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Avian GI and reproductive surgery (Proceedings)
A simple ventral midline celiotomy provides limited exposure to most abdominal organs in birds. The liver, pancreas and intestines are accessible through this approach.
A simple ventral midline celiotomy provides limited exposure to most abdominal organs in birds. The liver, pancreas and intestines are accessible through this approach. The hepatoperitoneal cavity is entered, but this cavity does not communicate with the air sacs located lateral to it on each side. Ascites is characterized by accumulation of fluid in this cavity. The duodenum and pancreas are immediately under the body wall and it is easy to inadvertently incise these structures. If the liver is of a normal size, it is usually under the sternum making it inaccessible. Coelomitis may cause fluid to accumulate in the hepatoperitoneal cavity. Fluid can be drained and irrigation of the hepatoperitoneal cavity can be safely performed as long as the air sacs are intact.
Exposure using a ventral midline approach can be improved by creating a flap extending along one side of the caudal border of the sternum leaving 2-3 mm of muscle into suture to. A Y shaped incision can be made creating bilateral flaps. Flap approaches often provide the best exposure to mid-abdominal masses, uterine masses, and generalized abdominal disease such as yolk coelomitis. The approach should be limited to the minimum needed to accomplish the task to minimize tissue trauma and disruption of air sacs. It may be difficult to maintain anesthesia with large abdominal approaches that disrupt air sacs. Closing the incision or covering the opening with saline moistened sponges for several breaths along with increasing the percent of anesthetic gas will often help with maintenance of anesthesia.
A transverse abdominal approach provides exposure to a large portion of the abdomen. With the bird in dorsal recumbency a transverse incision is made midway between the vent and the caudal extent of the sternum. The duodenal loop and pancreas lie immediately under the body wal and the ventriculus, pancreas and small intestine are most accessible. If there is hepatomegaly, the caudal extent of the liver may also be accessible. The viscera may be reflected to expose the middle and caudal divisions of the kidneys, the cranial cloaca, and the lower reproductive tract. The body wall incision is closed in a simple continuous pattern and the skin in a Ford interlocking pattern.
A left lateral approach provides good exposure to most of the abdominal organs. The pancreas and structures on the right side are not very accessible through this approach. The bird is positioned in right lateral recumbency with the left leg retracted caudally. The skin incision is made from the middle of the pubis to the sixth rib dorsal to the uncinate process. After the skin is incised, the left leg can be retracted farther caudally to improve exposure. Branches of the femoral artery and vein are located within the body wall coursing toward midline from the area of the coxofemoral joint. These vessels must be coagulated or ligated before the abdominal musculature is incised. An incision is made through the mid-lateral body wall from the level of the pubic bone to the last rib. To gain exposure to the gonad and proventriculus, the last two ribs may need to be transected. The intercostal vessels are located just cranial to each rib. They are coagulated with bipolar forceps or hemostatic clips then the ribs are transected just dorsal to the angle of the sternal and vertebral portions. Avoid the lung which may extend as far caudal as the 7th rib. A retractor, such as a Heiss retractor, is placed between the cut ends of the ribs and used to spread the ribs providing exposure to the more cranial abdominal organs. Closure involves apposition of the abdominal and intercostal muscles. No effort is made to unite the cut ends of the ribs. Skin is closed in a Ford interlocking pattern. This approach offers exposure to the male or female reproductive tract, the ventriculus, the proventriculus, the spleen, the left lung, the left kidney and some of the intestines.
Ingluviotomy and crop surgery
The ingluvies (crop) is a storage organ that is often full and protruding making it susceptible to trauma. It may also be the site where a foreign body has lodged. Hand fed baby birds may suffer from crop burns from overheated food. Fortunately, the crop has a good blood supply and heals well.
An ingluviotomy is used to retrieve foreign bodies or to pass a rigid endoscope into the stomach. The patient is anesthetized, intubated and the head elevated to prevent liquid from getting into the pharynx and being aspirated. Foreign bodies can often be retrieved using blunt, atraumatic forceps or by massaging the object, gently, from the crop. When ingluviotomy is necessary, the skin incision is made in the left lateral cervical region over the. Stay sutures are placed and the incision in the crop is made about ½ the length of the skin incision. The crop is closed with a continuous appositional or inverting pattern. The skin is closed separately over the ingluviotomy incision.
Crop biopsy is also indicated as a tool for diagnosing proventricular dilation syndrome. The biopsy must be taken in a location where there are blood vessels in order to obtain nerves which might demonstrate the typical histologic changes.
When the crop is burned or traumatized, there may be loss of significant portions of tissue. In some birds there will be a true fistula with food dropping out. In more acute burns, it may be difficult to distinguish viable from devitalized tissues. In these cases it is best to wait 3-5 days for a line of demarcation between necrotic and viable tissue to develop. The wound edges should be debrided until the skin can be separated from the crop wall. The skin and crop are sutured closed as separate structures. Placing a feeding tube through the crop will help identify the lumen. In cases where there is significant loss of crop tissue it is best to maintain the longitudinal integrity of the esophagus (crop) as there is a higher likelihood of stricture formation with resection and anastomosis.
Proventriculotomy and ventriculotomy
Proventriculotomy or ventriculotomy is most commonly indicated for removal of foreign objects (such as lead) from the proventriculus or ventriculus not retrievable with an endoscope or flushing technique. Ventriculotomy is considered more likely to leak postoperatively as it is difficult to seal the incision with sutures and birds do not have an omentum. Very fine monofilament material must be used and accurately placed. Serosal patching should be considered to help create a fibrin seal quickly.
A left lateral approach is used. The suspensory tissues surrounding the ventriculus are bluntly dissected and stay sutures placed into the white tendinous portion to elevate the isthmus into the field. Stay sutures should not be placed into the proventriculus or in the muscular component of the ventriculus as these tissues are weak and the sutures will tear through them. Moistened sponges should be used to isolate the proventriculus and contain any gastric contents that may spill. A stab incision is made in an avascular area of the isthmus using a scalpel or scissors (electrosurgery is not used as this causes lateral heat damage that might predispose to incisional leakage). The incision is then extended orad using scissors for a proventriculotomy or aborad for a ventriculotomy. Careful irrigation and suction are used to evacuate the contents. The air sac will be open and irrigation fluids can enter the lung. The incision is closed with a fine monofilament absorbable material on a small atraumatic needle using a simple continuous pattern. No attempt is made to repair the suspensory tissues. The abdominal viscera are gently cleaned and replaced prior to abdominal closure.
Enterotomy is not frequently indicated in avian patients. Historically, birds in need of an enterotomy were considered to have a guarded to poor prognosis. With the use of magnification and fine monofilament absorbable material on a small atraumatic needle, accurate closure is more easily accomplished with a much better prognosis. Magnification and microsurgical techniques are generally required. 6-0 to 10-0 suture in a simple appositional pattern is used.
The cloaca is the cavity into which the kidneys, colon, and reproductive tract empty. The vent is the opening of the cloaca to the environment. The vent sphincter muscle provides continence. Cloacotomy is indicated for a thorough evaluation of the internal structures as in treating cloacal papillomatosis or other masses within the cloaca. Through this approach the surgeon is able to visualize the coprourodeal fold and the uroproctodeal fold as well as the colonic, ureteral and oviductal openings. The openings of the vasa deferentia are generally too small to visualize.
Insert a moistened cotton tipped applicator stick into the cloaca. Using the monopolar electrosurgical tip, incise through the skin, the muscle of the cloacal sphincter, and the mucosa of the cloaca from the vent to the cranial extent of the cotton tipped applicator. Alternatively, small scissors may be inserted into the cloaca and the ventral wall including skin, body wall, and cloaca cut all at once. Using this technique you should not enter the coelomic cavity. Inspect the cloaca and on the dorsal surface you should be able to visualize the ureteral openings and urine/urates flowing into the cloaca. Close the cloacal mucosa using 6-0 monofilament absorbable material in a simple continuous pattern beginning at the cranial extent of the incision. The vent sphincter muscle is closed with a single mattress suture of 4-0 absorbable material. The skin is closed as the last layer over the cloaca and vent sphincter muscle.
Cloacopexy is indicated for treatment of chronic cloacal prolapse. Several procedures have been recommended for the treatment of chronic cloacal prolapse. Because the exact cause of the problem has not been determined, recurrence is observed with all techniques. Even if permanent adhesions are created, the sphincter is typically stretched out and atonic. The cloaca itself often stretches (megacloaca) and the redundant tissue prolapses out the vent which has the appearance of a recurrence.
I use a combination of three procedures to reduce the prolapse, maintain its position, and reduce the size of the vent opening. Make a ventral midline incision in the abdomen. Extend the incision parasternal on both sides. Remove fat from the ventral surface of the cloaca that might inhibit the formation of strong adhesions. Insert an appropriate structure into the cloaca to define its limits. The circumcostal cloacopexy uses the last rib to which the cloaca is sutured to maintain reduction. In birds with cloacal prolapse, there is generally not too much tension when this is done. As an alternative, the organ can be sutured to the caudal border of the sternum. Preplace 2 sutures around the rib at the angle on each side or through the cartilaginous border of the sternum and full thickness through the cloaca. This will anchor the organ in a reduced position; however, the suture will eventually stretch, break, or cut through resulting in failure. To prevent recurrence, permanent adhesions must be created. Close the ventral midline incorporating the cloaca creating a cloacopexy. Scarify, incise, or resect the ventral cloaca to create a raw surface. Pass the suture through one side of the body wall incision, full thickness through the cloaca, and through the other side of the body wall. This encourages the cloaca to heal within the body wall forming permanent adhesions between these structures. Ventplasty is indicated in birds with chronic cloacal prolapse where the vent sphincter has become atonic. This may be the result of chronic straining or a primary neuropathy. The sphincter is incompetent and is no longer able to prevent the cloacal tissues from prolapsing. Ventplasty (analogous to canthoplasty of the eyelids) is used to decrease the size of the vent opening.
Incise the skin over the vent sphincter at the lateral commissures exposing the underlying muscle. Place fine monofilament absorbable suture transversely in the mucosa from cranial to caudal. Next, the vent sphincter muscle is apposed with a synthetic absorbable in a mattress pattern between the cranial and caudal aspects of the sphincter. Finally, the skin edges are apposed cranial to caudal using a synthetic absorbable material. Remove enough tissue from each side so that only 1 or 2 cotton tipped applicators can be passed through the vent. Postoperatively, the patient is monitored to assure that it can still void urine, urates, and fecal material. Some birds will develop stricture a few weeks after this procedure. Under general anesthesia, stretch the sphincter with a cotton tipped applicator in a circular motion. In birds that have had strictures, I have only had to do this procedure once.
In most adult birds, the right reproductive tract is virtually nonexistent. The arterial supply is through the ovario-oviductal branch of the left cranial renal artery with venous drainage through 2 ovarian veins into the caudal vena cava. These vessels and many nerves enter through a broad based ovarian hilus on the dorsal aspect of the coelom. The magnum is the longest and most coiled portion of the oviduct and has numerous tubular glands which are responsible for the white of the egg. The isthmus is a narrowing in the oviduct with less prominent folds and a transparent junction with the magnum. The shell membranes are produced in this section. The uterus (shell gland) has no distinct separation from the oviduct and it is in this location that the shell is applied. The vagina is attached to the cloaca and is in an S configuration. It is very thick and muscular but has no glands. The oviduct and uterus are suspended from the dorsal coelom by a double layer of peritoneum which forms the dorsal and ventral ligaments. These ligaments contain smooth muscle which is responsible for transporting the egg along the pathway. The ventral ligament comes together caudally as a thick muscular band which attaches to the caudal uterus and vagina. The oviduct is supplied by three major blood vessels: the cranial oviductal artery is a branch of the left renal artery, the middle ovarian artery is a branch of the ischiatic artery, and the caudal ovarian artery is a branch of the pudendal artery.
Female reproductive surgery
Hysterotomy or hysterectomy may be performed to remove an obstructing egg. Where oviduct rupture has occurred, celiotomy is necessary to remove the egg. Chronic or recurrent egg related problems are also indications for hysterectomy. Although some hysterectomized birds exhibit copulatory and laying behavior, yolk coelomitis is rarely a problem. Because the procedure carries some risk, it is not currently recommended as a prophylactic procedure. In my lab we performed hysterectomies in juvenile cockatiels using endosurgical techniques. Because the uterus is small and the vessels underdeveloped, the procedure is much easier and safer. After 9 years, there have been no deaths attributable to reproductive problems.
I prefer a left lateral approach for this procedure. The ovary is visualized by retracting the proventriculus ventral. The ventral suspensory ligament is not vascular and throws the oviduct and uterus into numerous folds. The ligament is broken down with bipolar forceps allowing the oviduct to be stretched out into a more linear configuration providing exposure to the vessels in the dorsal suspensory ligament. Two hemostatic clips are applied to cranial oviductal artery and vein as they emerge from the ovary. If they are accidentally torn, a small piece of hemostatic foam is applied with gentle pressure to aid in clotting. The dorsal suspensory ligament of the uterus is identified from the dorsal body wall to the oviduct and uterus. You will see numerous branches supplying the oviduct and uterus. Each of these vessels is coagulated with the bipolar forceps as close to the oviduct and uterus as possible minimizing hemorrhage as the ligament is transected.
Once all the blood vessels are coagulated, the uterus and oviduct can be exteriorized so its junction with the cloaca is visible. This is where the clips or ligatures will be applied prior to the transection. A cotton-tipped applicator is inserted through the vent into the cloaca to help delineate its boundaries. Two clips or ligatures are applied to the uterus near its junction with the cloaca. The uterus is then transected distal to the clips. Prior to closure, the abdominal cavity should be evaluated for any residual hemorrhage. If hemorrhage is found, the bipolar forceps may be used to control it. Clips are an alternative for larger vessels that cannot be controlled with bipolar forceps. A hemostatic agent is placed along the dorsal coelom along where the vessels were transected to control hemorrhage during recovery.
The indications for orchidectomy in birds remain anecdotal. In male birds with chronic cloacal prolapse, straining and masturbation may be contributing factors. Castration may prevent these behaviors which may decrease the chances of recurrence of the prolapse. In aggressive male birds, castration may ameliorate their behavior. In the author's experience, most male birds have a decrease in aggressive behavior following castration.
Male birds have two gonads which lie on the external iliac vessels at the point they join to become the caudal vena cava. In some species the testicles are pigmented (black in cockatoos). They are attached to these veins by a short ligament. Numerous small vessels pass through this ligament to provide blood supply to the testicle. The size of the testicles and the associated vasculature vary with species and reproductive status. In sexually active birds the testicles are large and vascular making castration more difficult.
The testicles are approached through a left lateral celiotomy. The left testicle is identified caudal to the lung and ventral to the kidney. The caudal pole of the testicle is gently grasped with fine forceps and elevated from the external iliac vein exposing the short ligament. A vascular clip is applied between the testis and the vessel. Fine scissors are used to cut the ligament along the clip, distal to it. Depending on the size of the clip and the size of the testicle, it may take more than one clip to be able to remove the testis. Once the ligament is cut, the testis can be elevated farther allowing a second clip to be placed cranial to the first one. The ligament is then cut along the second clip. This procedure is continued until the testis is removed. The site is inspected for the presence of any testicular tissue which must be removed. The right testicle is adjacent to the left but separated by an air sac membrane. This membrane is opened using blunt or sharp dissection to create a window through which the right testicle can be removed. Once the right testis is accessible it is removed in a manner analogous to that described for removal of the left testis. It is somewhat more difficult because the right testicle is deeper (through the left lateral approach); however, it can be removed without too much difficulty.
A right-angled hemostatic clip applier is advantageous especially in smaller birds where exposure is limited. The right-angled applier allows the clip to be placed under the testis through the abdominal approach without having to lay the applier flat. In addition to controlling hemorrhage from the vessels supplying the testis, the clips provide a barrier to help protect the fragile external iliac veins from being accidentally cut with the scissors. If the vein is damaged during dissection, gentle pressure is applied and a hemostatic agent is placed at the site to aid in hemostasis.