enables achalasia subtyping (types I, II, III), which has prognostic value and guides therapeutic decisions. 2
• HRM is the preferred method to localize the LOS before pH catheter placement. 2
• In patients with persistent dysphagia after antireflux surgery, HRM provides diagnostic information unavailable from standard manometry. 2

Common Pitfalls to Avoid

• Failing to check electrolyte abnormalities (particularly magnesium and potassium) before attributing dysmotility to a primary esophageal disorder. 2
• Using incorrect normal values for your specific catheter manufacturer and model. 1
• Diagnosing a major motor disorder based solely on supine water swallows without performing adjunctive testing. 1, 2
• Interpreting minor disorders as clinically significant without confirming they persist with provocative maneuvers. 1
• Performing manometry before endoscopy with biopsies in patients with dysphagia. 1, 2