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Vascular Ring Anomalies (view source)

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Most commonly found in dogs and cats.  Acyanotic; clinical signs due to constriction of the [[Oesophagus - Anatomy & Physiology|oesophagus]]:
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== Introduciton<br> ==
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*Regurgiation of food, usually noticed at weaning.
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*Aspiration pneumonia.
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====Persistent Right Aortic Arch====
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This congenital condition is most commonly found in dogs after weaning, but is very rare in cats. <br>
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Most common vascular ring anomaly, increased incidence in GSDs, and Irish setters. vascular ring forms between the ductus arteriosus/ligamentum arteriosum and the persistent right aorta.
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Persistent Right Aortic Arch is the most common vascular ring anomaly, increased incidence in GSDs, and Irish setters. vascular ring forms between the ductus arteriosus/ligamentum arteriosum and the persistent right aorta. [[Megaoesophagus]] is seen cranial to the constriction. Other causes include a&nbsp;Double aortic arch and Anomalous subclavian arteries. These arise form the aortic arch rather than the brachiocephalic artery.  
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[[Megaoesophagus]] is seen cranial to the constriction.
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Other causes include:
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During normal embryonic development there are five pairs of aortic arch arteries (1-6, 5 is absent) that undergo developmental changes necessary to form the major arteries of the head, neck, and upper thorax.
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[[Image:dextra-aorta.jpg|right|thumb|200px|<small><center>'''Dextra-aorta'''. Courtesy of A. Jefferies</center></small>]]
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====Double aortic arch====
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Malformations of the aortic arch arteries can cause several vascular ring anomalies, but the most commonly seen anomaly is persistent right aortic arch (PRAA). With PRAA, the esophagus and trachea are most often encircled by the left ligamentum arteriosum as they pass over the heart base causing chronic esophageal and tracheal compression.
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====Anomalous subclavian arteries====
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Arise form the aortic arch rather than the brachiocephalic artery.
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When a young animal with PRAA is weaned onto solid food, the esophageal and tracheal compression causes food stasis above the narrowed esophageal foramen leading to megaesophagus. Continued stress on the esophagus in this manner can cause permanent damage. Additionally, aspiration pneumonia and the resulting respiratory distress is a complication of postprandial regurgitation.<br>
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''Diagnosis:''
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<br>
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*Ventral deviation of the trachea and dilation of the oesophagus on radiology.
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*Barium swallow definitive.
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''Treatment:''
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== Clinical Signs<br> ==
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*Surgical resection possible.
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*Dietary management usually sufficient to control regurgitation.
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Clinical signs are usually due to constriction of the oesophagus, such as regurgiation of food, usually noticed at weaning and aspiration pneumonia. This may ne seen as coughing. The animal may present as 'vomitting' but thorough physical exam should distinguish this from regurgitation. Respiratory distress may also be seen. Stunted growth, thin and malnourished with an increased appetite may also be a clinical sign. <br>
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<br>
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== Diagnosis''<br>''  ==
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History and clinical signs plus age and breed may be indicative of the disease. <br>
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*Seen most frequently in young animals right after weaning
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On physical exam, there will be no caridac murmours unless a PDA is alos present. A palpable dialted cervical oesophagus may be detected.<br>
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*Common in dogs
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Radiographs should be taken for further diagnostics and will show a ventral deviation of the trachea and dilation of the oesophagus. A barium swallow will provide definative diagnosis of this condition.<br>
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*Very rare in cats
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<br>
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===Signalment===
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== Treatment''<br>''  ==
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*Genetics & Predisposed Breeds: Large breeds make up the majority of cases such as:
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Surgical resection of the vascular ring anomaly is possible, by refferal to a specialist cardiac surgeon.&nbsp;Dietary management is usually sufficient to control regurgitation, such as feeding from a platform and feeding small amounts of liquidised food.&nbsp;
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<br>
    
<gallery>
 
<gallery>
 
Image:GermanShep.jpg|'''German Shepherd (Alsatian)'''<p> Ellen Levy Finch (2004) WikiMedia Commons
 
Image:GermanShep.jpg|'''German Shepherd (Alsatian)'''<p> Ellen Levy Finch (2004) WikiMedia Commons
 
Image:greatdane.jpg|'''Great Dane'''<p> Lilly M (2007) WikiMedia Commons
 
Image:greatdane.jpg|'''Great Dane'''<p> Lilly M (2007) WikiMedia Commons
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</gallery>
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</gallery>  
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===Description===
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*During normal embryonic development there are five pairs of aortic arch arteries (1-6, 5 is absent) that undergo developmental changes necessary to form the major arteries of the head, neck, and upper thorax.
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*Malformations of the aortic arch arteries can cause several vascular ring anomalies, but the most commonly seen anomaly is persistent right aortic arch (PRAA). With PRAA, the esophagus and trachea are most often encircled by the left ligamentum arteriosum as they pass over the heart base causing chronic esophageal and tracheal compression.
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*When a young animal with PRAA is weaned onto solid food, the esophageal and tracheal compression causes food stasis above the narrowed esophageal foramen leading to megaesophagus. Continued stress on the esophagus in this manner can cause permanent damage. Additionally, aspiration pneumonia and the resulting respiratory distress is a complication of postprandial regurgitation.
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===Diagnosis===
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====History & Clinical Signs====
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-Regurgitation (Postprandial=after meals)
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-Coughing
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-Respiratory distress
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-Small size
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-Underweight (Malnourished)
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-Increased appetite
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====Physical Exam====
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-No cardiac murmurs unless PDA is also present
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-Palpable dilated cervical esophagus
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====Radiographic Findings====
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-Megaesophagus in the thoracic inlet (+/- barium series)
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====Echocardiographic Findings====
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Not used to diagnose a PRAA
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====Electrocardiographic (ECG)====
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Not used to diagnose a PRAA
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===Treatment===
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-Surgical sectioning of the vascular ring anomaly to relieve constriction of the esophagus and trachea
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-Management of esophageal damage: frequent feeding of small semi-solid/liquid meals from an elevated position
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===Prognosis===
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-Good with surgery
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<br>
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-Less favourable if there is extensive esophageal damage
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== Prognosis<br> ==
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==from megaoesophagus page:
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Good with surgery, but less favourable if there is extensive esophageal damage. If surgery cannot be performed, for what ever reason, then thoughts into the quality of life of the animal without surgery must be taken into consideration.
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[[Image:Praa.gif|right|thumb|125px|<center>Post-mortem specimen of an animal with a persistent right aortic arch <br><small> Copyright Alun Williams 2009 (RVC))</center></small>]]
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[[Image:Praa.gif|thumb|right|125px|<center>Post-mortem specimen of an animal with a persistent right aortic arch <br /><small> Copyright Alun Williams 2009 (RVC))&lt;/center&gt;</small>]] <br>
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Vascular rings are congenital abnormalities of the aortic arch system which interfere with [[Oesophagus - Anatomy & Physiology|oesophageal]] function. Many vascular anomalies (such as an aberrant right subclavian artery) are clinically silent and up to 20% of dogs and cats may possess such an anomaly.  Clinically significant anomalies are found most commonly in large breed dogs, particularly Irish setters and German Shepherd dogs. 
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The most common clinically significant anomaly is a '''dextra-aorta''' or '''persistent right aortic arch''', in which the aorta is formed by the fourth right branchial arch rather than the fourth left arch.  In the normal animal, the aorta, pulmonary artery and ductus arteriosus (which connects the former vessels) all lie on the left side of the oesophagus but, when the aorta develops on the right, the ductus arteriosus must pass across the oesophagus to reach the aorta.  The oesophagus is then trapped within a ring formed by the '''aorta''' (on the right), the '''main pulmonary artery''' (on the left), the '''ductus arteriosus''' (or ligamentum arteriosum) dorsally and the '''heart base''' ventrally.  The compression and stricture produced by the vascular ring prevents the passage of solid food beyond the heart base and food accumulates cranial to the obstruction.  This results in dilation (megaoesophagus) which is usually confined to the cranial thoracic region but, in chronic cases, may extend along its entire length.
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== References<br> ==
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The condition usually becomes apparent at weaning when animals start to eat solid food that cannot pass through the constricted region. Affected animals tend to regurgitate undigested solid food but, if they are presented for treatment before severe dilation occurs, surgical correction of the ring (if possible) should result in a good prognosis.
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Ettinger, S.J. and Feldman, E. C. (2000) Textbook of Veterinary Internal Medicine Diseases of the Dog and Cat Volume 2 (Fifth Edition) W.B. Saunders Company<br>Ettinger, S.J, Feldman, E.C. (2005) Textbook of Veterinary Internal Medicine (6th edition, volume 2)W.B. Saunders Company<br>Fossum, T. W. et. al. (2007) Small Animal Surgery (Third Edition) Mosby Elsevier <br>Merck &amp; Co (2008) The Merck Veterinary Manual (Eighth Edition) Merial<br>Nelson, R.W. and Couto, C.G. (2009) Small Animal Internal Medicine (Fourth Edition) Mosby Elsevier. <br>
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==Test yourself with the Developmental Pathology Flashcards==
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<br>
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[[Cardiovascular Developmental Pathology Flashcards]]
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<br>
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== Test yourself with the Developmental Pathology Flashcards ==
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[[Cardiovascular Developmental Pathology Flashcards]]
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[[Category:Cardiovascular_System_-_Developmental_Pathology]][[Category:Oesophagus - Pathology]]
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[[Category:Cardiovascular_System_-_Developmental_Pathology]] [[Category:Oesophagus_-_Pathology]] [[Category:To_Do_-_Review]] [[Category:Cardiac_Diseases_-_Cat]] [[Category:Oesophageal_Diseases_-_Cat]] [[Category:Cardiac_Diseases_-_Dog]] [[Category:Oesophageal_Diseases_-_Dog]] [[Category:Cardiac_Diseases_-_Horse]] [[Category:Oesophageal_Diseases_-_Horse]] [[Category:Cardiac_Diseases_-_Cattle]] [[Category:Cardiac_Diseases_-_Pig]]
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[[Category:To_Do_-_Cardiovascular]]
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[[Category:Cardiac Diseases - Cat]][[Category:Oesophageal Diseases - Cat]][[Category:Cardiac Diseases - Dog]][[Category:Oesophageal Diseases - Dog]]
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[[Category:Cardiac Diseases - Horse]][[Category:Oesophageal Diseases - Horse]]
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[[Category:Cardiac Diseases - Cattle]]
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[[Category:Cardiac Diseases - Pig]]
 
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