Differential Diagnosis of Clinicopathological Abnormalities Flashcards
Anaemia and erythrocytosis
Define anaemia.
Reduced RBC indices:
- RBC
- PCV
- HCT
- Haemoglobin
Define erythrocytosis.
Increased RBC mass/indices including:
- RBC
- PCV
- HCT
- Haemoglobin
What can cause erythrocytosis?
- Relative e.g. dehydration or splenic contraction
- Absolute e.g. polycythaemia vera
What is polycythaemia vera?
Refers to chronic myeloproliferative disease specifically erythroid leukaemia
What can cause hyperviscosity of blood?
- Relative erythrocytosis e.g dehydration
- Absolute e.g. polycynthaemia vera e.g. chronic myeloproliferative disease such erythroid leukaemia
- Hyperproteinaemia
What is the difference between PCV and HCT?
PCV is a measure value from haematocrit tubes whereas HCT is a calculated values, HCT = MCV x RBC, thus is more prone to artifactual or real changes in MCV which are less likely to affect the PCV.
What is the first step in interpretation of HCT or PCV?
Determining whether it is physiological or true.
What is important about interpreting HCT or PCV in Greyhounds?
Given they have a higher HCTs than other breed a HCT <45% would be considered anaemia in this breed.
What are the three main pathophysiologic mechanisms for anaemia?
- Loss
- Destruction/decrease life span
- Lack of production
How can we determine between loss and destruction vs lack of production?
Determining if there is evidence of regeneration. If regeneration is present than the underlying mechanism is loss or destruction.
What are the differentials for haemorrhage?
- Internal e.g. into a body cavity
- External e.g. skin, respiratory, genitourinary, gastrointestinal tract.
- Chronic blood loss which can results in iron deficiency anaemia
What other cbc and biochemistry parameters could support haemorrhage?
Hypoproteinaemia e.g. low albumin and globulins
What are some features of iron deficiency anaemia?
Hypochromasia and RBC fragmentation. Will see microcytic hypochromic non or pre-regenerative anaemia.
Low reticulocyte-haemoglobin concentration - not definitive but supports a diagnosis.
What are the differential for low reticulolcyte haemoglobin concentration?
- Iron deficiency
- Inflammatory disease
- PSS
- Breed associated microcytosis.
What are the types of haemolysis?
- Extravascular - premature phagocytosis by macrophages in spleen, liver and bone marrow
- Extravascular with a component of intravascular - extravascular haemolysis is occuring in all cases of haemolysis but in some cases there will be a component on intravascular haemolysis where RBCs are destroyed in circulation liberating haemoglobin.
How do were determined if there is a component of intravascular haemolysis?
- Haemoglobinaemia
- Haemoglobinuria
- Ghost RBCs , heinz bodies or infectious organisms may also be seen by not relied upon.
What other CBC and biochemistry changes can support haemolysis?
- Normal or high TP
- Elevated TBIL
What are clues to indicate decreased production or a bone marrow problem?
- Severity of anaemia - often a mild to moderate normocytic, normochromic anaemia
- Concurrent cytopaenia particularly neutropaenia and thrombocytopaenia
What are the differentials for haemolysis?
- Immune-mediated which can be associative or non-associative
- Infectious organisms e.g. Babesia, theileria, mycoplasma haemocanis and haemofelis, leptospira
- Oxidant-induced: zinc, onion, acetominophen
- Fragmentation injury (microangioppathic haemolytic anaemia: vasculitis, DIC
- Aberrant macrophage activity: reactive or neoplastic histiocytic disorders
- Inherited defects in the RBC membrane or metabolic pathways
- Severe hypophosphataemia, envenomation
What are the differentials for decreased production Rbcs?
- Inflammatory disease
- Chronic kidney disease e.g. decreased EPO mostly - GI ulceration, haemolysis or inflammation can all contribute
- Endocrine disease e.g. hypoT or hypoadrenocorticism
- Bone marrow disease
- Increased intramedullary cell death e.g. precursor-directed immune-mediated anaemia (PIMA), drugs or hormone e.g. oestrogen, toxins or infectious organisms (erlichia) or histiocytic disorders
- Abnormal production with intramedually cell death e.g. myelodysplastic syndrome or primary myelodysplasia in cats often secondary to FELV
- Destruction or damage to erythroid progenitor cells e.g. PIMA, infectious (parvo or erhlichia), drugs
- Decreased HGB production e.g. iroon deficiency, PSS, lead toxicosis
- Decreased or abnormal DNA production e.g. vit b12 or folate deficiency FeLV
- Cancer e.g. primary such as acute myeloid leukaemia, or infiltrative such as histiocytic sarcoma, multiple myeloma in cats, lymphoma in dogs.
Name the inherited defects in RBCs membrane.
- Stomacytosis in alaskan malamutes
- Spherocytosis in golden retrievers
Name the inherited defects in RBCs metabolic pathways.
- Phosphofructokinase deficiency in dogs
- Pyruvate kinase deficiency in dogs and cats
Describe the pathogenesis of inflammatory disease causing non-regenerative anaemias? Give some differentials.
Inflammatory cytokines supress erythropoiesis , EPO release and response to EPO. It also stimulated hepcidin release, inhibiting iron absorption causes iron sequestration.
DDx include sepsis, IBD, inflammatory liver disease, cancer.