Page 170 - BSAVA Manual of Canine and Feline Head, Neck and Thoracic Surgery, 2nd Edition

Chapter 12 · Pleural drainage techniques

window, enhancing the visualization of intrathoracic struc- Transudates: These are the result of a disturbance in the
tures. Ultrasonography requires minimal restraint and is overall balance of hydrostatic and colloid osmotic forces
VetBooks.ir sate during positioning for radiography. Ultrasonography pleural space. A major cause of a true transudate is
governing the formation and absorption of fluid in the
particularly useful for patients that are likely to decompen-
can be used to guide thoracocentesis, as well as aspiration
hypoalbuminaemia that results in a decreased intravas-
of an underlying intrathoracic mass or pericardial effusion.
CT, as for pneumothorax, is extremely useful for inves- cular oncotic pressure. Usually the albumin level must be
<0.15 g/l to result in transudation (Hackett, 1999). Hypo-
tigation of the underlying aetiology, staging neoplasia and/ albuminaemia may be caused by a protein-losing enter-
or informing the surgical plan. opathy or nephropathy, hepatic disease or marked loss of
inflammatory fluid through a wound or into a body cavity.
Types and causes Animals with hypoalbuminaemia may also have ascites or
subcutaneous oedema.
Pleural effusions are classified into categories based on Cardiac disease can affect the formation and absorp-
the gross appearance, protein content, specific gravity, tion of fluid in the pleural space by altering pulmonary and
total nucleated cell count, cytological characteristics of the systemic capillary pressures. Systemic venous hyperten-
cells and culture results (see the BSAVA Manual of Canine sion resulting from right-sided or bilateral congestive heart
and Feline Clinical Pathology). Pleural fluid should be sub- failure may result in accumulation of pleural transudate
mitted for both aerobic and anaerobic culture. Analysis of
biochemical parameters, such as levels of triglyceride and and is accompanied by other signs of cardiac disease.
Lung lobe torsion or a diaphragmatic rupture (see
cholesterol, is also indicated if the effusion is suspected to
be chylous. These categories give a useful indication of Chapter 17) can obstruct venous and lymphatic drainage,
possible aetiologies for the effusion, although in practice resulting in leakage of variable types of fluid through the
there is considerable overlap (Figure 12.5). organ capsule into the pleural space. Lung lobe torsion is
A wide range of diseases may be associated with not common in dogs, although Afghan Hounds and Pugs
pleural effusions. In dogs with pleural and mediastinal appear to be predisposed. Lung lobe torsion may occur
effusions, the most common underlying disease identified as a primary entity, particularly in deep-chested dogs,
was pyothorax (Mellanby et al., 2002). Other common con- but may also occur secondarily in any animal with a
ditions included idiopathic pericardial effusion, cranial pleural effusion. Therefore, it may be difficult to determine
mediastinal mass, idiopathic chylothorax, secondary lung whether the pleural effusion or the lung lobe torsion
metastases and dilated cardiomyopathy. In cats, the most occurred first. Other underlying causes for the pleural
common underlying diseases associated with pleural effu- effusion should be ruled out. Lung lobe torsion has been
sions have been suggested to be pyothorax, mediastinal associated with trauma, chylothorax, pulmonary neo-
lymphoma, hypertrophic cardiomyopathy and feline infec- plasia, respiratory disease and thoracic surgery. The right
tious peritonitis (FIP) (Davies and Forrester, 1996). middle lung lobe and the right cranial lung lobe are most
The presence of a peritoneal effusion in conjunction frequently affected. Radiography after pleural drainage
with a pleural effusion is relatively rare. In a study that usually reveals diffuse consolidation of a lung lobe and
looked at aspects of simultaneous pleural and peritoneal possibly altered orien tation or abrupt termination of the
effusions in 48 cases, the presence of a double effusion, lobar bronchi. Complete lobectomy of the involved lobe
irrespective of the underlying disease condition, indicated is indicated and the pedicle is clamped before the lobe is
a poor prognosis and was associated with a greater risk of untwisted (see Chapter 14). The prognosis for dogs with
death when compared with a similar condition without a lung lobe torsion following surgery is fair to guarded
double effusion (Steyn and Wittum, 1993). (Neath et al., 2000).
Effusion Gross appearance Protein Total nucleated Cell cytology Possible aetiologies
category content (g/l) cell count (x 10 /l)
9
Transudate Colourless or very <10 <1 Mesothelial cells, macrophages, Hypoalbuminaemia, heart failure
pale yellow lymphocytes
odified Clear or slightly <30 <5 Mesothelial cells, macrophages, Right-sided heart disease, lung lobe
transudate turbid; yellow/pink lymphocytes, non-degenerate torsion, diaphragmatic rupture,
to orange/reddish neutrophils neoplasia
Non-septic Clear or turbid; >30 >25 Mesothelial cells, macrophages, Feline infectious peritonitis,
exudate yellow to orange/ lymphocytes, neutrophils neoplasia, diaphragmatic rupture,
reddish lung lobe torsion
Septic exudate Turbid, granular; >30 >50 Degenerate neutrophils with Pyothorax
yellow/orange to intracellular bacteria,
brown/green; may macrophages, mesothelial cells
be foul smelling
Neoplastic Variable 30–80 Variable Possible exfoliated neoplastic Primary and metastatic thoracic
cells, mesothelial cells, neoplasia
macrophages, neutrophils
Haemorrhagic Dark red blood 40–80 >3 Red blood cells, white blood cells Trauma, coagulopathy, lung lobe
(similar to peripheral blood) torsion, neoplasia
Chylous Milky/opaque; 30–85 Variable Small lymphocytes, ± non- Chylothorax (idiopathic or associated
white or pink degenerate neutrophils, with trauma, neoplasia, heart disease,
macrophages vena cava thrombosis, lung lobe
torsion)

12.5 Common causes of pleural effusions in dogs and cats categori ed by fluid characteristics.

161

Ch12 HNT.indd 161 31/08/2018 12:07