Definition, Etiology, PathogenesisTop
Achalasia is the most common (>70% of cases) primary esophageal motility disorder of unclear etiology characterized by impairment of lower esophageal sphincter (LES) relaxation and lack of a primary peristaltic wave in the esophageal body. An increase in resting LES pressure may also be present. Impairment of LES relaxation is probably caused by damage to and decrease in the number of postganglionic inhibitory neurons of the esophageal myenteric plexus (Auerbach plexus), which are responsible for relaxation of the LES. As the disease progresses, an esophageal stricture develops, which in turn leads to dilation of the esophageal lumen and marked thinning of the esophageal wall above the hypertrophic LES.
Clinical Features and Natural HistoryTop
The most typical feature is dysphagia, which is initially limited to solid foods and later includes liquids. It may be accompanied by regurgitation, chest pain, heartburn, chronic cough, and aspiration. Dysphagia leads to weight loss and malnutrition, while regurgitation may cause aspiration pneumonia and lung abscess. Other complications include esophagitis, development of diverticula of distal parts of the esophagus, and bleeding (rare). After 15 to 25 years, the risk of developing squamous cell carcinoma of the esophagus is ~30 times higher than in the general population.
1. Barium esophagography reveals a beak-like appearance of the distal esophagus with smooth outlines of the walls that sharply taper downwards to the closed LES.
2. Endoscopy is necessary to exclude other causes of the stricture, particularly esophageal cancer, which may have similar symptoms (eg, dysphagia and weight loss). It also helps to exclude hiatal hernia, which may present as dysphagia but requires different treatment. In advanced achalasia the esophagus is atonic, dilated, and tortuous, and its mucosa is damaged due to chronic irritation by residual food (erythema, fragility, ulcerations, candidiasis). The LES keeps closed and does not open with insufflation of air into the distal esophagus, although passage of the endoscope to the stomach is possible with slight resistance. Marked resistance to passage of the endoscope and stiffening of the cardia suggest other causes (postinflammatory stricture, cancer).
3. Esophageal manometry reveals impaired LES relaxation with elevated LES integrated relaxation pressure and 100% failed peristalsis (absence of peristalsis; no contractions) or spastic contractions in the esophageal body. The LES may show normal or increased resting pressure.
Diagnosis is based on barium esophagography and endoscopy. Esophageal manometry is performed to confirm diagnosis. Increased resting pressure of the LES is not a prerequisite for diagnosis.
Other causes of dysphagia. History and endoscopy are the basis of differential diagnosis.
1. Avoidance of foods that are difficult to swallow; in some patients soft (blended, minced, or pureed) foods may be recommended. Hot water (50 degrees Celsius) may help to relax the LES.
2. Lifestyle modifications such as elevated bedhead to prevent aspiration with food retained in the esophagus.
Drugs relaxing the smooth muscle of the LES and esophageal body supplement surgical or endoscopic treatment. Isosorbide dinitrate 5 to 20 mg or nifedipine 10 to 30 mg administered sublingually 10 to 30 minutes before a meal (duration of action, ~1.5 hours) are used. The benefit is not durable.
1. Pneumatic balloon dilation of the LES weakens the LES by circumferential stretching or tearing of its muscle fibers. It should be performed by an experienced endoscopist. The efficacy may last 12 to 24 months and retreatment is required for symptom recurrence in >50% of patients over a 5-year period. Complications include esophageal perforation, upper gastrointestinal bleeding, reflux esophagitis, intramural hematomas, esophageal mucosal tears, aspiration pneumonia, and diverticula at the gastric cardia. Postprocedural fever and postprocedural chest pain can be self-limiting.
2. Intrasphincteric injection of botulinum toxin during endoscopy paralyses the LES by poisoning the excitatory (acetylcholine-releasing) neurons that increase the LES smooth muscle tone, thereby reducing LES resting pressure.
3. Peroral endoscopic myotomy (POEM) is a longitudinal cut of the esophageal muscle with a special knife inserted through the gastroscope. The procedure is performed under general anesthesia with endotracheal intubation. Myotomy is performed inside the esophagus with subsequent closure of the esophageal mucosa. Leakage of air and esophageal fluid may complicate the procedure.
Cardiomyotomy (Heller myotomy) has been the primary alternative to pneumatic dilation for achalasia. It is a longitudinal incision of the muscle fibers of the LES and cardia. Heller myotomy is usually performed laparoscopically and is frequently combined with partial fundoplication to reduce the risk of symptomatic gastroesophageal reflux. The advantages of surgical myotomy are high initial success rates and, compared with pneumatic dilation, lower rates of symptom recurrence. Indications include stricture of the cardia that blocks passage of the endoscope to the stomach and age <30 years; the procedure is also indicated in situations when multiple sessions of esophageal dilation will probably be necessary. The main complication is gastroesophageal reflux. In certain cases (eg, severe esophageal dilation) esophageal resection may be indicated.
The majority of patients require multiple endoscopic procedures (dilation, injection of botulinum toxin) or myotomy (endoscopic or surgical), which are often only partially effective. Even after successful treatment the risk of developing esophageal cancer is probably increased, which is why some authors advise periodic endoscopic follow-up.