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SAM Module B Urinary system > Urolithiasis > Flashcards

Urolithiasis Flashcards

1
Q

What can contribute to the formation of uroliths?

A 
pH
Retention of urine
Increased concentration of salt
Infection
Decreased concentration of crystalisation inhibitors (GAGs, citrates etc)
Normally a nidus
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2
Q

What are the types of urolith that are common

A 
Struvite
Ca Oxalate
Cystine
Purine
Silica
Ca Phosphate
Mixed
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3
Q

What can predispose to Ca Oxalate crystals

A

High calcium
High oxaluria
Ca in the water source
Concurrent disease

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4
Q

What can cause calciuria?

A

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
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5
Q

What can cause oxaluria?

A

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

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6
Q

/How can water source predispose to Ca Ox crystals

A

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

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7
Q

What are some inhibitors of Ca Ox?

A

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

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8
Q

What concurrent diseases pre-dispose to calcium oxalate?

A 
Cushings
hyper PTH
vitaminosis D
Paraneoplastic hypercalcaemia
Meds - frusemide or steroids
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9
Q

How can you dx Ca Ox stones?

A

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

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10
Q

How do you treat Ca Ox stones?

A

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

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11
Q

When should you use surgery to remove uroliths?

A 
Recurrent infections
Blockage
Painful
Severe h+ u+
Increasing in size/ damaging renal tissue
Monitor with rads every 3-6m
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12
Q

How should a diet be made for Ca Ox stones?

A 
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
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13
Q

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?

A

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

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14
Q

What does K citrate do?

A

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

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15
Q

What supplements should be avoided with Ca Ox?

A

Vits C or D

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16
Q

What is the recurrence rate of Ca Ox?

A

up to 50% in 3 years

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17
Q

When is the presence of crystals important?

A

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

18
Q

Which breeds have a higher occurance of struvites?

A

Lhasa Apso, Cockers, mini poodle

19
Q

What are Ix findings specific for struvites

A

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

20
Q

How do you monitor dissolution of struvites?

A 
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
21
Q

Outline the use of Hills S/d for struvite dissolution

A

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

22
Q

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

A

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.

23
Q

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

A 
Mixed uroltih
Wrong Dx
Further release of bacteria
non compliant O
Consider sx
24
Q

How do you monitor struvites post dissolution?

A

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

25
Q

How do you prevent sterile struvites?

A

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

26
Q

What specific Ix are needed for purine stones

A

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

27
Q

How do you treat purine stones

A

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

28
Q

What is a caveat to allopurinol treatment?

A

Must be low protein diet or can get a xanthine shell

29
Q

What pH do you need to prevent cysteine?

A

> 7.2

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

30
Q

What specific ix findings are there with cysteine?

A

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

31
Q

How can you do medical dissolution of cysteine stones?

A 
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
32
Q

How do you prevent cysteine stones

A

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

33
Q

Outline silica stones

A 
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
34
Q

How do you treat silica stones

A

Can’t disolve
Low veg diet
Sx if obstructing

35
Q

What can cause Ca Phophate stones/ crystals

A

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

36
Q

How do you treat Ca Phosphate stones?

A

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

37
Q

Who gets dried blood clot stones

A

Cats

38
Q

outline ureteral stones

A

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

39
Q

Outline excretory urography

A

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

40
Q

What are the easiest stones to dissolve with lithotripsy?

A

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

SAM Module B Urinary system (13 decks)

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