Pilot study results of novel catheter design for managing feline urethral obstruction

Feline urethral obstruction remains a common and life-threatening emergency in veterinary practice. Most blockages occur at the distal penile urethra, where the lumen narrows to an average of 0.7 mm in diameter, in contrast to the wider proximal urethra (1.3–2.0 mm).¹ Traditional indwelling urinary catheters are sutured in place and extend into the bladder lumen. While effective at relieving obstruction, these designs may contribute to incomplete elimination of urinary crystals. Crystals tend to accumulate in the bladder neck during catheterization and often migrate into the urethra upon catheter removal, precipitating repeat obstruction.

Diagram comparing current catheters versus the MILA Tomcat Catheter. (Images courtesy of Mark Besancon, DVM)

Median section of feline penis, left lateral view. (Adapted from: Dyce KM, Sack WO, Wensing CJG. Textbook of Veterinary Anatomy. 2nd ed. Philadelphia, PA: Saunders; 1986.)

The MILA Tomcat Catheter was developed to address these shortcomings. Designed at a shorter 5cm length, and available in a 4Fr size, the catheter resides in the membranous/pelvic urethra rather than extending into the bladder.² This positioning allows urine suspension of struvite crystals, reduces bladder wall irritation, and facilitates more complete elimination. The present pilot study evaluates the effectiveness of the MILA Tomcat Catheter in comparison with currently available commercial open-ended catheters.⁵

Commercial catheter (top), MILA Tomcat Catheter (bottom).

Radiographic measurements of feline urethral length and anatomical landmarks used to determine the 5cm MILA Tomcat Catheter Length.

Materials and Methods

Three groups of male cats were evaluated over 48 hours:

1. Healthy Controls: Four non-diseased male cats with baseline urine samples collected via cystocentesis at day 0 and day 2.
2. MILA Tomcat Catheter Group: Obstructed male cats managed with the MILA 4 Fr catheter for 48 hours.
3. Commercial Catheter Group: Obstructed male cats managed with Argyle or Buster open-ended catheters for 48 hours.

Procedures

• Day 0: Relief of obstruction and baseline urine collection (submitted to Texas A&M Veterinary Medical Diagnostic Laboratory).
• Day 1: Medical management per clinician preference (fluids, antibiotics, analgesia, optional adjuncts).
• Day 2: Repeat urine collection, catheter removal.
  Samples were assessed for urine crystal concentration (intact struvite) at baseline and 48 hours.

Results

Control Group: Healthy male cats showed minimal baseline crystalluria with an average concentration of 0.74 crystals per high-power field (hpf), decreasing to 0.20 crystals/hpf at 48 hours, confirming expected physiologic clearance (Figure 1a and 1b).⁴

Figure 1a.

Figure 1b: Control Group Results.

MILA Catheter Group: Cats treated with the MILA Tomcat Catheter demonstrated a substantial reduction in crystalluria. Average baseline concentration was 13.86 crystals/hpf, falling to 2.12 crystals/hpf after 48 hours. Several cases demonstrated near-complete clearance, with no re-obstruction observed during hospitalization (Figure 2a and 2b).⁴

Figure 2a.

Figure 2b: MILA Tomcat Catheter Group Results. (Image courtesy of Besancon)

Commercial Catheter Group: Cats treated with Argyle or Buster catheters showed less effective crystal clearance. Average baseline concentration of 4.55 crystals/hpf rose to 10.4 crystals/hpf after 48 hours, reflecting persistent or worsening crystalluria. In several cases, recurrent obstruction occurred within hours of catheter removal (Figure 3a and 3b).⁴

Figure 3a.

Figure 3b: Commercial Catheter Group Results. (Image courtesy of Besancon)

Comparative Averages: When groups were compared, the MILA Catheter group showed markedly superior outcomes, with an average 85% reduction in urine crystal concentration compared to baseline, versus a +128% increase in the commercial catheter group (Figure 4a and 4b).

Figure 4a. (Image courtesy of Besancon)

Figure 4b: Comparative Average Crystal Concentrations by Group.

Discussion

These findings support the hypothesis that catheter design significantly impacts clinical outcomes in feline urethral obstruction. Traditional catheters extending into the bladder body do not effectively address crystals pooling in the bladder neck, leading to residual crystalluria and frequent re-blockage. The MILA Tomcat Catheter’s shorter length and placement within the proximal urethra leverage feline urethral anatomy to maximize clearance of suspended crystals.
Additional clinical advantages include:

• Reduced bladder wall trauma due to shorter indwelling length.
• Maintenance of urethral sphincter function, lowering risk of incontinence.
• Improved patient comfort with reduced irritation and inflammation.

The pilot study results align with anecdotal feedback from practitioners reporting fewer recurrent blockages and faster recovery times. Limitations include small sample size, variability in concurrent medical management, and potential dilutional effects in certain cases. Larger, multicenter trials with standardized protocols are recommended.

Conclusion

The MILA Tomcat Catheter represents a promising advancement in the management of feline urethral obstruction. By aligning with the anatomic advantages of the proximal urethra, it provides superior clearance of urinary crystals compared to Argyle and Buster catheters. These findings suggest a potential for improved patient outcomes, reduced recurrence, and a meaningful shift in how blocked tomcats are medically managed.

References

1. Johnston SA, Tobias KM. Veterinary Surgery: Small Animal. 2nd ed. Elsevier; 2018
2. Dyce KM, Sack WO, Wensing CJG. Textbook of Veterinary Anatomy. 2nd ed. Philadelphia, PA: Saunders; 1986
3. Fossum TW. Small Animal Surgery. 5th ed. Elsevier; 2019.
4. Texas A&M Veterinary Medical Diagnostic Laboratory. Urinalysis reports. 2024.
5. Besançon M. MILA Tomcat Catheter Pilot Study. Internal data. 2024.

Acknowledgments

The author gratefully acknowledges the collaboration of MILA International, Inc., participating veterinary clinics, and the Texas A&M Veterinary Medical Diagnostic Laboratory for analytical support. Special thanks to veterinary technicians and colleagues who assisted with patient monitoring, catheter placement, and sample collection.