CESAREAN SECTION

Cesarean section should be considered to manage dystocia when vaginal delivery is not possible (oversized fetus or failure of cervical dilation “ring womb”). Occasionally the technique can be used to terminate pregnancy in ewes that are suffering from pregnancy toxemia or ketosis.

RESTRAINT AND ANESTHESIA

Cesarean section can be performed via either a ventral abdominal paramedian or midline incision with the animal in dorsal recumbency or via a left flank (para-lumbar) incision with the animal in right lateral recumbency. Ventral midline or paramedian techniques are the preferred methods in sheep because the area does not have as much wool. This technique also provides easy access to both horns of the uterus, which is important because most ewes carry more than one fetus. Cesarean section can be performed in the field under lumbosacral epidural and local anesthesia, although use of lumbosacral epidural anesthesia has been associated with a risk of shock as a result of pooling of blood in the viscera. Epinephrine (0.02 mg/kg IM) may be administered intramuscularly as a prophylactic measure.

VENTRAL ABDOMINAL PARAMEDIAN APPROACH

After anesthesia, the ewe is restrained in a dorsal position in a cradle with her legs extended. The surgical area, which extends from the umbilicus to the base of the mammary gland and externally toward mid flank, is prepared by clipping the wool and aseptic preparation of the skin.

The 25-cm skin incision extends from the base of the udder toward the umbilicus. The incision should be made between the linea alba and subcutaneous abdominal vein, which is very prominent in late pregnancy. The approach is continued by using a combination of blunt and sharp dissection through subcutaneous tissues. The external rectus abdominis sheath is sharply incised, the rectus muscle bluntly separated along its fibers, and the internal rectus sheath tented, along with the peritoneum, and incised. The abdominal incision may be extended, if necessary, to allow easy exteriorization of the uterine horn. The operator should be careful not to incise the greater omentum, which lies deep into the peritoneum. The greater omentum and abdominal viscera are retracted cranially to expose the uterus. The uterine horn is grasped and exteriorized gently to avoid perforation (Figure 19.1-1). Hysterotomy is performed on the greater curvature of the uterine horn, starting at the upper third and extending towards the uterine bifurcation. Care should be taken to avoid incising through cotyledons, which prevents excessive bleeding. In most cases, ewes carry more than one fetus. Therefore a uterine incision large enough to allow a fetus in the other horn to be exteriorized through the same incision should be placed along the caudal aspect of the horn. If this is too difficult, a second hysterotomy may be performed on the other uterine horn. Depending upon the presentation, the fetuses are exteriorized by traction on the front legs and head or on the hind legs. During exteriorization of the fetus, the surgeon should be careful not to tear the uterine wall. Excess fetal fluid should be removed from the uterus. The placenta should be removed only if it is already detached. The uterus is sutured with an atraumatic needle with chromic catgut (No. 0 or 1-0) or similar synthetic absorbable suture in a continuous inverting suture pattern (Figure 19.1-2). If the uterus is compromised, a two-layer closure may be indicated. The sutured uterus should be checked for tears and lavaged copiously with sterile fluids before it is replaced into the abdominal cavity. Some authors suggest intrauterine and intraabdominal antibiotic therapy, but this is not usually necessary if the surgery is performed under aseptic or very clean conditions and systemic antibiotics are provided.

Figure 19.1-1 Paramedian ventral cesarean section: exteriorization of the uterus.

Figure 19.1-2 Cesarean section: closure of the uterus using a continuous inverting suture pattern.

The peritoneum and internal rectus sheath are sutured in a single layer with synthetic absorbable sutures in a continuous pattern. It is not necessary to include the peritoneum, it just depends on the surgeon’s preference. The rectus abdominis muscle may be closed to decrease dead space. The external rectus sheath is the “holding layer.” This should be closed carefully with an absorbable suture. Subcutaneous tissues and skin are closed routinely. The size of the suture varies with the weight of the animal. Some advocate the use of nonabsorbable sutures to decrease the risk of herniation and provide better security.

Postsurgical care includes oxytocin if the cervix is open and systemic antibiotics when indicated. The udder should be examined for milk let-down. During the surgery, there should be an assistant designated to attend immediately to the newborn and provide neonatal care.

Ventral Midline Approach

The ventral midline approach to cesarean section in small ruminants differs from the paramedian approach in that the skin and abdominal incisions are made directly over the linea alba. Incision of the skin starts at the base of the udder and is extended about 20 cm cranially towards the umbilicus. The subcutaneous tissue is incised to expose the linea alba, which should be evident as a small concave line. The abdominal wall is grasped with tissue forceps and tented, and a small incision is made on the linea alba (Figure 19.1-3). The incision is continued through the linea alba and peritoneum, with scissors guided by the operator’s index and middle fingers to avoid damaging the omentum or intestinal loops. Exteriorization of the uterus and delivery of fetuses is done in the same manner as described for the paramedian approach. The linea alba and peritoneum are sutured in an interrupted or continuous pattern with synthetic absorbable or nonabsorbable sutures (again, the choice is surgeon’s preference). Subcutaneous tissues and skin are closed routinely. Postsurgical care is similar to the paramedian technique.

Figure 19.1-3 Cesarean section by ventral approach in a goat; the internal rectus sheath and peritoneum are tented before they are incised.

OVARIECTOMY AND OVARIOHYSTERECTOMY

Exteriorization of the female reproductive organs is required for many reproductive techniques such as embryo collection and transfer, oocyte collection, uterine tube flushing, etc. An ovariectomy or ovariohysterectomy is usually performed for convenience to prevent sexual activity and eliminate pregnancy or to remove diseased organs (ovarian masses, chronic pyometra, uterine neoplasm, etc.).

An ovariectomy or ovariohysterectomy performed as an elective surgery should be done during the luteal phase of the cycle or during anoestrus so that the uterus is relaxed and bleeding problems that would be associated with a toned, well-vascularized uterus during estrus are prevented. Ovariectomy is easily performed on the anesthetized animal placed in dorsal recumbency. A small 6- to 8-cm incision is made in the ventral midline just cranial to the udder and continued into the abdominal cavity as described for cesarean section. The surgeon introduces two fingers into the abdominal cavity. The urinary bladder is identified, and the uterus is recognized in its dorsal aspect by following one of the horns to the uterine bifurcation. Once the uterine horn is grasped between the fingers, it is pulled towards the surgical incision. Both horns are exteriorized by gentle traction (Figure 19.1-4).

Figure 19.1-4 Ovariectomy/ovariohysterectomy: exteriorized uterine horns and ovaries.

For ovariectomy, the vascular pedicle of the ovary is isolated by passing forceps through the mesovarium and making sure to incorporate the ovarian artery and vein. A size “0” absorbable suture material is used to transfix the ovarian pedicle before transection.

For hysterectomy or ovariohysterectomy, the mesometrium and round ligament of each uterine horn are transected after ligation of small blood vessels. Transfixation ligatures are placed proximal to the cervix; the surgeon should make sure to include the large uterine vessels located on each side. The uterus is transected at the level of the body between two hemostatic forceps (Figure 19.1-5). A circumferential transfixation ligature of absorbable suture material is placed close to the cervix. If the remaining portion of the uterine body is large, it should be closed with an inverting suture pattern before replacing it in the abdomen. Removal of one horn or part of a uterine horn, a partial hysterectomy, is sometimes used in reproductive experimentation or for pathology confined to one side of the abdomen. The technique is similar to a total hysterectomy, although a flank approach would be possible. The vasculature supplying the ovary and horn on one side are ligated and transected. The remaining uterus is closed with an inverting pattern. Some advocate a two-layer uterine closure. For successful reproductive performance, it is essential the remaining ovary and uterine horn are normal.

Figure 19.1-5 Ovariectomy/ovariohysterectomy: transection of the uterus at the level of the uterine body between two hemostatic forceps.

SURGICAL EMBRYO COLLECTION

Embryo collection generally is done under general anesthesia. An area similar to that described for cesarean section is prepared for surgery and draped. A ventral midline incision is made just cranial to the base of the udder and extended for 6 to 8 cm towards the umbilicus. The linea alba is exposed by blunt dissection and then incised. The uterus and ovaries are located and exteriorized as described earlier. The ovaries are inspected for numbers of corpora lutea. During the procedure, the uterine horn is lavaged repeatedly with sterile saline, so it does not dry out. Each horn is flushed separately. A small incision is made at the base of the horn, and a Foley or Argyle silicon No. 10 catheter is introduced and maintained in place by inflating the cuff. The uterine horn is flushed from the uterotubal junction towards the base. Suturing the uterus is unnecessary if the endometrium is not prolapsing through the uterine incision. The linea alba is apposed carefully. Subcutaneous tissues and skin are closed routinely.

CASTRATION

Most small ruminants are castrated early at 2 to 3 weeks of age. Techniques used at this age are usually bloodless (see Bloodless Castration Techniques). Surgical castration of rams can be done under sedation/analgesia and local anesthesia. General anesthesia is recommended for adult goats or castrations performed because of testicular disease. Because of the large size of the testicular cord in these species, hemostasis is best accomplished with emasculators or by placing a transfixion ligature proximal to the pampiniform plexus. The distal third of the scrotal sac should be removed.

Young animals are usually sedated and restrained in a sitting position with the legs on the same side held together. The bottom third of the scrotal sac is excised, and the testes are removed by stripping while maintaining pressure on the inguinal ring (Figure 19.1-7).

Figure 19.1-7 Castration in a billy goat. The bottom third of the scrotum has been resected and the testes are stripped.

In the adult ram or buck, general anesthesia is recommended. The animal is placed either in lateral or dorsal recumbency. The scrotum and surrounding area are clipped and prepared for surgery. An incision is made on the lateral surface of the testis through the skin and tunica dartos. The testis and its envelopes are separated by blunt dissection. The vaginal tunic is excised to expose the testis. The cremaster muscle is separated from the vascular testicular cord. Each of these structures is ligated by transfixation suture. Some practitioners prefer to ligate the spermatic artery and vein separately. The cord is transected distal to the ligatures. Use of an emasculator can be indicated if the testes are normal size (Figure 19.1-8, A and B). The vaginal tunic is transected distally enough to allow the tunics to be closed over the remaining cord. An inverting suture pattern is used with an absorbable suture material. The tunica dartos muscle is closed over the wound with a simple continuous pattern. Excess skin may be trimmed. The subcutaneous tissues and longitudinal skin incision are closed. Bandaging the scrotum is recommended if bleeding is observed. Alternatively the incisions can be left to close by second intention if preferable or if the conditions are unsanitary.

Figure 19.1-8 Castration in an adult ram. A, Exteriorization of the testis; B, castration using an emasculator.

VASECTOMY

Vasectomy is a management technique in bucks and rams used to provide teaser animals and estrus synchronization through the “ram effect.” The surgery can be performed on rams after sedation and local anesthesia. General anesthesia is recommended for bucks because of their tendency to become agitated and vocal, which may disturb owners if surgery is done on the farm. Vasectomy has also been performed in rams after lumbosacral spinal analgesia. Rams can be restrained in the sitting position. Dorsal recumbency is the preferred position in goats.

The scrotal skin is prepared by clipping and surgical scrubbing. Surgical drapes are placed around and underneath the scrotum. A 3- to 4-cm vertical incision is made slightly medial on the cranial surface of the scrotal skin above the testicular cord. The spermatic cord is freed by blunt dissection and exteriorized with the help of hemostatic forceps (Figure 19.1-9). The vas deferens can be easily identified by palpation or visually by its white color and the presence of adjacent vein and artery. The vas deferens is exteriorized by using forceps or a spay hook through a small nick made in the vaginal tunic. A 3-cm portion of the vas deferens is removed after ligating each end (Figure 19.1-10, A and B). The vaginal tunic does not need to be sutured. The skin is sutured or stapled, and the same procedure is repeated on the other side. Excised tissue should be submitted for histological confirmation. Flushing and observing spermatozoa under the microscope is another quick way to confirm the excised tissue was in fact the vas deferens.

Figure 19.1-9 Vasectomy in a ram: exteriorization of the spermatic cord and identification of the vas deferens.

Figure 19.1-10 Vasectomy in a ram. A, Ligature and B, removal of a portion of the vas deferens.

EPIDIDYMECTOMY

The animal is prepared as for castration. A local block is provided by infusing 2% lidocaine in the ventral scrotal skin directly over the caudal epididymis. The testis should be held firmly within the scrotum to better visualize the prominent tail of the epididymis (Figure 19.1-11). The skin is incised (2.5 to 3 cm) on the ventral, posterior aspect of the scrotum (just above the caudal epididymis). Using blunt dissection, the veterinarian isolates the epididymis and holds it with an instrument or stay suture. The tail of the epididymis is transected after ligating each border with a nonabsorbable suture material. The skin is sutured by using a simple interrupted suture pattern. Semen should be collected at least three times before the male is used as a teaser.

Figure 19.1-11 Epididymectomy in a ram: the testis is held firmly within the scrotum and an incision is made over the prominent tail of the epididymis.

TRANSLOCATION OF THE PENIS

The objective of this surgery is to translocate the preputial opening laterally to render vaginal intromis-sion of the penis impossible during normal erection and mounting behavior. It is preferable to perform penile deviation under general anesthesia or deep sedation/analgesia. The animal is placed in dorsal recumbency, and the area from the umbilicus to the base of the scrotum is clipped, scrubbed, and draped for surgery. Special attention should be given to thoroughly flushing the prepuce with diluted iodophor. A skin incision is made about 1.5 to 2 cm around the preputial orifice and continued caudally towards the sigmoid flexure (Figure 19.1-12). The prepuce is entirely freed from the skin and surrounding tissue with blunt scissors dissection. Placing a catheter in the prepuce helps orient the surgeon. Once the desired length of the prepuce is completely freed, a site is selected on the abdominal wall at a 45° angle from the base of the penis to create the new preputial location. A circular skin flap is removed at this site (Figure 19.1-13). A closed long forceps is used to create a subcutaneous tunnel that extends from the circular skin incision to the base of the scrotum. The freed prepuce is placed in a sterile plastic sleeve, grasped with the forceps, inserted into the subcutaneous tunnel, and transferred to the new location. The surgeon must be sure that the organ does not twist. The preputial opening is sutured to the skin with synthetic nonabsorbable suture material in an interrupted simple or horizontal mattress pattern. The midline abdominal skin incision is closed routinely (Figure 19.1-14). Postoperative care includes systemic antibiotics. Ventral edema may develop in some animals and persist, generally for a few days. Urination should be verified, and the patient should be examined carefully if there is a large amount of persistent preputial edema. Skin sutures may be removed 10-to-14 days after surgery.

Figure 19.1-12 Translocation of the penis: skin incision around the preputial orifice continuing caudal towards the sigmoid flexure.

Figure 19.1-13 Translocation of the penis: removal of a circular flap of skin at the site where the preputial opening is to be relocated.

Figure 19.1-14 Translocation of the penis: skin suture and appearance after translocation of the organ.