Objective—To determine hospital proportional morbidity
rates (HPMR) for urethral obstructions, urethral
plugs or urethroliths, and urethrostomies in cats in
veterinary teaching hospitals (VTH) in Canada and the
United States between 1980 and 1999.
Animals—305,672 cats evaluated at VTH.
Procedures—Yearly HPMR were determined for cats
with urethral obstructions, urethral plugs or urethroliths,
or urethrostomies from data compiled by
the Purdue Veterinary Medical Database. The test for
a linear trend in proportions was used.
Results—Urethral obstructions were reported in 4,683
cats. Yearly HPMR for urethral obstructions declined
from 19 cases/1,000 feline evaluations in 1980 to 7
cases/1,000 feline evaluations in 1999. Urethral plugs
or urethroliths affected 1,460 cats. Yearly HPMR for
urethral plugs or urethroliths decreased from 10
cases/1,000 feline evaluations in 1980 to 2 cases/1,000
feline evaluations in 1999. A total of 2,359 urethrostomies
were performed. Yearly HPMR for urethrostomies
decreased from 13 cases/1,000 feline evaluations
in 1980 to 4 cases/1,000 feline evaluations in
Conclusions and Clinical Relevance—Frequency of
feline urethrostomies performed at VTH in Canada and
the United States declined during the past 20 years
and paralleled a similar decline in frequency of urethral
obstructions and urethral plugs or urethroliths. These
trends coincide with widespread use of diets to minimize
struvite crystalluria in cats, which is important
because struvite has consistently been the predominant
mineral in feline urethral plugs during this period.
(J Am Vet Med Assoc 2002;221:502–505)
Objective—To identify demographic factors associated with urate urolithiasis in cats and determine whether the rate of urolith submission to a laboratory had changed over time.
Design—Case series and case-control study.
Animals—Cases consisted of 5,072 cats with urate uroliths submitted to the Minnesota Urolith Center between January 1, 1981, and December 31, 2008. Controls consisted of 437,228 cats without urinary tract diseases identified in records of the Veterinary Medical Database during the same period.
Procedures—Information on cat breed, age, sex, reproductive status, and location of uroliths was used to identify risk factors. Changes in annual urolith submission rates were evaluated.
Results—Purebred cats had significantly higher odds of developing urate uroliths than did cats of mixed breeding (reference group). On the other hand, cats of the Abyssinian, American Shorthair, Himalayan, Manx, and Persian breeds had significantly lower odds of developing urate uroliths than did mixed breeds. Neutered cats were 12 times as likely to develop urate uroliths as were sexually intact cats. Cats in all age groups had significantly increased odds of developing urate uroliths, compared with cats < 1 year of age (reference group). Cats ≥ 4 but < 7 years of age had the highest odds of all groups and were 51 times as likely to develop urate uroliths as were cats < 1 year of age. Urolith submission rates did not change significantly with time.
Conclusions and Clinical Relevance—Findings of this study suggested that the typical cat with urate uroliths was a purebred neutered cat, 4 to 7 years old, with uroliths in the bladder or urethra. This information may be helpful in predicting mineral composition of uroliths in vivo. However, no conclusions can be made regarding cause-and-effect relationships.
Objective—To determine proportional morbidity rates
(PMR) and risk factors for lower urinary tract diseases
(LUTD) in cats.
Sample Population—Records of 22,908 cats with
LUTD and 263,168 cats without LUTD.
Procedure—Data were retrieved from the Purdue
Veterinary Medical Data Base. Descriptive statistics
and univariate logistic regression analyses were performed
to assess whether breed, age, sex, and neutering
status were associated with different causes of
Results—Mean PMR for LUTD irrespective of cause
was 8/100 cats (range, 2 to 13/100 cats). Increased
risk for urocystolithiasis (Russian Blue, Himalayan,
and Persian cats), bacterial urinary tract infections
(UTI; Abyssinian cats), congenital urinary tract defects
(Manx and Persian cats), and urinary incontinence
(Manx cats) was detected. Cats between 2 and < 7
years of age had increased risk for urethral plugs, neurogenic
disorders, congenital defects, and iatrogenic
injuries. Cats between 4 and < 10 years of age had
increased risk for urocystolithiasis, urethral obstructions,
and idiopathic LUTD. Cats ≥ 10 years of age had
increased risk for UTI and neoplasia. Castrated males
had increased risk for each cause of LUTD except UTI
and incontinence. Spayed females had increased risk
for urocystolithiasis, UTI, and neoplasia. Sexually
intact females had decreased risk for each cause of
LUTD except neurogenic disorders and iatrogenic
Conclusion and Clinical Relevance—Specific breed,
age, sex, and neutering status may be associated with
specific types of feline LUTD. Knowledge of patient
risk factors for LUTD may facilitate development of
surveillance strategies that enhance earlier detection.
(J Am Vet Med Assoc 2001;218:1429–1435)
Objective—To test the hypothesis that urate uroliths
are uncommonly detected in female Dalmatians,
compared with males.
Sample Population—Medical records of dogs evaluated
at veterinary teaching hospitals in North America
from 1981 to 2002 and compiled by the Veterinary
Medical Database, and records of dogs with uroliths
submitted for quantitative analyses to the Minnesota
Urolith Center from 1981 to 2002.
Procedures—Crude odds ratios (ORs) and 95% confidence
intervals were calculated to assess whether
sex (male vs female) was a risk factor for urate
Results—In Dalmatians evaluated by veterinary
teaching hospitals in North America, males were
more likely (OR, 13.0) to form uroliths, compared with
females. In Dalmatians that formed uroliths analyzed
by the Minnesota Urolith Center, males were more
likely (OR, 14.0) to form urate uroliths, compared with
females. In all dogs (Dalmatian and non-Dalmatian)
that formed uroliths analyzed by the Minnesota
Urolith Center, males were also more likely (OR, 48.0)
to form urate uroliths, compared with females.
Conclusions and Clinical Relevance—When conducting
studies and formulating generalities about
urate urolithiasis in Dalmatians, it is important to consider
sex-related differences in urolith occurrence.
Long-term dietary or drug protocols designed to minimize
formation of urate uroliths in male Dalmatians
may not be warranted in female Dalmatians. (J Am
Vet Med Assoc 2005;227:565–569)
Objective—To determine whether hydrochlorothiazide
(HCTZ) reduces urinary calcium excretion in
dogs with calcium oxalate urolithiasis.
Animals—8 dogs with calcium oxalate urolithiasis.
Procedure—4 treatment protocols were evaluated in
each dog (a low calcium, low protein diet designed to
prevent calcium oxalate urolith formation with and
without administration of HCTZ [2 mg/kg (0.9 mg/lb)
of body weight, PO, q 12 h] and a maintenance diet
with higher quantities of protein and calcium with and
without administration of HCTZ). At the end of each 2-week treatment period, 24-hour urine samples were collected. Blood samples were collected during the
midpoint of each urine collection period. Analysis of
variance was performed to evaluate the effects of
HCTZ and diet on urine and serum analytes.
Results—Hydrochlorothiazide significantly decreased
urine calcium and potassium concentration and excretion.
Hydrochlorothiazide also significantly decreased
serum potassium concentration. Compared with the
maintenance diet, the urolith prevention diet significantly
decreased urine calcium and oxalic acid concentration
and excretion. Dogs consuming the urolith
prevention diet had significantly lower serum concentrations
of albumin and urea nitrogen.
Conclusions and Clinical Relevance—Administration
of HCTZ decreased urine calcium excretion
in dogs with a history of calcium oxalate urolith formation.
The greatest reduction in urine calcium concentration
and excretion was achieved when dogs
received HCTZ and the urolith prevention diet.
Results of this study suggest that the hypocalciuric
effect of HCTZ will minimize recurrence of calcium
oxalate urolith formation in dogs; however, long-term
controlled clinical trials are needed to confirm the
safety and effectiveness of HCTZ. (J Am Vet Med
Objective—To determine effects of storage temperature
and time on pH and specific gravity of and number
and size of crystals in urine samples from dogs
Design—Randomized complete block design.
Animals—31 dogs and 8 cats.
Procedure—Aliquots of each urine sample were analyzed
within 60 minutes of collection or after storage
at room or refrigeration temperatures (20 vs 6°C [68
vs 43°F]) for 6 or 24 hours.
Results—Crystals formed in samples from 11 of 39
(28%) animals. Calcium oxalate (CaOx) crystals
formed in vitro in samples from 1 cat and 8 dogs.
Magnesium ammonium phosphate (MAP) crystals
formed in vitro in samples from 2 dogs. Compared
with aliquots stored at room temperature, refrigeration
increased the number and size of crystals that
formed in vitro; however, the increase in number and
size of MAP crystals in stored urine samples was not
significant. Increased storage time and decreased
storage temperature were associated with a significant
increase in number of CaOx crystals formed.
Greater numbers of crystals formed in urine aliquots
stored for 24 hours than in aliquots stored for 6
hours. Storage time and temperature did not have a
significant effect on pH or specific gravity.
Conclusions and Clinical Relevance—Urine samples
should be analyzed within 60 minutes of collection to
minimize temperature- and time-dependent effects on
in vitro crystal formation. Presence of crystals observed
in stored samples should be validated by reevaluation of
fresh urine. (J Am Vet Med Assoc 2003;222:176–179)
Objective—To determine whether nephrolithiasis was associated with an increase in mortality rate or in the rate of disease progression in cats with naturally occurring stage 2 (mild) or 3 (moderate) chronic kidney disease.
Design—Retrospective case-control study.
Animals—14 cats with stage 2 (mild) or 3 (moderate) chronic kidney disease (7 with nephroliths and 7 without).
Procedures—All cats were evaluated every 3 months for up to 24 months. Possible associations between nephrolithiasis and clinicopathologic abnormalities, incidence of uremic crises, death secondary to renal causes, and death secondary to any cause were evaluated.
Results—There were no clinically important differences in biochemical, hematologic, or urinalysis variables between cats with and without nephroliths at baseline or after 12 and 24 months of monitoring. No associations were detected between nephrolithiasis and rate of disease progression, incidence of uremic crises, or death.
Conclusions and Clinical Relevance—Results suggested that in cats with mild or moderate chronic kidney disease, nephrolithiasis was not associated with an increase in mortality rate or in the rate of disease progression. Findings support recommendations that cats with severe kidney disease and nephrolithiasis be managed without surgery.
Objective—To determine whether breed, age, sex, or
reproductive status (ie, neutered versus sexually
intact) was associated with the apparent increase in
prevalence of calcium oxalate (CaOx) uroliths and the
decrease in prevalence of magnesium ammonium
phosphate (MAP) uroliths in cats over time.
Animals—Case cats consisted of cats with CaOx (n
= 7,895) or MAP (7,334) uroliths evaluated at the
Minnesota Urolith Center between 1981 and 1997.
Control cats consisted of cats without urinary tract
disease admitted to veterinary teaching hospitals in
the United States and Canada during the same period
Procedure—Univariate and multivariate logistic
regression were performed.
Results—British Shorthair, Exotic Shorthair, Foreign
Shorthair, Havana Brown, Himalayan, Persian,
Ragdoll, and Scottish Fold cats had an increased risk
of developing CaOx uroliths, as did male cats and
neutered cats. Chartreux, domestic shorthair, Foreign
Shorthair, Himalayan, Oriental Shorthair, and Ragdoll
cats had an increased risk of developing MAP
uroliths, as did female cats and neutered cats. Cats
with CaOx uroliths were significantly older than cats
with MAP uroliths.
Conclusions and Clinical Relevance—Results suggest
that changes in breed, age, sex, or reproductive
status did not contribute to the apparent reciprocal
relationship between prevalences of CaOx and MAP
uroliths in cats during a 17-year period. However, cats
of particular breeds, ages, sex, and reproductive status
had an increased risk of developing CaOx and
MAP uroliths. (J Am Vet Med Assoc 2000;217:520–525)
Objective—To determine frequency of and interval until recurrence after initial ammonium urate, calcium oxalate, and struvite uroliths in cats and whether breed, age, or sex was associated with increased risk for urolith recurrence.
Animals—4,435 cats with recurrent uroliths.
Procedures—To identify recurrence of uroliths in cats for which uroliths were submitted for analysis at the Minnesota Urolith Center in 1998, the facility's database was searched for urolith resubmissions from the same cats between 1998 and 2003. Risk factors and differences in mean interval until recurrence were assessed.
Results—Of 221 cats with ammonium urate uroliths in 1998, 29 (13.1%) had a first and 9 (4.1%) had a second recurrence. Mean interval until recurrence was 22 and 43 months for the first and second recurrence, respectively. Of 2,393 cats with calcium oxalate uroliths in 1998, 169 (7.1%) had a first, 15 (0.6%) had a second, and 2 (0.1%) had a third recurrence. Mean interval until recurrence was 25, 38, and 48 months for the first, second, and third recurrence, respectively. Of 1,821 cats with struvite uroliths in 1998, 49 (2.7%) had a first and 3 (0.2%) had a second recurrence. Mean interval until recurrence was 29 months for first and 40 months for second recurrences.
Conclusions and Clinical Relevance—These results provided insights into the frequency of urolith recurrence in cats. Because some uroliths associated with recurrent episodes probably were not submitted to our facility, our data likely represented an underestimation of the actual recurrence rate.
Objective—To determine whether high systolic blood
pressure (SBP) at the time of initial diagnosis of
chronic renal failure in dogs was associated with
increased risk of uremic crisis, risk of dying, or rate of
decline in renal function.
Design—Prospective cohort study.
Animals—45 dogs with spontaneous chronic renal
Procedure—Dogs were assigned to 1 of 3 groups on
the basis of initial SBP (high, intermediate, low);
Kaplan-Meier and Cox proportional hazards methods
were used to estimate the association between SBP
and development of a uremic crisis and death. The
reciprocal of serum creatinine concentration was
used as an estimate of renal function.
Results—Dogs in the high SBP group were more
likely to develop a uremic crisis and to die than were
dogs in the other groups, and the risks of developing
a uremic crisis and of dying increased significantly as
SBP increased. A greater decrease in renal function
was observed in dogs in the high SBP group.
Retinopathy and hypertensive encephalopathy were
detected in 3 of 14 dogs with SBP ≥ 180 mm Hg.
Systolic blood pressure remained high in 10 of 11
dogs treated with antihypertensive drugs.
Conclusions and Clinical Relevance—Results suggested
that initial high SBP in dogs with chronic renal
failure was associated with increased risk of developing
a uremic crisis and of dying. Further studies are
required to determine whether there is a cause-and-effect
relationship between high SBP and progressive
renal injury and to identify the risks and benefits of
antihypertensive drug treatment. (J Am Vet Med Assoc 2003;222:322–329)