Page 700 - Small Animal Internal Medicine, 6th Edition

672 PART V Urinary Tract Disorders

URODYNAMIC TESTING infused and intravesical pressure are monitored on the
computer screen.
VetBooks.ir Urodynamic testing can be useful in animals presented for Procedure
URETHRAL PRESSURE PROFILE
evaluation of urinary incontinence, especially those refrac-
extent. Many drugs (e.g., inhalant anesthetics) can abolish
tory to standard treatment. The urethral pressure profile As for the UPP, all drugs affect the detrusor reflex to some
(UPP) evaluates pressure along the length of the urethra. the reflex and, ideally, the CMG should be done without
This test is indicated for dogs with refractory urethral sphinc- sedation, but usually doing so is not practical. Intravenously
ter mechanism incompetence (USMI) or for dogs with USMI administered propofol can be used for this procedure. Once
for which medications may cause potentially serious adverse the animal is sedated, a double-lumen urinary catheter is
effects. It usually is unnecessary in dogs that present for aseptically placed into the urinary bladder of the dog or cat.
uncomplicated urinary incontinence suspected to be caused One of the ports is connected to the pressure transducer on
by USMI. A UPP also can be used to screen dogs with ectopic the machine and the other is used for fluid administration.
ureters before surgical or laser correction. The screening Sterile water is infused at a constant rate. The rate of fluid
might suggest concurrent USMI and provide evidence that infusion is very important and should be calculated based
medication to treat this condition may be needed after on patient size. Pressures are measured as the bladder is filled
ectopic ureter correction. Finally, UPP can be considered to with water, indicating the degree of compliance of the
evaluate dogs and cats with suspected functional urethral bladder. Resting bladder pressure, threshold pressure (the
outflow tract obstruction. pressure at which the detrusor reflex occurs), and threshold
volume (the volume at which the detrusor reflex occurs) are
Procedure recorded. Bladder compliance then can be calculated.
A UPP can be obtained on a male or female dog, and this
test can be done on most cats. Urinary tract infections should
be treated appropriately before performing urodynamic URETHROCYSTOSCOPY
procedures.
All anesthetics will decrease urethral closure pressure to Urethrocystoscopy using a rigid cystoscope allows visual
some extent, but performing this procedure without seda- inspection of the mucosal surfaces of the vestibule, vagina,
tion can be challenging. If chemical restraint is necessary, urethra, ureteral orifices, and bladder in female dogs and cats
a bolus of propofol (2–3 mg/kg IV) can be given to facili- weighing > 3 kg. It is a valuable technique for the diagnosis
tate placement of the urinary catheter. Once the animal is of several lower urinary tract disorders, including ectopic
sedated, a double- or triple-lumen catheter (of appropriate ureter, urachal remnant, proliferative urethritis, polypoid
size) is inserted via the urethra to the level of the bladder cystitis, and transitional cell carcinoma of the bladder or
trigone. The catheter is slowly withdrawn at a standard rate urethra. It is the gold standard for the diagnosis of ectopic
(0.5–1 mm/sec) while warm sterile water is infused at a rate ureters in dogs and is valuable for identifying the termina-
of 2 mL/min. This procedure generates a pressure curve that tion sites of ectopic ureters. It allows a presumptive diagnosis
can be visualized on the computer screen. From this curve, of transitional cell carcinoma of the urethra or bladder and
the maximal urethral closure pressure is determined, which permits a biopsy to be performed in a minimally invasive
is the maximal urethral pressure minus the resting bladder manner. Female dogs with recurrent UTIs can be evaluated
pressure. The UPP can be obtained in female cats, but cath- for predisposing anatomic abnormalities. The technique also
eters of appropriate size for male cats are not commercially is useful for the diagnosis of idiopathic renal hematuria in
available. dogs and allows identification of the kidney responsible for
hemorrhage by observing the discharge of bloody urine from
CYSTOMETROGRAPHY the ureteral orifice on the affected side. Urethrocystoscopy
Cystometrography (CMG) can be performed to evaluate also can be used to treat sphincter mechanism incompetence
detrusor function in dogs and cats. This study evaluates by submucosal injection of collagen in the urethra, to remove
the detrusor reflex, bladder filling volume, and compli- small cystic calculi in female dogs by voiding hydropulsion,
ance. Referral for this procedure generally is indicated for and to perform lithotripsy.
dogs and cats with refractory USMI or those with persis-
tent pollakiuria for which underlying causes, such as bac-
terial cystitis, urolithiasis, neoplasia, and polypoid cystitis, RENAL BIOPSY
have been ruled out. CMG also can be used to evaluate
dogs and cats with suspected detrusor atony. To perform Renal biopsy allows the clinician to establish a histologic
this procedure, the patient is anesthetized with propo- diagnosis and should be considered when the information
fol and a catheter is inserted into the bladder. The cath- obtained is likely to alter patient management. Examples of
eter is connected to pressure transducers and the bladder such situations include differentiation of protein-losing glo-
is slowly filled with sterile warm water at a constant rate, merular diseases, differentiation of AKI from CKD, determi-
calculated based on the animal’s body size. The volume nation of the status of tubular basement membranes in AKI,