Clinical nutrition in renal disease

Question 1

Outline protein restriction in renal dz

Answer 1

• ovezealous protein restriction –> protein malnutrition which can further compromise renal function
• protein restriction–> accelerates endogenous protein catabolism and contributes and can even exacerbate azotaemia
• the level of azotaemia that warrants protein restriction is controversial (little evidence to suggest an exact cut-off)

Question 2

Outline use of appetite stimulants

Answer 2

• ineffective in achieving adequate intake

- don’t start in hospital

Question 3

Rationale - protein restriction in kidney dz

Answer 3

• attempt to minimise generation of nirtogenous waste, thus relieving kidneys of extra workload
• controlling azotaemia may mitigate uraemia CS

Question 4

Problems of severe protein restriction

Answer 4

• renal repair requires some protein
• exacerbates malnutrition
• worsens cachexia

Question 5

What level of azotaemia warrants protein restriction?

Answer 5

• poorly define

- common recommendation is institute protein restriction when BUN >27g/L

Question 6

What is protein restriction for dogs and cats?

Answer 6

• Dogs:

Question 7

Outline protein restriction and glomerulopathies

Answer 7

• protein restriction may be useful with PLN
• proteinuria perpetuates glomerular injury (protein restriciton reduces proteinuria, other meds to restore glomerular membrane charge to reduce protein loss)
• don’t restrict too much
• ACEI and fish oils may be helpful in management

Question 8

What is best evidence for nutritional intervention in renal dz?

Answer 8

Revolves around phosphorous restriction:

• reduced mortality rate in various studies
• recent studies suggest it improves QoL and prolongs survival
• may prevent secondary renal hyperparathyroidism
• ideal time to start this not clear
• phosphorous-restricted diets may be preferable to oral phosphorous-binding agents which can be difficult to administer
• phosphorous-resticted diets may need to be supplemented with oral phosphorous-binding agents in cases where animals remain hyperphosphataemic

Question 9

T/F: sodium chloride intake has been linked with hypertension in dogs and cats

Answer 9

True in 40% of humans) but it has not been proven that restricting NaCl in diet reduces hypertension in animals as the hypertension associated with kidney disease in dogs/cats is not salt-sensitive (thus this aspect of diet is less important in animals vs people)

Question 10

Outline fibre and renal diets

Answer 10

Addition of fermentable fibre lowers BUN (rat models)

• enhancement of colonic degradation of urea
• increase in faecal N content
• described as ‘nitrogen trap’ in gut
• unknown if dietary fibre can reduce BUN in clinically relevant amounts
• unknown in dog/cat

Question 11

T/F: acidosis in renal disease accelerates lean body losses

Answer 11

True - activation of ubiquitin-proteosome system –> catabolism of body mm. This is an energy consuming process so exacerbates a NEB. Especially cats. Associated with anorexia, nausea, vomiting, lethargy, weakness, mm wasting and wt loss

Question 12

What alkalinising agents are useful?

Answer 12

• oral Na bicarbonate therapy
• potassium citrate therapy
• (bicarbonate and citrate are the buffers)
• may not work in many cats because of taste
• prescription diets for renal failure have been designed to decrease need for urinary acid excretion

Question 13

Outline omega-3 FAs in renal diets

Answer 13

• renal dz involves a constant state of inflammation
• modulation of inflammation may modulate progression in dz\ diets rich in omega-6 FAs worsen renal injury in certain models: acutely increased GFR, increased glomerular pressure, hastened renal failure
• omega 3 FAs are less inflammatory in their metabolites than omega-6 FAs
• omega 3s can preserve renal morphology and influence progression of disease
• omega-3s can improve appetite in some animals

Question 14

Benefits - omega 3 FAs in renal dz

Answer 14

• reduces inflammation
• lowers systemic arterial BP
• alters plasma lipid concentrations
• alter blood low
• lowered glomerular pressure
• may improve appetite
• preserves renal function
• further studies needed
• unknown if all renal dz would benefit from supplementation
• rather than omega 6: omega 3 ratios perhaps dose is more appropriate

Question 15

Supplement recommendations (EPA and DHA)

Answer 15

• EPA 40mg/kg/day
• DHA 25 mg/kg/day
• can be achieved using concentrated fish oil supplements designed for people
• supplements for dermatological dz in dogs and cats don’t contain FAs in sufficient amounts to incur the changes.

Question 16

Outline concentrated fish oil supplements

Answer 16

• 1 gram capsules: works for 4.5kg of bodyweight = big commitment with large dogs!

Question 17

Why is nutritional management of renal dz controversial?

Answer 17

debate whether or not progression of renal injury can be modulated by diet

• less controversial is role of nutrition in alleviating some CS associated with azotaemia (i.e. uraemia)
• when is the appropriate time to instigate renal diet?
• depends on stage of dz, nutritional status, concurrent dz, practical considerations, type of kidney dz

Question 18

In dogs/cats is there a link between dietary protein levels and progression of dz?

Answer 18

NO - despite rodent models that demonstrate there is a relationship

Question 19

Indication for protein restriction in non-azotaemic patients

Answer 19

PLNs (degree of proteinuria in these patients parallels protein intake to a point) At some point though, continued protein restriction will lead to worsening of hypoalbuminaemia and no further decrease in UPC ratio. Balancing degree of protein restriction can be challenging

Question 20

How may metabolic acidosis enhance progression of renal failure?

Answer 20

by promoting renal ammoniagenesis and through activation of the alternate complement pathway (which induces renal injury)

Question 21

How to support animals in renal failure prior to diet change to prescription?

Answer 21

IV fluids, gastroprotectants

Question 22

When should feeding tubes be recommended in renal failure?

Answer 22

if there is a possibility of reversing the condition (ARF d/t leptospirosis, grape or raisin-induced renal failure). Placement of oesophagostomy or percutaneous endoscopy-guided gastrostomy (PEG) tubes in renal failure patients allow for proper feeding during recovery of acute conditions. Discontinue after a few weeks/months.

Question 23

What dietary factors are manipulated in renal disease?

Answer 23

- Food intake/Calories
• Protein
• Phosphorus
• Potassium
• Sodium
• Fibre
• Fatty acids

Question 24

Outline phosphorous restriction in dogs/cats

Answer 24

• dogs