Page 232 - BSAVA Manual of Canine and Feline Head, Neck and Thoracic Surgery, 2nd Edition

Chapter 17 · Surgery of the diaphragm

• Repeat survey radiographs following thoracocentesis Ultrasonographic examination should always be per-
• Positional radiographic views made with a horizontal formed in animals where a diagnosis cannot be made from
VetBooks.ir • Contrast radiographs. the diaphragm) or where a small tear may be suspected
beam
the radiograph (e.g. if pleural effusion obscures the line of
but is not obvious radiographically (e.g. a small tear in the
Repeat survey radiographs: If there is a significant volume
Ultrasonography may not always identify the tear in the
of pleural fluid present, thoracocentesis should be per- diaphragm with incarceration of a single liver lobe).
formed (see Chapter 12). Removal of the fluid will alleviate diaphragm or organs herniating through it, but it will dem-
some of the respiratory distress, allow a sample of the fluid onstrate the presence of abdominal viscera in the pleural
to be submitted for analysis to rule out other causes of space. The liver, spleen and intestines can all be identified
pleural effusion and improve the detail seen on sub- ultrasonographically and their presence in an inappro-
sequent radiographs. However, thoracic radiographs taken priate location, such as adjacent to the heart, indicates a
after thoracocentesis may still not yield a definitive diag- diaphragmatic rupture. Asymmetry of the cranial hepatic
nosis (Sullivan and Lee, 1989). border may be seen. In some cases, the remnants of
the torn diaphragmatic muscle, surrounded by anechoic
Positional radiography and horizontal beam views: Taking pleural fluid, may be seen moving in time with respiratory
radiographs with the animal in different positions (e.g. a movements. However, mirror image artefact, a common
horizontal beam lateral view with the animal in dorsal finding that results in the apparent presence of the liver
recumbency), may help to differentiate solid tissue from cranial to the diaphragm, should not be misinterpreted as
fluid. Solid tissue will usually remain in place, whereas fluid a ruptured diaphragm.
will move to the dependent part of the thorax. However, it
should be stressed that any dyspnoeic patient should not Other diagnostic tests: Arterial blood gas analysis will give
be placed in dorsal recumbency and this is useful only for further information about the effectiveness of ventilation
animals with a small volume of pleural fluid. and gas exchange. Pulse oximetry is a non-invasive tool
Horizontal beam radiography may be required for that will provide information about the saturation of
severely dyspnoeic animals. The patient is allowed to haemoglobin, giving indirect evidence of oxygenation. An
adopt a comfortable sitting or standing position and a electrocardiogram should ideally be performed in all
radiograph is made with a horizontal beam. Cats may be patients to rule out cardiac arrhythmias due to myocardial
placed inside a cardboard box on the radiography table contusions or hypoxia.
to provide minimal restraint. However, this view is not
standard, so may be difficult to interpret; positioning is Clinical pathology: In acute cases, there may be little
poor, with the forelimbs often obscuring the thoracic change in routine blood screens. With liver entrapment in
cavity, and it requires the use of a horizontal X-ray beam, the rupture, elevations in serum alanine aminotransferase
for which appropriate radiographic safety procedures and alkaline phosphatase may be noted.
should be followed.
Treatment:
Contrast radiographs: Various contrast radiographic tech- Preoperative stabilization: Rupture of the diaphragm is a
niques, such as an upper gastrointestinal barium series, surgical disease. However, because of the numerous and
peritoneography (negative and positive contrast), positive potentially life-threatening pathophysiological changes, the
contrast pleurography, portography, cholecystography and patient should be stabilized prior to anaesthesia for defini-
angiography, have been suggested, although only the first tive repair. This will allow an accurate assessment of the
two techniques are recommended. The use of ultrasono- severity of the other injuries, and stabilization and treat-
graphy has replaced these techniques and they are only ment of them. If the surgery is carried out too soon, the
indicated if thoracic radiography is equivocal and ultra- patient may succumb to other disease processes (e.g. pul-
sonography is not available. monary oedema). However, if the surgery is delayed the
An upper gastrointestinal barium series, following the pathophysiological changes may become worse (e.g.
administration of 2–4 ml/kg 30% w/v barium sulphate sus- worsening atelectasis) and adhesions may start to form
pension, is relatively simple to perform and non-invasive, between the herniated organs and the contents of the
but it will only allow a definitive diagnosis to be made if thoracic cavity, thus making reduction of the organs more
part of the gastrointestinal tract has herniated through the difficult. Surgical repair within the first 24 hours following
diaphragm (Sullivan and Lee, 1989). Obstruction of the trauma has been reported to have the highest mortality
intestinal tract may delay passage of barium and is a rate (33%) (Boudrieau and Muir, 1987), but this finding was
further disadvantage. Peritoneography is more invasive not supported by a more recent study where the survival
and may yield false negative results if the rent in the dia- rate was 89.7% (Gibson et al., 2005). It is likely that appro-
phragm has been sealed by viscera. The use of positive priate patient assessment and stabilization are more
contrast agents (e.g. 1 ml/kg water-soluble iodinated con- important than time per se, and some patients with acute
trast medium) rather than air is more sensitive, although life-threatening dyspnoea will benefit from early surgery.
dilution of the medium by pleural fluid may also yield false Supplementary oxygen therapy should be provided
negative results (Stickle, 1984). during the evaluation and initial stabilization of the patient.
The need for longer-term therapy can be decided once the
Ultrasonography: Ultrasound examination is a relatively patient is stable. This may be provided simply by flow-by,
simple, non-invasive, accurate technique for the diagnosis facemask or nasal catheter (see Chapter 2). Intravenous
of diaphragmatic rupture (Spattini et al., 2003), which still fluid therapy is indicated for patients that are hypovolae-
works well in the presence of pleural fluid. The examination mic, in circulatory shock or unlikely to maintain their own
is performed with the probe in a subcostal position, imme- voluntary intake. This generally includes all patients follow-
diately caudal to the xiphisternum, or in a parasternal loca- ing trauma, but care should be taken to avoid volume over-
tion, below the costochondral junctions, in an intercostal load in patients with pre-existing lung contusions so as
space selected after evaluation of the thoracic radiograph. not to exacerbate pulmonary dysfunction. As previously

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