Urinalysis should be performed in any dog presenting for urinary incontinence to rule out a urinary tract infection. Routine haematology and serum biochemistry should be performed to rule out metabolic conditions which may be causing polyuria/polydypsia.
Definitive diagnostic testing involves an excretory urogram using either flat-film radiographs or computed tomography, with computed tomography being more sensitive. Iohexal (240 mg/ml) is used at a dose of 2-3 mls/Kg. If there is evidence of renal insufficiency, a reduced dose of 0.5 – 1.0 mls/Kg is used. Scans or radiographs are performed at regular intervals after injection of the contrast at time zero, 1 minute, 5 minutes, 10 minutes and 20 minutes.
If flat-film radiographs are being used, the patient should be fasted for 36 hours prior to the procedure to ensure that the bowels are evacuated and lateral and ventrodorsal views should be taken. If computed tomography is being used, these issues are not relevant.
The appearance and position of the ureteral openings are assessed noting that up to 70% of ectopic ureters can be bilateral. Many patients will have hydroureter or hydronephrosis of the affected side. Other conditions may also be present including ureterocoeles and bladder hypoplasia. The function of each kidney should be noted because a severely abnormal kidney with hydronephrosis and hydroureter may need to be removed rather than repositioning the ureteral opening.
Primary urethral sphincter incompetence can be present in about 50% of patients with ectopic ureters, so urethral pressure profilometry can be performed to assess the likelihood of success of repair of the ectopic ureter.
Cystourethroscopy is also very helpful on making a diagnosis. The ureteral opening can often be seen in its abnormal position.