Lecture 14

Question 1

What is urolithiasis?

Answer 1

presence of a mineral or mineral/matrix concretion within any part of the urinary tract

Question 2

What are the possible locations for a urolith?

Answer 2

*lower urinary tract:
-bladder: cystolith
-urethra: urethrolith

*upper urinary tract:
-kidney: nephrolith
-ureter: ureterolith

Question 3

Which stone types are radiopaque and show up on radiographs?

Answer 3

-calcium oxalate
-calcium phosphate
-brushite
-silicate

Question 4

Which stone type is moderately radiopaque?

Answer 4

struvite

Question 5

Which stone types are radiolucent?

Answer 5

-cystine
-urate

Question 6

How does the make up of stone determine the naming?

Answer 6

-if > 70% of the stone is the same, it is labeled as a specific urolith type
-if < 70% of the stone is the same, it is a compound or mixed urolith

Question 7

What is the driving factor behind stone formation?

Answer 7

supersaturation/increased particle concentration in solution

Question 8

How does undersaturated urine affect stone formation?

Answer 8

-stable urine
-crystals dissolve
-crystals do not precipitate
-crystals do not grow or aggregate

Question 9

How does saturated urine affect stone formation?

Answer 9

-metastable
-crystals do not dissolve
-crystals do not precipitate spontaneously
-crystals can precipitate on a template (nucleation)
-inhibitors will impede or prevent crystallization

Question 10

How does oversaturated urine affect stone formation?

Answer 10

-unstable
-crystals form spontaneously
-crystals aggregate or grow
-crystals do not dissolve

Question 11

What is the primary goal when managing urolithiasis?

Answer 11

reduce urine saturation

Question 12

What are the components factored in to relative supersaturation?

Answer 12

-urine pH
-temperature
-ionic strength

Question 13

What are the risk factors for uroliths?

Answer 13

-urine pH
-urinary tract infection
-dietary factors
-decreased frequency of urination
-stone promoter and inhibitor balance
-increased urine volume
-metabolic factors
-age, breed, gender

Question 14

Why are crystals not a good indicator of stone presence?

Answer 14

-crystals can be present with or without a stone
-crystal type may not match stone type

Question 15

Which aspects related to urine volume can contribute to stone formation?

Answer 15

-urine dilution
-food type
-sodium levels
-voiding frequency

Question 16

What is urine pH influenced by?

Answer 16

-diet
-drugs
-feeding schedule
-infections

Question 17

How does urine pH play into stone formation?

Answer 17

*acidic stones:
-calcium phosphate
-purines
-calcium oxalate
-cystine
-silica

*neutral stones:
-sterile struvite

*alkaline stones:
-infection-induced struvite
-calcium apatite

Question 18

How does diet affect urine pH?

Answer 18

-meat-based diets are acidifying and increase urea and ammonia
-vegetable-based diets are alkalinizing

Question 19

How does feeding frequency impact urine pH?

Answer 19

-urine becomes more alkaline around meals from the excess bicarb. used to buffer HCl
-more frequent meals will keep the urine alkaline for a greater portion of time

Question 20

Which type of bacteria is associated with struvite stone formation in dogs?

Answer 20

urease-producing bacteria

Question 21

What must be considered when crystals are seen on urinalysis?

Answer 21

-urine pH
-collection time vs. time of analysis
-refrigeration if greater than 1 hour post-collection
-crystals can be normal in saturated urine

Question 22

When are crystals definitively abnormal?

Answer 22

-large numbers in a fresh sample
-evidence of aggregation
-certain types that are never normal

Question 23

Which metabolic factors can play into stone formation?

Answer 23

*hypercalcemia due to:
-hyperparathyroidism
-hyperadrenocorticism
-idiopathic

*uric acid:
-leads to urate stones

Question 24

What are the breed predispositions for stones?

Answer 24

*calcium oxalate:
-schnauzer
-poodle

*cystine:
-bernese mountain dog
-bulldog

*urate:
-bulldog
-dalmatian

Question 25

What are the potential presentations of uroliths?

Answer 25

-asymptomatic -upper or lower urinary tract signs -uroabdomen in obstruction cases

Question 26

Which diagnostics are done in suspected urolith cases?

Answer 26

-history and PE -biochem. testing (ID underlying cause) -urinalysis -urine culture -radiographs -ultrasound -contrast studies -urolith composition analysis

Question 27

What are the characteristics of radiographs as a urolith diagnostic?

Answer 27

-detect radiodense uroliths -best to determine size, shape, number, and location -may miss uroliths smaller than 1 mm

Question 28

What are the characteristics of ultrasound as a urolith diagnostic?

Answer 28

-most sensitive for small, radiolucent stones and obstructions -less specific for shape, texture, and density

Question 29

What are the components of quantitative stone analysis?

Answer 29

-optical crystallography -spectroscopy

Question 30

What are the four most common stone types seen in companion animals?

Answer 30

-struvite -calcium oxalate -urate/purine -cystine

Question 31

What are the general components of urolith management?

Answer 31

-dissolution -retrieval/removal -prevention

Question 32

What are the principles of dissolution?

Answer 32

-undersaturate urine -minimize urine retention

Question 33

How can urine be undersaturated for stone dissolution?

Answer 33

-dilute urine -optimize pH -minimize analyte excretion -enhance inhibitor concentration/function -eliminate promotors or stone nidus

Question 34

What options exist for increasing water intake for stone dissolution?

Answer 34

-flavored water/purina hydrocare -canned food -adding salt to diet (not recommended) -SQ fluids (last resort)

Question 35

How can diuresis be achieved when needed for stone dissolution?

Answer 35

-ultra-low protein food in dogs only -drugs like furosemide

Question 36

How can urine pH be optimized for stone dissolution/prevention?

Answer 36

-feeding methods -diet selection -acidifying or alkalinizing medication

Question 37

How can analyte excretion be minimized?

Answer 37

-treat metabolic factors -control diet -treat infections -alter metabolism

Question 38

How can conditions for stone prevention/dissolution be optimized?

Answer 38

-eliminate promotors/stone nidus -enhance inhibitors -minimize urine retention

Question 39

What is the typical signalment for struvite stones?

Answer 39

-younger animals -females > males in dogs -females = males in cats -predisposed breed

Question 40

What are the common lab findings in cases with struvite stones?

Answer 40

*UA: -active infection in dogs -alkaline pH > 7.0 -struvite crystals *rads: -radiodense -large -round to pyrimidal -smooth -many stones

Question 41

What are the goals of dissolution therapy for struvite stones?

Answer 41

-resolve any present UTI -achieve urine pH around 6.5 -maintain USG < 1.015

Question 42

What is a practical dissolution strategy for struvite stones?

Answer 42

-antibiotics if infection is present -dissolution diet -increase water intake -possible urinary acidifiers

Question 43

What are the characteristics of antibiotic use in stone dissolution?

Answer 43

-only use if bacteria are present -typically continued for 2 to 4 weeks beyond radiographic resolution of stones -median length of use is 30 days -bacteria can be present in layers of stone; want to continue antibiotics long-term

Question 44

What are the characteristics of a struvite calculolytic diet?

Answer 44

-restriction of magnesium and phosphorus -moderate to low protein (reduced ammonia) -urine pH of 6.0 to 6.5 -canned diet preferred (extra water)

Question 45

What are the characteristics of struvite treatment in cats?

Answer 45

-diet that restricts minerals and reduces ammonium production -increased water intake (canned diets) -antibiotics not needed; typically sterile

Question 46

What are the monitoring steps for struvite dissolution?

Answer 46

*radiograph every 4 weeks (2-3 weeks if sterile or cats) -consider removal if not getting smaller *measure USG -want < 1.015 to 1.020 *urine pH -ideally decreases if alkaline -culture PRN +/- urinary acidifiers

Question 47

What are the key points regarding struvite stones?

Answer 47

-60% of dogs will have full resolution -want to recheck radiographs one month into treatment -should see at least 50% reduction in size after 3 to 4 weeks of therapy to consider it successful -size or number of uroliths is not predictive for dissolution success