A ureteral bypass device and procedure suitable for performing internal urinary diversions within patients, including patients such as humans and veterinary animals (cats and dogs). The device includes a nephrostomy catheter having a proximal end, an oppositely-disposed distal end, and means for securing the distal end within the renal pelvis of a kidney of a patient, a cystostomy catheter having a proximal end, an oppositely-disposed distal end, and means for securing the distal end of the cystostomy catheter within the urinary bladder of the patient, and an adaptor fluidically connected to the proximal ends of the nephrostomy and cystostomy catheters so as to fluidically connect the nephrostomy and cystostomy catheters together through the adaptor. If implanted subcutaneously, the adaptor may include an entry site that has a self-sealing septum that can be accessed with a needle while the device remains implanted and secured under the skin to subcutaneous tissue.
