Guide to Ureteroscopy
1) Ureteroscope technology continues to improve (See ureteroscope overview article). The key components are the diameter of the scope (now down as low as 7.5Fr), the lumen of the working port (around 3.5 Fr), and the diameter of the working element (eg. laser fiber or basket). Water flow decreases as the diameter of the working element approaches the diameter of the port making visualization more difficult.
2) “Safety wire”: Always have an extra wire fully up the ureter and set securely aside when performing ureteroscopy. The rationale is that if there is any significant trouble during the procedure (eg. ureteral perforation or “red-out”), the ureteroscope can be removed and a stent can be placed over the safety wire.
3) Patients with pre-existing urinary infections, or, particularly, an infected stone, can become quickly septic with significant ureteral manipulation. Ureteroscopy should be avoided in these patients.
|Figure 1: Flexiable ureteroscopes can access the entire urinary collecting system for treatment of stones throughout the upper urinary tract.|
There are numerous different types of wires which are used in Urologic procedures reflecting the many different ways in which wires are utilized. Their most common functions are to a) gain access to the ureter, and b) act as the inner component of a coaxial system allowing stents, catheters, and other working devices to be safely passed into the collecting system. The basic characteristics of interest which differ among wires are flexibility, lubricity, and shaft stiffness. Wire diameters typically range from 0.018 to 0.038 inches, with 0.035 and 0.038 wires used most frequently. The tips are often made flexible in order to minimize ureteral trauma. Here, we review the most commonly used wires.
1) Guide or “House” wire: Standard all-purpose wire with moderate stiffness. It is the most commonly employed wire and is often used for placement of ureteral stents and/or initial access to a ureter.
2) Hydrophilic or “Glide” wire: Very slippery and flexible. Comes in both angled-tip and straight-tip varieties. Utilized to gain access where access is difficult. Examples include ureteral orifices which will not pass a ureteral catheter, ureters with a stone or stricture blocking passage of a wire, or urethras which will not allow a Foley catheter to pass. Note: difficult to handle due to slipperiness, therefore needs to be exchanged for another wire once access is achieved.
3) Super-stiff: These very rigid wires provide secure access to a ureter and are used to pass sheaths, stents, or other working devices such as balloon dilators.
4) Double flexible tip: These wires with moderate shaft stiffness are primarily utilized for passing the flexible ureteroscope. The advantage of the 2nd flexible tip is that it decreases trauma to the (expensive) ureteroscope as it is passed over the wire.
Ureteral access and pyeloscopy:
1) Cystoscopy to gain access to the bladder
2) A 5 Fr open-ended ureteral catheter is typically used to gain access to the ureteral orifice, though the ureter can also be directly cannulated with a wire
3) A retrograde pyelogram may be performed through the ureteral catheter to delineate the anatomy of the collecting system
4) Using fluoroscopic guidance, a wire is then passed through the ureteral catheter and up the ureter into the renal pelvis. This is often a double floppy tip wire which will be used to pass the ureteroscope.
- If there is any difficulty passing the wire (eg. due to a ureteral stone), a hydrophilic (glide) wire is passed into the renal pelvis. The open-ended catheter is passed over the wire into the renal pelvis and the glide wire is replaced with another, more sturdy wire.
5) The ureteral catheter is then removed
6) A second wire—the “safety wire”—is then passed by any of a variety of means. Steps 2-4 may be repeated, or devices such as a ureteral access sheath or a dual lumen ureteral access catheter may be employed.
- The access sheath or catheter have the advantage of both allowing quick passage of a second wire and dilating the distal ureter. This facilitates passage of the ureteroscope and may save then need for further ureteral dilation such as with a balloon dilator.
- The dual lumen catheter is inserted over a wire, through the cystoscope sheath, and under fluoroscopic guidance. The second wire (typically a Guide or Super-stiff wire) is passed through the second port and the dual lumen cather is removed
- The ureteral access sheath is passed directly over a wire without using the cystoscope. It provides continuous, direct access to the ureter which can be useful when the ureteroscope has to be passed in and out repeatedly (eg. when basketing small stones or obtaining ureteral biopsies).7) With two wires in place, the safety wire is secured well to the drapes and set aside
8) The double floppy tip wire is used to pass the ureteroscope. The flexible ureteroscope is passed under fluoroscopic guidance over the wire all the way up to the renal pelvis (unless there is a ureteral stone or stricture blocking its path)
- If the scope cannot pass through the ureteral orifice—typically the most common hang-up—it may help to ensure the bladder is empty (by passing the cystoscope). Otherwise, it may be necessary to pass a balloon dilator over the wire and dilate the orifice.
- The scope is easiest to pass without any attachments (ie. camera, light cord), then hook the scope up to everything after it is in place
9) Fluid is attached to the ureteroscope. This is typically pressurized normal saline.
10) Pyeloscopy is then performed. Contrast can be first injected through the ureteroscope to delineate the calyceal system. The calyces are then systematically visualized with the ureteroscope.
11) Further procedures such as laser lithotripsy, stone basketting, ureteral biopsy, etc.can now be performed
12) When complete, the ureteroscope is gradually removed with visualization of the entire ureter
13) The safety wire is still in place and can now be used for placement of a stent if necessary. Otherwise, the wire can be removed.
- Holmium:YAG laser is most commonly used
- The laser is delivered using flexible quartz fibers which come in different diameters, typically approximately 200, 365, and 550 microns. Larger fibers deliver more energy faster, however the flexibility decreases with increased diameter
- Key concept: maintain contact with stone in order to fragment it while avoiding contact with urothelium. The urothelium will bleed with trauma, making visualization difficult.
- The two main techniques employed for lithotripsy are to 1) fracture the stone into multiple tiny fragments which will pass on their own or may be basketted, or 2) gradually “dust” each stone, a tedious process but with the goal of clearing the entire upper tract by the end of the procedure
|Figure 2: Ureteroscopic view of an 8mm proximal ureteral stone. A safety wire is seen at 10 o'clock. (click to watch video).|
- Patients are typically discharged the same day as the procedure.
- Patient should expect renal colic post-op, and, if stent placed, may have intermittent flank and lower abd pain while stent is in place.
- There is a significant risk of UTI post-op. Patients should receive single-dose IV abx (fluoroquinolone or cefazolin) pre-op. Patients may be sent home with up to 3 days of oral antibiotics for UTI prophylaxis although there is minimal evidence to support this practice.
- Patients undergoing ureteroscopic manipulation of a solitary kidney are at highrisk for post-obstructive diuresis. These patients usually need to be admitted and their fluid balance and electrolytes need to be closely monitored.