Page 389 - Small Animal Internal Medicine, 6th Edition

CHAPTER 23 Clinical Manifestations and Diagnostic Tests of Pleural Cavity and Mediastinal Disease 361

TABLE 23.1
VetBooks.ir Diagnostic Approach in Dogs and Cats With Pleural Effusion Based on Fluid Type

FLUID TYPE
DIAGNOSTIC TESTS
COMMON DISEASE
Pure and modified Right-sided heart failure Evaluate pulses, auscultation, ECG, thor rad, echo
transudates Pericardial disease See right-sided heart failure
Hypoalbuminemia Serum albumin concentrations
(pure transudate)
Neoplasia Thor rad and US, CT, thoracoscopy, thoracotomy
Diaphragmatic hernia Thor rad and US
Nonseptic exudates Feline infectious Pleural fluid cytology is generally sufficient. In questionable cases
peritonitis (FIP) many tests are available, but none has shown good specificity for
diagnosing FIP. Consider systemic evaluation, ophthalmoscopic
examination, serum or fluid electrophoresis, coronavirus antibody
titer, PCR of tissues or effusion (see Chapter 96)
Neoplasia See Neoplasia above
Diaphragmatic hernia See Diaphragmatic hernia above
Lung lobe torsion Thor rad and US, bronchoscopy, thoracotomy
Septic exudates Pyothorax Gram staining, aerobic and anaerobic cultures, serial thor rad
Chylous effusion Chylothorax See Box 24.1
Hemorrhagic effusion Trauma History
Bleeding disorder Systemic examination, coagulation tests (ACT, PT, PTT), platelet
count
Neoplasia See Neoplasia above
Lung lobe torsion See Lung lobe torsion above

ACT, Activated clotting time; CT, computed tomography; ECG, electrocardiography; echo, echocardiography; PCR, polymerase chain
reaction; PT, prothrombin time; PTT, partial thromboplastin time; thor rad, thoracic radiography; US, ultrasonography.

Chest tube (thoracostomy tube) placement is indicated organisms or abnormal or unexpected cell populations. In
primarily for the treatment of patients with progressive addition to the inflammatory cell types included in each
pneumothorax or pyothorax. However, fluid obtained from cytologic category described in subsequent sections of this
chest tubes is used for therapeutic monitoring, and a descrip- chapter, mesothelial cells are generally present and are often
tion of chest tube placement and management appears at the reactive.
end of this chapter.
Thoracic computed tomography (CT) is indicated in TRANSUDATES AND MODIFIED
patients with pleural or mediastinal disease without a diag- TRANSUDATES
nosis after routine imaging and cytologic analysis of fluid or Pure transudates are fluids with low protein concentrations
masses. Thoracoscopy and/or thoracotomy may be necessary of less than 2.5 to 3 g/dL and low nucleated cell counts of
to obtain a diagnosis in challenging cases. less than 500 to 1000/µL. The primary cell types are mono-
nuclear cells, composed of macrophages, lymphocytes, and
mesothelial cells. Modified transudates have a slightly higher
DIAGNOSTIC APPROACH FOR protein concentration of up to 3.5 g/dL and nucleated cell
PLEURAL EFFUSIONS BASED counts of up to 5000/µL. Primary cell types include neutro-
ON FLUID CYTOLOGY phils and mononuclear cells.
Transudates and modified transudates are formed as a
Pleural fluid is classified as a transudate, a modified transu- result of increased hydrostatic pressure, decreased plasma
date, or an exudate on the basis of protein concentration and oncotic pressure, or lymphatic obstruction. Increased hydro-
nucleated cell count. Further classification of fluid may be static pressure occurs in association with right-sided conges-
possible on the basis of other cytologic or biochemical fea- tive heart failure or pericardial disease. Physical examination
tures. Additional clinically useful fluid categories include findings such as abnormal jugular pulses, gallop rhythms,
septic exudate, chylous effusion, hemorrhagic effusion, and arrhythmias, or murmurs support a diagnosis of heart
effusion caused by neoplasia. Although various types of fluid disease. Heart sounds may be muffled in animals with peri-
have a typical gross appearance (Fig. 23.1), reliance on gross cardial effusion. Thoracic radiography (after fluid removal),
appearance alone will lead in some cases to the misclassifica- electrocardiography, and echocardiography are indicated for
tion of fluid and missed diagnoses through failure to identify cardiac evaluation (see Chapter 2).