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Anaemia is a reduction in red cell mass and oxygen carrying capacity. It has many different causes, which can be divided into three basic groups:

[[File:NationWide Logo.jpeg|right|link=https://www.nwlabs.co.uk/|alt=NationWide Logo|320x320px|frameless]]Anaemia is a reduction in red cell mass and oxygen carrying capacity. It has many different causes, which can be divided into three basic groups:

* Blood loss – haemorrhagic anaemia

* Blood loss – haemorrhagic anaemia

** Secondary to other systemic diseases

** Secondary to other systemic diseases

All three types can give rise to chronic anaemia but only haemorrhagic or haemolytic anaemia can be acute. This is because of the long life span of erythrocytes (110 days in the dog, 70 days in

All three types can give rise to chronic anaemia but only haemorrhagic or haemolytic anaemia can be acute. This is because of the long life span of erythrocytes (110 days in the dog, 70 days in the cat). Even if there were a sudden complete arrest in RBC production, a discernible fall in RBC mass would take several days to develop; hypoproliferative anaemias are always chronic.

 

the cat). Even if there were a sudden complete arrest in RBC production, a discernible fall in RBC mass would take several days to develop; hypoproliferative anaemias are always chronic.[[File:NationWide Logo.jpeg|right|link=https://www.nwlabs.co.uk/|alt=NationWide Logo|240x240px|In Partnership with NationWide Laboratories|frameless|thumb|]]

 

== Clinical signs of anaemia ==

== Clinical signs of anaemia ==

'''Nonspecific clinical signs:'''

'''Nonspecific clinical signs:'''

These signs are not seen with mild anaemia but become more pronounced as the severity increases.

These signs are not seen with mild anaemia but become more pronounced as the severity increases.

All the signs except a haemic murmur could occur with severe shock. (Haemorrhagic shock occurs when 1⁄3 total blood volume is lost over a short period of time or 1⁄2 of the total blood volume is lost over 24 hours). In shock, capillary refill time is prolonged (>2s).

Mucous membranes can appear pale in many non-anaemic cats.  

Mucous membranes can appear pale in many non-anaemic cats. With anaemia of comparable severity the signs are more pronounced:

With anaemia of comparable severity the signs are more pronounced:

* In the dog than the cat

* In the dog than the cat

* If rapid onset - clinical signs are more pronounced with acute than chronic anaemia

* If rapid onset - clinical signs are more pronounced with acute than chronic anaemia

* In older animals due to reduced ability to compensate compared with younger animals n In haemolytic compared to haemorrhagic anaemia

* In older animals due to reduced ability to compensate compared with younger animals

* In haemolytic compared to haemorrhagic anaemia

{| class="wikitable"

{| class="wikitable"

* Jaundice - associated with acute haemolytic anaemia or following severe haemorrhage into a body cavity

* Jaundice - associated with acute haemolytic anaemia or following severe haemorrhage into a body cavity

* Petechial haemorrhages - thrombocytopaenia, von Willebrand disease (see section on coagulopathies

* Petechial haemorrhages - thrombocytopaenia, von Willebrand disease (see section on coagulopathies)

* Pyrexia - often accompanies immune-mediated disease

* Pyrexia - often accompanies immune-mediated disease

* Hepatic and/or splenic enlargement - may occur with immune-mediated destruction of erythrocytes or platelets, extramedullary haematopoiesis (rarely causes hepatomegaly), lymphoma/leukaemia

* Hepatic and/or splenic enlargement - may occur with immune-mediated destruction of erythrocytes or platelets, extramedullary haematopoiesis (rarely causes hepatomegaly), lymphoma/leukaemia

* No erythroid response is expected in the first 1-3 days (preregenerative phase)

* No erythroid response is expected in the first 1-3 days (preregenerative phase)

* Polychromasia and reticulocytosis peak at 4-5 days. In the dog, if there is polychromasia, a reticulocyte count is usually unnecessary because the degree of polychromasia reflects the degree of regeneration (reticulocytosis). In the cat,the degree of polychromasia reflects the aggregate reticulocyte count

* Polychromasia and reticulocytosis peak at 4-5 days. In the dog, if there is polychromasia, a reticulocyte count is usually unnecessary because the degree of polychromasia reflects the degree of regeneration (reticulocytosis). In the cat, the degree of polychromasia reflects the aggregate reticulocyte count

A reticulocyte count is useful to quantify the erythroid response in non- and poorly regenerative anaemias.  

A reticulocyte count is useful to quantify the erythroid response in non- and poorly regenerative anaemias.  

|>200 (>5%)  

|>200 (>5%)  

|}

|}

'''Macrocytic normochromic.''' This is an uncommon category, usually seen in cats as a nonregenerative anaemia associated with FeLV infection or myelodysplasia. Rarely macrocytic normochromic anaemia can indicate vitamin B12 deficiency, for example malabsorption. Macrocytic anaemia has also been associated with folate antagonists such as phenytoin.

'''Macrocytic normochromic.''' This is an uncommon category, usually seen in cats as a nonregenerative anaemia associated with FeLV infection or myelodysplasia. Rarely macrocytic normochromic anaemia can indicate vitamin B12 deficiency, for example malabsorption. Macrocytic anaemia has also been associated with folate antagonists such as phenytoin.

'''Diagnosis of regenerative anaemia'''

'''Diagnosis of regenerative anaemia'''

'''External blood loss.''' History including possible access to rodenticide. Look for biochemical evidence of hypoproteinaemia and/or hypoalbuminaemia? Check for thrombocytopaenia or other bleeding tendencies (buccal mucosal bleeding time, OSPT, APTT). If the anaemia is microcytic, or faeces are dark, consider GI blood loss. Testing faeces for occult blood may clarify.

'''External blood loss.''' History including possible access to rodenticide. Look for biochemical evidence of hypoproteinaemia and/or hypoalbuminaemia? Check for thrombocytopaenia or other bleeding tendencies (buccal mucosal bleeding time, OSPT, APTT). If the anaemia is microcytic, or faeces are dark, consider GI blood loss. Testing faeces for occult blood may clarify.

* Pancytopaenia or bicytopaenia. Proceed to bone marrow examination

* Pancytopaenia or bicytopaenia. Proceed to bone marrow examination

Clinical chemistry profile

'''Clinical chemistry profile'''

* Anaemia secondary to renal disease (usually chronic renal disease) or hepatic disease   

* Anaemia secondary to renal disease (usually chronic renal disease) or hepatic disease   

* Chronic systemic disease may cause anaemia  

* Chronic systemic disease may cause anaemia  

'''Microcytic hypochromic RBCs'''

'''Microcytic hypochromic RBCs'''