Ureteral Obstruction is a critical medical emergency defined by the blockage of the ureter, the narrow tube that transports urine from the kidney to the bladder. This condition is most frequently caused by a ureterolith (kidney stone) composed of calcium oxalate that leaves the kidney and becomes lodged in the narrow duct. The blockage creates immediate back pressure known as hydronephrosis which causes the kidney to swell and halts filtration instantly. In CKD cats, this presents a unique diagnostic clue often referred to as "Big Kidney, Little Kidney" syndrome. On ultrasound, the obstructed kidney appears large and fluid-filled while the chronic CKD kidney appears small and shriveled. This obstruction is a common trigger for an Acute Kidney Injury crisis. Because the ureter is too small to pass these stones naturally, medical management often fails. Therefore, treatment frequently requires the surgical placement of a Subcutaneous Ureteral Bypass (SUB) device to create a new artificial path for urine flow.
Disclaimer: This content is for educational purposes only and does not constitute veterinary medical advice. Always consult with your primary care veterinarian or a veterinary internal medicine specialist regarding your cat’s specific condition.