1. Indications for perineal urethrostomy
"urethrostomy" refers to the creation of a new, permanent opening in the urethra. The perineal area is the most common location for cat urethraostomy, which allows urine to be discharged from the normal anatomical area, which is larger than the diameter of the natural urethra opening. Selectable urethral (modified surgery) locations include the anterior, subpubic and transpelvic locations; however, these surgeries are only used in cases where the lesions are in the lateral urethra of the urethra of the bulbous urethra. All cat urethraostomy surgical locations are at the level of the urethra bulb or on the cephalic side, as the cat urethra diameter gradually tapers from the cephalic side to the caudal side. The average inner diameter of the anterior urethra and posterior prostate urethra is 2mm, the urethra at the urethra bulb gland is 1.3mm, and the end of the urethra is 0.7mm. Perineal urethostomy is most commonly used as part of the treatment of lower urinary tract disease (FLUTD) for cats, but can also be used to treat distal urethra trauma, stenosis, tumors, or congenital abnormalities. Perineal urethral ostomy may be required when other causes of urethral obstruction of FLUTD have been ruled out and recurrent urethral obstruction occurs despite proper management.
2. Surgical steps
1. Animals can be lying on their back or prone. Regardless of the position used, the animal's head is facing the anesthesia machine, and the perineal area is located at the other end of the operating table to minimize the distance between the animal and the doctor. The anus is sutured to minimize intraoperative fecal contamination. When lying on your back, you should place your legs gently on the side of your head and side to maximize exposure to the perineal area. When lying prone, the animal's hind limbs hang at the end of the table and the tail is gently placed above the back to maximize the exposure of the perineal area. The pads can be placed under the waist (when lying on your back) or under the abdomen (when lying on your prone) to support the animal and raise the perineal area.
Some animals need to undergo cystectomy at the same time. At this time, the supine position is recommended to avoid re-purposing or changing the animal position, but there is no significant difference in the incidence of surgical complications, surgery or anesthesia duration between different positions. 24 hours after the operation, the animals' perineal reflex activity was usually reduced and the incidence of spinal pain increased; but there was no difference in the incidence between different positions.
2. Shave the perineal area and prepare for surgery aseptic. If a cystectomy is planned at the same time, the animal can be placed on the back. Shave the abdomen and cover it in the same surgical area to avoid re-preservation. If possible, a catheter should be placed before starting the surgery to help identify the anatomical location of the lower urinary tract.
3. The scalpel makes an oval incision around the scrotum and foreskin. Male cats are castrated regularly. The distal end of the penis and/or foreskin can be grasped with Allis tissue forceps for easy dissection. Using a combination of sharp and blunt peeling, the penis is separated and stripped around to the position where the ischial cavernosal muscle is inserted. Monopolar and/or bipolar electrosurgery helps minimize bleeding during stripping.
4. Elevate the bilateral ischia cavernosal muscle from the ischia position. An electric knife or scalpel can help lift the start of the ischium cavernosal muscle and then fully elevate it using a periosteal stripper to minimize the risk of muscle bleeding. Release of the ischia cavernosal muscle can expose the ventral ligament of the penis, which is then transected at the insertion of the ventral and central portion of the penis. Continue to peel the penis from the subcutaneous tissues and sharply transversely cut the penis contractile muscle from the dorsal side of the penis (Figure 4). Continue to circumcision stripping until the urethral sphere gland is exposed. The urethral bulb glands are most easily seen and palpated on the back of the penis and are located on the side of the transverse ischial cavernosal muscle head.
5. Once the penis has been fully dissected, use a blade or tendon shear to cut the distal tip of the penis urethra to the urethra bulb. If the urethra cannot be incised far enough on the cephalo side, it will limit the size of the urethral ostomy site and increase the risk of stenosis. If the catheter cannot be placed before the operation due to obstruction, a catheter should be placed after the urethral incision to help guide the urethral stoma. Studies have shown that the diameter of the urethra stoma lumen decreased by an average of 0.15±0.09mm in 12 days after surgery, so the urethra stoma site should be large enough to withstand this expected stenosis that occurs during natural healing.
According to relevant research, urethral stoma that can easily accommodate 10Fr red rubber catheters has a 6% chance of obstructive stenosis, while urethral stoma that can accommodate 8Fr or 6Fr catheters has a 44% chance of obstructive stenosis in 100% chance of obstructive stenosis, respectively.
Sewing the urethral mucosa with the surrounding skin to form a urethral stoma. Any tension in the ostomy site should be avoided to minimize the risk of ostomy cracking and excessive stenosis. While non-absorbent sutures (e.g. nylon thread) and slow absorbable sutures (e.g. polydioxane), fast-absorbing sutures (e.g. polycapron 25) have been proven to be safe and do not require disassembly. Simple interrupted suture or horizontal mattress suture can be maintained in the dorsal range of the urethra or at 12 o'clock, so that the stoma can be maintained in the appropriate direction and avoid urethra misalignment. Placing a simple interrupted suture on both sides of the urethra stoma can gradually promote the formation of the opening and avoid tension on both sides. The 10Fr catheter can be left in situ during the ostomy process to ensure sufficient size.
Alternatively, the catheter may be placed intermittently during the ostomy process to find the appropriate diameter according to the surgeon's preference. You can use about 1 cm in length in the remaining penis urethra as a "laundry board". Sew this 1 cm penis mucosa to the surrounding skin using simple intermittent suture or simple continuous suture. This minimizes tension on the site and minimizes the probability of dermatitis caused by urine. After the "laundry board" is made, any remaining penile tissue must be ligated with circumferential ligation or percutaneous ligation and then removed. The final suture is placed at any corner of the distal range of the "laundry board" and the rest of the skin is closed regularly as a double layer (subcutaneous tissue and skin).
III. Results
Although 81.8% to 100% of cases have good and excellent long-term results, it should be remembered that perineal urethostomy is a rescue operation. Pet owners should be informed that perineal urethostomy can be used to treat FLUTD, but it does not cure the disease. About 54% of cats have short-term complications, and it was reported that on average 92±25 days after surgery, up to 20% of the affected animals developed urinary tract obstruction and urethral stenosis. Sterile cystitis and urinary tract infection are the most common short-term and long-term complications; however, other less common short-term complications in the literature include urinary incontinence, repeated obstruction, stenosis, extravasation of urine into subcutaneous perineal tissue, and local dermatitis. Mild long-term complications are not common; however, 13.5% to 39% of animals experience recurrent sterile cystitis and/or urinary tract infection, consistent with FLUTD. Although some of the diseased animals are subclinical, 77.2% of cats have bacterial urine within 12 to 24 months after perineal urethostomy.
In short, perineal urethostomy is a common treatment for lower urinary tract diseases in cats. Although the short-term complication rate of this surgery is quite high, its long-term success rate is high. It has been proven to improve the quality of life of affected cats.