the oesophagus and its disorders Flashcards
describe the structure of the oesophagus
- Fibromuscular tube (25cm) of striated squamous epithelium
- Lies posterior to the trachea
- Begins at end of laryngopharynx and joins the stomach a few cm from diaphragm (at the cardiac orifice of the stomach)
what is the function of the oesophagus ?
- transports food to the stomach and secretes mucus in order to do this
- Conveys food and fluids from pharynx to stomach
- Presence of food in the mouth triggers the swallowing
- Afferent impulses in the glossopharyngeal- vagal reflex
- Integration of impulses in the nucleus of tractus solitarius (NTS), nucleus ambiguus (NA) and dorsal vagal nucleus
- Efferent impulses/motor pathways pass to the pharyngeal musculature, tongue, oesophagus and LOS
what promotes the transport of ingested food into the stomach ?
- This is a highly coordinated muscular process - involves contraction and relaxation of the oesophagus which transports the food through the length of the GI Tract
- Relaxation of the sphincters (UOS and LOS)
what type of muscles does the oesophagus comprise of ?
- Skeletal muscles surround the oesophagus below the pharynx (the upper third)
- Smooth muscles surround the lower two thirds
describe the 2 sphincters of the oesophagus
Upper oesophageal sphincter (UOS): striated muscle;
* Musculo-cartilaginous structure
* Constricted to avoid air entering the oesophagus
Lower oesophageal sphincter (LOS): smooth muscle; acts as a flap valve
* LOS = area of high pressure zone
* LOS has intrinsic and extrinsic components
* Intrinsic components of LOS: oesophageal muscles; under neurohormonal influence
* Extrinsic components of LOS: diaphragm muscle (adjunctive external sphincter)
describe the components of the lower oesophagus sphincter
Intrinsic components of LOS:
* Thick circular smooth muscle layers and longitudinal muscles
* Clasp-like semi-circular smooth muscle fibres on the right side
* Myogenic activity (some resting tone initiated by cells within), but less ACh-responsive
* Sling-like oblique gastric (angle of His) muscle fibres on the left side
* Work in concert with the clasp like-semicircular smooth muscle fibres, help to prevent regurgitation- responsive to cholinergic innervation
* Angle of His is poorly developed in infants for it makes a vertical junction with stomach, hence why reflux is common in infants
Extrinsic components of LOS:
* Crural diaphragm encircles the LOS
Forms channel through which oesophagus enters the abdomen
* Fibres of the crural portion of the diaphragm possess a “pinchcock-like” action (extrinsic sphincter; diaphragmatic sphincter)- myogenic tone
how is the oesophagus innervated ?
- Upper part: striated muscle; supplied by somatic motor neurons of vagus nerve without interruption
Vagus nerve - Splanchnic nerves (thoracic sympathetic trunks)
- Lower part: smooth muscles;
- Innervated by visceral motor neurons of vagus nerve with interruptions (-synapse with postganglionic neurons; cell bodies in oesophagus and splanchnic plexus)
describe neural control of the sphincters
- Acetylcholine, SP: contract the intrinsic sphincters
Gastrin contracts the intrinsic sphincters - NO and VIP: relax the intrinsic sphincters
how is swallowing initiated ?
- Voluntary action – collect material on tongue and push it backwards into pharynx (skeletal muscle, mucus membrane)
- Waves of involuntary contractions push the material into oesophagus
- Food moves from Mouth→oropharynx →laryngopharynx→oesophagus and stomach
Reflex responses:
* Inhibition of respiration (breathing)- nasopharynx is closed off
* Closure of glottis (around the vocal cords) by epiglottis
* Prevents food from entering the trachea
* Ring of peristaltic waves (4cm/sec) behind the food mass moves it towards the stomach
* A second wave of peristalsis moves any food remnants along the oesophagus
describe secondary peristalsis
- Upon the relaxation of upper oesophageal sphincter (UOS), food passes
- UOS closes as soon as food passes
- Glottis opens
- Breathing resumes
- LOS closes after the food mass has passed
- Large food material does not often reach the stomach after the first peristaltic wave
- Distension of the lumen of the oesophagus by food remnants stimulates the receptors → repeated waves of peristalsis (secondary peristalsis)
- Secondary peristalsis ensures that ingested food reaches the stomach
what prevents the reflux of gastric contents ?
- there is an anti-reflux barrier in the region of gastro-oesophageal junction
- LOS – closes after the “material”/food mass has passed
- “Pinchcock” effect of the diaphragmatic sphincter on the lower oesophagus (side-to-side compression between “2 pillars” of the crus)
- Plug-like action of the mucosal folds in the cardia– occludes the lumen of the gastro-oesophageal junction:
- Abdominal pressure acting on the intra-abdominal parts of the oesophagus
- Valve-like effect of oblique entry of oesophagus into stomach – in adults only
- Sphincter muscles of UOS and LOS = strong circular muscles
- Act as valves; and the law of the gut promotes and controls the movement of the food mass aborally (movement towards the anus)
- Prevent reflux by (forming an opening when relaxed and) closing completely when contracted
what are the types of oesophageal diseases ?
Oropharyngeal dysphagia/aphagia- swallowing difficulty is caused by the inability of the UOS to open or discoordination of the timing between the opening of UOS and the pharyngeal push behind the ingested mass of food
Oesophageal spasm- abnormal oesophageal contractions and food is not reaching the stomach effectively
Diffuse oesophageal spasm- chest pain coming from oesophagus (angina-like pain)
Achalasia- disorders of motility or peristalsis of oesophagus (assess the motor function of the UOS, LOS and oesophageal body)
Regurgitation- reflux of stomach acids into oesophagus; weak LOS (GORD); assess causes of regurgitation
describe the pathophysiology of achalasia
- 1/100,000; presents at any age
Findings may vary: - Impaired LOS relaxation (spasms) -
Can be accompanied by impaired peristalsis (sphincter spasms); - Food and liquids fail to reach the stomach – delayed opening of LOS;
- Results in dilation of oesophageal body with distal narrowing (bird’s beak appearance) of the barium-filled oesophagus on oesophagram;
- Long period of sporadic dysphagia (difficulty swallowing);
- Regurgitation of food
describe the aetiology of achalasia
- Disorders of motility or peristalsis of oesophagus (assess the motor function of the UOS, oesophageal body and LOS)
- Damage to the innervation of oesophagus
- Degenerative lesions to the vagus nerve and loss of myenteric plexus ganglionic cells in the oesophagus
Initiating factor unknown, but thought to be autoimmune or triggered by infection
what are the symptoms of achalasia ?
- Dysphagia
Difficult or painful swallowing - Vomiting/regurgitation
- Heartburn
Retrosternal burning sensation due to oesophageal dysmotility
Retention of ingested (acidic) food;
Generation of lactic acid in the process of decomposition of retained food;
also heartburn could be caused by the retention of small quantities of gastric acid refluxed in the oesophagus due to poor emptying and incomplete relaxation of LOS
how is achalasia diagnosed ?
- Examine/take patient history and evaluate any swallowing disorders
- The patient’s self-report may suggest the type of disorder responsible for the complaints which may trigger tests required to determine, or verify the specific cause of the complaint
- The elderly: Some abnormalities of swallowing may be frequent in the elderly
- Barium radiography (barium swallow): dilatation of oesophagus with beak deformity at lower end
-Evaluates the entire swallowing channel (mouth, pharynx, and oesophagus) - Oesophageal manometry: absent peristalsis
why do we do oesophageal manometry ?
Oesophageal manometry is performed for the following reasons:
* To determine the cause of non-cardiac chest pain
* To evaluate the cause of reflux (regurgitation) of stomach acid and other contents back up into the oesophagus (GORD?)
* To determine the cause of difficulty of swallowing food (does UOS/LOS contract and relax properly?)
Allows evaluation of strength of coordination of muscle contractions
* Relaxation function of LOS
* Overall, test evaluates if the oesophagus is contracting and relaxing properly
Interpretation of results:
Pressure of LOS <26mm Hg is normal; >100 mm Hg is considered achalasia; > 200 mm Hg is nut cracker achalasia
Low LOS pressure suggests GORD, but GORD can occur in individuals with normal LOS pressure
what do the results of manometry mean ?
Normal results of oesophageal manometry would show:
* Normal LOS pressure and normal muscle contractions upon swallowing
* The muscle contractions follow a normal pattern down the oesophagus
* Normal pressure of the LOS is about 15 mmHg, but
- When the LOS relaxes to let food pass into the stomach, the pressure is less than 10 mmHg
- But in the absence of letting food mass pass through the LOS into the stomach and the LOS pressure is less than 10 mmHg, GORD can be suspected
Abnormal results show/are characterised by:
* Presence of muscle spasms in the oesophageal body
* Presence of weak contractions along the length of the oesophagus
- Achalasia is characterised by high LOS pressure, the LOS fails to relax after swallowing
- Lack of a coordinated LOS relaxation in response to swallowing.
describe reflux in normal individuals
- Reflux is often brief, relatively infrequent;
- Often occurs after meals in normal individuals (- due to transient spontaneous LOS relaxation, tsr);
- Reflux usually stimulates salivation
- Saliva is an effective natural antacid - dilutes and neutralises refluxed gastric acid
BUT
Low rate of salivation; lack of ability to swallow own saliva →prolongation of contact of refluxed material with oesophagus → GORD
what is gastro-oesophageal reflux disease (GORD) ?
- GORD is the backwards movement of gastric content into oesophagus, due to prolonged relaxation of the LOS
- GORD is when reflux is more frequent and troublesome
- GORD causes oesophageal irritation and oesophageal damage
- Chronic oesophagitis (erosive or non-erosive) – 30% prevalence
- GORD causes a burning sensation in the chest (angina-like pains), in some cases after meals
Symptoms:
Heartburn – retrosternal pain (angina-like pains)
Coughs (reflux irritates the larynx); poor sleep due to waking up at night
Belching
Regurgitation
Dysphagia
What are the causes of reflux in patients with GORD ?
- Transient spontaneous LOS relaxation (tsr)
- Resting LOS pressure is too weak to resist the pressure within the stomach
- Sudden (& sustained) relaxation of the LOS that is not induced by swallowing
what factors contribute to the severity of GORD ?
- Weak or uncoordinated oesophageal contractions/poor oesophageal motor activity - poor oesophageal peristalsis →↓ clearance of gastric acid
- Prolonged duration of contact of refluxed digestive contents with oesophagus
- Length of time the oesophagus is exposed to gastric acid
- Impaired gastric emptying alone can cause severe GORD
- ↑ Gastric acid secretion coupled with presence of bile in gastric contents → severe oesophageal damage
- Amount of pressure placed on the anti-reflux barrier and less functional LOS or resting LOS tone is low or absent
- LOS tone fails to increase when lying flat or during pregnancy
Some foods; lying down (supine) after eating – heavy meal
Some drugs
Pregnancy or obesity
how is GORD investigated ?
- Low dose proton pump inhibitor (PPI) challenge
- Upper GI endoscopy
- Manometry
- 24-hr ambulatory pH monitoring
Findings from continuous pH monitoring:
24 hr hour pH monitoring shows that most normal
individuals (non-refluxers) reflux on a daily basis
Therefore, GORD implies not just the presence of
reflux, but reflux in excess of that experienced by
non-refluxers
how can pregnancy lead to GORD ?
- Last trimester of pregnancy is associated with increased abdominal pressure which forces gastric contents into oesophagus
- Foetus increases pressure on abdominal contents
Pushes terminal segments of oesophagus into thoracic cavity - Heartburn subsides in the last months of pregnancy as uterus descends into pelvis
how is GORD managed in patients ?
- Life-style changes - raise head of bed at night, weight loss, modify food
- ↓ Intake of foods and drink which cause symptoms
- Anti-reflux surgery (fundoplication – wrap fundus around LOS)
- Caution: Fundoplication can cause dysphagia as it reduces the distensibility of LOS
- Antacids
- H2 receptor antagonists and proton pump inhibitors
Metoclopramide/domperidone – may enhance peristalsis and help gastric acid clearance - Some people need to avoid large meals
- Lose weight (if overweight)
- Avoid foods that increase gastric acidity
- Avoid foods that slow gastric emptying (decease fat intake
- Avoid lying down after meals - elevate the head of the bed
- Avoid some drugs and smoking
describe the use of antacids to treat GORD
- Neutralise gastric acid; ↑ pH of gastric lumen
Inhibit peptic activity and stop acid secretion
But - Magnesium salts→ diarrhoea
- Aluminium salts→ constipation
- Use a mixture of 2 to ensure bowel function
- Combine alginates (e.g. gaviscon) with antacids for oesophageal reflux
- Alginic acid + saliva form a raft which floats on content of gastric lumen and protects the oesophageal mucosa from reflux
- All of the above agents ↓ acid secretion and help heal the ulcer, but removal of H. pylori is essential to stop ulcer returning.
what are the complications of GORD ?
- Oesophagus has squamous mucosa
- Acid reflux → desquamation of oesophageal cells (injury of squamous mucosa)
- ↑ cell loss → basal cell hyperplasia
- Excessive desquamation → ulceration
- Ulcers may haemorrhage, perforate or heal by fibrosis with strictures
- This leads to Barrett’s oesophagus and oesophageal cancer
what are the long term effects of GORD ?
- Oesophagitis, oesophageal strictures
- Squamous cell carcinoma
- Barrett’s syndrome - this may predispose someone to oesophageal adenocarcinoma
- Oesophageal ulcer
Where possible, manometry should be ordered if you have symptoms of:
* Heartburn or nausea after eating (GORD)
* Problems swallowing [feeling that food is stuck behind the breast bone (achalasia)]
