Page 228 - BSAVA Manual of Canine and Feline Head, Neck and Thoracic Surgery, 2nd Edition

Chapter 17 · Surgery of the diaphragm

the diameter of the hiatus is reduced too much, or if a fund - cranial displacement of the liver or caudal displacement of
oplication procedure is performed. Iatrogenic pneumo - the developing lung bud into the canal may prevent its
VetBooks.ir ligament and adequate measures for controlled ventilation may fail to guide the posthepatic mesenchymal plate to
closure. Alternatively, atrophy of the developing lung bud
thorax may follow disruption of the phrenico-oesophageal
fusion (Mann et al., 1991). The facts that the left lung bud
and pleural drainage should be available.
Continued regurgitation or vomiting may be due to
that pleuroperitoneal hernias develop predominantly on
unresolved oesophageal motility disorders, continuing develops more slowly than the right in many species and
gastro-oesophageal reflux, unresolved oesophagitis, mega - the left side appear to support the latter hypothesis (Mann
oesophagus and gastric hypomotility. Gastric hypomo tility et al., 1991).
may be caused by iatrogenic trauma to the ventral vagus
trunk or may be part of generalized gastrointestinal tract Pathophysiology: The pathophysiological events in
hypomotility (Prymak et al., 1989; Callan et al., 1993). animals with sufficiently large defects are similar to those
in animals with traumatic diaphragmatic rupture, with dis-
Prognosis: Surgical management of hiatal hernia using placement and compression of the thoracic viscera by
sphincter-enhancing techniques has a high rate of failure abdominal organs and, less commonly, incarceration of
and frequent complications (Merdan Dhein et al., 1980; abdominal viscera in the thorax. Animals may be dead at
Ellison et al., 1987). Operative mortality can be high, up to birth or die soon after with cyanosis and dyspnoea
64% (Ellison et al., 1987), and success rates are not con- because of an inability to expand the lungs. Organs that
sistently high; for example, in one study only 25% of commonly herniate include the stomach, liver, spleen,
animals were relieved of all clinical signs (Ellison et al., duodenum and pancreas (Feldman et al., 1968). Hernias
1987). However, if surgical closure of the hiatus and fixa- formed by incomplete muscular invasion of the pleuro-
tion of abdominal organs is performed, and if care is taken peritoneal folds have a hernial sac that limits the extent of
to identify and correct predisposing conditions, then the herniated organs, compared with hernias formed by
prognosis is good (Burnie et al., 1989; Prymak et al., 1989; incomplete closure of the pleuroperitoneal canals.
Bright et al., 1990; White, 1993; Hardie et al., 1998;
Lorinson and Bright, 1998). Diagnosis: Puppies or kittens may be born dead or may
exhibit severe dyspnoea and cyanosis. Less severely
affected animals may show mild dyspnoea and abdominal
Pleuroperitoneal hernia
breathing (Feldman et al., 1968; Mann et al., 1991) or no
Anatomy and incidence: This is the least common of the clinical signs (Voges et al., 1997).
congenital diaphragmatic hernias. A defect is present in Radiography reveals a soft tissue opacity at the cranial
the dorsolateral diaphragm, which may range from a lack extent of the diaphragm (Figure 17.10), which may mimic a
of the intermediate part of the left lumbar muscle of the mass lesion affecting the diaphragm, lung lobes or pleura.
crus to absence of both crura and a portion of the central Ultrasonographic examination may reveal an abnormally
tendon (Feldman et al., 1968; Valentine et al., 1988). These thin diaphragm with a hernial defect and abdominal organs
defects do not involve the pericardial sac. passing cranial to the diaphragm (Mann et al., 1991).
Differentiating a pleuroperitoneal hernia from a rup-
Aetiology: Two aetiologies for these hernias are sug- tured diaphragm may be difficult if there is no history of
gested, which explain their dorsolateral location: trauma. This differentiation is relatively simple for com-
plete tears of the diaphragm. However, this may be diffi-
• Incomplete closure of the pleuroperitoneal canals: the cult in the case of a subtotal diaphragmatic tear, in which
pleuroperitoneal folds and posthepatic mesenchymal there is a traumatically induced rent in the musculotendi-
plate fail to fuse with the septum transversum and nous portion of the diaphragm, but the parietal pleura on
dorsal mesentery of the oesophagus, and an opening the thoracic surface of the diaphragm remains intact
(foramen of Bochdalek) persists between the thoracic (Voges et al., 1997). This is sometimes referred to as even-
and abdominal cavities (Feldman et al., 1968; Valentine tration of the diaphragm. In this situation, the abdominal
et al., 1988) organs are bounded by a membrane that mimics the
• Failure of the pleuroperitoneal folds to incorporate hernial sac of the true pleuroperitoneal hernia, although
muscular components of the body wall: the this membrane may be difficult to recognize.
pleuroperitoneal canals are closed, but myoblasts from Criteria used to help differentiate a congenital pleuro-
the posthepatic mesenchymal plate and abdominal peritoneal hernia from a ruptured diaphragm are shown in
wall fail to invade this tissue and the lumbar portion of Figure 17.11.
the diaphragm remains membranous rather than
muscular, and acts as a hernial sac. This type is Treatment: Surgical closure of the hernia may be pos-
referred to as a true pleuroperitoneal hernia (Mann et sible, depending on the size of the defect. However, in
al., 1991; Voges et al., 1997). those animals that survive beyond birth, the hernia is
likely to be relatively small and bounded by a hernial sac.
On the basis of finding the defect in litters from Herniorrhaphy is performed in a similar manner to that
repeated matings, an autosomal recessive mode of inherit- for a ruptured diaphragm (see below), although the pres-
ance has been proposed in the dog (Feldman et al., 1968; ence of the intact pleuroperitoneal membrane in most
Valentine et al., 1988). In humans, the left side of the dia- cases means that there is no direct continuity between
phragm is also more commonly affected and an autosomal the thoracic and abdominal cavities and intraoperative
mode of inheritance is also suspected. These hernias have pneumothorax will not occur unless this membrane is
also been induced by exposure to various teratogens, incised or is absent.
such as thalidomide and polybrominated biphenyls, as
well as by vitamin A deficiency (Mann et al., 1991). Postoperative care and complications: Postoperative
Failure of the pleuroperitoneal membranes to close recovery is usually uncomplicated. Complications have not
may be caused by interference by viscera. For instance, been reported.

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