Diagnosis
The diagnosis of achalasia is contingent on demonstrating impaired LES relaxation and absent peristalsis in the absence of partial esophageal obstruction near the LES by a stricture, tumor, vascular structure, implanted device (eg, LAP-BAND, Allergan, Inc., Irvine CA), or infiltrating process. Thus, the minimal requisite evaluation should include manometry to document the motor findings and appropriate imaging studies to rule out obstruction. There are many nuances to both evaluations to keep in mind. Straightforward cases are straightforward, but the increasing sophistication of diagnostic methods has led to increasing recognition of variations in the physiological manifestations of achalasia and of alternative disease processes that can mimic the disease.
With regard to esophageal manometry, a major technological evolution has occurred during the last decade wherein conventional water perfused or strain gauge systems with a polygraph and line tracing output have been replaced by high-resolution manometry (HRM) systems outputting pressure data in esophageal pressure topography (EPT). Nowhere has this evolution had more impact than in the diagnosis of achalasia. Diagnostic criteria have been tightened, and relevant physiological subtypes have been identified. Particularly instrumental in establishing uniform diagnostic criteria for achalasia was the development of a new metric devised for EPT to quantify esophagogastric junction (EGJ) relaxation, the integrated relaxation pressure (IRP). Measurement of the IRP uses an electronic sleeve sensor initially described by Clouse and Staino and conceptually similar to a Dent sleeve that compensates for potential LES movement by tracking the sphincter within a specified zone. This avoids the artifact of pseudorelaxation (apparent sphincter relaxation caused by elevation of the sphincter above the sensor, displacing it into the stomach), which was a fatal flaw in the assessment of LES relaxation with nonsleeve conventional systems. The IRP is calculated from the electronic sleeve as the mean of 4 seconds of maximal EGJ relaxation after the pharyngeal contraction. The time scored can be continuous or noncontinuous, as when it is interrupted by a crural diaphragm contraction. The IRP provides a robust and accurate assessment of deglutitive EGJ relaxation and optimally discriminates defects of sphincter relaxation characteristic of achalasia.
Before the introduction of HRM and EPT, there were no data substantiating the prognostic value of conventional manometric measures in achalasia, although there were qualitative descriptions of variants such as vigorous achalasia, achalasia with preserved peristalsis, and cases with complete or partial LES relaxation. There were no established conventions for making these measurements. However, with the adoption of HRM with EPT, 3 distinct subtypes of achalasia were quantitatively defined by using novel EPT metrics (Figure 1). Furthermore, there are now 5 publications supporting the prognostic value of these achalasia subtypes that consistently observe that (1) type II patients have the best prognosis with myotomy or pneumatic dilation, (2) the treatment response of type I patients is less robust (and reduced further as the degree of esophageal dilatation increases), and (3) type III patients have a worse prognosis, likely because the associated spasm is less likely to respond to therapies directed at the LES. In addition, patients with impaired EGJ relaxation but some preserved peristalsis (Figure 2) are now recognized as a distinct entity that can be a variant phenotype of achalasia. However, EGJ outflow obstruction can also be a manifestation of other disease entities including eosinophilic esophagitis, LES hypertrophy, strictures, paraesophageal hernia, and pseudoachalasia that is due to tumor infiltration. Consequently, this finding always mandates carefully imaging (often with biopsies) the EGJ. Table 1 contrasts the defining manometric measures of achalasia in conventional and EPT terms. Highlighted in Table 1 is the finding that threshold values for abnormal deglutitive EGJ relaxation by using the IRP are altered by the pressurization pattern in the esophageal body such that a value above 10 mm Hg is abnormal in type I patients and that panesophageal pressurization is diagnostic of type II achalasia, independent of the IRP value.
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Figure 1.
Subtypes of achalasia. The 3 subtypes are based on esophageal body contractility and pressurization. Type I (left) is associated with absent peristalsis and no discernible esophageal contractility in the context of an elevated IRP. The esophagus is flaccid with some degree of dilatation as evidenced by the associated esophagogram. The IRP threshold value for impaired EGJ relaxation in type I (>10 mm Hg) is lower than for type II or III because there is no potential for esophageal body pressurization. Type II (center) is associated with abnormal EGJ relaxation and panesophageal pressurization in excess of 30 mm Hg. This pressurization is likely related to longitudinal muscle and (nonocclusive) circular contraction compressing the esophageal body compartment. In this example, the proximal esophagus is filled by air, which is evident by the associated esophagogram and the overlying impedance signal showing liquid (purple transparency) only in the distal esophagus. Type III achalasia (right) is associated with premature (spastic) contractions and impaired EGJ relaxation. The diagnostic criteria stipulate that at least 2 swallows be associated with a contraction with distal latency of less than 4.5 seconds; other swallows may have absent peristalsis or rapid contractions, and as in this example, panesophageal pressurization can also be seen. As in this example, the associated esophagogram for type III achalasia is often interpreted as esophageal spasm because this has an extreme corkscrew with a small diverticulum above the distal contraction. With permission from the Esophageal Center at Northwestern.
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Figure 2.
The criteria for EGJ outflow obstruction are an abnormal EGJ relaxation pressure associated with some preserved weak or normal peristalsis, thereby not meeting the diagnostic criteria for types I, II, or III achalasia. Ultimately, this pattern may prove to be a phenotype of achalasia as in the case of (A), where the patient also had a large epiphrenic diverticulum. This patient was treated with a laparoscopic myotomy and diverticulectomy, with a good symptomatic and functional response. In contrast, EGJ outflow obstruction can also be associated with mechanical obstruction in the region of the EGJ, as proved to be the case with the patient illustrated in (B). The patient was reported to have a patulous EGJ, and a 9-mm endoscope passed with no resistance noted at the EGJ. However, the IRP was abnormal, and there was compartmentalized pressurization between the preserved peristaltic contraction and the EGJ. The associated esophagogram revealed a subtle stricture just proximal to the EGJ where passage of a 12.5-mm barium tablet was delayed. The patient responded to 18-mm balloon dilation and proton pump inhibitor therapy. With permission from the Esophageal Center at Northwestern.
The other requisite evaluation to establish a diagnosis of achalasia is of imaging studies to rule out obstruction in the region of the EGJ. In most instances, endoscopy will suffice. Endoscopy may also be helpful in determining the degree of esophageal dilatation, whether there is significant esophageal retention of food and fluid, and whether there is coexistent stasis or fungal esophagitis. A barium esophagogram may suffice in this capacity in instances that there are equivocal manometric findings or when manometry is not feasible because of severe dilatation and an inability to intubate the stomach with the manometry catheter. The esophagogram can also quantify the efficacy of esophageal emptying when done as a timed barium esophagogram protocol. When suspicion of pseudoachalasia is high, endoscopic ultrasound and/or computed tomography may be necessary. Figure 3 illustrates such an example in which endoscopic ultrasound implicated an aortic aneurysm as the ultimate cause of a pseudoachalasia syndrome.
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Figure 3.
Pseudoachalasia. The patient was referred for HRM on the basis of a presumed diagnosis of achalasia from the timed barium esophagogram noting a dilated esophagus with esophageal retention at 5 minutes and a bird beak deformity at the EGJ. Although the patient met criteria for type I achalasia, there was a strong vascular signal noted on the EPT plot that raised suspicion for vascular compression. Endoscopic ultrasound revealed a large thoracic aneurysm compressing the distal esophagus. The patient underwent repair of the aneurysm, and her esophageal function subsequently improved with no esophageal retention on esophagogram. With permission from the Esophageal Center at Northwestern.