Urolithiasis Flashcards
Where can urolithiasis
anywhere in the urinary system
-kidney
-ureters
-bladder
-urethra
more than one place
How might you localize where urolithiasis occurs radiographically
Laterals
VD
Obliques
Buttshots
What is the best tool to localize urolithiasis
Radiographs
can pick up
1) Magnesium ammonium phosphate (Struvite)
2) Calcium oxalate
3) Silicate
4) Ammonium urate?
5) Cystine?
What 5 stones can you pick up radiographically
1) Magnesium ammonium phosphate (Struvite)
2) Calcium oxalate
3) Silicate
4) Ammonium urate?
5) Cystine?
What are your options to visualize radiolucent stones
1) Ultrasound * - typically lower urinary
2) Positive and Double Contrast studies
3) UA- USG, bacteria, WBC, crystals
4) Urine culture
5) Bloodwork - r/p obstruction, azotemia, electrolytes
6) POCUS- free fluid and run creat/K+
7) Renal function tests - USG / GFR
8) ECG if hyperkalemic
what stones are radiolucent
Urates
What are the indications of urolithiasis for surgery *
1) Obstructions of urinary flow
2) Refractory to medical treatment (struvite, urate, cysteine)
-Silica, calcium oxalate, calcium phosphate
-Increasing size
3) Nephroliths and renal dysfunction
4) Anatomical defect
5) Owner compliance
Most commonly, urolithiasis occurs in
the urethra or ureter as these are smaller tubes
What stones might medical treatment via dissolution be favorable for
Struvite
Urate
Cysteine
if they are refractory then there is indication for surgery
What stones are you unable to dissolve
Silica
Calcium oxalate
Calcium phosphate
Nephroliths are only removed if
they cause active renal dysfunction
test for renal function
-BUN, creatinine
-USG
-Perfusion and GFR
T/F: nephroliths always affect renal function
False
test for renal function
-BUN, creatinine
-USG
-Perfusion and GFR
if evidence is there then you might need to remove it
Nephroliths might predispose a dog to
pyelonephritis
What do you do for a patient with bilateral nephroliths
Stage it
-do best kidney first
3-4 weeks between surgeries
What are the surgical options for nephroliths
1) Nephrotomy- incision into the kidney to remove the stone
2) Pyelolithotomy- incision into the renal pelvis to remove the nephrolith
3) Nephrectomy - not a good option
Following nephrotomy, kidney function might be reduced to
10-50% (might be temporary or long-term)
How do you perform nephrotomy
1) Occlusion of blood supply (temporary)
2) Incision on convex surface (greater curvature)
3) Flush ureter and renal pelvis
4) Suture renal capsule
What are the effects of pyelolithotomy
Dilation of the renal pevlis
less effect on renal function as the renal blood supply is not occluded
Why does a pyelolithotomy have less effects on renal function when compared to nephrotomy
because you do not need to occlude renal blood flow
Nephroscopy can be done if
there is dilation of the renal pelvis
use 1.9mm scope in renal pelvis with saline
When is surgery for ureteroliths indicated
1) If not improving after serial radiographs or ultrasounds
2) Complete renal obstruction as you get complete loss of renal function after 4 weeks and ureteral necrosis and stricture can occur
What are the results of a complete ureteral obstruction
complete loss of renal function after 4 weeks
ureteral necrosis or stricture
What are the surgical options for ureteroliths
1) Pyelolithotomy- go through the renal pelvis and flush
2) Ureterotomy +/- stent : incision into ureter
3) Reconstruct the ureter
-reimplantation +/- stent
-bladder tube
4) Subcutaneous Ureteral Bypass - not good option
5) Nephrectomy and ureterectomy - not a good option
What is needed to do Pyelolithotomy
dilated renal pelvis and hydroureter
What is a pyelolithotomy for ureter obstruction
where you make an incision into the renal pelvis (patient needs to have dilated renal pelvis and hydroureter)
do retropulsion flush from bladder into renal pelvis
What species is Uretertomy +/- stent preferred in
Dogs > Cats
cats dont tolerate pigtail stents - dysuric
Uretertomy +/- stent can be done for ureters with
only 1 or 2 stones
What are complications of surgery for ureteroliths
1) Uroabdomen
commonly transient, just remove with drain
2) Swelling obstruction
3) Stricture - obstruction
What is ureter reconstruction
where you ligate section of ureter that has obstruction, cut off, and suture ureter back to bladder, resulting in shorter ureter
not commonly done
What is Subcutaneous Ureteral Bypass (SUB)
a complete bypass where tubing is attached from kidney to connector to bladder
life long medical management
-infection
-encrustation
-migration
-kinking
port that goes outside allows you to flush and collect urine
has to be flushed frequently for life
What are the risks from Subcutaneous Ureteral Bypass (SUB)
life long medical management
-infection
-encrustation
-migration
-kinking
has to be flushed frequently for life
Nephrectomy + ureterectomy depends on
other kidney function
multiple uroliths
*Not a good option for urolithiasis
What are tips for retropulsion of urethral stones in dogs
-general anesthesia
-large rigid catheter
-gauze to grip penis (pinch)
-sterile lubricant (lots of it) and saline
-extra finger for a -rectal if needed
-post procedure radiographs
where you flush stones from the urethra back into the bladder
retropulsion
retropulsion for urehtral stones works
90-95% of the time
Why it is recommended to do retropulsion of urethral stones with general sedation
sedation might work but general anesthesia is recommended to relax
What cather is recommended for retropulsion
Large rigid catheter
Why should you do post procedure radiographs after retropulsion for urethral stones
you cant always tell you got all of the stone with a catheter
they like to hide in the ischial arch
What should you do if you cant do retropulsion of urethral stones
Urethrotomy: first time
or
Urethrostomy: multiple obstructions
T/F: most urethral calculi can be retropulsed into the bladder
True
Urethrotomy is for _______ while urethrostomy is for ________
UrethroTOMY: first time
UrethroSTOMY: multiple (or cat)
T/F: you can do urethrotomy in cats
false- their urethra is too small to open and close again
Urethrostomy is indicated for
Dogs with multiple urethral obstructions or cats
Surgical procedure to make a large urethral opening
Urethrostomy
Surgical procedure to open urethra, take stone out, and close again
Urethrotomy
Why is a urethrostomy done in the scrotal area, as opposed to the pre-scotal area
-Large area
-Superficial
-tension free
-limits hemorrhage
-minimizes urine scale
-dont necessarily have to remove penis
How does the approach for a urethrostomy differ in dogs vs cats
Dogs: Scrotal Urethrostomy
Cats: Perineal Urethrostomy (PU)
What are the benefits of doing urethrostomy in cats with a perineal approach
1) Larger urethral opening
2) Minimizes tension
3) Dissect to the level of the bulbourethral glands (dogs dont have this)
4) Removes penis
When doing a Perineal Urethrostomy (PU) in cats you need to dissect down to the
Bublourethral glands
What approach is a cystotomy performed on
ventral cystostomy
ideally stones are retropulsed into the bladder for removal
When doing a cystotomy, why is it important to start with a urinary catheter in place
so the stones dont go into the urethra during surgery
What approach is a cystotomy done in male dogs
caudal midline and parapreputial approach
-deeper incision at linea alba
When doing cystotomy where do you want to incise the bladder
at the median ligament
When doing a cystotomy where are stay sutures placed
Apex and neck
also helpful in side
When doing a cystotomy you make a stab incision and extend with scissors from the
neck to the apex
What should you do after removing stones when doing a cystotomy
1) Flush retrograde
2) Flush normograde
both through the urethra
this ensures you remove residual minerals
go until you dont feel any gritty
How do you close a cystotomy
4-0 Monofilament rapidly absorbable suture
Taper needle
Full thickness
bite 3mm apart and from edge
submucosa = holding later
simple continuous, appositional
What is the holding layer when doing a cystotomy
Submucosa
With cystotomy closure, full thickness defects gain 100% of normal strength in
14-21 days
can use small monofilament that is rapidly absorbed ie Monocryl, Biosyn
When closing cystotomy, how far should your bites be
3mm apart and from edge
What needle should you use when suturing a cystotomy
Tapered (cutting makes bigger hole in bladder)
T/F: dont do full thickness closure in cystotomy
False - you need to go full thickness because you if you get the mucosa then you will get the submucosa (holding layer)
T/F: full thickness cystotomy suture closure results in long terms bladder mucosal changes
False - you should go full thickness to make sure you get the submucosa
What should you do after closure of cystotomy
Post-operative radiographs to confirm stones not present in the bladder or the urethra
if you see stones, go back to surgery
After cystotomy, what post operative care should you do
-IV fluids, flush blood clots from the bladder / urethra
-Opioids (PRN while hospitalized)
-NSAIDs 5-7d
-Gabapentin 7-10d
-Buprenorphine (cats)
+/- Prazosin if significant spasm or straing
What drug should you give if the patient is having significant spasm or straining after cystotomy
Prazosin
What diagnostics should you do for removed stones
Stone Analysis at Minnesota Urolith Center
Culture - treat as needed
Follow up medical management: diet and urine pH
How long should you wait to recheck after cystotomy
10-14 days
follow up on stone analysis and make recommendations for further treatment, diet, diagnostics, and follow up
What are cystotomy complications
-Superficial incisional complications - 4%
-Uroabdomen due to suture failure <1.5%
-Self resolving hematuria and dysuria 37-50%
-Incomplete urolith removal 14-20%
