Fine-needle aspirate in Cats (Felis) | Vetlexicon
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Fine-needle aspirate

ISSN 2398-2950

Contributor(s) :


Synonym(s): FNA

Introduction

  • Diagnosis of superficial masses and enlarged lymph nodes by cytologic evaluation.

Uses

  • Diagnosis of lymphadenopathy.
  • Evaluation of superficial masses.
  • Evaluation of intracavity masses.

Advantages

  • Simple.
  • Can be performed on conscious unsedated patient.
  • Often yields definitive diagnosis.

Disadvantages

  • Aspiration of intracavity masses may need to be guided by ultrasound, but can be done blindly on a palpable mass.

Alternative techniques

  • Biopsy   →   punch core/wedge/tru-cut/jamshidi.

Time required

Preparation

  • 1 minute.

Procedure

  • 5 minutes - longer if more than one mass is sampled.

Decision taking

Criteria for choosing test

  • Enlarged nodes or superficial masses.

Requirements

Materials required

Minimum consumables

  • 1-1.5 inch, 20-22G needle.
  • 5 ml syringe.
  • Glass slides.

Preparation

Site preparation

  • If multiple enlarged lymph nodes, choose one which is medium sized.
    Avoid submandibular and popliteal nodes where possible.
  • Do not need to prepare skin aseptically.
  • For intracavity masses, aseptic preparation of site of entry.
  • Very big mesenteric or iliac lymph nodes can be aspirated transabdominally.

Restraint

  • Minimal restraint of patient in position to provide easy access to mass.

Technique

Approach

Step 1 - Insert the needle and aspirate sample

  • Immobilize the mass with one hand.

Step 2 -

  • Insert the needle until it is embedded in the mass.

Step 3 -

  • Apply suction (at least 2-4 ml), then redirect needle and reapply suction. Repeat this several times.

Step 4 -

  • Release pressure before removing needle.

Exit

Step 1 - Sample handling

  • There is usually little material visible in the hub of the needle.
  • Remove syringe, fill it with air, then reattach needle.

Step 2 -

  • Expel material from needle with gentle pressure onto several glass slides.

Step 3 -

  • Squash (gently press with clean slide and smear) material with a clean glass slide and then allow to air dry before sending to laboratory .

Step 4 -

  • May stain one slide.

Step 5 - Alternative procedure (needle only)

  • Enter mass through skin with needle.
  • Staying under skin, push needle firmly and rapidly into mass 4-6 times.
  • Withdraw needle. Attach syringe and expel onto slide as stated previously.

Aftercare

Outcomes

Reasons for treatment failure

  • Did not hit mass - if poor yield, try again.
  • Mass may be too advanced in disease to yield evidence of active pathology (necrosis in large mass).
  • Inadequate suction applied.
  • Maintenance of suction during needle withdrawal could have pulled specimen into syringe.
  • Crush artifact can complicate interpretation, especially lymph node aspirates.
  • Lymphoma in cat's lymph nodes may be over-interpreted by cytology.
    Lymph node histopathology recommended.

Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • McCullough S, Brinson J (1999) Collection and interpretation of respiratory cytology. Clin Tech Small Anim Pract 14 (4), 220-6 PubMed.