Achalasia and oesophageal motility disorders

• Achalasia is an incurable motility disorder in which the inhibitory nerve cells of the myenteric plexus of the distal oesophagus and lower oesophageal sphincter are lost, so the sphincter does not relax and peristalsis fails. Food accumulates and the oesophagus slowly stretches.
• Most cases are primary (idiopathic); the rest are secondary, mainly Chagas disease (chronic Trypanosoma cruzi infection, common in Latin America) and, uncommonly, pseudoachalasia from a cancer at the gastro-oesophageal junction.
• Patients present with progressive dysphagia to both solids and liquids, regurgitation of undigested food, chest pain and weight loss. The diagnosis is confirmed by high-resolution manometry.
• A barium swallow shows a dilated oesophagus with bird-beak narrowing; endoscopy is done first to exclude cancer.
• Definitive treatment disrupts the sphincter: pneumatic dilation, laparoscopic Heller myotomy or peroral endoscopic myotomy (POEM). Botulinum toxin and tablets are reserved for those unfit for definitive therapy. Treated patients need reflux control and, in practice, surveillance for the small oesophageal cancer risk.

By the end of this page you should be able to:

1. Explain normal swallowing and peristalsis, then describe what is lost in achalasia and how that produces symptoms.
2. Distinguish primary achalasia (including Chagas-related disease) from pseudoachalasia caused by cancer.
3. Interpret endoscopy, barium swallow and high-resolution manometry, and name the Chicago Classification version 4.0 subtypes.
4. Compare pneumatic dilation, Heller myotomy and POEM and choose among them by achalasia subtype and fitness.
5. Manage reflux after treatment and describe the oesophageal cancer risk.
6. Contrast achalasia with distal oesophageal spasm, hypercontractile (jackhammer) oesophagus, scleroderma and ineffective motility.
7. Apply these concepts in a low-resource setting, including Chagas-endemic practice.

"Achalasia" literally means "failure to relax", which is its core problem. It is not a narrowing from scarring or a growth. The food tube is structurally open, but its pump and valve do not work, so food and saliva accumulate and the oesophagus slowly stretches over months to years.

Achalasia is rare. Reported global incidence ranges from 0.03 to 1.63 per 100,000 persons per year and prevalence from 1.8 to 12.6 per 100,000 persons, with only 20,000 to 40,000 affected people in the United States.^[1] It occurs equally in men and women, with no racial predilection, and peak incidence is between 30 and 60 years of age.^[1] Most patients have idiopathic (primary) achalasia, with secondary disease accounting for the remainder, mainly Chagas disease (a major cause in Latin America)^[6] and uncommon pseudoachalasia from cancer.>>

A swallow has three phases: oral, pharyngeal and oesophageal. Once food leaves the pharynx, the upper oesophageal sphincter opens and the primary peristaltic wave takes over: a coordinated contraction that travels down the oesophageal body while the lower oesophageal sphincter relaxes. The vagus nerve and the myenteric (Auerbach) plexus coordinate this.

Two kinds of nerve signalling matter:

• Excitatory neurons release acetylcholine (and substance P), which contract the circular muscle.
• Inhibitory neurons release nitric oxide and vasoactive intestinal peptide, which relax the muscle ahead of the bolus and let the lower sphincter open.

In the healthy oesophagus there is a gradient: inhibition lasts longer distally, so the wave slows near the bottom and the sphincter stays open long enough for the bolus to pass. That timing is what high-resolution manometry measures as distal latency; a short (premature) contraction is spastic. The normal upper-to-lower sequence is why a normal swallow clears the oesophagus in seconds and why loss of inhibition converts this into a tube that simply does not empty.

The leading explanation is selective loss of the inhibitory neurons of the myenteric plexus in the distal oesophagus and lower sphincter, with excitatory neurons left intact and unopposed.^[1] Inhibitory neurons mainly release vasoactive intestinal peptide and nitric oxide.^[1] Without them, two things follow:

1. The lower sphincter cannot relax (or relaxes only partially), so it becomes a functional plug.
2. The propagating wave is replaced by absent or simultaneous contractions, so the oesophagus does not clear.

Because excitatory cholinergic signalling is preserved, sphincter pressure is often raised early in the disease, and the organised wave is progressively lost. Histology shows a chronic inflammatory infiltrate (T cells, eosinophils, mast cells and antibodies) with loss of ganglion cells and interstitial cells of Cajal in the myenteric plexus.^[5] Over years the oesophagus dilates and may become sigmoid or "megaesophagus", and food stasis becomes a problem in itself.

In Chagas disease, both excitatory and inhibitory enteric nerves are damaged, so sphincter pressure is actually lower than normal, whereas in idiopathic achalasia the excitatory innervation is preserved and pressure is higher than normal.^[6] The radiological picture is otherwise the same, usually with megaesophagus.

• Primary (idiopathic) achalasia: the common form described above, of unknown cause, with myenteric ganglion loss and usually a raised sphincter pressure.
• Secondary achalasia:
  • Chagas disease: chronic infection with Trypanosoma cruzi destroying the myenteric plexus. Presentation, manometry and treatment overlap with the idiopathic form; in endemic Latin American regions it is a major cause. Serology and the patient's origin (and features such as cardiomyopathy or megacolon) point to it.^[6]
  • Pseudoachalasia: an achalasia-like pattern produced by a tumour (usually adenocarcinoma of the gastro-oesophageal junction or stomach, but sometimes lung, breast and others) invading or compressing the sphincter or causing a paraneoplastic neuropathy. It mimics primary achalasia clinically, radiologically and manometrically. Clues are older age, shorter duration of symptoms (median 13 months versus 36 months in primary disease), severe weight loss, and difficulty passing the gastro-oesophageal junction at endoscopy.^[5] Tumours behind pseudoachalasia are esophageal, gastric or gastro-oesophageal junction neoplasms in about 46 percent, lung in 13 percent and breast in 6 percent.^[5] Endoscopy and biopsy can be falsely negative, so cross-sectional imaging and endoscopic ultrasound are often needed.^[5]

Symptoms develop slowly and are often blamed on reflux for years. Heartburn may be present in 27 to 42 percent of patients, so patients are frequently misdiagnosed as having gastro-oesophageal reflux disease and treated with proton pump inhibitors for a long time.^[1]

History:

• Progressive dysphagia to both solids and liquids from the outset. This is the classic pointer away from a mechanical stricture, where solids go first.
• Regurgitation of undigested food and saliva, often at night, which can be effortless and may resemble vomiting; nocturnal regurgitation predisposes to cough and aspiration.
• Heartburn in 27 to 42 percent, from bacterial fermentation of retained food producing lactic acid.^[1]
• Substernal chest pain, often with eating or with rapid drinking.
• Weight loss and nutritional deficiency in more advanced disease (variable); severe or rapid weight loss should raise pseudoachalasia.^[1]
• Halitosis and excessive salivation from oesophageal stasis.

Examination is usually normal; a tender fullness or succussion splash may be present only in advanced disease. Lower sphincter tone can sometimes be felt as resistance on passing the endoscope.

Red flags for pseudoachalasia in an elderly patient: significant short-term weight loss with suspected achalasia, which should prompt cross-sectional imaging or endoscopic ultrasound.^[1]

The main look-alikes are listed below. The first step in every patient with suspected achalasia is upper endoscopy to exclude a mechanical obstruction.

Upper endoscopy is always done first in suspected achalasia. It excludes a mechanical cause and looks for pseudoachalasia. Findings suggestive of achalasia include retained saliva and food, a dilated oesophagus, and puckering of the gastro-oesophageal junction that requires more than usual pressure to pass. Early disease can look almost normal. Endoscopy is also used after treatment to assess reflux or recurrence, and endoscopic injection of botulinum toxin is performed through the endoscope.

Patients who are initially suspected of having gastro-oesophageal reflux disease but do not respond to acid-suppressive therapy should be evaluated for achalasia.^[1]

A dilated oesophagus with a tapered bird-beak narrowing at the gastro-oesophageal junction is the classic appearance; retained barium above the junction confirms poor emptying. In the appropriate clinical presentation, timed barium esophagram showing retained barium and bird beaking may be diagnostic of achalasia.^[1]

Timed barium swallow, measured by column height at 1, 2 and 5 minutes after a large bolus, is the best practical test of emptying and of response to treatment: before therapy most patients retain barium at all three time points, and after effective therapy the oesophagus should be empty at 1 minute.^[1] A retained barium column greater than 5 cm at 5 minutes after treatment suggests incomplete emptying and close follow-up.

This is the gold standard. It measures three things: relaxation of the gastro-oesophageal junction (integrated relaxation pressure, IRP), contractile vigour of the oesophageal body (distal contractile integral, DCI) and the timing of the contraction (distal latency).

Normal adult values (Medtronic system): median IRP under 15 mmHg supine and under 12 mmHg upright; Laborie or Diversatek systems use under 22 mmHg supine and under 15 mmHg upright. A normal contraction has a DCI of 450 to 8000 mmHg·s·cm; panesophageal pressurisation is defined at 30 mmHg or more. A premature (spastic) contraction is a distal latency under 4.5 seconds with a DCI of at least 450. These values are reproduced from the Chicago Classification version 4.0.^[2]

The manometric subtypes of achalasia in Chicago Classification version 4.0 are:

• Type I: abnormal median IRP with 100 percent failed peristalsis (aperistalsis), with no panesophageal pressurisation. This is the second most common subtype, seen in 20 to 40 percent of cases.
• Type II: abnormal median IRP with 100 percent failed peristalsis and panesophageal pressurisation in 20 percent or more swallows. This is the most common subtype, seen in 50 to 70 percent of cases.
• Type III: abnormal median IRP with spastic contractions, with 20 percent or more swallows premature and no evidence of peristalsis. This is the least common subtype, seen in about 5 percent of cases.^[1][2]

A definition of achalasia requires 100 percent absent peristalsis, defined as all swallows either failed or premature.^[2] Type III is distinguished from distal oesophageal spasm by an abnormal IRP; opioids are associated with type III achalasia and patients should be studied off opioid medication if possible, because opioids inhibit neuronal excitability and reduce inhibitory neurotransmitters.^[2][5]

Inconclusive patterns (IRP at the upper limit of normal with 100 percent failed peristalsis) should be evaluated further with timed barium swallow and/or functional lumen imaging probe (FLIP). FLIP assesses oesophago-gastric junction opening and distensibility and can help in equivocal cases.

FLIP measures distensibility of the gastro-oesophageal junction and can be complementary in diagnosing achalasia and in post-treatment assessment. A reduced distensibility index with a reduced maximal diameter at the junction supports outflow obstruction.

The Eckardt score is the standard symptom score: four components (dysphagia, regurgitation, chest pain, weight loss), each scored 0 to 3, giving a total of 0 to 12. A value greater than 3 is considered a suboptimal (failed) outcome after treatment.^[1] It is a symptom score, not a disease stage, and is best combined with timed barium emptying or manometry.

Achalasia is chronic and incurable. All current treatments are palliative: they aim to reduce sphincter hypertonicity, relieve symptoms, improve emptying and prevent further dilatation.

The American College of Gastroenterology guideline grades pneumatic dilation, laparoscopic Heller myotomy and POEM as comparable effective therapies for type I or type II achalasia, and recommends POEM or extended myotomy for type III. Botulinum toxin is first-line only for those unfit for definitive therapy. Pneumatic dilation or Heller myotomy are both effective and equivalent short- and long-term in candidates.^[1]

Pharmacological therapy is the least effective option. Calcium channel blockers (nifedipine 10 to 30 mg sublingual before meals) and nitrates (sublingual isosorbide dinitrate 5 mg before meals) are the two most commonly used. Sildenafil 50 mg has also shown some efficacy.^[1] Overall, pharmacotherapy produces a short-term decrease of lower sphincter pressure in 13 to 65 percent of patients, with symptom improvement in 0 to 87 percent.^[1] Duration of action is short (30 to 120 minutes), so multiple daily dosing is needed, with side effects such as headache, hypotension and pedal oedema.

Other less commonly used agents include anticholinergics, beta-adrenergic agonists (terbutaline), theophylline and phosphodiesterase inhibitors.

The guideline recommends pharmacotherapy be used only for patients who are not candidates for definitive therapy and have failed botulinum toxin injection.^[1]

Botulinum toxin is a presynaptic inhibitor of acetylcholine release, cleaving SNAP-25 and blocking the unopposed cholinergic stimulation of the sphincter. It is delivered as 100 units above the squamocolumnar junction using a sclerotherapy needle in 0.5 to 1 mL aliquots. Escalating doses above 100 units have not shown superior benefit.^[1]

In a systematic review of 9 studies in 315 patients, symptom relief was seen in 78.7 percent within 30 days, declining to 70 percent at 3 months, 53.3 percent at 6 months and 40.6 percent at 12 months. Additional injections were needed in 46.6 percent, and 30 percent required further treatment (repeated injection, dilation or surgery).^[1]

It remains the best studied pharmacotherapy and the most effective pharmacological option, but its benefit is short-lived, so it should not be first-line in patients fit for myotomy. It is first-line for those unfit for definitive therapy. Previous toxin injection does not significantly affect performance and outcomes of myotomy.^[1]

Rare complications include reflux and mediastinitis. Repeated injection may make later myotomy more difficult.

Pneumatic dilation is the most effective non-surgical treatment. The standard dilators are 3.0, 3.5 and 4.0 cm, used in a graded fashion. The pressure required to obliterate the waist is usually 10 to 15 psi of air held for 15 to 60 seconds.^[1]

• Good to excellent symptom relief in 50 to 93 percent of patients after dilation.^[1]
• Cumulatively, 3.0 cm, 3.5 cm and 4.0 cm balloons give good to excellent relief in 74, 86 and 90 percent respectively, at a mean follow-up of 1.6 years (range 0.1 to 6 years).^[1]
• Initial dilation with the 3.0 cm balloon is recommended for most patients, followed by symptomatic and objective assessment in 4 to 6 weeks. In younger men (under 45 years), starting at 3.5 cm, or offering myotomy/POEM, may be more effective.^[1]
• Perforation is the most serious complication, with a median rate of 1.9 percent (range 0 to 16 percent) in experienced hands (over 100 treated patients). Every patient must be a surgical candidate in case of perforation.^[1]
• Gastro-oesophageal reflux may occur in 15 to 35 percent after dilation; proton pump inhibitors are indicated.^[1]

Predictors of favourable response include older age (over 45 years), female sex, a narrow (non-dilated) oesophagus and lower sphincter pressure under 10 mmHg after dilation.^[1] Routine gastrograffin swallow after dilation is not recommended; it is reserved for suspected perforation.^[1]

Serial dilation starting with 3.0 cm may not be effective in younger men with thicker sphincter musculature. In this group, 3.5 cm first, or myotomy/POEM, may be considered.^[1]

Surgical myotomy remains a definitive therapy. In 39 studies including 3086 patients, symptom improvement was achieved in a mean of 89 percent (range 77 to 100 percent) after laparoscopic myotomy.^[1] A meta-analysis of 1575 patients found success depended on subtype: 81, 92 and 71 percent for types I, II and III respectively.^[1]

Myotomy with fundoplication is superior to myotomy alone in controlling distal acid exposure: abnormal acid exposure in 47 percent without an anti-reflux procedure versus 9 percent with a posterior Dor fundoplication.^[1] Either Dor or Toupet fundoplication may be used; Toupet may be superior for dysphagia and length of stay in some meta-analyses.^[1]

Post-operative gastro-oesophageal reflux after myotomy alone occurs in about 29 to 31 percent (depending on approach), reduced to about 8 to 14 percent with fundoplication.^[1] Reflux after POEM is higher than after LHM with fundoplication (distal acid exposure 39.0 versus 16.8 percent).^[1]

Myotomy with a longer myotomy (or POEM) is favoured for type III achalasia.^[1]

POEM is a hybrid natural-orifice technique: a submucosal tunnel is created and the circular muscle cut for at least 6 cm into the oesophagus and 2 cm onto the cardia. Success (symptom improvement with no further treatment) in prospective cohorts has been greater than 90 percent.^[1] POEM is easier to tailor (longer myotomy) and is especially suited to type III achalasia, where extended myotomy matters.

Trade-offs: higher gastro-oesophageal reflux than LHM with fundoplication (39.0 versus 16.8 percent acid exposure), and the need for specialised expertise. As with dilation, routine post-POEM contrast study is not supported by evidence. Stent placement is recommended against for long-term dysphagia.^[1]

Because all definitive therapies disrupt the sphincter, reflux is common. After POEM, reflux esophagitis is frequent and may be high-grade even with mild or no symptoms, because patients with achalasia have limited oesophageal sensitivity to oesophagitis.^[5] Proton pump inhibitors are standard, and anti-reflux wrap at the time of LHM reduces this burden.^[1] Patients should be told that absence of heartburn does not exclude reflux after POEM.

• Aspiration from nocturnal regurgitation, causing cough, pneumonia.
• Megaesophagus and oesophageal food stasis.
• Perforation with pneumatic dilation (median 1.9 percent).^[1]
• Reflux oesophagitis/stricture after therapy.
• Oesophageal cancer (see below).

Targeted question in the post-treatment setting: the American College of Gastroenterology recommends using timed barium swallow as the first-line test when symptoms continue or return after definitive therapy, and suggests Eckardt score or manometry alone should not define treatment failure.^[1] It also suggests against routine endoscopic surveillance for oesophageal carcinoma in achalasia.^[1] Heller myotomy may be considered before esophagectomy in patients who have failed dilation and POEM if anatomy is conducive, and esophagectomy is recommended in surgically fit patients with megaesophagus who have failed other interventions.^[1]

Patients with achalasia have an increased risk of oesophageal cancer, mainly squamous cell carcinoma, with a reported incidence of 312 per 100,000 patient-years at risk; adenocarcinoma is 21 per 100,000 patient-years at risk.^[5] The risk progressively increases with follow-up time and is not clearly reduced by myotomy or dilation, because reflux after these procedures can induce metaplastic change.^[5] Patients with idiopathic or Chagasic achalasia should be under surveillance for oesophageal cancer; under a surveillance programme, early cancers amenable to endoscopic resection are found more often, and chromoendoscopy may improve accuracy.^[5] This contrasts with the ACG suggestion against routine surveillance^[1]; the evidence is observational and guidelines differ, so practice varies by centre. Intervals are not standardised in the sources reviewed and should follow local policy.

Any patient with suspected achalasia, especially with weight loss, should be referred for manometry and a specialist opinion. Type III achalasia, megaesophagus, failed therapy or pseudoachalasia always warrants specialist care.

Distal oesophageal spasm is a spastic disorder: recurrent chest pain and dysphagia from premature, simultaneous contractions of the distal oesophagus with normal lower sphincter relaxation. The commonest symptoms are dysphagia in about 55 percent and chest pain in about 29 percent; regurgitation, heartburn, weight loss, nausea and vomiting also occur.^[3]

Diagnosis: high-resolution manometry is the gold standard. Chicago version 4.0 defines it as a conclusive diagnosis when at least 20 percent of swallows are premature (distal latency under 4.5 seconds) with a normal median IRP.^[2][3] It differs from type III achalasia by normal sphincter relaxation (abnormal IRP in achalasia). Barium swallow may show retention and a corkscrew (rosary beads) configuration from tertiary, non-propulsive contractions.^[3]

Associations: gastro-oesophageal reflux disease (some patients improve with acid suppression), psychiatric conditions, and notably opioids (opioids inhibit inhibitory neurotransmitter release and can produce spasm). Distal spasm may represent a stage in the evolution to type III achalasia.^[3]

Treatment: pharmacological therapy is tried first, with limited efficacy. Proton pump inhibitors for reflux; nitrates and phosphodiesterase inhibitors (increasing nitric oxide availability), calcium channel blockers (inhibiting L-type channels and relaxing smooth muscle), and tricyclic antidepressants or SSRIs. Botulinum toxin reduces dysphagia score, stabilises unintentional weight loss and decreases sphincter pressure in spastic disorders, but efficacy is usually less than a year. Pneumatic dilation has minimal success. POEM appears effective (success rate greater than 80 percent) and safe in non-achalasia spastic disorders when performed by experienced endoscopists; surgical myotomy is an alternative when POEM is unavailable.^[3]

A hypercontractile disorder defined as 20 percent or more hypercontractile swallows (DCI greater than 8000 mmHg·s·cm) with a normal median IRP, and no achalasia or spasm. Symptoms are dysphagia and non-cardiac chest pain. It can only be diagnosed when achalasia and distal spasm are excluded and mechanical obstruction ruled out. Sphincter dysfunction may be present on FLIP even when IRP is normal, which may change management (targeted myotomy).^[2][3] Treatment is similar to spasm: acid suppression, smooth-muscle relaxants, botulinum toxin, POEM or surgical myotomy in refractory cases.

Ineffective (or hypomotile) motility: normal IRP with more than 70 percent ineffective swallows or at least 50 percent failed peristalsis; 50 to 70 percent ineffective swallows is inconclusive. An ineffective swallow is weak (DCI 100 to 449) or failed (DCI under 100), or a fragmented contraction. Patients often have reflux symptoms. Management is of the reflux and underlying cause; prokinetics help some.

Systemic sclerosis commonly involves the oesophagus: up to 90 percent of patients. Classic scleroderma oesophagus is absent or ineffective peristalsis of the distal oesophagus with a hypotensive lower sphincter, found in as many as 55 percent; manometric abnormalities occur in up to 75 to 80 percent, with hypotensive sphincter in more than 50 percent and body dysmotility in more than 60 percent.^[4]

Mechanism: smooth muscle atrophy and fibrosis in distal oesophagus and sphincter, opposite to achalasia (hypotensive sphincter rather than non-relaxing). Consequences: severe reflux, dysphagia, Barrett's risk, peptic stricture.

Treatment: proton pump inhibitors are standard of care for reflux; an estimated 40 percent of patients show no response to a standard dose, so a two- to fourfold increase is common practice.^[4] Prokinetics (metoclopramide, erythromycin, and others) and buspirone 10 mg (lower sphincter pressure increased in up to 80 percent of patients) are used.^[4] Anti-reflux surgery is generally suboptimal because of profound dysmotility, with 38 to 71 percent developing postoperative dysphagia after fundoplication; Roux-en-Y gastric bypass is an alternative with better reflux-related quality of life and less dysphagia.^[4] Empirically treat reflux and avoid large meals; specific low-resource advice below.

A manometric diagnosis of EGJ outflow obstruction requires abnormal IRP in both primary and secondary positions plus elevated intrabolus pressure, with evidence of peristalsis (not meeting achalasia criteria), plus supportive testing. Clinically relevant EGJOO may represent an achalasia variant or mechanical/functional factors; opioids and artifactual IRP rises are common. It is always considered clinically inconclusive without supportive testing.^[2]

| --- | --- | --- | --- |

• Pregnancy: manometry and endoscopy can be done when needed; definitive therapy is usually deferred unless severe. Individual specialist management.
• Children: achalasia occurs but is uncommon; paediatric surgical expertise is required. Chagas may coexist in endemic areas.
• Older adults: pseudoachalasia must always be excluded; severe weight loss is a red flag.
• Systemic sclerosis: manage reflux aggressively; surgery carries high dysphagia risk.

• Achalasia can be suspected clinically (progressive dysphagia to solids and liquids, nocturnal regurgitation, weight loss) and on a plain barium swallow, which shows bird-beak narrowing and retention. Timed barium swallow needs only barium and X-ray.
• High-resolution manometry may be unavailable; a barium swallow plus careful endoscopy still secures the diagnosis in most.
• Pneumatic dilation can be performed in centres with fluoroscopy/scopy and surgical backup; without this, refer. Botulinum toxin requires endoscopy but not surgery; tablets are a fallback for the unfit.
• In Chagas-endemic Latin America, chagasic achalasia is a major cause. Consider serology, ask about origin, and look for cardiomyopathy and megacolon. Treatment is the same (palliative LES disruption), although sphincter pressure is lower and both nerves are damaged.^[6]
• For distal spasm and scleroderma: cheap first steps are proton pump inhibitors, nitrates or calcium channel blockers, and behavioural measures; POEM/myotomy only where expertise exists.

• Achalasia is an incurable motility disorder from loss of inhibitory myenteric neurons: the lower sphincter does not relax and peristalsis is absent or spastic. Food accumulates and the oesophagus dilates.
• Most cases are primary (idiopathic); secondary causes are Chagas disease (both nerves damaged, lower pressure) and pseudoachalasia (cancer; shorter history, older age, severe weight loss).
• Presentation: progressive dysphagia to solids and liquids, nocturnal regurgitation, chest pain, heartburn (27 to 42 percent), weight loss. Examination often normal; red flags for cancer.
• Endoscopy first (excludes pseudoachalasia), then barium swallow (bird beak, retention; timed column at 1, 2, 5 minutes), then high-resolution manometry (gold standard).
• Manometry values (Medtronic): IRP under 15 mmHg supine / under 12 mmHg upright; DCI 450 to 8000; panesophageal pressurisation 30 or more; premature contraction distal latency under 4.5 seconds at DCI at least 450.
• Chicago v4.0 subtypes: Type I (20 to 40 percent), Type II (50 to 70 percent), Type III (about 5 percent); 100 percent absent peristalsis defines achalasia.
• Eckardt score (0 to 12) greater than 3 means treatment failure; combined with timed barium emptying or manometry.
• Definitive therapy knocks out the sphincter: pneumatic dilation (graded 3.0, 3.5, 4.0 cm; 10 to 15 psi for 15 to 60 seconds; 50 to 93 percent relief; 1.9 percent perforation median), laparoscopic Heller myotomy (mean 89 percent improvement; with fundoplication reflux falls from 47 to 9 percent), or POEM (greater than 90 percent). Type III favours POEM or extended myotomy.
• Botulinum toxin 100 units gives 78.7 percent relief at 30 days, falling to 40.6 percent at 12 months; first-line only for the unfit. Nifedipine 10 to 30 mg or isosorbide dinitrate 5 mg sublingual before meals, sildenafil 50 mg are fallbacks (13 to 65 percent pressure fall; 0 to 87 percent symptom improvement).
• Post-treatment reflux is common, especially after POEM (39.0 versus 16.8 percent acid exposure); treated with proton pump inhibitors; no heartburn does not mean no reflux.
• Cancer risk: squamous cell carcinoma 312 per 100,000 patient-years; adenocarcinoma 21 per 100,000 patient-years. Guidelines differ on routine surveillance; risk rises with time and is not clearly reduced by therapy.
• Distal spasm: at least 20 percent premature contractions, normal IRP; dysphagia 55 percent, chest pain 29 percent; corkscrew barium; POEM success greater than 80 percent.
• Hypercontractile oesophagus: at least 20 percent swallows with DCI over 8000.
• Ineffective motility: more than 70 percent ineffective or at least 50 percent failed swallows.
• Scleroderma: up to 90 percent oesophageal involvement; hypotensive sphincter and absent distal peristalsis; proton pump inhibitors standard; 40 percent need higher doses; surgery risky.
• Use original, open-access sources; numbers above come from ACG 2020 and Chicago v4.0 2021.

Gastro-oesophageal reflux disease; eosinophilic oesophagitis; systemic sclerosis; Chagas disease; oesophageal carcinoma; normal swallowing physiology.