Dietary and Nutritional Management of Gastrointestinal Diseases

Special Article

Special Article on Clinical Nutrition

0195--5616/89 $0.00

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.20

Dietary and Nutritional Management of Gastrointestinal Diseases R. L. Remillard, DVM, PhD* and C. D. Thatcher, DVM, PhDt

Inadequate caloric and nitrogen intake, which may undermine proper therapeutic management, is far more common than is recognized. Dietary and nutritional management are recognized as essential adjuncts in the management of patients. Nutritional assessment and nutrient requirement determinations are essential to proper management of each patient. Dietetics incorporated into the therapeutic management of gastrointestinal tract diseases has been shown to be effective. Principles of dietary management for specific clinical signs referable to gastrointestinal diseases are presented. Patients that cannot or will not eat should be given nutritional support enterally, which is a simple and cost-effective procedure. Patients that cannot digest or absorb nutrients from the small intestine should receive nutrients parenterally, an effective but more complex method of nutritional support. Guidelines for enteral and parenteral nutritional support are presented to assist the veterinarian in the nutritional management of gastrointestinal patients. Early and aggressive nutritional therapy may be the factor most responsible for a positive response to other proper therapies.

NUTRITIONAL ASSESSMENT Nutritional assessment of the gastrointestinal patient is the summation of information obtained from history, physical examination, laboratory data, and, if known, the diagnosis. General indications of malnutrition have been From the Virginia-Maryland Regional College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Blacksburg, Virginia *Research Associate; Veterinary Clinical Nutritionist, Veterinary Medical Teaching Hospital tAssociate Professor; Veterinary Clinical Nutritionist, Veterinary MedicalTeaching Hospital This article is part of the May 1989 Veterinary Clinics of North America: Small Animal Practice symposium on clinical nutrition. Veterinary Clinics of North America: Small Animal Practice-Vol. 19, No. 4, July 1989

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adapted from the human literature7 for the veterinary patient. 23 Individual signs indicating a need for nutritional support (Table 1) are not as useful as several positive signs obtained in the overall assessment of the patient. Positive indications of malnutrition suggest that nutritional support should be instituted in conjunction with other therapies. Patients that are in poor condition nutritionally or are losing weight have a higher incidence of infections, decreased wound healing, dehiscence, and prolonged hospital stays. 1 Malnutrition is far more common than is recognized, primarily because the signs of malnutrition and indications for nutritional support are not assessed routinely.

NUTRIENT REQUIREMENTS IN DISEASE Diseased patients have lower metabolic rates and energy requirements than those of the comparable normal healthy (maintenance) individual (Fig. 1). The caloric requirements are less, primarily because diseased and (or) injured patients have reduced physical activities. In starvation without disease or injury, the metabolic rate is lowered because triiodothyronine (T3) concentrations decrease, which reduces nutrient requirements. Disease and injury, however, invoke neuroendocrine responses to stress that increase the metabolic rate above basal, resting, and starvation rates (see Fig. 1). The energy requirement of a patient therefore is greater than that in simple starvation but, in most cases, is less than that for maintenance of the normal active individual. The patient's actual metabolic rate and resultant energy requirement is related to the degree of trauma, disease, and (or) complications. Basal energy requirements (BER) in kcals per 24 hours for any mammal has been estimated20 using body weight in kilograms (BW) in the equation BER = 70(BW)0 75 In 1916, Krogh 21 correctly explained that true "basal" requirements could not be determined and suggested the term "standard" be used to better define the conditions under which energy measurements were determined. "Fasting" may be an appropriate term; however, heat increment (energy associated with food ingestion) is a small fraction (5 to 10 per cent) of the total energy requirement. We suggest the term "resting" be used, as it currently is in human medical literature. The term resting energy requirement (RER) will be used throughout this paper and considered equal to the previously used term "basal." All patients should receive calories sufficient to meet at least their RER. Although allometric equations theoretically are more accurate because they contain a y-intercept of zero, the linear equation may be used equally as well in a clinical setting 23 • 32 for patients weighing more than 2 kg: RER

=

30(BW)

+ 70

Maintenance metabolizable energy requirements (MER) 18• 29 have been determined on normal dogs and cats. These digestion trial measurements

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Table 1. Indications for Nutritional Support* Historical Chronic weight loss of greater than 10% of normal Maintenance IV fluid administration for more than 3 days Anorexia or poor food intake for more than 3 days Physical Examination Poor body condition, easily depilated hair, cracked and split (\ails Nonhealing wounds, presence of edema, ascites Muscle atrophy, bone pain, joint swelling Hepatomegaly, lymphadenopathy, tumors Laboratory Data Low albumin Lymphopenia Anemia Diagnoses Diseases with increased losses of protein and electrolytes caused by Vomiting, diarrhea Draining wounds, abscesses, burns Malassimilation, ileus Surgical removal of small intestinal segments Diseases that increase nutrient requirements Multiple trauma or surgeries Burns Cancer Infections, fever Chronic organ dysfunction Treatments that produce catabolism, anorexia, or dysphagia Drugs: corticosteroids, antibiotics, immunosuppressants Chemo- or radiation therapy Surgeries or lesions of the oral cavity, esophagus, or upper gastrointestinal tract *Data adapted from Butterworth CE: Some clinical manifestations of nutritional deficiency in hospitalized patients. In Levenson SM (ed): Nutritional Assessment-present status, future directions, and prospects; and Report of the Second Ross Conference on Medical Research. Columbus, Ohio, Ross Laboratories, 1981, pp 2-3; and Lewis LD, Morris ML, Hand MS: Small Animal Clinical Nutrition, ed 3. Topeka, Kansas, Mark Morris Assoc, 1987, pp 5-12. (From Remillard RL: Nutritional and dietary management of the gastrointestinal patient. Vet Med Report 1(3), 1989; with permission.)

were made on animals adequately fed and receiving 2 to 3 hours of exercise daily. Using the dog data as an example, the allometric 18 and linear32 equations are MER = 140(BW)0 75 and MER = 62.2(BW)

+ 144

These estimates of MER are adequate for the normal, healthy, moderately active dog or cat. The MER (kcals per day) for the dog therefore is twice the RER, whereas the MER for the cat is approximately 1.5 times RER.29. 31 There is strong evidence that the energy requirement of diseased and (or) injured patients is at or greater than RER, but rarely exceeds MER. In 1924, respiration calorimetry measurements of more than 3000 human

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Major burns

Ql Sepsis, Trauma

e Cancer e Surgery

Injury

TIME

Figure l. Comparative energy requirements in health and disease. (From Remillard RL: Nutritional and dietary manage ment of the gastrointestinal patient. Vet Med Report 1(3), 1989; with permission.)

cases with a wide variety of diseases, specifically excluding hyperthyroidism, demonstrated that 90 per cent of the patients were within ± 15 per cent of RER. 5 Acutely ill28 and major (70 per cent) burn42 patients have energy requirements 1.5 to 2.1 times RER as determined by bedside respiration calorimetry. In the most severe injuries, energy requirements of twice RER appear to be the upper limit. Veterinary patients therefore probably have an energy requirement that is some multiple of RER but rarely equal to their normal healthy adult maintenance requirement. 12 The total caloric requirement of a patient may be estimated using RER multiplied by a factor to compensate for the increased need that occurs with disease. The term "hypermetabolism" has been used in this context because the energy requirement of the patient is greater than the expected normal resting individual. At this time, best estimates of disease factors for veterinary patients (Table 2) are those adapted from the human respiration calorimetry measurements. 10• 25 • 28 • 37• 42 The magnitude of the stress and its effect on metabolic rate can be estimated only by the average effect of a specific disease state. Total energy requirements (TER) (kcals per day), therefore, may be calculated using the equation: TER = RER X Disease Factor. Food dosage is determined by the caloric requirement of the patient divided by the caloric density of the diet: Food dosage =

Total Energy Requirement (kcal per day)

--------~--~------~--~----~

Diet Caloric Density (kcal per g)

A patient's requirements for all other nutrients need not be calculated

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Table 2. Suggested Disease Factors in Determining Total Daily Canine Energy Requirements DISEASE CONDITION

Starvation Cage rest Elective surgery Cancer Trauma Multiple trauma Sepsis Burns, head trauma

FACTOR

RER* x .7 RER RER x 1.3 RER X '1.1-1.5 RER X 1.3-1.5 RER X 1.5-1.8 RER x 1.5-1.8 RER X 1.8-2.3

*Resting energy requirement (kcals ME/day) = 30(BW) + 70 or 70 BW075 . Adjust factors accordingly for the cat. From Remillard RL: Nutritional and dietary management of the gastrointestinal patient. Vet Med Report 1(3), 1989; with permission Adapted from Popp MB, Brennan MF: Metabolic response to trauma and infection. In Fischer JE (ed): Surgical Nutrition. Boston, Little, Brown and Co, 1983, pp 479-513. Long CL, Schaffel N, Geiger JW, et al: Metabolic response to injury and illness: Estimation of energy and protein needs from indirect calorimetry and nitrogen balance. J Par Ent Nutr 3:452-456, 1979. Hand MS, Crane SW, Buffington CA: Surgical nutrition. In Betts CW, Crane SW (eds): Manual of Small Animal Surgical Therapeutics. New York, Churchill Livingstone, 1986, pp 91-115

when a diet contains nonenergy nutrients properly balanced to the caloric density of the product. When the patient consumes the proper food dosage of a balanced diet, all nutrient needs have been met. The term "hyperalimentation," therefore, is not appropriate because the patient's nutrient needs are being met, not exceeded. In the patient with gastrointestinal disea:;e, a dietary change often is recommended in the management of the disease. Most often, the food dosage of the new diet is offered at MER for the adult or greater for the growing and underweight patient. If the patient has undergone surgery or trauma or has cancer, the MER and food dosage are decreased appropriately until the disease or condition has resolved. Any dietary recommendation should be modified to obtain and maintain optimum body weight and condition of the patient. Feeding more than needed of any diet may pose problems. Excessive calories may aggravate hepatic energy metabolism. Protein requirements are based on the energy requirement because sufficient calories must be available before protein will be used for tissue maintenance and repair. 27 Excessive protein requires additional energy expenditure to rid the body of excess nitrogen, which may or may not be handled well by the liver (urea cycle) and kidneys. Excessive protein administration increases the cost of nutritional support and burdens the patient with additional nitrogen metabolism and excretion. Conversely, insufficient protein has been linked to low albumin, poor immune-response, poor healing, and increased risk of dehiscence. The most efficient use of protein occurs when 4 to 6 g per 100 kcal are administered. 19• 25 Initial recommendations are to feed dogs 4 g of protein per 100 kcal TER, whereas cats, and dogs with increased protein losses (draining wounds, glomerulopathies, and so on), should be fed 6 g of protein per 100 kcal TER. Protein intake may be adjusted based on the patient's needs and ability to handle these initial protein recommendations.

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Nutritional support may be administered enterally and (or) parenterally. Enteral administration, whether oral or by feeding tube, is the method of choice in most clinical cases. Enteral nutrition is more physiological, less expensive, and easier than parenteral delivery. When the gastrointestinal tract (small intestine) is not functioning adequately to meet the patient's energy and nitrogen requirements, nutrients must be administered parenterally. Assessment of gastrointestinal function therefore is essential in the decision of how nutritional support should be provided.

DIETARY PRINCIPLES OF GASTROINTESTINAL MANAGEMENT Proximal Gastrointestinal Region The pharynx and esophagus function primarily to deliver food to the stomach. The stomach is the first site of protein and fat digestion and serves as a food reservoir. The stomach delivers chyme to the duodenum in a small continuous flow, which improves intestinal nutrient digestion and absorption. When administering nutritional support, it is advisable to use the stomach whenever possible to take advantage of these gastric functions. Pharyngeal or esophageal tissues heal slowly and are susceptible to secondary bacterial infections. With inflammation, trauma, or surgery involving these tissues, therefore, the recommendation has been to withhold oral feedings of regular pet foods for 5 to 7 days. Patients with no evidence of malnutrition may be held off food safely for 2 to 3 days but should receive nutrients by the third day. A malnourished patient (see Table 1) should receive nutritional support immediately as a liquid diet consumed orally or via feeding tube. A balanced human liquid diet (Pulmocare, Ross Laboratories, Columbus, OH) or blenderized pet food 23 may be used for several weeks, if necessary, prior to the reintroduction of regular food. Dietary goals are· to provide adequate nutrition to the patient using a diet that minimizes irritation and trauma to sensitive pharyngeal or esophageal tissues. It is important that the product chosen is consumed in quantities sufficient to meet the patient's calculated energy, protein, and fluid requirements. Both dogs and cats have been maintained on these enteral products for several weeks and patients do consume them voluntarily. Regurgitation. A definitive distinction between regurgitation and vomiting must be established either through historical evidence or direct observation. Causative factors useful in the differential diagnosis for regurgitation have been outlined previously. 9 Regurgitation of undigested food from the mouth or esophagus before it has entered the stomach signals a problem in the posterior pharyngeal area or esophagus. The more common cause of regurgitation is megaesophagus. Dietary management was found to be the treatment of choice when compan~d with surgical treatment in a 79-case clinical survey. 13 The goals of dietary management are to minimize regurgitation, avoid secondary aspiration pneumonia, and provide adequate nutrition. Feeding in an upright position and maintaining this position for 15 to 20 minutes after feeding has been successful in managing regurgitation. Pets can be trained to eat on stairs or

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from a counter or stool. Small pets easily can be held in an upright position to promote gravity fill of the stomach. Large dogs have been trained to remain in a sitting position or to lie down on an inclined board for the required time period. The meal consistency that best promotes flow through the esophagus to the stomach is determined in each case by trial and error. Dry foods could be a bolus stimuli to any remaining normal esophageal tissue and would be the form of choice given that gruel-type meals may increase the risk of aspiration pneumonia. Gruel-type diets, however, may be necessary when the entire esophagus is involved. 23 It would be advisable to use diets with concentrated forms of energy and other nutrients to meet the nutrie"nt requirements of the patient with smaller volumes. Diets in any form should be consumed in quantities sufficient to maintain optimum body weight and condition of the patient. Patients with positive indications of malnutrition on presentation (see Table 1), should have a gastrostomy feeding tube placed for immediate alimentation. If gastric reflux to the lower esophagus is of concern, as in the rare case of an incompetent lower esophageal sphincter, a gastrostomy feeding tube may not be appropriate because gastric reflux has been noted with this method of feeding. Parenteral or jejunostomy feeding should be considered in malnourished cases when complete rest is necessary for lower esophageal lesions. Vomiting. Vomiting requires a forceful, coordinated, musculoskeletal effort to eject food from the stomach to the mouth. In most vomiting cases of fewer than 24 hours' duration, withholding food for 24 to 48 hours and water for 24 hours generally controls the episode. Gradual reintroduction of food is advisable. Dietary goals are to meet the nutritional requirements of the patient with a diet that minimizes gastric irritation, promotes gastric emptying (low fat), and is assimilated easily. A patient may become dehydrated and (or) develop electrolyte abnormalities with ongoing episodes and correction of these medical problems is of foremost importance. Episodes of acute vomiting that occur for longer than 3 days or cases of chronic vomiting with positive signs of malnutrition (see Table 1) require nutritional support in addition to proper medical management. There are two methods of providing nutritional support to a patient with intractable vomiting. The most appropriate method depends on the experience of the clinician, availability of supplies, and cost of the service. Nutrients may be supplied parenterally using dextrose, lipid emulsions, amino acids with electrolyte solutions, plus vitamin B-complex. Parenteral administration of nutrients is the method of choice in cases of intractable vomiting at the Virginia-Maryland Regional College of Veterinary Medicine (VMRCVM). Parenteral nutritional support should be continued until the patient is consuming 50 to 75 per cent of the calculated food dosage orally. A second method of providing nutritional support to a patient with intractable vomiting utilizes a nasoesophageal or pharyngostomy tube with the tip in the caudal esophagus. The feeding tube method has worked well in cases of feline hepatic lipidosis where there were no primary esophageal or gastric abnormalities. A slow (5 to 20 ml per hour) cyclic (12 hours) infusion of a liquid diet has been tolerated well when small, frequent bolus feedings

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induced vomiting. A slow increase in the feeding rate and (or) concentration may allow gastric feeding in these sensitive patients. Patients should be brought back onto oral feedings gradually with small, frequent meals. Highly digestible diets offered in small, frequent feedings (4 to 6 per day) is recommended during food reintroduction (Table 3). After 1 week, the patient gradually may be changed back to the original diet. A feeding plan commonly used when changing diets is presented in Table 3. Following this schedule, the patient may be switched from one diet to another, in most cases, without gastrointestinal disturbances. Should a problem such as food refusal, vomiting, or diarrhea occur, the last successful diet mixture should be offered for several days before proceeding. Most pets, however, undergo dietary changes with little or no detectable gastrointestinal disturbance. Small Intestine

The primary function of the small intestine is to digest and absorb nutrients. The primary sign of small intestinal dysfunction is diarrhea, the passage of liquid stools. Diarrhea. Small bowel diarrhea may be acute or chronic, each with a list of possible etiologies. 9 As with vomiting, the first objective should be to correct dehydration, acid-base, and electrolyte imbalances, if present. Dietary goals are to provide an easily assimilated diet that meets the patient's nutrient requirements and allows healing of the intestinal tract. In most cases, fasting for24 to 48 hours, with access to water, either reduces or resolves the diarrhea by removing the effects of undigested food within the intestine. 23 Food should be reintroduced gradually, in small frequent meals, as outlined in Table 3. In the reintroduction of food to the diarrheic patient, feed an easily digestible diet. Increased digestibility reduces the quantity of undigested food within the intestine, which can alter gastrointestinal motility, secretions, and bacterial populations. 23 Rice is more digestible than corn or wheat, common carbohydrate sources in popular brands of pet foods. Lean meat sources also are more digestible Table 3. Recommended Schedules for Food Reintroduction and Dietary Changes Food Reintroduction Schedule Day 1 Day 2 Day 3

% daily food dosage % daily food dosage

+

% water

+ % water

100% daily food dosage

Offer each day's food dosage in small, frequent (4 to 6/day) meals Dietary Change Schedule Day 1-2 Day 3-4 Day 5-6 Day 7

Old diet : New diet (% of total daily food dosage) 75 50 25 0

25 50 75 100

Instructions: If at any time food is not tolerated, feed last successful mixture for several days, then proceed slowly

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than sources containing fat and bone. The diet of choice for the dog is a low-fat (15 per cent of diet dry matter [DM]), lactose-free, rice product (i/ d or did, Hill's Pet Products, Topeka, KS). Cats recovering from diarrhea apparently do better on a highly digestible diet that contains more fat (25 to 30 per cent DM) (c/d, Hill's Pet Products) than is recommended for dogs. 23 The reasons for this are not known. Patients presenting with chronic small boweJ diarrhea and positive indications for nutritional support (see Table 1) are managed best initially by providing nutrients parenterally. Parenteral nutrition often is instituted as a supportive measure while further diagnostics, such as exploratory surgery, are ongoing. Second, parenteral nutrition allows for complete emptying and rest of the gastrointestinal tract without depriving the patient of the nutrients required for recovery. Malassimilation Syndrome. Dietary management is an essential component in the medical management of patients with a malassimilation disease. Dietary intake should meet the patient's nutrient needs in an easily digested and absorbable form. Steatorrhea is the most prominent clinical sign in the malassimilation (maldigestion/malabsorption) syndrome. The pancreas provides digestive enzymes for fats, carbohydrates, and proteins, and the small intestine absorbs all three nutrients. The liver secretes bile salts that are required for dietary fat emulsification to micelles and the small intestinal lymphatics transport fat as chylomicrons to the systemic blood supply and tissues. Maldigestion occurs when there is a defect in intraluminal digestion. The defect may be the result of gastric, pancreatic, or biliary dysfunction. Pancreatic exocrine insufficiency (PEl) is the most common cause of fat maldigestion in dogs because pancreatic lipase is required for the hydrolyses of most dietary fats. Pancreatic enzyme addition to regular commercial dog food, however, did not improve nutrient digestion in dogs with PEl as much as simply feeding a highly digestible diet (i/d, Hill's Pet Products). 36 The combination of a readily digestible diet plus pancreatic enzymes provided more metabolizable energy to a dog with PEl than regular pet food with supplementation. The current recommendation, therefore, is to begin feeding a low-fiber, moderate-fat, highly digestible diet with regular additions of pancreatic enzymes (Viokase, A. H. Robins, Richmond, VA) according to label instructions, if needed. Pancreatic enzyme preparations vary considerably in their lipase activity. As a general rule, the more expensive preparations contain the more effective lipase preparations. In one study, adding digestive enzymes to food 20 to 30 minutes prior to feeding did not improve the response to dietary management. 23 Feeding more than normal may be necessary to compensate for any decreased digestibility and to maintain optimum body weight and condition. The addition of medium-chain triglycerides (MCT) to the diet may not be beneficial because MCT decreases diet palatability and may lower caloric intake, which is counterproductive. Malabsorption occurs with diseases that alter the structure and function of the small intestinal mucosa, including the lymphatics. Patients with lymphangiectasia, obstructed or dilated intestinal lymphatics, require severely restricted fat intakes. Lymph contains considerable quantities of

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protein in the form of albumin and globulin. As a result, excessive lymph losses often present as weight loss with edema or ascites. Diarrhea and steatorrhea usually are present. Dietary fats, which are composed of longchain fatty acids, normally are absorbed into intestinal lymphatics and are thought to increase postprandial lymph flow. 17 It has been recommended23 that dogs and cats with lymphangiectasia be fed a severely restricted fat diet (5 to 15 per cent DM) (r/d or w/d, Hill's Pet Products) because diets low in long-chain fatty acids minimize lymph flow and protein losses. These low-fat diets are high in fiber, and which factor is responsible·for the successful dietary management of lymphangiectasia is not known. Ideally, the dietary management of lymphangiectasia is a high-carbohydrate, high-protein, low-fat diet. The fiber content most beneficial in lymphangiectasia has yet to be determined. Medium-chain fatty acids may be a preferred form of lipid because they are absorbed directly into the blood supply and may not stimulate lymph flow. However, MCT oil (Mead Johnson, Evansville, IN) does not contain the essential fatty acids required by the dog and cat, has been related to hepatic lipidosis in cats, 26 may decrease diet palatability, and unabsorbed portions cause diarrhea. 16 Feeding a low-fat, high-carbohydrate and high-protein diet should be instituted for at least 7 days, preferably 2 weeks. If optimum weight and condition cannot be obtained or maintained, MCT oil can be added to the diet to increase caloric density, but should be used with caution, introduced gradually, and should not exceed 25 per cent of the caloric requirement. Micronutrients (vitamins and minerals) must be taken into consideration in the dietary management of steatorrhea. Fat-soluble vitamins, particularly A and D, may be administered intramuscularly or subcutaneously if fat absorption remains impaired because intraluminal long-chain fat absorption is required for fat-soluble vitamin absorption. During fat malabsorption, feeding a diet that contains fat may increase divalent cation losses (calcium, magnesium, zinc, and copper) because of the intraluminal formation of soaps. It therefore would be advisable to feed patients with fat malabsorption a highly digestible, low-fat diet that has been balanced properly with respect to micronutrients. Vitamin and mineral supplementation has not been reported to be necessary when a properly balanced commercial product is fed. Patients presenting with positive signs of malnutrition (see Table 1) caused by chronic malassimilation should be administered parenteral nutritional support during the diagnostic work-up. Long-term parenteral nutrition is not feasible in veterinary medicine because of financial and practical considerations, but the technical and nutritional expertise exists for shortterm (less than 3 week) administration. Parenteral nutrition in the management of patients with malassimilation disease therefore primarily is supportive and may be essential in the initial stages of case management. Parenteral nutrition can improve the caloric, nitrogen, and micronutrient balances in veterinary patients such that they may undergo diagnostic procedures, including exploratory surgery. Administration of parenteral solutions in the chronically debilitated malassimilation patient often is necessary with concurrent dietary management until adequate absorption of nutrients has

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been achieved. Parenteral nutritional administration may be necessary as a supportive procedure in proper management of malassimilation cases. 40 Pancreatitis. The dietary cause and nutritional management of a pancreatitis patient are currently debated in both the human and veterinary literature. Goals of dietary management are to decrease pancreatic secretions and to provide a nutrient source that meets the patient's nutrient requirements. Oral food intake stimulates pancreatic secretions. It is assumed that continued secretion of enzymes is deleterious to the inflamed pancreas. The majority of patients respond, usually' in 2 to 4 days, to a nothing per os (NPO) course of treatment. The patient usually makes a favorable recovery with a gradual reintroduction of a highly digestible diet fed in small, frequent meals (4 to 6 per day). Prolonged cases of pancreatitis, associated with pancreatic abscesses, pseudocysts, and duct obstruction, do not respond to NPO management. Parenteral nutrition may be instituted to meet the nutrient requirements of the patient and minimize pancreatic secretions. Although pancreatic atrophy has been associated with prolonged parenteral administration of nutritional support, 4 intravenous nutrient administration has been shown to stimulate pancreatic secretions but to a lesser extent than orally ingested food. 38 Elemental diets infused directly into the duodenum of dogs did stimulate some pancreatic output where oral administration of the same elemental diet stimulated a greater volume of pancreatic secretion. 38 The presence of free amino acids (phenylalanine, tryptophan, and valine) is considered the major stimuli to pancreatic secretions, more so than intraduodenal fat infusions. 11 Parenteral administration of nutrients to prolonged pancreatitis cases is the preferred method at the VMRCVM. The parenteral formula is modified for each case because such cases may be glucose intolerant and (or) hyperlipemic, which complicates the administration of dextrose and (or) lipid emulsions. 39 Jejunostomy tube feeding of an elemental diet could be used for a prolonged case of pancreatitis that was undergoing general anesthesia and abdominal surgery for reasons other than jejunostomy tube placement. Elemental diets (Peptamen, Carnation, Los Angeles, CA, and Vivonex-Ten, Norwich Eaton, Norwich, NY) may be infused by a slow continuous gravity drip or using an enteral pump. Directly infusing a readily absorbable elemental diet into the jejunum, as opposed to a polymeric product that requires some enzymatic digestion prior to absorption, may stimulate pancreatic secretions minimally. By either method, the prolonged pancreatitis case must be supported nutritionally after 3 days of NPO protocol. The method deemed the least invasive and that stimulates pancreatic secretions least is most desirable. Large Intestine The major function of the large intestine is to reabsorb water from the fecal material. Clinical signs oflarge intestinal problems therefore are either colitis or constipation. It also is the site of a large microbial population that may produce excessive gas resulting in flatulence, an objectionable problem, which often may be controlled through diet. Colitis. In the management of colitis, initial deworming is advisable,

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even in the face of negative fecal examinations for endoparasites. Proper dosage and duration of a broad-spectrum anthelmintic such as fenbendazole (American Hoechst, Somerville, NJ) and antiprotozoan agents like metronidazole (Searle Pharmaceuticals, Chicago, IL) should be part of the initial treatment plan. Should clinical signs of colitis continue, dietary management is indicated to meet the nutritional requirements of the patient with a diet that allows healing of inflammatory disorders and normalizes intestinal transit times. There are three major considerations in the dietary management of colitis: (1) gastrointestinal hypersensitivity, (2) fiber responsiveness, and (3) low-residue responsiveness. Dietary intolerance or food allergy cases often present with generalized pruritus, which may be associated with gastrointestinal signs (vomiting, colitis, flatulence). The offending ingredient usually is in popular commercial pet foods that may have been fed for several years before clinical signs develop and, in most cases, only one allergen is involved. 41 Dietary management of colitis caused by a food allergy involves a 3-week trial using ingredients the patient most likely has not been fed previously. A hypoallergenic diet should be composed entirely of ingredients rarely used in pet foods, such as lamb, egg, rice balanced with vegetable oil, vitamins, and minerals (did, Hill's Pet Products). Clinical signs should abate during the second or third week of strict dietary management-that is, feeding only the hypoallergenic diet. Successful dietary management may be continued as such or owners may add specific ingredients individually to the diet in an effort to identify the offending allergen. Patients not managed successfully on a commercially prepared hypoallergenic diet may respond to a simple (two ingredient) homemade diet. These patients should be hospitalized for 2 days of fasting and enemas to empty the gastrointestinal tract completely. Diets composed of cooked rice, potatoes, or pasta for carbohydrates and cooked lamb, egg, or cottage cheese for protein may be used. 33 White, highly refined rice and skinned potatoes are preferred to minimize potential sources of allergens. The carbohydrate and protein sources should be mixed in a ratio of approximately 2:1 on an as-is basis. If such a simple diet is successful, a hypoallergenic vitamin and mineral supplement should be added for long-term feeding because these diets are not balanced. Most veterinary vitaminmineral supplements contain sources of protein and flavorings similar to those used in pet foods. Supplements may be added to the successful homemade diet on a trial and error basis because these products may or may not be tolerated. There are hypoallergenic supplements available from health food stores. The addition of vegetable oil also is necessary to supply lipids for fat-soluble vitamin absorption and essential fatty acids. Suggested hypoallergenic diets, computer formulated to meet the nutrient requirements of the dog, are presented in Table 4. Most cases of colitis responsive to increased fiber intake are managed dietarily by withholding food for 1 to 2 days and reintroduction of food using a high-fiber (15 to 25 per cent DM) product. Not all fiber is created equal. The term crude fiber may be found on product labels and is determined by a specific laboratory procedure. The term "dietary fiber" is preferred to "crude fiber" because it is a physiologic term referring to all

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Table 4. Balanced Homemade Hypoallergenic Diets for Dogs* DIETSt FOODS

1

2

3

Protein Cottage cheese 300 g 150 g Lean braised lamb 300 g Hard-boiled egg Carbohydrates Pasta 650 g Potatoes lOOOg 650 g Rice Supplements Vegetable oil 1.0 Tbsp 8.0 g Bone mealt 2.5 g 9.0 g I nstruotions: Cook carbohydrate source without salt. Mix oil and (or) bone meal powder into carbohydrate source. Blenderize protein source with carbohydrate source well. Administer vitamin supplements separately, preferably prior to meal. *Computer formulated to meet canine nutrient requirements. 23 Each diet contains approximately 1 kcal ME/g and is adequate to meet the daily requirements of a 30-lb adult dog. Water-soluble vitamins should be supplemented (Hypoallergenic B-complex, Plus Products, Hillside, New Jersey) tAll measurements are for cooked edible portions :j:Bone meal is not hypoallergenic and may need to be replaced by a dicalcium phosphate product containing 18.5 per cent phosphorus and 20 to 24 per cent calcium

food residue that is resistant to hydrolysis by digestive enzymes. To date, there is no laboratory procedure specific for dietary fiber determination as defined. Fiber also may be divided into two broad categories: soluble and insoluble. Insoluble fiber is composed primarily of cellulose and polysaccharides with lignin, which is resistant to digestion and increases intestinal residue and fecal bulk. Insoluble fiber may increase fecal bulk by several methods: (1) undigested residue is increased in the colon, (2) undigested fiber absorbs water, and (3) fiber residue in the colon increases fecal bacterial weight. Feeding insoluble fiber decreases a rapid transit time. 6 • 14• 35 Soluble fiber such as pectins and gums are fermented in the colon to short-chain fatty acids and does not increase fecal bulk or decrease rapid transit times. It is possible to add fiber to the diet; sufficient quantities rarely are achieved, however, and, if so, the diet most likely will become unpalatable and unbalanced with respect to other nutrients (diluted). A well-balanced specifically formulated product therefore is recommended (r/d, w/d, Hill's Pet Products). High-fiber diets should be introduced (see Table 3) gradually (over 2 weeks) and owners need to be made aware of the increased stool production and possible flatulence and borborygmus. These latter symptoms are less likely to be a problem if the high-fiber diet is introduced gradually and often resolve with time as the patient becomes accustomed to the diet. Constipation also often is managed most successfully by feeding a highfiber diet. Insoluble fiber is the treatment of choice for constipation because it increases fecal bulk, decreases intracolonic pressure, and increases slow

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transit times 6 • 14• 35. as well. Increasing exercise also may encourage more frequent defecation. Patients with colitis that do not respond positively to a high-fiber diet within 2 weeks should be switched to a low-residue, low-fiber diet. 23 Lowresidue or highly digestible (egg and rice) diets present less undigested material to the colon, which may reduce irritation to the colonic mucosa. During acute phases of colitis when a patient has diarrhea and is dehydrated, fluid administration to re-establish acid-base and. electrolyte imbalances is most important. Parenteral nutritional support may be used for short-term bowel rest and diagnostics, if necessary. Oral feedings should be instituted with ~ highly digestible pet food, which should not cause diarrhea and presents little residue to the colon. When the patient tolerates the highly digestible diet, a gradual dietary change to a pet food with more fiber may be attempted if the colitis is considered fiber responsive. Parenteral feedings should not be discontinued until 50 to 75 per cent of the patient's requirements are being met and tolerated via enteral feedings. Flatulence is a chronic objectionable problem more common in dogs than in cats. 23 Dietary management primarily is concerned with decreasing the intestinal gases produced by bacterial fermentation of undigested food. Excessive colonic gas production may result from a malabsorptive disorder or the ingestion of unabsorbable carbohydrates. Correction of a malassimilation disease may reduce or eliminate a flatulence problem. Initial recommendation is NPO for 2 to 3 days then feeding a 1ow residue or more digestible diet in small, frequent meals. This protocol will reduce food residues available for bacterial fermentation in the large intestine and should reduce gas production. Most commonly, the soybean sources present in many pet foods have been associated with flatulence because they contain nonabsorbable oligosaccarides (raffinose, stachyose, and verbascose) and increase intestinal gas production in some dogs. 23 Other food sources that contain unabsorbable carbohydrates and should be avoided are beans, sulfur-containing vegetables, fruits, whole wheat products, and high-lactose products (milk). Last, feeding high-protein diets and (or) vitamin supplements support the colonic microbial population and, therefore, should be discouraged when managing flatulence. Feeding onions, garlic, spices, and spoiled foods should be discouraged, particularly in managing flatulence. In humans, swallowed air does not contribute to colonic gas. Carbon dioxide produced in the duodenum is absorbed and also does not contribute to flatus production. In the veterinary patient, however, these sources of flatus are hypothesized and attempts should be made to minimize aerophagia. . Enteral Nutrition

Route. Enteral nutritional support provides nutrients to the patient using some portion of the gastrointestinal tract. Patients that cannot or will not eat but can digest and absorb nutrients from the gastrointestinal tract should receive enteral nutritional support. Feeding via the gastrointestinal tract is the simplest, fastest, easiest, safest, least expensive, and most physiological method of feeding patients. If enteral nutritional support is necessary for more than two days, tube feeding is the method of choice.

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An orogastric, nasoesophageal or pharyngostomy, gastrostomy, or jejunostomy tube may be used. Methods of placement and feeding tube recommendations have been discussed previously. 8 Tube placement should be in the most proximal functioning portion of the gastrointestinal tract via the least invasive method. Orogastric tubes generally are used for 2 to 3 days or less but require tube placement at each feeding. Nasoesophageal tubes may remain in place for extended periods of time (days to weeks). Both types of feeding tubes may be used in anorectic patients with no nasal, oral, or pharyngeal lesions. Pharyngostomy tubes are placed in patients with disease of or trauma to the nasal or oral cavity. This tube can be used long-term (weeks to months) for in-hospital or home feeding. Gastrostomy tubes placed at surgery or by the percutaneous method, utilizing an endoscope, are used in patients that require by-passing the pharynx and esophagus. Gastrostomy tubes also work well for long-term (weeks to months) in-hospital or home feedings. Tubes placed with the tip in the caudal esophagus or stomach allow bolus or meal-type feeding schedules because the stomach acts as a food reservoir. The exception is the patient that cannot tolerate bolus feeding without vomiting. Such patients may benefit from a slow continuous-drip administration. When it is necessary to by-pass the proximal gastrointestinal tract, a jejunostomy tube may be placed, ideally, at the time of surgery for other purposes. 34 Jejunostomy tubes require slow, if not continuous, administration of the diet, usually delivered by an enteral feeding pump. In human medicine, there has been renewed interest in the use of enteral feeding and the advantages over parenteral nutritional administration. 2• 30 There is increasing evidence that 3 days or more without nutrient administration into the gastrointestinal tract allows enterocyte deterioration and decreases gastrointestinal immunity. 3 Translocation of enteric bacteria because of a compromised intestinal mucosal barrier may be a source of sepsis. 30 A combination of enteral and parenteral administration has been suggested. The infusions of only 10 ml of a liquid protein diet during parenteral feeding has been beneficial in preventing intestinal mucosal deterioration. 3 In addition, intestinal adaptations after disease and intestinal hypertrophy after surgery require the presence of nutrients intraluminally. The intake of food has been shown to promote intestinal hyperplasia and brush border enzyme activity. 15 Current recommendations therefore encourage some enteral feeding, if possible, to those patients receiving parenteral nutritional support. Feeding the gastrointestinal tract is as important to recovery as feeding the patient. Diet. Diet selection depends on tube size, tube location within the functioning gastrointestinal tract, the availability and cost of products, and the experience of the clinician. There are many diets available for veterinary patients, which can be divided into two major types: (1) human liquid products and (2) blenderized pet foods. Nasal and jejunostomy tubes usually have a small diameter (less than 8 french) and require liquid or strained blenderized diets. Orogastric, pharyngostomy, and gastrostomy tubes have larger diameters and are suitable for blenderized pet foods. In general, the human liquid diets cost 2 to 10 times more than the blenderized pet foods and, if hypertonic, may cause diarrhea. These diets, however, are homo-

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geneous liquids that result in potentially fewer tube complications, such as plugging. Some patients will consume these products voluntarily, which may preclude tube placement. Dogs with oral surgical repair at the VMRCVM have been maintained successfully on a human liquid product (Pulmocare) for 5 to 7 days using only voluntary consumption. Most liquid diets are adequate for the adult dog but are too low in protein for puppies and dogs with high protein losses (protein-losing enteropathies, draining wounds, and so on). Liquid enteral products do not contain adequate concentrations of protein, taurine, and arachidonic acid for the cat. The cat also has specific. nutrient requirements for arginine, vitamin A, niacin, and vitamin B6 • Cats fed human liquid enteral diets for greater than 7 days should be supplemented (Feline Probalance, Norden Laboratories, Lincoln, NE). There are many human liquid enteral products of three basic types: (I) elemental, (2) polymeric, and (3) modular, which have been discussed previously. 23 Elemental diets require minimal digestion and can be infused directly into any feeding tube, including one in the jejunum. Elemental diets are indicated in disease conditions such as inflammatory bowel disease, lymphangiectasia, and alimentary lymphosarcoma, or in any condition in which digestive capabilities are questionable. Products representative of this category are Peptamen and Vivonex-Ten. Polymeric diets do require normal digestive processes and are appropriate for most veterinary clinical situations, particularly when a small feeding tube (less than 8 french) has been placed. Products such as Ensure and Pulmocare (Ross Laboratories) are only two of a large number of products available. 23 Modular products are concentrated forms of one nutrient and are used primarily as supplements. These include protein supplements such as Promod (Ross Laboratories) and Propac (Organon, West Orange, NJ), carbohydrate supplements such as Polycose (Ross Laboratories) and fat supplements such as vegetable oil and M CT oil. Baby foods commonly are used because some patients will eat these products voluntarily when offered. Baby foods are strained and will flow through a feeding tube well. Meat and egg baby foods are high protein (30 to 70 per cent DM) and high fat (20 to 60 per cent DM) products but contain only 10 per cent of the calcium required by the dog and cat. In general, they have a large inverse calcium-to-phosphorus ratio, contain nearly twice the sodium needed, and most likely do not contain a balanced mixture of micronutrients for the dog and cat. The optimum veterinary recommendation for a tube feeding diet is blenderized pet food using a product that has been feeding-trial tested and proven to be balanced and complete for the dog or cat. 23 These products are available more readily and are less expensive than human liquid diets. Blenderized pet foods are higher in protein and equal in caloric density to human liquid diets, and are known to contain the essential, properly balanced micronutrients. There are fewer medical complications such as diarrhea when feeding a blenderized pet food, but they are more likely to plug a small or large feeding tube if the tube is not managed properly. When appetite returns and (or) the tube has been removed, patients may consume the same food, which eliminates a dietary change. There are a

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variety of pet foods available that have been designed specifically for particular disease conditions (Prescription Diets, Hill's Pet Products). Regardless of the product fed, food dosage should be determined and the proper quantity of the food should be administered to the patient. Procedures. The feeding schedule often is determined by the patient's ability to tolerate food and the method of feeding. A gradual reintroduction of food is advised for patients that have not consumed food for more than 3 days (see Table 3). The diet should be warmed between room and body temperature, but no higher, before feeding. Bolus ·infusion of diets must be slow (2 to 3 minutes) to allow gastric expansion. Daily food dosage should be divided into several meals according to expected stomach capacity. 'Capacities for cats and dogs are approximately 10 to 15 ml per kg during initial food reintroduction, but may reach as high as 45 to 90 ml per kg after several days offeeding. Vomiting, retching, and abdominal discomfort may occur when too much food is infused or when the infusion rate is too rapid. Feeding should stop at the first sign of discomfort and meal size be reduced by 50 per cent for 24 hours, then increased gradually. Diets given via jejunostomy tube must be infused using a slow gravity drip or enteral pump at a rate of 5 to 20 ml per hour. Each meal should be followed by a water flush to clear the feeding tube. Plugged feeding tubes may be cleared successfully using a stylet or filling the tube with a carbonated beverage and allowing time for. the food plug to dissolve. In general, endport tubes are easier to maintain than the side-port tubes because food tends to become trapped in the blind-end of the side-port tubes. Last, the patient's fluid requirement also must be met. Water may be administered through the feeding tube to meet this requirement. Oral medications also may be administered via the feeding tube. Parenteral Nutrition Patients that cannot digest or absorb adequate nutrients from the gastrointestinal tract require nutritional support in the form of parenteral administration. In cases where the gastrointestinal tract is not functioning properly or complete gastrointestinal rest is required for healing, the administration of nutrients intravenously is appropriate. Patients' TER and protein requirements are calculated as previously presented. Parenteral solutions are composed of dextrose, amino acids with electrolytes, lipid emulsions, and vitamin B-complex. 24 • 39 A 50 per cent dextrose solution and 20 per cent lipid emulsion are used most commonly, in combination such that each provides approximately 50 per cent of the caloric need. The amino acid solutions provide the required protein and electrolytes. Injectable vitamin B-complex should be provided daily (1 to 2 ml per day). Actual calculation of parenteral solutions based on patient requirements has been described. 39 Solutions may be compounded by several methods. One method involves transferring each individual parenteral product using a needle and syringe from the individual bottles to an empty sterile bag. This method is time consuming and the risk of microbial contamination is high. Another method utilizes the Ali-in-One compounding bag (Baxter Healthcare, Deerfield, IL), a sterile empty bag with an attached three-lead transfer set; Each lead, with a filtered vent, is inserted directly

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into the individuaJ product bottles. This method is most practical for the veterinarian and makes compounding solutions simpler in a clinical setting. Parenteral solutions are hypertonic and must be administered by means of a central venous catheter. Silicone catheters (Centrasil catheter, Baxter Healthcare) essentially are nonreactive with body tissues and fluids may be used for extended periods of time (weeks to months). Any catheter material with the tip in a central vein, however, may be used for 2 to 4 days. Parenteral solutions, in most cases, are administered continuously over 24 hours. There is evidence that cyclic parenteral administration ·of solutions does not alter energy metabolism 22 and simulates normal feeding patterns more closely than -a continuous infusion. With close monitoring, it is possible to deliver parenteral solutions to veterinary patients in a cyclic rather than a continuous pattern. 39 Close monitoring of patients administered parenteral nutrition is essential. There are two major types of complications: (1) catheter-related, such as a mechanical problem or sepsis, and. (2) metabolic abnormalities concerning blood glucose, nitrogen, electrolytes, and lipids. 39 Parenteral nutritional support, although possible in veterinary medicine, may not be possible in all small animal practices. As veterinarians become more familiar with the indications for parenteral nutritional support and as more case reports demonstrate the effectiveness of this medical adjunct, 24 • 40 parenteral nutrition will be used as a supportive tool in veterinary medicine.

SUMMARY The value of proper diet in the management of the gastrointestinal patient has been demonstrated. As experience and knowledge increase, diets will become more refined to address specific diet-related abnormalities. There is an increasing awareness in veterinary medicine, and justifiably so, of the benefit of nutritional support, administered enterally or parenterally. Aggressive, early, and adequate nutritional support may be the most important factor responsible for a successful response to other aspects of therapy and recovery, and has to represent an improvement in veterinary medicine.

REFERENCES l. Abbott WM: Indications for parenteral nutrition. In Fischer JE (ed): Total Parenteral Nutrition. Boston, Little, Brown and Co, 1976, pp 3-14 2. Adams S, Dellinger EP, Wurtz MJ, et a!: Enteral versus parenteral nutritional support following laparotomy for trauma: A randomized prospective trial. J Trauma 26:882-891, 1986 3. Alverdy J, Chi HS, Sheldon GF: The effect of parenteral nutrition on gastrointestinal immunity. Ann Surg 202:681-684, 1985 4. Betzhold J, Howard L: Enteral nutrition and gastrointestinal disease. In Rombeau JL, Caldwell MD (eds): Clinical Nutrition: Enteral and Tube Feeding, voll. Philadelphia, WB Saunders, 1986, pp 338-361 5. Boothby WM, Sandiford 1: Basal metabolism. Physiol Rev 4:69-161, 1924

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6. Burrows CF, Kronfeld DS, Banta CA, et al: Effects of fiber on digestibility and transit time in dogs. J Nutr 112:1726-1732, 1982 7. Butterworth CE: Some clinical manifestations of nutritional deficiency in hospitalized patients. In Levenson SM (ed): Nutritional assessment: Present status, future directions, and prospects. Report of the second Ross Conference on Medical Research. Columbus, Ohio, Ross Laboratories, 1981, pp 2-3 · 8. Crowe DT: Methods of enteral feeding in the seriously ill or injured patient: Part I and part II. J Vet Emerg Crit Care 3:1-17, 1986 9. Ettinger SJ: Textbook of Veterinary Internal Medicine. Diseases of the Dog and Cat, ed 2, vol 1 and 2. Philadelphia, WB Saunders, 1983 10. Feurer ID, Mallen JL: Measurement of energy expenditure. In Rombeau JL, Caldwell MD (eds): Clinical Nutrition: Parenteral Nutrition, vol 2. Philadelphia, WB Saunders, 1986, pp 224-236 11. Go VLW, Hofmann AF, Summerskill WFJ: Pancreozymin assay in man based on pancreatic enzyme secretion: Potency of specific amino acids and other digestive products. J Clin Invest 49:1558-1564, 1970 12. Hand MS, Crane SW, Buffington CA: Surgical nutrition. In Betts CW, Crane SW (eds): Manual of Small Animal Surgical Therapeutics. New York, Churchill Livingstone, 1986, pp 91-115 13. Harvey CE, O'Brien JA, Darle VR, et a!: Megaesophagus in the dog: A clinical survey of 79 cases. JAm Vet Med Assoc 165:443-446, 1974 14. Harvey RF, Pomare EW, Heaton KW: Effects of increased dietary fiber on intestinal transit. Lancet 1:1278-1280, 1973 15. Hermann-Zaidius MG: Malabsorption in adults: Etiology, evaluation, and management. J · Am Diet Assoc 86:1171-1178, 1986 16. Hopman WPM, Jansen BMJ, Rosen busch G, et al: Effect of equimolar amounts of longchain triglyerides and medium-chain triglycerides on plasma cholecystokinin and gall bladder contraction. Am J Clin Nutr 39:356-359, 1984 17. Jeffries GH, Chapman A, Sleisenger MH: Low-fat diet in intestinal lymphangiectasia. Its effect on albumin metabolism. N Eng! J Med 270:761-766, 1964 18. Kendall PT, Blaza SE, Smith PM: Comparative digestible energy requirements of adult beagles and domestic cats for body weight maintenance. J Nutr 113:1946-1955, 1983 19. Kinney JM: Energy metabolism: Heat, fuel, and life. In Kinney JM (ed): Nutrition and Metabolism in Patient Care. Philadelphia, WB Saunders, 1988, pp 3-34 20. Kleiber M: Body size and metabolism. flilgardia 6:315-353, 1932 21. Krogh A: Respiratory Exchange of Animals and Man. New York, Longmans, Green and Co, 1916 22. Lerebours E, Rim bert A, Hecketsweiler B, et al: Comparison of the effects of continuous and cyclic nocturnal parenteral nutrition on energy expenditure and protein metabolism. J Par Ent Nutr 12:360-364, 1988 23. Lewis LD, Morris ML, Hand MS: Small animal clinical nutrition, ed 3. Topeka, Kansas, Mark Morris Associates, 1987, chapters 3 and 5 24. Lippert AC: Total parenteral nutrition in dogs and cats (abstr). In Proceedings of the Fifth Annual Veterinary Medical Forum, 1987, p 905 25. Long CL, Schaffel N, Geiger JW, et al: Metabolic response to injury and illness: Estimation of energy and protein needs from indirect calorimetry and nitrogen balance. J Par Ent Nutr 3:452-456, 1979 26. MacDonald ML, Anderson BC, Rogers QR, et al: Essential fatty acid requirements of cats: Pathology of essential fatty
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32. National Research Council: Nutrient requirements of dogs. Washington, DC, National Academy Press, 1985, pp 2-5 33. Nelson RW, Steokey LJ, Kazacos E: Nutritional management of idiopathic chronic colitis in the dog. J Vet Intern Med 2:133-137, 1988 34. Orton EC: Enteral hyperalimentation administered via needle catheter-jejunostoma as an adjunct to cranial abdominal surgery in dogs and cats. JAm Vet Med Assoc 188:14061411, 1986 35. Payler PK, Pomare EW, Heaton KW, et al: The effect of wheat bran on intestinal transit. Gut 16:209-213, 1975 36. Pidgeon G: Effect of diet on exocrine pancreatic insufficiency in dogs. J Am Vet Med Assoc 181:232-235, 1982 37. Popp MB, Brennan MF: Metabolic response to trauma and infection. In Fischer JE (ed): Surgical Nutrition. Boston, Little, Brown and Co, 1983, pp 479-513 38. Reily GA, Nahrwold DL: Pancreatic secretion in response to an elemental diet and intravenous hyperalimentation. Surg Gynecol Obstet 143:87-91, 1976 39. Remillard RL, Thatcher CD: Parenteral nutrition in the small animal patient. Vet Clin North Am [Small Anim Pract)19:6, 1989 40. Remillard RL, Matz ME, Shell LG: Nutritional management of a complicated case of diabetes mellitus in a dog. Vet Med, submitted 41. Walton GS: Allergic responses to ingested allergens. In Kirk RW (ed): Current Veterinary Therapy VI. Philadelphia, WB Saunders, 1977, pp 576-579 42. Wilmore DW, Long JM, Mason AD, et al: Catecholamines: Mediator of the hypermetabolic response to thermal injury. Ann Surg 180:653-669, 1974 Virginia-Maryland Regional College of Veterinary Medicine Virginia Polytechnic Institu•e and State University Blacksburg, VA 24061