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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3869_Библиотеки_им_академика_М_И_Перельмана.pdf
90 J. Jackson
a
Fig. 9.2 Seventy-two-year-old man with pulmonary fibrosis and massive hemoptysis. (a) Coronal
MDCT reformation shows hypertrophied bronchial artery (arrow) arising from the inferior aspect
of the aortic arch. (b) Selective arteriogram of this hypertrophied anomalous combined right and
left bronchial arteries trunks prior to embolization
b
Pre-procedure Imaging: Why?
Pre-procedural CT is extremely helpful to document the number and size of treatable
lesions.
• Number of feeding vessels. There is often a dominant feeding artery to a PAVM
but it is not uncommon to find additional small feeders, which may arise from a
different segmental pulmonary artery branch, which will continue to perfuse the
venous sac. These will gradually enlarge over time if missed and left untreated.
A knowledge of the presence of multiple feeding arteries before intervention is
very helpful so that this is avoided (Fig. 9.3).
• Number of malformations. CT is now the gold-standard imaging modality when
it comes to the demonstration of treatable PAVMs. If there are no treatable malformations in one lung, then selective proximal pulmonary angiography of that
side is unnecessary, thereby reducing radiation and contrast dose and procedural
time.
Deciding whether endovascular therapy is indicated
• PAVM size. Remember that it is the size of the feeding artery to a PAVM, rather
than its venous sac, that is important when assessing these lesions and determining their suitability for treatment. It is generally recommended that all PAVMs
with feeding arteries of 3 mm or greater in size are treated, as these are more
likely to be a route for paradoxical embolization. Knowledge of the approximate diameter of the feeding arteries to each PAVM can be very helpful when
determining the most appropriate embolic agent to use.
• Exclusion of PAVM mimics. Although PAVMs have characteristic features on CT
with dilated feeding and draining vessels and an intervening venous sac, there
are two uncommon lesions which may be a trap for the unwary and result in a
referral for inappropriate angiography.
9 Pre-procedure Imaging: When, Why, and How? 91
a
b
c
d
Fig. 9.3 Thirty-two-year-old lady with hereditary hemorrhagic telangiectasia and a single right
upper lobe PAVM. (a) Single axial image from an unenhanced thoracic CT demonstrates a lobulated venous sac and a large outflow vein. Other images (not shown) suggested the presence
of a dominant feeding artery with an adjacent smaller branch also supplying the venous sac.
(b) Selective right pulmonary artery angiogram shows a single PAVM at the right lung apex with
a dominant feeding artery. (c) Selective pulmonary angiogram after coil occlusion of the dominant
feeding artery at the neck of the malformation shows persistent sac perfusion from an adjacent
small vessel (arrow). (d) Selective pulmonary arteriogram after coil embolization of both feeding
arteries confirms complete occlusion of the PAVM
92 J. Jackson
◦ Congenital pulmonary varix: this is an intrapulmonary collateral vein bypass-
ing a segment of atretic pulmonary vein. Close scrutiny of these vessels and
their communications will allow their correct diagnosis.
◦ Congenital bronchial atresia: the expanded branching bronchi distal to the
atretic segment will often contain fluid of high attenuation which may be
mistaken for vascular enhancement on a contrast-enhanced CT. The correct
diagnosis will usually be suggested by the fact that the branching bronchi do
not reach the lung hilum and that there is an area of surrounding hypertransradiancy due to air-trapping.
Pre-procedure Imaging: How?
Contrast enhancement is unnecessary. A volume acquisition during a single breathhold is all that is required and the study is best viewed on a workstation in axial,
coronal, and sagittal planes.
Abdominal Embolization
The two acute scenarios which require urgent assessment and intervention are acute
gastrointestinal tract hemorrhage and trauma.
Acute Gastrointestinal Hemorrhage
Pre-procedure Imaging: When?
Patients with recurrent episodes of acute gastrointestinal hemorrhage in whom
endoscopy has failed to determine the source are one of the most frustrating groups
in interventional radiology. By the time these patients have been admitted to hospital, bleeding has often stopped and visceral angiography is negative. MDCT has
become an invaluable tool in the management of these individuals and has become
the imaging procedure of first choice in many centers when endoscopy is negative
for the following reasons:
• Tim e: it is usually quicker to organize and perform MDCT than formal catheter
angiography.
• Safety: MDCT is less invasive and can be more easily repeated.
• Sensitivity: MDCT is almost certainly more sensitive than formal angiography at
determining the source and/or cause of hemorrhage because of the following:
◦ Rapid access to imaging increases the likelihood of continuing bleeding at the
time of study.
◦ Reduction in respiratory artifact.
◦ Demonstration of other significant pathology, for example, liver cirrhosis,
varices, inflammatory or neoplastic bowel disease.
9 Pre-procedure Imaging: When, Why, and How? 93
Pre-procedure Imaging: Why?
Demonstrating the target vascular anatomy
• Variants of normal visceral arterial anatomy are extremely common and should
be looked for, as they may affect subsequent embolization.
Anticipating the approach, equipment, and techniques which will be required for
effective treatment
◦ The demonstration of the source of contrast medium extravasation helps con-
siderably when performing embolization as this area can be targeted from the
very beginning of the procedure.
◦ Close scrutiny of the vascular anatomy on axial, coronal, and sagittal refor-
matted images can be extremely useful to help plan the most appropriate route
and catheter for subsequent catheter angiography and embolization (Fig. 9.4).
◦ For example, the demonstration of a pseudoaneurysm of the inferior
pancreatico-duodenal artery originating from the first jejunal artery would suggest that a catheter with a “Cobra” configuration catheter might be the most
suitable to start with, while an area of contrast medium extravasation within
the distal transverse colon originating from an accessory middle colic artery
might be best approached using a “Sidewinder”-shaped catheter.
Deciding whether endovascular therapy is indicated
◦ MDCT allows appropriate referral for further therapy. In many cases this will
be embolization, but occasionally a source of hemorrhage will suggest that an
endoscopic or surgical approach is more appropriate (Fig. 9.5).
◦ In the absence of active extravasation, important underlying pathology may be
identified but might be subtle. For example, a Meckel’s diverticulum causing
intermittent, short-lived episodes of acute hemorrhage may easily be missed
unless specifically searched for with the help of multiplanar reformatted
images (Fig. 9.6).
◦ Absence of a source of hemorrhage on MDCT makes it unlikely that catheter
angiography performed immediately afterwards will be contributory.
Pre-procedure Imaging: How?
Timing . The best chance of “catching” active contrast medium extravasation is when
there are clinical signs of ongoing hemorrhage, i.e., when the patient is hypotensive
with a shock index (heart rate/systolic blood pressure) of >1. Clinicians involved
with the patient’s resuscitation should be aware of the importance of performing
this study as soon as it is safe to do so. If the patient is “fit enough” to allow transfer
to the radiology department for angiography and embolization, then they should
undergo CT while the interventional suite is being prepared.
Technique. Volumetric acquisitions through the entire abdomen and pelvis should
be performed without intravenous contrast medium and then during the arterial and
portal venous phases of contrast medium enhancement. Oral contrast should not be
used. Important points regarding image interpretation are as follows:
94 J. Jackson
a
c
b
d
e
Fig. 9.4 Thirty-year-old man with several episodes of upper gastrointestinal hemorrhage during
recovery from acute pancreatitis. (a) MDCT coronal reformatted image demonstrates a pseudoaneurysm arising from the gastroduodenal artery. Other images (not included) showed anomalous
visceral arterial anatomy with the common hepatic artery arising from the proximal superior mesenteric artery. (b) Selective superior mesenteric artery angiogram confirms the anomalous anatomy and shows faint filling of the pseudoaneurysm cavity which has markedly increased in size
9 Pre-procedure Imaging: When, Why, and How? 95
Fig. 9.5 Seventy-year-old
man with massive bright red
blood loss per rectum. Lower
GI endoscopy before imaging
showed copious blood but no
source. (a and b) Axial and
sagittal images obtained
during the arterial phase of
contrast medium
enhancement show rapid
contrast medium
extravasation in the low
rectum. A repeat endoscopy
confirmed an actively
bleeding rectal ulcer which
was successfully treated
a
b
• Active contrast medium extravasation is most commonly seen on the arterial
phase images but it can be subtle and may only be visualized during careful comparison of both the post-contrast and unenhanced studies (Fig. 9.7). Reformatted
images often make the bleeding and the underlying cause much more obvious.
Fig. 9.4 (continued) since the MDCT. (c) A selective common hepatic artery angiogram shows
the anatomy in greater detail. (d and e) Control film and angiogram after embolization confirm
complete exclusion of the pseudoaneurysm from the circulation with coils in three separate branch
vessels immediately beyond the pseudoaneurysm neck and within the distal gastroduodenal artery
with preservation of the retroduodenal artery arising more proximally
96 J. Jackson
Fig. 9.6 Twenty-eight-year-old
man with intermittent
episodes of acute lower GI
hemorrhage. MDCT
performed soon after
admission following further
bleed when patient
hemodynamically stable.
(a and b) Axial and coronal
images do not demonstrate
active contrast medium
extravasation but a
blind-ending fluid-filled
viscus is seen in the right
lower abdomen consistent
with a Meckel’s diverticulum
confirmed at subsequent
surgery
a
b
• The unenhanced study is also important so that high-attenuation material within
the bowel lumen, such as vicariously excreted contrast medium following
previous imaging, is not mistaken for active extravasation.
• Following surgery, think what anatomical changes will be present and also the
likely source of bleeding.
Trauma (see also Chapter 10)
The advent of MDCT has been described as the greatest advance in trauma care
that has occurred in the last 25 years. It has resulted in diagnostic angiography
becoming almost obsolete, as most significant vascular injuries will be identified but, along with a trend toward non-surgical management, there has been an
increase in the indications for embolization. The major indication for embolization following accidental or iatrogenic abdominal trauma is arterial bleeding from
the liver, spleen, or kidneys. Severe bleeding following percutaneous biopsy of the
liver or kidney is uncommon but, when it occurs, is generally easily controlled by
9 Pre-procedure Imaging: When, Why, and How? 97
Fig. 9.7 Sixty-seven-year-old
man with intermittent
episodes of bright red
bleeding per rectum. Pre- and
post-contrast medium axial
images demonstrate a subtle
area of active contrast
medium extravasation into a
mid-transverse colon
diverticulum (arrow)which
would have been difficult to
appreciate without the
unenhanced study
selective embolization. Pre-procedural imaging is rarely necessary, as the cause of
sudden hemodynamic collapse within a few hours of biopsy is usually obvious; such
patients should be transferred to the interventional suite for embolization as soon as
possible after initial resuscitation. All other individuals with evidence of hemorrhage following accidental trauma or surgery should be assessed by MDCT before
proceeding to embolization.
Pre-procedure Imaging: How?
Several algorithms are listed in the table in Chapter 10 (p. 108). The MDCT technique utilized needs to be tailored to the patient and will depend upon the nature of
the trauma but, in the majority of cases, images obtained during the arterial phase
of contrast medium enhancement are the most helpful.
Deciding whether endovascular therapy is indicated
Important points regarding image interpretation include the following:
• Active contrast medium extravasation within the liver and spleen is usually
obvious and is an indication for urgent angiography and embolization.
• Pseudoaneurysms within the substance of the liver and spleen may be small
but are usually easily visualized and are, once again, an indication for urgent
angiography and embolization as they are at high risk of re-bleeding.
98 J. Jackson
• Prophylactic splenic artery embolization is unnecessary in the absence of active
contrast medium extravasation and pseudoaneurysm formation even in the
presence of a high-grade splenic injury.
• A pseudoaneurysm involving the extrahepatic portion of the right hepatic artery
is most commonly iatrogenic and is well recognized after laparoscopic cholecystectomy, particularly if there is a concomitant bile duct injury. It is at high risk of
rupture causing extrahepatic hemorrhage or hemobilia, if it communicates with
the biliary tree and should be treated by embolization. Such pseudoaneurysms
may be small and difficult to visualize unless specifically looked for with the aid
of multiplanar and 3D reconstructions.
True Aneurysms of the Visceral Arteries
True aneurysms of the visceral arteries are rare and are often an incidental finding
on cross-sectional imaging. The splenic artery is the visceral vessel most commonly
involved followed by extrahepatic and renal artery aneurysms.
Pre-procedure Imaging: When?
While the risk of hemorrhage from true visceral artery aneurysms is not known, it
is recognized that their rupture is more common during pregnancy and in patients
undergoing liver transplantation. Treatment of aneurysms of 2 cm in diameter
or greater is recommended in women of child-bearing age who wish to become
pregnant at some stage and in persons undergoing liver transplantation.
The indications for treatment outside these patient groups are not as clear-cut,
but therapy is generally advised for aneurysms of greater than 2.5 cm in diameter,
those who show a gradual increase in size on follow-up and those associated with
symptoms due, for example, to peripheral embolic events.
Pre-procedure Imaging: Why?
If the decision has been made that treatment is necessary and that an endovascular
approach is the most appropriate, pre-procedural imaging is essential in order to
document completely the anatomy of the aneurysm, plan the best route of access,
and ensure availability of all t he equipment (sheaths, catheters, guidewires, and
embolization agents) which is likely to be required to ensure a successful outcome.
Pre-procedure Imaging: How?
MDCT during the arterial phase of contrast medium enhancement should be performed through the area of interest, and multiplanar and 3D reconstructions should
be viewed on a workstation. Important points regarding image interpretation include
the following:
• Proximal parent vessel anatomy. Embolization is most commonly performed via
a common femoral artery approach, but occasionally approach will be more
9 Pre-procedure Imaging: When, Why, and How? 99
favorable from the arm when the visceral artery requiring catheterization has
an acutely angled origin from the aorta. Compression of the celiac axis origin
by the median arcuate ligament of the hemidiaphragm is relatively common and
its recognition on pre-procedural CT may indicate that an arm approach may
be necessary. Look carefully for stenosis of the celiac axis and/or the superior mesenteric artery origins in the presence of pancreatico-duodenal artery
aneurysmal disease.
• Vascular anatomy around the aneurysm neck.
◦ Visceral arterial disease typically occurs at bifurcations (particularly common
in splenic and renal arteries), and a complete understanding of the anatomy of
such aneurysms before intervention is essential in order to determine the most
suitable technique of embolization.
a
c
b
d
Fig. 9.8 Sixty-nine-year-old man with an incidental finding of a large hepatic artery aneurysm
during investigation of renal pathology. (a) Axial image from arterial phase MDCT shows large
aneurysm of common hepatic artery. Other images (not included) showed complex distal anatomy
involving the bifurcation into the right and left hepatic arteries. (b) Selective common hepatic artery
confirms extension of the aneurysm up to its bifurcation. (c and d) Control film and arteriogram
after coil embolization of the left hepatic artery and the placement of covered stents from the
proximal common hepatic artery into the right hepatic artery showing successful exclusion of the
aneurysm