Liver shunts, also known as portosystemic shunts (PSS), are a relatively common condition in dogs and cats, especially certain breeds, where blood vessels bypass the liver, preventing it from properly detoxifying the blood. This article provides a detailed guide to dietary management for canines with liver shunts, incorporating information from veterinary experts and practical feeding strategies.
Understanding Liver Shunts
Liver shunts occur when abnormal veins divert blood from the intestines and other organs away from the liver, directly into the systemic circulation. This "untreated" blood contains high levels of ammonia and other toxins, which can lead to seizures, hepatic encephalopathy (HE), and the formation of urate bladder stones. Both genetic defects and liver damage can cause shunts. Congenital PSS is the most common congenital vascular disorder.
Congenital vs. Acquired Shunts
Congenital shunts are more prevalent in dogs and are often seen in purebreds such as Irish Wolfhounds, Golden Retrievers, Yorkshire Terriers, and Maltese. In cats, domestic shorthairs are more commonly affected. These shunts typically involve a single abnormal vessel. Acquired shunts, on the other hand, usually consist of multiple vessels and develop secondary to chronic liver disease or damage, such as that caused by aflatoxin poisoning, leading to portal hypertension.
The Role of the Liver
The liver is a vital organ involved in numerous metabolic functions, including protein, fat, and carbohydrate metabolism, vitamin and mineral storage, and the detoxification and excretion of nitrogenous waste. It plays a crucial role in ammonia detoxification through the urea cycle. In patients with PSS, inadequate ammonia detoxification can lead to hyperammonemia, causing neurologic signs and muscle atrophy.
Treatment Options for Liver Shunts
The preferred treatment for large, portosystemic shunts is often surgery to reduce the size or completely close the abnormal vein(s). However, surgery may not always be feasible or fully successful, necessitating medical management. Nutritional support plays a crucial role in managing animals with progressive hepatobiliary disease and hepatic insufficiency, especially those prone to hepatic encephalopathy.
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Medical Management
Medical management includes dietary adjustments, intestinal ammonia trapping with fiber, prebiotics and probiotics, lactulose as a laxative, and potentially seizure control medication. For patients with urate crystals, additional medications and urine pH modifiers may be required.
Dietary Management: The Cornerstone of Liver Shunt Treatment
Dietary modification is a critical component of managing liver shunts, aiming to reduce the production of toxins and support liver function. The primary goals of dietary management include:
- Reducing protein intake to minimize ammonia production.
- Providing highly digestible protein sources.
- Meeting energy requirements to prevent muscle loss.
- Supplementing with essential nutrients and vitamins.
Key Dietary Principles
Diets for animals with hepatobiliary disease should be easily digestible, highly palatable, and calorie-dense. Frequent, small meals are recommended to optimize food digestion and assimilation. It is essential to restrict protein content only in patients with clinical signs of HE or ammonium biurate crystalluria.
Protein Restriction: When and How
A diagnosis of liver disease does not automatically necessitate protein restriction. In fact, protein restriction can be detrimental in some animals, such as cats with hepatic lipidosis (HL) or animals with chronic necroinflammatory liver disease without acquired portosystemic shunts (APSSs) or HE. Protein restriction is appropriate when HE is suspected, ammonium biurate crystalluria is observed, or portosystemic shunting is confirmed.
For animals with HE, the initial protein restriction should be around 2.5 g protein/kg (< 5 g protein per 418.4 kJ [100 kcal] diet) for dogs and 3.5 g protein/kg (< 7 g protein per 418.4 kJ [100 kcal]) for cats. The response to treatment should be assessed through historical, physical, and clinicopathologic evaluations to guide further adjustments.
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Protein Quality and Source
Altering the type and quality of protein intake can significantly improve the quality of life for dogs with HE. A high energy:nitrogen ratio should be maintained to optimize dietary protein utilization. Dairy and vegetable protein sources are often recommended due to their favorable amino acid profiles.
In dogs, dairy protein sources like whole milk, yogurt, cottage cheese, and cheddar cheese are good options. Vegetable proteins, such as soy, are also beneficial. In cats, a meat-based protein source is essential, but protein-restricted feline commercial prescription renal diet foods that meet the requirements for arginine, taurine, and other essential nutrients can be used.
Fat and Carbohydrates
There is generally no need to restrict dietary fat in animals with hepatobiliary disease unless they have specific conditions like chronic extrahepatic bile duct obstruction (EHBDO) or gallbladder mucoceles. Fat ingestion is important for providing essential fatty acids and fat-soluble vitamins. Complex carbohydrates are beneficial because they are a good source of energy.
Homemade Diet Recipes for Liver Shunts
Integrating custom recipes into medical programs for dogs with liver shunts can be a beneficial approach, especially when commercial diets are unappealing or insufficient.
General Guidelines
When preparing homemade diets, it is essential to work with a board-certified veterinary nutritionist to ensure the diet is balanced and meets the dog's specific needs. A typical calorie distribution for liver shunt patients is:
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- Protein: 14%
- Fat: 38%
- Carbohydrates: 48%
These recipes contain less meat protein than normal diets (24%-52%), helping to reduce symptoms associated with liver shunts. They also contain the minimum amounts of copper recommended by veterinary experts for liver conditions resulting from copper toxicity.
Sample Recipe
Here is an example of a homemade diet recipe for adult dogs with liver shunts:
Ingredients:
- 200 grams of cooked whole egg, chicken, or duck (no shell) OR low-fat cottage cheese (2% fat)
- 50 grams of boneless raw meat (skinless chicken thigh or breast, skinless turkey breast, boneless drumstick, skinless duck breast, turkey mince (6% fat), pork mince, shoulder or loin (5% fat), or boneless rabbit meat)
- 500 grams of starchy vegetables and/or cooked grains (sweet potato, potato, oats, brown rice, quinoa, or wholemeal pasta)
- 150 grams of colorful vegetables and fruit
- 100 grams of kale (fresh or frozen) OR 3 tablespoons of ground sesame seeds OR 33 grams textured vegetable protein (TVP; soak before use)
- 3 mL omega-3 rich oil (fish oil, salmon oil, krill oil, or marine algae oil)
- 2 teaspoons of omega-6-rich oil (hempseed oil, walnut oil, rice bran oil, pumpkin seed oil, canola oil, or sesame oil)
- 12 grams of CompleteMe Hepatic Canine (a supplement to ensure nutritional balance)
Directions:
- Gently pan-fry the diced meat with 20-30 mL water until cooked. Omit this step if using raw meat.
- Steam or microwave the chopped vegetables until very soft.
- Cook any grains or pasta until very soft, as per the manufacturer's instructions.
- Combine the meat (including liquid from pan), cooked egg or cottage cheese, cooked vegetables, fruit, kale/seeds/TVP, and oils, and mix well.
- Allow to cool, then add 12 grams of CompleteMe Hepatic Canine and mix again.
- Portion and refrigerate or freeze as desired.
Important Considerations for Homemade Diets
- Balance and Completeness: Ensure that the diet meets all AAFCO and NRC daily nutrient requirements. The Healthier Homemade Liver Shunt program includes taurine supplementation for heart health.
- Veterinarian Consultation: Always consult with a veterinarian or a board-certified veterinary nutritionist before starting a homemade diet.
- Ingredient Restrictions: Be aware of any conflicting dietary restrictions due to other health conditions (e.g., inflammatory bowel disease, chronic enteropathy, short bowel syndrome, or cancer).
- Raw Feeding Safety: For raw meat, freeze for 10 days before use to destroy parasites. In areas with Trichinella, freeze pork for 3 weeks before use.
- Storage and Feeding: Keep refrigerated food for 3 days and frozen food for 3-4 months. Feed small, frequent meals.
Feeding Guidelines
- Toy/mini breeds (<5 kg): 150-400 g/day
- Small breeds (5-10 kg): 270-700 g/day
- Medium breeds (10-25 kg): 600-1250 g/day
- Large breeds (25-45 kg): 1100-2100 g/day
- Giant breeds (45-80 kg): 1550-3500 g/day
Adjust the amount of food based on the dog's size, body condition, age, and activity level. Consult with a veterinarian as needed, especially if the dog is underweight or has severe liver disease.
Micronutrients and Vitamins
Supplementation with water-soluble vitamins is important in animals with chronic liver disease. Cats are particularly susceptible to deficiencies in thiamine (B1), cobalamin (B12), and vitamin K1. Fat-soluble vitamins are also important in animals with fat malabsorption or obstructed bile flow.
Vitamin K1
Administer vitamin K1 to any jaundiced animal with suspected liver disease (0.5â1.5 mg/kg, SC or IM, three times at 12-hour intervals) before invasive procedures.
Vitamin E
Vitamin E is an important antioxidant with anti-inflammatory and antifibrotic properties. Supplementation is often prescribed for animals with necroinflammatory or cholestatic liver disorders.
Additional Tips for Managing Liver Shunts
- Monitor for Hepatic Encephalopathy: Watch for signs such as lethargy, seizures, ataxia, and behavioral changes.
- Avoid High-Protein Treats: Pets with HE should avoid meats or high-protein foods and treats.
- Use Condiments and Appetite Stimulants: To combat "food fatigue" associated with low-protein diets, use condiments like bacon grease, BBQ sauce, teriyaki baste, catsup, and honey.
- Ensure Fresh Water: Provide clean, filtered water to minimize exposure to toxins.
- Avoid Toxins: Minimize exposure to environmental toxins, such as pesticides, herbicides, and chemical cleaning products.
- Consider Fiber Supplementation: Dietary fiber can reduce the availability and production of nitrogenous waste in the gastrointestinal tract.
Commercial Therapeutic Diets
Veterinary therapeutic diets formulated for liver disease or copper storage disease are often recommended. These diets typically have better-tolerated protein sources and restricted copper content. However, for some dogs, these diets may be too protein-restrictive, and alternative options should be considered.
Energy Allowance
Energy allowance should be estimated based on ideal body weight, with modified diets gradually introduced. Initial intake should be no greater than 50% of the calculated daily energy requirement on day 1, increased to 75% on day 2, and then to 100% by days 3â5.
The Importance of Monitoring
Regular monitoring is crucial for managing liver shunts effectively. This includes:
- Regular veterinary check-ups: To assess liver function and adjust treatment as needed.
- Blood tests: To monitor ammonia levels and other indicators of liver health.
- Urine analysis: To check for ammonium biurate crystals.
- Weight and body condition scoring: To ensure that the dog is maintaining a healthy weight and muscle mass.
Case Study: Nutritional Management of a Great Dane Puppy with an Intrahepatic PSS
A 6-month-old Great Dane puppy with an intrahepatic portosystemic shunt and hind limb angular limb deformity was evaluated to determine the appropriateness of his diet. The puppy was initially fed a veterinary therapeutic liver diet (Diet A), which was later switched to another veterinary therapeutic liver diet (Diet B). However, neither diet met the nutrient requirements for growth, particularly in terms of protein, calcium, phosphorus, and copper.
The puppy was then transitioned to a veterinary therapeutic vegetarian diet (Diet D), which had undergone feeding trials for growth. The diet was carefully managed to meet the puppy's energy needs while avoiding rapid growth, which can exacerbate skeletal issues. Over several months, the puppy's angular limb deformity corrected, and blood analysis showed improvement in several parameters.
This case highlights the importance of tailoring nutritional management to the individual needs of growing animals with liver shunts. It also underscores the need to carefully consider the nutrient content of therapeutic diets and to work closely with a veterinarian or veterinary nutritionist to ensure that the diet is balanced and appropriate.
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