Urethral catheterization is the most frequent retrograde manipulation performed on the urinary tract. Catheters are placed to drain the bladder during and after surgical procedures requiring anesthetics, to assess urinary output in critically ill patients, to collect reliable urine specimens, for urodynamic evaluation, for radiographic studies (eg, cystograms), and to assess residual urine. Such catheters can be left indwelling with a self-retaining balloon, as is done with a Foley catheter. An in-and-out procedure to drain a bladder does not require a self-retaining device. Adequate lubrication and sufficient frequency to keep the bladder at reasonable volumes are critical and must be emphasized to the patient performing self-intermittent catheterization; sterility is secondary. In contrast, when a catheter is left indwelling it is important to use sterile technique.
Technique of Catheterization
The penis should be positioned pointing toward the umbilicus to decrease the acute angulation as the catheter traverses the bulbar urethra. On most occasions, the catheter passes without difficulty. When difficulties arise, a careful history relating to previous urologic manipulations is critical. Strictures are not infrequent and can occur after endourologic surgery. Urethral strictures can be found from the meatus to the bladder neck. History of a straddle injury may suggest a bulbar urethral stricture. Adequate lubrication injected into the urethra and instruction of the patient to relax his pelvic floor eases the passage beyond the striated rhabdosphincter. A large-caliber catheter of approximately 18F should be used. Narrow, stiff, small catheters have greater potential of creating false passages and possible perforation. Coudé (elbowed) tipped catheters frequently help negotiate a high bladder neck, as seen with benign prostatic hyperplasia. With self-retaining Foley catheters, complete advancement until the elbowed valve is at the meatus or until the urine returns is important. Inflating the balloon prematurely (while it is in the urethra) may result in severe pain and possible urethral rupture. This must be emphasized to ancillary nursing personnel dealing with patients who are unable to communicate effectively, because under such circumstances, urethral rupture may present only after severe infection is evident.
It may be difficult to identify the meatus, especially in patients with obesity or hypospadias. Lateral and outward traction on the labia and the use of the posterior bill of a vaginal speculum may be helpful. With adequate instruction and a mirror to visualize the meatus, women can learn to catheterize themselves. For repeat catheterizations, a finger inserted into the vagina can help to guide the catheter.
Difficult Placement and Removal
When a urethral catheter cannot be placed, filiforms and followers may be used. The narrow filiform leaders are stiff and can puncture the urethra if too much force is used. Thus, gentle advancement should stop when resistance is encountered, and the initial filiform should be left in place. A second and third filiform, and possibly additional ones, should be placed next to the previously placed catheters in hope that the existing catheter occupies false passages or tortuous kinks. Eventually, one of the filiforms should pass and coil into the bladder. A screw adaptor at the end of the filiform can be used to connect progressively larger followers to dilate the narrowed urethra. After adequate dilatation, an open-tipped Council catheter can be placed over the filiform and into the bladder. If a problem or undue resistance is encountered at any stage, the procedure should be aborted and a suprapubic cystostomy should be placed to achieve adequate drainage.
Indwelling catheters should be secured to a closed gravity drainage system. Drainage tubing connected to catheters should be positioned to limit dependent curls and thereby limit airlocks that will frequently limit bladder evacuation. For long-term requirements in males, the catheter should be secured to the abdominal wall to decrease urethral traction pressure and potential stricture formation. Meatal care is needed to ensure adequate egress of urethral secretions.
Difficulty is much less common when removing indwelling urethral catheters. Here, the retention balloon is deflated prior to removal. On occasion, the balloon may not deflate. Inspection of the valve frequently reveals a problem. One may cut proximal to the valve in hopes of evacuating the balloon contents, but this is not always successful. Other options include transperineal or transabdominal balloon puncture (best with ultrasonographic guidance), or injection of an organic agent such as ether through the balloon port (with a full bladder to prevent chemical cystitis) to dissolve the balloon wall. If the catheter cannot be advanced, retracted, or twisted, one should suspect an unintended suture that could have been placed during prior surgery; such sutures can be cut via the small pediatric endoscope placed along the Foley catheter. Another complication of urethral catheters is incrustation, especially when a catheter is left indwelling for a long time.
Catheters differ in size, shape, type of material, number of lumens, and type of retaining mechanism (Figure 11–1). Standard sizes of external catheter diameters and most endoscopic instruments are given according to Charriére's French scale (units of 0.33 mm = 1 French [F] or 1 Charriére [Charr]). Thus, 3F equals 1 mm in diameter and 30F equals 10 mm in diameter.
Urethral catheters, metal stylet, catheter, and guidewire techniques for catheter insertion.
The choice of catheter size is dependent on the patient and the purpose. Large-caliber catheters are used to evacuate blood clots or other debris. Other catheters are used to stabilize grafts after open urethroplasties, for stenting after endoscopic incisions of strictures, for support of external ureteral catheters, or to assess urinary output. Triple-lumen catheters (one port for balloon inflation and deflation, and one each for inflow and outflow) have smaller lumens than two-way catheters. Other catheter variables include balloon size and construction materials; smaller catheters typically have smaller balloons. Large balloons (eg, 30 mL) can be inflated well over 50 mL to decrease the likelihood of the balloon migrating into the prostatic fossa, especially after transurethral resection of the prostate (TURP). They can be used as traction devices against the bladder neck to control hemorrhage from the prostatic fossa after TURP.
The rigidity of the catheter, the ratio between internal and external diameters, and the biocompatibility depend on the material with which the catheter is made. The standard latex catheter can result in severe reactions in patients with latex allergies, most commonly seen in those with myelomeningoceles. Silicone varieties are good alternatives in such situations. Mucosal irritation is decreased when catheters with a low coefficient of friction are used. Hydromers are placed onto catheters to allow for transient coating, creating an interface between biologic tissues and the foreign catheter; this interface lasts for approximately 5 days. Permanent hydrogel coatings last the life of the catheter. Decreasing the coefficient of friction of these catheters brings about a decrease in mucosal irritation and better biocompatibility. Catheters with a longer lasting interface result in decreased incrustation.