Placing and managing urinary catheters and catheter collection systems (Proceedings)
The use of urinary catheters is a common part of veterinary practice. Indications for urinary catheters include urinary obstruction, urinary trauma, voiding disorders, urine diversion during or after surgery, or to monitor urine production. Additionally, catheters are sometimes used to perform contrast radiographic procedures, to collect urine or to collect cells and tissue samples from the lower urinary tract. Urinary catheters may be passed and removed (intermittent catheterization) or left in place for variable periods of time (indwelling urinary catheterization). Indwelling catheters are reserved for situations in which retention of urine or replacement of the catheter would be detrimental to the patient (e.g. severely ill obstructed cat, urethral trauma, or monitoring of acute renal failure). Urinary catheters described here are typically transurethral catheters. If the transurethral route is impossible, or a longer term urinary diversion is needed, antepubic catheters can be placed directly into the urinary bladder through the abdominal wall (cystostomy catheters).
Transurethral catheter placement
One key to successful use of urinary catheters is preparation. Prior to starting the procedure, all the possible supplies should be gathered:
• Sterile gloves
• Cleansing solution or soapy water
• Gauze pads or cotton balls
• Sterile lubricant (individual packets of sterile lubricant are ideal)
• Flushing solution (sterile saline)
• Syringes to withdraw urine and to save a urine sample
• Syringe to inflate catheter cuff (if using a Foley catheter)
• Bowl for larger volumes of urine
• Appropriate Catheter (plus extras) plus stylet (if appropriate)
• Mosquito forceps
• Drugs for sedation (if needed)
• Speculum and light source (females)
If the catheter is to be left indwelling:
• Tape and/or suture to secure catheter
• Extension line or intravenous fluid administration set
• Collection bag
• Elizabethan collar
The type and size of catheter depends on the patient to be catheterized and the length of catheterization anticipated. Polypropelene catheters (tomcat and longer urethral catheters) are easy to place because of their stiffness, but are more irritating to the patient. Small 3.5 French polypropylene catheters (TomCat catheters) are usually used to unobstruct male cats, but softer infant feeding tubes or specialized catheters can be used for longer term catheterization. Softer red rubber catheters are often used for male and female dogs and range in size from 3.5-8 French. Polypropelene catheters also can be used for one-time catheterization. If urethral catheters are to be left in for extended periods, then a Foley catheter may be placed. Foley catheters have a balloon at the distal tip of the catheter that may be filled with air or water. Once the catheter is inserted into the urinary bladder, the balloon is filled up and the catheter is pulled caudally to "wedge" the balloon in the area of the trigone, preventing it from slipping out. Foley catheters are especially useful in female dogs because of their relatively short urethra.
Urethral catheterization in dogs, especially males, is accomplished more easily than in cats because sedation is not often required. When placing urethral catheters, it is important to be as clean as possible, and if indwelling urethral catheters are placed, then it should be done as aseptically as possible. The hair may be clipped away from the vulva in female dogs and cats or the prepuce in male cats if needed. The area around the penis or vulva should be cleaned with warm soapy water to minimize inducing iatrogenic bacterial urinary tract infections. Only dilute chlorhexidine solutions or dilute betadine should be used around the penis or vagina (no alcohol!)
Placement of urethral catheters is easy in male dogs with the penis extended and the prepuce held out of the way. Resistance is felt at the base of the os penis and as the catheter curves around the perineal area. The catheter should be advanced just far enough to place the tip of the catheter at the entrance of the bladder and allow good urine flow. Placement of urethral catheters in female dogs may be accomplished by digital palpation, by use of a vaginoscope or otoscope, or by blindly "sliding" the catheter along the ventral floor of the vagina until it "drops into" the urethral orifice. Some small female dogs, or those with painful conditions, will need sedation or short-term anesthesia. Placement of urethral catheters requires sedation or anesthesia in cats. Following sedation of a male cat, I usually place them in dorsal or lateral recumbency to facilitate passage of the urethral catheter. The urethra of male cats has a small flexure located at the ischial arch. Placing them on their back allows you to straighten out the urethra by pulling the penis upwards (toward you) or caudally and dorsally towards the tail. Catheterizing female cats is accomplished in a manner similar to female dogs except that it also requires sedation or anesthesia.
Indwelling urinary catheters
Indwelling urethral catheters should be sutured to the perineal region by using a piece of tape as a butterfly. Indwelling catheters should always be connected to a "closed system" where there is no opening to the outside air. That is, they should be connected to an intravenous drip set and an empty non-glucose containing fluid bag (such as LRS or saline) to prevent the bladder from filling with urine, or capped and emptied periodically. If the urethral catheter is connected to an empty intravenous fluid bag, 20-30 ml of Betadine or Nolvasan can be preplaced in the bag to minimize risk of bacterial colonization. This closed system should be broken as infrequently as possible. When the urine bag is emptied or lines must be changed, the procedure should be done as aseptically as possible. The end of the urinary catheter should never be left open to drip continuously as this often results in urine scald as well as increasing the risk of bacterial migration and colonization of the urinary bladder.
Problems with indwelling catheters include kinking of the catheter or tubing, premature removal of the catheter, obstruction of the catheter with cells or crystalline debris, irritation or inflammation of the urethra, or introduction of urinary tract infection. Soft catheters are less likely to cause irritation of the urothelium when compared with catheters made of more rigid material. Administering a sympatholytic drug such as phenoxybenzamine may treat urethrospasm (most common in cats). The risk of bacterial urinary tract infection may be minimized by placing urinary catheters in a manner that is as clean as possible, using a proper collection system, keeping the insertion site clean, and by avoiding administration of antibiotics and immunosuppressive agents while the catheter is in place. While animals have indwelling urethral catheters in place, they should not receive antibiotics as a prophylaxis for bacterial urinary tract infections. Studies have shown that antibiotic administration to human beings, dogs, and cats with indwelling urethral catheters increases the risk of bacterial urinary tract infection and that when infections occur they have a high degree of antibacterial resistance. Once the animal is voiding normally and systemically out of danger, the indwelling urethral catheters may be removed. A urine sample can then be cultured to detect persistent urinary tract infection requiring treatment.
Although transurethral Foley catheters or modified feeding tubes may be used long term in dogs and cats, they are more difficult to manage over weeks to months and are more likely to be inadvertently removed. Furthermore, if the urethra is diseased, it may be impossible to pass a catheter through the urethra into the urinary bladder. Examples of such diseases include transitional cell carcinomas of the bladder and urethra, prostatic cancer, or intrapelvic urethral strictures. In these situations, the urethra must be bypassed and a urinary catheter inserted directly into the urinary bladder. These catheters are called cystostomy catheters. The advantage of cystostomy catheters is that they allow direct drainage of the urinary bladder. Cystostomy catheters can be left in for months and are easy for owners to manage. Placement of cystostomy catheters requires heavy sedation or anesthesia because a mini-laparotomy must be performed. Percutaneous cystostomy catheter kits are available, but there is limited experience in using them in dogs and cats. Cystostomy catheters must be kept clean. They are capped when not in use and owners uncap them to drain the urine from the bladder. Cystostomy catheters do not induce urethral spasm because they are inserted directly into the urinary bladder. With cystostomy catheters, bacterial urinary tract infections are inevitable. They should be treated as they occur, but can be minimized by administering the urinary antiseptic, methenamine, to dogs (but not cats) or by infusing Tris-EDTA through the catheter. These catheters can be used in dogs with lower urinary tract cancer and urethral outflow obstruction and may provide months of good quality life. The disadvantages of cystostomy catheters are that they require surgical placement and they are more expensive; however, their advantages far outweigh their disadvantages.
In summary, urinary catheters are valuable tools in the management of many diseases in dogs and cats. When managed properly, they provide a low risk method of keeping the urinary bladder empty or of providing a good quality of life for animals.