Oesophageal manometry: an overview.SJ Bhatia
Dept. of Gastroenterology, KEM Hospital, Bombay, Maharashtra.
Keywords: Esophagus, physiology,Human, Manometry,
The osesophagus is a hollow tube, which transports food from the mouth to the stomach. Anatomically, it is a simple tube, with sphincters at both ends. The sphincters funption to keep the tube empty from external (food) as well as internal (acid) intrusions. Swallowing and transport of food from the mouth to the stomach en route the oesophagus is a highly coordinated neuromuscular event. In the normal course of events, this function is practically taken for granted. In addition to motor activity, the oesophagus reacts to chemical agents and pressure changes. It is only in disease states that the physician is perplexed about the complexity of the functions of the oesophagus and its sphincters.
Oesophageal disorders usually present with heartburn and dysphagia, and occasionally with chest pain, nocturnal cough and dyspnoea. From the history alone, except in cases of classical gastro-oesophageal reflux (GOR) disease, it is difficult to judge the cause of symptoms. It is therefore mandatory to rule out a structural lesion in the oesophagus or stomach by barium studies or endoscopy, prior to performing a function test. In patients with chest pain, a prior cardiac workup to rule out ischaemic heart disease is essential.
Barium studies assess the emptying of the oesophagus as well as structural abnormality. Esophageal motility is best assessed by the full column technique and fluoroscopic observation. When combined with videofluoroscopy, radiology is a useful complement to manometry, especially for the pharyngo-oesophageal segment.
Endoscopy has the advantage of direct visualisation of structural lesions and biopsies can be obtained simultaneously. However, endoscopy does not play a role in the diagnosis of a motility disorder. Manometry is the best method available to diagnose motor disorders of the oesophagus.
Oesophageal function tests are designed to assess motor and sensory functions [Table - 1]
Primitive manometric studies were done about a century ago. Techniques of recording pressures improved only in the late 1960s, and accurate measurements were made possible with the development of the low-compliance perfusion system,. About two decades ago, Dr LD Harris wrote 'Many papers describing the clinical application of esophageal manometry have appeared, but so little has been added to our understanding of either esophageal physiology or disease that 1 still wonder whether esophageal manometry is ready for widespread clinical application. The situation changed over the next few years and manometry became a tool for clinical evaluation of patients with motor disorders of the oesophagus. As precision of measurements increased, manometry gained ground as a clinical tool. Today manometry and pH testing are important weapons in the armamentarium of investigative tools especially in patients with non-cardiac chest pain and dysphagia.
Station manometry consists of evaluating the oesophagus at rest and in response to water or food swallows. Ambulatory manometry, usually combined with pH monitoring, evaluates the oesophagus over a period of 24 hours.
Manometry systems are of two main types: water perfusion type (external transducer) or those with built in transducers (solid state) connected to a recording device. The solid state catheters have the advantage that water perfusion is not continuously required and the patient can therefore shift position or be ambulatory. Data are recorded on a chart recorder or computer. With dedicated software of many types available, the physician's job of analysis of the recordings is made easy.
In the normal state, the oesophageal sphincters have an increased resting pressure, and relax in response to a swallow. In contrast, the oesophageal body lumen pressure is negative (as compared to gastric pressure) at rest. After a swallow, a wave of peristalsis follows the bolus head.
The lower (LOS) and upper (UOS) oesophageal sphincters are studied to assess the basal pressure and response to swallowing. After a swallow is initiated, the lower and upper sphincters relax within 2 mmHg of the gastric and oesophageal baseline respectively. The LOS length, intraabdominal portion and vector volume can also be studied. The oesophageal body is studied with the recording ports at various levels 5 cm apart (usually 5, 10, 15 cm or 3, 8, 13 cm above the LOS).
Manometry assesses the strength and duration of contractions, and coordination between them. It is recommended that every laboratory have standard values depending on the normal population. However, with technique being standardised, interinstitutional data are becoming comparable. The accepted normal values based on a study of 95 volunteers are listed in [Table - 2]. For the UOS, normal values in the supine position are: UOS basal pressure 82 + 12 mmHg and residual pressure is -2 + 1 mmHg (as compared to oesophageal pressure).
Oesophageal manometry is indicated [Table - 3] when a motility disorder is suspected as a cause for symptoms.
A variety of motor disorders have been described normal. It provides the opportunity to test patients when especially in non-cardiac chest pain. Criteria for diagnosis of various motility disorders have been evaluated. swallows in a physiological setting, including meal times The recommended manometric criteria, [Table - 4] have remained almost unchanged over the last few years. However, there is confusion as to whether these abnormalities (except achalasia) are distinct entities, variants of diffuse oesopha eal spasm (DOS), or curious manometric findings. Investigators who 'split' these disorders into groups had hoped that further definition would lead to a better diagnostic and therapeutic approach. However, this has not been the case. The intermittent nature of these findings further compounds the problem.
Even if a classic motor pattern is detected on manometry, this is insufficient evidence on which to base the diagnosis, except in achalasia. Most manometric findings of spastic oesophageal disease can be found with GOR. Cohen suggested general criteria to define a manometric finding as an important oesophageal disease. The motility event must be a major alteration of oesophageal physiology; the motility change must be associated temporally with symptoms; abnormal oesophageal function must be shown by other independent measurements; and symptoms or signs of abnormality must be improved as the disorder is corrected. The only disorder, which fulfills all these criteria is achalasia cardia.
In patients who present with dysphagia, conventional station manometry may be normal in upto 36% of cases. Provocation by food swallows may detect a motility disorder in about half of these cases. Food ingestion often magnifies the motor disorders seen during water swallows. In patients who have dysphagia to a particular consistency of food, challenge with the same kind of food is required.
Ambulatory manometry is an important investigation in patients where station manometry is normal. It provides the opportunity to test patients when they have the symptoms. Also it evalutates about 1000 swallows in a physiological setting, including meal times and sleep.
This is the only definitive test for GOR due to acid. It has been accepted as the gold standard for the diagnosis of GOR. Alkaline (bile) Feflux can be suspected if the oesophageal pH rises > 7 with a simultaneous rise in intragastric pH. The pH electrode, either glass or antimony, is placed in the oesophagus, and connected to a data-logger. The recording probe is traditionally placed 5 cm above the lower oesophageal sphincter (LOS) and kept in place for 12-24 hours, while the subject continues 'normal activity'. As with manometry, normal standards have to be established individually by each laboratory.
Indications for performing the procedure include: suspected GOR with normal endoscopy; atypical symptoms; non-responsive GOR; and pre-operative cases.
If manometry is to be done, who is to do it? This important question was raised and answered by Pope in 1978. According to him, oesophageal motility tests should be both performed and interpreted by the same well-trained physician who has a personal clinical interest. If no dedicated individual is available or interested, then manometry should not be added just to keep up to date.
[Table - 1], [Table - 2], [Table - 3], [Table - 4]