Achalasia is one of those “if you know the mechanism, you’ll never miss the question” GI disorders. Step 1 loves it because it’s a clean, testable failure of neural control: the esophagus can’t move food forward and the lower esophageal sphincter (LES) won’t relax—so patients get progressive dysphagia, a classic barium swallow, and manometry findings you should recognize on sight.
What Is Achalasia?
Achalasia is an esophageal motility disorder characterized by:
- Impaired relaxation of the LES
- Loss of peristalsis in the distal esophagus
In plain terms: the “door” (LES) stays shut and the “conveyor belt” (peristalsis) is broken.
High-yield definition:
Failure of LES relaxation + aperistalsis due to loss of inhibitory neurons in the myenteric (Auerbach) plexus.
Pathophysiology (The Step 1 Core)
Normal physiology (what’s supposed to happen)
Swallowing triggers inhibitory neurons in the myenteric plexus to release NO (nitric oxide) and VIP, causing:
- LES relaxation
- Coordinated peristalsis
Achalasia physiology (what goes wrong)
Achalasia results from degeneration of inhibitory ganglion cells in the myenteric (Auerbach) plexus, leading to:
- ↓ NO and ↓ VIP
- ↑ LES tone (fails to relax)
- Aperistalsis in the distal esophagus
- Progressive esophageal dilation proximal to the LES
Primary vs secondary achalasia
- Primary (idiopathic): most common; presumed autoimmune/inflammatory degeneration of myenteric neurons
- Secondary: classic association is Chagas disease
- Trypanosoma cruzi damages the myenteric plexus → achalasia-like picture and megacolon
First Aid cross-reference: GI → Esophagus → Achalasia; Micro → Chagas disease (T. cruzi).
Clinical Presentation (How It Shows Up on Exams)
Key symptoms
- Progressive dysphagia to both solids and liquids
- This is a major Step clue: motility disorder = solids + liquids
- Regurgitation of undigested food, especially at night
- Chest pain (can mimic angina)
- Weight loss (variable; more concerning if rapid/severe—think pseudoachalasia)
- Aspiration symptoms: cough, recurrent pneumonias, nocturnal choking
“Classic patient story”
Middle-aged patient with months of dysphagia to solids and liquids, regurgitation, and a barium swallow showing “bird’s beak.”
Diagnosis (Know the Big 3 Tests)
1) Barium swallow (esophagram)
Classic finding: “Bird’s beak” tapering at the distal esophagus with proximal dilation.
| Test | What you see in Achalasia | Why it matters |
|---|---|---|
| Barium swallow | Bird’s beak distal narrowing + dilated esophagus | Great first visual clue on exams |
| Manometry (gold standard) | ↑ LES resting tone, incomplete LES relaxation, aperistalsis | Confirms diagnosis |
| Endoscopy | Often retained food/secretions; helps exclude malignancy | Important to rule out pseudoachalasia |
2) Esophageal manometry (gold standard)
You’re looking for:
- Failure of LES relaxation
- Increased LES resting pressure
- Absent peristaltic waves in the distal esophagus
3) Upper endoscopy (EGD): rule-out step
EGD is commonly performed to:
- Exclude esophageal/gastric cardia cancer causing pseudoachalasia
- Evaluate for other structural lesions
Pseudoachalasia clue: older patient, rapid weight loss, short symptom duration → think malignancy until proven otherwise.
Treatment (What Step Wants You to Pick)
Treatment aims to reduce LES pressure. There’s no “neuron regrowth” fix—so we mechanically/chemically relax or disrupt the LES.
First-line definitive options
- Pneumatic balloon dilation
- Endoscopic dilation to disrupt LES muscle fibers
- Heller myotomy
- Surgical myotomy of LES (often combined with partial fundoplication to reduce GERD)
Newer/commonly tested option
- POEM (Peroral Endoscopic Myotomy)
- Endoscopic myotomy; effective, increasingly used
- GERD can be a notable complication (similar issue: reduced LES barrier)
Medical therapy (usually for poor surgical candidates)
- Nitrates (increase NO effect) or calcium channel blockers (smooth muscle relaxation)
- Botulinum toxin injection into LES
- Inhibits ACh release → decreases LES contraction
- Often temporary; used in older/high-risk patients
Quick treatment table
| Approach | Mechanism | When used | Trade-offs |
|---|---|---|---|
| Pneumatic dilation | Tears LES muscle | Common definitive therapy | Risk of perforation |
| Heller myotomy | Cuts LES muscle | Durable definitive therapy | Post-op GERD risk |
| POEM | Endoscopic myotomy | Effective, minimally invasive | GERD risk |
| Botulinum toxin | ↓ ACh → ↓ LES tone | Poor surgical candidates | Short-lived benefit |
| Nitrates/CCBs | Smooth muscle relaxation | Symptom control | Limited efficacy/side effects |
High-Yield Associations & Test Traps
1) Dysphagia: solids vs liquids
- Solids then liquids (progressive): structural obstruction (e.g., cancer, stricture)
- Solids + liquids from the start: motility disorder (achalasia, diffuse esophageal spasm, scleroderma)
2) Achalasia vs GERD (opposite LES problem)
- Achalasia: ↑ LES tone, poor relaxation, regurgitation of undigested food
- GERD: ↓ LES tone, acid reflux, heartburn
3) Achalasia vs scleroderma esophagus (both are motility issues, but opposite LES tone)
| Feature | Achalasia | Scleroderma esophagus |
|---|---|---|
| LES tone | Increased | Decreased |
| Peristalsis | Decreased/absent | Decreased |
| Primary symptom | Dysphagia + regurgitation | GERD symptoms + dysphagia |
| Path | Loss of inhibitory neurons (NO/VIP) | Smooth muscle atrophy + fibrosis |
4) Chagas disease
- Trypanosoma cruzi can cause:
- Achalasia
- Megacolon
- Dilated cardiomyopathy
- Mechanism: destruction of enteric nervous system (myenteric plexus)
First Aid cross-reference: Micro → Protozoa → T. cruzi (Chagas); GI pathology → esophageal motility disorders.
5) Esophageal squamous cell carcinoma risk
Long-standing achalasia is associated with increased risk of esophageal squamous cell carcinoma, likely due to chronic stasis/irritation and inflammation.
Step-friendly takeaway:
Chronic achalasia → esophageal dilation + stasis → ↑ SCC risk.
Rapid-Fire “If You See This, Think Achalasia”
- Progressive dysphagia to solids and liquids
- Regurgitation of undigested food
- Nocturnal cough/aspiration
- Barium swallow: bird’s beak
- Manometry: increased LES tone + incomplete relaxation + aperistalsis
- Association: Chagas disease
- Complication: increased risk of esophageal SCC
Mini Self-Check (Step-Style)
1) What’s the neurotransmitter deficit in achalasia?
- ↓ NO and ↓ VIP from inhibitory myenteric neurons
2) Best diagnostic test?
- Esophageal manometry (gold standard)
3) Next step after suspected achalasia on barium swallow?
- Often EGD to rule out malignancy (pseudoachalasia), then confirm with manometry
4) Best definitive treatments?
- Pneumatic dilation, Heller myotomy, or POEM