Renal - Urolithiasis Flashcards
What is urolithiasis?
The general term referring to a stone in the urinary tract
What is a nephrolith?
a stone in the kidney
What is a ureterolith?
A stone in the ureter
What is a cystolith?
A stone in the urinary bladder
What is a urethrolith?
A stone in the urethra
True or false: Crystalluria = urolithiasis
NOOOOOOO - the presence of crystals is usually not always a problem
What storage method can cause crystal formation?
refrigeration
What crystals can be problematic?
ammonium urate - breed? liver dz?
Cystine - breed? Proximal tubular dz?
Struvite + bacteriuria - supports stone presence
What is needed to for stone formation?
High solute concentration
What are the multifactorial causes of stone formation?
Increased excretion of metabolites, decreased inhibitors of urolith formation, urine pH, and stone retention
True or False: Clinical signs often reflect location of urolithiasis
True
What clinical signs are associated with lower urinary tract urolithiasis?
hematuria, pollakiuria, stranguria, and obstruction
What clinical signs are associated with upper urinary tract uroliths?
systemic signs (uremia) abdominal pain
What do you do if you suspect a patient has urolithiasis?
IMAGING!!! - Rads or ultrasound
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
What are the cons for radiographs in urolith diagnosis?
Cannot see radiolucent stones
Cannot reliable see soft tissue changes
What are the benefits for ultrasounding in urolith diagnosis?
Identification of radio-opaque/lucent stones
identification of soft tissue abnormalities
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
What uroliths are radio-opaque?
Struvites, calcium oxalate, and silica
What uroliths are radio-lucent?
Cystine and urate stones
What sized stones may be missed on standard radiographs?
small stones (<2mm)
What imaging techniques can be used for urolith diagnosis aside from radiographs and ultrasounding?
contrast cystourethrograms
Does a urinalysis allow for the diagnosis of urolithiasis?
No
How can pH help in diagnosing a urolith?
It can assist in determining the type
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
