Page 913 - Small Animal Clinical Nutrition 5th Edition

Feline Lower Urinary Tract Diseases 945

urolithiasis (five cats) or FIC (four cats) (Bass et al, 2005).
VetBooks.ir been incriminated as risk factors for bacterial UTI. These
Several factors associated with perineal urethrostomies have
include decreased length of the urethra after surgery, loss of
normal penile urethral mucosal defense mechanisms, trans-
urethral catheterization, wider external urethral orifices,
impaired function of the striated urethralis muscle and
decreased intraluminal pressure. Some cats have decreased
postprostatic urethral pressure and decreased activity of the stri-
ated muscle sphincter after perineal urethrostomy, as deter-
mined by urethral pressure profiles and electromyographic
changes (Gregory and Vasseur, 1983). These changes were
linked to extensive tissue dissection and damage to the puden-
dal nerve during surgery.
A modified surgical procedure, designed to preserve function
of the striated urethral sphincter, was evaluated in a group of
healthy neutered male cats and a group of cats with persistent
or recurrent urethral obstruction. All cats had normal urethral
pressure profiles and electromyographic results postoperatively.
Twenty-two percent of the cats with persistent or recurrent ure-
thral obstruction had bacterial UTIs vs. none of the normal
cats. These findings suggest that decreased urethral pressure
does not predispose cats to ascending UTI (Griffin et al, 1989).
Vesicourachal diverticula were reported to occur in one of Figure 46-14. Diagram showing a cross-section of a matrix-crys-
every four cats with dysuria, hematuria and/or urethral obstruc- talline urethral plug. Note the spaces previously occupied by struvite
tion (Osborne et al, 1987). Vesicourachal diverticula can be crystals are surrounded by matrix containing amorphous material,
cellular debris and a small number of inflammatory cells. This phe-
congenital or acquired. Diverticula alter the normal flow of
nomenon is analogous to a gelatin salad that contains various fruits
urine; thus in theory, they may predispose patients to UTI, or vegetables (depicting crystals, cells, cellular material) embedded
infection-related urolithiasis and formation of urinary precipi- in a gelatin matrix.
tates. It has been suggested that acquired diverticula occur as a
result of increased intraluminal pressure due to urethral ob-
struction or hyperactivity of the detrusor muscle associated of 47 cats with nonobstructive FIC, 22 cats with obstructive
with inflammation. Spontaneous resolution of diverticula has FIC, 56 cats with signs of upper respiratory tract disease and 46
been observed in cats (Osborne et al, 1987, 1989). asymptomatic cats, FCV was detected by reverse transcription-
polymerase chain reaction (RT-PCR) in urine from approxi-
VIRAL INFECTION mately 6% of cats with FIC or upper respiratory tract disease.
Although not a consistent finding in cats with lower urinary FCV was not detected in urine from any asymptomatic cat.
tract signs, viral infections have been implicated as causative Mean FCV virus neutralizing antibody titers for cats with
agents based on isolation of feline cell-associated herpesvirus, nonobstructive FIC, obstructive FIC and upper respiratory
feline calicivirus (FCV) and syncytia-forming virus from cats tract disease were significantly higher than the mean titers of
with hematuria and dysuria alone or in combination with ure- asymptomatic control cats (Larson et al, 2007). Despite in-
thral obstruction (Kruger and Osborne, 1990). Calicivirus-like creasing evidence that FCV invades the urinary system and that
viral particles have been identified in crystalline/matrix urethral cats with FIC have increased exposure to FCV, establishing a
plugs from cats with obstructive lower urinary tract disease. cause-and-effect relationship between FCV and FIC requires
Although standard cell culture inoculation methods with urine further investigation.
were negative for virus, investigators were able to induce bovine
herpesvirus type 4 (BHV-4) infections experimentally in feline FUNGAL INFECTION
urinary bladders using tissue explantation techniques.However, Fungal UTI is rarely diagnosed in cats; Candida spp. are the
the pathogenic role of BHV-4 in FLUTD remains unclear organisms most often isolated (Pressler et al, 2003; Jin and Lin,
because the prevalence of BHV-4 antibodies in affected cats 2005). Candida spp. are considered a normal part of the genital
was not significantly different from that of clinically normal mucosal flora and most patients with fungal UTI have under-
control cats (Kruger et al, 1991). In a study of 40 cats, lying disorders that alter host defenses against opportunistic
researchers identified FCV in one female cat with FIC and one infection. Some treatments and concomitant disorders diag-
male cat with obstructive FIC; the FCV (FCV-U1 and FCV- nosed in cats with fungal UTI have included administration of
U2) were genetically different from known field and vaccine antimicrobials or corticosteroids, diabetes mellitus, kidney dis-
strains (Rice et al, 2002). In a more recent epidemiologic study ease, indwelling urinary catheters, perineal urethrostomy and