Services

Ferret Surgery

Michael B. Mison, DVM, Diplomate ACVS
R. Avery Bennett, DVM, MS, Diplomate ACVS

I.    General Surgical Considerations
A.    Presurgical Evaluation
As in all species a complete physical examination and appropriate pre-surgical laboratory tests are essential parts of successful surgery.  Ferrets are commonly diagnosed with cardiac disease (dilated cardiomyopathy being the most common).  Care should be taken to closely examine the heart and lungs on pre-surgical evaluation.  Some of the clinical signs of cardiac disease such as weight loss, anorexia, inactivity, weakness, and hind limb ataxia are common to other diseases for which surgery may be contemplated.  Ferrets often do not cough with cardiac disease and may be asymptomatic.  Chest radiographs, an electrocardiogram, and an echocardiogram should be performed prior to surgery if cardiac disease is suspected.

B.    Perioperative Care
In general ferrets are hardy and make excellent surgical candidates.  Body temperature should be closely monitored during surgery and recovery.  Precautions to prevent heat loss include the use of a circulating warm water blanket, warmed saline for irrigation, administration of warmed intravenous fluids, a radiant heat lamp and a force warm air blanket.  As in cats but more commonly, rebound hyperthermia during recovery occurs in ferrets, so the recovery cage should not be prewarmed and care should be taken to avoid overheating.  Most heat sources should be removed when the body temperature stabilizes at around 100-101o F.
An indwelling intravenous catheter should be placed and warmed fluids administered during most procedures at a rate of 10 ml/kg/hr.  Ferret skin is relatively thick, so it is often necessary to make a small nick in the skin with a # 11 scalpel blade or the bevel of a 20 ga needle before attempting to pass the catheter through the skin.  Either cephalic or jugular placement is possible.  A 24 gauge cephalic catheter works well in most ferrets.  Due to the fact that a high percentage of ferrets have insulinomas which may or may not be clinically evident, an intravenous fluid solution containing 5% dextrose should be used such as lactated Ringer’s solution with added dextrose.

Ferrets have a gastrointestinal transit time of only three to four hours. They only need to be fasted for approximately three hours prior to anesthesia.  A more prolonged fast can induce hypoglycemia even in healthy ferrets.  Once the patient is awake and walking, feed  kibble or if indicated, make a gruel made from dry ferret chow blended with water and a high calorie liquid supplement such as Deliver (Mead Johnson, Evansville, Ill.), Ensure (Ross Products Division, Abbot Laboratories, Columbus, Ohio), or Sustical (Mead Johnson, Evansville, Ill.).  This is especially important in procedures on older ferrets with insulinomas.

C.    Anatomic Considerations
Ferrets often have thicker skin compared to other species.  It may take added pressure to incise through the skin completely during the initial approach.  The linea alba is thin and easily seen.  Postsurgical bruising along the incision is not uncommon in ferrets.  This is seen even with diligent attention to hemostasis.  The discoloration usually resolves within 5 to 7 days, but owners should be warned about the possibility of it developing.
A common finding during abdominal surgery is an enlarged spleen.  When enlarged, the spleen extends in a diagonal fashion from the upper left to the lower right quadrant of the abdominal cavity.  For this reason it is important to avoid damage to the spleen when entering the abdomen.  The small and large intestines are difficult to distinguish anatomically and the transition from small intestine to colon is grossly marked by only by a change in vascularity.  Ferrets lack a cecum.
 
D.    Instrumentation
Many of the same instruments used in canine and feline surgery can be used in ferrets.  The Lonestar Veterinary Retractor is very useful for retracting the abdominal wall for celiotomy or for retracting the wound edges for other procedures (Jorgensen Laboratories, Inc. Loveland, CO, USA).  Small needle holders and mosquito forceps are often handy when working in the small abdominal cavities of ferrets.  In addition, the small and medium size hemostatic clips (e.g. Hemoclips; Weck Surgical Instruments, or Ligaclips; Ethicon) make occlusion of vessels much easier when performing adrenalectomies.  A generous supply of sterile cotton tipped applicators is very useful for blotting and to aid in dissection of fragile tissues.

II.    Abdominal Surgery
A.  Liver biopsy
Liver biopsy is indicated during most exploratory celiotomies. Diagnosis of hepatic lipidosis, lymphoma, metastatic insulinoma, and other hepatic diseases may be obtained using hepatic biopsy.  The conformation of the liver lobes varies among individual ferrets. In some patients, a pointed portion of a liver lobe may be identified. A suture fracture technique as described for partial pancreatectomy is appropriate for liver biopsy when a protruding point of liver is identified. A ligature of 4-0 braided absorbable suture is looped around the protruding section of liver and tightened to cut through the liver parenchyma while ligating any vessels. Scissors are used to transect the tissue distal to the ligature leaving the ligature to control hemorrhage.

If all lobes have a rounded configuration, a transfixation suture fracture technique is used. This method is also used if a specific section of liver is desired for biopsy because of the presence of a lesion. The needle (atraumatic) is passed through the liver parenchyma and the suture is tied to cut through the liver on one side. The second throw on the suture is made to cut through the liver on the other side ligating the vessels supplying the liver distal to the ligature. The tissue is then transected distal to the ligature allowing excision of the biopsy specimen. Any residual hemorrhage is controlled with a hemostatic agent.

B.  Splenic Surgery
Splenomegaly is very common in ferrets and may be incidental or incidental or indicative of disease.  The spleen is easily palpated in ferrets and readily visualized on abdominal radiographs.  Primary splenic disease is uncommon in ferrets and splenomegaly is generally a benign condition and routine removal of the spleen is not recommended.  In cases where the spleen is excessively large, when the spleen is interfering with normal abdominal function, or if it is lumpy or irregular in shape, splenectomy or partial splenectomy should be performed.  A spleen that increases rapidly in size over a very short period of time or one that is irregular in shape, painful or so large that it interferes with abdominal viscera function is cause for concern.  Conditions which cause splenomegaly in ferrets include lymphoma, insulinoma, cardiomegaly, adrenal neoplasia, systemic mast cell tumors, Aleutian disease, eosinophilic gastritis, hemangiosarcoma, primary splenic neoplasia, hypersplenism and splenitis. The most common histologic diagnosis from Splenomegaly in ferrets is extramedullary hematopoiesis. These ferrets are actively producing red blood cells in their spleen and splenectomy can result in chronic anemia as this important site of red cell synthesis is removed. In cases where the spleen is excessively large, when the spleen is interfering with normal abdominal function, or if it is lumpy or irregular in shape, splenectomy or partial splenectomy should be performed.
Preoperative biopsy of the spleen is recommended as partial splenectomy is preferred over complete removal if possible. Lymphoma, myelogenous leukemia, and nonvascular neoplasia such as leiomyosarcoma and fibrosarcoma can be diagnosed with splenic biopsy. Percutaneous biopsy is contraindicated with hemangiosarcoma as it may induce fatal hemorrhage; however, this tumor type is uncommon in ferrets. Ultrasound will help determine the safety and efficacy of percutaneous biopsy and is very useful for guiding the needle to collect an appropriate sample. Fine-needle aspiration is currently recommended for percutaneous biopsy of the spleen because it is simple, carries little risk, and provides excellent samples.  Using a 25 ga 1 inch needle on a 6 cc syringe, the spleen is isolated and held in position. As the needle penetrates the spleen, negative pressure is applied and maintained as the needle is advanced into the parenchyma. Negative pressure is discontinued and the needle slowly withdrawn. Releasing pressure prior to withdrawal minimizes the risk of blood contamination.

Splenic biopsy may be performed during an exploratory celiotomy. If the sample is to be taken from the margin, mattress sutures are placed through both surfaces of the spleen. The parenchyma is transected distal to the sutures leaving them in place to control hemorrhage. To remove a central portion, two parallel incisions are created long and deep enough to obtain a representative sample. Then, two additional incisions are made perpendicular to the original incisions creating a rectangular section of spleen to be removed. Mattress sutures are placed across the defect to control hemorrhage.

Partial splenectomy is indicated as treatment of non-neoplastic conditions such as extramedullary hematopoiesis as it allows for retention of normal splenic function. This procedure should only be performed if the spleen is so large that it interferes with normal physiologic functions. The vessels supplying the portion of the spleen to be removed are double ligated or clipped, and transected at the hilus. In most cases the caudal portion (free end) of the spleen is removed as it is less likely to result in vascular compromise to the stomach. After several minutes, a line of demarcation will be visible between the viable portion of the spleen and the section which has been deprived of its blood supply. Using this line of demarcation, the splenic tissue is pinched between the thumb and forefinger milking the pulp toward the ischemic tissue. Forceps are placed along the flattened portion and the spleen is transected distal to the clamp. The cut surface along the clamp is sutured with an absorbable material in a continuous pattern. Digital pressure or a hemostatic agent can be used to control residual hemorrhage following removal of the clamp. Alternatively, mattress sutures are placed through the parietal and visceral surfaces of the spleen along the line of demarcation. The spleen is transected distal to the sutures. Automatic stapling devices, if available, are excellent for performing partial splenectomy.

Total splenectomy is performed beginning at the caudal or free end of the spleen by double ligating or clipping the vessels at the hilus of the spleen (splenic and short gastric vessels) and transecting the vessels between the ligatures. An alternative method which is faster involves ligation of the short gastric vessels and the splenic vessels distal to the pancreatic branch; however, using this technique, ischemic pancreatitis can result from inappropriate ligation of the splenic vessels.

Following splenectomy, dogs are less tolerant of experimentally induced hemorrhagic shock and do not respond as well to strenuous exercise. Sepsis following splenectomy as occurs in humans has not been reported as a complication in animals. Effects of splenectomy in ferrets have not been studied.

III.    Endocrine System
A.  Adrenal Disease
Adrenocortical disease is very common disease in ferrets.  This syndrome is strictly an adrenal disease as the pituitary is not involved.  The levels of one or more of the plasma androgens, estradiol, or 17-hydroxyprogesterone may be elevated as a result of adrenal cortical hyperplasia, adrenal cortical adenoma, or cortical adenocarcinoma is diagnosed.  Serum cortisol concentrations are rarely elevated in ferrets.

Clinical signs associated with adrenal neoplasia consist primarily of bilaterally symmetrical alopecia, beginning at the hind quarters and progressing cranially along the body. Unlike endocrine alopecia in most mammals, approximately 1/3 of ferrets with adrenal disease the alopecia is often associated with pruritus. Spayed female ferrets frequently present with vulvar enlargement with or without alopecia. Male ferrets with adrenal neoplasia occasionally 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 (Androstenedione, Dehydroepiandrosterone sulfate, Estradiol, 17-hydroxyprogesterone).  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.

Medical management with Mitotane (o,p’-DDD) or Ketoconazole is generally unsuccessful and may be accompanied by dangerous side effects.  The use of a long-acting GnRH analog Leuprolide acetate (Lupron) has been shown to lead to significant reductions in plasma androgen concentrations.  Treatment with Lupron eliminated or reduced clinical signs associated with adrenal disease, however, the response to treatment was transitory.  Time to recurrence ranges from 1.5 to 8 months and long term effects unknown.

Surgery is considered the treatment of choice.  A standard ventral midline celiotomy is performed and a complete exploratory celiotomy is done.  Because adrenal neoplasias frequently occur coincidentally with insulinoma and lymphoma, the lymph nodes, liver, spleen, and pancreas must be evaluated. It is also important to evaluate the ovarian and uterine stumps and the mesentery for any evidence of ectopic or residual ovarian tissue.  The adrenal glands are evaluated for size, color, and shape. They should be 2-4 mm wide, 4-6 mm long, and appear light-pink and homogenous. The appearance of lumps, hard spots, discolorations, cysts or gross enlargement is an indication for removal. If both adrenal glands appear to be involved it is recommended that both adrenals be removed.  If it appears that the adrenal gland cannot be safely removed without damaging adjacent structures such as the caudal vena cava, it is best to remove as much as possible in order to obtain a biopsy and debulk the mass. When an adrenal mass is only debulked, it is likely the mass will re-grow.

The left adrenal gland is found within the sublumbar fat just cranial and medial to the cranial pole of the left kidney. It is deep within the lumbar fat in the retroperitoneal space. 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 the caudal most pole of the caudate lobe of the liver which touches the cranial pole of the right kidney. A thin membrane extends from the caudal tip of this liver lobe towards the kidney (hepatorenal ligament). This may be incised sharply to allow the liver lobe to be elevated. The hepatorenal ligament can then be 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 tightly to it. Usually it appears more dorsal than strictly on the right side of the vena cava. Because of its intimate association with the vena cava, removal of the right adrenal gland is more difficult.

It is generally easy to remove the left adrenal. The adrenolumbar vein (phrenicoabdominal) courses over the left adrenal gland and must be ligated on each side of the gland prior to removal. Large tumors may have other large vessels supplying them which might require ligation or cauterization. Hemostatic clips are very valuable in controlling hemorrhage from these vessels. 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. These are much harder to remove safely, underscoring the value of adrenalectomy when the gland is small and not involving other organs.

Vascular clamps are vital in performing right adrenalecotomy in ferrets. These clamps are designed occlude blood vessels stopping flow but atraumatically so the vessel wall does not leak or cause thrombi to form. The gland is dissected from both the right and left sides of the caudal vena cava to isolate the tumor as much as possible prior to placing the clamp. When the adrenal is free from surrounding tissues 360o and only attached to the vena cava, the clamps are applied. With the aid of magnifying loupes, a plane of dissection between the adrenal and the vena cava is identified. Through this plane, 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 o 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. Surgicel is oxidized regenerated cellulose and is a cloth-like material that can be wrapped around the cava where the dissection occurred. When the clamps are removed, hemorrhage will be noted from small holes in the wall of the vena cava. The Surgicel is quickly placed on the vena cava where the adrenal was dissected free and gentle pressure is applied for approximately 5 minutes. This will allow the holes to seal. The Surgicel is absorbable and left in place. Irrigation is kept to a minimum to prevent the Surgicel 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.  Another technique described for partial excision of the right adrenal involves the use of hemostatic clips. Once the gland is freed from surrounding tissues, hemostatic clips are applied between the gland and the caudal vena cava. The tissue is then transected along the clips which provide hemostatis of vessels between the adrenal and the vena cava. Using this technique, more of the adrenal tissue remains in the ferret increasing the chances for recurrence.

Abdominal closure is routine. Postoperatively a dose of dexamethasone at 1 mg/kg body weight is administered.  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. Rarely, they require mineralocorticoid supplementation as well. These ferrets usually decompensate a couple of 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 in these patients. Patients are returned to a normal diet as soon as possible postoperatively. 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.

B.  Insulinomas
Insulinomas are pancreatic beta cell tumors and are one of the most common tumors that occur in middle-aged to older ferrets.  The disease occurs with approximately the same degree of frequency as adrenal neoplasia and the two diseases commonly occur at the same time affecting both male and female ferrets 2 years of age or older.  The tumor produces high levels of insulin driving glucose out of the circulation and into the cells leading to hypoglycemia. 

Clinical signs can be categorized as neuroglycopenic or adrenergic manifestations.  Neuroglycopenic signs result from the effect of hypoglycemia on the central nervous system. Clinical signs generally consist of weakness and depression. These signs may be subtle and short-lived and may resolve on their own early in the course of the disease.  Frequently, ferrets salivate and paw at the mouth as if experiencing nausea. As the disease progresses the periods of weakness and lethargy become more pronounced and persistent. Some animals eventually develop neurologic seizures, coma and may die.  Adrenergic signs occur when blood glucose decline rapidly, resulting in catecholamine release and increased sympathetic tone.  These signs include tachycardia, hypothermia, tremors, nervousness, and irritability.

Definitive diagnosis is made based on a fasting (4-6 hr) blood glucose of less than 70 mg/dl (normal is 90-100 mg/dl).  The presence of an elevated blood insulin concentration coupled with hypoglycemia further supports the diagnosis.  Generally insulinomas are too small to detect with ultrasonography, however, this modality may be useful in pre-surgical evaluation and prognostication.

Medical therapy is performed to alleviate clinical signs of hypoglycemia but does not stop the progression of the insulinoma.  The recommended treatment for insulinoma is surgical excision. Patients with insulinoma should receive 2.5 % dextrose + 0.45% NaCl or 5% dextrose in water instead of lactated Ringer’s during the procedure.  As described for adrenal neoplasia a complete exploratory celiotomy is performed to evaluate for the presence of concurrent disease.  It has been reported that insulinoma may metastasize to the liver and spleen indicating the need for biopsy of these tissues during the exploratory celiotomy.

The pancreas has a right limb which is longer and larger than the left limb and is located within the mesoduodenum. At the caudal duodenal flexure, the right limb turns onto itself so that the entire right limb is right of the root of the mesentery. The left limb is shorter and thicker and lies within the deep leaf of the greater omentum. The pancreas is V-shaped and the right and left limbs meet at the apex of the V which is called the body of the pancreas and lies at the pyloroduodenal junction. In most ferrets there is one pancreatic duct within the right and the left limbs which join to form the common pancreatic duct. The common pancreatic duct joins the bile duct and empties into the duodenum as the major duodenal papilla 2.8 cm caudal to the cranial duodenal flexure. In a small percentage of ferrets an accessory pancreatic duct and minor duodenal papilla are present. The cranial and caudal pancreaticoduodenal arteries are the major blood supply to the right limb of the pancreas while the pancreatic branch of the splenic artery supplies the left limb. Analogous veins provide drainage.

To evaluate the pancreas, the free border of the greater omentum is pulled out of the abdomen and wrapped in saline moistened sponges. The proximal portion of the duodenum is exteriorized while the colon is retracted caudally. The left lobe of the pancreas is visualized in the deep leaf of the greater omentum. The right lobe is visualized within the mesoduodenum. The body of the pancreas is along the pyloroduodenal junction. By moving the duodenum toward midline the dorsal aspect of the right lobe can be seen. Moving the duodenum laterally allows visualization of the ventral surface of the pancreas. These manipulations will allow inspection of the lymph nodes as well.

Insulinomas range in size from microscopic, nonpalpable to 2 cm3, but frequently can be visualized within the pancreas as small firm masses (0.5-2 mm). These small masses can generally be removed by blunt dissection. Hemorrhage is usually minimal and is frequently controlled using gentle digital pressure and a hemostatic agent such as Gelfoam or Surgicel. Small pancreatic ducts will generally seal and leakage of pancreatic enzymes in small amounts may not be associated with pancreatitis because enzyme activation has not occurred and the peritoneum will absorb pancreatic enzymes. Pancreatic wounds heal by fibrin deposition and polymerization, fibrous protein synthesis, and re-epithelialization. Pancreatitis from rough tissue handling can occur but is uncommon.

In some cases, multiple masses are observed. This may be an indication for partial pancreatectomy. It has also been recommended that if no masses are palpable, a section of pancreas (usually the left limb) should be removed and submitted for histologic examination because occasionally these tumors are microscopic and diffusely disseminated within the pancreas. There are two methods for performing partial pancreatectomy - dissection and ligation of ductules and vessels, or suture fracture technique. The suture fracture technique requires less time but is associated with more inflammation. The area of the lesion and distal to it are isolated being careful not to disrupt the common pancreatic duct. The mesoduodenum or the deep leaf of the greater omentum is incised providing access to the right or left lobe of the pancreas, respectively. Be careful not to damage the blood vessels supplying the spleen and duodenum.

Using the dissection and ligation technique, the lobules are gently separated from adjacent tissue until the vessels and duct or ductules are exposed. These are ligated with hemostatic clips or fine, absorbable monofilament suture, then transected distal to the ligatures allowing removal of the tissue. With the suture fracture technique, following isolation, a ligature is passed around the portion of pancreas to be excised. As the suture is tightened, it crushes the parenchyma of the pancreas and ligates the vessels and ducts. The tissue distal to the ligature is excised, leaving a small amount of tissue distal to the ligature. The defect in the mesentery or omentum is closed to prevent entrapment of viscera.
During partial pancreatectomy care is taken to assure that the blood supply to other structures has not been compromised. When a portion of the right limb of the pancreas is removed, if the pancreaticoduodenal vessels are ligated, the blood supply to the proximal duodenum may be compromised. On the left side, ligation of the splenic vessels could occur, compromising blood flow to the spleen. Following partial pancreatectomy, these organs must be evaluated prior to closure to assure the blood supply has not been compromised. In dogs, removal of 80-90% of the pancreas will not alter exocrine or endocrine pancreatic function as long as the common duct is maintained in tact to the remaining portion.
Postoperatively an IV catheter should be maintained for 24-48 hours and the patient should be maintained on 2.5% dextrose + 0.45% saline or 5% dextrose in water at 10% of the body weight for 24 hours. Twelve hours after surgery the patient is given a bland diet in small but frequent meals and fluids are continued either intravenously or subcutaneously converting to lactated Ringer’s solution at 10% of the body weight per 24 hours. The third day following surgery the patient is returned to its normal diet and generally requires no additional medication. Blood glucose is monitored every 12-24 hrs and may take 2-3 days to return to normal.

Surgical removal of insulinomas is generally considered a debulking procedure rather than a curative procedure as insulinomas have a high rate of recurrence and metastatic potential. Surgery provides definitive diagnosis and usually provides temporary relief of clinical signs associated with hypoglycemia. Some ferrets will not become euglycemic even after removal of one or more insulinomas. This appears to be due to metastatic and/or microscopic pancreatic lesions. Fasting blood glucose level should be evaluated two weeks postoperatively and then every 1-3 months to detect if insulinoma is recurring. Subsequent surgeries may be performed; however, in most cases, because surgery is not usually curative, the patient is managed with diet and medications following the first surgery.

IV.    Gastrointestinal System
A.  Gastrointestinal Foreign Bodies
Foreign body ingestion is very common in ferrets.  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 (hair balls) becomes a relatively frequent problem.  The most common clinical signs of GI foreign body in ferrets include nausea, lethargy, anorexia, and/or diarrhea.  Gradual weight loss and potentially severe wasting may occur after several weeks of illness.  Clinical signs are more dramatic in patients with acute gastrointestinal obstruction. These signs include severe depression and dehydration, vomiting, and crying in pain.  Vomiting in ferrets is an inconsistent clinical sign even with complete obstruction.
Diagnosis of gastrointestinal foreign body 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 within the stomach or the intestine. Small trichobezoars may be difficult to palpate as they compress easily and may go undetected. Objects in the stomach are more difficult to palpate as the stomach lays under the rib cage.  Radiography may reveal a foreign object or segmental ileus and/or gaseous distention of the stomach.  A gas distended stomach is consistent with gastric outflow obstruction and is an indication for surgery as soon as possible. Contrast radiography may be performed in some cases if plain films are not diagnostic; however, in the majority of ferrets with gastrointestinal obstruction, contrast radiography is not necessary.

Treatment of gastrointestinal foreign bodies involves exploratory laparotomy and gastrotomy or enterotomy to remove the foreign body.  The patient should be stabilized and rehydrated prior to surgery but surgery should be performed as soon as possible.  A complete abdominal exploratory is performed and the entire GI tract is evaluated for the presence of multiple foreign bodies. The techniques for gastrotomy and enterotomy in ferrets are analogous to those used in other species.  The gastrotomy incision is made in a relatively avascular region of the stomach after isolating the stomach with saline moistened sponges. Stay sutures may be used to allow the surgeon to control the incision. Take a full thickness biopsy of the stomach wall using scissors to cut a slice off of one side of the primary incision.  A two layer closure is recommended using 4-0 monofilament absorbable material with the first layer being a simple continuous appositional pattern and the second layer being an inverting pattern such as a Cushing or Lembert. 

The diameter of the small intestine of ferrets is narrow and there are reports of intestinal stricture following routine enterotomy in ferrets. Additionally, 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. The enterotomy is made longitudinally along the antimesenteric border. In order to minimize the likelihood of postoperative stricture formation, the enterotomy is closed transversely, in effect widening rather than narrowing the lumen at the enterotomy.

Following closure of the gastrotomy or enterotomy, contaminated instruments are exchanged for sterile ones, surgeons’ gloves are changed, and the abdomen is lavaged thoroghly prior to abdominal closure. Food and water are offered as soon as the ferret is awake. Studies have shown that enterocytes need food passage to proliferate and heal lesions. Antibiotics are administered if indicated based on the level of abdominal contamination. The prognosis following surgery is generally good; however, clients must take steps to prevent recurrence. Helicobacter mustelae infection is common and may be asymptomatic until the ferret is stressed. If the ferret does not do well postoperatively, the biopsy can confirm helicobacteriosis.


V.    Urogenital System
A.  Cystotomy
Urolithiasis occurs in both male and female ferrets of any age. The calculi are generally composed of magnesium ammonium phosphate (struvite). They are frequently secondary to bacterial infection caused by agents such as Staphylococcus and Proteus as well as to a diet high in fiber. Jills may develop urolithiasis during pregnancy.

Clinical signs associated with urolithiasis include dysuria, hematuria and painful urination. Diagnosis is based on clinical signs, palpation of a large bladder, palpation of calculi, and radiographic or ultrasonographic evidence of calculi or crystals within the bladder.  In some cases crystals are visible in voided urine.  It is frequently difficult to catheterize either a male or female ferret that has a urinary tract obstruction. A tom cat catheter can be placed in male ferrets with urinary obstruction; however, it can be quite challenging. As an alternative an 18 gauge Teflon catheter may be placed as a urinary catheter. The catheter must be long enough to reach the bladder. Infusing lidocaine into the urethra and administering diazepam as a smooth muscle relaxant may help dilate the urethra to allow passage of the urinary catheter. A new ferret urethral catheter is produced by Cook Veterinary Products and is 3 fr rather than 3.5 fr as are tom cat catheters. These are more easily placed in ferret urethra. A tube cystostomy is indicated if a urethral catheter cannot be placed. The bladder is generally quite large and easy to palpate. A small incision is made to allow access to the bladder. A purse-string suture is placed in the wall of the bladder. A stab incision (1-2 mm) is made into the bladder wall allowing insertion of the urinary catheter. Be careful to control urine leaking into the abdomen. The bladder wall is sutured against the body wall to assure urine does not leak into the abdomen. The catheter is secured to the skin and the site managed as aseptically as possible. The catheter is connected to a closed urine collection system.

Cystotomy is indicated for removal of calculi and irrigation of the urethra. Standard approach and technique for cystotomy are used in ferrets. A ventral cystotomy is performed and calculi removed. The apex of the bladder should be inspected for the presence of diverticula which have been reported in ferrets. Culture of the bladder wall and culture and analysis of the calculi should be performed and appropriate antibiotic therapy administered. The bladder is closed in one layer of absorbable monofilament suture on an atraumatic needle.

Postsurgically the patient is placed on broad spectrum systemic antibiotics pending the results of urine culture. IV fluid diuresis is maintained for 24-48 hr posoperatively. The patient should be placed on a diet of primarily meat protein and no plant material. Urinary acidifiers are not recommended.


B.    Perineal Urethrostomy
Repeated urinary obstruction due to crystaluria in Hobs, despite appropriate medical management, can be treated palliatively with perineal urethrostomy. This procedure is NOT effective for urinary obstruction secondary to paraprostatic cysts where the obstruction is secondary to compression from the cyst as it will not relieve the obstruction. Cystotomy should be performed when calculi rather than crystals are the cause of obstruction.

Place the anesthetized ferret in a perineal stand and place a purse string suture in the anus. The urethrostomy site is located between the caudal aspect of the os penis and the pelvic urethra, about 1-2 cm ventral to the anus. Make a skin incision here and expose the base of the penis. Make a 1-1.5 cm incision in the penile urethra (facilitated by an indwelling 3.0 urethral catheter). Avoid the cavernous tissue on both side of the urethra. Laceration of this tissue causes marked hemorrhage. If an indwelling urinary catheter is not already present, one can be placed through the incised urethra at this time to drain the urinary bladder. Oppose the urethral mucosa to skin edges using 5-0 or 6-0 monofilament, nonabsorbable, simple interrupted sutures. Make the final opening at least 1cm long. Postoperative care includes antibiotics, IV fluids, analgesics and a collar, if possible, to prevent self-mutilation. Healing is usually uneventful with no long-term complications. Because of the fine sutures and delicate tissues it is best to perform suture removal under heavy sedation.

C.  Paraurethral or Prostatic Cysts
Male ferrets with adrenal neoplasia can develop prostatic enlargement, prostatitis, paraprostatic cysts, or paraurethral cysts. It is likely that this is a result of excessive quantities of hormones produced by the adrenal tumor. Treatment is aimed at surgical removal of the affected adrenal gland. Following removal of the adrenal neoplasia the prostate rapidly decreases in size often within as little as 1 or 2 days. In some ferrets with prostatic enlargement and paraprostatic cysts, the cystic structure may be as large or larger than the urinary bladder. These cysts frequently contain a tenacious green, often odoriferous material. This material is removed at the time of surgery; however, it is not necessary to marsupialize the cyst. Following removal of the adrenal neoplasia the cystic structure generally resolves rapidly.

Omentalization of the cyst is also very helpful especially if the cyst is large and causing urinary obstruction. A portion of the cyst wall is removed and submitted for culture and sensitivity. The contents are removed attempting to minimize contamination. The omentum is pulled caudally and sutured into the lumen of the cyst. Removing the contents decompresses the cyst and allows urine to flow. The omentum brings in vascular support to the cyst to help clear up any infection that might be present.  It is vital to make sure there is not defect in the urethra or urine will leak out the urethra, through the cyst and into the abdomen. If there is a urethral defect, an indwelling urinary catheter should be placed for 5-7 days to allow the urethra to heal before letting urine pass.

VI.    Miscellaneous Surgery
A.    Anal Sacculectomy
Most ferrets obtained from pet stores are descented so the average practitioner is rarely asked to perform this surgery.  Although it has been stated that castration can sufficiently control odor in ferrets, the anal sacs still accumulate very pungent material which they can express during periods of stress, excitement, or aggression.  Removal of the anal sacs does not truly descent the animal because the sebaceous glands in the skin will continue to produce a less odorous musk.  Animals are placed in the perianal stand position with the tail secured over the back.  Clip the area around the anus and place a purse string suture in the anus to prevent contamination of the surgical site with feces.  The area is prepared and draped for aseptic surgery.  The ducts of the anal sacs open at the 4 and 8 o’clock positions.   In the procedure described by Creed the opening of the duct is clamped to prevent leakage of the pungent anal sac contents during the surgery.  A small curved hemostat is placed on the exterior anal sac duct opening.  Make a 2 mm diameter circular incision around the duct.  Take care to avoid making the incision too deep.  Gently retract the hemostat in a dorsal direction and using a #15 or #11 scalpel blade, beginning at the duct opening dissect the anal sphincter muscle off the anal sac. The duct is about 2-3mm long and the sac is 10-20 mm long. The tissue around the duct is glandular in nature containing many perianal glands and appears tough and fibrous.  A plane of dissection cannot be readily established. As dissection is continued away from the anus, the wall of the anal sac appears smoother and whitish in color.  Care should be taken to avoid rupturing the sac, but if this occurs reposition the forceps to grab the edge of the sac where it was opened to control leakage and continue the dissection.  The sac lies within the internal and external sphincter muscles and the muscle fibers are carefully scraped off the white tissue of the anal sac.  Try to scrape as much muscle off the wall of the sacs as possible.  Continue to scrape and bluntly dissect (cotton tipped applicators work well for this dissection) the muscle fibers while putting outward traction on the duct.  Sometimes, a small blood vessel is attached to the distal portion of the gland.  It should be ligated and transsected.  After the sac has been removed, flush the cavity with sterile saline.  There is usually minimal bleeding.  The defect does not need to be closed, but the tissue may be apposed with loose sutures of an absorbable material to provide some tissue apposition.  If contamination of the surgical site occurs irrigate the area with sterile saline and administer a broad-spectrum antibiotic for 5-7 days.  
Complications are rare, but include excessive hemorrhage, postoperative infection or abscess formation, and fecal incontinence.  If the patient is incontinent postoperatively, owners should be advised that in most cases sphincter control returns as healing occurs and tissue swelling subsides.  Gentle tissue handling and careful dissection will keep complications to a minimum.

B.    Mammary Gland and Prepucial Masses
Mammary gland neoplasia is rare in ferrets. Benign mammary adenomas have been reported to occur most frequently in male ferrets, sometimes in conjunction with prepucial masses.  Mastectomy or lumpectomy of the mammary masses is usually curative. Prepucial orifice masses are also uncommon and may be adenomas or adenocarcinomas. Masses can cause partial urinary obstruction or may be incidental. Removal of these masses involves cosmetic and functional reconstruction of the prepucial orifice. Place skin-to-prepuce sutures using 4-0 or 5-0 suture material in a simple interrupted pattern.  With large masses, reconstruction can be challenging.  In some cases, penile amputation and urethrostomy may be indicated, especially in ferrets with adenocarcinomas.
Prognosis is excellent for adenomas of the prepuce and mammary gland. The outcome for carcinoma of the prepuce or mammary glands is guarded.

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