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 . 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 . a 9-year male neutered domestic longhair cat was referred to the small animal soft tissue surgery department of our hospital for investigation of recurrent urinary tract obstruction . the clinical signs had started 12 months previously when a grass seed was incompletely removed from the urethra . subsequently , the cat had been catheterised on multiple occasions owing to recurrent urethral blockage . medical management ( dexamethasone , meloxicam and prazosin ) failed to alleviate the clinical signs , so referral was sought . upon arrival there were no reported changes to the home environment but the cat did not get on well with the other cats in the household . it was reported to be an outdoor cat during the day but was kept indoors at night , with no access to a litter tray . at that time , it was not on a urinary tract prescription diet . physical examination was unremarkable and , with the owner s consent , it was decided to perform a conscious abdominal ultrasound examination followed by a contrast retrograde urethrocystogram study under general anaesthesia . blood and urine ( via ultrasound - guided cystocentesis ) were also taken for evaluation . the serum biochemistry was within normal limits showing normal electrolytes and normal renal parameters ( urea , creatinine , phosphate ) . a urine culture and sensitivity test demonstrated a heavy growth of escherichia coli , which was resistant to clavulanic amoxicillin but sensitive to marbofloxacin . abdominal ultrasound of the abdomen was performed using a philips hdi 5000 machine and a microconvex 58 mhz transducer . subjectively , normal kidneys and ureters , a distended urinary bladder with anechoic contents and a mildly dilated ( 3 mm in diameter ) proximal urethra that extended towards the pelvic rim were seen . no obvious reason for the dilation , such as an obstruction , was identified in the urethra cranial to the pelvic inlet . the cat was anaesthetised and examination of the penis revealed it to be prolapsed and extremely erythematous and friable ( figure 1 ) . the cat received epidural morphine at 0.1 mg / kg ( morphine sulphate ; martindale ) and bupivacaine 1 mg / kg ( marcain ; astrazeneca ) , whereupon a urinary catheter was placed . catheterisation of the distal urethra was challenging but a 3 f urinary catheter with end hole ( 1.3 mm  11.0 cm slippery sam tomcat ; surgivet ) was eventually inserted into the distal tip of the penis . a retrograde contrast urethrocystogram was performed by instilling 4 ml ionised contrast medium ( 61.2% w / v iopamidol equivalent to 300 mg iodine / ml [ niopam300 ; bracco ] ) diluted 1:1 with sterile saline through the pre - placed urinary catheter into the distal urethra and then occluding the penile opening . iopamidol is a non - ionic contrast medium that results in a low osmolality when compared with ionic media . radiographs were taken prior to administration and at predetermined times ( immediately , 2 mins and 10 mins ) after instillation of contrast medium into the urethra . examination of the penis under sedation revealed it to be prolapsed and extremely erythematous and friable ( reproduced by kind permission of kelly bowlt ) plain radiographs of the abdomen showed good peritoneal serosal detail , a normal shape and size of both kidneys , a moderately distended urinary bladder and a small amount of formed faeces within the descending colon . a contrast retrograde urethrocystogram ( figure 2 ) , taken immediately postadministration of contrast medium , showed an area of extravasation of the contrast medium that could be seen cranioventrally to the distal urethra . a focal narrowing is visible in the mid - pelvic urethra at the level of the prostate gland , which is normal anatomy . the urinary bladder and urethra appeared subjectively normal in shape and were filling appropriately with contrast medium , without any evidence of calculi . an area of extravasation of the contrast medium can be seen cranioventrally to the distal urethra ( white arrow ) . a focal narrowing is visible in the mid - pelvic urethra at the level of the prostate gland ( black arrow ) , which is normal anatomy . the urinary bladder is normal in shape and filling appropriately with contrast medium two minutes later a second contrast retrograde urethrocystogram was acquired ( figure 3 ) , which showed that the contrast medium had extravasated from the urethra . dramatically , the contrast could now be seen within the vasculature and is highlighting the penile veins the internal and external pudendal veins , which drain into , respectively , the internal iliac and external iliac veins and , ultimately , the caudal vena cava . the internal ( dorsally ) and external ( ventrally ) pudendal veins drain blood from the penis . the internal pudendal joins the internal iliac vein , and the external pudendal drains into the external iliac . the iliac veins on each side unite to form the common iliac vein , and the two common iliac veins then converge into the caudal vena cava . a = dorsal penile vein ; b = scrotal vein ; c = internal pudendal vein ; d = external pudendal vein ; e = branch of the femoral vein ; f = internal iliac vein ; g = external vein ; h = caudal vena cava at 10 mins post - contrast injection , a third radiograph was taken ( figure 4 ) , which showed contrast medium within the renal pelves ( renal excretion ) , indicating that the contrast uptake had , indeed , been within the vasculature . contrast medium is present within the renal pelves ( black arrow ) demonstrating renal excretion and indicating that the contrast uptake had been within the vasculature retrograde urethrocystoscopy revealed stenosis and irregularities of the caudal urethral mucosa consistent with strictures . further to discussion with the owners , it was decided to perform surgery to remove the damaged penis to create a larger opening through which urine could pass . a routine perineal urethrostomy was performed using a previously described technique ( figure 5 ) . the resulting stoma was large enough to accommodate a pair of needle holders up to the box lock . a perineal urethrostomy was performed using a previously described technique ( tobias ) ( reproduced by kind permission of kelly bowlt ) the cat recovered well from the anaesthetic . immediately after the anaesthetic , it underwent pain checks every 2 h for 8 h. during the following 3 days in hospital the cat was maintained on buprenorphine 20 g / kg intramuscularly q6h ( vetergesic ; alstoe ) , marbofloxacin 10 mg orally ( po ) q24h ( marbocyl ; vetoquinol ) , meloxicam 0.05 mg / kg po q24h ( metacam ; boehringer ingelheim ) , cystophan 1 capsule po q12h ( cystophan ; protexin ) and prazosin 0.5 mg po q12h ( hypovase ; pfizer ) . the cat did not urinate the first or second day after surgery , and a urinary catheter ( 3 f 1.3 mm  11.0 cm slippery sam tomcat ) was passed easily into the urinary bladder once daily on both days . a repeat ultrasound of the urinary bladder and proximal urethra was unremarkable . on the third day in hospital the cat urinated and defecated in its litter tray without assistance , and was subsequently discharged . at discharge several dietary / environmental changes were suggested , including provision of a prescription urinary tract diet , a drinking fountain , a litter tray for overnight use and a pheromone diffuser ( feliway ; ceva ) . a follow - up appointment was recommended with the referring vet , at which time healing was progressing normally . the cat has since recovered completely and , at the time of publication , had not displayed any symptoms of urinary tract disease . the retrograde contrast study demonstrated that this cat had a patent urethra and urinary bladder . however , the extravasation of contrast material from the urethra established that there was at least partial leakage or a tear of the urethra . although extravasation of contrast medium is frequently seen in urethral tears , it usually dissipates into the surrounding periurethral tissues . in this case , the extravasated contrast was almost immediately absorbed by the systemic circulation , suggesting an abnormal and increased blood supply of the distal urethra and penis . the rapid vascular uptake of the extravasated contrast , as seen in this case , has , to our knowledge , not been described before . in the cat , the deep and dorsal penile veins these veins then merge with the internal pudendal vein dorsally and the external pudendal vein ventrally . the internal pudendal vein drains into the internal iliac vein , whereas the external pudendal vein drains into the external iliac vein . the internal and external iliac veins merge to form the short common iliac vein before terminating in the caudal vena cava ( see figure 3 ) . the increased vascularisation of the lower urinary tract in this case is likely the result of inflammation . whether the inflammation was secondary to chronic obstruction or repeated iatrogenic trauma , or a combination of these factors , however , the chronicity of the disease is supported by the presence of chronic changes in the form of urethral strictures and the friability and oedematous nature of the penis . from a clinical point of view , the increased vascularisation following ( chronic ) inflammation is important to recognise . it is well documented that traumatic catheterisation can cause urethral tears but perhaps some consideration of the effects of multiple non - traumatic catheterisations and the ensuing inevitable inflammation is warranted . in any case , due care must be taken in the selection of contrast media for potential retrograde studies . these principles also apply to any other medication that might be applied into the urethra . for example , multiple local anaesthetic agents are used in the urethra ; however , caution is necessary in the selection of an agent based on the potential for entry into the vasculature . equally , an absolute aseptic technique is essential considering the potential for contaminants to be resorbed quite rapidly into the systemic circulation . as demonstrated by this case , the potential complications of chronic lower urinary tract disease should not be underestimated . multiple catheterisations and chronic inflammation should be avoided , and alternative options should be considered when chronic disease is suspected .
case summarya 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 relevancerapid 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 .