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

Question 24

What is a single crystal?

Answer 24

a single crystal is where 70% of the urolith is composed of one type of crystal

Question 25

What is a mixed urolith?

Answer 25

Less than 70% one crystal, there is no identifiable nidus or shell

Question 26

What is a compound urolith?

Answer 26

Identifiable nidus of one crystal with surrounding layers of another crystal

Question 27

What is a matrix urolith?

Answer 27

Matrix without an appreciable crystalloid

Question 28

What are the three ways that crystals form?

Answer 28

* Growth = new crystals are added to the nucleus * Aggregation = crystals stick together, promoted by cementing substances or viscous bidning materials * Matrix= made up of lipids and proteins

Question 29

What does urinary saturation depend on?

Answer 29

* Urinary pH * Ionic strength * Solute concentration * Complexation

Question 30

What is the main way that uroliths form?

Answer 30

* Urine is full of colloids and crystalloids * dissolved in solution * Once saturated, the salt crystallises * Nucleation/ nidus

Question 31

What is the primary risk factor for calcium oxalate stones?

Answer 31

hyperoxaluria (urinary oxalate is a key determinant)

Question 32

What is the main consequence of infection of the urinary tract with urease producing microbes

Answer 32

Almost all struvite uroliths

Question 33

What are 95% of all cat struvite uroliths linked to?

Answer 33

Urinary excretion of excessive quantities of dietary minerals

Question 34

Where do calcium oxalate stones occur?

Answer 34

In both the upper and the lower urinary tract of dogs

Question 35

What is the effect of having a high dietary calcium?

Answer 35

Reduces oxalate absorption

Question 36

What is the effect of reduced dietary calcium?

Answer 36

* reduces complexion with oxalate in the intestinal lumen * increases intestinal absorption of oxalate * Increased renal excretion of both exogenous calcium and oxalate

Question 37

Why is the aim to reduce oxalate absorption?

Answer 37

* Keeps oxalate in the gut * Increased faecal excretion

Question 38

What percentage of uroliths are non-obstructive?

Answer 38

75% of UUT * removal is not recommended unless they are in pain or any other complications

Question 39

What is the link between obesity and urolithiasis?

Answer 39

Glucose load increases the urinary oxalate excretion * Greater mass load = increased urinary oxalate excretion

Question 40

What is insulin resistance associated with?

Answer 40

defects in the renal ammonium ion production

Question 41

What is the function of oxalobacter formigenes?

Answer 41

* gram negative anaeroic bacterium * degrades oxalate in the intestinal tract * Antibiotic consumption = absence of O.formigenes

Question 42

What does a diet low in magnesium prevent in cats?

Answer 42

struvite urolithiasis also encourages the formation of calcium oxalate

Question 43

What is one of the greatest diet related risk factors for the formation of oxalate calculi?

Answer 43

low-magnesium acidifying diets designed to prevent struvite calculi

Question 44

What causes struvite calcium oxalate infection?

Answer 44

Urease positive bacteria, i.e Staphylococcus, Streptococcus, Proteus

Question 45

What are ruminants most predisposed to?

Answer 45

Increased risk of developing struvite uroliths * high grain diets * low calcium/ phosphorys ratio * ruminants graze on silica-rich soil

Question 46

How may you prevent struvite calculi?

Answer 46

* increased urinary chloride excretion * decrease in urine pH

Question 47

How would you minimise urethral calculi?

Answer 47

* add sodium chloride to the total ration * promote increased sodium and chloride * increase mineral solubility

Question 48

How could you reduce urolith formation in equines?

Answer 48

* Decrease the time that urine stays in the bladder * Addition of 50-75g of salt to the daily ration to increase fluid intake

Question 49

What factors effect the incidence of urolithiasis in rabbits?

Answer 49

* Decreased water supply * Decreased activity level * Low forage intake