Smallest ureteral stent currently available (Cat ureteral stent) 2.5Fr tapered to a 0.018" wire is THE SMALLEST ureteral stent made Multiple Fenestrations along the stent shaft Permits multiple areas for urine drainage; reduces stent obstructions Customized small diameter pigtails and variable lengths Permits placement in even very small cat renal pelvises and various length ureters Radiopaque and Hydrophilic Allows precise placement and reduced friction

Dual stiffness configurations Stiffer version facilitates placement and reduces buckling while softer version improves patient comfort Cancer Stent Optimized for malignant ureteral obstructions with no fenestrations at distal half of ureteral stent shaft Customized Pusher/Dilator Various diameter, custom tapered dilators facilitate stent placement in the smallest ureters and have dual use as stent pusher for endoscopic placement

Stent Size (diameter)	Shaft Length Options (cm)	Coil Diameter (mm)	Pusher length x diameter	Indication	Guide Wire size (diameter)	Ureteral Catheter Size  Recommended (French)
2.5 french (soft or stiff **see instructions)	12,14,16 cm	6 mm	45 cm long x 0.034” wide	Feline	0.018”	0.034” dilator-pusher comes with stent (**see instructions) (sold separately)
3.7 french	12,15,18 cm	6 mm	45 cm long x 4 french wide	Small dog	0.025”	4 french (sold separately)
4.7 french	16, 18, 20 cm	10 mm	45 cm long x 5 french diameter	Medium or large dog	0.035”	5 french (sold separately)
6.0 french	17, 20, 23 cm	12 mm	60 cm long x 7 french diameter	Tumor at UVJ (dog)	0.035”	7 or 8 french sheath (**see instructions) (sold separately)

Case Study 1

Endoscopic placement: female dogs, male dogs (>8kg), female cats (often need surgical assistance) (Figure 1)

FIGURE 1: Endoscopic stent placement (canine)

The patient is placed under general anesthesia and positioned in dorsal recumbency on a fluoroscopy table. For a female patient the vulva should be hanging off the end of the table for the easy of cystoscopy. The vulva is clipped, scrubbed and draped. Peri-operative antibiotics are routinely used unless the patient is already receiving appropriate antibiotic therapy. A marker catheter is placed per rectum and gently advanced into the terminal colon over a floppy-tipped (soft, atraumatic) hydrophilic guide wire or inside a soft rubber catheter that is advanced per-rectum. Using a cystoscope (rigid in female and flexible in male) the ureterovesicular junction (UVJ) is identified (Figure 2F) and the appropriate side is confirmed fluoroscopically. The fluoroscopy unit is positioned over the bladder neck and distal ureter (Figure 1A). The appropriately sized hydrophilic angle-tipped guide wire (Weasel wire) is advanced through the working channel of the cystoscope. Using endoscopy the guide wire (see sizing chart) is manipulated and aimed up the UVJ and into the distal ureter. (Figure 1A, 2F, 2G) An open-ended ureteral catheter (see sizing chart) is then advanced over the guide wire to the level of the distal ureter. (Figure 1A, 2G) This is more easily accomplished when the cystoscope is situated at

FIGURE 2: Endoscopic Stent placement (Feline)

the UVJ and should not be moved from this position for appropriate pushablility. The guide wire is removed and contrast (iohexol) diluted 1:1 with saline is infused up the catheter for a retrograde ureteropyelogram (RUPG) (Figure 2A, 2B). Be sure to fill the entire ureter and renal pelvis for mapping. The guide wire is then re-advanced up the ureter through the catheter and directed around the obstruction and into the renal pelvis. (Figure 1B, 2C) Care should be taken not to perforate the ureter at the obstruction site. Once the guide wire is in the renal pelvis the catheter is advanced over the guide wire, passing the obstruction. Using either the marks on the ureteral catheter, or the marker catheter in the colon, the ureteral shaft length should be determined from the UPJ to the UVJ. The stent length should be chosen accordingly.

The ureteral catheter should be carefully removed over the guide wire without removing the guide wire. The stent should be loaded on the guide wire, through the working channel of the cystoscope (making sure you have the appropriate sized working channel to accommodate your stent diameter). The stent can be advanced over the guide wire, while the scope is situated at the UVJ and should not be moved. This allows for pushablility of the stent up the ureter, as the stent is very soft compared to the catheter (2F, 2G). Using fluoroscopy the stent should be advanced over the guide wire, being sure that the wire is monitored in the renal pelvis and it remains in place (Figure 1C, 2D). Once the stent is fully inside the cystoscope the dilator-pusher catheter should be advanced over the wire to "push" the stent inside the cystoscope. Once about 1 cm of the stent is seen inside the renal pelvis, or on endoscopy the "Black line" is seen, indicating the distal shaft of the ureteral stent, the wire can be slowly withdrawn (2D). If you see the line and the stent is not yet inside the renal pelvis, than this stent is too short and should be exchanged for a longer stent. One loop should be seen in the renal pelvis (2E). The wire can be withdrawn to the distal ureter, just crossing the distal stent, so that it is across the stent and pusher catheter. The cystoscope can be withdrawn into the proximal urethra while the pusher catheter is advanced to push the distal end of the stent into the urinary bladder. The wire can be removed and the distal pigtail should be inside the urinary bladder (Figure 1D, 2E).

Case Study 2

Surgical Stent Placement: male cats, female cats, dogs without endoscopic access

FIGURE 3: Antegrade Stent placement (Feline)

In dogs where endoscopic access is not possible the procedure is done surgically. The UVJ in dogs is in the bladder trigone and ureter access can be obtained by a distal cystotomy, where you can visually identify the appropriate ureteral orifice. The same steps are followed as above for the endoscopic procedure, though you do not need an endoscope. A guide wire is advanced up the ureteral orifice, with an open-ended ureteral catheter advanced over the guide wire into the distal ureter. Using fluoroscopy a RUPG is performed and the same steps as above are followed. For surgical placement a pusher catheter is not necessary as you can put the distal loop in the bladder manually.

In most cats surgical assistance is necessary in ureteral stent placement. In female cats endoscopic guide wire access is initiated and then the abdomen is open for stent manipulation if necessary. In male cats the entire procedure is done surgically. The options for guide wire ureteral access are either antegrade (from the kidney) or retrograde (from the bladder-UVJ). It is important to remember that the UVJ in cats are located in the proximal urethra, not the bladder, so a urethrotomy is necessary, which is why antegrade access through the kidney is often performed.

Antegrade access: (Figure 3) The patient is placed under general anesthesia. The abdomen is clipped and aseptically prepared, including the prepuce or vulva. The animal is placed in dorsal recumbency. The entire abdomen from sternum to prepuce/vulva is draped. Via laparotomy the appropriate kidney is isolated. A 22gauge over-the-needle intravenous catheter is used to gain renal pelvic access (Figure 3A). This is done through the greater curvature of the kidney. Fluoroscopy is aligned over the kidney and proximal ureter. The catheter is prepared with a T-port, 3-way stopcock and 2 syringes (1 syringe [5cc] of contrast [diluted 1:1 with saline] and one empty syringe [5 cc]). Once urine is seen from the catheter the needle is removed and the T-port is attached. Using the stopcock urine is withdrawn (for culture) and then contrast in infused under fluoroscopic guidance. Once a pyelogram and ureterogram are visualized the T-port is removed leaving the catheter in place and the 0.018" Weasel wire is advanced into the renal pelvis through the catheter (Figure 3B). It is manipulated down the ureter, bypassing the obstruction, and through the UVJ into the urinary bladder (Figure 3C). Once the wire is inside the urinary bladder either a small, distal cystotomy can be performed to grab the guide wire for through-and-through wire access or the wire can be passed out the urethra (Figure 3D).

The feline stent (2.5 french*) comes with a ureteral dilator-pusher** (0.034"). This is tapered to the 0.018" guide wire. This should be used to pass over the guide wire to dilate the UVJ and the small ureteral diameter distal to the obstruction. This can be done either retrograde or antegrade (through the kidney). Once this catheter is passed from the bladder to the kidney the wire should be reversed so that the soft, angled tip is on the kidney side, rather than the current bladder side. This is because the wire needs to curl inside the renal pelvis to get the proximal end of the stent curled in the renal pelvis. This should NEVER be done with the stiff end of the wire. Once the wire is reversed than the dilator-pusher catheter can be removed and the stent can be placed over the wire. Once the stent is inside the entire ureter the guide wire should be withdrawn so that the soft angled tip is inside the renal pelvis and curled. The stent should then be advanced over the guide wire until a curl is made and the wire can be withdrawn at the bladder side. The distal end of the stent can then be placed inside the bladder through the small cystotomy (Figure 3E). The cystotomy incision can then be closed and fluoroscopy should be used to confirm the stent is curled in the renal pelvis and inside the urinary bladder. *The 2.5 french feline ureteral stent comes in a soft and a stiff durometer. If the ureter distal to the obstruction (normal diameter) is very difficult to bypass with the soft stent, as it is usually tight, than you can try the stiffer stent, which may have more success. The concern about the stiff stent is that is could result in more post-operative dysuria, as the material in the bladder could be irritating in some cats. **The ureteral dilator-pusher that comes with the ureteral stent is 0.034" diameter. There are also 0.032" and 0.036" dilators sold separately which are often helpful in circumstances when the ureter is too tight for the stent.

Case Study 3

CANCER STENT***: For trigonal neoplasia induced ureteral obstruction (Figure 4)

FIGURE 4: Percutaneous antegrade access (Canine-Tumor)

Ureteral access for stent placement in patients with UVJ obstructions secondary to neoplasia is typically performed in an antegrade manner due to the lack of visibility of the UVJ cystoscopically. Female dogs occasionally can have placement success via transurethral cystoscopy as described above, but this is uncommon as the tumor makes the UVJ impossible to visualize.

The patient is placed in lateral recumbency with the affected kidney facing up. The dorsal paracostal and flank areas and the perineum (female) or prepuce (male) are clipped and aseptically prepared and draped. A marker catheter is placed over-the-wire or within a red rubber catheter per rectum and advanced into the descending colon to allow for ureteral length measurement to aid in choosing the appropriate stent shaft length (Figure 4). A 3mm skin incision is made over the kidney. Using ultrasonographic and fluoroscopic guidance, an 18 gauge renal access needle is used for antegrade ureteropyelography (Figure 4A). A urine sample is obtained and cultured. Iodinated contrast material diluted 1:1 with sterile saline (approximately the same volume of the urine removed) is injected. Using fluoroscopic guidance, a 0.035" stiffened Weasel wire is advanced through the needle and guided caudally through the lumen of the ureter to the level of the ureteral obstruction at the UVJ (Figure 4B). The guide wire is manipulated gently and advanced into the urinary bladder. If the guide wire meets considerable resistance at the level of the tumor, the renal access needle is removed over the guidewire and a 5 french vascular access sheath is advanced over the guide wire into the renal pelvis allowing for contrast injection into the renal pelvis to maintain a ureterogram during wire manipulation. If necessary, a combination guide wire and 4 french angled Berenstein angiographic catheter is used to achieve access across the tumor (Figure 4C, 4D). Once urinary bladder access is achieved, the wire (and catheter if used) is directed toward the bladder trigone and down the urethra caudally until "through-and-through" wire access is obtained as it exits the urethra (Figure 4E). This wire is termed the "safety wire". A 7 French 45 cm introducer sheath and dilator set are then advanced retrograde over the "safety wire" through the urethral lumen and across the tumor and UVJ to the level of the mid ureter (Figure 4F). This sheath dilates the ureteral obstruction. The dilator is removed over the guide wire and a second 0.035" un-stiffened angled Weasel wire is placed directly through the sheath, with the soft-angled tip advanced cranially in the ureteral lumen in a retrograde manner until it curls in the dilated renal pelvis (Figure 4F). The second wire allows the stent to be placed without losing through-and-through wire access maintained by the "safety wire" in the event the stent placement is not ideal and needs manipulation (Figure 4G). The appropriate stent length is chosen based on ureteral length measurements using the marker catheter in the colon. The 6 french Vet Stent-Ureter (cancer) is then advanced over the 2nd guide wire through the sheath in a retrograde manner to bypass the obstructed lesion. The pusher catheter is advanced over the same wire in order to advance the ureteral stent into position. Once the proximal end of the stent is advanced into the renal pelvis the 7 French sheath is withdrawn into the urethra and the 2nd guide wire (over which the stent is placed) is retracted to allow a pigtail to curl in the renal pelvis (Figure 4G). The pusher catheter is used to advance the distal end of the stent into the urinary bladder. Once the stent is in place the primary through-and-through "safety wire" is carefully removed through the urethra, leaving the double pigtail stent in place (Figure 4H).

***The cancer stent is designed to have multiple fenestrations in the proximal half of the stent, and the distal loop, but not the distal shaft. This is to prevent tumor in-growth at the UVJ, which could occlude the stent. It is important to remember this when loading the stent for placement.

Instructions for Use

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