Cytology Lab – Fluid and Bone Marrow

Question 1

Purple top (EDTA)

Answer 1

• Cytology
• Protein
• Cell count

Question 2

Red top (no anticoagulant)

Answer 2

• Culture
• Biochem analysis

Question 3

What are the 6 main pathophysiological mechanisms?

Answer 3

• Transudation
• Exudation
• Compromised lymphatic drainage or integrity
• Haemorrhage
• Ruptured viscus
• Neoplasia

Question 4

Exudative effusions

Answer 4

• Increased vascular or mesothelial permeability from inflammation
• Can be infectious: bacterial, fungal, viral
• Can be non-infectious: foreign body, ischemia, necrotic tumor, bile or urine peritonitis
• Often see REACTIVE mesothelial cells among the inflammatory cells
  o Neutrophils predominate
  o May be degenerate in septic exudates due to bacterial toxins
  o May see macrophages with leukophagis

Question 5

Feline infectious peritonitis

Answer 5

• Cytology is supportive but NOT pathognomonic
• Expect very HIGH protein, LOW cell count
  o Technically an exudate, but calls into transudate, protein-rich category
  o Protein often >40g/L
• Cells: neutrophils, macrophages or mixed
  o +/- lymphocytes and plasma cells
  o Important to rule out sepsis and neoplasia

Question 6

What additional testing can you do for FIP?

Answer 6

• PCR for FCoV on fluid sample
• A:G ratio on fluid (<0.4=FIP moderately more likely)
• Histology + IHC is a GOLD STANDARD
• Serology is not helpful

Question 7

Hemorrhagic effusion

Answer 7

• Hemorrhage is primary cause of effusion
  o Ex. hemostatic disorder, trauma, ruptured hemangiosarcoma
• Need to rule OUT blood contamination during collection
• Features of TRUE (pathologic) hemorrhage
  o Sample uniformly red during collection
  o Lack of clottin in red-top tube
  o Lack of platelets
  o Erythrophagia (acute hemorrhage)
   Can occur within 2 hrs of samples stored in tube (always make fresh smears!)
  o Hemosiderin or hematoidin (chronic hemorrhage)

Question 8

Uroabdomen

Answer 8

• Initially, low to moderate cell count, LOW protein
  o Urine dilutes protein concentration
• Eventually: urine will elicit an INFLAMMATORY (exudative) response
  o Moderate cell count, low to moderate protein concentration
• Confirm by measuring creatinine
  o Fluid creatinine >2x serum creatinine

Question 9

Chylous effusion

Answer 9

• Leakage of lymph into a body cavity
• Characteristic “MILKY” appearance
  o High in CMs and TGs
  o Fluid may not be opaque in anorexic animals

Question 10

Chylous effusion: what predominates?

Answer 10

• Small lymphocytes
• +/- highly vacuolated macrophages (lipid ingestion)
• Often many fine clear (lipid) vacuoles in background
• Can induce inflammation: may see low numbers of inflammatory cells

Question 11

How do you confirm chylous effusion?

Answer 11

• Measure TGs
• Fluid TGs >2 times serum TGs
• Fluid cholesterol:TG ratio of <1
• NOT helpful in anorexic animals

Question 12

Bile peritonitis

Answer 12

• Turbid, yellow-brown to greenish fluid
• Bile: yellow-brown amorphous material in macrophages and background
  o May see “white bile” (pale blue amorphous material
• Bile is high inflammatory=neutrophilic ‘EXUDATE’

Question 13

How do you confirm bile peritonitis?

Answer 13

• Confirm by measuring bilirubin
  o Fluid bilirubin >2x serum bilirubin

Question 14

Neoplastic effusions

Answer 14

• Can be associated with any fluid type
  o Compression of lymphatics: chylous fluid
  o Venous compression causing hypertension: transudate
  o Blood vessel erosion, rupture of vascular tumor: hemorrhagic
  o Cytokine production by tumor: exudate
• May or may NOT see neoplastic cells
  o Lymphomas and carcinomas are more likely to exfoliate into EFFUSION
• Beware: carcinoma cells and reactive mesothelial cells can be difficult to tell apart

Question 15

Why evaluate the bone marrow?

Answer 15

• Evaluate hematopoietic system
• Persistent cytopenias
  o Non-regenerative anemia, neutropenia, thrombocytopenia
• Unexplained increase in cell numbers
• Abnormal blood cell morphology
• Neoplasia
• Fe stores, increased Ca, increased globulins
• Infectious disease, FUO, weight loss

Question 16

Bone marrow: ‘procedure’

Answer 16

• Low risk
• Technically not difficult
• Can be done in practice

Question 17

Microscopic evaluation: low power 10x

Answer 17

• Smear quality
  o Presence of particles
• Cellularity of particles
  o 25-75% cellularity=normal
• Megakaryocytes
• Iron stores
  o NOT visible in normal cat (does not stain)

Question 18

Microscopic evaluation: high power 50x

Answer 18

• M:E ratio
• Orderly maturation

Question 19

M:E ratio

Answer 19

• Ratio of myeloid (granulocytic cells) to nucleated erythroid cells
• Reflects “priorities” of bone marrow
• Normal: 1:1 to 2:1 (equal numbers or about 2x as many myeloid cells as erythroid cells
• Ex. animal with inflammatory disease= increased M:E ratio=granulocytic hyperplasia
  o Granulocytic hyperplasia OR erythroid hypoplasia?
• NEED CBC for proper interpretation

Question 20

What are some examples of NOT orderly maturation?

Answer 20

• Increased blasts=leukemia
• Decreased mature cells=maturation arrest
  o Ex. immune-mediated destruction of precursors
  o Ex. non-regenerative anemia
• Dysplastic features (ex. myelodysplasia usually precedes neoplasia)