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==Description==

==Description==

'''Lymphangiectasia''' is characterised by dilation and dysfunction of the [[Lymphatic Vessels - Anatomy & Physiology|lymphatic vessels]] of the intestines.  Consequently, protein rich [[Lymph - Anatomy & Physiology|lymph]] leaks into the intestinal lumen, causing a [[Protein Losing Enteropathy|

'''Lymphangiectasia''' is a disease of the intestinal [[Lymphatic Vessels - Anatomy & Physiology|lymphatic vessels]] that results in the leakage of protein rich [[Lymph - Anatomy & Physiology|lymph]] leaks into the intestinal lumen, producing a [[Protein Losing Enteropathy|protein-losing enteropathy]](PLE) and severe lipid malabsorption.   

protein-losing enteropathy]] and severe lipid malabsorption.  It is relatively common in dogs but rare in cats.   

Lymphangiectasia can be classified into a primary or a secondary lymphangiectasia.  '''Primary lymphangiectasia''' may form part of a localised or a more widespread lymphatic abnormality.  '''Secondary lymphangiectasia''' results from lymphatic obstruction, which may be caused by:

Lymphangiectasia can be classified into a primary or a secondary disease.  '''Primary lymphangiectasia''' usually only affects the intestine but it occasionally involve a concurrent [[Chylous Effusion|chylothorax]].  It occurs due to a congenital defect of the lymphatic vessels but it may be associated with inflammation of the lymphatics, so-called '''lipogranulomatous lympangitis'''.  The relationship with lipogranulomatous lymphangitis is currently unclear and it is possible that either condition could result in the development of the other.  '''Secondary lymphangiectasia''' occurs with any pathological process that causes lymphatic obstruction, of which the most common are:

*[[Inflammation - Pathology|inflammation]],[[Neoplasia - Pathology|neoplastic]] infiltration or fibrosis

*'''Inflammation''' and subsequent fibrosis of the lymphatics, obstructing the lumina of the vessels.

*thoracic duct obstruction

*'''Neoplastic infiltration or erosion''' of the walls of lymphatic vessels.

*[[Heart Failure, Right-Sided|right sided cardiac failure]]

*'''Obstruction of the thoracic duct''', the major lymphatic vessel that runs through the chest.  This may occur due to rupture and subsequent inflammation or due to the presence of a neoplastic mass.

*'''[[Heart Failure, Right-Sided|Right-sided heat failure]]''' (including cardiac tamponade) causes an increase in central venous pressure, reducing the pressure gradient between the thoracic duct and the subclavian veins with which it anastomoses.

Lymphangiectasia often accompanies a lipogranulomatous [[Inflammation - Pathology|inflammation]], but it is not clear which is the primary event.  [[Oedema - Pathology#Lymphatic oedema|Lymphangitis]] can cause lymphatic obstruction but the leakage of [[Lymph - Anatomy & Physiology|lymph]] can also cause a [[Chronic Inflammation  - Pathology#Granulomatous Inflammation|granuloma]] to form.

*caval obstruction?

==Diagnosis==

==Diagnosis==

===Clinical Signs===

===Clinical Signs===

*Weight loss

*Chronic [[Diarrhoea|diarrhoea]]; steatorrhoea

*'''Weight loss''' in the face of '''polyphagia''' due to loss of fat and protein.

*Ascites, oedema or chylothorax may result if there is severe hypoproteinaemia or lymphatic obstruction

*'''Chronic [[Diarrhoea|diarrhoea]]''' or '''steatorrhoea''', the latter occurring due to the high fat content of the faeces.  The presence of large quantities of fat in the intestinal lumen provides a substrate for bacteria which produce hydroxy-fatty acids as by-products.  Bacterial proliferation may result in concurrent small intestinal bacterial overgrowth (SIBO) and the hydroxy-fatty acids act as potent secretagogues in the colon, leading to the production of diarrhoeic faeces.

*'''Effusions''' may develop for a number of reasons in animals with lymphangiectasia.  Ascites composed of a [[Transudate|transudate]] may develop in severely [[Hypoalbuminaemia|hypoproteinaemic]] animals but, in animals that develop secondary lymphangiectasia due to right-sided heart failure, a [[Modified Transudate|modified transudate]] may form due to portal hypertension.  If the major lymphatic vessels of the abdomen are disrupted (by a neoplastic mass), [[Chylous Effusion|chylous ascites]] may develop, although this is very rare.  In animals with congenital lymphangiectasia or in those with disruption of the thoracic duct, chylothorax may also be described.

*[[Stomach and Abomasum Consequences of Gastric Disease - Pathology|Vomiting]], lethargy and anorexia (less common)

*[[Stomach and Abomasum Consequences of Gastric Disease - Pathology|Vomiting]], lethargy and anorexia are not common clinical signs.

 

===Laboratory Tests===

===Laboratory Tests===

====Haematology====

====Haematology====

*'''[[Changes in Inflammatory Cells Circulating in Blood - Pathology #Lymphopenia|Lymphopaenia]]''' occurs as lymphocytes are the major type of cell present in lymph and they are therefore lost into the intestinal lumen in large numbers.

*'''[[Changes in Inflammatory Cells Circulating in Blood - Pathology #Lymphopenia|Lymphopaenia]]'''

====Biochemistry====

====Biochemistry====

*'''Hypocholesterolaemia'''

*[[Hypocalcaemia - Small Animal|Hypocalcaemia]] due to hypoproteinaemia, vitamin D and calcium malabsorption

*'''Hypocholesterolaemia''' and a reduction in the circulating concentration of triglycerides occur as these nutrients are lost into the intestinal lumen.

*Hypomagnesaemia

*[[Hypocalcaemia - Small Animal|'''Hypocalcaemia]]''' occurs due to hypoproteinaemia (reducing the total but not ionised calcium concentration) and due to vitamin D and calcium malabsorption.  Hypocalcaemic tetany may be observed in animals which are severely hypocalcaemic and which then become stressed or excited.

*'''Hypomagnesaemia''' may also develop due to malabsorption but this is rarely recognised in clinical practice.

[[Image:Lymphangiectasia.jpg|thumb|right|300px|Lymphangiectasia Endoscopy- Copyright Karin Allenspach's lecture RVC]]

[[Image:Lymphangiectasia.jpg|thumb|right|300px|Lymphangiectasia Endoscopy- Copyright Karin Allenspach's lecture RVC]]

====Other Tests====

====Other Tests====

*Faecal α1-proteinase inhibitor concentrations or chromium 51-labelled albumin may be used to confirm [[Protein Losing Enteropathy|protein-losing enteropathy]].

Further tests may be used to confirm the presence of [[Protein Losing Enteropathy|protein-losing enteropathy]], including measurement of '''faecal alpha-1 protease inhibitor concentration''' and '''faecal 51-Chromium albumin concentration''' after intra-venous injection.

 

===Diagnostic Imaging===

===Diagnostic Imaging===

====Ultrasound====

====Ultrasonography====

Abdominal ultrasonography may reveal pleural fluid or ascites as well as helping to narrow down other differential diagnoses.  Mucosa of intestinal loops may appear thickened due to oedema.

Ultrasound scans may reveal the presence of effusions (pleural fluid or ascites) and may be used to rule out other causes of PLE.  The mucosa of affected intestinal loops may appear to be thickened and may also appear to have 'tiger stripes', although the latter finding is an unreliable indicator of lymphangiectasia.  

====Endoscopy====

====Endoscopy====