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==Introduction==

 

'''Lymphangiectasia''' is a disease of the [[Lymphatic Vessels - Anatomy & Physiology|lymphatic vessels]] that results in the leakage of protein-rich [[Lymph - Anatomy & Physiology|lymph]].  The term is usually taken to mean intestinal lymphangiectasia (in which lymph is lost into the intestinal lumen, producing a [[Protein Losing Enteropathy|protein-losing enteropathy]](PLE) and severe lipid malabsorption) but thoracic and generalised lymphangiectasia have been reported.   

==Description==

'''Lymphangiectasia''' is a disease of the [[Lymphatic Vessels - Anatomy & Physiology|lymphatic vessels]] that results in the leakage of protein-rich [[Lymph - Anatomy & Physiology|lymph]].  The term is taken to mean intestinal lymphangiectasia (in which lymph is lost into the intestinal lumen, producing a [[Protein Losing Enteropathy|protein-losing enteropathy]](PLE) and severe lipid malabsorption) but thoracic and generalised lymphangiectasia have been reported.   

Lymphangiectasia can be classified into a primary or secondary disease.  '''Primary lymphangiectasia''' usually only affects the intestine but it occasionally involves 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 between lymphangiectasia and 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:

Lymphangiectasia can be classified into a primary or secondary disease.  '''Primary lymphangiectasia''' usually only affects the intestine but it occasionally involves 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 between lymphangiectasia and 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:

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

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

*Increased pressure in the systemic veins reducing the pressure gradient from the thoracic duct to the subclavian veins

*Increased pressure in the systemic veins reducing the pressure gradient from the thoracic duct to the subclavian veins

**'''[[Heart Failure, Right-Sided|Right-sided heat failure]]''' due to [[Cardiomyopathies|cardiomyopathy]], [[Cardiac Tamponade|cardiac tamponade]] or [[Tricuspid Valve Dysplasia|tricuspid dysplasia]], [[Cor Pulmonale]] or Cor Triatriatum Dexter.   

**'''[[Heart Failure, Right-Sided|Right-sided heat failure]]''' due to [[Cardiomyopathy|cardiomyopathy]], [[Cardiac Tamponade|cardiac tamponade]] or [[Tricuspid Valve Dysplasia|tricuspid dysplasia]], [[Cor Pulmonale]] or Cor Triatriatum Dexter.   

**Obstruction to venous return by '''intra-thoracic masses''' including thymoma and thymic lymphoma.

**Obstruction to venous return by '''intra-thoracic masses''' including thymoma and thymic lymphoma.

Clinical signs are related to the loss of lymph and the resultant protein-losing enteropathy and fat malabsorption.  The following signs are therefore common:

Clinical signs are related to the loss of lymph and the resultant protein-losing enteropathy and fat malabsorption.  The following signs are therefore common:

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

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

*'''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.

*'''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 [[Antibiotic Responsive Diarrhoea|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 has also been described.

*[[:Category:Effusions|'''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 has also been described.

*[[Stomach and Abomasum Consequences of Gastric Disease - Pathology|Vomiting]], lethargy and anorexia are uncommon clinical signs.

*[[Vomiting|Vomiting]], lethargy and anorexia are uncommon clinical signs.

===Laboratory Tests===

===Laboratory Tests===

The following parameters may be altered on haematological or biochemical analysis of blood samples:

Several parameters may be altered on haematological or biochemical analysis of blood samples.

====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.

'''[[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. If an inflammatory process (such as lipogranulomatous lymphangitis) has developed, there may be a '''monocytosis''' or '''neutrophilia'''.

*If an inflammatory process (such as lipgranulomatous lymphangitis) has developed, there may be a '''monocytosis''' or '''neutrophilia'''.

====Biochemistry====

====Biochemistry====

*'''Panhypoproteinaemia''' occurs in most forms of protein-losing enteropathy and suggests that both plasma albumin and globulin are being lost.   

*'''Panhypoproteinaemia''' occurs in most forms of protein-losing enteropathy and suggests that both plasma albumin and globulin are being lost.   

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

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

*[[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.

*'''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.

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

*Changes associated with SIBO are discussed [[Small Intestinal Bacterial Overgrowth and Antibiotic Responsive Diarrhoea|here]].

*[[Antibiotic Responsive Diarrhoea|Changes associated with SIBO are discussed here]].

 

====Other Tests====

====Other Tests====

====Endoscopy====

====Endoscopy====

Grossly, multiple white lipid droplets can be seen to protrude from prominent mucosal blebs in the intestine.  The mucosa is frequently oedematous.

Grossly, multiple white lipid droplets can be seen to protrude from prominent mucosal blebs in the intestine (see image).  The mucosa is frequently oedematous.

===Histopathology===

===Histopathology===

Preferably, a full thickness intestinal biopsy should be taken to achieve a definitive diagnosis.  Care should be taken as hypoproteinaemic animals are at much greater risk of dehiscence at the biopsy sites, potentially leading to an acute septic peritonitis.  On histological examination of the biopsy sample, accumulation of lipid-laden macrophages may be detected together with a granulomatous response around distended lymphatics.

Preferably, a full thickness intestinal biopsy should be taken to achieve a definitive diagnosis.  Care should be taken as hypoproteinaemic animals are at much greater risk of dehiscence at the biopsy sites, potentially leading to an acute septic [[Peritonitis - Cats and Dogs|peritonitis]].  On histological examination of the biopsy sample, accumulation of lipid-laden macrophages may be detected together with a granulomatous response around distended lymphatics.

It is essential to distinguish a true lymphangiectasia from secondary lacteal dilation that occurs with [[Inflammatory Bowel Disease|Inflammatory Bowel Disease ]] (IBD).  In the case of IBD, an inflammatory infiltrate will be seen in the lamina propria but the degree of infiltration may be underestimated if [[Oedema - Pathology|oedema]] is present.

It is essential to distinguish a true lymphangiectasia from secondary lacteal dilation that occurs with [[Inflammatory Bowel Disease|Inflammatory Bowel Disease]] (IBD).  In the case of IBD, an inflammatory infiltrate will be seen in the lamina propria but the degree of infiltration may be underestimated if [[Oedema|oedema]] is present.

==Treatment==

==Treatment==

If the lymphangiectasia is secondary to another disease, the underlying cause should be treated.  Otherwise, the following elements should be considered in designing a treatment plan.

If the lymphangiectasia is secondary to another disease, the underlying cause should be treated.  Otherwise, the following elements should be considered in designing a treatment plan.

===Dietary modification===

===Dietary modification===

The diet should have a '''low fat content''' to reduce the production of lymph but should have a high calorie content to allow the animal to regain weight.  The fat soluble vitamins (K, E, D and A) should be supplemented.

The diet should have a '''low fat content''' to reduce the production of lymph but should have a high calorie content to allow the animal to regain weight.  The fat soluble vitamins (K, E, D and A) should be supplemented and additional calcium should be added if hypocalcaemia is documented.

===Immunosuppressive===

===Immunosuppressive===

Immunosuppressive agents are a key element in the treatment of lymphangiectasia.  Corticosteroids such as [[Steroids|prednisolone]] are used most commonly for this pupose at an immunosuppressive dose (~2 mg/kg/day in dogs).  These drugs are likely to be of most benefit in those animals that evidence of inflammatory pathology, such as lipogranulomatous lymphangitis and inflammatory infiltration of the lamina propria.  If further immunosuppression is considered necessary or if adverse effects occur with corticosteroid therapy, azathioprine or ciclosporin could also be used.

Immunosuppressive agents are a key element in the treatment of lymphangiectasia.  Corticosteroids such as [[Steroids|prednisolone]] are used most commonly for this pupose at an immunosuppressive dose (of 1-2 mg/kg/day in dogs).  These drugs are likely to be of most benefit in those animals that have evidence of inflammatory pathology, such as lipogranulomatous lymphangitis and inflammatory infiltration of the lamina propria.  If further immunosuppression is considered necessary or if adverse effects occur with corticosteroid therapy, azathioprine or ciclosporin could also be used.

===Antimicrobials===

===Antimicrobials===

[[Nitroimidazoles|Metronidazole]] or [[Macrolides and Lincosamides|tylosin]] may be used to control any secondary [[Small Intestinal Bacterial Overgrowth and Antibiotic Responsive Diarrhoea|SIBO]].  Antibiotics are thought to have effects on both the intestinal immune system and the normal enteric flora.

[[Nitroimidazoles|Metronidazole]] or [[Macrolides and Lincosamides|tylosin]] may be used to control any secondary [[Antibiotic Responsive Diarrhoea|SIBO]].  Antibiotics are thought to have effects on both the intestinal immune system and the normal enteric flora.

===Fluid therapy===

===Fluid therapy===

Short term treatment with [[Plasma - WikiBlood|plasma]] or [[Colloids|colloids]] can be instituted in severely hypoproteinaemic animals that have begun to develop clinical signs.  Diuretics such as [[Heart Failure, Treatmen#C. Pharmacological|frusemide and spironolactone]] may also be used to manage effusions.

Short term treatment with plasma or [[Colloids|colloids]] can be instituted in severely hypoproteinaemic animals that have begun to develop clinical signs.  Diuretics such as [[Heart Failure, Treatment#C. Pharmacological|frusemide and spironolactone]] may also be used to manage effusions.

==Prognosis==

==Prognosis==

The long-term prognosis is guarded as, although animals may respond to medical therapy initially, they frequently relapse and develop clinical signs associated with hypoproteinaemia.

The long-term prognosis is guarded as, although animals may respond to medical therapy initially, they frequently relapse and develop clinical signs associated with hypoproteinaemia.

==References==

==References==

*Nelson, R.W. and Couto, C.G. (2009) '''Small Animal Internal Medicine (Fourth Edition)''' ''Mosby Elsevier''.

*Nelson, R.W. and Couto, C.G. (2009) '''Small Animal Internal Medicine (Fourth Edition)''' ''Mosby Elsevier''.

[[Category:Intestine_-_Inflammatory_Pathology]]

[[Category:Intestine_-_Inflammatory_Pathology]]

[[Category:To_Do_-_James]]

 

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[[Category:Intestinal Diseases - Dog]][[Category:Intestinal Diseases - Cat]]

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