Renal - Urolithiasis Flashcards by Jessica Carson

What is urolithiasis?

The general term referring to a stone in the urinary tract

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What is a nephrolith?

a stone in the kidney

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What is a ureterolith?

A stone in the ureter

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What is a cystolith?

A stone in the urinary bladder

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What is a urethrolith?

A stone in the urethra

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True or false: Crystalluria = urolithiasis

NOOOOOOO - the presence of crystals is usually not always a problem

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What storage method can cause crystal formation?

refrigeration

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What crystals can be problematic?

ammonium urate - breed? liver dz?
Cystine - breed? Proximal tubular dz?
Struvite + bacteriuria - supports stone presence

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What is needed to for stone formation?

High solute concentration

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What are the multifactorial causes of stone formation?

Increased excretion of metabolites, decreased inhibitors of urolith formation, urine pH, and stone retention

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True or False: Clinical signs often reflect location of urolithiasis

True

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What clinical signs are associated with lower urinary tract urolithiasis?

hematuria, pollakiuria, stranguria, and obstruction

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What clinical signs are associated with upper urinary tract uroliths?

systemic signs (uremia) abdominal pain

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What do you do if you suspect a patient has urolithiasis?

IMAGING!!! - Rads or ultrasound

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What are the benefits for radiographs in urolith diagnosis?

View of entire urinary tract
Better resolution of stone number/size/shape
Identification of stone helps predict stone composition

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What are the cons for radiographs in urolith diagnosis?

Cannot see radiolucent stones

Cannot reliable see soft tissue changes

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What are the benefits for ultrasounding in urolith diagnosis?

Identification of radio-opaque/lucent stones

identification of soft tissue abnormalities

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What are the cons to ultrasounding in urolith diagnosis?

Limited visualization of the urethra
Poor capacity to determine stone number/size/shape
Cannot use imaging to predict stone composition

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What uroliths are radio-opaque?

Struvites, calcium oxalate, and silica

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What uroliths are radio-lucent?

Cystine and urate stones

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What sized stones may be missed on standard radiographs?

small stones (<2mm)

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What imaging techniques can be used for urolith diagnosis aside from radiographs and ultrasounding?

contrast cystourethrograms

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Does a urinalysis allow for the diagnosis of urolithiasis?

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How can pH help in diagnosing a urolith?

It can assist in determining the type

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How can crystalluria help in diagnosing a urolith?

It can assist in determining the type of you know a stone is present

How is USG important in urolithiasis?

High USG can be a risk factor and it is an important monitoring component of therapy

What additional testing can be done for urolith diagnosis?

Testing for Azotemia, portosystemic shunt, and pyelonephritis

Why can predicting stone composition be useful?

Determine the optimum treatment - surgery or dissolution? Concurrent surgical procedures?

Why is stone analysis important?

It is the only way to definitively identify the stone type Helps determine optimum therapy Helps identify concurrent diseases

How is stone analysis done?

Chemical/optical analysis of the stone

What is the most common canine urolith (it is the 2nd most common in cats)?

Calcium oxalate (CaOX) uroliths

What breeds are predisposed to CaOX uroliths?

Miniature Schnauzer, Shih Tzu, Bichon Frise, and yorkies

What is the etiology of CaOx uroliths?

Poorly characterized - genetics, increased Ca an doxalate excretion, and diet acidification

What will CaOx uroliths look like on radiographs?

Radioopaque and can be round or spiculated

What will you see on UA in patients with CaOX uroliths?

Form in acidic urine (<6.5) May or may not be crystals Pyuria/bacteriuria can present as a consequence NOT A CAUSE

How are CaOX stones treated?

They cannot be resolved - so removal is the only option

What is the prevention plan for CaOX uroliths?

Canned food, avoid high Na and high protein +/- medications: potassium citrate and hydrochlorothiazide Monitor - USG and pH Repeat imaging every 3-6 months

When should you consider CaOX to be a chronic disease?

If they recur in 2 years - treat the contributing pathology (hypercalcemia)

What are the goals of CaOX tharpy?

neutral pH and low USG

What is the second most common canine urolith (most common in a cat)?

struvite uroliths

What breeds are most commonly affected by struvites?

Min Schnauzer, Shih Tzu, Bichon Frise, and Dachshunt

What is almost always the cause of struvites?

UTI - they are almost always secondary to them because of urease-producing bacteria causing an increased pH

True or False: Struvites are almost always sterile.

True

What will you see radiographically with a struvite?

Radioopaque and smooth/rount

What will a UA show in a patient with struvites?

Alkaline pH, crystals may or may not be resent, Pyuria/bacteriuria can be present

How are struvites treated?

Dissolution - medical dissolution should be the first line treatment in non-obstructed cases

What diet can aid in treatment of struvites?

Canned dissolution diet - lower protein diets, USG <1.020 and a pH of <6.5

If you use an antibiotic to treat a struvite, what do you want to target? For how long

The underlying cause - until complete dissolution

How are struvates monitored?

Repeat radiographs every 2-4 weeks during dissolution (complete dissolution 6-8 weeks for sterile and 8-12 weeks for infection) Aggressive treatment of UTIs

What is the 3rd most common urolith type for both cats/dogs?

Urate uroliths

What breeds most commonly get urate uroliths? Why?

Dalmations, English Bulldogs, Black Russian Terriers | Altered hepatic urate transporter

What anatomic abnormalities (not in the urinary tract) can lead to urate uroliths?

Portosystemic shunts - increased urinary excretion of uric acid an dammonia

What do urate uroliths look like on radiographs?

Radiolucent to mildly radioopaque | Round shapte

What will you find on UA in patients with urate uroliths?

Acidic urine (pH <6.8) +/- ammonium biurate crystals +/- secondary bacterial infection

What initial diagnostics can be done for urate uroliths?

Consider serum bile acids and other Dx when found in breeds that are not predisposed to urates

How are urate uroliths treated?

Surgical removal because dissolution is rarely effective

What are the goals of treatment for urate urolithiasis?

Decreased USG to <1.020 | pH >6.6

What diets can be used to manage urate uroliths?

Low purine diets (Hill's U/D)

What additional therapies can be used to treat urate uroliths?

Urine alkalization - potassium citrate Allopurinol PSS repair

Cystine uroliths are most common in what breed of dog? Sex?

English Bulldogs, Newfoundland, Mastiff | 98% of cases are males

What causes cystine uroliths?

A defect in proximal tubular reabsorption of cystine - autosomal recessive mutation identified

What will you see on radiographs in patients with cystine uroliths?

Radiolucent to mildly radioopaque | Smooth/round shape

What will you find on UA in patients with cystine uroliths?

Acidic pH (<7) Crystals may or may not be present Pyuria/bacteriuria can be present

How are cystine uroliths treated?

Medical removal +/- dissolution

Aside from medical removal, what can be done for cystine uroliths?

Low protein diets +/- castration reduces cystine excretion in some dogs +/- potassium citrate +/- 2-MPG: cystine chelator

What are the goals of therapy for cystine uroliths?

pH >7.5 and USG >1.020

What are the removal options (general) for urolith removal?

Benign neglect, surgery, and minimally-invasive options

What surgical options are there for urolith removal?

cystotomy and urethrotomy

What minimally-invasive options are there for urolith removal?

Voiding urodydropropulsion Cystoscopy + laser lithotripsy and removal Percutaneous cystolithotomy

When is benign neglect reasonable?

When there are no clinical signs

What is the most commonly used surgical removal technique for stone removal?

cystotomy - do post op rads after

What should you do instead of a urethrotomy?

Retropulse stones into the bladder instead or consider cystoscopy

What is urohydropulsion?

Place the patient in a verticle position under anesthesia Manual bladder expression Have a container for stone/urine collection - max size 4mm

What is cystoscopy + laser lithotripsy?

Visualize, fragment with a laser (lithotripsy), and remove via urohydropropulsion

What is percutaneous cystolithotomy?

Make a small incision in the abdomen and bladder. Go in with a scope and remove the stone that way