Uroliths and Nutrition

Question 1

Where do oxalates come from?

Answer 1

1. A combination of dietary sources
2. endogenous synthesis from precursors such as ascorbate and various amino acids

Question 2

What percentage of kidney stones are composed primarily of calcium oxalate

Answer 2

75%

Question 3

What are almost all struvite uroliths a consequence of?

Answer 3

• infection of the urinary tract with urease producing microbes (e.g staphylococci)

Question 4

What are 95% of struvite uroliths linked to in cats?

Answer 4

• Urinary excretion of excessive quantities of dietary minerals

Question 5

What does acidic urine cause the precipitation of?

Answer 5

• Calcium oxalates
• Uric acid
• Cystine uroliths

Question 6

What does alkaline urine cause precipitation of?

Answer 6

• Struvite
• Calcium carbonate
• Calcium phosphate

Question 7

How is calcum oxalate ususally formed?

Answer 7

Over-saturation of urine with calcium and oxalate

Question 8

Why should you not recommend reducing dietary calcium?

Answer 8

• Reduced complexes with oxalate formed
• Increased intestinal absorption of oxalate
• increased renal excretion of oxalate

Question 9

What may a low dietary intake of phosphorus be linked to?

Answer 9

Increased urinary calcium excretion
* lower binding of calcium by phosphate ions in the GIT

Question 10

What can excessive levels of phosphorus in the GIT mean?

Answer 10

• They act as scavengers for calcium
• increase the availability of oxalate uptake in the intestine

Question 11

What are some of the risk factors for calcium oxalate stones in dogs?

Answer 11

• Dogs under 7
• males
• neutured

Question 12

What is the link between obesity and urolithiasis?

Answer 12

Glucose load increases urinary oxalate excretion

Question 13

What is the function of Oxalobacter formigenes?

Answer 13

Gram-Negative anaerobic bacterium
degrades oxalate in the intestinal tract

Question 14

What is the link between high phosphorus diets and kidney disease?

Answer 14

cats with chronic kidney disease have signficantly higher phosphorus and protein intakes

Question 15

What is the function of magnesium in the GIT?

Answer 15

• Directly interacts with oxalate to form an insoluble complex
• this lowers the free oxalate concentration in the GIT
• reduction in the absorption of oxalate, less oxalate for excretion via the kidneys

Question 16

How can you reduce the risk of urolithiasis in cats?

Answer 16

• Increase water intake
• Increase the urinary input
• dilutes the urine
• reduces the risk of CaOx crystallisation in the urinary tract

Question 17

What is the link between high protein diet and urine?

Answer 17

• Increased protein diet
• acompanied by increased water consumption
• increased urine volume in cats

Question 18

What is the main risk factor of struvites?

Answer 18

• alkaline urine and increased levels of magnesium, ammonium and phosphate in urine

Question 19

What is the consequence of a diet low in magnesium?

Answer 19

Prevents struvite urolithiasis
* may also encourage the formation of calcium oxalate

Question 20

How are struvites produced in the urine?

Answer 20

• Urinary tract infection with urease producing bacteria
• Urine with a high urea concentration (bacteria hydrolyse urea to ammonia)
• Ammonium ions reduce the hydrogen concentration
• Increased urine pH

Question 21

What increases the likelihood of ruminants getting struvites?

Answer 21

• High grain diets
• low calcium/ phosphorus ratio
• ruminants also graze on silica-rich soil so are predisposed to silica uroliths

Question 22

How may you prevent struvite calculi?

Answer 22

Increase urinary chloride excretion
* decreases urine pH

Question 23

What are the common characteristics of diets fed to overweight horses?

Answer 23

• Preserved forages
• low moisture content
• unbalanced mins
• low dry matter intake