Urethral Catheterization of the Obstructed Male Cat

Urethral obstruction is a common veterinary emergency for the male feline patient. Untreated, urethral obstruction leads to azotemia (as uremic toxins are not expelled from the body), life-threatening hyperkalemia, bladder necrosis and/or uroabdomen, and, ultimately, death.¹ Emergency treatment includes fluids for renal perfusion and systemic shock, cardioprotectants, multimodal therapy to treat hyperkalemia, and quick urethral catheterization to restore normal urine flow.² Although protocols exist for managing urethral obstruction without urethral catheterization, risks are severe and standard medical management options continue to rely on successful catheterization.³ A skilled veterinary nurse should be able to perform catheterization quickly and efficiently, according to each state’s Veterinary Practice Act and under the supervision of a licensed veterinarian, while minimizing patient risks. This article provides a step-by-step approach to the procedure, which is also demonstrated in VIDEO 1.

Step 1: Gather Supplies

Supplies for urethral catheterization vary widely based on clinic inventory and personal preference. However, cats that are difficult to unblock may require a broad selection of catheter options and techniques.

Catheter options are as follows (FIGURE 1):

• Red rubber catheters, 3.5 and 5 Fr (e.g., Covidien)
• Semirigid polypropylene catheter (e.g., Cardinal Argyle Tomcat)
• Soft polytetrafluoroethylene/polyurethane catheter (e.g., Mila Tomcat, SurgiVet Slippery Sam Tomcat)
• Stainless steel olive-tip urethral catheter (e.g., Jorgensen KatKath Tomcat)
• 22- and 20-G IV catheters

FIGURE 1. Selection of urinary catheters.

Sterile supplies needed are as follows (FIGURE 2):

• Lubricant packets
• Sterile gloves
• Cutting needle
• 3-0 suture material
• Urinary collection bag
• Supplies for hydropulsion
  • Sterile bladder flush (0.9% saline or sterile water) in 12- or 20-mL syringes (2 to 3 syringes)
  • Optional: Luer Lock adapter (e.g., SurgiVet Little Herbert)

FIGURE 2. Example of sterile supplies (not inclusive) used for unblocking.

After the supplies are ready, set up the procedure table with traditional monitoring equipment and flow-by oxygen (FIGURE 3). All patients should be monitored to the extent available, which should minimally include electrocardiography and blood pressure monitoring. A small V-shaped trough may be helpful for positioning the patient; however, similar positioning may be accomplished with sandbags or rolled towels.

FIGURE 3. Urinary obstruction patient sedated with monitoring.

Step 2: Sedate the Patient

Most patients will require sedation, with the exception of moribund patients, for which opioids alone may suffice. For alert patients, sedation protocols vary according to patient stability. Critical patients typically tolerate unblocking with neuroleptanalgesia, which combines the use of an opioid and benzodiazepine (e.g., methadone and midazolam). More stable patients typically require heavier sedation. Fluid therapy should be administered before, during, and after the procedure. TABLE 1 reviews common drug combinations and dosages.

Some practitioners prefer to use inhalation anesthesia; however, no benefit has been shown for inhalation anesthesia compared with sedation.⁴ In the author’s experience, use of a sacrococcygeal block renders inhalation anesthesia unnecessary. However, if inhalation anesthesia is preferred due to patient stability, the patient should undergo endotracheal intubation and full anesthesia monitoring.

Step 3: Administer a Sacrococcygeal Block and Prepare the Patient

Patient preparation first involves performing a sacrococcygeal block for patient comfort and improved muscle relaxation for unblocking.⁵ Information on how to perform a sacrococcygeal block can be found at go.navc.com/3AIR3Gx.

The most common positioning for urethral catheterization is in dorsal recumbency, using a V-shaped trough, sandbags, or rolled towels for positioning. Next, the hind limbs should be brought cranially and secured (FIGURE 4), which exposes the prepuce and allows for straightening of the urethra during catheterization. After the patient is positioned, shave the perineal region and aseptically scrub the area, including the prepuce. Before the final scrub, gently massage/roll the prepuce; for a few patients blocked by small mucous plugs, this gentle act combined with the muscle relaxation of sedation may be enough to unblock them.

FIGURE 4. Preparation of the perineal area.

Step 4: Choose a Catheter

The choice of first catheter for unblocking is based on personal preference. The author prefers to attempt initial unblocking with a red rubber catheter. The benefits of exclusively using a red rubber catheter are a less traumatic approach to the urethra, subsequent decreased likelihood of urethral damage, and the ability to leave the catheter in place after unblocking. However, pliability and fenestrations of red rubber catheters can make hydropulsion more difficult.

Some practitioners prefer to use a more rigid catheter for initial unblocking and later replace it with a more pliable catheter to leave indwelling. The benefits of a Mila Tomcat catheter are similar to those of a red rubber catheter, in that it is soft and pliable and can be left in place after unblocking; however, its biggest benefit is that it contains a rigid guide wire and is open-ended (the hole is at the tip of the catheter as opposed to on the sides), thus allowing for easier hydropulsion. The disadvantages of a Mila Tomcat catheter are that it can become dislodged and may be more prone to kinking than a red rubber catheter.

Indwelling longevity can be increased by additional catheter security (e.g., by placing tape around the suture adapter, using an additional finger trap). For very distal blockages, steel olive-tip catheters can be used and are less likely than semirigid catheters to cause a urethral tear. IV catheters (with stylet removed) may also be used; however, IV catheters are very pliable and can be difficult to use. The benefit is that every clinic will have a supply of IV catheters available.

Step 5: Place the Catheter

The difficulty of clearing the urethral obstruction (unblocking) will vary by patient. Some patients may be easily unblocked; others may take several attempts and a combination of techniques. Some practitioners prefer to rely on force and the stiffness of the catheter to unblock the urethra. Doing so is more likely to cause urethral damage and result in a urethral tear but may lessen the time to successful unblocking.⁶

Step 6: Use Hydropulsion

Use of hydropulsion (aggressive lavage of the urethra with sterile water or saline) is an efficient unblocking technique. This method may be slower and require more patience, but ultimately is safer and less traumatic on the urethra. The hydropulsion must be forceful. Gentle hydropulsion will not produce sufficient pressure to dislodge urethral material; thus, use of 12- or 20-mL syringes, as opposed to 3- or 6-mL syringes, is recommended. It is common for so much force to be applied during hydropulsion that connections between the syringe and catheter disconnect.

Regardless of catheter choice, the technique remains the same. The penis is first extruded by placing a finger and thumb above and below the penis (FIGURE 5). The tip of the catheter is lubricated and placed into the tip of the penis, and the prepuce is then pulled caudally (FIGURE 6); be sure the catheter does not become dislodged from the urethra. Pulling the prepuce caudally straightens the bend in the urethra immediately proximal to the penis, allowing easier passage of the catheter. After the tip of the catheter is in the penis and is pulled caudally, use hydropulsion while attempting to push the catheter up the urethra. Hold the end of the prepuce snugly to prevent the hydropulsion from escaping backwards. It is helpful to have an assistant perform the hydropulsion while the practitioner holds the prepuce and attempts to pass the catheter. Several attempts may be required before the catheter can be passed. In difficult cases, the sterile lavage solution may be mixed with a small amount of sterile lubricant in an effort to lubricate the urethra. For very difficult cases, attempt this step multiple times. Patience is key; too much force during rigid catheter insertion can lead to urethral trauma.

FIGURE 5. Penis extrusion.

FIGURE 6. Pulling the prepuce caudally to straighten the urethra.

Step 7: Secure the Catheter

The indwelling catheter can be secured after it has reached just beyond the trigone of the bladder. Termination can be determined via ultrasonography (FIGURE 7) and radiography (FIGURE 8). Catheter securement and adjustment will vary according to catheter choice. Jorgensen KatKath catheters have a swiveling securement device to help prevent kinking. Mila Tomcat catheters have suturing sheaths. Red rubber catheters can be secured with stay sutures on either side of the prepuce (not on the prepuce) (FIGURE 9), and then sutured to Elasticon tape around the catheter. Use of stay sutures enables less painful catheter replacement in the event of catheter slippage because the sutures may remain in place. An additional finger-trap suture may be placed at the caudal end of the tape to prevent slippage. The catheter or urinary collection set can then be secured to the tail with self-adhesive wrap and catheter tape (FIGURE 10). Leave adequate length between the penis and the tail securement to prevent pulling on the penis during the patient’s natural movement.

FIGURE 7. Ultrasonography image showing catheter termination (arrow).

FIGURE 8. Radiograph image showing catheter termination (arrow).

FIGURE 9. Stay suture placement.

FIGURE 10. Urinary catheter securement.

Complications

Although uncommon, urethral tears can result from difficult catheterization. Urethral tears cause urine extravasation and urethral strictures and may even prevent urethral catheterization, thereby leading to ongoing obstruction and decreased chances of survival to discharge.⁷ Factors that contribute to urethral tears are friable tissue, dehydration, and a history of urethral catheterization.⁸ Urethral tears can be difficult to recognize but are usually noted as an inability to pass a catheter, catheter curling or kinking in the subcutaneous periurethral space, and even intra-abdominal placement of a catheter. If the catheter can be passed but no urine is obtained, concerns should rise for urethral tearing. For very distal tears, surgical intervention via perineal urethrostomy may resolve the complication. For more proximal tears, normograde passage of the urinary catheter may be needed, which is difficult in patients that are still obstructed. Retrograde passage can still be attempted using contrast cystourethrography. After the urinary catheter is in place, it is typically kept indwelling for 1 to 2 weeks to allow the urethra time to heal.⁷

Alternative Procedure

If a catheter cannot be passed, decompressive cystocentesis may be performed to alleviate renal back pressure and ease patient comfort. Decompressive cystocentesis involves emptying the bladder via cystocentesis. Although repeated bladder puncture has been associated with development of hemoabdomen or uroabdomen, single decompressive cystocentesis has not been associated with bladder rupture when followed by urethral catheterization and in-hospital management.⁹ Decompressive cystocentesis can be performed while planning referral to a specialty hospital, if necessary.

Summary

Urethral catheterization of the blocked male cat can be accomplished by a trained veterinary nurse. A trained veterinary nurse should know the techniques used for unblocking and be aware of and able to recognize potential complications.