Page 1214 - Clinical Small Animal Internal Medicine

1152 Section 10 Renal and Genitourinary Disease

Table 123.4 Considerations for various interventional procedures in patients with partial or complete ureteral obstruction a
VetBooks.ir Procedure Cats Dogs

Medical management ● Indicated within 48 h of ureteral obstruction ● Indicated within 48 h of ureteral obstruction
(aggressive diuresis) ● Contraindicated if patient is unstable (hyperkalemic, ● Contraindicated if patient is unstable
excessively overhydrated, becoming oliguric, or has (hyperkalemic, excessively overhydrated,
cardiac disease) becoming oliguric, or has cardiac disease)
Nephrostomy tube ● Indicated for urgent decompression of the renal pelvis ● Indicated for urgent decompression of the renal

if ESWL and ureteral stenting not available pelvis if ESWL and ureteral stenting not available
● Renal pelvis must be >10 mm ● Renal pelvis must be >10 mm
● Surgically placed; percutaneous placement not ● Percutaneously placed
recommended because of increased risk of
uroabdomen due to mobility of feline kidneys
ESWL ● Indicated for ureteroliths <3 mm ● Indicated for ureteroliths <5 mm
● Add ureteral stent if ureterolith is between 3 and ● Add ureteral stent if ureterolith is >5 mm or
5 mm or obstruction is present obstruction is present
Ureteral stents ● Indicated for obstructive ureteroliths (any degree of ● Indicated for any obstructive ureterolith
hydroureter and hydronephrosis) ● Placed retrograde (cystotomy or cystoscopy) or
● Placed antegrade via nephrostomy access antegrade (percutaneous or surgical
● Placed retrograde via cystoscopy or ureterotomy nephrostomy access)
Ureteroscopy Not performed because of small patient size ● Indicated for dogs >18 kg
● Ureteral stents placed when complete obstruction
SUB ● Current preferred method for ureteral obstruction in ● Indicated for ureteral stent reactions or
cats intolerance or recurrence of occlusion
● Indicated for ureteral strictures or very proximal
ureteral obstructions
● Indicated for ureteral stent reactions
Ureterotomy or If deemed appropriate by attending surgeon If deemed appropriate by attending surgeon
ureteral reimplantation
a Immediate treatment of partial ureteral obstruction is typically recommended.
Source: Reproduced with permission from Defarges A, Berent AC, Dunn M. New alternatives for minimally invasive management of uroliths:
ureteroliths. Compend Contin Educ Vet 2013; 35(3): E1–E7.
ESWL, extracorporeal shock wave lithotripsy; SUB, subcutaneous ureteral bypass.

Extracorporeal Shock Wave Lithotripsy nephrolith could become an obstructive ureterolith after
Extracorporeal shock wave lithotripsy is used to fragment ESWL. Post ESWL, nephrolith fragments are typically
uroliths fixed in one location. It has been successfully used ≥1 mm in diameter, and the typical unstented feline ureter
to fragment nephroliths and ureteroliths in dogs and uret­ is 0.3–0.4 mm in diameter. Second, there is some concern
eroliths in cats. The patient is placed under general anes­ that feline kidneys are more sensitive than canine kidneys
thesia to permit positioning and provide analgesia. to shock waves and could experience bleeding.
Fluoroscopy is used to position the ESWL unit to target Extracorporeal shock wave lithotripsy treatment was
the urolith. If compromised renal function is of concern, or reported to be successful in approximately 85% of dogs
if bilateral ESWL is to be performed concurrently, limiting with calcium‐containing nephroliths and ureteroliths.
treatment to a maximum of 2000–2500 shock waves per Successful fragmentation of renal stones was achieved
kidney is recommended. For uroliths in the distal ureter or in 90% of dogs, but some dogs required multiple treat­
urinary bladder, higher doses are possible because the kid­ ments. Overall, 30% of dogs required more than one
ney is not within the treatment focal zone and collateral ESWL treatment for adequate fragmentation of neph­
damage to surrounding tissues seems to be minimal. roliths when lithotripsy was used; when an older model
Extracorporeal shock wave lithotripsy is most com­ dry unit (Modulith SL‐20) was used, up to 50% of dogs
monly recommended for the treatment of nephroliths and required more than one treatment. Success rates
ureteroliths in dogs, rather than cats, for two reasons. approach ~85% with one treatment when ureteral
First, the feline ureter does not routinely accommodate stenting is concurrently performed. In one study of five
nephrolith fragment passage. Therefore, a nonobstructive cats with ureterolithiasis treated by ESWL (wet unit),