Page 1179 - Clinical Small Animal Internal Medicine

122 Obstructive Uropathy 1117

be considered to avoid this potential development, albeit Prognosis
VetBooks.ir with a possible increased stent infection rate, in the Depending on the underlying cause, there is an approxi­
authors’ experience.
mately 15–40% incidence of recurrence with feline UO.
Alternative Management Protocols for Feline UO With repeated obstructive episodes, it may be necessary
to consider perineal urethrostomy (PU). This procedure
Unfortunately, the ability to provide the optimal treat­ will decrease risk of UO, though will not impact underly­
ment course (close monitoring, IV and urinary catheteri­ ing FIC if present. In addition, patients with a PU may be
zation) may be limited by owner financial constraints. at increased risk for UTI.
Predicated on the notion that there is a component of Prognosis for UO in dogs is even more dependent on
functional obstruction (urethral edema and spasm), it the underlying cause. Obstruction secondary to urolithi­
has been demonstrated that pharmacologic manipula­ asis is generally very good with successful catheteriza­
tion (buprenorphine and acepromazine +/‐ dexmedeto­ tion and stone removal, though there is potential for
midine), a low‐stress environment, and intermittent recurrence. Proper dietary management to decrease
cystocentesis can result in spontaneous urination with­ stone formation may help decrease this risk. Prognosis
out the need for catheterization. This approach was for bladder/urethral/prostatic neoplasia is guarded, with
successful in achieving spontaneous urination in approx­ palliative efforts (chemotherapy, radiation, urethral
imately 75% of cats in one study. However, while a rea­ stenting) only providing temporary relief. Reported
sonable alternative to euthanasia, this protocol cannot median survival for dogs with urothelial malignancy
be recommended in lieu of traditional management varies from days to nearly one year after diagnosis,
(which carries a reported success rate of 91–94%) as depending on the severity of disease and the treatment
no direct comparison between the two has been made. pursued.
Further, severely debilitated cats in need of emergency
stabilization, based on significant physical exam/meta­
bolic derangements, should be excluded from this Ureteral Obstruction
protocol.
In some cases, financial limitations might preclude the
ability to hospitalize for treatment. Under those circum­ Etiology/Pathophysiology
stances, it may be necessary to offer euthanasia, especially Ureteral obstruction in small animals results from uro­
for severely affected patients (hypothermia, bradycardia, lithiasis, stricture, blood clots, congenital anomalies
lateral recumbency, etc.). For those patients presenting (ureteropelvic junction stenosis), neoplasia, external
in the earlier stages of obstruction that are not yet sig­ compression, severe ureteritis, or as a functional conse­
nificantly ill, it may be possible to provide care on an out­ quence of urethral obstruction. In nearly all cats and
patient basis, though this should be reserved as a last most dogs, urolithiasis is identified as the underlying
resort. One option would be to provide sedation and cause. A rare cause of ureteral stricture is the presence of
analgesia (acepromazine and buprenorphine) and blad­ a circumcaval ureter, reported in four of 10 cats with
der decompression through either passage of a urinary strictures in one series and also reported in case reports
catheter or cystocentesis. Catheterization would offer of dogs. The consequences of ureteral obstruction vary
the benefit of removing any physical obstruction within depending on several factors: whether one or both kid­
the urethra but could also result in damage or irritation neys are affected, the acuity versus chronicity of the dis­
to the urethral and an increased risk of reobstruction. ease, whether the obstruction is partial or complete, and
Cystocentesis would likely be less expensive to perform the presence of any complicating co‐morbidities, such as
and less injurious to the urethra, but might only provide infection.
temporary relief if a significant physical obstruction Ureteral obstruction may be complete or partial,
is present. depending on whether any urine is able to flow beyond
In either approach, the patient would be discharged in the site of obstruction. The degree of obstruction dic­
the hopes that continued analgesia and sedation will tates the severity of any rise in hydrostatic pressure
allow for spontaneous urination to occur. Aside from exerted upstream of the obstruction – to the proximal
anecdotal reports and clinical experience, there is no evi­ ureter, renal pelvis, and renal parenchyma. The effect of
dence to support the merits of either of these approaches, this increased pressure on the proximal ureter and renal
nor is there information regarding the likelihood of suc­ pelvis is passive dilation of these structures, which can
cess or recurrence. The client would have to be well become profound (Figure 122.9).
informed of the potential for treatment failure, and fol­ Similar to UO, the increased pressure upstream of a
low‐up phone calls to determine response would be ureteral obstruction is transmitted from the renal pelvis
strongly recommended. to the renal parenchyma, specifically to the nephron and