1. ERYTHROCYTE (RBC) DISORDERS: POLYCYTHAEMIA AND ANAEMIA
Haematology
ERYTHROCYTE (RBC) DISORDERS: POLYCYTHAEMIA AND ANAEMIA

2. OVERVIEW
1. Polycythaemia (erythrocytosis)
2. Anaemia
-Regenerative: blood-loss or haemolytic
-Non-regenerative: primary or secondary bone marrow disorder

3. 1.POLYCYTHAEMIA/
ERYTHROCYTOSIS

4. DEFINITION AND TYPES
An increase in PCV, Hb concentration and/or RBC count
Relative
• Dehydration (eg. increased water loss: e.g. vomiting,
diarrhoea, polyuric disorders) causing an apparent increase in RBC due to a decrease in fluid in circulation.
• Exercise, fear, excitement (eg. in the horse) causing
adrenaline secretion, splenic contraction and transient
redistribution of RBC from the spleen to the circulation.

5. DEFINITION AND TYPES Absolute (real increase in RBCs) • Secondary:
- chronic tissue hypoxia: heart/lung diseases, high altitude
- renal tumor or cysts increasing erythropietin (EPO) secretion
• Primary:
- polycythaemia vera (rare myeloproliferative disorder of RBC
precursors)

6. CLINICAL IMPLICATIONS
-Cardiovascular signs due to blood hyperviscosity and peripheral hypoxia (increased pulse and
respiratory rate)
-Neurological signs (syncope, lethargy) due to poor brain perfusion, and bleeding tendencies

7. LABORATORY DIAGNOSIS OF DIFFERENT CAUSES
Relative
• Dehydration: total protein and albumin
Absolute
• Secondary to chronic hypoxia: arterial pO2
• Renal tumours or cysts (or others): erythropoietin EPO*)
• Polycythaemia vera: EPO
*Human immunoassays kits should be validated prior to use for measurement of canine and feline erythropoietin

8. 2. ANAEMIA

9. Anaemia regenerative non regenerative TYPES OF ANAEMIA haemolytic
haemorrhagic
Anaemia
secondary B-M
disorders
B-M (bone-marrow)
non
regenerative
primary B-M
disorders

10. ANAEMIA
A decrease in PCV, Hb concentration and/or RBC count
Low PCV

11. ANAEMIA: CLINICAL IMPLICATIONS
- Inadequate tissue oxygenation
• pale mucous membranes
• weakness, inappetance, anorexia
• syncope
- Compensatory mechanisms
• tachypnoea (particularly if forced to exercise)
• tachycardia, small and strong pulse

12. ANAEMIA: CLINICAL IMPLICATIONS
-Signs which may be associated with cause of anaemia
• icterus
• bleeding (petechiae,ecchymoses, melena, haematuria, haematomas)
• fever
• splenomegaly

13. Anaemia regenerative non regenerative TYPES OF ANAEMIA haemolytic
haemorrhagic
Anaemia
secondary BM
disorders
B-M (bone-marrow)
non
regenerative
primary B-M
disorders

14. REGENERATIVE ANAEMIA Characterized by an increase in the number of
RETICULOCYTES produced by the bone marrow to
compensate for the anaemia.

15. SIGNS OF REGENERATIVE ANAEMIA
Reticulocytosis will produce:
-  MCV and RDW,  MCH and MCHC
- In blood smears with Romanowsky stains:
• polychromasia
• anisocytosis
See lecture 4 for abreviations.
Additionally it can be found:
-increased nucleated RBCs
-basophilic stippling
-increased number of Howell-Jolly Bodies
Secondary effects may include:
-leukocytosis with neutrophilia and left shift
-thrombocytosis

16. Anaemia regenerative non regenerative TYPES OF ANAEMIA haemolytic
haemorrhagic
Anaemia
secondary BM
disorders
B-M (bone-marrow)
non
regenerative
primary B-M
disorders

17. HAEMORRHAGIC ANAEMIA Plasma total protein generally 
(because protein is lost together with RBC)
Plasma clear
If measured in the aftermath of the loss of a lot of blood and before blood volume is restored, RBCs values and plasma protein may appear within reference ranges.

18. HAEMORRHAGIC (blood-loss) ANAEMIA
ACUTE BLOOD LOSS
Reticulocyte response will only be detected in blood after 3-4 days !!
Causes:
• Trauma, surgery
• Coagulation disorders
• Others
There are many others causes of acute blood loss such as:
- abomasal or intestinal ulceration
- severe angiostrongylus infestaion
- rupture of haemangiosarcomatous spleen
Reticulocytes does not appear in peripheral blood in all species.
Acute blood loss can cause hypotension and shock (due to severe hypovolaemia)

19. • Gastrointestinal ulceration and tumours • Parasitism
CHRONIC BLOOD LOSS
- External. Causes:
• Gastrointestinal ulceration and tumours
• Parasitism
In many cases signs of RBC regeneration are present in blood but progressive depletion of iron stores may
produce IRON DEFIENCY ANAEMIA with:
-normo to microcytosis
-hypochromasia
- ↑ platelet count
-reticulocytes can decrease
Examples of gastrointestinal tumours: carcinoma/leiomyosarcoma
Parasitism can be internal or external
- Internal : blood loss into abdomen/chest

20. IRON DEFICIENCY ANAEMIA
An increased number of platelets, and hypochromic and microcytic RBCs can be observed in the blood smear

21. Anaemia regenerative non regenerative TYPES OF ANAEMIA haemolytic
haemorrhagic
Anaemia
secondary B-M
disorders
B-M (bone-marrow)
non
regenerative
primary B-M
disorders

22. HAEMOLYTIC ANAEMIA Plasma total protein within reference range or 
Plasma can be icteric or hemolysed
Abnormal erythrocyte morphology (Heinz bodies, RBC parasites, spherocytes) may suggest a haemolytic cause for the anaemia
In haemolytic anaemia the plasma frequently appears yellow (“icteric” or “jaundiced”) due to increased RBC destruction and increased bilirubin metabolism (mostly unconjugated). In severe haemolysis, haemoglobinaemia (producing red colour in plasma) and haemoglobinuria (producing red colour in urine) may result from the body´s inability to bind Hb to haptoglobin, and the inability of the monocyte macrophage system to metabolise amounts of Hb being released.

23. IN REGENERATIVE ANAEMIAS:
TPP and plasma colour can be used to differentiate
haemolysis and haemorrhage
Haemolytic anaemia
Haemorrhagic anaemia
TPP > 60 g/L
PLASMA ICTERIC/
HEMOLYSED
TPP < 60 g/L
PLASMA CLEAR
RBC regeneration following haemolysis is usually much more marked than that following blood loss.

24. Clinical signs associated with an increase in haemoglobin
HAEMOLYTIC ANAEMIA
Clinical signs associated with an increase in haemoglobin
catabolism:
• Haemoglobinemia and haemoglobinuria
• Icterus
Icteric serum when
serum bilirubin levels >20mol/L
Icteric tissues when
serum bilirubin levels >50mol/L

25. HAEMOLYTIC ANAEMIA Red blood cell lysis may occur by two mechanisms:
1. INTRAVASCULAR HAEMOLYSIS
2. EXTRAVASCULAR HAEMOLYSIS

26. INTRAVASCULAR HAEMOLYSIS (causes)
-Parasites/infectious causes
Vascular Endothelial Lesions
Oxidant damage
- Others
Parasites/infectious causes: Babesia, Mycoplasma haemofelis, toxins (Leptospira, Clostridium).
Vascular Endothelial Lesions: haemangiosarcomas, DIC?, splenic torsion, heartworm disease.
Oxidant damage: vegetable, animal toxins and drugs (onions, snake venom, methylene blue, acetaminophen).
Others:poisoning with Cu and Zn, genetic (pyruvate kinase/phosphofructokinase deficiency), severe hypophosphataemia

27. INTRAVASCULAR HAEMOLYSIS (laboratory findings)
In addition to  PCV,
TPP within the reference range or 
and icteric/hemolysed plasma
- Parasites/infectious causes: Blood smears, Serology/PCR
Vascular Endothelial Lesions: Schistocytes in blood smears
- Oxidant damage: Heinz bodies in blood smears

28. Heinz bodies
Schistocyte

29. EXTRAVASCULAR HAEMOLYSIS
-Physiological. (aged erythrocytes) removed by the
macrophage-monocyte system in the spleen
-Pathological. (Auto)antibodies are produced against
“normal” erythrocytes that are phagocytosed by the spleen
- INMUNE-MEDIATED HAEMOLYTIC ANAEMIA

30. INMUNE-MEDIATED HAEMOLYTIC ANAEMIA
- Idiopathic (unknown mechanisms)
- Secondary to:
• Infectious agents
• Drugs/insecticides/vaccines/neonatal isoerythrolysis
CAUSE THE APPEARANCE OF
ABNORMAL ANTIGENS ON THE ERYTHROCYTE
CELL MEMBRANE

31. INMUNE-MEDIATED HAEMOLYTIC ANAEMIA (laboratory findings)
In addition to  PCV,
TPP = within the reference range or  and yellow coloured plasma
Spherocytosis (canine blood)
Autoagglutination
Gross autoagglutination on a slide

32. Spherocytosis
Autoagglutination

33. INMUNE-MEDIATED HAEMOLYTIC ANAEMIA:
ADDITIONAL TESTS TO CHARACTERIZE
INMUNE-MEDIATED HAEMOLYTIC ANAEMIA:
COOMBS TEST
- ERYTHROCYTE FRAGILITY TEST

34. COOMBS TEST Detects antibodies directed at the erythrocyte membrane
Falses +´s: -some chronic infections
- “ parasites (heartworms, haemobartonella)
- “ drugs (trimethoprim-sulfa)
- “ neoplasms
Falses -´s: in some cases of inadequate antibody production
Usually consists of antisera against IgG, IgM and C3 (complement), and detects the presence of these factors on RBC surface. Thrice-washed RBCs from the patient are mixed with antisera and a positive reaction is denoted by marked clumping of RBC.
The test is species-specific

35. ERYTHROCYTE FRAGILITY TEST:BASIS
Whole blood in a hypotonic solution (0.55% NaCl)
Normal RBCs absorb water from the hypotonic solution for osmotic equilibrium and are distended but not haemolyzed
Membranes of fragile RBCs (spherocytes, and those with enzyme deficiencies or damaged by some drugs)
cannot withstand distension and are haemolyzed
Spherocytes are small and dense, and do not have central pallor, so can be easily detected in canine blood smears since normal erythrocytes have central pallor. The erythrocyte fragility test can be a help for detecting spherocytes in species with erythrocytes without central pallor.

36. Anaemia regenerative non regenerative TYPES OF ANAEMIA haemolytic
haemorrhagic
Anaemia
secondary B-M
disorders
B-M (bone-marrow)
non
regenerative
primary B-M
disorders

37. NON-REGENERATIVE ANAEMIA
Characterized by an absence of, or reduction in reticulocyte
response in an anaemic animal.
This will produce:
• Normocytic-normochromic anaemia
MCV and RDW, MCH and MCHC within the reference ranges
• In blood smears with Romanowsky stains:
- absence of polychromasia and anisocytosis

38. NON REGENERATIVE ANAEMIA (causes)
- Primary bone marrow disorders:
some myeloproliferative, lymphoproliferative and myelodisplastic disorders
virus (feline leukaemia/ canine parvovirus)
some drugs: oestrogens, inmunosuppressive agents, non-steroid anti-inflammatories
- Secondary:
chronic inflammatory disease, some endocrine diseases
chronic renal failure with decreased erythropoietin levels
Other causes of primary bone marrow disorders can be mycotoxins and irradiation.

39. NON REGENERATIVE ANAEMIA (laboratory findings)
In addition to  PCV and absent/reduced signs of RBC regeneration (reticulocytes)
- Primary (bone marrow disorders): Diagnosis by bone marrow evaluation + specific tests. Leukopenia and/or thrombocytopenia may also occur
- Secondary: Laboratory findings of the primary disease. (e.g. chronic renal failure:  BUN and creatinine)

40. - RBC loss or destruction has occurred within the previous 4 days
NON REGENERATIVE BLOOD SMEARS MAY BE SEEN IN HAEMORRHAGE OR HAEMOLYSIS IF:
- RBC loss or destruction has occurred within the previous 4 days
- chronic haemorrhage has induced iron deficiency anaemia
- animals with a low reticulocyte response: bovine, and
particularly equine species. In the latter, the only sign that
regeneration is occurring may be a small increase in MCV.
In these cases serial haemograms are highly recommended

41. CLASSIFICATION OF ANAEMIAS
BASED ON RBC INDICES
- Macrocytic-hypochromic (regenerative)
- Normocytic-normochromic (non regenerative)
- Microcytic-hypochromic or normochromic (iron deficiency)
* Macrocytic-hypochromic anaemias are usually produced by the presence of reticulocytes and it is a sign of regeneration. However, there are other causes of macrocytic RBCs which are not associated with regenerative anaemias:
- FeLV
- Vit B12 and folic acid deficiency
- Chemotherapy (eg. With methotrexate)
* Lead intoxication can produce microcytic RBCs and the appearance of nucleated RBCs

42. DIAGNOSIS OF ANAEMIAS: SUGGESTED
APPROACH
The following questions must be addressed:
1. Regenerative or non-regenerative?
2. If regenerative: haemolytic or haemorrhagic?
3. If non-regenerative: primary or secondary bone marrow disorder?