Akalasia

01Pathophysiology

Achalasia results from the progressive destruction of inhibitory ganglion cells within the myenteric (Auerbach) plexus of the esophageal wall. These neurons are responsible for releasing nitric oxide (NO) and vasoactive intestinal peptide (VIP), which are the neurotransmitters that signal the lower esophageal sphincter (LES) to relax during swallowing. When these neurons degenerate, the LES loses its ability to relax in a coordinated fashion, and the esophageal body loses its normal peristaltic contractions.

The cause of this neuronal loss in primary (idiopathic) achalasia remains unclear, though current evidence points toward an autoimmune or inflammatory process targeting the myenteric plexus in genetically susceptible individuals. In secondary achalasia, the best-known cause is Chagas disease, where Trypanosoma cruzi directly invades and destroys the myenteric ganglia. This is a frequently tested association, particularly in vignettes describing a patient who has emigrated from South America.

The clinical consequences follow directly from the pathophysiology. Because the LES cannot relax, a functional obstruction develops at the gastroesophageal junction. This produces dysphagia to both solids and liquids from the onset, which is the cardinal feature that distinguishes achalasia from a mechanical obstruction (where dysphagia typically begins with solids and progresses to liquids over time). Food and secretions accumulate in the esophagus, which gradually dilates and loses its tone, leading to regurgitation of bland, undigested food (not acidic, because it never reached the stomach). Stasis of food also raises the long-term risk of squamous cell carcinoma of the esophagus, a testable pearl.

Chest pain in achalasia is thought to arise from esophageal distension and non-peristaltic (spastic) contractions of the esophageal body. This pain can mimic cardiac chest pain and is another exam favorite.

02Classification and Clinical Manifestation

Achalasia is classified using the Chicago Classification (version 4.0) of esophageal motility disorders, based on high-resolution manometry (HRM) findings. This classification has direct treatment implications and is increasingly tested.

All three subtypes share the hallmark finding of impaired LES relaxation, defined by an elevated integrated relaxation pressure (IRP) above $15mmHg15\backslash \; mmHg$ on HRM.

Clinical manifestations across all subtypes include:

03Diagnostic Workup

The workup for achalasia follows a logical sequence. When a patient presents with progressive dysphagia to both solids and liquids, the best initial test is a barium esophagogram. This study is noninvasive, widely available, and often reveals the classic "bird's beak" appearance: a dilated esophageal body with a smooth, tapered narrowing at the gastroesophageal junction. The esophagus may also show an air-fluid level from retained food and secretions.

If the barium swallow is suggestive, the next step is esophageal manometry, which is the gold standard. Manometry directly measures the motility pattern of the esophageal body and the relaxation of the LES. The diagnostic criteria require incomplete LES relaxation (elevated IRP) and aperistalsis of the esophageal body. This is the only test that can definitively confirm achalasia and subtype it according to the Chicago Classification.

Upper endoscopy (EGD) must be performed in all patients before treatment, even if manometry is diagnostic. The reason is to exclude pseudoachalasia, which is a malignant tumor (most commonly gastric cardia or distal esophageal adenocarcinoma) infiltrating the myenteric plexus and mimicking achalasia. Exam vignettes testing pseudoachalasia typically describe an older patient with rapid symptom onset and significant weight loss. If endoscopic findings or clinical suspicion are concerning, a CT scan should follow.

04Management and Treatment

The management of achalasia is centered on reducing the outflow obstruction at the LES because the underlying neuronal damage cannot be reversed. No therapy restores normal peristalsis.

For patients who are reasonable candidates for intervention, the two established definitive treatments are pneumatic balloon dilation and laparoscopic Heller myotomy. Both have strong evidence, and the choice often depends on patient preference, local expertise, and achalasia subtype. Type II achalasia responds best to both approaches. For Type III (spastic) achalasia, myotomy (particularly POEM, which allows a longer myotomy) tends to outperform dilation.

Laparoscopic Heller myotomy involves surgically dividing the muscle fibers of the LES. A partial fundoplication (usually a Dor anterior wrap) is added to prevent gastroesophageal reflux, which otherwise occurs in up to 30% of post-myotomy patients. This is a commonly tested "next step" detail: myotomy without fundoplication leads to significant reflux.

Pneumatic dilation uses a balloon to forcefully stretch and disrupt the LES muscle fibers. The main risk is esophageal perforation (2 to 5%), and patients should be counseled about this. A post-dilation barium swallow or CT is obtained if perforation is suspected.

POEM (peroral endoscopic myotomy) is increasingly adopted and has shown results comparable to Heller myotomy. The primary downside is a higher rate of post-procedural gastroesophageal reflux because an antireflux procedure cannot be performed during the same endoscopic session. Patients undergoing POEM typically require long-term proton pump inhibitor therapy.

Botulinum toxin injection into the LES is reserved for patients who cannot undergo dilation or surgery. It works by inhibiting acetylcholine release at the remaining excitatory nerve endings, effectively reducing LES tone. The effect is temporary (lasting approximately 6 to 12 months), and repeated injections can cause fibrosis that complicates future surgical intervention.

Pharmacotherapy with calcium channel blockers (nifedipine) or nitrates (isosorbide dinitrate) provides the least effective relief and is considered a last resort. These agents relax smooth muscle and transiently lower LES pressure, but they do not address the underlying obstruction meaningfully.

05Differential Diagnosis and Distractors

06Traps and High-Yield Pearls

The single most important concept tested about achalasia is the pattern of dysphagia. The exam will present a patient with dysphagia and expect you to recognize that simultaneous difficulty with both solids and liquids points to a motility (functional) disorder, whereas progressive dysphagia starting with solids alone points to a mechanical obstruction. Students who do not apply this distinction reliably will select esophageal stricture or cancer instead of achalasia.

The second common trap involves pseudoachalasia. Vignettes describing an older patient (over age 60) with a short duration of symptoms, rapid weight loss, or a history of malignancy should raise suspicion. Even if the barium swallow and manometry appear consistent with achalasia, the correct next step in that clinical context is upper endoscopy with biopsies and possibly CT imaging to rule out a GEJ malignancy.

Another frequently tested pearl is the distinction between achalasia and scleroderma esophagus. Both show absent peristalsis on manometry, and this is where students get confused. The discriminator is the LES pressure: achalasia has a hypertensive, non-relaxing LES, while scleroderma has a hypotensive, incompetent LES leading to severe reflux.

Students should also be aware that achalasia causes regurgitation of bland, undigested food (not acidic stomach contents). When a vignette describes heartburn in an achalasia patient, the mechanism is fermentation of retained food producing lactic acid, not true gastric acid reflux. Misidentifying this as GERD leads to an incorrect treatment plan.

Finally, remember that achalasia carries a long-term increased risk of squamous cell carcinoma of the esophagus (not adenocarcinoma). This risk stems from chronic mucosal irritation due to food stasis, and it is an association the exam expects you to know.