Chapter 138 Urinary Catheterization
Urinary catheterization is performed for diagnostic, treatment, or monitoring purposes and often is indicated in critically ill patients. Sex and species differences may offer anatomic challenges that can be overcome with proper technique and practice. Each patient should be evaluated individually for a clear indication for the procedure, type of urinary catheter to be used, and the duration of which the catheter is to remain in place. Indications for urinary catheter placement can be grouped into those warranting a one-time or intermittent placement and those in which the catheter should be left in place.
One-time or intermittent urethral catheterization can be used to obtain urine samples, perform radiographic contrast procedures, or relieve an anatomic or functional obstruction leading to urine retention. Samples for urinalysis may be obtained via catheterization, although bacterial and red blood cell contamination may occur.1,2 Additionally, retrieval of small stones from the bladder has been described using urinary catheters. Urinary contrast imaging procedures, such as a contrast urethrocystogram, assess the integrity of the lower urinary tract and can help characterize bladder masses, calculi, and urethral obstructions due to neoplasia, a calculus, or a foreign body. Lastly, urethral obstructions may be relieved or bypassed with a urinary catheter. Retrohydropulsion can be used to help dislodge calculi.
Indwelling urinary catheters allow for continuous urine collection and, based on human guidelines by the Centers for Disease Control and Prevention, are indicated for urinary obstruction, urine retention due to neurogenic bladder dysfunction, surgery of the lower urinary tract, or in critically ill patients for accurate urine output determination.3 Simple recumbency or wishing to prevent the patient from soiling itself is not a justifiable indication.
Catheter-associated UTIs have been reported in the veterinary literature and the incidence may exceed 50%. These infections have played a role in nosocomial outbreaks in veterinary intensive care units (ICUs) and have the potential to cause serious morbidity and mortality. Resistant bacteria such as Klebsiella, Acinetobacter, Enterobacter, Citrobacter, Serratia, Pseudomonas spp, and Escherichia coli may cause catheter-associated UTIs in veterinary ICUs and may serve as a source within the ICU for other nosocomial infections.4-9
Catheter-associated UTIs are thought to occur as a result of introducing bacteria into the bladder during catheter insertion. In one study, there was a 20% incidence of UTIs following a one-time catheterization in female dogs.10 Once indwelling, the catheter provides a surface on which bacteria may migrate. This often involves a biofilm, a matrix of microorganisms and their produced glycocalyces, host salts, and proteins. Biofilms allow for the adherence of bacteria to catheter surfaces and provide protection from the host’s defenses. Not surprisingly, duration of catheterization and absence of a closed collection system has been positively correlated with catheter-associated UTIs.6
Prophylactic or concurrent administration of antibiotics may offer short-term protection against a UTI, but organisms that are resistant to the antibiotics often emerge. Therefore routine prophylactic antibiotics are not recommended; however, they could be considered in compromised patients with anticipated short-term urinary catheter use.4 Despite the morbidity and even mortality associated with urinary catheters, appropriate patient selection coupled with placement and maintenance protocols as described below resulted in a 10% incidence of nonresistant catheter-associated UTIs in a veterinary ICU. Most of these patients had urinary catheters placed for monitoring urine output and left in place for less than 4 days.4
During placement, stiff catheters or catheter stylets may cause physical trauma to the urethra or bladder. Appropriate lubrication, judicious use of force, and properly seated stylets (i.e., contained within the catheter) are indicated to prevent physical trauma. If a soft catheter is advanced too far into the bladder, it may fold back on itself and head back into the urethra. Measuring the length of the catheter before insertion can help prevent this complication. If it is encountered, topical anesthesia and, if needed, sedation will usually allow for its removal with steady traction; however, urethral trauma is a possibility. If this or manipulation of the catheter with stylets, flushing, and passing another catheter to force the advancing end back into the bladder are unsuccessful, or the catheter has actually become knotted, surgery is indicated.
Urinary catheters are made from a variety of materials that affect stiffness, urethral reactivity, and resistance to bacterial swarming and biofilm formation. Ideally a catheter is soft for patient comfort and to limit urethral trauma, has minimal reactivity, and has resistance to biofilm formation, decreasing the potential for catheter-associated UTI. The following materials are listed in order of decreasing urethral reactivity, increasing biofilm resistance and, hence, increasing order of suitability for long-term indwelling catheterization: plastic, red rubber, latex, siliconized elastomer or Teflon-coated latex, hydrogel-coated latex, and pure silicone. Diffusion from silicone balloons has been reported, resulting in balloon deflation.11