IRP Interpreter • Chicago v4.0 Metric
Enter the IRP value and select the catheter type to visualize the GOJ relaxation profile.
Guidelines & Evidence
Verified
Last Review: 2026-07-17
When to Use
When to Use
Defining Esophagogastric Junction (EGJ) obstruction in High-Resolution Manometry (HRM)
The primary diagnostic threshold for all types of Achalasia (v4.0 Chicago Classification)
Distinguishing between functional obstruction (high IRP) and normal motility (normal IRP)
The 'Integrated' Logic
The IRP represents the lowest average pressure of EGJ relaxation over 4 seconds (continuous or non-continuous) during the 10-second window following a swallow.
How it Works
Hardware-Specific Thresholds
| Medtronic (Given) | Abnormal if > 15 mmHg |
| Diversatek (Sandhill) | Abnormal if > 22 mmHg |
| Unisensor | Abnormal if > 19 mmHg |
Interpretation Protocol (v4.0)
01
Step 1: Check IRP in the supine position (10 swallows).
02
Step 2: If equivocal (e.g., 10–15 mmHg), check upright IRP.
03
Step 3: If still equivocal, perform a Rapid Drink Challenge (RDC) or Multiple Rapid Swallows (MRS) to "stress" the EGJ.
Clinical Pearls
Achalasia with a "Normal" IRP
Up to 5% of patients with clinically proven Achalasia may have a "Normal" IRP (e.g., 12 mmHg) on a single study. This is why the Chicago v4.0 criteria allow for a diagnosis of Achalasia even with a borderline IRP if there is 100% failed peristalsis AND evidence of obstruction on Timed Barium Swallow.
The Artifact Trap
Diaphragmatic "crural" interference can falsely elevate the IRP. Clinicians should ensure the IRP box on the manometry software is correctly positioned over the LES and away from the crural diaphragm to avoid over-diagnosis of EGJOO.
Clinical Pearls
A high IRP in a patient with persistent peristalsis is the definition of EGJ Outflow Obstruction (EGJOO)
The IRP should always decrease (improve) following successful POEM or Heller Myotomy
Hiatal hernia can cause "pseudo-high" IRP due to overlap of the hernia sac and the LES
Next Steps
Clinical Triage
01
IRP > 15 + 100% Failed Peristalsis: Diagnose Achalasia (Type I/II).
02
IRP > 15 + Preserved Peristalsis: Perform Timed Barium Swallow to confirm EGJOO.
03
IRP < 15 + Dysphagia: Look for abnormal contractile vigor (Jackhammer) or normal motility.
Complementary Motility Tools
Chicago Classification v4.0 (HRM)
Distal Contractile Integral (DCI) Calculator
Timed Barium Swallow Interpretation
The Evidence
Chicago v4.0 Core Reference
Esophageal motility classification on HRM: The Chicago Classification version 4.0.
Yadlapati R et al. • Neurogastroenterology & Motility. 2021;33(1):e14058. Definitive international consensus for IRP usage.
View Source• . ;
Origins & History
Evolution from "LES Pressure"
In the era of conventional manometry, we measured "Resting LES Pressure." Peter Kahrilas and his team recognized that the "residue" of pressure during relaxation (IRP) was a far more powerful predictor of bolus transit failure than the baseline resting tone.
Last Comprehensive Review: 2026-07-17