Abnormalities of the erythron Flashcards
Function of RBCs?
- haemaglobin oxygen carrying capacity
Where are RBCs produced in foetus? In adult?
- liver/spleen in foetus
- bone marrow in neonate
- growing animals = BM of all bones
- red marrow/yellow marrow (femur/humerus) in long bones, flat bones remain active
- liver and spleen maintain erythropoietic capacity, espcially if incresed demand (extramedullary haematopoeisis) as do long bones (reversion to red marrow)
Production requirements for haemopoeisis?
- stem cells
- space in marrow
- Growth factors (IL3, GM-CSF, G-CSF, erythropoeitin)
- Iron
- Cholesterol/lipids for membrane (more humans)
- enzyme pathways for construction and maintainance
Outline the different cell lines as a RBC matures
- Rubriblast (nucleoli, fine granules in nucleus, dark blue cytoplasm)
- Prorubriocyte
- Basophilicrubricyte
- Polychromatophilic rubricyte
- Metarubricyte
- Reticulocyte
What is blue basic dye attracted to?
Acid
How long do RBCs live for?
- 100d (Dog)
- 70d cat
- 150d horse and cattle
How are RBCs removed when too old normally?
- MAJOR ROUTE: macrophage phagocytoses recycles components
- MINOR ROUTE: intravascular haemolysis
What is anaemia? Howo may this be appreciated diagnostically?
> reduction in red cell mass, evidence in decreased:
- [Hgb] conc Haemoglobin
- PCV packed cell volume
- HCT haematocrit
- [RBC] RBC conc
How should PCV, HCT, [Hbg] nd [RBC] values change?
All together - if they change independantly suspect something
What is HCT?
Haematocrit (= PCV)
- calculated by machine
- Relies on RBC count and cell volume (less accurate)
What is [RBC]]
- total red cell numbers
What is [Hbg]?
- total oxygen carrying capacity
What is PCV?
- packed cell volume = % red cells in a volume of blood
- centrifuged whole blood, red cells red as % of column length
What else can be assessed in PCV?
- buffy coat assessment (WBC)
- plasma (clear/straw or pink if hamolysed)
- total protein measurement (put serum into refractometer)
> if bleeding, losing protein, protein v
Different classifications of anaemia?
> mild/mod/severe > regenerative/non-regenerative > normocytic/microcytic/macrocytic > normochromic/hypochromic (hyperchromic artefact) - Haemoglobin * helps to narrow the cause of anaemia *
Define mild anaemia
- normal - 10% decrease PCV
- may not affect animal until excercised
- common in animals with ongstanding dz, endocrine disorders etc.
- will not present for this as main presenting factor
Define moderate anameia
- varies between species, depends on normal PCV of each
- weakness or may be well adapted (takes time)
- mm pallor
- fast bounding pulse
DDefine severe anameia
- PCV low teens and less
- pale, weak, unable to excercise
- may need O2 stabilisation before dxx
> dont fight with severely anaemic cats!
How would hypochromic anaemia appear? Why?
- increased central pallor
- MCHC/MCH (hbg conc)
- decreased in iron deficiency/poor iron incorporation (with microcytosis)
When does hyperchromia occour?
Artefact, cells cannot be hyperchromic
- haemolysis
What is the MCV?
= mean cell volume
- average volume of a single red cell (micro/normo/macrocytic)
Distinguishing features of normocytic
- erythrocytes unremarkable size
- often assoc with mild, non-regnerative anaemia, acute haemmorrhage etc.
Distinguishing features of microcytic?
- RBC haemoglobin conc determines when devision stops
- iron deficiency allows oe more division -> smaller RBC
- eg. seen with PSS, Fe deficiency, hepatic failure
- akitas (congenital, normal cells but smaller, NOT path)
Distinguishing features of macrocytic?
- in regeneration
- polychromatophils larger than mature RBC
- more purple colour too
- we want these as indicate regenerationi (yay)
- some poodles inherited dz (path)
How may macrocytosis affect your dxx?
Can increase PCV as dependant on size of cell as well as number
When is macrocytosis also seen?
- FeLV affected cats
- myelodysplasia
- common artefact in stored (usually posted) blood
What is regenerative anaemia and what stimulates it?
- body response to a fall in oxygenation
- kidneys release EPO -> BM stimulation
- takes 2-3d and younger red cells (polychromatophils/reticulocytes) increase in circulation.
Non regeneratvie
no notes
What are the 2 Ddx for regenerative anaemia?
- haemorrhage (loss)
- haemolysis (destroyed)
> if you can control the loss, animal will get better by itself
> allows assessmeent of how well an anmal is resposing
What cells do you look for as hallmarks of regenerative anaemia?
> reticulocytes - RNA precipitates - new methylene blue - aggregates/reticulum forms > polychromatophils - Diff-Quick/Giemsa - young immature cells containing ribosomal RNA show as large, blue cells (polychromatophils) > these are the SAME CELLS
How do cat reticulocytes differ?
- cat retics released as aggregate retics, mature to punctate retics over time
- retic counts should record AGGREGATE or BOTH (punctates hang around for a while)
How can regenerative v non-regenerative be distignusihed?
- reticulocyte % (1000 red cells counted, retics expressed as %)
- corected % (same no retics will take up more % in a very anaemic animal)
> retic% x patient PCV/normal PCV
[ PCV 45% normal dog, 35% normal cat ]
> regenerative if >1% corrected (Dog) or >0.4% (cat)
> absolute reticulocyte conc may be better ([RBC] x Retic%)
What casues decreased red cell mass?
- ^ loss or v production
Causes of increased losses of RBC
> haemorrhage (external)
- melena
- UT
- epistaxis
- post-trauma/surgery
Shape of RBCs = ? Reason? Exceptions?
- biconcave disk in most species
- central pallor (seenin dogs)
- high surface area to volume ratio -> ^ deformability
> camelids have elliptical RBCs
> anucleate in all animals except birds and reptiles
