of Richard Hopper and Heath King.
Inguinal Hernia
Inguinal hernias can be classified as either congenital or acquired and direct or indirect. In mature bulls all inguinal hernias are considered acquired. Indirect hernias occur when bowel passes through an intact but dilated inguinal ring. This type of herniation occurs more frequently on the left side and rarely causes strangulation of bowel. Bulls with an indirect hernia will typically present clinically normal, other than swelling in the neck of the scrotum that gives the scrotum an hourglass appearance (Figure 18.7). Direct inguinal hernias occur through the inguinal ring, but disruption or tearing of the ring or vaginal tunic is present. Direct inguinal herniation is more likely to result in strangulation and obstruction of bowel with more pronounced and generalized scrotal swelling [17, 18].
Figure 18.7 Inguinal hernia in a bull. Note characteristic swelling confined to neck of scrotum.
The presence of an inguinal hernia can be confirmed with rectal palpation and scrotal ultrasound. Palpation should reveal a dilated or disrupted inguinal ring on the affected side and the presence of herniated bowel contained in the ring. Ultrasound of the neck of the scrotum can definitively confirm the presence of bowel. Bulls with intestinal obstruction will present with abdominal pain and distention and will require emergency surgery. Inguinal hernias in bulls that present clinically normal without any signs of obstruction can be managed with elective surgery [17, 18].
Less Common Causes
Bilateral scrotal enlargement with pitting edema of the hind limbs has been reported in young bulls secondary to Mycoplasma wenyonii infection (Figure 18.8). Swelling subsided in these bulls following treatment with oxytetracycline [19, 20]. Scrotal edema can be differentiated from other causes of scrotal enlargement by palpation and ultrasound.
Figure 18.8 Generalized edema of scrotal wall due to Mycoplasma weyenoii.
Primary testicular tumors are not common in bulls but unilateral or bilateral scrotal enlargement has been reported in bulls with mesothelioma [5, 12, 13, 19].
Unilateral Castration
Hemi‐ or unilateral castration should be considered in bulls with unilateral testicular disease. When one testicle is inflamed, the heat thus generated affects the contralateral testicle and the reversibility of degenerative change depends on the severity and duration of the insult [12]. Valuable animals with unilateral hematoceles, hyrdrocleles, orchitis, periorchitis, or testicular rupture may be able to resume breeding soundness with unilateral castration.
Although unilateral castration is not an emergency procedure, the prognosis for return to fertility improves if surgery is performed early in the disease process. Early intervention can reduce further insult to the contralateral testicle generated by inflammation, with less likelihood that the testicle will undergo irreversible degeneration. Most bulls will return to fertility following surgery if the remaining testicle is not severely compromised [10, 21, 22]. Compensatory hypertrophy in the normal testis should allow the bull to subsequently produce up to 75% of normal sperm capacity. Therefore, advise owners that restrictions may be necessary following surgery. Additionally, although a bull may be productive in a herd situation, a unilaterally castrated bull will not pass a standardized breeding soundness evaluation and is therefore ineligible for certain shows or sales [10].
In preparation for surgery the bull should be withheld from feed for 48 hours and water for 12 hours. Surgery is performed with the bull restrained in lateral recumbency under general anesthesia or heavy sedation and regional or local anesthesia. Regional anesthesia can be accomplished with the use of a pudendal nerve block, or local anesthetic can be injected into the neck of the scrotum and the spermatic cord. Antibiotics are administered prior to surgery and continued for at least five days post‐surgery. Non‐steroidal anti‐inflammatories should also be administered immediately prior to surgery. The scrotum is clipped and prepped for aseptic surgery [10, 23]. On the lateral aspect of the scrotum an elliptical skin incision is made approximately the length of the testicle, preserving the parietal vaginal tunic (Figure 18.9). The affected testicle within the parietal vaginal tunic is bluntly dissected away from the surrounding scrotal fascia (Figure 18.10). If the condition is chronic, variable amounts of fibrous tissue and adhesions of the parietal and visceral vaginal tunics may be encountered. At this point the decision is made whether an open or closed castration should be pursued. An open castration allows for more careful ligation of the vasculature but does expose the surgery site to potential contamination from the contents of the parietal tunic. A closed castration is typically performed by the author to limit contamination of the surgical site. Both techniques are described below.
Figure 18.9 Elliptical skin incision on lateral aspect of scrotum.
Source: Image courtesy of Richard Hopper and Heath King.
Figure 18.10 Testicle within parietal vaginal tunic bluntly dissected from scrotal fascia.
Source: Image courtesy of Richard Hopper and Heath King.
To perform an open castration, a vertical incision is made through the parietal tunic sufficiently long to remove the testis and exteriorize the testicle and spermatic cord (Figures 18.11). The spermatic artery, vein, and ductus deferens are isolated and double ligated with #0 chromic gut 8 cm proximal to the pampiniform plexus and transected between the two ligatures (Figure 18.12). The vaginal tunic is then transected and the external cremaster muscle is ligated and transected distal to the stump of the spermatic cord (Figure 18.13). The vaginal tunic is closed with an inverting pattern such as a Connell or Parker–Kerr using #0 chromic gut (Figure 18.14). To perform the closed castration, the spermatic cord is ligated proximal to the pampiniform plexus with a combination of one transfixing ligature and two circumferential Miller's knot ligatures using #4 polyglactin suture (Figure 18.15). The spermatic cord is then transected distal to the ligatures with emasculators. For either technique, the scrotal fascia and tunica dartos are closed with #0 or larger chromic gut in a simple continuous pattern being careful to eliminate dead space. The skin is then closed with non‐absorbable suture in a continuous
