Achalasia is primarily a disorder of motility of the lower oesophageal or cardiac sphincter. The smooth muscle layer of the oesophagus has impaired peristalsis and failure of the sphincter to relax causes a functional stenosis or functional oesophageal stricture. Most cases have no known underlying cause but a small proportion occurs secondary to other conditions - eg, oesophageal cancer.
- The tone and the activity of the muscle are controlled by a balance of excitatory transmitters such as acetylcholine and substance P and inhibitory transmitters such as nitric oxide and vasoactive intestinal peptide (VIP).
- The local obstruction with proximal dilatation is similar to Hirschsprung's disease and, in most cases, there is an aganglionic segment as in Hirschprung's disease but it is apparently acquired rather than congenital and so presents much later.
- The interstitial cells of Cajal (cells found within the intestinal wall which seem to provide a 'pacemaker' function for the intestinal musculature) are thought to play a role.
- Autoimmune reaction to viral infections and genetic factors have also been implicated.
- Achalasia tends to present in adult life. A Canadian study reported a mean age at diagnosis of 53.1 years. The same study reported an annual incidence of 1.63/100,000.
- Achalasia in children is rare but the incidence is rising. A UK study reported an annual incidence of 0.18/100,000.
- The most common presenting feature is dysphagia. This affects solids more than soft food or liquids.
- Food bolus impaction.
- Regurgitation may occur in 80-90% and some patients learn to induce it to relieve pain.
- Chest pain occurs in 25-50%. It occurs after eating and is described as retrosternal. It is more prevalent in early disease.
- Heartburn is common and may be aggravated by treatment.
- Loss of weight suggests malignancy (may co-exist).
- Nocturnal cough and even inhalation of refluxed contents is a feature of later disease.
- Examination is unlikely to be revealing although loss of weight may be noted. Rarely, there may be signs of an inhalation pneumonia.
- This may possibly show signs of inhalation.
- The classical picture of a CXR in achalasia shows a vastly dilated oesophagus behind the heart; however, this is rarely seen in practice.
- The gastric air bubble may be small or absent.
- This usually precedes endoscopy when investigating dysphagia, as it is very easy to perforate a malignancy with an endoscope.
- The barium swallow in achalasia is characteristic. The oesophagus is dilated and contrast material passes slowly into the stomach as the sphincter opens intermittently. The distal oesophagus has a narrow segment and the image resembles a bird's beak. This is in contrast to the rat's tail appearance of carcinoma of the oesophagus. In the early stages, radiology can be normal.
- The technique can be enhanced by having patients drink tap water during visualisation of the lower oesophagus in an attempt to clear the standing barium column.
- Having ruled out obvious malignancy with a barium swallow, many specialists proceed to endoscopy, which can detect approximately a third of achalasia cases, although some still prefer to perform manometry at this stage (see below).
Manometry of the oesophagus
- Manometry is the gold standard for diagnosis of achalasia and can detect up to 90% of cases.
- It may show diagnostic features; there is a high resting pressure in the cardiac sphincter, incomplete relaxation on swallowing and absent peristalsis.
- If manometry is normal but clinical symptoms or radiological evidence suggest achalasia, a condition called pseudoachalasia may be present. Causes include oesophageal and gastric malignancies and other tumours involving the distal oesophagus. Endoscopic biopsy remains the most helpful diagnostic tool.
Lower oesophageal pH monitoring
- This may also be required to exclude gastro-oesophageal reflux disease (GORD) which often occurs with achalasia. If present it should mitigate against treatment by pneumatic dilatation (which causes about a 30% incidence of GORD).
- Other causes of dysphagia, including:
- A rare form may present in children. The Rozycki syndrome is deafness associated with short stature, vitiligo, muscle wasting and achalasia. Allgrove's syndrome is familial dysautonomia, glucocorticoid insufficiency and defective tear formation.
- A condition rather like achalasia can develop as a complication of American trypanosomiasis (Chagas' disease). There is no aganglionic segment in this or in achalasia associated with diabetes and certain malignancies.
- Calcium-channel blockers and nitrates may reduce pressure in the lower oesophageal sphincter but they are effective in only about 10% of patients and tend to be reserved for those who are unable to tolerate other forms of treatment.
- Although there are no international guidelines, the Heller myotomy is generally considered the best treatment for those who are fit. Considering the usual age of presentation, that should be most patients. The operation can be performed via the laparoscope. The muscle fibres of the lower oesophagus are divided in a longitudinal direction for about 5 cm, about 1.5 cm above the stomach. The success rate is 85-95% and there is a low complication rate.
- Pneumatic dilatation is the preferred option for older unfit patients. A balloon is inserted into the lower oesophagus via an endoscope and it is inflated to rupture the muscle of the oesophagus whilst leaving the mucosa intact. The success rate is 40-85% with a 0-10% rate of perforation. If a perforation occurs, emergency surgery is needed to close the perforation and perform a myotomy. Multiple balloon dilatation with increasing balloon diameter at two months, two years and six years is more effective.
- Endoscopic injection of botulinum toxin into the lower oesophageal sphincter is effective in 85% of cases but the benefits reduce over time: only 30% remain improved at two years. The technique is best reserved for the elderly and infirm who cannot tolerate dilatation or surgery.
- Peroral endoscopic myotomy and endoscopic stent insertion are techniques being explored.
- Operative failure may be met by repeat operation, dilatation or, in extreme circumstances, oesophagectomy.
- Untreated achalasia may lead to nocturnal inhalation of material lodged in the oesophagus and aspiration pneumonia.
- Treatment may cause perforation of the oesophagus.
- Treatment may lead to GORD.
- Oesophageal cancer:
- In a prospective study of 448 achalasia patients, 3.3% developed oesophageal cancer. Two thirds were men.
- Long-standing disease increases the risk.
- Presumably potential carcinogens are held in the oesophagus instead of being moved along.
- Malignancy can develop even after treatment.
- Endoscopic surveillance is controversial but might be worthwhile in patients with long-standing achalasia.
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