There are very few well-defined esophageal motility disorders and thus the introduction of the nutcracker esophagus concept during the late 1970s gained rapid popularity among “motilists” and the motor disorder since then has been well entrenched within the field of gastrointestinal motility.1,2 Some have suggested that the chosen term “Nutcracker esophagus” was the main impetus for the quick adoption of the disorder as it may infer significant pathophysiologic consequences. From its conception, nutcracker esophagus remained an area of intense controversy. The clinical value of making the diagnosis has been questioned, resulting in contentious editorials.3
The evolution of nutcracker esophagus is a great prelude to the interesting article by Agrawal and colleagues.4 Originally, the disorder was defined as mean amplitude peristaltic contractions above 120 mm Hg.1 However, this criterion was based on normal data obtained from 20 young, healthy volunteers with a mean age of 25 years.5 Later, investigators concluded that this was an inappropriate control group and thus embarked on a new study, this time including patients from different age groups. Using the original criteria for nutcracker esophagus, which required average distal peristaltic contractions greater than 2 SDs above a normal mean, a value greater than 180 mm Hg was adopted. Subsequently, studies have demonstrated a variety of pathophysiologic abnormalities in patients with this disorder, further cementing its importance as a separate clinical entity. They include prolonged esophageal bolus transit time, autonomic dysregulation with defects in both parasympathetic and sympathetic function, and food impaction.6–8 Several case reports even demonstrated progression of nutcracker esophagus to achalasia or diffuse esophageal spasm, directly tying the disorder to the other spastic esophageal motor disorders.9–11 By demonstrating that nutcracker esophagus is by far the most common esophageal motility abnormality documented in patients with noncardiac chest pain (NCCP), the disorder attracted growing attention, making it an important target for pharmacologic, endoscopic, and surgical intervention.12–16
In the last decade, further information that has been accumulated about the disorder resulted in questioning the necessity of making the diagnosis of nutcracker esophagus and its ultimate clinical relevance. Studies have demonstrated that nutcracker esophagus does not appear to be the most common motility disorder documented in the general NCCP patient population, but rather hypotensive lower esophageal sphincter.17 Furthermore, several studies suggested that in most cases, concomitant gastroesophageal reflux is the underlying cause for patients' chest pain and not the peristaltic phenomenon.18,19 Most disconcerting were the studies demonstrating a very limited symptomatic response of patients with NCCP and nutcracker esophagus to various smooth muscle relaxants as compared with the high efficacy of visceral analgesics.20 The aforementioned findings resulted in several commentaries suggesting that nutcracker esophagus is “much to do about nothing.”3,21
However, the pendulum has swung back again with the introduction of endoscopic ultrasound and high-frequency intraluminal ultrasonography. Thickening of the muscularis propria layer predominantly at the distal portion of the esophagus was reported in a subset of patients with nutcracker esophagus, suggesting that an esophageal anatomic abnormality may be responsible for the high-amplitude contractions.22,23 These studies challenged the traditional definition of nutcracker esophagus and indirectly supported the need for determining the true threshold for diagnosing the disorder. Consequently, the study by Agrawal et al is timely and highly important for the proper position of the disorder and we congratulate the authors for taking the lead on such a controversial issue.
In their study, Agrawal and colleagues performed a retrospective analysis of multichannel intraluminal impedance and pH test results of 56 patients with documented nutcracker esophagus. Because of the retrospective nature of the study, not all patients underwent both procedures. The patients were arbitrarily divided into 3 groups on the basis of the values of their esophageal amplitude contractions (A—180 to 220 mm Hg, B—>220 to 260 mm Hg, and C—>260 mm Hg). The 3 main findings of the study are the presence of chest pain in 100%, 69%, and 23%, median bolus transit time of 5.8, 5.9, and 6.5 seconds, as well as abnormal pH test in 29%, 70%, and 77% of the patients from groups C, B, and A, respectively. On the basis of their results, the authors suggested revising the definition of nutcracker esophagus and including patients with distal esophageal amplitude contractions of at least 260 mm Hg and possibly those with ≥220 mm Hg.4
Although the study is afflicted with various shortcomings, which in fact are recognized by the authors in the discussion, the conclusion provided is in the right direction. The small number of subjects enrolled, the retrospective nature of the study, lack of follow-up, and absence of data reproducibility, all impede the prompt adoption of the new diagnostic threshold offered by the authors. This is compounded by the lack of understanding of the natural course of nutcracker esophagus and the true relationship between the disorder and gastroesophageal reflux disease. The addition of esophageal ultrasonography to a prospective design of a similar study could have provided a unique opportunity to correlate the height of amplitude contractions with the results of the different physiologic parameters evaluated by the current study. This was also suggested by Pehlivanov et al,24 who demonstrated a close correlation between baseline esophageal muscle thickness and peak pressure in patients with nutcracker esophagus.
The results of the study do not provide a clear-cut new threshold for diagnosing nutcracker esophagus, but do support abandoning the traditional definition (>180 mm Hg). In contrast, it is likely that patients with esophageal amplitude contractions greater than 260 mm Hg should be termed as having nutcracker esophagus. However, using this article, we propose that it is time to rid ourselves of the term nutcracker esophagus. It is confusing to patients and physicians who are not gastroenterologists.
Although we focus exclusively on the height of esophageal amplitude contractions when we think of nutcracker esophagus, a recent paper has suggested that there is more to the story. Using high-frequency intraluminal ultrasonography, Hwoon-Yong demonstrated a functional abnormality in patients with nutcracker esophagus—asynchrony between the circular and the longitudinal muscle during esophageal contraction.25 The latter suggests that future considerations of the diagnosis of nutcracker esophagus are unlikely to solely rely on the height of esophageal amplitude contractions.
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