Page 229 - BSAVA Manual of Canine and Feline Head, Neck and Thoracic Surgery, 2nd Edition

BSAVA Manual of Canine and Feline Head, Neck and Thoracic Surgery

by patent pleuroperitoneal canals (Feldman et al., 1968;
Valentine et al., 1988). Those animals that survived beyond a
VetBooks.ir membrane limiting herniation of organs into the thoracic
few months with a pleuroperitoneal hernia had a mesothelial
cavity and surgical closure was successful (Mann et al.,
1991; Auger and Riley, 1997; Voges et al., 1997).

Acquired diseases
Ruptured diaphragm
Anatomy and incidence: Traumatic rupture of the dia-
phragm is the most common cause of herniation of abdom-
inal organs into the thoracic cavity, representing 77–85% of
all cases of herniation (Wilson et al., 1971; Wilson and
Hayes, 1986; Boudrieau and Muir, 1987). Young male
(a) animals (1–3 years old) are at increased risk for ruptured
diaphragm (Stokhof, 1986; Boudrieau and Muir, 1987).
Knowledge of the anatomical structure of the dia-
phragm helps the clinician understand the common loca-
tions of rupture. The weak ventrally located costal muscles
are more frequently injured than the stronger central
tendon and the large, well protected dorsal lumbar portion
(Wilson and Hayes, 1986). Although some studies have
shown a predominance of tears on the left or the right
side, overall the incidence is probably equal. A single tear
is present in most affected animals, but approximately
15% of individuals have either bilateral or multiple tears
(Garson et al., 1980; Stokhof, 1986; Wilson and Hayes,
1986). In dogs, the orientation of tears was circumferential
in 40%, radial in 40% and a combination of these in the
remaining 20%, whereas in cats the majority were circum-
ferential (59%), with fewer radial tears (18%) in one study
(b)
(Garson et al., 1980).
True pleuroperitoneal hernia. (a) Lateral view of the thorax.
17.10 The cardiac silhouette is ill-defined ventrally and the trachea is
elevated. The caudal sternebrae are fused. (b) Lateral view of the thorax Aetiology: Ruptured diaphragm is caused by blunt
following positive contrast peritoneography. Contrast medium outlines abdominal trauma, primarily from road traffic accidents,
the cranial extent of the parietal peritoneum, which extends into the although kicks, falls and fights have also been impli -
thorax and contains loops of intestine. cated (Walker and Hall, 1965; Wilson and Hayes, 1986;
(Courtesy of C Lamb) Boudrieau and Muir, 1987). Direct trauma from penetra-
ting injuries (e.g. stab wounds and gunshot wounds)
Criterion Congenital hernia Acquired rupture is occasionally seen. Iatrogenic diaphragmatic injury
Appearance of the Round, smooth border Irregular border caused by inadvertent incision during cranial extension of
opening a midline laparotomy, or during placement of a thora-
costomy tube, and cutaneous asthenia are also rare but
Association with Other congenital Other congenital
other abnormalities anomalies possible anomalies unlikely possible causes.
Indirect trauma when the glottis is open is the most
Extent of herniation Large volume of viscera Volume of viscera common cause of diaphragmatic rupture. During normal
and size of defect through a small defect tends to
approximate size of inspiration, the pleuroperitoneal pressure gradient varies
defect from 7 to 20 cmH 2O, but may increase to over 100 cmH 2O
at peak inspiration. Application of force to the abdomen
Histological Lack of inflammation Inflammatory
examination of changes with the glottis open increases this gradient further,
hernial ring which may lead to rupture of the diaphragm. If the glottis
Hernial sac Present in true Absent is closed, the intrathoracic pressure is higher, the pleuro-
pleuroperitoneal hernia peritoneal gradient is lower, and rupture of the lung
parenchyma, rather than the diaphragm, is the most
Completeness of Portions of diaphragm Diaphragm
diaphragm absent complete, but torn likely sequel.
Although blunt indirect trauma is well recognized as a
Age of animal Generally young animals Any age cause of ruptured diaphragm, it must be considered that
Criteria used to help differentiate a congenital any trauma sufficient to cause rupture of the diaphragm
17.11 pleuroperitoneal hernia from a ruptured diaphragm.
(Kent, 1950) will also result in damage to other thoracic and abdominal
organs. In fact, following blunt trauma, such as a road
traffic accident, ruptured diaphragm is considerably less
Prognosis: The prognosis depends on the size and nature common than other injuries, such as rib fractures, pulmo-
of the defect, the degree of visceral displacement and the nary contusions, pleural disease (e.g. haemothorax, pneu-
ability of the lungs to expand. All animals with a pleuro- mothorax) and myocardial contusions. Approximately 2%
peritoneal hernia that were dead at birth or were eutha- of dogs with long bone fractures have a concomitant
nased because of severe dyspnoea had a hernia manifested ruptured diaphragm.

220

Ch17 HNT.indd 220 31/08/2018 13:45