Interventional Radiology

Tracheal stents offer a palliative treatment for tracheal collapse when medical management options have been exhausted. In some cases, the tracheal collapse can be so severe that medical management will have limited positive impact and stenting quickly becomes the treatment of choice. Self-expanding intra-luminal stents are used with preference; the placement of such a stent involves the use of fluoroscopy and is minimally invasive. Amongst patients that have been appropriately selected for the procedure, significant clinical improvement is seen in 80-90% of cases.

Benign or malignant nasopharyngeal strictures can be managed with stricture dilation or stent placement if the stricture were to be refractory to other treatments.

Nephrostomy tubes are used as a temporary measure in cases of acute obstruction of the ureter by ureteroliths. This allows stabilisation of the patient including preventing further deterioration of renal function. Furthermore, permanent procedures that may be necessary to bypass the obstructioncan then be planned and undertaken as more of an elective procedure.

Subcutaneous ureteral bypass system (SUBS) is used in cases of ureteral obstruction by ureteroliths, strictures or neoplasia in cats and dogs. This technique surpasses the ureteral stent in many cases and particularly in cats and has a low complication rate. It involves placing a shunting port along the ventral abdominal wall and a connecting tube between the kidney of the affected side and the bladder.

Ureteral stents still have their place, particularly in larger patients, where these can be placed in a retrograde manner, through the use of cystoscopy and fluoroscopy, to bypass the obstruction thereby avoiding surgery. In some cases, it is more appropriate to undertake an anterograde approach from the kidney to the bladder to bypass a ureteral obstruction, thereby allowing renal function to be preserved.

Urethral stents alleviate dysuria and stranguria in dogs and cats with various conditions such as neoplasia of the bladder neck or prostatic tumours, granulomatous urethritis, urethral stricture, reflex dyssynergia and extrinsic urethral compression. In many cases, the stent offers only a palliative solution however, with significantly less complication than alternative surgical options such as cystostomy tubes. In cases of strictures, balloon dilation can also be performed under fluoroscopic guidance.

Balloon dilation is considered the first line approach in cases of oesophageal and colonic strictures in dogs and cats. Stenting of strictures, typically with biodegradable stents, is considered in patients with strictures that are refractory to balloon dilation or in some cases stenting is considered earlier in the treatment phase to prevent multiple repeated dilations and general anaesthetics.

Intravascular procedures (pin hole surgery) have also been adapted from human to veterinary patients. These techniques involve the use of wires and catheters within a blood vessel to access areas that are difficult to reach surgically. Stents can be placed to occlude or improve blood flow.

• Coil embolisation of intrahepatic portosystemic shunts involve placing numerous coils in the shunting vessel to occlude the blood flow through this vessel.
• Chemo-emobilisation of nasal tumours can also be performed in appropriate cases.
• Chemo-embolisation of large non-resectable liver tumours (hepatocellular carcinomas) can be performed to provide drugs directly to the tumour and then block the blood supply to theliver. Chemo-embolisation of nasal tumours can also be performed in appropriate cases.
• Embolisation can be used in cases of refractory epistaxis by placing embolic agents in nasal blood vessels to stop the haemorrhage.

Laparoscopy and thoracoscopy (keyhole surgery) is a minimally invasive surgical technique which can be used to perform certain procedures such as taking biopsies of liver, pancreas, or lymph nodes, performing cryptorchid castration and ovariectomy in the abdomen and partial lung lobectomy or pericardectomy in the thorax. Many other procedures are possible however, cases are assessed on an individual basis to determine suitability.