Table – Abdominal Effusion (Ascites) Evaluation

Test

Abnormal Result

Interpretation and Comments

AFAST® and Abdominal Fluid Scoring

*AFAST® Negative for Free Fluid

Abdominal Fluid Score (AFS) = 0 *Always Repeat the Exam Post-Resuscitation and Rehydration and Continue as Part of the Physical Exam (Patient Rounds, Recheck Exams)

AFAST® Fluid Scoring Allows Tracking of Ascites

  • Static (same AFS)
  • Worsening (increasing AFS)
  • Improving (decreasing AFS)
  • Resolved (AFS=0)

Note: Must Sample and Test Fluid when Safely Acceptable to Definitively Determine Type of Fluid because Ultrasound Cannot Reliably Characterize Free Fluid based on Echogenicity

*AFAST® Positive for Free Fluid

Small Volume Effusion AFS < 3

Large Volume Effusion AFS ≥ 3

Global FAST® should always be performed to stage the patient as localized versus disseminated disease (TFAST® and Vet BLUE®).

Biochemical Analysis

Hemoabdomen – Packed Cell Volume

PCV ≥ 10-25% peripheral PCV Must spin down sample as PCV as low as 3-5% can appear grossly like blood and in fact it’s blood contamination
Septic Peritonitis – Glucose ≥ 20 mg/dL less than the venous Glucose *Bacteria consume Glucose is a way to remember this test

Do AFAST® and fluid score and sample fluid (abdominocentesis) when safely accessible

Lactate

≥ 2mmol/L greater than the venous Lactate *Bacteria metabolically produce Lactate is a way to remember this test

Do AFAST® and fluid score and sample fluid (abdominocentesis) when safely accessible

Uroabdomen – Creatinine ≥ 2:1 Peritoneal to Venous Blood Urea Nitrogen (BUN) not used because unreliable (small molecule and to freely diffusible)

Do AFAST® and fluid score and sample fluid (abdominocentesis) when safely accessible

Potassium

≥ 1.9:1 (Feline) and ≥ 1.4:1 (Canine) Peritoneal to Venous

Bilioabdomen – Total Bilirubin

≥ 2:1 Peritoneal to Venous Cytology very helpful

Do AFAST® and fluid score and sample fluid (abdominocentesis) when safely accessible

Pancreatitis – Lipase

≥ 4 times the upper reference range OR

≥ 2:1 Peritoneal to Serum

Do AFAST® and fluid score and sample fluid (abdominocentesis) when safely accessible

Patients with Pancreatitis can get Pancreatitis-related Pleural Effusion

Others – Total Protein

< 2.5 g/dL – Transudate plus low Cellularity

≥ 2.5 – 5.0 g/dL – Modified Transudate plus low Cellularity

> 3.0 g/dL – Exudate (Non-septic, Septic) plus high Cellularity

> 3.0 g/dL – Hemorrhagic

> 2.5 g/dL – Neoplastic

Transudate – Pre-hepatic Portal Hypertension (lymph from weeping small intestine), Liver Disease, Low Albumin (< 1.6 g/dl), Vasculitis

Do Global FAST® for any obvious soft tissue abnormalities.

Modified Transudate – Post-hepatic Portal Hypertension (lymph from weeping liver [or less commonly spleen]), Liver Disease, *Right-sided Congestive Heart Failure, Splenic Torsion, Liver Lobe Torsion

Do Global FAST® for TFAST® echocardiography views and AFAST®-TFAST® Diaphragmatico-Hepatic View for a distended caudal vena cava and hepatic veins

Do Global FAST® for any masses, evidence of co-morbidities, that could provide additional helpful information

Do Global FAST® for any masses, evidence of co-morbidities, that could provide additional helpful information

Do Global FAST® for any masses, evidence of co-morbidities, determining if localized versus disseminated disease (Global FAST® Staging) that could provide additional helpful information including possible locations for tissue biopsy

Microscopic Evaluation

Predominant Cell Type

Neutrophils

Lymphoblasts

Red Blood Cells

Small Mature Lymphocytes

Sheets of Cells of ≥ 8-16 cells

Consider Inflammatory disease, Non-septic and Septic (when degenerate, engulfed bacteria, fungal organisms), Chronic hemorrhage when engulfed red blood cells)

Consider Lymphoma

Consider Blood Contamination versus True Hemorrhage (run comparative PCVs)

Consider Chylous (high Triglycerides) and Pseudo-chylous effusion (high Cholesterol and protein-lecithin compounds), both grossly milky white to milky pinkish appearance.

Rule of thumb – Chylous is more common and does NOT clear with centrifugation

Consider Carcinoma/Neoplasia

Bile Pigment

Gold, green, black-brown, free or engulfed in neutrophils, macrophages Consider Bile peritonitis

Intracellular Organisms

Intracellular bacteria, fungal organisms

Extracellular bacteria, fungal organisms

Consider Septic (bacterial, fungal) peritonitis

Consider (bacterial, fungal) contamination from bowel aspirate

*Total Nucleated Cell Count

Mononuclear <1,000/ul – Transudate

Mononuclear 1,000-8,000/ul – Modified Transudate

Neutrophils >3,000/ul – Non-septic Exudate

Neutrophils >3,000/ul – Septic Exudate

Similar to Blood with Variable Counts – Hemorrhagic

Tumor Cells with Variable Counts – Neoplasia

*Combine findings of Cytology with Biochemical analysis
*Cytology has been estimated to vary between 60-80% sensitive for the presence of bacterial septic peritonitis, combine with Glucose and Lactate testing.
References:

Alleman AR, Abdominal, thoracic, and pericardial effusions. The Veterinary Clinics Small Animal Practice 33(2003): 89-118.

Created by Dr. Gregory Lisciandro, DVM, Dipl. ABVP, Dipl. ACVECC of FASTVet.com Copyright 2021

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