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 muscles. Blunt dissection is used until the penis can be grasped. The retractor penis muscles can often be confused for the penis. The retractor penis muscles are pink, soft, and identifiable as two separate components versus the firm penis which is covered in white tunica albuginea [21]. Once the penis is grasped, firm traction is used to pull the penis caudodorsally toward the skin incision, while the retractor penis muscles can be reflected or sharply dissected. Caudal traction and dissection are performed until a 6‐cm segment of penis can be exteriorized without tension [21]. If substantial subcutaneous urine accumulation has occurred, the penis can separate from the preputial attachments, allowing exteriorization of the entire penis [4]. The dorsal penile artery and vein are identified and ligated approximately 5 cm distal to the dorsal aspect of the skin incision [21]. The penis is transected distal to this ligature. However, removal of the distal penis requires substantial dissection of the preputial attachments in cases with urethral obstruction but absence of urethral rupture. In these cases, the dorsal penile vasculature should remain intact and be blunted dissected and reflected from the penis.
Once the penis is transected, it is turned over 180° with the urethra now oriented dorsally. A horizontal mattress pattern using a monofilament non‐absorbable suture is made through the corpus cavernosum to secure the penile stump to the skin [4, 21]. Caution should be used to not incorporate the urethra; a retrograde polypropylene catheter may be placed to ensure inadvertent urethral involvement is avoided (Figure 20.8). To assist with prevention of urine scald, the stump should extend 2–3‐cm from the skin incision [21]. Spatulation of the urethra is optional (Figure 20.8). If performed, the urethra is incised from the distal aspect of the penile stump to the proximal aspect of the incision. The urethral mucosa and tunica albuginea are sutured to the skin using an absorbable 2–0 monofilament suture in a simple continuous or interrupted pattern. Spatulation of the urethra is performed to decrease the rapidity of urethral stricture formation [21]. The skin remaining proximal and distal to the urethrostomy site is closed in a routine fashion.
Figure 20.8 Perineal urethrostomy showing spatulation of the urethra and use of polypropylene catheter to assist with urethra location during suturing.
For individuals with a urethral rupture, subcutaneous skin incisions should be made as/if needed to drain any subcutaneous urine accumulation. Individuals with uroabdomen should have abdominal drainage of urine performed.
Potential complications from this procedure include postoperative hemorrhage from the corpus cavernosum of the penile stump and hemorrhage from repeated trauma to the penile stump. A securely fitted urethral catheter can be placed to put pressure on the corpus spongiosum to assist with hemorrhaging. Other common complications include urine scald, urethral stricture, and reobstruction with blood or calculi.
Other Procedures
Other treatment methods include laser lithotripsy, basket catheter urolith retrieval, and bladder marsupialization. Laser lithotripsy and basket catheter urolith retrieval will only be briefly mentioned here due to their limited use at referral institutions. Bladder marsupialization is only briefly mentioned due to the high complication rate in bovines.
Removal of urethroliths via laser lithotripsy has been reported in the literature for steers, goats, and pot‐bellied pigs [35, 36]. An endoscope and laser fiber can be passed retrograde or normograde through an ischial urethrotomy [35]. Once the urethrolith is identified, the fiber is fired in a pulsatile fashion on the stone until fragmented enough to clear the urethra.
Basket catherization involves inserting a basket catheter into the urethral orifice and manipulating the instrument past the urethrolith. The instrument is opened, the urethrolith is maneuvered within the basket, and the catheter is removed. One report states a 55% successful urethrolith removal in calves [37] and another report successfully treated a bull with basket catherization while maintaining fertility [38].
Bladder
