Related narrative: Laparoscopic Heller Esophagomyotomy
Achalasia (Gr.) means failure of relaxation and refers specifically to failure of the lower esophageal sphincter (LES) to reflexively relax appropriately on swallowing. Idiopathic achalasia occurs in 1-2:200,000 per year, affects both sexes equally and usually arises in the 4th-5th decades of life. There is also a disorder of generalized esophageal body contractility in this condition that is of secondary importance to the LES defect. The body of the esophagus exhibits simultaneous, non-propulsive contractions on barium swallow and manometry. The defect appears seated in the myenteric plexus of Auerbach between the longitudinal and circular muscle layers where the number of neuronal cells are depleted. There have also been vagal trunk and nucleus defects noted in some cases. The loss of inhibitory myenteric neurons leads secondarily to thickening of the inner circular muscle layer at the LES. The continuous tonic contraction of the LES gives a characteristic unrelieved birds-beak appearance on barium swallow. Etiology is unknown, with viral and genetic theories unlikely and an autoimmune factor possible in light of the finding of antibodies to myenteric neurons in some cases. The progression of the disease is gradual, making early differentiation from other esophageal motility and obstructive conditions difficult. With time the esophagus dilates and symptoms become more dramatic. The classic triad consists of dysphagia, regurgitation and weight loss. The retained esophageal contents in advanced disease harbor increasingly pathogenic bacterial flora posing an increasing risk of life-threatening aspiration.
X-ray findings of dilatation are proportional to the degree of disease. In late stages the esophagus may be massively dilated and tortuous with an air fluid level indicative of retained food. Manometry is most helpful in early stage diagnosis. It may show failure of LES relaxation, low amplitude simultaneous contractions, and absence of propulsive peristalsis. With a large esophageal food load, the esophageal pressure may exceed the intragastric pressure, a reversal of the normal physiological condition. A small subset of patients may have higher amplitude contractions of the esophageal body, a condition that has been termed vigorous achalasia. The clinical significance of this variation is minimal. Esophagoscopy is of benefit to rule out a mechanical cause of obstructive symptoms, such as stricture and tumor. The reddish purple esophagitis due to retention is usually distinguishable from signs of reflux esophagitis. The puckered, closed LES usually yields to gentle pressure, allowing the scope to enter the stomach, vs. the fixed defects of stricture and tumor. Unfortunately, tumors at the esophagogastric junction are often infiltrating and difficult to detect visually. Repeated examination and biopsy may be necessary. Such tumors may produce a physical narrowing, or infiltrate the neural plexus and cause a secondary physiological effect (pseudoachalasia). Achalasia must be differentiated from a variety of malignant and non-malignant conditions (see references). Malignancy remains the major concern, and is more likely when duration of symptoms has been short (< 6 mo), the patient is older, and the weight loss has been rapid.
Treatment is purely palliative in that there is no way to restore normal neuromuscular function. The aim is to facilitate emptying, reduce dilatation, reduce the risk of aspiration, and relieve symptoms. The means of treatment include pharmacotherapy, botulinum toxin, forceful pneumatic dilatation and esophagomyotomy.
Approximately 70% of individuals will have a response to smooth muscle relaxants. Short acting agents like amyl nitrite may produce a rapid response, but longer acting agents like sublingual isosorbide dinitrate (5-10 mg before meals) are more clinically relevant. Side effects, particularly headache, precludes long-term use in 1/3 of patients. Oral ingestion has fewer side effects, but is less effective, probably because of delayed absorption in the pool of esophageal contents.
Calcium channel blockers block uptake of calcium needed for smooth muscle contraction, and works best in patients with minimal dilatation. The long-term benefits are limited and this therapy does not prevent the progression to dilatation and complications. Pharmacologic therapy has a greater effect on symptoms than on emptying.
In recent years, the toxin of clostridium botulinum has been applied to the LES dysfunction of achalasia. Botox was initially used for focal dystonias, and is injected endoscopically into the LES. The toxin binds to presynaptic cholinergic receptors and is taken into the cell where it causes irreversible inhibition of acetylcholine release. Paralysis of the smooth circular muscle of the LES occurs over several days, and 60-75% of individuals have an initial response. Effects may last up to one year, when regrowth of axonal sprouts result in return of muscle function. Repeat injection may be effective, but fibrosis may result. It may be useful for a patient who is not a candidate for dilatation or surgery, but it is not considered a cost-effective long-term strategy at this time.
Bougie dilatation has a very transient benefit, measured in days, and forceful dilatation is necessary to achieve more durable results. In order to tear the circular muscle, it is necessary to forcefully dilate the LES to 3 cm. This is accomplished with a volume-limited, pressure-controlled Gruntzig-type balloon applying rapid inflation to 300 torr and holding it for 15 seconds. The major morbidity of the procedure is esophageal rupture (3%), and patients are evaluated immediately post-procedure with a water-soluble contrast study, and observed for late perforation over the next 6 hours. Small perforations without signs of general toxicity can often be managed non-operatively with NPO, antibiotics and observation. Thoracotomy is required for more significant perforation. Forced dilatation is effective in 60-95% of patients. An additional 10% of patients with sub-optimal results on the first dilatation will benefit from a second dilatation. Dilatation is less effective than myotomy, and most patients who come to myotomy will have had at least one unsuccessful balloon dilatation.
Esophagomyotomy, described by Heller in 1913 as an open transthoracic procedure, aimed at reducing LES pressure without leaving the esophagus vulnerable to reflux complications. Debate continues about the extent and completeness of myotomy. Heller opened the left chest through the 6th or 7th interspace and incised 7-10 cm of lower esophageal muscle from the inferior pulmonary vein to the esophagogastric junction, and extended the incision 3-5 cm onto the stomach. The vagus nerve was carefully preserved. A lower morbidity was achieved with a thoracoscopic approach in the modern era, and the laparoscopic approach has generally superseded the thoracoscopic approach (see laparoscopic esophagomyotomy). The myotomy is usually complemented with a partial (Toupe) 270 degree fundoplication. Complete 360-degree fundoplication (see laparoscopic fundoplication video), even if very loose, has an increased risk of causing persistent obstructive symptoms due to the compromised esophageal motility. Esophagomyotomy results in the highest success rate and most durable results of the treatment options. Patients who go on to develop progressive disease and complications are candidates for transhiatal esophageal resection and gastric conduit replacement.
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