90 - Oesophagus Flashcards
What are the three ‘sections’ of the oesophagus?
Describe the course within each section
Cervical
* Dorsal to the cricoid cartilage
* Runs to the left of the trachea
* Ends at the thoracic inlet
Thoracic
* To the left of the trachea at the thoracic inlet
* Becomes dorsal at the tracheal bifurcation
* Ends at the oesophageal hiatus
Terminal
* Short wedge shaped abdominal portion
* Extends from oeosphageal hiatus to the cardia
What are the layers of the oesophagus?
Mucosa
* Stratified squamous epithelium
* Longitudinal folds
* Herringbone appearance in cats
Submucosa
* Allows independent mucosal movement
* Contains mucous glands which lubricate mucosa
Muscularis
* 100% striated muscle in dogs
* Terminal portion is smooth muscle in cats
* Functional sphincters at cranial and caudal ends
* Arises from the cricopharyngeus muscle and circo-oesophageal tendon (fixed attachment to cricoid)
* Two distinct sheets which form left and right-handed spirals
* Fibres in inner coat become transverse, blending with oblique fibres of the stomach
* Fibres in outer coat become more longitudinal, blending with longitudinal fibres of stomach
Adventitia
* Blending with deep cervical fascia, pleura and peritoneum
* Connected to diaphragm by phrenico-oesophageal membrane
Describe the anatomy of the ‘Oesophageal Spincters’
Both are functional – not anatomical
Upper
* Formed by Cricopharyngeus and Thyropharyngeus muscles and associated elastic tissue
‘Pharyngoesophageal junction’
Lower
* Thickening of circumferential striated muscle at gastroesophageal junction (dogs)
What three other structures contribute to the lower oesiphageal ‘sphincter’
- Diaphragmatic crura
- Angle of the gastroesophageal junction
- Folds of mucosa
Describe the arterial supply to the oesophagus
‘Segmental’
Cervical region
* Cranial and caudal thyroid artery
Thoracic region
* Bronchoesophageal artery supplies the cranial 2/3
* Oesophageal branches of aorta and dorsal intercostal arteries supply caudal 1/3
Terminal region
* Branches of LEFT GASTRIC artery
Describe the venous drainage for the oesophagus
Cervical
* Drain into external Jugular
Thoracic
* Azygous
Terminal
* Portal venous system
Which Lymph nodes do the oesophagus drain to?
- Medial retropharyngeal
- Deep cervical
- Cranial mediastinal
- Portal
- Splenic
- Gastric
Describe the innervation to the oesophagus
- Paired pharyngoesophageal nerves
- Recurrent laryngeal nerve
- Dorsal and ventral vagal trunks
Branches of the vagus nerve
Recap the phases of swallowing
1) Oropharnyngeal = Oral (voluntary), pharyngeal, cricopharnygeal = CN V, VII, IX, X, XII
2) Oesophageal = Sufficiently large food bolus generates primary and then secondary peristaltic waves
3) Gastroesophageal = Muscularis ahead of the bolus relaxes to propell through the GEJ into the stomach
What are the normal oesophageal transit times for dogs with liquid vs kibble?
In sternal = 2.6s for liquid; 4.4s for kibble
In right lateral = 7.2s for liquid; 8.9s for kibble
Primary peristaltic waves initiated by swallows more frequently in sternal than lateral
How can the causes of oesophageal dysphagia be divided?
Mechanical = Anatomic
* Mural/luminal = Hiatal hernia, Gastroesophagal intussusception, FB, stricture, mass
* Extramural = Vascular ring or mass
Functional = Neuromuscular
* Megaoesophagus = idiopathic or due to neuromuscular disease
Inflammatory = Oesophagitis
* Reflux due to GA, hiatal hernia, chronic vomiting, malpositioned tubes
* Other = corrosives, thermal burns, radiation, FBs
Summarise the reflex control of swallowing
Oral phase voluntary (CN V - tongue, VII - masticatory muscles, XII - tongue )
swallowing centre (IX - Pharnyx and X - Pharynx, larynx and oesophagus)
What factors contribute to an increased risk of dehiscence?
(5)
- Lack of serosa
- Segmental blood supply
- Motion from swallowing
- Tension due to fixed anatomical position
- Lack of omentum
Why does lack of serosa impair healing?
Serosa provides an early fibrin seal and mesothelial stem cells for healing
Pleural mesothelium does act similarly to serosa in the thoracic oesophagus
What is the most important factor in wound dehiscence of the oesophagus?
The integrity of the intramural plexus
- Provided this is intact, and collateral blood supply is present in the other segments, resection and anastmosis can be successful
How can motion of the oesphagus be limited?
Witholding food and water
1-7 days
Place an G tube or enterostomy tube!
Which approach should be selected for the cervical oesophagus?
Ventral cervical midline
Which approaches are appropriate for the cranial thoracic oesophagus?
Median sternotomy
* Can be used with ventral cervical midline
* Access up to the tracheal bifurcation
Left ICS 3/4
* Ventral retraction of the brachiocephalic trunk and subclavian vessels to access
Right ICS 3/4/5
* Ventral retraction of the trachea
* Ventral retraction of the azygous at the heart base (or ligation if necessary)
Which approach is appropriate for the caudal thoracic oesophagus?
Left ICS 7/8/9
* Avoids the vena cava on the right
* Essential to identify/preserve the dorsal and ventral vagus n.
(Useful to combine with Left paracostal incision for omental pedical flap, tunneled through diaphragm)
Which approach is appropriate for the terminal oesophagus
Ventral midline coeliotomy
* Extended to caudal median sternotomy if needed
* +/- diaphragmatic incision
Which suture material should be used for the oesophagus?
Monofilament
Slowly absorbably
Minimally reactive
e.g. Polydioxanone (PDS) or Polygloconate (Maxon)
How should sutures be placed in the oesophagus?
- Appositional
- 2mm from cut edge
- 2-3 mm apart
- Single later
- Simple interrupted
Submucosa is functional holding layer
Give 2 reasons why simple interrupted sutures preferred in the oesophagus
- Reduce vascular compromise in the intramural layer
- Allows dilation of the oesophagus
Can use double layer (superior to simple continuous)
Simple continous fine for otomy repair
(I like to preplace interupteds to ensure good bites before typing off)
Describe the technique for oesophagotomy
- Suction material from oesophagus transorally
- Isolate with moist lap sponges
- Obstruct material with fingers, umbilical tape, atraumatic clamps
- Incision made longitudinally
- Bites 2 mm from edge and 2-3mm apart
- Single layer closure = Full thickness with minimal mucosa, extraluminal knots
- Two layer closure: Mucosa/submucosa intraluminal knots, muscularis/adventitia extraluminal knots
- +/- omentalise/muscle patch
NPO 24- 48 hrs
Otube can delay healing
What steps should be taken pre op before considering oesophageal R&A?
- Estimate length of resection pre op (Contrast US, CT, MRI)
- Consider need for oesophageal substitution techniques
What % of the oesophagus can be resected
< 3 - 5 cm
Realistically any resection > 3-5 cm has an increased risk of dehiscence
What % of the cervical oesophagus and thoracic oesophagus has been successfully resected experimentally?
Cervical = 20%
Thoracic = 50%
Descibe the technique for oesophageal resection and anastomosis
- Care with excessive mobilisation and damage to segmental blood supply
- Stay sutures for handling and alignment
- Single or two layer closure
- Far oesophageal wall sutured first
- Stapling devices can be used (via mouth, pharyngotomy or gastrostomy)
- NPO for 1 week post op
- G-tube or E-tube required
- Follow up swallow study at 1 and 3 months - Assess for stricture and oesophageal function
What technique can be performed to reduce the tension on an oesophageal resection and anastomosis?
Describe key steps
Circumferential partial myotomy
- Performed 2-3cm proximal, distal or both from the R&A site
- Layers separated by injecting saline into the muscularis
- Partial avoids damage to the intramural plexus compared with complete myotomy
- Heals by second intention without stricture or diverticulum
How can the oesophageal repair be reinforced?
Oesophageal patching
How can oesophageal patches be applied?
On-lay = Reinforcement of incisions at risk of dehiscence due to poor blood supply
In-lay = Partial circumferental replacement
Which host tissues can be used as on-lay oesphageal patches?
Omental pedicle flap
Pericardium
Sternothyroideus
Longus coli
Free buccal mucosa
Vascularised pedicle graft from internal/external intercostal
Diaphragmetic pedicle
Stomach/small intestine
Adjacent lung
How is an omental pedicle flap formed?
- Via paracostal or midline abdo incision
- Right gastrepiploic arterial branches ligated
- Brought through incision in diaphragm and tacked to site
Vascular, available, minimises stricture formation
What is the concern regarding using adjacent lung to reinforc oesophageal repair?
Oesophagopulmonary fistula formation
Which Xenogenic or artifical tissues can be used as oesophageal patches?
Porcine SIS
Lyophylised dura mater
Collagen coated vicryl mesh
PTFE (Gortex)
Which tissue types can be used for oesophageal substitution?
Skin grafts
Muscle grafts
GI based techniques
Name three techniques for oesophageal reconstruction using the cervical skin?
Inverse tubed skin graft
Creation of oesophagocutaneous fistulas
Omocervical cutaneous island axial pattern flap
Describe the techniques for inversed tubed skin graft
1:
* Single pedicle skin flap formed into tube and sutured distally to oesophagus cut end
* Two weeks later cranial skin pedicle cut and sutures to cranial end of oesophagus
2:
* Two oesophagocutaneous fistulas created by suturing cut end to skin
* Several weeks later skin between inverted to form tube connecting two ends of the oesophagus and cervical skin closed over the top
3:
* Omocervical cutaneous island axial pattern flap based on the omocervical vessels can create one stage tube skin graft
What are downsides to use of skin grafts for oesophageal substitution?
- Can block with hair
- Lacks peristalsis
- Indistensible
Give three examples of oesophageal substitution using muscle grafts
Which location can they be used in?
- Tubed intercostal musculpleural pedicle graft = Cranial thoracic
- Diaphragmatic pedicle graft = Caudal thoracic (or terminal)
- Epithelial lined oesophageal conduit from latissimus dorsi musculocutaenous flap based on thoracodorsal vessles = Thoracic
Name 4 techniques for oesophageal substitution using the GI tract
- Gastric advancement and oesophagogastric anastomosis
- Iso and antiperistaltic gastric tubes
- Jejunal or conolic pedicle grafts
- Microvascular free grafts
GI pedicle grafts hampered by mobility of the vascular pedicle
Where are iso/antiperistatic tubes harvested from?
What is the difference between iso and anti?
What other procedures need to be performed?
Created from the greater curvature of the stomach
Anti = Reverse
- Created so maintains luminal connection with the fundus
- Advanced into the thorax for anastomosis
Iso = Maintains peristalsis in an aboral direction
- Separated at both ends to form pedicle graft
Other procedures =
* Splenectomy and ligation of the ometalgastroepiplic vessels
* Pyloromyoplasty recommended to enhance gastric emptying (vagal disruption likely)
Portion of tube should remain in the abdomen to prevent reflux
With GI microvascular free grafts, which location is most feasible?
Which vessels can it be anastomosed to?
Middle colic:
* vessels are larger
* provides a longer segment
* more tolerant to ischaemia
In cervical region
- Carotid and cranial thyroid a.
- Jugular, omobrachial or lingofacial veins
What causes congenital megaoesophagus?
Idiopathic
Suspected to be due to defect in vagal afferent innervation
Which breeds are affected by congenital MO?
GSD
Irish setters
Great Danes
Newfies
Labs
Sharpei’s
Mini schnauzers
Fox Terriers
What is the mortality rate of congenital MO?
74% by 1 year old
Describe the lateral approach for cricoharyngeal myotomy
RIGHT lateral with towel under neck
Orogastric tube placed to ID oesophageal wall
Incision dorsal to the larynx and ventral to jugular vein through skin, suncut, platysma
Jugular and sternocephalicus retracted dorsally and sternohyoideus ventrally by gelpis
Thyroid carilage identified and fascia freed to visualise cricopharnygeus muscle
Cricopharnygeus dissected free from the oesophagus dorsally and laterally
2-2.5cm section removed from dorsal midline
Metal clips applied at rostral and caudal end of muscle transection for ID on fluoro post op
Tissue submitted for histopath
Oesophagus inspected for damage and sutured as needed
Closed routinely
Simplify the normal embronic development of the cranial aorta
Starts as ventral and dorsal aorta, connected by 6 aortic arches
- Ventra aorta fuse caudally to form the heart
- 1st and 2nd arches involute
- Ventral aortas at 1st and 2nd => EXTERNAL carotids
- Dorsal aortas at 1st and 2nd => INTERNAL carotids
- Ventral aorta between 3rd and 4th => Common carotids
- 3rd and 4th arches involute
- LEFT 4TH ARCH AND VENTRAL AORTA at this level => ADULT AORTIC ARCH
- RIGHT VENTRAL AORTA at the level of the 4th arch => BRACHIOCEPHAIC TRUNK
- Right 4th arch itself => RIGHT SUBCLAVIAN
- 7th intersegmental artery => LEFT SUBCLAVIAN
- 5th arches involute
- 6th arches => Pulmonary arteries
- LEFT pulmonary artery => DUCTUS ARTERIOSUS and after birth => LIGAMENTUM ARTERIOSUM
- Right ductus arteriosus and right dorsal aorta between 6th arch and point of fusion regress => releasing the oesophagus and trachea
Review the normal anatomy
What is the most common VRA in dogs?
Aberrant right subclavian with normal left aortic arch!!
Right SC comes from caudal position on Left arch
Causes mild dorsal compression of the oesophagus
Likely underdiagnosed/incidental finding on angiography
What is the most common CLINICALLY RELEVANT VRA in dogs?
What % of VRA does this represent?
What other anomaly can occur - how frequently?
Persistant Right Aortic Arch
95% of clinical VRAs
10% have concurrent PDA
Left 4th ICT, ligate and divide the ligamentum, transect fibrous bands
What VRA does this diagram represent?
In addition to regurgitation, what concurrent clinical signs can occur and why?
Double Aortic Arch
Causes respiratory signs
due to tracheal stenosis
CT angiography useful to determine dominant side
(Right more dominant in Matteo’s case series)
Tx = Ipsilateral Intercostal thoracotomy and division of the non-dominant arch. Tobias recommends oversewing the ends once transected
How clinically relevent is a left aortic arch and right ligamentum arteriosum?
Likely to cause clinical signs
Basically a mirror image of PRAA becase you have right ligamentum entrapping the oesophagus
Requires identification for correct RIGHT sided surgical approach (Right 4th ICT) to access, ligate and transect ligamentum
Which VRA does this diagram represent?
How will it appear on imaging?
Persistent right aortic arch with
aberrent left subclavian
Left subclavian arises from the right aortic arch and passes dorsal to the oesophagus
If the ligamentum arteriosum is from the right e.g. correct side for the arch, this anomaly will appear as as a single, incomplete, vascular ring on imaging
Tx - If clinical, the left subclavian can be divided
The vertebral artery provides sufficent collateral circulation
You diagnose a PRAA on radiographs
You perform a left 4th ICT to treat it and you see this structure*
What is it?
How frequently does it occur?
PERSISTANT LEFT CRANIAL VENA CAVA
Occurs in 45% of VRAs
Angiogram would be useful for planning
Can complicate approach
Briefly describe the surgical technique for treatment of PRAA
- Left 4th ICT (5th in cats)
- Pack lung lobes caudally
- Isolate and dorsally retract persistent left cranial vena cava with vessel loop if present
- Ligate and divide hemiazygous vein for access as needed
- Incise mediastinum longitudinally over VRA
- Preserve the vagus and recurrent laryngeal nerve which pass caudal to Ligamentum
- Identify pulmonary artery, aorta and ligamentum
- Dissected LA/PDA using right angled forceps
- Double ligated with silk and transect
- Pass OG tube through oesophagus
- Identify, dissect and transect constrictive fibres
- Massage oesophageal casts into stomach (oesophagotomy if obstructed - avoid if poss)
- Place chest drain piror to closure
Redundant oesophageal resection reported but not recommended due to risk of complication and motility distruption
