Portosystemic Shunts

Congenital Portal Shunts are due to a defect in the blood circulation around the liver. Instead of blood entering the liver to be detoxified, the liver is bypassed. The liver usually eliminates toxins derived from the gut. With a porto-systemic shunt, there is a bridging between the veins around the liver and so the toxic material bypasses the liver, causing an elevation of ammonia in the circulation.


This defect may be within the liver (intrahepatic) or occur outside of the liver (extrahepatic) - most are single vessels.

Shunts can be congenital (present at birth) or acquired. Acquired shunts can develop subsequent to portal hypertension (high blood pressure); typically they are multiple in nature. This occurs due to a lack of valves in the portal vein, permitting circulatory accommodation through the shunt. Portal hypertension is usually associated with liver scarring or cirrhosis.

The shunt may lead to episodic development of hepatic encephalopathy (seizures or bizarre behavior) associated with ingestion of high protein food, and administration of certain drugs.

Another effect of the shunt is the development of bladder stones due to inability of the liver to metabolise uric acid from the blood.

SYSTEMS AFFECTED

Nervous system signs include episodic hepatic encephalopathy (seizures).
Gastrointestinal signs are intermittent inappetence; vomiting; diarrhea; pica; drooling in cats.
Urogenital signs bladder stones and or large kidneys

GENETICS

Basis unknown
Breeds predisposed include miniature schnauzers; Irish wolfhounds; Old English sheepdogs; cairn terriers; Yorkshire terriers

INCIDENCE/PREVALENCE

Incidence is greatest in purebred dogs and mixed breed cats
Especially common in Yorkshire terriers

CLINICAL SIGNS

Episodic seizures or disorientation (hepatic encephalopathy) may be noted.
Affected cats may drool. This may be initially confused with an upper respiratory infection based on the display of increased salivation.
Initial signs usually noted at initial feeding of puppy or kitten food and stunted growth is common

SYMPTOMS

CNS Signs: Episodic weakness, pacing, disorientation, head pressing, blindness, behavioral changes (aggression, vocalization, hallucinations), seizures, coma
Gastrointestinal Signs: inappetence, vomiting, diarrhea
Urinary Signs: bladder stones
Congenital disease –The pets may have a normal appearance or have stunted stature, hepatic encephalopathy, golden or copper irises in non- blue-eyed and non-Persian cats.

DIFFERENTIAL DIAGNOSES

CNS signs -Other rule outs include infectious disorders (e.g., FIP, canine distemper, toxoplasmosis, FeLV-related infections); toxicities (e.g., lead, mushrooms, recreational drugs); hydrocephalus; epilepsy; metabolic disorders (e.g., severe low blood sugar).
Gastrointestinal signs—bowel obstruction; dietary indiscretion; foreign body ingestion; inflammatory bowel disease
Urinary tract signs—bacterial urinary tract infection; stones

DIAGNOSIS

Lab Work

CBC/Biochemistry: low BUN, creatinine, glucose, and cholesterol common; liver enzyme activity variable (ALP usually high in young patients owing to bone isoenzyme); bilirubin normal with congenital but may be high with acquired shunts.
Urinalysis: Decreased urine specific gravity (inability of kidneys to work properly) and crystals in the urine.
Total serum bile acids—sensitive indicators; random fasting values may be within normal reference range; 2-hr postprandial (post feeding) values markedly high (usually > 100 mmol/L)
Blood ammonia values—sensitive indicators; less reliable than total serum bile acids because of analytic problems
Ammonia tolerance testing—more reliable than random ammonia values; samples cannot be stored, frozen, or mailed for analysis.

Imaging

Abdominal Radiography: Small liver, Large kidneys, Bladder stones
Injecting radiographic contrast media into a mesenteric or spleenic vein. This is the test of choice, but is technically difficult.
Abdominal Ultrasonography: Subjective estimation of small liver, hypervascularity, and observation of the shunting vessel. Color-flow Doppler—assists in shunt localization. Intrahepatic shunts are most easily imaged.


Acquired Shunts

Liver size depends on underlying cause.
Abdominal fluid is easily detected.
Ammonium urate calculi (stones) in the kidney or bladder

TREATMENT

Eliminate causal factors—dehydration; elevated kidney toxins; gastrointestinal bleeding; high- protein foods; infection (urinary tract, other); treatment with certain drugs

Protein-restricted diet—dogs: dairy and soy protein may perform better than meat and fish proteins; cats: require balanced, meat-based protein.

Increase dietary protein tolerance by concurrent treatment with lactulose (0.5–1 mL/kg PO q8–12h; dose based on production of two to three soft stools daily), metronidazole (7.5 mg/kg PO q8– 12h), and/or neomycin (22 mg/kg PO q12h).

Cleansing enemas with warmed isotonic fluids— until free of feces
Retention enemas—15 mL/kg; with lactulose (1:2 dilution with water) and neomycin (10–15 mg/kg)

SURGICAL CONSIDERATIONS

Surgical ligation with congenital disease

Goal: total ligation vessel; often only partial ligation can be performed safely and surgical assessment of extent of ligation may be inaccurate.

Hepatic encephalopathy signs must be resolved before surgery. Intrahepatic shunts are most difficult to ligate.

This article was donated by the Columbia Animal Hospital. For further information please visit http://www.petshealth.com/

The Canine Weight Loss Drug

The FDA in the USA approved a drug over a year ago, on 5th January 2007, that claims to be a useful weapon in the fight against canine obesity. Slentrol (dirlotapide), manufactured by Pfizer, is aimed at dogs that are clinically obese rather than those that are just slightly overweight. Could your dog be a candidate for this new drug? Here we look at what Slentrol is and how it works.

Indications

Slentrol Oral Solution is indicated for the management of canine obesity. With canine obesity on the increase globally, many veterinarians see it as the most important health issue facing pets today. Though the approval of this drug has been welcomed by the veterinary community, they are also stressing that it must be used together with an appropriate weight loss diet and exercise program to be effective. It is not a cure for obesity, once the dog stops taking the medication, the obesity will return unless lifestyle changes are enforced.

Presentation

Slentrol is a solution formulated at a concentration of 5 mg/ml of dirlotapide for oral administration to dogs. It can be administered directly into the dogs mouth or on a small amount of food, with a meal or at a different time of the day.

Slentrol is available in 20, 50 and 150 ml bottles.

Slentrol should be stored in its original container at room temperature, 15 to 30 degrees centigrade.

How it works

Dirlotapide is a selective microsomal triglyceride transfer protein inhibitor that blocks the assembly and release of lipoprotein particles into the bloodstream (via the lymphatic system).
The exact mechanism for producing weight loss is not completely understood, according to the FDA, but seems to result from reduced fat absorption and sending a feeling to the dogs brain of being full.If used correctly, Slentrol helps to achieve weight loss of at least 2.8% body weight per month.

Dosage

Slentrol is given dosed in 2 phases:

1) Weight loss phase
2) Weight management phase

Weight loss phase

The initial dosage of Slentrol is 0.01 ml/kg (0.0045 ml/lb) body weight, administered once daily orally for the first 14 days.

After the first 14 days of treatment, the dose should be doubled to 0.02 ml/kg (0.009 ml/lb) body weight, administered once daily for the next 14 days.In subsequent months of therapy, the recommended dose varies for each individual dog and the dose volume must be specifically calculated each month, based on percent of weight lost during the previous month of therapy.

Dogs should be weighed monthly on accurate weighing scales at your veterinary clinic and the dose volume adjusted every month, as necessary, to maintain a target percent weight loss of at least 0.7% per week.

Weight management phase

A 3 month weight management phase is recommended to successfully maintain the weight loss achieved. During the weight management phase, the veterinarian and the pet owner should together establish the optimal level of food intake and physical exercise required.
When Slentrol is discontinued, the daily amount of food offered and physical activity should be continued as established during the weight management phase. Reverting to previous food intake or exercise levels at this point can contribute to a regain of some or all of the weight loss that has been achieved.

What if my dog is not losing any weight despite after 1 month of therapy?

The dose volume (number of ml administered each day) should be increased by 100%, resulting in an increase of the dose volume to 2 times the dose administered during the previous month. Only perform a 100% dose increase once during treatment after day 14.

What if my dog is still not losing weight after increasing the dose?

If additional dose increases are necessary in the following months, the dose volume should be increased by 50%, resulting in an increase of the dose volume to1.5 times the dose administered the previous month of dosing.

The dose should not exceed a maximum daily dose of 0.2 mL/kg (0.09 mL/lb), based on the dogs current body weight, during any part of treatment.

Precautions

Prior to starting treatment with Slentrol, all dogs should undergo a thorough history and physical examination by a veterinarian. This should include laboratory tests to screen for underlying conditions that can cause weight gain, such as Cushings syndrome and hypothyroidism.

The safety of Slentrol use in dogs has not been evaluated beyond 1 year.

Safety in breeding, pregnant or lactating dogs has not been established.

Slentrol has not been evaluated in dogs less than 1 year of age.

Slentrol is not recommended for dogs receiving long term corticosteroid therapy or dogs with liver disease.

Slentrol must not be used in cats due to the risk of causing hepatic lipidosis in obese cats.

Slentrol causes serious adverse reactions in humans such as abdominal distention, abdominal pain, diarrhea, flatulence, headache, nausea and vomiting. Keep well out of reach of children.

Adverse Effects

Vomiting / Diarrhea.

Almost 1 in 4 of dogs placed on Slentrol therapy experience occasional episodes of vomiting and diarrhea. In most cases these episodes lasted for one or two days before clearing up. Vomiting occurs most often during the first month of treatment or within a week of a dose increase. If vomiting is severe or lasts longer than 2 days, consult your veterinarian and have your dog examined.

Inappetance

Of course this is the aim of the therapy to an extent, but if during therapy a dogs food consumption is excessively reduced for several consecutive days, stop giving Slentrol until the appetite returns (usually 1-2 days) and then resume dosing at the same volume as before.

Lethargy

Further information for the pet owner

Achieving your weight loss target for your pet requires a great deal of motivation. It is important to maintain an active and on-going line of communication with your veterinarian for the duration of therapy, until the medication has been discontinued and beyond. Above all else, veterinary weighing scales are likely to be far more accurate than your average human bathroom scales, and it is important to get your measurements correct so you can chart your progress and adjust the dose as necessary.

Remember that successful long-term weight management requires changes that extend beyond the period of drug therapy. To maintain the weight lost when treated with Slentrol, the adjustments in dietary management as well as exercise that were begun as part of the overall weight loss program must be continued by the owner after drug therapy is discontinued. The appetite suppression caused by Slentrol only lasts for 1 to 2 days after stopping treatment, so unless food is limited the dog will gain weight again.

Author bio: Matthew Homfray is a veterinarian and online pet advisor at FREE pet Q&A service http://www.televets.com

A Healthy Diet for Dogs

Every owner these days seems to have their own ideas on what constitutes a healthy balanced diet for their dog. How many of them are reliably imformed though? The following questions are designed to critically assess your dogs diet. Please read them, for your dogs sake.

1) How many times a day do you feed your dog?

There is no set rule for adult dogs but the general consensus is that twice a day is a sensible amount. Some owners feed once a day, some three times a day. How much your dog is fed is far more important than how often really, but it is useful to set guidelines nevertheless. The reason many experts suggest twice a day rather than once a day is that once a day feeding encourages the dog to gorge his or her food as he or she is so hungry, having last had a meal a full 24 hours ago. Eating too quickly can cause reflex regurgitation or vomiting. Also it has been theorized that deep chested large breed dogs are more likely to suffer from a twisted stomach (gastric dilatation and volvulus), a life threatening condition, if they are fed one large meal daily rather than two smaller meals.

Clearly more active dogs will burn far more calories than others but these variables are best reflected in portion size rather than frequency. Some dogs with medical conditions may benefit from multiple meals of smaller portions, for example those recovering from gastroenteritis. Puppies must be fed more often than adult dogs as they have a higher metabolic rate, around 4 times a day from weaning to around 5 months old, then drop down to 3 times a day until 7 months old, then down to twice a day thereafter.

2) Is your dogs diet manufactured specifically for dogs or do you give human food or food from the butchers?

There is a misconception around that human food is higher quality than dog food, and therefore better for them. This is by and large nonsense. Reputable dog foods are formulated after extensive trials by pet food companies to provide the mixture of protein, carbohydrate and fat that suits canine physiology best. Dogs on balanced dog food diets do not get nutritional deficiencies but dogs on human food do. Certain human titbits can play havoc with your dogs digestive tract, chocolate being a prime example.

Your dog need ingest nothing other than a complete dog food and water to have a complete and balanced diet. Remember, dogs do not need variety in their diet! They are perfectly happy having the same boring looking meal every day! So keep it simple and safe, feed your dog either a complete dog food (dry or tinned, dry is better for their teeth) or standard dog biscuits and tinned dog meat together. Of course human leftovers every now and again or a bit of tripe or heart from the butcher is fine, but do not make it the day to day diet.

3) Which is the best dog food to choose?

There are so many different brands of dog food on the market, the best one is basically a matter of opinion. Certainly palatability is a factor, there is no point in purchasing a particular food if your dog cannot stand it, although this is occasionally a necessity in dogs with food allergies, for example. Rather than recommending you a specific brand, we suggest that you choose one which adheres to the criteria below.

Dog foods labeled as complete and balanced must meet standards established by the Association of American Feed Control Officials (AAFCO), either by meeting a nutrient profile or by passing a feeding trial. There are now two separate nutrient profiles for dogs - one for growth (puppies) and one for maintenance (adults). Maximum levels of intake of some nutrients have been established for the first time because of the concern that overnutrition, rather than undernutrition, is a bigger problem with many pet foods today. The standards include recommendations on protein, fat, fat soluble vitamins, water soluble vitamins, and mineral content of foods. If you are prepared to get technical, you should choose a food that comes closest to AAFCO recommendations.

In summary, consider the following points.

Choose a food that suits your dogs age, breed and overall health. Most big pet food companies will have different foods for small vs large breeds, and puppies vs adults. Dogs with medical conditions may be recommended special prescription diets.

Choose a food that come closest to AAFCO recommendations.

The ingredients contains the truth about a particular food. Everything else is there only for marketing purposes.

There are no legal and scientific definitions for the terms premium, super premium, quality, or natural.

Use dry matter numbers to evaluate and compare foods.

The source of ingredients (e.g. animal vs vegetable) does not matter, except in the case of food allergies.

Avoid supplementation. All commercial dog foods have more than enough protein, fat, vitamins, and minerals. Too many minerals can lead to severe skeletal problems in growing dogs.

Feeding your dog a good food incorrectly can lead to significant problems. For example, overfeeding puppies can lead to serious skeletal problems. Neutered dogs require portions 20% smaller than unneutered dogs or they will put on weight.

4) How many times a day do you give your dog treats?

It is hard to resist those puppy dog eyes begging you for a little piece of what you are eating. Indeed treats promote a special bond between you and your dog and it gives such pleasure when they have a delicious morsel to savor. The key word is MODERATION. If you are giving your dog regular treats, you must subtract this amount from the portion given at meal time to maintain a appropriate calorie intake. As a rule of thumb the amount of treats should never exceed 10% of your dogs daily food intake. It is far easier to make your dog obedient if you reserve treats for rewarding good behavior rather than just giving them willy nilly, where they become meaningless.

5) What do your dogs treats consist of?

Quality dog treats are usually far healthier and lower in calories than table scraps. Many dogs are fed scraps habitually from the table while families are eating, particularly by children. This only encourages further begging and feeding with often unsuitable high calorie treats which are forgotten about when it comes to measuring the dogs daily portion(s).

Matthew Homfray is one of the online experts at free pet Q&A service Televets. To ask a pet question visit http://www.televets.com