Blood Loss

The blood volume of the rabbit is reported to be approximately 57 mL/kg body weight.^16,18 Most mammalian species experience a drop in arterial pressure and cardiac output with moderate blood loss. Loss of 15% to 20% of the total blood volume causes massive cholinergic release, with tachycardia and intense arterial constriction; thus blood is redistributed away from the gut and skin. In a 4-kg rabbit, this amounts to 34 to 45 mL of blood. An acute blood loss of 20% to 30% of total blood volume, or 45 to 68 mL in a 4-kg rabbit, is critical.

Pain and Analgesics

The very nature of rabbits is the foremost argument for the use of analgesics. A rabbit in pain is inactive, anorectic, and poorly responsive, and it may grind its teeth. Pain is assumed based on anthropomorphic evaluation of the injury or surgery the animal has experienced. See Chapters 31 and 41 for suggested dosages of analgesics.

Adhesion Formation

Problems resulting from adhesions are regularly found in rabbits; these are most often reflected in postoperative problems involving the cecum, colon and bladder and result from adhesions to the uterine stump, broad ligament, or ovarian pedicle. Adhesions associated with gastrotomy, enterotomy, and a variety of other types of gastrointestinal surgery may also occur. Symptoms include recurrent cystitis, cystic calculi, and microurinary calculi.¹⁴

Prevention of adhesions has been the subject of much study, often involving rabbits as animal models of human disease.^6,7 A large number of substances have been used to combat adhesion formation, but the majority of these have proven to either be too toxic for use, to possess a high a complication rate, to be too difficult in application, or simply not to work. Promising substances include hyaluronic acid solutions¹⁰ and sodium carboxymethyl cellulose.⁵ Chondroitin sulfate²⁰ has also been reported to be effective. These agents act by mechanical separation of surfaces as well as adding a protective “finish” to the viscera. Both mechanisms being a feature of their inert nature.

Thrombolytics, such as streptokinase,¹³ have been reported to be effective in adhesion prevention, but they present difficulties with local and systemic administration and the risk of hypersensitivity. There have been several studies using recombinant tissue plasminogen activator (rt-PA) in rabbits.^3,19 In a rabbit adhesion model, rt-PA was found to reduce the primary and recurrent adhesion rates by 80%.³ Use of rt-PA was shown to be safe in the presence of colonic anastomoses and did not alter abdominal wound strength or increase postoperative hemorrhage.

Other studies have evaluated the use of endoscopy to correct adhesions as compared with traditional laparotomy.²³ These have shown that laparoscopic adhesiolysis is associated with a significantly reduced formation of new postoperative adhesions as compared with laparotomy.

Choice of Suture Material

The biologic and physical characteristics of suture material influence wound healing. New suture material made from polymers that are removed by hydrolytic degradation are much less reactive and cause fewer and weaker adhesions. For example, monofilament polyglyconate (Maxon, Davis & Geck, Manati, PR) or other similar monofilament synthetic suture for closure of gastrotomy, enterotomy, or colotomy sites, cesarean sections, or other major abdominal surgery are excellent choices. Stainless steel or tantalum clips (Hemoclip, Weck, Research Triangle Park, NC) are excellent for vessel and small pedicle ligation with minimal tissue reaction. A study of laser anastomosis for sutureless closure of the colon of rabbits has been published,¹⁵ and this technique holds potential for the future.

Skin Closures

Rabbits commonly remove skin sutures. All but the smallest rabbits will chew sutures of nylon or even stainless steel monofilament. Intradermal closures work very well but are time-consuming to place because of the tenuity of rabbit skin. Cyanoacrylate tissue cement (Vet-Bond, 3M Medical-Surgical Division, St. Paul, MN) works well to hold rabbit skin but is often removed by the rabbit. Skin staples are both reliable and well accepted by rabbits and their owners.

Ovariohysterectomy

The reproductive tract of the female rabbit is unusual compared with that of the dog or cat (Fig. 21-1). The uterus is bicornate. Each uterine cornua possesses a cervix (there is no uterine body). At maturity it is coiled in the caudal abdomen, cranial and just dorsal to the urinary bladder. Long uterine (tuba uterina) and infundibular tubes (infundibulum tubae) extend between the cornua and the ovary.²¹ The uterus is easily exteriorized but is more fragile than that of other species. In a healthy doe, the caudal portion of the broad uterine ligament (ligamentum latum uteri), the mesometrium, is a principal fat-storage site that makes identifying and ligating uterine vessels difficult. The urethra of the female rabbit empties into the proximal end of a deep vaginal vestibule. Expression of the bladder with the animal in dorsal recumbency often leads to retrofilling of the vaginal vault. This can be a source of contamination of the peritoneal cavity during uterine surgery. It is also important not to confuse the vaginal vault with the bladder.

Fig. 21-1 Uterus of a 4-month-old nulliparous rabbit at surgery for ovariohysterectomy. The ovarian vessels have been clamped with mosquito hemostatic forceps, ligated, and incised and the uterus exteriorized. The top of the illustration is cranial. The rabbit’s ovary (o) is often coiled in the uterine/infundibulum tubules (ut/it). The bicornate uterus (cornua) (u) end in a paired cervix (cc). The broad ligament (bl) of this young, well-fed rabbit is not so filled with fat that the uterine vessels cannot be easily identified. The arrowheads mark the point where the uterine vessels are transfixed and ligated. The broad ligament is trimmed from the vagina to the level of the cervix, as marked by the orange lines. Finally the cranial end of the vagina is double ligated and transfixed just caudal to the cervix at the level of the black lines.

With the rabbit anesthetized before surgery, empty the rabbit’s bladder by gentle palpation. Shave and prepare the abdominal area and restrain the rabbit on the surgery table in dorsal recumbency, draped for surgery. Make a 2- to 3-cm midline incision centered over the cranial pole of the bladder, about half the distance between the umbilicus and the cranial rim of the pubis. Lift the narrow linea alba from the abdominal contents as you make a stab incision into the abdomen; be very careful in entering the abdominal wall, because the thin-walled cecum and bladder are often pressed firmly against the ventral abdomen. In the reproductively mature rabbit, the uterus can typically be seen as it lies cranial and dorsal to the cranial pole of the bladder and may be lifted through the incision with forceps. A spay (snook) hook is not necessary and may cause damage to the cecum. Follow the uterus to the uterine/infundibular tubes. The uterine/infundibular tubes are coiled in a large loop. They are several times longer than those of a dog or cat; be careful not to leave any portion of them. Multiple vessels are associated with the ovary, but they are smaller than those of many mammals. Carefully identify each and double ligate them with transfixing sutures of chromic gut or synthetic absorbable suture. Hemorrhage is seldom a problem with these vessels. The uterine vessels stand as much as a centimeter off the uterus and may be of significant size in mature does. Double ligate these vessels with transfixing ligatures to the vaginal serosa. The mesometrium may then be stripped away from the cervix and vagina. Ligate the uterus just caudal to the cervices. Avoid contaminating the abdomen with urine or vaginal contents if a caudal ligature is used. Ligate each uterine horn if removed cranial to the cervix, or carefully ligate at the dorsal vagina if the uterus is removed caudal to the cervices. Closure of the abdomen is routine. Close the skin with surgical staples, an intradermal suture pattern, or tissue cement.

Orchidectomy (Castration)

Sexually active male rabbits (bucks) have obnoxious sexual mounting and urine-marking behaviors that generally lead their owners to want to have them neutered. Furthermore, bucks may become territorial and possessive about their environment and owners, leading to aggressive behavior.

The rabbit’s testes are similar to those of the cat but may move freely from the scrotum to the abdomen through an open inguinal canal. Soft tissue herniation and strangulation of bowel loops is prevented by a large mass of fat associated with the epididymis, which rests in the inguinal canal when the testicle is in the scrotum.

For castration, anesthetize and restrain the buck in dorsal recumbency. Carefully shave the hair from the scrotum and surrounding area and surgically prepare and drape the area to minimize contamination. Make a 1- to 1.5-cm incision with a No. 15 scalpel blade through the skin and vaginal tunic on the ventral surface of both sides of the scrotum (Fig. 21-2). Remove the testis from the tunic and carefully tear the ligament of the testicle from the tunic with a dry gauze sponge. Pull the testis caudally to expose a section of the vas deferens and the vascular structures of the spermatic cord, then tie them in an overhand knot with a small Mayo needle holder or mosquito forceps. Alternatively, ligate the duct and vasculature with 2-0 to 3-0 synthetic absorbable suture. Cut the duct and vessels distal to the knot or ligature and return the spermatic cord to the inguinal canal in such a way that it can be recovered if bleeding occurs. Return the tunic to the scrotum and repeat the process for the remaining testis.

Fig. 21-2 A technique for castration of a rabbit. A, The scrotum and surrounding skin is prepared for sterile surgery. B, The skin and vaginal tunic (VT) on both sides of the scrotum are incised (arrowhead). C, The testes (T) are removed from the vaginal tunic and the ligament of the testicle (L) is torn from the tunic using a dry gauze sponge (G). D, The vas deferens and vessels of the spermatic cord (SC) are tied with an overhand knot using a needle holder. F, The tunic is returned to its correct position within the scrotum.

Stay updated, free articles. Join our Telegram channel

Join