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

2. CFA Health Committee Autosomal Dominant Polycystic Kidney Disease in Persian Cats by Dr. David S. Biller, Kansas State University, et al.

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