Ureteral stenting is performed for a variety of disorders to divert urine from the renal pelvis into the urinary bladder. This technique can be useful in patients with ureteral obstruction due to ureteral stones, ureteral or trigonal obstructive cancer, following ureteroscopy (endoscopy of the ureter), for post-operative ureteral anastomosis, ureteral tears, ureteral spasm, or ureteral inflammation. In addition, the presence of the ureteral stent may result in subsequent passive ureteral dilation to permit passage of previously obstructive stones, or allow passage of the flexible ureteroscope for appropriate ureteral intervention. This technique has been performed in over 100 dogs and cats, and is currently routinely performed for ureterolith-induced obstructions. Ureteral stenting is also ideal in patients with nephroliths or ureteroliths that are undergoing shockewave lithotripsy to aid in fragment passage following treatment. Stent placement in the ureter for bladder tumors causing obstruction is now being performed routinely as well.
“Jeanette” is a 12 year old female domestic shorthair presented for renal failure. On further evaluation it was found that she had stones up and down both ureters, and only one functioning kidney, which was obstructed with over 30 stones. Routine surgery was not a good option for Jeanette so her stones were addressed by placing a ureteral stent. With an endoscope through her urethra and into the bladder the stent was able to be placed into her kidney, bypassing her stones and decompressing her obstruction.
An 8 year old male Beagle named “Ben” presented for ureteral obstruction secondary to cancer in his bladder, called transitional cell carcinoma. “Ben” had a dilated kidney and ureter due to this obstruction and a minimally invasive procedure allowed us to use ultrasound and fluoroscopy to place a double pigtail stent in his ureter to bypass the obstruction. “Ben” returned home within 8 hours after the procedure and lived another 10 months, never going into renal failure.
Percutaneous antegrade placement of ureteral stent to relieve malignant ureteral obstruction secondary to transitional cell carcinoma in a dog. (A) Percutaneous pyelocentesis with an 18 gauge catheter and contrast ureteropyelogram demonstrating hydronephrosis (*) and hydroureter (white arrows). A marker catheter (black arrows) has been placed in the colon for stent sizing. (B) Fluoroscopic-guided antegrade passage of an angled hydrophilic guidewire and catheter (white arrows) across the obstruction and out the penis. (C) Retrograde ureteral dilation with a 6Fr ureteral dilator placed over-the-wire (white arrows). (D) Indwelling multifenestrated 4.7Fr x 12cm ureteral stent (white arrows) passed retrograde over the guidewire spanning the urinary bladder (UB) to the renal pelvis (white asterisk) for urinary decompression.
Kidney stones or proximal ureteral obstructions secondary to ureteroliths can result in progressive renal failure, intractable infections, ureteral pain, and bleeding. If the stone is small enough it may pass, however others require surgery to relieve the obstruction or avoid permanent nephron damage. The surgeries to fix this can be prolonged, invasive, and complicated, potentially resulting in significant morbidity. In people, percutaneous nephrolithotomy is considered the standard-of-care for kidney stones too large to be treated with shockwave lithotripsy or retrograde ureteroscopy with laser lithotripsy, and has recently been performed successfully in clinical veterinary cases. This minimally invasive procedure aims to minimize morbidity, and preserve as much renal function as possible.
“Sasha” is a 10 year old female Yorkshire terrier who had a very large kidney stone that was causing a worsening to her renal failure. Sasha’s owner decided that she did not want to risk surgery to cut her kidney open and potentially make her kidney failure worse, so a PCNL was instead performed using fluoroscopy and endoscopy to remove the stone through a very small hole.
Percutaneous nephrolithotomy in a dog with large nephrolith. (A) Following percutaneous, ultrasound-guided renal access, two guidewires (white arrows) are advanced down the ureter, into the bladder, and out of the urethra for through-and-through access. A large sheath (black arrow) is placed over the wire to gain access to the renal pelvis and nephroliths (*). (B) Using endoscopic visualization, the lithotripter (white arrow) is used to fragment and remove the nephrolith. (C) Post-procedure fluoroscopic image demonstrating complete removal of the nephrolith. (D) Nephro-ureteral stent (white arrows) placement following lithotripsy.
Extracorporeal shock-wave lithotripsy (ESWL) is another minimally invasive alternative for the removal of upper tract calculi in the renal pelvis, or ureters. ESWL uses external shockwaves that is passes through a water medium directed under fluoroscopic guidance in 2 planes. The stone is shocked at different energy levels to allow for implosion and powdering of a stone. 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 in nephroliths smaller than 5 mm, and ureteroliths smaller than 3 mm. In larger stone burdens an indwelling double pigtail ureteral stent is placed prior to ESWL to aide in stone debris passage. For stones of larger sizes PCNL is recommended.
Case Example: “Meesha” is a 12 year old female Terrier who had very large kidney stones in both kidneys (Red oval on left-Figure 10). Due to the invasive nature of surgery it was elected to try shock-wave lithotripsy (ESWL) where no incision needs to be made. This requires the stones to break, and pass on their own down the ureter. Since they were so large we elected to place a ureteral stent (black arrows-Figure 10) prior to her therapy. Within 7 days her stone was gone and a second procedure was the performed on her other side.
Ectopic ureters are a common congenital problem in dogs with the ureteral orifice being positioned behind the bladder within the ureter, vagina, vestibule or uterus resulting in urinary incontinence. Over 95% of dogs with ectopic ureters transverse intramurally and are candidates for the minimally invasive procedure. Endoscopic repair of ectopic ureters has been performed in the authors’ practice in over 40 patients to date, with excellent success. 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 ectopic ureter diagnosis avoiding the need for more than one anesthetic procedure for fixation. Overall, traditional surgical fixation of ectopic ureters reports results of continence rates (with supplemental concurrent medical therapy) anywhere from 30-60% due to concurrent sphincter mechanism incompetence of the urethra (SMI). Thus far, in the our experience with the laser, continence has been maintained similarly or higher, without the need for any invasive surgery.
Case Example: “Madison” is a 2 year old female Shih-tzu who presented for incontinence since adoption. On cystoscopic evaluation she had her ureters opening in the wrong place (ectopic ureters). At the same time a laser was used to cut the tissue of one of the walls of her ureter, through the cystoscope, and the opening was then re-located to the urinary bladder, resulting in complete continence.
Idiopathic renal hematuria (Figure 12) is a rare condition in which a focal area of bleeding in the upper urinary tract results in long term hematuria, iron deficient anemia (chronically) and the potential for clot formation, or calculi due to blood clots, resulting in ureteral colic or signs of lower urinary tract disease. In people, the presence of a hemangioma or vascular malformations have been visualized ureteroscopically, which is cauterized through the working channel of a ureteroscope. This has also been performed in a small number of dogs to date.
Laser lithotripsy is an innovative technique involving the intracorporeal fragmentation of bladder and urethral stones (and rarely ureteral or kidney stones), which is assessed using a rigid or flexible cystoscope or ureteroscope. The stone is fragmented until the pieces are small enough to be removed normograde through the urethral orifice, either via voiding urohydropropulsion or with the assistance of a stone basket. This process is useful for ureteral, cystic and urethral calculi. All stone types are able to be fragmented using laser lithotripsy.
Other urologic applications for laser lithotripsy include incision of urethral and ureteral strictures; ablation of superficial transitional cell carcinoma/prostatic adenocarcinoma within the urethral lumen, laser ablation of urinary polyps. Bladder polyps are common findings in dogs and can be associated with chronic, recurrent urinary tract infections, cystolith formation, and are often misinterpreted for cystic neoplasia. Using cystoscopy and baskets or laser lithotripsy the polyps can be removed without surgical intervention by cauterizing the stalk.
Case Example: “Chester” is a 8 year old Bichon with a large calcium oxalate stone stuck in his urethra. He has had 4 surgeries in the past for removal. With cystoscopy and a laser we were able to break and remove this stone avoiding surgery. He went home only 6 hours later without any signs of discomfort.
Case Example: “Penny”, a 12 year old Doberman, had a large benign mass in her bladder, known as a polyp. This was growing and she was getting recurrent infections. Using endoscopy was was able to belasered off from the stalk for removal and analysis.
Malignant obstructions of the urethra can cause severe discomfort, painful and bloody urination and eventually urinary obstruction. Greater than 80% of animals with transitional cell carcinoma (TCC) of the urethra, and/or prostatic carcinoma experience dysuria and approximately 10% developing complete urinary tract obstruction. Chemotherapy and radiation therapy has been successful in slowing tumor growth but complete cure is uncommon. When signs of obstruction occur, more aggressive therapy is indicated. Placement of self-expanding metallic stents using fluoroscopic guidance through a transurethral approach can be a fast, reliable, and safe alternative to establish urethral patency in both males and females with a greater than 95% good to excellent palliative outcome. Urethral stenting may also be useful in patients with benign urethral strictures, or reflex dysynnergia, when traditional therapies have failed or when surgery is refused or not indicated. All animals that died after stent placement were due to reasons other than urinary obstruction, most of which being distant metastatic disease.
Case Example: “Happy” is a 13 year old Mix breed dog that had a prostatic carcinoma. He had radiation and chemotherapy, but was unable to pass urine through his urethra suddenly. After placement of a urethral stent through his tumor he was immediately able to urinate comfortably for the remainder of his life.
Urethral stent placement for malignant urethral obstruction. (A) Retrograde contrast urethrocystogram of male dog demonstrating narrowed urethral lumen at the level of the prostatic urethra (black arrows). Notice the marker catheter in the rectum (3) used to determine radiographic magnification and extrapolate normal urethral diameter (4) and obstruction length. (B) Urethroscopy of malignant urethral obstruction and loss of lumen patency. (C) Retrograde contrast urethrocystogram following self-expanding metallic stent in prostatic urethra demonstrating restored urethral patency (black arrows). (D) Urethroscopy following stent placement with restored urethral lumen.
Collagen injections via urethroscopic guidance has been performed for urinary sphinchter incompetence/urinary continence at many institutions. This procedure is indicated if medical management for SMI has failed, is contraindicated, or not tolerated. Overall success of the procedure is good, though the average maintenance of continence following this procedure is reported at 17 months, with re-injections being common thereafter.
Using a rigid cystoscope the urethra is cannulated and an area just caudal to the bladder trigone is identified within the urethra. A collagen heuber needle with syringe is inserted into the working channel of the cystoscope, being preloaded with the collagen material. A submucosal injection is made placing a bled into the urethral lumen. This is done in 3-4 areas, creating a new narrowing within the urethral lumen.
Another new technique that has been very helpful in the treatment for non-responsive urinary incontinence is with the use of a silicone ring that is placed around the urethra. This ring is called a hydraulic occluder. It allows for life-long adjustments in the strength of an artificial sphincter with a simple injection into a port that sits under the skin.
Chemotherapy plays a largely palliative role for solid tumors in veterinary patients. Most pet owners would not accept the complications encountered if their pets received the substantially higher doses of chemotherapy necessary to achieve the remission rates obtained in human patients. Intravenous (IV) chemotherapy doses used in veterinary patients are determined in order to achieve effective plasma levels without causing excessive morbidity; side effects from IV chemotherapy often result in dose-reductions which are less likely to achieve tumor control but will be better tolerated by the patient. Following an injection of IV chemotherapy, the drug flows centrally while being diluted by the other blood returning to the heart. Following dissemination via the arterial system, only a small proportion (and low concentration) of the drug will reach the actual tumor.
Alternatively, IR techniques permit fluoroscopically-guided, super-selective catheterization of the arteries feeding the actual tumor or body region. Intra-arterial (IA) administration of the systemic dose of chemotherapy permits significantly greater concentrations of the drug to reach the tumor without the systemic side effects that would be encountered had an equivalent IV dose been used to achieve the same local chemotherapy concentrations. Experimental studies in dogs and controlled studies in rabbits have documented the improved efficacy of these techniques in achieving higher local concentrations and improved tumor remission rates, respectively for certain types of tumors. These techniques have been used in veterinary patients for osteosarcoma and are currently being investigated in dogs with transitional cell tumors of the urinary bladder, urethra, and prostate.
Urethral catheterization is typically a fairly simple and routinely performed procedure in veterinary patients primarily used to monitor urine output, establish urine drainage in patients that are recumbent or have mechanical/functional urethral obstructions, or to provide urethral patency following urethral or urinary bladder surgery. Occasionally, standard retrograde catheterization can be difficult in very small (female) patients or feline patients with urethral tears following attempts to “de-obstruct” blocked cats or secondary to trauma. Antegrade urethral catheterization performed under direct fluoroscopic visualization can be performed rapidly, easily, and safely in patients in whom attempts at routine retrograde catheterization have failed.
Under general anesthesia (recommended) or heavy sedation, the patient is placed in lateral recumbency and the flank and caudal ventral abdomen are clipped and scrubbed. Cystocentesis is performed and contrast is injected to define the urinary bladder and urethra. Under fluoroscopic guidance, a guidewire is advanced through the cystocentesis catheter and passed antegrade into the bladder and down the urethra until exiting the penis or vulva. A urinary catheter is advanced over-the-wire in a retrograde fashion into the urinary bladder and the guidewire is removed. The urinary catheter is secured in place in a routine fashion.
Antegrade urethral catheterization in a cat following iatrogenic urethral tear during attempted retrograde catheterization for urinary obstruction. (A) Retrograde contrast urethrogram through tomcat catheter (black arrows) demonstrating peri-urethral contrast extravasation (*) and non-catheterized actual urethral lumen (white arrows). (B) Percutaneous cystocentesis with 18 gauge catheter (white arrow) and contrast cystogram of urinary bladder (UB). (C) Fluoroscopic-guided antegrade passage of hydrophilic angled guidewire (black arrows) through catheter (white arrow) and down urethra. (D) Retrograde passage of 5 Fr open-ended catheter (white block arrows) over the guidewire (black arrow) and up to 18 gauge catheter (white arrow). (E) Radiograph following removal of guidewire and 18 gauge catheter leaving urinary catheter (white block arrow) in place for urinary drainage while urethral tear heals.
Ureteral obstructions secondary to ureteroliths or malignancy can result in severe hydronephrosis and/or life-threatening azotemia when present bilaterally or in animals with concurrent renal insufficiency. Some patients can be managed with supportive care until a ureterolith passes, others may require surgery to avoid permanent damage and/or hemodialsysi to stabilize the patient prior to a prolonged anesthesia. Ureterotomies can be relatively prolonged and complicated surgeries in these often debilitated patients. One possibility is to place a nephrostomy tube percutaneously in order to quickly relieve the obstruction, and determine whether adequate renal function remains before prolonged anesthesia for ureteral surgery is performed.
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