Abdominal surgery in ferrets (Proceedings)


Abdominal surgery in ferrets (Proceedings)

Nov 01, 2009

Gastrointestinal foreign bodies

Foreign body (FB) ingestion is particularly a problem in ferrets less than one year of age. Young ferrets enjoy chewing on and ingesting soft rubber such as latex or foam rubber, cork, and occasionally cloth material. After they reach one year of age their chewing behavior decreases greatly. In older ferrets obstruction or partial obstruction with trichobezoars becomes a relatively frequent problem. In ferrets with a gastric FB that is not causing an acute obstruction clinical signs are vague including intermittent anorexia, dark tarry stool and depression. Vomiting is an infrequent finding. Gradual weight loss may occur after weeks of illness.

Diagnosis of GI FB is made based on physical examination and radiography. Most ferrets have a relaxed abdomen and are easy to palpate. In most cases the clinician will be able to palpate the foreign material. Small trichobezoars may be difficult to palpate as they compress easily. Objects in the stomach are more difficult to palpate. Radiography may reveal a foreign object or gas pattern consistent with ileus secondary to intestinal obstruction. Contrast radiography may be performed if plain films are not diagnostic.

Treatment of GI FBs involves exploratory laparotomy and gastrotomy or enterotomy to remove the FB as an emergency procedure. The patient should be stabilized and rehydrated prior to surgery. A complete abdominal exploratory is performed and the entire GI tract evaluated. The techniques for gastrotomy and enterotomy in ferrets are analogous to those used in other species.

The gastrotomy incision is made in an avascular region of the stomach. Take a full thickness biopsy of the stomach wall using scissors to cut a slice off of one side of the primary incision and save it in the event that the ferret continues to have problems postoperatively. A two layer closure is recommended.

The diameter of the small intestine of ferrets is quite narrow and there are reports of intestinal stricture following routine enterotomy in ferrets. It is recommended that the enterotomy be made on the antimesenteric border of the intestine in the aborad (smaller) portion as this is the healthier portion of bowel. To minimize the risk of postoperative stricture, the enterotomy is closed transversely, in effect widening rather than narrowing the lumen at the enterotomy.

Adrenal disease

At least 95% of generalized alopecia in neutered ferrets 2 years of age or older is caused by neoplasia or hyperplasia of the adrenal glands. Histologically there can be adrenal cortical hyperplasia, cortical adenoma or cortical adenocarcinoma. Metastasis is uncommon but has been reported.

Clinical signs associated with adrenal neoplasia consist primarily of bilaterally symmetrical pruritic alopecia, beginning at the hind quarters and progressing cranially along the body. Spayed female ferrets frequently present with vulvar enlargement with or without alopecia. Male ferrets with may present with prostatic enlargement or cysts with or without alopecia. Splenic enlargement and insulinomas are also common in ferrets with adrenal neoplasia.

The diagnosis is suspected on physical examination and history. Confirmation is frequently obtained using ultrasound evaluation of the adrenal glands. An adrenal steroid panel is available through the University of Tennessee to evaluate the circulating levels of some of the hormone precursors. Unfortunately, some adrenal masses do not produce these few hormones that are assayed in this steroid panel but these ferrets still have adrenal disease. Therefore, the panel is good if positive but a negative test does not rule out adrenal disease.

Surgery is considered the treatment of choice. A standard ventral midline celiotomy is performed. A complete exploratory celiotomy is performed because adrenal neoplasias frequently occur coincidentally with insulinoma and lymphoma. It is also important to evaluate the ovarian and uterine stumps and the mesentery for any evidence of ectopic or residual ovarian tissue.

The left adrenal gland is found deep within the sublumbar retroperitoneal fat just cranial and medial to the cranial pole of the left kidney. Only the ventral surface of the gland can be visualized through the peritoneum. In some cases, this surface may appear grossly normal while the abnormal portion may be deeper and not readily visible. It is important to open the peritoneum and explore the entire gland using blunt dissection before declaring it normal. The right adrenal gland is located by elevating caudate lobe of the liver which touches the cranial pole of the right kidney. The hepatorenal ligament is incised and used to retract the liver ventrally allowing exposure of the adrenal. The adrenal gland is visualized on the dorsal aspect of the caudal vena cava attached to it. Because of its intimate association with the vena cava, removal of the right adrenal gland is more difficult.

The adrenal glands are evaluated for size, color, and shape - 2-4 mm × 4-6 mm and light-pink and homogenous. Lumps, hard spots, discolorations, cysts or gross enlargement are indications for removal. If both adrenal glands appear to be involved it is recommended that both be removed.

To remove the left gland, the adrenolumbar vein (phrenicoabdominal) over the left adrenal must be ligated on each side. Hemostatic clips are very for this. Once the vessels have been ligated, the adrenal gland is removed using sharp or blunt dissection. Cotton-tipped applicators are valuable in this dissection. Some tumors are large enough to envelope the kidney and invade the caudal vena cava, underscoring the value of adrenalectomy when the gland is small and not involving other organs.

Vascular clamps are vital in performing right adrenalectomy in ferrets. These clamps are designed occlude blood vessels atraumatically so the vessel wall is not damaged. The gland and associated cava are dissected circumferentially. When they are free from surrounding tissues, the clamps are applied on the cava cranial and caudal to the adrenal. With the aid of magnifying loupes, a plane of dissection is developed between the adrenal and the vena cava. Dissection is continued until the adrenal is removed from the surface of the vena cava. Prior to releasing the clamp inspect the wall of the cava for small holes. Holes should be closed with a fine, absorbable suture such as 6-0 to 8-0 on a small needle. There are usually tiny holes in the wall that are not identifiable even with magnification. Hemostatic aides are helpful to control bleeding from these. Apply gentle pressure for approximately 5 minutes allowing the holes to seal. Irrigation is kept to a minimum to prevent clots from being dislodged. If an incision is created in the vena cava during dissection it is closed with a simple continuous pattern of 6-0 to 8-0 monofilament suture on an atraumatic needle.

Abdominal closure is routine. Postoperatively a dose of dexamethasone at 1 mg/kg body weight is administered (I usually give this intraoperatively as soon as the tumor is removed). In 24 hours the ferret is given 0.1 mg/kg prednisone orally once daily for 3 days followed by the same dose every other day for 3 treatments. Although postoperative steroids are not necessarily required it appears that many ferrets suffer less depression and have a more rapid return to their normal state when glucocorticoids are administered for a short period of time. Following bilateral adrenalectomy, ferrets often require glucocorticoid therapy for a longer period of time. Some require mineralocorticoid supplementation as well. These ferrets usually crump days to weeks postoperatively. They present clinically depressed, dehydrated, and often are nonresponsive. They typically respond to IV fluid therapy and steroid administration. Long term mineralocorticoid supplementation is recommended. Following adequate removal of the adrenal neoplasia, the swollen vulva will generally return to normal within 2 weeks and hair loss will begin to resolve in 1-4 months.