Download Palliative Stenting for Benign or Malignant Obstructions

Metropolitan New Jersey Veterinary Medicine Association
New Jersey
IR or the OR? How interventional radiology can help your patients
Chick Weisse, Diplomate ACVS
Animal Medical Center, NY, NY
[email protected]
Following the description of percutaneous arterial catheterization by Sven Ivar Seldinger
in 1953, angiography developed into a widely-utilized and essential medical diagnostic
tool (for humans). Technological advances have since helped transform this diagnostic
modality into a sub-specialization with enormous therapeutic potential. Interventional
radiology (IR) involves the use of contemporary imaging techniques such as fluoroscopy
and ultrasonography to selectively access vessels and other structures in order to
deliver different materials for therapeutic reasons.
ADVANTAGES AND DISADVANTAGES
The use of IR techniques in veterinary patients offers a number of advantages
compared to more traditional therapies. These procedures are minimally invasive and
can therefore lead to reduced peri-operative morbidity and mortality, shorter anesthesia
times and shorter hospital stays. Some less equipment-intensive procedures can result
in reduced costs as well. In addition, some techniques such as chemoembolization of
tumors or palliative stenting for malignant obstructions offer alternative treatment
options for patients with various conditions that may not be amenable to standard
therapies.
The primary disadvantages of IR include the required technical expertise, the
specialized equipment necessary (fluoroscopy with or without digital subtraction
capabilities), and the large initial capital investment necessary to provide a suitable
inventory of catheters, guide wires, balloons, stents and coils.
EQUIPMENT AND TECHNIQUE
As most of these procedures are minimally invasive (performed through catheters or
small holes in the skin), traditional sterile operating rooms are not required, but
recommended. Most of these procedures are performed in clean angiography suites.
The entry sites receive a traditional sterile scrub, and operators wear full lead gowns,
lead thyroid shields, caps, gowns, and masks. The radiation exposure during
conventional or C-arm fluoroscopy can be substantial. The operator should review
radiation safety guidelines, minimize exposure time and beam size, and maximize
shielding and distance from the beam.
For many of the more commonly performed IR procedures, a traditional fluoroscopy unit
is sufficient. A C-arm fluoroscopy unit has the advantage of mobility of the image
intensifier, permitting multiple tangential views without moving the patient.
Occasionally, ultrasonography is useful for percutaneous needle access into vessels or
other structures. Digital subtraction angiography (DSA) and “road-mapping” allow high
resolution images to be obtained with minimal use of contrast agent which is often a
concern in our relatively small veterinary patients. DSA is required for super-selective
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Metropolitan New Jersey Veterinary Medicine Association
New Jersey
IR or the OR? How interventional radiology can help your patients
Chick Weisse, Diplomate ACVS
Animal Medical Center, NY, NY
[email protected]
angiograms of small caliber vessels and those vessels in the head (or where there is
substantial bone which makes angiogram visualization difficult).
EXAMPLES OF COMMONLY PERFORMED PROCEDURES
Tracheal Stenting
Tracheal collapse is a progressive, degenerative disease of
the cartilage rings in which hypocellularity and decreased
glycosaminoglycan and calcium content leads to dynamic
tracheal collapse during respiration. Many of these animals
are palliated with medications including anti-inflammatories,
cough
suppressants,
sedatives/tranquilizers,
and
bronchodilators. Candidates for surgical therapy are those
that have failed initial conservative medical management. Various surgical techniques
have been described, however the currently recommended surgical therapy for patients
with extrathoracic tracheal collapse is extraluminal polyprolpylene ring (or spiral)
prostheses. The current therapy in humans is intra-luminal stenting with one of a
number of FDA-approved tracheobronchial stents. A number of stents have been
evaluated in the canine trachea, including both balloon-expandable (Palmaz), and selfexpanding (Stainless steel, Laser-cut nitinol, Knitted nitinol) stents (see tracheal stent
figure).2-4 Clinical improvement rates in 75%-90% of animals treated with selfexpanding, intra-luminal stainless steel stents have been reported.3,4 Immediate
complications were mostly minor although there was a peri-operative mortality rate of
approximately 10%.
Late complications included stent shortening, excessive
granulation tissue, progressive tracheal collapse, and stent fracture.
Congenital Intrahepatic Portosystemic Shunts
Portosystemic shunts (PSSs) are anomalous vascular communications between the
portal venous and systemic circulations that result in a clinical syndrome with various
neurological, biochemical, and hematological consequences. Numerous techniques
have been described for intrahepatic PSS attenuation, ranging from careful liver
dissection around the shunting vessel to more technically demanding and complicated
procedures involving temporary vascular hepatic inflow occlusion for intravascular repair
(References available from the author). A review of six major veterinary reports on
canine intrahepatic PSSs reveals mortality rates following surgical treatment ranging
from 10% to 66%.5-10 The majority of mortalities occurred peri-operatively with fewer
than 20% occurring later than one week post-operatively. The goal of IR techniques for
intrahepatic PSSs is to reduce the unacceptably high, peri-operative mortality rates
associated with traditional open surgical techniques and hopefully improve the outcome
for these cases. We have performed over 60 percutaneous transvenous coil
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Metropolitan New Jersey Veterinary Medicine Association
New Jersey
IR or the OR? How interventional radiology can help your patients
Chick Weisse, Diplomate ACVS
Animal Medical Center, NY, NY
[email protected]
embolizations (PTCE) with a vena caval stent and thrombogenic coils placed within the
shunt.11 Peri-operative complications were minor and peri-operative mortalities were
comparatively low.
Percutaneous Transarterial Embolization and Chemoembolization (TACE)
Bland arterial embolization entails selective, catheter-directed delivery of particulate
material in order to control hemorrhage, occlude vascular malformations, or reduce
tumor growth. Chemoembolization involves selective intra-arterial chemotherapy
delivery in conjunction with subsequent particle embolization.
Intra-arterial
chemoembolization has been shown to result in a 10- to 50-fold increase in intratumoral drug concentrations when compared to systemic intravenous chemotherapy
administration.12 Various tumors may respond to chemoembolization as well. We have
performed this procedure in dogs with unresectable invasive sinus carcinomas with
some encouraging results.
Palliative Stenting for Benign or Malignant Obstructions
Veterinary patients can present with advanced stages of
malignancy in which traditional therapies such as surgery,
chemotherapy, or radiation therapy are either associated with
excessive morbidity, cost, or poor outcome. Presenting
clinical signs may be associated with the tumor location and
subsequent local effects rather than the systemic effects of
the tumor burden. For example, malignant obstructions of
the urinary tract are usually due to transitional cell
carcinomas or prostatic tumors and affected animals can
present with life-threatening signs associated with urinary
tract obstruction. IR techniques involving the placement of
intra-luminal stents to palliate similar malignant obstructions
in humans have been described (see urethral stent figure). The author has performed a
number of palliative stenting procedures in the urinary tract, and upper and lower
gastrointestinal tracts to relieve luminal obstructions due to
neoplasia in animals as small as a ferret. These IR
techniques were rapid, safe, and effective, and
complications were minor and uncommon.14
Endourology
Similar techniques are currently being employed to manage
ureteral obstructions secondary to stones (see ureteral
stent figure to right), strictures, or malignancies. These
procedures can be performed surgically or with minimal
invasiveness (percutaneously or via cystoscopy) to reduce
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Metropolitan New Jersey Veterinary Medicine Association
New Jersey
IR or the OR? How interventional radiology can help your patients
Chick Weisse, Diplomate ACVS
Animal Medical Center, NY, NY
[email protected]
morbidity and improve outcomes in certain patients.
REFERENCES
1
Buback JL, Boothe HW, and Hobson HP. Surgical treatment of tracheal collapse in dogs: 90 cases
(1983-1993) Journal of the American Veterinary Medical Association 1996; 208(3):380-384.
2
Radlinsky MG, Fossum TW, Waler MA, et al. Evaluation of the palmaz stent in the trachea and
mainstem bronchi of normal dogs. Veterinary Surgery 1997; 26(2):99-107.
3
Norris JL, Boulay JP, Beck KA, et al. Intraluminal self-expanding stent placement for the treatment of
tracheal collapse in dogs (abstr), in Proceedings, 10th Annual Meeting of the American College of
Veterinary Surgeons 2000.
4
Moritz A, Schneider M, and Bauer N. Management of advanced tracheal collapse in dogs using
intraluminal self-expanding biliary wallstents. Journal of Veterinary Internal Medicine 2004; 18:31-42.
5
White RN, Burton CA, McEvoy FJ. Surgical treatment of intrahepatic portosystemic
shunts in 45 dogs. Veterinary Record 1998; 142:358-365.
6
Bostwick DR, Twedt DC. Intrahepatic and extrahepatic portal venous anomalies in dogs: 52 cases
(1982-1992). Journal of the American Veterinary Medical Association 1995; 206(8):1181-1185.
7
Komtebedde J, Forsyth SF, Breznock EM, et al. Intrahepatic portosystemic venous anomaly in the dog
perioperative management and complications. Veterinary Surgery 1991; 20:37-426.
8
Breznock EM, Berger B, Pendray D, et al. Surgical manipulation of intrahepatic portocaval shunts in
dogs. Journal of the American Veterinary Medical Association 1983; 182:798-805.
9
Tisdall PLC, Hunt GB, Bellenger CR, et al. Congenital portosystemic shunts in maltese and Australian
cattle dogs. Australian Veterinary Journal 1994; 71:174-178.
10
Kyles AE, Gregory CR, Jackson J, et al. Evaluation of a portocaval venograft and ameroid ring for the
occlusion of intrahepatic portocaval shunts in dogs. Veterinary Surgery 2001; 30(2):161-169.
11
Weisse C, Solomon JA, Holt D, et al. Percutaneous transvenous coil embolization of canine
intrahepatic portosystemic shunts: Short term results in 14 dogs (abstr), in Proceedings, 13th Annual
Meeting of the American College of Veterinary Surgeons 2003; 21-22.
12
Dyet J, Ettles D, Nicholson A, eds., et al. Textbook of Endovascular Procedures. 1st ed. Philadelphia:
Churchill Livingstone, 2000:357-367.
13
Valji K, ed.
1999;12,225.
14
Vascular and Interventional Radiology.
1 st ed.
Philadelphia: W.B. Saunders Co,
Weisse C, Hume DZ, Berent A, et al. Palliative Stenting for Malignant Obstructions in a Dog, Cat, and
Ferret (abstr) Submitted to the 14th Annual Meeting of the American College of Veterinary Surgeons.
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