Rapid vascular uptake of contrast during a retrograde urethro-cystogram in a cat with chronic lower urinary tract disease

Case summary A 9-year male neutered domestic longhair cat was referred to our hospital for investigation of recurrent urinary tract obstruction. The clinical signs had started 12 months earlier and the cat had been catheterised on multiple occasions. Clinical examination and abdominal ultrasound of the abdomen was unremarkable but examination of the penis revealed it to be prolapsed and extremely erythematous and friable. A retrograde contrast urethrocystogram was performed, showing extravasation of the contrast medium and establishing the presence of partial leakage or a tear of the urethra. In subsequent radiographs, the contrast was seen being rapidly absorbed into the pelvic and systemic vasculature via the penile veins, internal and external pudendal veins, internal and external iliac veins, and, ultimately, the caudal vena cava. Later, the contrast medium was seen within the renal pelves. Retrograde urethrocystography revealed stenosis and irregularities of the caudal urethral mucosa consistent with strictures. A routine perineal urethrostomy was performed and the cat recovered well. Conclusions and relevance Rapid vascular absorption of extravasated contrast medium has not been reported before. In this case, the increased blood supply to the distal urethra and penis is likely secondary to (chronic) inflammation, as demonstrated by the urethral strictures and the friable, oedematous nature of the penis. Whether the inflammation was caused by chronic obstruction or repeated iatrogenic trauma, or a combination of these factors, will remain debatable. Nonetheless, this case demonstrates that when a retrograde contrast urethrocystogram is considered, it is imperative that a contrast medium (or other intraurethral medication such as local anaesthesia) is chosen that is safe for intravascular use. Equally, an absolute aseptic technique is essential considering the potential for contaminants to be absorbed quite rapidly into the systemic circulation. Multiple catheterisations should be avoided when there is chronic inflammation, and alternative options should be considered when chronic disease is suspected.