Timothy C. McCarthy, D.V.M., Ph.D., Diplomate ACVS
Lower urinary tract disease comprises a major portion of cases diagnosed and managed in small animal practice. However, the cornerstone for diagnosis and management of lower urinary tract disease used in human medicine, cystoscopy, has until recently received limited application in veterinary medicine. Advantages of cystoscopy over other diagnostic techniques are many, as it provides minimally invasive direct visualization of the vagina, urethral opening, urethra, bladder, and ureteral openings. Visualization of these structures, even where accessible by surgery, is far superior with cystoscopy because of magnification provided by the instrumentation and elimination of distortion that occurs with cystotomy or other surgical entry into the urinary tract.
The complete range of small animal patients can be evaluated with transurethral cystoscopy(TUC) using currently available instrumentation. This includes male cats that can be examined with a 1.2mm diameter flexible endoscope or with 1.9mm diameter or 2.7mm diameter rigid endoscopes after a perineal urethrostomy has been performed. Prepubic percutaneous cystoscopy(PPC) can be employed for evaluation of the bladder and proximal urethra in patients when these structures are not accessible transurethrally due to patient size, urethral disease, or lack of appropriate instrumentation. Access is limited in very small patients and in male cats. PPC is also more difficult or technically demanding in very small patients.
Cystoscopy is recommended as the primary diagnostic tool for urinary tract evaluation in any chronic or acute urinary tract disease which is difficult to diagnose or resolve. Specific indications include chronic cystitis, acute or chronic hematuria, straining or difficult urination, increased frequency of urination, urinary incontinence, alteration of urinary stream, urinary tract trauma, cystic calculi and urethral calculi. Cystoscopy is the procedure of choice for assessing cases with suspected ectopic ureters and is far superior to radiographic contrast studies or to operative assessment. Cystoscopy is also the procedure of choice for evaluation of possible urinary tract trauma allowing rapid and complete assessment of the vagina, urethra, bladder, ureters and kidneys. The kidneys and ureters are assessed by observation of the presence and character of urine being produced by each ureter.
Five endoscopes are used for transurethral cystoscopy in small animals. Rigid telescopes include a 1.9mm cystoscope with 300 viewing angle, a 2.7mm diameter arthroscope or multipurpose rigid telescope with 300 viewing angles, and a 4.0mm diameter cystoscope with 300 viewing angle. The 2.7mm diameter multipurpose rigid telescope and the 1.9mm diameter cystoscope have been used for transurethral cystoscopy in female dogs ranging in size from 2.3kg to about 20kg, in female cats, and in male cats after a perineal urethrostomy has been performed. The 4.0mm diameter cystoscope has been used in female dogs over about 20kg. Rigid telescopes are available for cystoscopy with viewing angles from zero degrees to 120 degrees. The most effective angle for diagnostic transurethral cystoscopy is 30 degrees. Flexible endoscopes include 2.8mm diameter and 1.2mm diameter cystourethroscopes. The 2.8mm diameter(8.5 French) flexible cystourethroscope has a 2.8mm diameter insertion tube, a 2.5mm diameter(7.5 French) distal tip with two way tip deflection control and a range of 170 degrees up to down 90 degrees, a working length of 100cm, and a biopsy channel that will accommodate 1.0mm(3 French) instruments. This endoscope is used for transurethral cystoscopy in most male dogs. The 1.2mm diameter(3.6 French) cystoscope has a working length of 50cm, a 0.3mm(one French) infusion channel that is too small for passage of instrumentation, and does not have distal tip deflection control. This endoscope is used in male cats and in very small male dogs. Biopsy forceps, cytology brushes, stone baskets, stone and foreign body graspers, and urethral dilators are available for use with these rigid and flexible endoscopes with the exception of the 1.2mm diameter flexible cystourethroscope.
For prepubic percutaneous cystoscopy the 2.7mm diameter multipurose rigid telescope can be used for the entire size range of small animal patients. This telescope is used with its arthroscopy sheath and a sharp trocar to penetrate the abdominal and bladder walls. An appropriately sized laparoscopy cannula with a sharp trocar, combined with a telescope guard sheath, can also be empolyed for PPC with this telescope. A second puncture cannula and trocar with rigid biopsy forceps and graspers are needed for sample collection. In very small dogs and in cats a 1.9mm diameter arthroscope may have some advantages and a 5mm diameter laparoscope may be used in large dogs.
General anesthesia has been employed for all types of cystoscopy. Irrigation with a continuous or interrupted flow of sterile physiologic saline solution has been used for urinary tract distension in the majority of transurethral and prepubic percutaneous cystoscopies. Examination of the urinary tract can also be done using air, nitrous oxide, or carbon dioxide.
TRANSURETHRAL CYSTOSCOPY IN FEMALE DOGS AND CATS:
For transurethral cystoscopy in females the endoscope is passed under direct visualization using continuous fluid flow. Patient positioning is usually right or left lateral recumbency but dorsal or ventral recumbent positions may also be employed. Position varies depending on the individual case and personal preference. Aseptic preparation and draping is not employed routinely but may be required in some circumstances. Continuous irrigation is most commonly done by connecting a liter bag or bottle of sterile physiologic saline or Ringerís solution to the endoscope irrigation port with a standard intravenous administration set. The fluid reservoir is placed anywhere from 5cm to 80cm above the patient. Fluid flow is initiated and the endoscope is passed into the vagina, the urethral opening is visualized and the scope is passed into and through the urethra as it is distended. Urethral evaluation is conducted as the endoscope is advanced. This technique is easier, faster and safer than blind or speculum passage. Safety of transurethral cystoscopy is greatly enhanced with this direct visualization technique because any pathology can be identified and avoided thus reducing the chance of urethral wall damage or penetration during passage of the endoscope.
Once the bladder is entered fluid flow is arrested and urine in the bladder is completely drained through the endoscope. Fluid flow is reinstituted and examination of the bladder is carried out while the bladder is filling. If the urine is concentrated or contains blood examination may be hampered by cloudiness of bladder irrigation fluid and additional saline exchanges may be required to obtain a clear viewing field.
The bladder may also be distended with air, nitrous oxide, or carbon dioxide. Gas distension has been employed primarily when bleeding produced persistent cloudiness of the viewing liquid. When gas distension is used, occasional small amounts of saline irrigation may be needed to keep the endoscope lens clean.
Caution must be employed to prevent over distension of the bladder and subsequent damage. Rupture of the bladder is an uncommon complication of cystoscopy but can occur if there is extreme over distension or severe bladder wall pathology. Partial rupture may also occur with mucosal tearing but with the seromuscular layers remaining intact. The most common form of bladder wall damage during cystoscopy is microscopic mucosal tears causing bleeding that interferes with examination. This form of damage occurs most frequently in bladders with significant chronic inflammation and secondary scar tissue formation which prevents normal bladder wall stretching.
The entire urethra and bladder wall can be evaluated with the 300 angle of view telescopes. The urethra is evaluated for tumors, calculi, ectopic ureteral openings, strictures, contusions, mucosal lacerations, and wall penetrations or disruption. The entire bladder is examined for the presence of tumors, calculi, diverticula, mucosal tears, bladder wall lacerations or penetrations and for proper location of ureteral openings. Both ureteral openings are found and assessed for location, configuration and for flow and character of urine. The bladder mucosa is evaluated for contour, texture, color, and for blood vessel number, size and configuration.
Biopsy samples are easily obtained with telescopes utilizing the cystoscopy cannulas with biopsy channels. When arthroscopy cannulas are employed for examination, biopsy collection is complicated by the absence of an instrument channel. Several options are available for collecting samples when an arthroscopy cannula is used. For localized urethral lesions, when there is adequate space, biopsy forceps can be passed beside the endoscope. With generalized bladder wall disease where location of the biopsy site is not important, the telescope can be removed and biopsy forceps passed blindly through the endoscope cannula while it is still in the bladder. Another alternative, required for localized bladder mucosal lesions, is to perform a prepubic percutaneous puncture for passing biopsy instrumentation while maintaining transurethral placement of the endoscope. Sample collection is then done through this percutaneous cannula while instrumentation is guided to sample collection sites with the transurethrally placed endoscope. When percutaneous puncture is performed an indwelling urinary catheter is placed and maintained for 48 to 72 hours to keep the bladder empty and allow bladder puncture wounds to seal. The skin puncture wounds are closed with single skin sutures.
TRANSURETHRAL CYSTOSCOPY IN MALE DOGS AND CATS:
Transurethral cystoscopy in male dogs and cats is also performed by passing flexible endoscopes through the urethra with fluid distension. Lateral recumbency is most commonly employed. The bladder is emptied with a catheter prior to endoscopic examination because this is easier and faster than emptying the bladder through the small diameter of flexible endoscope operating channels. This is especially true with a distended bladder in a large dog or with male cats when the 1.2mm diameter cystoscope is used. Examination of the urethra can be done as the endoscope is being advanced or as it is being withdrawn. If the endoscope has tip deflection control examination is greatly facilitated and the urethra is followed and examined by changing the tip angle. The 1.2mm diameter flexible cystourethroscope does not have tip deflection control and examination is carried out by manipulation of the endoscope externally through the penile and urethral tissues.
To pass the endoscope transurethrally the prepuce is retracted exposing the tip of the penis, which is then cleaned, and the endoscope is introduced with continuous fluid irrigation to allow passage of the endoscope under direct visualization. The distal segment of the urethra from the tip of the penis to just below the ischial arch is relatively straight and can usually be followed and examined easily with minimal manipulation. Resistance to passage of the endoscope tip may be encountered in the area of the caudal end of the os penis which is normally the narrowest point of the urethra. Gentle pressure and manipulation may be employed to get the endoscope through this portion of the urethra. Excessive force is not used. If the endoscope cannot be passed the urethra can sometimes by dilated by passing increasing sizes of well-lubricated soft blunt tipped urinary catheters or with a balloon dilator.
Examination is greatly facilitated by endoscope tip deflection control as the tip, and corresponding field of view, is simply deflected to follow the curve of the urethra and to examine areas of interest as indicated. Without tip control the endoscope and surrounding urethra must be manipulated digitally to accomplish urethral and bladder examination. Manipulation of the urethra is done by grasping the urethra and surrounding tissues and pulling them away from the body while pushing the more distal urethra toward the body. This procedure is repeated as the hand is moved proximally and distally relative to the tip of the endoscope. Side to side movement may also be required to complete the examination. In the pelvic urethra manipulation is continued by rectal palpation. Evaluation of the bladder is carried out using transabdominal manipulation of the bladder to move various portions of the bladder wall in front of the endoscope until the entire bladder has been examined.
Biopsies are taken with flexible forceps through operating channels of the 2.8mm flexible cystourethroscope. The 1.2mm cystourethroscope is too small to permit passage of instrumentation. Urethral biopsies and bladder biopsies for generalized disease may then be taken by blind passage of flexible biopsy forceps. For localized urethral disease the distance to the urethral lesion is measured with the endoscope and flexible biopsy forceps passed to the same level. Manipulative control similar to that employed for flexible endoscopes without tip control may be used to assist with sample collection. Localized bladder lesions can be reached for biopsy by single percutaneous prepubic puncture for insertion of biopsy forceps combined with transurethral endoscope placement as was described for female dogs and cats.
Transurethral cystoscopy can be performed in male cats after a perineal urethrostomy has been performed using the 1.9mm rigid cystoscope or the 2.7mm universal telescope and itís arthroscopy sheath. This technique can be done immediately after surgery or delayed until healing is complete. When performed immediately after surgery there is the advantage of only requiring one anesthesia but great care must be taken to prevent damage to the stoma suture line. Delayed examination has less risk of damage to the surgery site but requires a second anesthesia.
PREPUBIC PERCUTANEOUS CYSTOSCOPY:
The procedure for PPC requires general anesthesia and aseptic technique. Dorsal recumbency is employed. The bladder is catheterized and emptied using a standard urethral catheter. This catheter is then connected to an intravenous administration set and sterile physiologic saline or Ringerís solution is used to fill the bladder to moderate distension so that the wall is firm but not hard. The abdominal wall is prepared and draped for aseptic technique similar to what would be used for a cystotomy. Sterilized endoscopic instruments are used. Sterilization can be performed with cold sterilization solutions (i.e. glutaraldehyde), with ethylene oxide, or by autoclaving. The instrument manufacturersí recommendations for sterilization are followed.
A small skin incision is made over the bladder and the endoscope cannula and trocar are inserted through the abdominal and bladder walls. The endoscope cannula with a sharp trocar is pushed through the abdominal and bladder walls with continuous gradually increasing pressure and oscillating rotation until the bladder lumen is entered. The instrumentation is held perpendicular to the bladder wall at the site of penetration during this maneuver. Caution must be used to prevent the trocar from being inserted too far as damage can occur to the opposite bladder wall and structures outside the bladder. Once the trocar and cannula assembly is appropriately placed in the bladder the trocar is removed and replaced with the telescope. Fluid inflow is transferred to the endoscope cannula using a new sterile intravenous infusion set and the initial transurethral infusion set becomes a drainage system for fluid outflow. Flow rate is adjusted to maintain bladder distension and to maintain a clear field of view. Bladder distension can also be maintained using a syringe to allow intermittent injection of fluid. This technique applies better to smaller dogs and cats because it allows more precise control reducing the risk of bladder over distension.
The entire mucosal surface of the bladder wall can be visualized except for an area immediately surrounding the puncture site. The proximal portion of the urethra can be evaluated usually to the caudal end of the prostatic urethra. If sample collection is required a second puncture is performed using technique similar to that used for placement of the endoscope cannula.
After examination has been completed and samples collected the bladder is drained to relieve wall tension and the endoscope and biopsy cannula are removed. Single abdominal wall and skin sutures are placed. The urethral catheter is left in place for 48 to 72 hours to keep the bladder empty and allow sealing of the bladder wall puncture wounds.
COMPLICATIONS AND CONTRAINDICATIONS:
There are several limiting factors in selecting cases for cystoscopy but there are no defined contraindications in veterinary medicine. In human medicine rupture of the bladder and severe bladder infections are considered to be contraindication for cystoscopy. Urinary tract trauma is an indication for cystoscopy in small animals. Bladder rupture, traumatic in origin or due to other causes, does not interfere with transurethral cystoscopy but makes percutaneous cystoscopy difficult to impossible depending on ability to distend the bladder. Infusion of sterile saline or Ringerís for performing the procedure is not detrimental to the patient. In cases with severe infections irrigation of the bladder during cystoscopy removes bacterial and inflammatory debris and is therapeutic.
Animal size and sex are limiting factors only in that they dictate the specific instrumentation and technique to be used. Urethral lesions such as tumors can prevent passage of the endoscope transurethrally. Small thick walled bladders that cannot be distended adequately may be difficult or impossible to enter for percutaneous cystoscopy.
The most common problem encountered during cystoscopy is difficulty with visibility due to hematuria or highly concentrated urine. Difficulty with visualization can be overcome by repeated drainage and filling of the bladder with clean solution or by using gas for distension of the bladder.
Over distension can occur in the normal bladder due to excessive filling or with normal filling of a diseased bladder. Significant complications have included two bladder ruptures, one case of persistent urine leakage from puncture wounds and one urethral laceration.
Cystoscopy has proven to be a highly effective technique for diagnosis of lower urinary tract disease in dogs and cats providing easy access for obtaining information not readily obtained by other diagnostic procedures. It is the authorís prediction that when cystoscopy reaches itís proper place in veterinary medicine itís use will exceed the use of gastrointestinal endoscopy. It is also predicted that cystoscopy will completely redefine lower urinary tract disease in veterinary medicine.