Page 1211 - Clinical Small Animal Internal Medicine

123 Urolithiasis in Small Animals 1149

retrieval device can be used to remove any remaining nephroliths) seems to worsen renal disease and outcome.
VetBooks.ir urethral calculi through the working channel of the For this reason, removal of nephroliths in people is
encouraged. In small animals, because of the challenges
endoscope.
In patients with embedded urethral stones, laser litho­
evidence that nephroliths are a cause of renal disease
tripsy can be performed. Percutaneous cystotomy can associated with removal of nephroliths and the lack of
also be used to aid in gaining access to the ureters for progression rather than a marker for more aggressive
diagnostic or therapeutic purposes and for resection of renal disease, it is not yet recommended to remove neph­
bladder polyps or diagnostic evaluation of the bladder roliths that are not complicated. Nephrolith removal is
and proximal urethra in dogs that are too small for retro­ not indicated unless uroliths are increasing in size and
grade cystoscopy. compressing the renal parenchyma, causing recurrent
infections despite appropriate duration of medical man­
Laparoscopic‐Assisted Cystoscopy agement, or if the patient has a partial or complete uret­
Laparoscopic‐assisted cystoscopy is performed via a eropelvic junction (UPJ) obstruction resulting in
mini laparotomy. In this technique, the abdomen is hydronephrosis, renal parenchymal loss, worsening renal
insufflated with carbon dioxide and the bladder is iso­ function, chronic hematuria, or pain.
lated. Another trocar is inserted into the abdomen at the
level of the bladder apex, and the bladder is exteriorized Ureteroliths
at this access point using a laparoscopic Babcock forceps. If one or more ureteroliths are obstructing urine flow,
The incision is enlarged, creating a mini laparotomy, to causing hydroureter and/or hydronephrosis, or are asso­
pull the urinary bladder. A small cystotomy is performed ciated with discomfort, hemorrhage, or concurrent pye­
and the bladder wall is sutured to the skin of this small lonephritis, management for medical stone passage or
abdominal incision. A rigid cystoscope is then inserted interventional urinary diversion is indicated immedi­
into the bladder for calculus retrieval. The use of a basket ately, regardless of stone composition, as time is critical.
passed through the working channel or a grasping for­ The presence of a hydroureter without renal pelvic dila­
ceps next to the cystoscope aids in removal of the stones. tion greater than 5 mm is sufficient to suspect ureteral
The cystotomy incision is closed routinely. This proce­ obstruction. If the ureteral obstruction is complete,
dure makes it difficult to maintain bladder distension for decompression of the renal pelvis becomes urgent to
the best visibility. preserve the function of the ipsilateral kidney. The longer
Laparoscopic‐assisted cystoscopy can circumvent the ureter remains obstructed, the more significant and
some of the limitations associated with laser lithotripsy, irreversible the damage. In one study, after seven days of
but it does require creating a pneumoperitoneum, mak­ obstruction, the GFR was permanently diminished by
ing the alternative PCCL very appealing. 35% after relief of the obstruction, and recovery took five
weeks to occur. When the obstruction lasted for 14 days,
the GFR was permanently diminished by 54%, with
Removal of Upper Urinary recovery taking four months to occur. These studies
Tract Uroliths were performed in dogs without preexisting renal or ure­
teral disease, so a worse outcome might be expected in
The incidence of nephroliths and ureteroliths in cats has feline and canine patients with chronic obstructions,
increased as much as 50‐fold since the early 1980s. previous and/or exhausted renal hypertrophy compen­
Calcium oxalate is the most common (>98%) type of sation, and preexisting renal insufficiency. These data
stone found in the upper tract of cats, followed by cal­ suggest that aggressive and timely intervention is neces­
cium phosphate, in the form of apatite, or urate. sary when a ureteral obstruction is diagnosed and that
Approximately 30–60% of ureteroliths in dogs are com­ the “watch and wait method” should be avoided when­
posed of calcium oxalate. ever possible.

Indications for Upper Urinary Tract Medical Management
Urolith Removal
Medical management of upper urinary tract stones
Nephroliths includes dissolution (nephroliths), aggressive diuresis, or
Many canine and feline nephroliths remain static in size intermittent hemodialysis (IHD).
and clinically silent for years. Some controversy exists More than 50% of dogs with ureteral obstructions have
as to whether nonobstructive kidney stones worsen been reported to have urinary tract infection. For that
underlying kidney disease. Most recent studies in human reason, any patient with ureteral obstruction should
and cats show that the presence of nephroliths (vs no have a urine culture performed and should be given the