By William E. Schultz, DVM For The Education Center
Originally Published In Veterinary Practice News, December 2018 – Download as a PDF
In our clinic, urinary tract obstruction in cats has been a common problem until recently. Before that, many late-night emergency calls were spent sedating and unblocking cats. After several attempts at catheterization, the outcome in many cases was surgical intervention. Over the years, several cat food companies have responded to the problem by changing formulations in the food to reduce the occurrence of crystalluria. The response in cats has been significant to the point that many veterinarians in practice have never done a perineal urethrostomy procedure. Although not as often as in the past, cats still develop urinary obstruction and urethrostomy is necessary. During conventional scalpel procedure, visualization may be compromised due to hemorrhage from several areas. Therefore, in our clinic, we utilize our Aesculight CO2 laser (by Aesculight®, Bothell, Wash.) for this procedure.
Before surgery, the cat should have a complete urinalysis performed and diet should be changed to a urinary care diet for life. Culture and sensitivity tests are done if infection is present. Blood chemistry is performed preoperatively with fluids, pain medications, and antibiotics given for surgery.
An important factor intraoperatively is to dissect the attachments of the penis and associated structures from pelvic attachments, allowing for the entire structure to be moved caudally. The caudal aspect of the penis and associated structures allows the urethra to be opened to the proper diameter for a successful procedure. CO2 laser surgery has completely changed visibility during dissection and the success of the procedure.
Prepping for the procedure
For this procedure, a tipless Aesculight handpiece with a 0.25-mm focal spot size is typically used (shown in Figures 1 and 5). The laser is set at 15 watts SuperPulse for the initial incision of the skin.
The cat is positioned at the end of the surgery table in sternal recumbency with the tail tied cranially and the feet extending off the end of the table, exposing the perineum. Surgical prep with chloroxylenol is completed before surgery.
The sheath and scrotum are removed completely (Figures 1 and 2), with the tissues surrounding the penis dissected away from the penile shaft. The retractor penis muscle is also dissected and removed (Figure 6).
The laser is then set to 10 watts in the continuous wave mode for the dissection of the bulbourethral gland from the ischium (Figures 4 and 5). The laser is directed at the surface of the ischium to prevent laceration of the bulbourethral gland. The attachment of the gland is completely removed from the ischium bilaterally. During surgery with a scalpel or scissors, the lack of coagulation often leads to hemorrhage as the bulbourethral gland is removed from the attachment to the ischium. The bleeding is difficult to control and will cause poor visualization of the surgical field.
The third area of attachment is centrally to the pelvic floor with a frenulum that needs to be incised (Figure 3). With the removal of the bulbourethral glands and the ventral frenulum, the entire penis and accessory organs are able to shift caudally, thus allowing the proper opening of the penile urethra. Digital palpation and movement caudally of the penis and attached organs will verify complete dissection of the bulbourethral glands and the ventral frenulum.
The penis is then catheterized with a tomcat catheter (Figures 7 to 9). In some cases, the scar tissue may be sufficient that the catheter cannot be inserted in the urethral opening. In this surgery, the urethra was opened dorsally with iris scissors enough for the easy insertion of the catheter. With the catheter in place, the iris scissors are used to open the penile urethra until the opening is wide enough for the hinge on a mosquito forcep to insert without pressure (Figures 9 and 10). The incision is advanced incrementally until the desired width of the lumen is achieved. This opening is enlarged until about 5 mm in diameter. The catheter may be removed during the final opening of the penile urethra, allowing for better visualization of the lumen. This stage of the surgery is usually characterized by mild hemorrhage due to the highly vascular tissues incised. The hemorrhage is easily controlled with gauze sponges.
The distal third of the penis is clamped transversely with mosquito forceps and the distal aspect is removed with the laser (Figure 12). The forceps remain during initial suture placement to help maintain tension on the penis for visualization.
Sutures and postop
3-0 Monocryl was utilized for this procedure. The use of a braided suture material is not recommended due to tissue friction. Monofilament suture material has less friction and proper tissue apposition is more likely. The important sutures are the dorsal central 3 sutures (Figures 11 and 13). The first suture is placed in the central area from the lumen of the urethra to the skin margin of the incision. The next two are placed at 11:00 and 1:00 o’clock position. These sutures assure patency of the urethral opening. The hemostat is then removed and sutures are placed from the distal aspect of the penis to the ventral aspect of the incision (Figure 13). The interrupted sutures are then placed progressively from the open urethra to the skin (Figures 14 and 15).
When the procedure is complete, the surgeon should be able to easily insert the hemostat to the level of the hinge. A catheter is then sutured in place overnight and the patient should wear an Elizabethan collar until suture removal two weeks after urethrostomy. Many cats will allow sutures to be removed without sedation, but it is important to evaluate the surgical site postop and sedation may be necessary in fractious cats.
Urethrostomy was common procedure 20 years ago. Since then, food companies responded by changing formulations in feline diets to dramatically decrease or completely stop the formation of urinary crystals that lead to the urethral obstruction. Yet, with the changes in feline food formulas, the occurrence of cats presenting at our clinic has declined from weekly to several times a year. Because the foods are not 100% effective in all cats the procedure is still needed for the cats that block several times or those that have extensive scar tissue as a result of urinary tract blockage. CO2 laser is highly beneficial for the surgery due to its excellent hemostatic ability, which assures good intraoperative visualization.
About the Author
William E. Schultz, DVM, graduated from Michigan State University College of Veterinary Medicine in 1973 and opened his companion animal practice in the fall of 1974. The practice includes general medicine with special interest in reproduction and orthopedic surgery. Fresh, chilled, and frozen semen breedings with semen collection, storage, and shipment are also available. Digital radiology includes Orthopedic Foundation for Animals (OFA) and PennHip procedures. Dr. Schultz has been a board member on the Synbiotics Reproductive Advisory Panel, MOFA Advisory Panel, the Society for Theriogenology, and the Theriogenology Foundation. He has a special interest in canine reproduction and laser surgery and has had speaking engagements at veterinary conferences, veterinary associations, and national specialties. In addition, he was awarded the Veterinary Practice of Excellence award by the Society for Theriogenology in 2014. Dr. Schultz has also published articles related to canine reproduction and soft tissue laser surgery, including a chapter on perineal and urogenital laser surgery in a new textbook.
This Education Center article was underwritten by Aesculight of Bothell, Wash., the manufacturer of the only American-made CO2 laser.