Urolithiasis can cause 15 percent to 21 percent of lower urinary tract problems.
EDITOR'S NOTE: SurgerySTAT is a collaborative column between the American College of Veterinary Surgeons (ACVS) and DVM Newsmagazine.
The Public Relations Committee of the ACVS would like to thank Dr. Tobias for her continued support of this column. She was one of the first contributors to SurgerySTAT and has continued to provide timely and informative articles.
Urolithiasis is reported to cause 15 percent to 21 percent of lower urinary tract problems in domestic cats. For male cats with irresolvable or recurrent urethral obstruction, perineal urethrostomy (PU) may be required, and any cystic calculi should be removed during the same anesthetic procedure.
These calculi can be removed via cystotomy or carefully through the new perineal stoma with a small urethroscope and retrieval instruments. Rather than using the more traditional perineal position — rear end tilted up, legs hanging over the end of the padded table and tail pulled forward — you can perform a PU procedure and cystotomy simultaneously with the cat in dorsal recumbency, reducing both surgery and anesthesia time and facilitating bladder flushing and stone retrieval.
For this alternative approach, first place a purse string suture in the anus, and prepare the appropriate areas for both abdominal and perineal surgery. Long-haired cats may need to be clipped along the dorsal aspects of the caudomedial thighs as well. Position the anesthetized patient on its back with each leg pulled forward. A positioning pillow, towels or a V-shaped table can be used to stabilize the cat. Gently pull the tail dorsally and cranially to one side, and complete the final surgical preparation of the area. The patient can then be draped so that the anus and any nonsterile areas are excluded from the surgical field.
In this position, the cat's hips will tip up slightly, providing excellent exposure to the scrotal and preputial area. The caudal abdominal wall will become somewhat concave and lax, but this will not interfere with the surgical approach for the cystotomy. At this point, you may elect to perform the cystotomy either before or after starting the PU.
The PU procedure is performed as usual in this position: Once the skin and subcutaneous tissues are incised, you can use a dry gauze sponge to wipe down the penile body, similar to stripping the spermatic cord in a castration. Transect the ventral penile ligament (between the pelvic symphysis and the penile body) and the ischiocavernosus and ischiourethralis muscles (located ventrolaterally). Palpate between the penile body and ischium (which is now cranial with the cat in dorsal recumbency) to verify that all ventral penile attachments have been freed.
With the cat in dorsal recumbency, the most superficial portion of the urethra will be facing upward and caudal. It may help to think about it this way: If the cat were in a perineal position, the penile urethra would be incised on the side closest to the anus. This is the same for cats in dorsal recumbency. Use tenotomy scissors to open the urethra (Photo 1) to the level of the bulbourethral glands so that the new stoma can accommodate a 5- or 8-Fr red rubber catheter or a closed pair of mosquito hemostats to the level of the box locks. Next, suture the urethral mucosa to the skin by using 4-0 absorbable monofilament in a continuous pattern. With the cystotomy still open, it is now possible to flush the bladder retrograde and antegrade to remove any stones before closing the bladder and abdomen.
Photo 1: The urethra is incised on its dorsal surface with tenotomy scissors.
Performing a PU in dorsal recumbency is not difficult; just think upside down!
Dr. Tobias is an ACVS board-certified surgeon and professor of small animal surgery at the University of Tennessee. She is the author of Manual of Small Animal Soft Tissue Surgery (Wiley-Blackwell, 2009) and the proud parent of two intelligent, attractive and well-behaved teenagers.
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