The management of achalasia and other motility disorders of the oesophagus

Pathophysiology

Achalasia results from the loss of myenteric neurons at the lower oesophageal sphincter (LOS) and distal oesophagus that leads to failure of relaxation of the LOS and ineffective oesophageal peristalsis. The exact aetiology of the loss of myenteric plexus is unknown, but autoimmune dysfunction after exposure to viral infections such as herpes simplex, human papillomavirus, and measles are postulated. In Chicago type 1 or 2 achalasia the mesenteric ganglia are replaced with fibrosis, but in type 3 achalasia the mesenteric ganglia are infiltrated with chronic inflammatory cells such as lymphocytes. This may account for the spastic contraction and chest pain that patients experience in type 3 achalasia. A large-scale genetic association study revealed significant abnormality at the major histocompatibility (MHC) region on chromosome 6; its protein products form the receptors of antigen-presenting cells. The findings imply that immune-mediated processes are involved in the pathophysiology of achalasia.

While most cases of achalasia are idiopathic, the disappearance of the myenteric plexus can occasionally be due to malignant infiltration, which is called pseudoachalasia, or due to Trypanosoma infection in Chagas disease. Pseudoachalasia is an important cause of secondary achalasia, especially in the elderly. It accounts for 2–4% of patients with suspected achalasia. It behaves like achalasia, with dilation of the proximal oesophagus and narrowing at the LOS. It is caused by submucosal infiltration of neoplastic cells or autoimmune damage from a reaction to tumour cells at the LOS, and the findings on barium oesophagogram and manometry might be similar to true achalasia. In a recent systemic review, the mean age of patients with pseudoachalasia was 60 years and the most common cause was gastric cancer, followed by oesophageal cancer and small-cell lung cancer. Many of the patients were mistakenly treated as having achalasia. Repeat endoscopy, computed tomography (CT) scan, and endoscopic ultrasound were found to be useful in the diagnosis of pseudoachalasia. A high index of clinical suspicion and correct interpretation of investigations is important to exclude this serious condition.

Clinical features

Dysphagia and regurgitation are the cardinal symptoms of achalasia, and these symptoms tend to be chronic. Many patients could be misdiagnosed as having gastro-oesophageal reflux disease (GORD) due to the presenting symptoms. Other symptoms include weight loss and chest pain. For patients with type 3 (or spastic) achalasia, chest pain is the predominant symptom. The Eckardt score is a composite symptom score that includes dysphagia, regurgitation, chest pain, and weight loss. This is commonly used for achalasia to grade the severity of disease and quantify treatment outcomes. As highlighted earlier, it is important to exclude pseudoachalasia before embarking on treatment.

Investigations

Upper endoscopy is usually the first diagnostic test for achalasia, given the presenting symptoms. It is used to exclude oesophageal or gastric neoplasm. In achalasia, the proximal oesophagus may appear dilated with food or saliva retention and occasionally, candidiasis is identified. Abnormal oesophageal body contractions can be seen, especially for type 3 achalasia. The LOS will be tight and there is often difficulty passing the standard endoscope through. However, if a patient has been previously treated, there might be minimal resistance encountered.

A barium swallow study may show hold-up of the contrast, with a tapering stricture in the distal oesophagus often described as a ‘bird’s beak’ ( Fig. 14.1 ). The oesophagus is dilated proximally. However, the findings of a barium study are non-specific and additional tests are required to confirm the diagnosis. Recently, a timed barium swallow (or timed oesophagogram) was described in which the height of barium was measured 5 minutes after the ingestion of barium. It is used to assess the emptying of the oesophagus and can also be adopted as a simple objective method to monitor treatment response.

Manometry and high-resolution manometry (HRM)

Manometry is recommended to confirm the diagnosis of achalasia ( Fig. 14.2 ). In conventional manometry, the cardinal features are a hypertensive non-relaxing LOS and the absence of oesophageal peristalsis. More recently, HRM is increasingly being used for diagnosis. In HRM, catheters with 36 or more sensors are placed 1 cm apart along the oesophagus, which allow a much more detailed pressure recording from the pharynx to the stomach.

HRM is more sensitive than conventional manometry to diagnose motility disorders and is regarded as the gold standard for the diagnosis of achalasia. The use of HRM has also led to the subclassification of achalasia based on the pattern of contractility in the oesophageal body, which forms the basis for the Chicago classification ( Fig. 14.3 ).

Integrated relaxation pressure (IRP) is the mean post-swallow LOS pressure of a 4-second period. Achalasia is typically diagnosed when IRP is higher than the upper limit of normal. It is subclassified as type 1 when there is complete loss of contractility of the oesophageal body with no evidence of pressurisation, type 2 when there is pressurisation or compression in the distal oesophagus over 30 mmHg, and type 3 when there are two or more premature spastic contractions in the oesophageal body.

Treatment modalities

There are many treatment options available for achalasia. However, these options are non-curative in nature as they are unable to restore neuromuscular function, including normal peristalsis. Most treatments target the LOS by lowering its resting pressure, and the goal of treatment is symptom control and quality of life improvement. The management of patients’ expectations is an important aspect of counselling for treatment.