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Frequently Asked Questions:
Written by: Jeff Vidt, DVM
Dietary Protein
Much progress has been made in clinical nutrition in the past decade especially in the area of nutrition in the kidney failure patient. This is still an area of controversy between clinicians and nutritionists, but research is providing more insight concerning the role of dietary protein in the management of the kidney failure patient. What I hope to do here is provide a digest of this current state of affairs and let you make your own decisions.
- There is a link between dietary protein levels and the clinical signs of kidney failure.
- Once dogs have developed signs of uremia such as decreased appetite, vomiting, depression, electrolyte changes, GI ulceration, increased BUN and creatinine and weight loss, then decreasing the protein content of the diet is indicated these signs. Decreasing the protein content of the diet prior to the onset of clinical signs does not affect the progression of kidney failure. The pathogenesis of kidney failure is not clear and the rate of progression is variable.
- We know that increasing the protein in the diet results in increased blood flow to the kidneys - this occurs in both healthy dogs and those with decreased kidney function.
- Increased levels of dietary protein do not seem to change the rate of progression of kidney failure. Protein levels in the diet do not seem to affect mortality, rate of progression of uremia or the development of kidney lesions.
- Decreased protein levels in the diet may impair immune responses, decrease hemo-globin levels, cause anemia, decrease total protein levels and result in muscle wasting.
- Phosphorus restriction is an important factor in management of dogs with kidney failure.
- 3/4 to 15/16 of the kidney mass must be lost before progression of kidney failure occurs.
- When protein restriction is initiated fat and carbohydrate levels must be increased to provide alternate energy sources.
Much of the research in kidney failure and diet have been done in rats, dogs who have had surgically induced kidney failure and geriatric dogs with progressive kidney failure due to age-related changes. Does this information pertain to dogs with amyloidosis, immune-mediated kidney diseases or inflammatory kidney diseases? Studies need to be done to address these scenarios. The information available can be used to formulate the following general guidelines:
- Feed a diet with a protein level which fits the dog's activity level. Couch potatoes on a high protein diet become obese leading to other problems.
- Dietary protein levels do not appear to be involved in the progression of renal disease or play a role in the prevention of kidney failure. However, I prefer to err on the conservative side. I think protein levels in the 20-24 % range are probably safe. Of course other factors enter in such as the protein source, the bioavailability of the protein, fat content, carbohydrate levels, etc. must be considered as well.
- When the BUN is greater than 75mg/dl and/or signs of uremia develop, moderate protein restriction is indicated to decrease the BUN and the clinical signs. Phosphorus restriction is also indicated at this time. This is most easily done with the available commercial kidney diets on the market.
- What this also means is that these dogs must be monitored closely to follow changes in the BUN and creatinine levels. My experience in Shar-Pei indicates that they show clinical signs of kidney failure very late in the course of the condition when their BUN and creatinine levels are extremely elevated. Often, Shar-Pei owners miss the very subtle early changes and present their dogs when it's too late.
Diet does not appear to play a major role in prevention of kidney disease in Shar-Pei at this time. I think avoiding substances and situations which result in kidney damage are preventative steps that can be taken. Certain drugs such as aminoglycoside antibiotics can cause kidney damage and should be avoided, when possible. Decreased kidney blood flow can lead to kidney damage emphasizing the importance of IV fluids administered during anesthetic procedures and use of monitoring equipment. Situations, which result in low blood flow to the kidneys such as heat stroke, bloat, and shock must also be avoided. Infectious diseases can also result in kidney damage. These include bacterial kidney disease, heartworm, leptospirosis, Lymes disease, etc. Toxins such as ethylene glycol (antifreeze) and arsenic can cause kidney damage as well. To a large extent we can prevent some of these things. The major emphasis has to be monitoring the dogs so the onset of kidney failure is uncovered early in the course of the disease when dietary manipulations may be useful.
Jeff Vidt, DVM
3/2/98