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https://t.me/med1917
19
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Pulmonary hydatid cysts
ANDRES VARELA MD, PhD
Professor, Department of Surgery, Autonomous University of Madrid; Section Chief of Thoracic Surgery and Lung Transplantation,
Department of Cardiovascular and Thoracic Surgery, Hospital Puerta de Hierro, Madrid, Spain
RAUL BURGOS MD, PhD
Associate Professor, Autonomous University of Madrid, Department of Cardiovascular and Thoracic Surgery, Hospital Puerta de Hierro,
Madrid, Spain
EVARISTO CASTEDO MD, PhD
Professor of Surgery, Autonomous University of Madrid, Department of Cardiovascular and Thoracic Surgery, Hospital Puerta de Hierro,
Madrid, Spain
HISTORY
Hydatid disease, which was known in medicine in the times
of Hippocrates, was described by Goze in 1782. This disease is
thought to have been brought to Europe by dogs accompanying whaling boats in the eighteenth century. Echinococcosis is
endemic to the Mediterranean region, South America,
Australia, New Zealand, the Middle East, Alaska, and Canada,
where it is widespread among Indian tribes. In the adult stage,
the parasite lives in the intestinal tracts of carnivores.
Humans contract the disease from contaminated water or
food or by direct contact with dogs. Once the eggs reach the
stomach, the hexacanth embryos are released. They pass
through the intestinal wall and reach the tributary veins of the
liver, where they undergo a vesicular transformation and
develop into the hydatid. Hexacanth embryos can reach the
thorax, mainly after passing through the portal system. The
lymphatic system or bronchi can also serve as the pathway for
infestation, although this route is less common. Within the
thorax, the lung is the organ most frequently colonized. If
parasites advance beyond the lung, they may reach any organ,
carried by the bloodstream.
196 Pulmonary hydatid cysts
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PRINCIPLES AND JUSTIFICATION
Surgery, when feasible, is the principal definitive method
1
of treatment of hydatid disease. The objective of surgical
treatment is to eradicate the parasite, to prevent the intraoperative rupture of the cyst with subsequent dissemination of
its contents, and to remove the residual cavity.
Planning of the surgical technique is based on a good
knowledge of the anatomical relations of the cyst with vascular and bronchial elements. Three topographical regions
must be differentiated:
A
B
• External layer (fibrous whitish aspect) (Part A)
• Medium layer (lung parenchyma with small vessels close
to the pericystic membrane) (Part B)
• Internal layer (bronchial openings and vessels close to the
pericystic membrane) (Part C)
The treatment of choice is to completely eradicate the parasite
while preserving the lung parenchyma.
Small and medium-sized cysts (up to 4–5 cm) are best
treated by enucleation and partial resection of the pericystic
layer. Giant cysts and those at risk of rupture may be treated
with needle aspiration or a trocar-suction device.
PREOPERATIVE ASSESSMENT AND
PREPARATION
Imaging studies
Because a period of 5–20 years often elapses before cysts
enlarge sufficiently to become symptomatic, they are frequently detected incidentally on a routine radiograph or
ultrasonographic scan.
C
1
The finding of a cystic tumor in the chest radiograph of a
patient in good clinical condition who comes from an area
where the disease is endemic, has been in contact with dogs,
or has eosinophilia strongly suggests the diagnosis of pulmonary hydatidosis. In fact, the combination of a positive
finding on chest radiograph and a suggestive clinical history
has a sensitivity of 95% in our series.
On a plain chest radiograph, intact pulmonary cysts
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2a
masses, of uniform density, and with a perfectly defined margin. Ruptured or complicated cysts, however, may have the
membrane floating in fluid resembling the water-lily sign, an
incarcerated membrane folded back in the form of a barricade. Evidence of cyst wall calcification, pneumothorax,
empyema, pleural effusion, pneumonitis, or atelectasis also
may be found.
are usually defined as round or oval-shaped irregular
Preoperative assessment and preparation 197
2a
Ultrasonography, computed tomography (CT), and
2b
defined cysts with thick or thin walls, which may contain
fragments of the hydatid membrane. Repeated evaluation of
cysts by CT and magnetic resonance imaging is also especially
useful in evaluation of the response to treatment. Differential
diagnosis should be made with pulmonary carcinoma,
sarcomas, or tuberculosis.
recommended, because of the risk of cyst rupture and fluid
leakage, which results in either dissemination of infection or
anaphylactic reaction.
magnetic resonance imaging usually reveal well-
CT-guided aspiration of hydatid cysts for diagnosis is not
2b
198 Pulmonary hydatid cysts
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Serological tests
A specific diagnosis can be made by serological assays,
although a negative test result does not exclude the diagnosis
of hydatidosis. Cysts in the liver elicit positive antibody
responses in 85% of infected individuals, but up to 50% of
patients with lung cysts may have negative serological results,
especially if the cysts are not ruptured. The Casoni test has a
high sensitivity but a poor specificity. Immunoblotting has
the highest specificity, although false-positive findings may be
obtained in cases of cysticercosis. Indirect hemagglutination,
indirect immunofluorescence, and enzyme immunoassay
also may be used. Results of serodiagnostic assays usually
become negative in a mean interval of 2 years after surgical
cyst removal.
Definitive diagnosis
Definitive diagnosis can be established either after surgery,
when scolices or daughter cysts are detected in the subsequent histopathological study, or preoperatively, with the
examination of sputum, feces, or urine if a rupture of the cyst
has occurred. Scolices can be demonstrated with a ZiehlNeelsen stain.
ANESTHESIA
General anesthesia is always required. Valsalva maneuvers or
cough must be avoided during induction to reduce the risk of
cyst rupture. Use of a double-lumen endotracheal tube is
mandatory to prevent dissemination. Caution should be
taken to prevent anaphylactic reaction or shock.
OPERATION
Unilateral cysts
For simple or multiple unilateral cysts, a sparing muscle thoracotomy incision is used. In appropriate patients with
uncomplicated pulmonary hydatid cysts, a surgical approach
via minithoracotomy with the help of video-assisted thoracoscopy may be a possibility. Selective unilateral lung ventilation is begun. Protection of the operative field and
surrounding tissues is accomplished with surgical sponges
soaked in 3% hypertonic saline solution.
ENUCLEATION
Small or medium-sized cysts up to 4–5 cm in diameter and
those close to the surface of the lung can be treated by enucleation.
Almost always the cyst is visible on the lung
3a, b
sion in the lung parenchyma encircles the area with care so
that the pericystic membranes are spared. The dissection
between the lung parenchyma and the pericystic membrane
involves small vessels and bronchi that must be carefully
ligated (Figure 3b).
surface as a white protruding area. The inci-
A
A
B
3a
3b
The pericystic membrane may
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3c, d, e, f
neously rather than incised with scissors. Blunt forceps are
used to hold open the pericystic membrane, but herniation of
the cyst is avoided. Dissection of the cyst is completed digitally. Tension on the pericystic membrane is reduced by making star-like incisions.
sometimes be opened sponta-
Cyst
Operation 199
3c
3d
3e
3f
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Thereafter, the cyst is evacuated by cupping of
3g, h
topography of the lesion permits.
the hands or by direct enucleation if the
3g
With small cysts, total resection with the pericystic
3i
membrane is a better alternative.
3h
3i
ASPIRATION OF THE CYST
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In our experience, giant cysts (larger than 5 cm) or
4a
by needle aspiration or by use of a trocar-suction device. The
use of the latter instrument prevents the rupture of the cyst,
eradicates the parasite, and makes it possible to excise the
residual cavity.
cysts in a location at risk of rupture are best treated
Operation 201
4a
This device is composed of a trocar containing a
4b
aspiration and surrounded by a suction cup that fits over the
convex part of the cyst wall. When the device is applied to the
cyst, the negative pressure makes the suction cup adhere hermetically to the cyst wall, which impedes the extravasation of
the content as it is suctioned out and eliminates the possibility of intraoperative contamination. The cystic contents are
partially aspirated and replaced with the same amount of 3%
saline solution. This maneuver is repeated several times with
a wait of 3–5 minutes between applications.
needle connected to a system of negative pressure
4b
Cystectomy is then performed and the membrane
4c
removed.
4c
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MANAGEMENT OF THE RESIDUAL CAVITY
Management of the residual cavity involves the partial resection of the pericystic layer and capitonnage.
a
The partial pericystectomy leaves intact the
5a, b
be closed with individual sutures, and the free portion of the
pericystic membrane should be resected.
internal layer. The bronchial openings should
5a
b
5b
5c, d
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rows of sutures.
Operation 203
The capitonnage is the obliteration of the
residual space by placement of concentric
5c
5e, f
5d
The visceral pleura is sewn over the incision.
5e
5f
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