Ureteral Interventions: A Minimally Invasive Approach to Diagnosis & Treatment of Ureteral Disease
Ureteral disease can create a significant dilemma as one considers various approaches to both diagnosis and treatment. Interventional radiologic (IR) and interventional endoscopic (IE) techniques have aided tremendously in the ability to simultaneously diagnosis, and potentially treat, ureteral disease in a minimally invasive manner. Interventional radiology is a contemporary imaging modality that utilizes fluoroscopy, with or without ultrasound, in order to access various parts of the body with guidewires and catheters (i.e., blood vessels, GI tract, respiratory tract, biliary tract, urinary tract, etc). Interventional endoscopy involves the use of flexible and rigid endoscopes, in conjunction with fluoroscopy, for luminal visualization, access, diagnosis and treatment.1,2 We will focus on the application of both IR and IE to help face ureteral disease.
Currently, an expanding investigation of the use of some novel minimally invasive techniques in veterinary medicine has been undertaken, and we will discuss the use of both IR and IE in the diagnosis and treatment of various ureteral diseases in dogs and cats.1-3,4 The relatively common incidence of ureteral disease, combined with the invasiveness and morbidity associated with traditional surgical techniques, makes the use of minimally invasive alternatives appealing. The endourologic procedures we will discuss are considered standard of care in human medicine and they are currently being investigated and applied in veterinary medicine.
This talk will be a brief overview of various ureteral interventions actively under investigation in veterinary patients like ureteral stenting (for stone disease, trauma, stricture/stenosis or neoplasia), ureteroscopy (for ureteral stones, idiopathic renal hematuria, evaluation of hydroureter, etc), lithotripsy for ureterolithiasis, retrograde ureteropyelography for evaluation of ureteral lesions, percutaneous nephrostomy tube placement for immediate relief of ureteral obstructions, and cystoscopic-guided laser ablation of ectopic ureters (CLA).
Human Ureteral Intervention
In human urology the development and improvements in ureteroscopy, ureteral stenting, extracorporeal shockwave lithotripsy (ESWL), laser lithotripsy, laparoscopy, and percutaneous nephroureterolithotomy (PCNUL) have almost eradicated the need for open ureteral surgery for stone disease, strictures, trauma and neoplasia.6-14 Currently, ureteroscopy is the first line evaluation of ureteral neoplasia, upper tract essential hematuria, ureteral calculi > 5mm, and evaluation for ureteral obstructions. Ureteroliths < 5 mm have a 98% chance of spontaneous passage with medical management alone. For larger stones, or those that do not pass spontaneously, ESWL is effective in 50-81% of cases, though most of the literature suggests this number is closer to 50-67%.8,15,16 Ureteroscopy has a near 100% success rate when Holmium: YAG laser lithotripsy is used. 6,7,15 PCNUL has been successful for large proximal impacted ureteral stones.9 Ureteral stenting was first introduced in 1967 for evaluation of human patients with malignant ureteral obstructions.11 They are still widely used to treat both benign and malignant obstructive disease and this is considered standard-of-care. There has been documented success in stent placement for distal malignant obstructions of >96% when placed in an antegrade manner when access is gained through the kidney, and only 50% when placed in a retrograde manner.11 Ureteral stenting for stone disease is typically done after ureteroscopy for post-scoping spasm and edema, and in children it has been routinely done prior to ureteroscopy to allow for passive ureteral dilation in anticipation of immediate ureteral bypass and spontaneous stone passage. Ureteral stent have also been shown to dramatically ease a future ureteroscopy in a small pediatric ureter.14
Flexible and rigid endoscopes are needed for endourologic ureteral procedures. Rigid cystoscopy is used for female (dog or cat) ureteral intervention. Ureteral access is capable in a retrograde fashion in most female patients via IR techniques. Rigid endoscope diameters range from 1.9 mm to 7.5 mm. Flexible ureteroscopes (7.5-8.2 french) are used for cystoscopic access in male dogs and is needed for ureteroscopy in both male and female dogs. Different types of intracorporeal lithotrites and lasers are available for our procedures including: Holmium:YAG, diode, ultrasonic, pneumatic, electrohydraulic, and Bugbee electrode cautery. These are used for stones disease, tumor ablation, ectopic ureteral ablation, or essential (idiopathic) renal hematuria lesion coagulation. In addition, extracorporeal shock wave lithotripsy (ESWL) has great application for small to moderate ureteroliths in both dogs and cats.
A traditional fluoroscopic C-arm is sufficient for visualization and ureteral intervention. A mobile C-arm has the ability to move the image intensifier and gain various tangential viewing of the renal pelvis and ureter. Ultrasonography is useful for percutaneous renal access in order to cannulate the ureter from in an antegrade manner or for the placement of a percutaneous nephrostomy tube. This can also be done under direct fluoroscopic visualization. Various guidewires and catheters are also needed for each procedure. Ureteral stents in numerous shapes and sizes (double pigtail, locking loop pigtail, or nephroureteral stents) are soft polyurethane catheters that can be easily removed after resolution of ureteral disease.
Ureteral stenting has been performed for a variety of disorders in both dogs and cats.5,17 This procedure has been performed successfully in over 20 cases at the University of Pennsylvania to date (14 dogs and 7 cats). The goal of ureteral stenting is to divert urine from the renal pelvis into the urinary bladder or to encourage passive ureteral dilation (for ureteral stenosis/strictures or future ureteroscopy). There are 3 main types of ureteral stents: an indwelling double pigtailed ureteral stent, which is the most common type used in veterinary and human medicine, a nephroureteral stent, and a locking-loop pigtailed catheter. The double pigtailed stent is completely intracorporeal, and can remain in place for numerous months if necessary (recommended for < 6 months).
Ureteral stents are used to bypass obstructions from ureterolithiasis, malignant obstructive neoplasia, and ureteral stenosis. After interventional procedures (ureteroscopy, ureteral balloon dilation, retrograde ureteral lithotripsy or percutaneous nephroureterolithotomy), a ureteral stent is placed to prevent temporary obstructions from ureteral edema or spasm. Following surgical ureterotomy, ureteral resection and anastomosis, or ureteral tears, a ureteral stent may allow for tension relief and healing, preventing post-operative ureteral leaking. Ureteral stenting is also ideal in patients with large (> 5 mm) nephroliths or ureteroliths that are undergoing ESWL to aid in ureteral localization and fragment passage following the treatment.8,12 Ureteral stenting has been shown to allow passive ureteral dilation in humans over 2-4 weeks to permit passage of a ureteroscope or spontaneous stone passage of obstructive ureteroliths.12,14 This theory is still under investigation in our veterinary patients.
Under general anesthesia, via cystoscopy and concurrent fluoroscopy, an angle-tipped hydrophilic guidewire (Weasel® wire, Infiniti Medical) is advanced retrograde into the ureterovescular junction, up the distal ureter and curled into the renal pelvis. A ureteral catheter is then advanced over the wire under fluoroscopic guidance, and the guidewire is removed. A retrograde contrast ureteropyelogram is performed to help identify an lesions, stones, or filling defects in the ureter or renal pelvis. The wire is re-advanced through the catheter into the renal pelvis and the catheter is withdrawn. An indwelling ureteral stent, or an exteriorized pigtail catheter, is placed over the guidewire under fluoroscopic guidance with one curl remaining in the renal pelvis in front of the obstruction and the other in the urinary bladder. The antegrade technique requires percutaneous renal access with a renal access needle. This can be done with either ultrasound or fluoroscopy. The guidewire is passed down the ureter, into the urinary bladder and out the urethra to have through-and-through access ("flossed"). This is the typical approach for a trigonal induced malignant ureteral obstruction when the ureteral orifice can not be identified cystoscopically or for small male dogs and male cats where cystoscopy for retrograde ureteral access is not possible. The stent is then placed in a retrograde fashion over the wire, as described above.
Retrograde ureteropyelography allows for a irrigation of contrast under fluoroscopic guidance in order to image ureteral patency, space occupying lesions, stone disease, tortuosity of the ureter and ureter diameter. This is seemingly more accurate than intravenous pyelography (IVP) since ureteral distension is not possible without mild pressure irrigation in the ureter. This procedure is also less invasive than antegrade pyelography, eliminating the need for renal needle access and the risk of subsequent urinary leakage through the renal parenchyma if a ureteral obstructive lesion persists. By injecting contrast up the ureter form the ureteral orifice via cystoscopy and fluoroscopy, subtle lesions and filling defects can be evaluated closely and repetitively without extravasation of contrast around in the retroperitoneal space (i.e., antegrade pyelography), and under mild to moderate pressure to allow ureteral distension. It also prevents any risk of contrast induced nephropathy, since the contrast agent remains in the renal collection system and is not injected intravascularly.
Ureteroscopy is possible in dogs larger than approximately 20 kg. This procedure is difficult to perform in dogs though a normal ureteral orifice, as the ureter in a normal dog is less than 2 mm and the smallest ureteroscope is approximately 2.5 mm. Ureteral access is obtained via cystoscopy, as described above with a guidewire being advanced into the renal pelvis. The ureteral orifice is then dilated with a ureteral dilator to 8-10 fr or a dual lumen (10 fr) ureteral catheter, allowing a retrograde ureteropyelogram prior to ureteroscopy, as well as the placement of a 2nd safety wire that can remain in place next to the ureteroscope. The flexible ureteroscope is than advanced over the guidewire into the ureter under fluoroscopic and endoscopic guidance. This procedure is ideally performed for evaluation of the ureteral and renal pelvic mucosa in the case of idiopathic renal hematuria, for ureteral stone disease and laser lithotripsy if ESWL is not effective, or for evaluation of ureteral obstruction and hydroureter when other imaging modalities are not diagnostic (ureteral stricture/stenosis or neoplasia).
Ureteroscopy can also be performed in an antegrade manner via renal access.1,18 A renal access needle (18 g) is advanced into the renal pelvis through the renal parenchyma under ultrasound or fluoroscopic guidance for a pyelocentesis and pyeloureterogram. A guidewire is advanced through the needle, down the ureter, into the urinary bladder, and out the urethra, as described above. A renal balloon dilator is then advanced over the wire, pre-loaded with an access sheath that is large enough to fit the nephroscope (18 fr) or ureteroscope (10 fr). The balloon is inflated through the renal parenchyma and the sheath is then advanced over the balloon for a smooth transition into the renal pelvis. The balloon is deflated and removed over the wire, and a second safety wire is advanced down the ureter through the sheath. The endoscope is then advanced over the wire, down the ureter and ureteroscopic evaluation can be performed. If a stone is present a stone basket can be used to remove the stone through the access sheath, or broken with the laser lithotrite.
Extracorporeal Shockwave Lithotripsy (ESWL) for Ureterolithiasis
Extracorporeal shock-wave lithotripsy is another minimally invasive alternative for the removal of ureteral calculi.19,20 ESWL delivers external shockwaves through a water medium directed under fluoroscopic guidance in 2 planes. The stone is shocked anywhere from 1000-3500 times at different energy levels to allow for implosion and powdering. The debris is then left to pass down the ureter into the urinary bladder over a 1-2 week period. This procedure can be performed safely for ureteroliths smaller than 5 mm in dogs and 3-5 mm in cats. For larger stone burdens an indwelling double pigtailed ureteral stent is placed prior to ESWL to aid in stone debris passage, ureteral imaging, and immediate relief of the ureteral obstruction prior to ESWL treatment. For stones of larger sizes, or those imbedded in the ureteral muosa, PCNUL or ureteroscopy may be necessary.
Percutaneous Nephrostomy Tube Placement
Ureteral obstructions secondary to ureteroliths or malignancy can result in severe hydronephrosis and/or life-threatening azotemia when presenting bilaterally or in animals with concurrent renal insufficiency/failure. Some patients can be managed medially with supportive care until a ureterolith passes, others may require surgery to avoid permanent damage and/or hemodialysis for stabilization prior to a prolonged anesthesia for ureteral surgery. Ureterotomies can be relatively prolonged and complicated surgeries in these debilitated patients with an unclear outcome of residual renal function.21 One possibility is to place a nephrostomy tube percutaneously to quickly relieve the obstruction1-3 and determine whether adequate renal function remains before prolonged anesthesia for ureteral surgery or ureteral stent placement. This procedure is done under ultrasound guidance, where a renal access needle is used for pyelocentesis and a ureteropyelogram. Then a guidewire is passed through the needle under fluoroscopic guidance, and coiled into the dilated renal pelvis. The pelvis should be larger than 1 cm to allow the pigtail to curl easily in the renal pelvis. The locking loop pigtailed cateter is then advanced over the guidewire into the renal pelvis and the curl is formed. Once the curl is in the renal pelvis is made the pigtail is locked and the catheter is secured to the body wall for tract formation. The catheter is securely sutured to the skin by a Chinese finger trap suture pattern. This should remain in place for 2-3 weeks for tract formation, or the hole can be closed surgically if a ureterotomy is subsequently performed. This allows for external renal drainage to asses azotemia resolution and patient stabilization prior to a more permanent fixation of the ureteral obstruction (ureterotomy, ureteral reimplantation or ureteral stent placement). During nephrostomy tube placement the guidewire maybe be able to be advanced down the ureter, and if it by-passes the obstruction, and through and through access is obtained, a ureteral stent can be attempted.
Cystoscopic-Guided Laser Ablation of Ectopic Ureters (CLA)
Ectopic ureters are a common congenital anatomic deformity in dogs with the ureteral orifice being positioned distal to the bladder trigone within the ureter, vagina, vestibule or uterus. Over 95% of dogs with ectopic ureters transverse intramurally and are candidates for this minimally invasive procedure. This is done with the use of fluoroscopy, cystoscopy and a diode or holmium:YAG laser. This procedure is performed on an out-patient basis at the time of cystoscopic diagnosis, avoiding the need for more than one anesthetic procedure for fixation. Overall, surgical fixation of ectopic ureters reports results of continued incontinence with concurrent medical intervention in anywhere from 40-71% of cases due to concurrent sphincter mechanism incompetence of the urethra (SMI). Thus far, in our experience, continence has been maintained in over 80% of patients, though more cases are needed with longer follow-up to accurately compare this procedure to surgery.3,4 This procedure is successful in both male and female dogs with ureteral ectopia, avoiding laparotomy, cystotomy, urethrotomy and ureterotomy.
The ureter is a frustrating area to gain access to for both diagnosis and treatment of disease. With the recent advances in veterinary interventional endourologic technique1,3-7 diagnosis and treatment has become less invasive and often simultaneous. Proper training and the availability of specialized equipment is needed to help these procedures become more available in the future. With these new minimally invasive modalities in veterinary medicine, we are hoping to find better alternatives for these problematic conditions, as we have seen in our human counterparts.
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