Congenital Diseases of the Urinary Tract
Congenital diseases (present at birth) may be genetically determined
(inherited) or result from exposure to adverse environmental factors during
development.
Renal aplasia
is complete lack of development of one or both kidneys. If bilateral, it
results in neonatal death. If unilateral, the opposite kidney is
hypertrophied and no clinical signs will be present unless the opposite
kidney is damaged. Renal aplasia is more commonly recognized in the cat. It
may be inherited in beagles.
Polycystic disease
results in multiple cysts of varying size in one or both kidneys.
Compression of renal parenchyma by enlarging cysts causes renal dysfunction.
Bilateral involvement may lead to CRF at a young age if a large percent of
renal parenchyma is replaced with cysts. A heritable form of polycystic
kidney disease (PKD) exists in Persian cats.
Clinical signs and
laboratory findings are similar to those of chronic renal failure of any
cause. Hematuria may be an early sign in some cats. Some Persian cats with
PKD also have liver cysts. PKD can occur in both young and old cats. It
appears to be transmitted as an autosomal dominant trait in Persian cats.
The cysts range in size from 1mm to > 1cm and will cause kidney enlargement
if large and numerous. The cysts typically contain clear or straw colored
fluid but can contain blood or purulent exudate.
A diagnosis can be made using excretory urography or less invasively
using ultrasound. Ultrasound may detect cysts as small as 2 mm. There is no
treatment for PKD other than
symptomatic treatment for CRD.
Owners should be counseled that this is a heritable disease.
1.
Polycystic Kidney
Disease in cats by Dr. David S. Biller, Kansas State University,
and Marie Thiers, S*Sequoyahs Persians, Sweden
Familial juvenile renal disease
occurs in related animals suggesting an inherited disease. Signs of juvenile
renal disease may be present at birth or deterioration may occur during the
first few years of life. The onset of signs can be as late as 5 years of
age. There are some commonly recognized laboratory findings in each breed
(e.g. glucosuria or proteinuria). The histologic appearance of the kidney
varies with the breed. The mode of inheritance and specific pathogenesis is
unknown in most breeds. Familial juvenile renal disease is generally
progressive with a poor long term prognosis, although some animals live for
several years.
Some of the specific syndromes include:
- Primary renal glucosuria which is a renal tubular enzymatic defect
in active glucose reabsorption. Patients may be asymptomatic or may be
polyuric/polydipsic due to the osmotic effect of glucose in the urine.
They are predisposed to development of urinary tract infection due to
the presence of glucose in the urine. Primary renal glucosuria must be
differentiated from diabetes mellitus based on a normal blood glucose
value. Breeds predisposed to develop primary renal glucosuria are the
Norwegian elkhound, Scottish terrier, and mixed breed dogs.
- Fanconi syndrome is a constellation of abnormalities associated with
proximal tubular defects in reabsorption. The consequences include loss
of water, glucose, phosphate, sodium, potassium, amino acids, and other
substances that are normally reabsorbed. Fanconi syndrome occurs most
commonly in Basenjis but also occurs in other breeds. Fanconi syndrome
is inherited but signs are often not recognized until middle age.
Clinical signs include polyuria, polydipsia and glucosuria initially
with metabolic acidosis and progression to renal failure leading to
death occurring later. Progression occurs over months to years.
See Textbook of Veterinary Internal Medicine for a table of reported
familial renal diseases in dogs and cats.
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1.
North
Carolina State University research page on protein-losing
enteropathy and/or protein-losing nephropathy in related soft-coated wheaten
terriers.
2.
Juvenile Renal Disease and Juvenile Renal Disease in Standard
Poodles by Susan L Fleisher are written by a lay person but are well
referenced.
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Ectopic ureters
are a congenital defect in which the ureters empty urine into another
location, other than the bladder. Unilateral ectopia is more common than
bilateral, ~25% of cases are bilateral. Ectopic ureters occur more
commonly in females. There is a familial tendency for ectopic ureters in
Siberian Huskies and Black Labradors. There are a few reported cases in
cats, usually in the male. In female dogs, one or both ureters terminate in
the vagina (most common), urethra or uterus. In male dogs, the ureter(s)
terminate in the urethra.
Ectopic ureters are often associated with other congenital anomalies or
associated diseases such as mega-ureter due to urine reflux, decreased
kidney size, congenital hypoplasia, chronic pyelonephritis, decreased
bladder size, either congenital or from disuse if ectopia is bilateral.
Clinical signs include urinary incontinence present from birth. Some males
with ectopic ureter(s) may be continent because of the longer length of the
male urethra. Animals can void normally if only one ureter is ectopic.
Ectopic ureters can be diagnosed by endoscopy to visualize the ureteral
opening into the vagina or by a radiographic contrast studies, an
intravenous pyelogram. The study may be hard to interpret if the ureters
tunnel through bladder wall before terminating in an ectopic site. Vaginal
contrast studies can also be performed by infusing contrast agent into the
vagina in an attempt to retrograde the contrast into an ectopic ureter.
The associated infection should be treated prior to surgical
transplantation of the ureter. A nephrectomy may be necessary if the kidney
attached to ectopic ureter has an intractable infection. Incontinence may
persist postoperatively if other defects are present.
Other congenital
diseases include:
- bladder agenesis (failure to form)
- bladder hypoplasia (small size and capacity)
- patent urachus
- urachal diverticulum which may predispose to recurrent urinary tract
infections
- predisposition to struvite calculi which is possibly familial in
miniature schnauzers
- cystinuria in dachshunds
Last Edited: May 05, 2008 5:01 PM
