Non-Oncologic Vascular Procedures
Intrahepatic Portosystemic Shunts
A portosystemic shunt is an abnormal connection between major blood vessels in the abdomen. This abnormal connection results in blood bypassing the liver and prevents the liver from performing blood filtering. Signs that may be noted in dogs and cats with portosystemic shunts include, but are not limited to, small body size, low energy level, mental dullness and seizures.
A minimally-invasive procedure has been developed in which coils are placed in the portosystemic shunt to allow the shunt to close down progressively over time. The coils are held in place by the use of a metal or metal-alloy stent. The entire procedure is performed through a small puncture in a blood vessel in the neck region. The goal of the procedure is to help the liver be able to perform normal functions more effectively as more blood travels through the liver.
Intrahepatic portosystemic shunts (IHPSS) present an important disease state in dogs and cats. While medical management is often involved in the treatment regimen for IHPSS, permanent occlusion is often recommended for dogs with IHPSS as long-term outcome is poor due to persistent clinical signs and continued poor liver perfusion. (Tobias 1996) Surgical treatments depend on the location of the shunt, and both extravascular and intravascular options have been described.
The use of transvenous coil embolization has been recently documented in several veterinary studies. (Partinton 1993, Gonzaol 2000, Leveille 2003, Asano 2003, Bussadori 2008) This procedure involves the placement of a stent within the caudal vena cava combined with thrombogenic coils within the shunt itself. The goal of the procedure is that the shunt will close down progressively over time allowing the portal vein time to develop.
This procedure is performed with the patient under general anesthesia and placed in dorsal recumbency. A tiny incision is made over the jugular vein, and the entire procedure is performed through a vascular access sheath that is placed in the jugular vein. Due to the minimally-invasive nature of the procedure, morbidity is considered low, and pain is generally not noted post-coil placement.
Diagnostic and Treatment Steps at UC Davis
Initial diagnostics performed at UC Davis will likely include bloodwork (complete blood count, chemistry panel, coagulation panel, pre- and post-prandial bile acids, ammonia level), abdominal ultrasound and computed tomographic angiography. Depending on the location and size of the shunt, transvenous coil embolization may be recommended. If deemed to be a good candidate for transvenous coil embolization, a stent will be ordered that is appropriate for that patient. The patient is placed under general anesthesia, and the procedure is performed. Future diagnostics that may be recommended include bloodwork (complete blood count, chemistry panel, coagulation panel, pre- and post-prandial bile acids, ammonia level), abdominal ultrasound and computed tomographic angiography.
- Asano K, Watari T, Kuwabara M, et al. Successful treatment by percutaneous transvenous coil embolization in a small breed dog with intrahepatic portosystemic shunt. J Vet Med Sci 2003;65: 1269–1272.
- Bussadori R, Bussadori C, Millán L, et al. Transvenous coil embolisation for the treatment of single congenital portosystemic shunts in six dogs. Veterinary J 2008;176:221-226.
- Gonzalo-Orden JM, Altonaga JR, Costilla S, et al. Trans-venous coil embolization of an intrahepatic portosystemic shunt in a dog. Vet Radiol Ultrasound 2000;41:516–518.
- Leveille R, Johnson SE, Birchard SJ. Transvenous coil embolization of portosystemic shunt in dogs. Vet Radiol Ultrasound 2003;44:32–36.
- Partington BP, Partington CR, Biller DS, et al. Transvenous coil embolization for treatment of patent ductus venosus in a dog. JAVMA 1993;202:281–284.
- Tobias KM, Rawlings CA. Surgical techniques for extravascular occlusion of intrahepatic shunts. Comp Cont Educ 1996;18:745-754.
An arteriovenous fistula/malformation otherwise known as an AVF or AVM is an abnormal connection (or several) between an artery and a vein. This usually develops during pregnancy, however, trauma and surgery can also lead to the development of an AVF or AVM. Depending on the location of the AVF/AVM, your pet may experience an accumulation of fluid or a swelling. These fluid accumulations can cause discomfort or excessive pressure on surrounding tissue.
Some AVF/AVM can be eliminated by the placement of glue or other agents in the blood vessel to close down the communication. This procedure is not possible in all cases, but when it can be performed, dramatic improvement may occur.
An arteriovenous fistula (AVF) is a single anomalous connection between an artery and a vein whereas an arteriovenous malformation (AVM) includes multiple arteries and veins. These abnormalities occur very uncommonly and are usually congenital, although surgery, neoplasia and trauma can result in AVF/AVM. The most common location for AVF in dogs has been reported to be the liver. (Chanoit 2007)
Treatment has historically involved the surgical resection of AVF; surgical treatment of AVMs is often not possible due to the extensive nature of the disease. (Chanoit 2007) Recently, the use of embolization in the treatment of AVF, specifically in the liver, has been investigated. For this procedure, the hepatic artery is selected with a guidewire and catheter, and a sterile glue is injected into the AVF to cause embolization. In a small case series comparing surgical resection to glue embolization, the use of glue embolization was considered a good alternative to surgery as hepatic AVF-related death occurred less frequently. (Chanoit 2007)
Diagnostic and Treatment Steps at UC Davis
Upon admission to UC Davis, likely diagnostics that will be performed (depending on AVF or AVM location) will include bloodwork (complete blood count, chemistry panel, coagulation panel), chest radiographs, abdominal ultrasound, and computed tomographic angiography of the affected area. General anesthesia will be necessary to perform angiography of the affected region and to consider if embolization is a suitable treatment option.
- Chanoit G, Kyles AE, Weisse C, et al. Surgical and interventional radiographic treatment of dogs with hepatic arteriovenous fistulae. Vet Surg 2007;36:199-209.
Intravascular Foreign Body Removal
Intravenous (IV) catheters are commonly placed in dogs and cats for both elective and non-elective procedures. If an IV catheter is accidentally cut during removal, part of the catheter (“foreign body”) may launch into the patient’s circulatory system. No studies have been performed that document long-term side effects in these patients, however, severe complications have been documented in humans.
Prior to the implementation of IR techniques in veterinary patients, surgery was the only treatment option for removal of these intravascular foreign bodies. With the use of fluoroscopy and a snare that can be manipulated through the circulatory system, these foreign bodies can often be removed through a small incision.
One complication of intravascular catheterization includes breakage or dislodgement of part or all of the intravascular catheter subsequently resulting in an intravascular foreign body. In human medicine, the removal of IV foreign bodies is often considered a necessity. (Kidney 1998) When foreign bodies are left intravascularly, the reported overall major complication or mortality rate ranges from 21-71%. (Richardson 1974, Fisher 1978) Major complications (including causes of mortality) identified in humans include arrhythmias, sepsis, catheter-associated thrombosis, pulmonary emboli, endocarditis, ventricular perforation, adrenal infarction and caval syndrome. (Richardson 1974, Fisher 1978) Human studies have shown that clinical signs may be delayed by up to one year following embolization. (Fisher 1978)
If surgical intervention is necessary for intravascular foreign body removal in the thorax, either a lateral thoracotomy or median sternotomy is typically necessary. These procedures may involve considerable morbidity and potential complications should be considered. (Yang 1994) The use of a minimally invasive technique for foreign body removal is an attractive alternative to these more invasive procedures. Percutaneous intravascular foreign body removal in humans has a success rate of 90-100%. (Uflacker 1986, Dondelinger 1991, Egglin 1995)
While intravascular foreign bodies are still an uncommon entity, the use of more minimally-invasive interventional techniques in veterinary medicine will likely lead to increased encounters. A recent report documented the percutaneous removal of intravascular foreign bodies in 5 dogs, a goat and a horse. All devices were successfully removed with the use of a snare that was controlled under fluoroscopic guidance. (Culp 2008)
Diagnostic and Treatment Steps at UC Davis
The percutaneous retrieval of intravascular foreign bodies is performed under general anesthesia. Prior to initiating anesthesia, bloodwork (complete blood count and chemistry panel) and chest radiographs will be performed.
- Culp WTN, Weisse C, Berent AC, et al. Percutaneous endovascular retrieval of an intravascular foreign body in five dogs, a goat and a horse. JAVMA 2008;232:1850-1856.
- Dondelinger RF, Lepoutre B. Kurdziel JC. Percutaneous vascular foreign body retrieval: experience of an 11-year period. Eur J Radiol 1991;12:4–10.
- Egglin TKP, Dickey KW, Rosenblatt M, et al. Retrieval of intra- vascular foreign bodies: experience in 32 cases. AJR 1995;164:1259–1264.
- Fisher RG, Ferreyro R. Evaluation of current techniques for nonsurgical removal of intravascular iatrogenic foreign bodies. AJR 1978;130:541–548.
- Kidney DD, Nguyen DT, Deutsch LS. Radiologic evaluation and management of malfunctioning long-term central vein catheters. AJR 1998;171:1251–1257.
- Richardson JD, Grover FL, Trinkle JK. Intravenous catheter emboli. Am J Surg 1974;128:722-727.
- Uflacker R, Lima S, Melichar AC. Intravascular foreign bodies: percutaneous retrieval. Radiology 1986;160:731–735.
- Yang FS, Ohta I, Chiang H, et al. Non-surgical retrieval of in- travascular foreign body: experience of 12 cases. Eur J Radiol 1994;18:1–5.
Epistaxis (bleeding from the nostril)
Nose bleeds (epistaxis) can develop from nasal trauma, cancer and inflammation, but on occasion, a nose bleed may develop from unknown causes (“idiopathic epistaxis”). The bleeding that occurs in these cases may be excessive, and can lead to life-threatening blood loss. In some of these cases, an agent can be injected through a catheter into the bleeding vessel to cause the vessel to occlude, thus preventing further bleeding. This procedure is performed through a very small incision, and post-procedure pain is very minimal.
Epistaxis is a potentially life-threatening condition that may occur secondary to severe nasal inflammation, trauma, neoplasia or coagulopathy. (Gieger 2004) Additionally, idiopathic epistaxis has also been reported. (Bissett 2007) For conditions where the underlying cause is known, treatment for that cause is pursued. In cases of idiopathic epistaxis, methods that may be tried to eliminate the bleeding include packing with sponges coated with a vasoconstrictive medications, ligation of carotid artery(ies) and embolization of the supplying arterial supply. (Weisse 2004)
Arterial (or bland, meaning without chemotherapy) embolization involves the delivery of an agent to the bleeding vessel that stimulates thrombosis in that vessel. To perform arterial embolization, a patient is placed under general anesthesia. An artery (likely femoral) is catheterized and a wire/catheter combination is steered toward the vessel that is bleeding. Upon reaching the vessel, an agent (particles, coils, liquid) that stimulates thrombosis is delivered to the vessel and results in cessation of blood flow through that vessel. Reports of this treatment in animals are rare, but this treatment has been performed successfully in three dogs with intractable epistaxis. (Weisse 2004)
Diagnostic and Treatment Steps at UC Davis
Diagnostics to assess the cause of epistaxis will likely be recommended. This will include bloodwork (complete blood count, chemistry panel, coagulation panel), chest radiographs, abdominal ultrasound, rhinoscopy and computed tomography scan of the nasal cavity and skull. Depending on the cause of epistaxis, arterial embolization may be recommended during the anesthesia for computed tomography.
- Bissett SA, Drobatz KJ, McKnight A, Degernes LA. Prevalence, clinical features, and causes of epistaxis in dogs: 176 cases (1996-2001). JAVMA 2007;231:1843-1850.
- Gieger T, Northrup N. Clinical approach to patients with epistaxis. Comp Cont Educ Pract 2004;26:30-43.
- Weisse C, Nicholson ME, Rollings C, et al. use of percutaneous arterial embolization for treatment of intractable epistaxis in three dogs. JAVMA 2004;224:1307-1311.