Bovine Reproduction. Группа авторов
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breeding function.
Cystotomy
A cystotomy is ideally performed under general anesthesia with the individual in dorsal recumbency. Prior to creating the incision, the penis should be exteriorized and secured by clamping the apical ligament of the penis. A paramedian skin incision is performed lateral to the prepuce. The incision should be positioned relatively caudally to ensure adequate access and exteriorization of the bladder [27]. A paramedian or midline celiotomy can be performed. Once the urinary bladder is localized, stay sutures with 2–0 or 0 monofilament can be placed in the bladder to assist with the cystotomy. A routine cystotomy is performed with aspiration of urine. Removal of uroliths from the bladder trigone and proximal urethra can be assisted with the use of a surgical spoon, as well as copious lavage and aspiration of sterile saline. An 8‐ to 10‐French polypropylene catheter is then passed in both a normograde and retrograde direction. Hydropulsion is performed with saline and may relieve the urethral obstruction. However, excessive force and effort are contraindicated due to the risk of damaging the urothelium or causing a urethral rupture. The urethra is considered free of calculi when saline can easily be flushed normograde and retrograde [27]. If urethral patency is not obtained, a tube cystostomy should be performed. The bladder is closed with 2–0 or 3–0 monofilament suture in a single‐ or double‐layer inverting suture pattern. In cases of bladder rupture, the defect should be repaired and/or any necrotic tissue removed. In cases of bladder rupture, aspiration and lavage of the abdomen should be performed. The celiotomy, subcutaneous tissues, and skin should be closed in a routine fashion. Disadvantages of this procedure include the expense and duration of the procedure, potential for urethral rupture, and extensive postoperative urethral swelling resulting in significant stranguria or postoperative obstruction.
Ischial Urethrostomy
Ischial urethrostomy is a viable treatment option for feedlot steers (≥318 kg) and breeding bulls [4, 32]. This procedure is performed under standing epidural anesthesia. The perineal region from the anus to the base of the scrotum is aseptically prepared. A 10‐cm midline skin incision is performed starting over the ischial arch approximately 5 cm ventral to the anus [4]. The dense layer of fascia between the skin and retractor penis muscle is incised to expose the retractor penis muscle [4]. Blunt dissection between the retractor penis muscles reveals the bulbospongiosus muscle [4]. The urethrotomy incision is made through the bulbospongiosus muscle or just distal to its attachment [33]. Excessive hemorrhage is common during this procedure if the urethra incision is off midline and the corpus spongiosum is nicked. A 20‐ to 28‐French Foley catheter is advanced into the bladder. Entrance into the bladder can be assisted with the use of a rigid stylet or curved hemostats to direct the tip over the ischial arch [4]. The Foley balloon is distended with saline and retracted until it is seated into the trigone of the bladder and sutured in place where it exits the skin. A one‐way valve utilizing the fingertip of a glove with a slit should be taped onto the external end of the Foley catheter to prevent air aspiration into the bladder and minimize bacterial contamination. Ideally, impervious plastic should be adhered to the skin just ventral to the anus to prevent fecal contamination of the surgical site. For breeding bulls in which urethral patency is desired, a sterile bandage over the incision with stay sutures and surgical towels is recommended (Figure 20.7).
Figure 20.7 Placement of a plastic or rubber (source‐ automobile inner tube) strip sutured to the perineum dorsal to the surgery site is recommended.
Source: Image courtesy Dwight Wolfe and Misty Edmondson.
For feedlot steers, the catheter can remain in place until desired slaughter weight is reached or the uremia is resolved (~30 days) [32]. Additionally, this procedure can be used when a previous lower perineal urethrostomy site has strictured or reobstructed. In general, the prognosis is greatly reduced for individuals with bladder rupture. However, this technique allows the bladder to remain empty and heal by second intention.
This technique can be a good option of urinary diversion for breeding bulls (without urethral rupture) because the urethral diameter is larger in this region, thus decreasing the risk of urethral stricture. If urethral patency is immediately obtained after the procedure, the Foley catheter can be removed and 3 mm polyethylene tubing is inserted through the urethrotomy incision into the bladder and exiting the distal urethra [4]. A primary urethral closure should be performed and the catheter exiting the distal urethra should be sutured to the ventral abdomen with a Chinese finger cuff ligature [4]. If urethra patency is not immediately obtained, the Foley catheter should remain in place to allow for relief of urethral spasm and swelling. If the obstruction fails to resolve after three to five days, alternative methods of calculi removal should be implemented. Other methods include retrograde catherization and hydropulsion, urethroscopy and possible basket retrieval, chemolysis (Walpole's solution, acetic acid, or hemiacidrin) for phosphatic uroliths (struvite or apatite), or urethrotomy. Long‐term outcome and complication rates for breeding bulls have not been evaluated. However, there is one report of a goat with a strictured perineal urethrostomy being reversed with a buccal mucosal graft urethroplasty successfully [34].
Urethrotomy
Urethrotomy can remove individual uroliths or uroliths unamenable to dissolution with urinary acidification. This procedure is most utilized in breeding bulls since the urethra is not altered from its natural course. Additionally, this procedure is only a via option for individuals without urethral rupture. To perform the procedure, the urolith must be identified via palpation, catherization, or ultrasound. Depending on the location of the urolith, this can be performed under epidural anesthesia, general anesthesia, or sedation with casting harnesses. The individual is placed in dorsal recumbency, the urolith is located, and 2% lidocaine is infiltrated over the site of obstruction. The penis is grasped and a skin incision is performed. The penis is then exteriorized through the skin incision. A towel clamp or tissue forceps can be used to crush the stone and allow the fragments passage [4]. However, if this fails after two attempts, a urethrotomy should be performed directly over the urolith and the urolith(s) should be removed [4]. Some authors recommend bidirectional urethral flushing to ensure patency [21]. Urethral closure is then performed with 3–0 or 4–0 monofilament suture in a simple interrupted pattern. Suturing over a urethral catheter facilitates closure. The subcutaneous tissues and skin are closed in a routine fashion. Concurrent treatment with a urinary diversion technique such as tube cystostomy or ischial urethrostomy is ideal to allow adequate healing of the urethrotomy site. Urinary diversion allows resolution of inflammation at the urethra and thus prevents the risk of dehiscence or fistulation at the urethrotomy site. Alternatively, urethral catheterization can be used 24–48 hours postoperatively. Complication of urethrotomy includes urethral dehiscence and stricture especially if the urethral mucosa is devitalized. Peripenile adhesion is also a common complication that ultimate prevents a bull from reaching an erection and extension for breeding.
Perineal Urethrostomy
A perineal urethrostomy with penile amputation is a common salvage technique used for lightweight feedlot steers. This procedure is not intended for breeding individuals. Urethral stricture is an eventual complication of this technique; therefore it should be reserved for feedlot steers to resolve their azotemia and finish growth prior to slaughter. This technique is relatively quick and can easily be performed in the field.
It can be performed with the individual restrained in a chute under epidural anesthesia or in dorsal recumbency with heavy sedation and epidural anesthesia. The perineal area from the anus to the scrotum is clipped and aseptically prepped. A 10‐ to 15‐cm midline incision is made immediately caudal to the scrotum. The incision is extended through the subcutaneous tissues and semitendinosus