Urolithiasis

Question 1

What can contribute to the formation of uroliths?

Answer 1

pH
Retention of urine
Increased concentration of salt
Infection
Decreased concentration of crystalisation inhibitors (GAGs, citrates etc)
Normally a nidus

Question 2

What are the types of urolith that are common

Answer 2

Struvite
Ca Oxalate
Cystine
Purine
Silica
Ca Phosphate
Mixed

Question 3

What can predispose to Ca Oxalate crystals

Answer 3

High calcium
High oxaluria
Ca in the water source
Concurrent disease

Question 4

What can cause calciuria?

Answer 4

Different types.

1. Absorptive - excess absorption in the intestines, leads to renal leak, therefore decreased renal reabsoprtion there fore increased PTH which leads to increased Ca absorption and release in bone
2. Resoptive - excess skeletal mobilisation of Ca - primary hyperparathyroidism

Question 5

What can cause oxaluria?

Answer 5

Produced by metabolism of glyoxalate, glycine, ascorbic acid in the liver and excreted in the urine
AAs from meat protein metabolised to oxalate
Not reported in dogs

Question 6

/How can water source predispose to Ca Ox crystals

Answer 6

Increased Na or Ca in the water
Abscence of Zn which chelates Zn
No studies in dogs
Not a thing in cats

Question 7

What are some inhibitors of Ca Ox?

Answer 7

most important are citrate and Mg as they form a v insoluble complex
Also:
Pyrophosphate - related to Phos, decrease phos, increased risk
GAGs
Nephrocalcin
Tamm Horsfall mucoprotein

Question 8

What concurrent diseases pre-dispose to calcium oxalate?

Answer 8

Cushings
hyper PTH
vitaminosis D
Paraneoplastic hypercalcaemia
Meds - frusemide or steroids

Question 9

How can you dx Ca Ox stones?

Answer 9

UA -ph <6.5
Crystals only may be present
Can be seen on rads
May see high Ca on bloods

Question 10

How do you treat Ca Ox stones?

Answer 10

Not ammenable to dissolution
For obstruction - retrograde hydropulsion then cystotomy or perineal urethrostomy if needed
If stones small enough to pass then increase u+ then repeat rads

Question 11

When should you use surgery to remove uroliths?

Answer 11

Recurrent infections
Blockage
Painful
Severe h+ u+
Increasing in size/ damaging renal tissue
Monitor with rads every 3-6m

Question 12

How should a diet be made for Ca Ox stones?

Answer 12

Increase water intake
Wet diet or  add water
Diet non rich or restricted Ca
Decent phos leves
Moderate Na levels to increase diuresis, but too much predisposes

Question 13

What should you do if the pH is not high enough even with a Ca Ox diet (s/o LUT support or Hills u/d)
Or what if there is still crystaluria?

Answer 13

Add K citrate
Feed moderate to high fibre and low fat
Thiazide diuretics - they decrease urinary Ca excretion, and concentraton, cause subclinical volume depletion which increases proximal tubular reabsorpion of Ca and Na

Question 14

What does K citrate do?

Answer 14

increases urinary pH by decreasing tubular reabsoprtion of citrate and increasing urinary citrate excretion

Question 15

What supplements should be avoided with Ca Ox?

Answer 15

Vits C or D

Question 16

What is the recurrence rate of Ca Ox?

Answer 16

up to 50% in 3 years

Question 17

When is the presence of crystals important?

Answer 17

Previous stones
Crystal that is not struvite or Ca Ox
Predisposed breed
Under treatment

Question 18

Which breeds have a higher occurance of struvites?

Answer 18

Lhasa Apso, Cockers, mini poodle

Question 19

What are Ix findings specific for struvites

Answer 19

Culture more commonly +ve
If negative, ensure an anaerobic culture is performed on the centre of the stone
May see inflammation on bloods

Question 20

How do you monitor dissolution of struvites?

Answer 20

Can take approx 3 months
Imaging and UA every m
Tx 4 weeks beyond radiographic cure
Do Sx if C/S are severe, obstruction, pyelonephritis, immature dog. 
UTI control more important than diet

Question 21

Outline the use of Hills S/d for struvite dissolution

Answer 21

not long term
Low protein, Mg, phos
Acidifies for diuresis
Avoid if pregnant, high BP, renal issue, need for low fat
May cause low BUN and high ALP - if bloods show no changes then O is likely also feeding pet something else

Question 22

What should you do if the diet is not modifying the pH enough?

Answer 22

Consider UTI not being under control

Can give AHA, an inhibitor of urease, however not to patients with renal issues as there are many side effects.

Question 23

What should you consider if the uroliths increase in size despite treatment?

Answer 23

Mixed uroltih
Wrong Dx
Further release of bacteria
non compliant O
Consider sx

Question 24

How do you monitor struvites post dissolution?

Answer 24

Culture approx every 2-4m
Diet alone cannot control struvite stones if present
Consider cystoscopy or bladder biopsy if recurring

Question 25

How do you prevent sterile struvites?

Answer 25

Keep pH 7 Increase water and u+ diet as for UTI struvites

Question 26

What specific Ix are needed for purine stones

Answer 26

Biochem may show underlying disease do BA stim in any breed not a dalmation Rads - are radiolucent so double contrast cystogram for nephroliths US - stones and shunts

Question 27

How do you treat purine stones

Answer 27

Sx if obstruction or PSS Low purine diet - high water Allopurinol (xanthine oxidase inhibitor) Increase pH - aim for 7, can give Na Bicarb or K citrate Tx UTI takes 8-12 weeks hills u/d - no Na, non acidifying, low purine, K citrate in and Ca Carbonate if dog has DCM, can get CHF with low protein diet, so give renal diet and allopurinol

Question 28

What is a caveat to allopurinol treatment?

Answer 28

Must be low protein diet or can get a xanthine shell

Question 29

What pH do you need to prevent cysteine?

Answer 29

>7.2 | Cysteine is freely filtered and actively reabsorbed. If there are stones, there is ddefective absorption

Question 30

What specific ix findings are there with cysteine?

Answer 30

Cyanide nitroprusside test +ve increase AA in urine AA profile Contrast studies needed for rads

Question 31

How can you do medical dissolution of cysteine stones?

Answer 31

``` 2MPG -combines with cysteine to make more soluble, can get s/e Hills u/d diet urine alkalinisers - K+ citrate At least 10 weeks, often a long time Monitor every 4-6 weeks ```

Question 32

How do you prevent cysteine stones

Answer 32

2MPG or u+ alkalinisers Low protein unless has DCM Decreased risk with age

Question 33

Outline silica stones

Answer 33

``` not pH dependent more males, any age GSD/ old english shepherds Jackstone appearance Poss d/t increased excretion of silica Increased plant diet thought to be a risk factor, also talc and kaolin Radiodense ```

Question 34

How do you treat silica stones

Answer 34

Can't disolve Low veg diet Sx if obstructing

Question 35

What can cause Ca Phophate stones/ crystals

Answer 35

UTI from urease high urine pH high ca/ high PTH Can irritate epithelium and be a nidus for struvite

Question 36

How do you treat Ca Phosphate stones?

Answer 36

Often small so high risk of obstruction, so often recommend Sx May need to remove parathyroid if high PTH

Question 37

Who gets dried blood clot stones

Answer 37

Cats

Question 38

outline ureteral stones

Answer 38

Often start in renal pelvis and move causing a partial or complete obstruction can get rupture In dog normall struvite or Ca ox Don't always get signs, may be incidental may not see on rads as so small so U/S easier Most sensitive test for changes in the ureter is excretory urography if no movement in 3-5 days consider intervention Tx - lithotripsy, sx or medical. Can do unilateral nephrectomy if v bad one side and all fine on other

Question 39

Outline excretory urography

Answer 39

Most sensitive test for changes in the ureter May see increased size if obsruction In chronic disease the ureters are dilated and tortuous Avoid in patients with renal issues

Question 40

What are the easiest stones to dissolve with lithotripsy?

Answer 40

Struvite easiest, then Ca Ox, then urate, then cysteine