CLINICAL TRIAL: Protocol No.  VC-014

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A randomized, blinded, placebo-controlled field study to determine the efficacy and safety of TANOVEA®-CA1 (rabacfosadine for injection) in dogs

Sponsor: VetDC, Inc.

TANOVEA®-CA1 (rabacfosadine for injection) is the first and only FDA conditionally approved drug for the treatment of lymphoma in dogs.  This pivotal study is intended to provide the data to demonstrate substantial evidence of effectiveness as well as additional safety information in support of full FDA approval.

VC-014 is a randomized, multi-center, double-blinded, placebo-controlled study evaluating TANOVEA®-CA1 (rabacfosadine for injection) administered every three weeks for up to five treatments in dogs with lymphoma (either previously treated or untreated).    In order to participate in the study, dogs must meet eligibility criteria described in the protocol.  The study is fully funded by the Sponsor, and owners will be offered a clinic credit towards additional treatment in the event of disease progression.  

Contact Dr. Brenda Phillips, Veterinary Specialty Hospital, at 858-875-7500 with any questions.

Metronomic Chemotherapy

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Written by Mairin Miller, DVM (Residency-trained in Oncology)

Overview

Metronomic chemotherapy (MC) is the oral administration of anticancer drugs at low, minimally toxic doses on a frequent or continuous schedule. This is commonly executed using a combination of cyclophosphamide (cytoxan) and piroxicam, however several other protocols have been published, including chlorambucil, etoposide and thalidomide. It is often an attractive option for clients due to its relatively low toxicity profile, moderate cost, and less intensive recheck schedule. In contrast to more traditional chemotherapy administered at maximally tolerated doses (MTD), the anticipated outcome with metronomic chemotherapy is disease stabilization or dormancy, therefore it is often pursued as a maintenance therapy, following surgery and/or MTD chemotherapy.

Mechanisms of Action

  1. Antiangiogenic – Angiogenesis, which is the formation of new blood vessels from larger preexisting vessels, is critical for tumor development. This involves the migration, growth and differentiation of vascular endothelial cells, which line blood vessels. Tumor angiogenesis is regulated by inhibiting anti-angiogenic factors and activating pro-angiogenic factors. Metronomic cytoxan administration has been associated with a significant decrease in tumor microvessel density in dogs with soft tissue sarcomas. It also was shown to decrease anti-angiogenic factors VEGF and thrombospondin-1 in a mouse model.
  2. Immunoregulatory – In patients with cancer, immunosuppressive T regulatory (Treg) cells are recruited by the tumor and present at high levels. This suppresses the anti-cancer immune responses and induces tolerance, allowing tumors to evade the immune system. Metronomic cytoxan and chlorambucil have been shown to reduce circulating Treg numbers in dogs with soft tissue sarcomas.
  3. Inhibition of cancer stem cells and tumor dormancy – Cancer stem cells are a subpopulation of cancer cells that act like normal stem cells and can initiate tumor growth. It is theorized that metronomic chemotherapy can target cancer stem cells thereby inducing tumor dormancy, causing a prolonged period of stable disease.

Metronomic Chemotherapy - Source Nature.com

Image Source: Nature.com

Potential Side Effects

Metronomic chemotherapy is well tolerated with minimal risk for bone marrow suppression or gastrointestinal (GI) upset. However, higher cumulative doses of Cytoxan have been associated with an increased risk of developing sterile hemorrhagic cystitis (SHC), which has been reported in 3.6 – 32% of dogs receiving metronomic cytoxan. Acrolein, a breakdown product of cyclophosphamide, is known to irritate the bladder epithelium. Symptoms of SHC include pollakiuria, stranguria and hematuria. In a 2017 study the addition of daily furosemide at 0.5 – 1 mg/kg/day significantly decreased the incidence of SHC with metronomic cytoxan.

Metronomic chemotherapy is often administered in conjunction with an NSAID, such as piroxicam, therefore we can see toxicity associated with these medications. Piroxicam alone has been reported to cause GI toxicity in 6-23% and nephrotoxicity in approximately 5% of cancer-bearing dogs.

Applications

The management of multiple different cancers using metronomic chemotherapy has been reported in the literature. One of the most common applications is in preventing local recurrence in dogs with incompletely excised soft tissue sarcomas. Another protocol using cytoxan, etoposide and piroxicam showed similar survival times to doxorubicin alone when treating dogs with hemangiosarcoma post splenectomy, with a median survival time of 178 days. Metronomic chlorambucil has be trialed in dogs with transitional cell carcinoma of the bladder in dogs, with 70% having a response or sustained stable disease for median of 119 days. Recently, a combination of cytoxan, piroxicam and thalidomide was shown to significantly prolong survival times in dogs with advanced primary lung tumors. Lastly reports of a response in dogs with a mast cell tumor, thyroid carcinoma and histiocytic sarcoma have been published.

Clinical Trial: Novel Pain Management Therapy in Dogs with Severe Elbow Dysplasia

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A Funded Clinical Trial to Evaluate a Novel Pain Management Therapy in Dogs with Severe Elbow Dysplasia

Trial Specifics

This study is designed to evaluate the tolerability, safety and effectiveness of a novel therapy (not yet approved by FDA) to manage pain associated with moderate to severe elbow dysplasia and secondary osteoarthritis in dogs. The investigational drug is administered as an intra-articular injection into both elbows. There is no placebo treatment.

The one-time treatment will be administered under sedation or general anesthesia to approximately 28 client-owned dogs. Owners are required to complete periodic pain assessment surveys and record short at-home videos assessing the dog’s gait. The study staff will train owners on how to complete the assessments.

The dog’s activity also will be tracked through the use of an activity monitor worn on the dog’s collar. Study visits include the dog’s initial consultation, treatment day (Day 0), and then recheck visits on Days 14, 28, 56, and 84.

Medications targeted at the treatment of osteoarthritis / elbow dysplasia pain, except for CBD and other cannabinoids, are acceptable, provided they have been administered for at least 2 weeks prior to enrolling in the study.

Trial Funding

The study is fully funded for its entire duration (approximately 84 days). Funding includes: the initial consultation, the study treatment and administration, radiographs prior to treatment (if not already performed within 2 weeks of enrollment), recheck visits, required bloodwork, and management of side effects that are thought to be directly related to study participation.

Trial Eligibility

Trained veterinarians at the trial sites will evaluate each dog for eligibility.

Dogs are eligible if they meet the following inclusion criteria:

  • Dog’s body weight 10-50 kg
  • Dog has clinical signs and radiographic evidence of elbow dysplasia
  • Dog is experiencing elbow-associated pain that is refractory to standard pain management or owner opts for pain management that is distinct from conventional treatments

Dogs are not eligible if they meet any of the following exclusion criteria:

  • Dog has a life expectancy of < 3 months
  • Dog has any underlying disease that will affect the study objectives or patient safety
  • Dog has concurrent or prior immune-mediated or other disease resulting polyarthropathy
  • Dog is impaired due to neurological disease or other orthopedic disease
  • Dog is pregnant or lactating
  • Dog is participating in another study
  • Dog may be unavailable for the entire trial duration or is felt to be unsuitable by the investigator for any other reason
  • Dog requires medications or supplements during the course of the study that interfere with the objectives of the studyincluding but not limited to TRPV1 agonist or antagonist drugs that could interfere with RTX mode of action (such as cannabinoids like CBD and anandamide).

 

Contact:

Please contact Dr. Sean Aiken, DACVS at 858.875-7500.

VSH Kicks Off Annual Holiday Pet Food Drive

VSH Kicks Off Annual Holiday Pet Food Drive

Now in its 7th year, Veterinary Specialty Hospital is proud to announce the start of our annual holiday pet food drive to help keep pets and their families together!  During the holiday season many families throughout San Diego have a difficult time feeding their human family members, let alone their furry companions. Working in partnership with the Jacobs and Cushman San Diego Food Bank, all dog and cat pet food items will be distributed within the community to benefit San Diego families and their four-legged friends.

During these times many will share what little food they have with their pet, and others will be forced to make the decision to surrender their pet to a shelter. According to the ASPCA, approximately 6.5 million animals enter U.S. animal shelters nationwide every year, with 1.5 million of them, euthanized annually. Today, families still find themselves struggling financially and must make the painful decision to give up their beloved pets to shelters, because they cannot afford to feed them or to care for them.

Donations can be dropped off in the lobby of the North County or San Diego Veterinary Specialty Hospital. For those who prefer online shopping or might be too busy to make a trip to one of the drop-off sites, please have food shipped directly to one of our hospitals (most pet food stores will ship for free!). Note: no glass, raw or homemade items, please.

Several of our referring partners are also participating in the pet food drive, with collection barrels located at their hospitals as well.  Participants include: Academy Animal Hospital, All Creatures Hospital, All Pets Animal Hospital, The Drake Center for Veterinary Care, Governor Animal Clinic, Kensington Veterinary Hospital, Pearson Animal Hospital, Poway Animal Hospital and The North County Credit Union.

Donations will be collected from December 1 through January 4, 2019. Please donate today!

The Danger of Grapes & Raisins to Dogs

Written by:  Erica O’Donnell, DVM, MRCVS

While many of us enjoy sharing snacks with our canine friends, many human foods are toxic to dogs including grapes and raisins.  At this time we do not know the exact toxic mechanism. The toxicity is idiosyncratic, meaning that there is no way to predict which dogs will be affected or not, and some dogs will experience toxicity from a small ingestion while others can ingest large amounts without any obvious problems. Even a small amount in a susceptible dog can be fatal.  Dogs of any age, breed, or gender can be affected.  One of the most serious complications of grape and raisins is that they can cause severe kidney damage leading to acute kidney failure. Clinical signs can include vomiting, diarrhea, decreased appetite, lethargy, weakness, abdominal pain, oliguria (passing only small amounts of urine), or changes in urination or drinking pattern.

If you witness your dog ingesting grapes or raisins, it should be considered an emergency and veterinary evaluation should be sought out immediately. Vomiting should be induced as soon as possible, before the toxins within the fruit can be absorbed.  This should ideally be performed at a hospital under veterinary supervision, and absolutely should not be performed at home if your dog is having trouble breathing, showing any signs of distress, or is lethargic.   You should consult a veterinarian by phone or call Poison Control if you are unable to seek veterinary attention so that vomiting can be induced in as safe a manner as possible.  The next step in decontamination is typically administration of activated charcoal, which binds up any toxin left in the gastrointestinal tract.  Baseline bloodwork and urine testing will be performed to assess for evidence of kidney damage, and kidney values should be checked daily for a few days since renal failure can take up to 72 hours to become apparent in some cases.  Fluid therapy is the mainstay of treatment for grape or raisin toxicity and is typically recommended for 2-3 days.

Most cases of grape or raisin ingestion are diagnosed as a witnessed ingestion, but a veterinarian should still be consulted as soon as possible if partially digested grape or raisin bits are found in feces or vomit.  The best treatment is prevention – keep raisins and grapes out of reach of your dog and notify family members of the toxic potential of these foods.

 

Case Study: Limb Spare

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Akiko is an almost 8 year old spayed female mixed breed dog that presented to VSH North County for evaluation of wounds suffered from a dog bite.I evaluated Akiko the morning after she arrived through our ER. Akiko had a severe wound on the distal aspect of the left thoracic limb. The wound encompassed the entire dorsal metacarpal surface with exposure of the extensor tendons. There was a comminuted grade 3 open fracture of the 5th metacarpal bone. The wound extended to just proximal to the metacarpal pad. There was no overt instability of the carpus and manus as a whole. A dorsopalmar radiograph was obtained and delineated the MC5 fracture but no other overt bony injuries. There was conscious sensation in the digits.

I met with Akiko’s owners and discussed treatment options. They were interested in salvaging her limb if at all possible. The challenges associated with ensuring tissue health followed by obtaining closure of the wound were discussed, but limb salvage was considered feasible since enough of the weight bearing portion of the paw was not affected. We discussed that there would be an initial phase of open wound management to allow granulation tissue formation (ensuring tissue health and greatly reducing the risk of infection), followed by reconstructive procedure(s) to achieve a functional result, as the defect was considered too large to allow second intention healing and in a location that primary closure was not possible.

The wound was managed with daily dry-to-dry bandages until a healthy granulation bed covered the majority of the wound. The dry-to-dry bandages allowed sequential mechanical debridement of the effusive wound. 9 days following initial presentation, Akiko was taken to surgery and a phalangeal fillet procedure performed. The bones of the fractured 5th metatarsal were removed along with the phalanges, but all associated skin and subcutaneous tissue from the digit was left intact. The resulting skin flap was rotated into the wound and sutured either to the adjacent skin or to the granulation bed. The digital pad was included as part of the flap to increase coverage. This procedure resulted in approximately 65% closure of the wound.  This procedure was chosen because the high-grade open fracture was at risk for infection and/or delayed healing, and because loss of the digit would not preclude weight bearing. The phalangeal fillet provides a durable skin flap that is not prone to vascular compromise.

The flap and remaining wound continued to be managed with a bandage using a non-adherent primary layer. At two weeks post-operatively, the flap demonstrated 100% survival including the digital pad. The remainder of the wound continued to contract and epithelialize, so no additional procedures (such as a free skin graft) were elected. The bandage was removed at approximately 5 weeks after presentation, at which time there was a slightly exuberant ~2cm granulation bed remaining on the dorsum of the paw adjacent to the transposed digital pad.

At approximately 6 weeks after initial presentation, the wound was completely closed with the exception of a ~1cm scab in the same dorsal location. Akiko demonstrated a grade 1/4 left thoracic limb lameness. The owners were instructed to wean Akiko off of her e-collar if and when she does not resort to self-trauma. No further intervention is planned.

Sun Protection for Your Pets

Our pets are just as vulnerable to sunlight-induced skin disease as we are. Some pets worship the sun as much as their beach-going humans do. In people, addiction to tanning is associated with the production of endorphins produced as part of the skin’s immune response to light exposure. Similar sun-seeking behavior can happen in pets as well. Although hair protects many animals from sunlight, not all parts of the body are covered with sufficient hair to shield the underlying skin from solar damage.

The armpits, abdomen, skin in front of the ears, nose and muzzle are vulnerable in all pets; short-coated breeds and lighter pigmented individuals are particularly at risk. Even indoor-only pets can have problems with too much sun.  Although double-paned and newer glass windows can prevent most harmful effects of the sun, older glass windows do not block all types of potentially damaging solar radiation.

Too much sun can cause problems ranging from burns to cancer. Dogs and cats can get precancerous lesions called actinic keratoses, which can then progress to skin cancers such as squamous cell or basal cell carcinoma. Some dogs can develop tumors of the blood vessels called hemangiomas.

The best protection strategy in humans and animals is avoidance of the sun, particularly when radiation levels are the highest, between 10 AM and 4 PM.  Early morning and evening are the safest times for long walks or outdoor play.  A penned enclosure with shade cloth can be effective in treeless yards.

Some companies make “sunwear” for dogs, designed for solar protection. Human clothing can be adapted for our pets as well, although few dogs or cats tolerate hats.

Sunscreen use in humans has increased along with awareness of the damaging effects of too much sun. However, sunscreen is typically not applied appropriately or at high enough frequency to be effective.  The use of sunscreens may impart a false sense of security, leading people to spend more time in the sun at the most dangerous times of the day.  Veterinary sunscreens are available; human zinc-free sunscreens designed for use in infants can be alternative.

What Is The Spleen?

What is the spleen?

The spleen is a tongue shaped organ of the abdomen that acts as a reservoir for blood as well as filters the circulating blood.  It removes and recycles old red blood cells and attacks any blood borne pathogens like bacteria and parasites commonly associated with tick borne diseases via its large volume of lymphoid tissue (immune system).

Canine and feline spleens may distend and contract to help increase circulating blood volume and this can be influenced by anesthetic medications.  Spleens can be surgically removed without significant compromise to our pets’ long term health.

When does an enlarged spleen need to be further evaluated?

Patients may be presented to a veterinarian for a variety of non-specific signs of illness resulting from an enlarged spleen or splenic mass.  Vomiting, inappetence, weight loss, low energy, pale mucus membranes (gums), or simply enlargement of their abdomen can be symptoms that a pet exhibits when there is a problem with their spleen.  A veterinarian may incidentally find a mass when palpating the abdomen on yearly health exams.  Splenic masses can be caused by a variety of diseases ranging from infection (abscess) to a tumor (benign vs. malignant), which is more common.  Additionally, systemic diseases or malpositioning of the spleen may also increase its overall size. Diagnostic tools veterinarians have to differentiate these multitude of diseases are x-rays (radiographs), abdominal ultrasound, CT (computed topography), and sometimes MRI (magnetic resonance imaging).

1. Normal Spleen Radiograph

Radiographs give an excellent over-view of a patient’s abdomen and help to appreciate the overall size and shape of organs in comparison to the rest of the patients’ abdominal organs.  Abdominal ultrasound is superior at looking at the inside architecture of abdominal organs and can determine different characteristics of the enlarged spleen or splenic mass that help guide treatment recommendations and provide tentative prognoses.

2. Enlarged Spleen Radiograph

3. Normal Spleen Ultrasound

The abdominal ultrasound can determine the location of a mass and whether it is associated with the spleen.  Unfortunately, tumors of the spleen are reported to be a malignant cancer more often than not.  Because tumors of the spleen typically arise from the blood vessels (hemangiosarcoma), the spread or metastasis of the tumor has already occurred at time of diagnosis and or the tumors have ruptured and are actively bleeding into the patients’ abdominal cavity.  The liver is commonly affected with metastasis of splenic cancers, so evaluation with an abdominal ultrasound can help determine if this is apparent.  Additionally, bleeding into the abdomen from the spleen can be assessed and diagnosed via abdominal ultrasound.

4. Splenic Mass Ultrasound

What are common tumors of the spleen?

The most common splenic tumor is the malignant cancer, hemangiosarcoma.  This is a tumor of the blood vessels and as a result can easily rupture and cause life threatening bleeding.  Unfortunately, diagnosis of a hemangiosarcoma requires tissue analysis (histopathology), which is typically completed with surgical removal of the spleen, and stops the active bleeding.  There are less concerning tumors of the spleen that can also rupture (hemangioma, hematomas) that once removed surgically are curative and should not affect your pet’s long term survival.  Other tumors include different sarcomas, lymphoma, and mast cell tumors (more commonly in cats).  Non-tumor diseases like infection (abscess) and splenic torsion (strangulation of splenic blood vessels), are also causes of an enlarged spleen, necessitating surgery.

What does surgery entail for your pet if they have been diagnosed with a splenic tumor or general enlargement of the spleen?

Canine and feline patients will be assessed thoroughly by a veterinarian to ensure they are stable and safe to proceed with surgery.  This typically entails complete blood work, chest x-rays, and blood type check to ensure that if a blood transfusion is needed the hospital is prepared.  Your family member will be put under general anesthesia and will have their abdomen clipped of hair for sterility purposes.  Through a long incision, the entire abdomen and abdominal organs will be thoroughly evaluated for abnormal changes.  Samples of other organs will be safely obtained if deemed necessary.  The spleen will then be isolated and removed.  Often using special vessel sealing and incising devices, LigaSure, adopted from human surgeons, will be used to safely and quickly remove the spleen stopping any current bleeding and obtaining the necessary tissue for analysis (histopathology).

5. Multiple Splenic Tumors

How long does my pet need to recover from surgery?

Following their successful recovery from anesthesia, your pet will need to be in the hospital for a couple of days for close monitoring.  Blood transfusions can be common for patients that were bleeding from their masses before surgery.  Bleeding after surgery is unlikely, but possible, and this will be closely monitored.  Heart arrhythmias (irregular heart rhythm and activity) can be present that may need to be treated with medications.  As your pet improves, they will be transitioned to oral medications and prepared to discharge home for further recovery.  Typically patients need 2 weeks of strict exercise restriction and rest.  Monitoring their incision for signs of infection and supportive care with medications are the mainstay of their at home recovery.  After 2 weeks of a successful recovery, they are allowed to go back to normal activity.

If my pet is diagnosed with hemangiosarcoma, what is their prognosis?

Unfortunately, hemangiosarcoma is a very serious and debilitating cancer.  The average patient following a diagnosis of splenic hemangiosarcoma will only have a life expectancy of around 3 months.  Chemotherapy may extend survival with hemangiosarcoma and we advise meeting with one of our oncologists after a diagnosis of hemangiosarcoma to see if further treatment would be appropriate for you and your pet.  Chemotherapy is well tolerated in our canine and feline patients.  They receive intermittent injections or pills on an outpatient basis and only a small percentage (less than 15% will experience nausea, vomiting, or low white blood cells requiring antibiotics.  There are ongoing studies and trials occurring nationwide trying to find drugs that could improve survival following a diagnosis of hemangiosarcoma.

Shoulder Instability

What is shoulder instability?

Shoulder problems are one of the most common causes of front leg lameness in dogs.   Shoulder instability (SI) describes a wide range of soft tissue injuries to the ligaments, tendons and muscles of  the shoulder.  SI affects all sizes and breeds of dogs.  Many athletic (esp. agility) dogs are affected, but more sedentary pets are also affected.  At this time it is not clear if the condition is purely traumatic or a result of degeneration of the tissue.  Typical patients are middle aged, but SI can affect all ages.    SI most commonly affects a single leg, but a small percentage of pets have both shoulders affected.

How is SI diagnosed?

The starting point for diagnosis of SI is a thorough orthopedic and neurologic examination.  Once pain has been localized to the shoulder, radiographs (x-rays) are typically the next step.  It is important to note that radiographs typically do not diagnose shoulder instability, but are used to look for other causes of shoulder lameness (fractures, cancer, cartilage flaps or arthritis).  Once radiographs are taken, the next step is generally a sedated measurement of shoulder stability (shoulder abduction angle) (Figure 1).  Further diagnostic steps are dependent on this angle measurement.  Often, ultrasound is used to evaluate the soft tissues of the shoulder.

Fig. 1: MRI demonstrating normal biceps.

In some cases, MRI (figure 2) may also be required to completely evaluate the extra-articular structures and determine the best treatment options.  Cost may be rate limiting for these diagnostic tests.  In most cases, exploratory arthroscopy must be performed to definitely diagnose the problem.

How do you treat SI?

Medical management: A variety of treatment options exist for SI and depend on the type and degree of instability present.  For early cases, medical management may be the first step.  Patients are sedated and fluid sampled from the affected joint.  Long acting steroids (depomedrol 20-40mg) may be placed in the joint to decrease inflammation and pain.

Fig. 2: Hobbles by Dogleggs.com

Patients will often be placed in a special type of hobble to limit shoulder motion during the healing phase (figure 3).  Physical therapy is very important after the initial healing phase to regain shoulder strength.  Treatments such as laser, therapeutic ultrasound and shockwave are often used during this phase of treatment.

Platelet rich plasma (PRP) is a new therapy that involves spinning down the patient’s own blood and harvesting the platelet portion of the plasma.  This can be injected into the joint and may help stimulate the healing process.  Objective evaluation of these therapies is lacking. Water therapy (swimming and water treadmill) can be very valuable with both surgically and medically managed SI in dogs.

Fig. 3: Tightrope, minimally invasive shoulder reconstruction

Weight control is also very important.  Overweight patients should be placed on appropriate calorie or metabolic diets.  Medical management can result in good outcomes in about 2/3 of appropriately selected patients. Dogs with significant laxity (abduction angles >60 degrees) rarely resolve with medical management only.  Surgical management:  surgical management is the treatment of choice for more severe instability cases or in those that medical management has failed.  A variety of surgical stabilization procedures are available and depend on the exact cause of SI.  Minimally invasive surgical options are always considered.  Ligament replacement surgery is often the surgical treatment of choice for SI (figure 4).  Successful outcomes with surgery approach 90%.  Patients can return to full function, but it may take 6-12 months to completely regain muscle strength.  Complications with surgery are uncommon, but include infection, failure of the repair or persistent lameness.

Portosystemic Shunts

What is a portosystemic shunt?

A portosytemic shunt (PSS) is an abnormal blood vessel that carries blood intended to flow through the liver and diverts it away from the liver to the general circulation. The portal system is a special network of blood vessels that collect blood and metabolic byproducts from many of the abdominal organs and allows passage of that blood through the liver to remove some harmful substances and derive nutrition from others. When the portal system is bypassed by a shunt, the blood flows unfiltered back to the heart and is circulated to the body, including the brain.

Portosystemic shunt (arrow) as seen at surgery located in the region of the stomach and spleen.

Diverse bodily functions can be impaired. Affected animals can show symptoms including:

  • Decreased alertness and appropriate reaction to surroundings most often seen following a meal(varying in severity from a puppy that seems “quiet” or “tired” to seizure activity)
  • Decreased growth
  • Abnormal urination (urinary stones can form in animals with PSS)
  • Various gastrointestinal symptoms (vomiting, poor appetite)
  • Drooling (a common symptom in cats with PSS)

PSS is seen in dogs and cats, but the majority of cases seen and treated are in dogs. The abnormal vessel is most often congenital (present at birth), and the symptoms are usually seen fairly early in life.  PSS in its most common form tends to affect small and toy breeds, although some large breed dogs can also be affected.

How is a portosystemic shunt diagnosed?

Most patients are diagnosed due to a concern for one or more of the symptoms above, but some PSS are discovered because of abnormalities in routine blood testing (such as done during a puppy or annual exam). Once there is suspicion for PSS, a blood test called a bile acids test is often performed. This is a test of general liver function, but patients with PSS will have abnormally high bile acid levels. This finding will prompt an imaging test to diagnose the presence of the abnormal vessel as well as its appearance. PSS can take many forms, so it can be important to know the shunt configuration before deciding on the nature of treatment. There are other conditions which resemble PSS on diagnostics without the presence of an abnormal vessel.

The most common methods of diagnosis are ultrasound and computed tomography (CT). Ultrasound, in experienced hands, can detect most PSS and give information about the size and location of the aberrant vessel. There is a fair amount of variation in the connection points of the abnormal vessel from one patient to another, so a “roadmap” is key to pre-surgical planning. CT is a highly useful tool for PSS diagnosis and gives detailed visual anatomical information which can be reconstructed into a 3-D format. Whether ultrasound, CT or both are used, the entire abdomen is assessed to screen for other abnormalities, including bladder stones.

How do you treat portosystemic shunts?

Most PSS are single, fairly large vessels coursing outside of the liver tissue (extrahepatic). These will be discussed. Intrahepatic shunts are located within the liver tissue allowing the blood to bypass filtration and flow directly to the heart without passing through the portal system.

Sometimes multiple shunts can be seen. These are usually not congenital, but acquired later in life and are associated with underlying liver disease and are not amenable to surgical treatment.

Medical Management

Once a single extrahepatic portosystemic shunt is diagnosed medical management should be initiated.  This treatment will help control the symptoms previously described, but does not reroute the abnormal blood flow and surgery is ultimately recommended in most patients.  Medical management often consists of the use of medication to decrease the absorption of ammonia by the intestines, antibiotics, low protein diets, and anti-seizure medications.

Lactulose can decrease the amount of ammonia absorbed by the intestines during the breakdown of proteins. Ammonia contributes to the abnormal neurologic signs in dogs with PSS.

Survival times reported with medical management range from five months to more than seven years following diagnosis.  In animals with PSS, medical management is generally recommended for a minimum of two weeks prior to undergoing any form of anesthesia for diagnostic information or surgical treatment.Surgical Management

Gradual closure of PSS is considered the treatment of choice in most animals due to improved outcomes. Several different surgical techniques are available to cause gradual occlusion of the abnormal blood vessel, including the use of cellophane, ameroid constrictors, hydraulic occluders, and coil embolization.

For the majority of these techniques to be performed, the abdominal cavity must be opened along the midline to allow exposure of the liver.  The abnormal vessel is located and a device is applied around the vessel where the blood flow enters general circulation.  Cellophane bands and ameroid constrictors stimulate scar tissue formation when applied allowing gradual closure of the vessel, whereas a hydraulic occluder can be gradually inflated or deflated through injection of a port placed under the skin at the time of surgery.

Ameroid constrictor placed around PSS.

Alternatively, coil embolization is performed using large catheters which are inserted through the blood vessels of the neck.  Coils are inserted from within the blood vessel and gradually result in clotting and closure of the abnormal vessel.  This technique is most frequently used with intrahepatic shunts.

A radiograph demonstrating coil embolization with a stent in the caudal vena cava and coils at the location of the entering anomalous vessel.

If any bladder stones were noted on imaging prior to surgery, these can be removed during the same procedure through an incision into the bladder (cystotomy). Spay or neuter can also be performed.

What are the possible complications of surgery?

Following surgery your pet is monitored closely in the ICU.  Complications that can be noted following surgery include:

Hypoglycemia: Some animals will have low blood sugar in the immediate postoperative period.  If this occurs dextrose can be given in a diluted form with IV fluids.  This condition usually resolves when the pet is alert enough to eat solid foods.

Portal hypertension: Reported in 2 – 14% of patients. This complication occurs when the shunting vessel closes too quickly.  Because of the presence of the shunting vessel, the portal vein is often smaller than usual.  When blood is redirected to flow through the portal vein time is needed for this vessel to accommodate.  If too much blood is directed through the portal vein too quickly, the blood pressure in this vessel elevates rapidly causing back pressure into the intestines.  If left untreated portal hypertension ultimately results in death.  Symptoms of hypertension include abdominal pain, distension, and severe diarrhea.  If recognized immediate return to surgery to adjust the surgical site is recommended.

– Seizures or abnormal neurologic signs: Reported in 3 – 18% of dogs and 8 – 22% of cats.  Most commonly this is seen within the first three days following surgery.  The cause of this is unknown.  If observed treatment with IV fluids and benzodiazepines is initiated.  If neurologic abnormalities persist, general anesthesia for 12 -24 hours is attempted until cessation of seizure activity is noted; some animals may require 72 hours of anesthesia.  The prognosis for animals with postoperative seizures is often unfavorable, though recovery is possible.

Return of clinical signs: This can occur if a shunting vessel fails to close completely or if it closes too rapidly leading to the formation of additional shunting vessels.  Additional surgery may be recommended if either of these scenarios occur.

What is the prognosis for my pet after surgery?

Mortality rates in dogs following surgery for PSS is <10%, varying somewhat with the technique used to occlude the shunting vessel.  Mortality rates are higher in animals with postoperative neurologic dysfunction or evidence of portal hypertension.

Long-term, animals undergoing surgery for PSS have good to excellent outcomes in 80-90% of cases.

What kind of postoperative care will my pet need?

Following surgery, most pets are hospitalized for 48 – 72 hours to monitor for postsurgical complications and to administer pain medications.  Following discharge from the hospital, a specialized low protein diet is continued until blood work shows evidence of improved liver function.  Lactulose may also be continued to help reduce abnormal neurologic signs while the liver recovers.