Experimental evaluation of four methods of progressive venous attenuation in dogs

OBJECTIVE: To determine the most effective and reliable method for progressive attenuation of single extrahepatic portosystemic shunts in dogs. STUDY DESIGN: The effects of the four treatments on femoral vein diameter and histology were compared with controls. ANIMALS: Fourteen healthy adult dogs. METHODS: Twenty-eight canine femoral veins were subjected to sham surgery (4), partial attenuation using silk (5), cellophane banding (6), ameroid constrictor implantation (5), and intravascular thrombogenic coils (8). Changes in vein diameter were evaluated at weekly intervals using venography. After 6 weeks, the dogs were humanely euthanatized, and histopathology was performed on the femoral veins. RESULTS: Only cellophane and ameroid constrictors produced progressive and permanent vein attenuation. Ameroid constrictors produced complete occlusion within 14 days in four of five veins and by 21 days in the fifth vein. Cellophane banding produced slow progressive (but not complete) attenuation in five of six veins. Complete occlusion was demonstrated in four of eight veins after thrombogenic coil implantation; however, recanalization occurred in all but one dog. Perivascular silk did not produce significant progressive attenuation. CONCLUSIONS: Ameroid constrictors produced rapid occlusion of femoral veins. Cellophane banding resulted in slower attenuation. Thrombogenic coils produced attenuation, but this was not sustained in many cases. Silk did not promote ongoing attenuation. CLINICAL RELEVANCE: Both ameroid constrictor implantation and cellophane banding show promise for progressive attenuation of single extrahepatic portosystemic shunts in dogs. Because rapid occlusion was seen with ameroid constrictors, however, cellophane banding maybe a safer technique in animals with increased hepatic vascular resistance. Further evaluation of both treatments in clinical cases is warranted.     

Re-evaluation of a portocaval venograft without an ameroid constrictor as a method for controlling portal hypertension after occlusion of intrahepatic portocaval shunts in dogs

OBJECTIVE: To evaluate the use of a portocaval venograft without an ameroid constrictor in the surgical management of intrahepatic portosystemic shunts (PSS). STUDY DESIGN: Prospective clinical study. ANIMALS: Seven dogs with intrahepatic PSS. METHODS: Portal pressure was measured after temporary suture occlusion of the intrahepatic PSS. In dogs with an increase in portal pressure > or =8 mm Hg or signs of portal hypertension, a single extrahepatic portocaval shunt was created using a jugular vein. Clinical outcome and complications were recorded. RESULTS: The mean (+/-SD) portal pressure increased from 5.9+/-1.6 to 17.9+/-4.1 mm Hg with PSS occlusion. There were no intraoperative complications and, after creation of the portocaval shunt, the intrahepatic PSS could be completely ligated in all dogs. The final portal pressure was 9.6+/-1.9 mm Hg. Complications developed during postoperative hospitalization in 5 dogs and included incisional discharge (4 dogs), ascites (3), ventricular premature contractions (2), and melena, bloody diarrhea, neurologic signs, coagulopathy, and aspiration pneumonia (each in 1 dog). Six dogs died or were euthanatized with clinical signs related to depression, inappetance, abdominal pain, vomiting, melena, and abdominal distention, with a median survival of 82 days (range, 20-990 days). One dog was clinically normal at 33 months after surgery. CONCLUSIONS: Clinical signs observed in 6 dogs after surgery were consistent with portal hypertension. Use of a portocaval venograft without an ameroid constrictor may reduce the likelihood of hepatic vascular development, thereby increasing the risk of life-threatening portal hypertension should the venograft suddenly occlude. CLINICAL RELEVANCE: Use of a portocaval venograft without an ameroid constrictor to control portal hypertension after ligation of an intrahepatic PSS cannot be recommended.     

Gradual Occlusion of Extrahepatic Portosystemic Shunts in Dogs and Cats Using the Ameroid Constrictor

Gradual occlusion of the splenic vein, using a specialized device (ameroid constrictor), was evaluated experimentally in three normal beagle dogs. Splenoportograms were used to verify that total occlusion of the splenic vein had occurred in all dogs within 4 to 5 weeks after application of the device. The ameroid constrictor (AC) was also evaluated as a method of gradual vascular occlusion in 12 dogs and two cats with single, extrahepatic, portosystemic shunts (PSS). Serum bile acid (SBA) concentrations were measured and portal scintigraphy (PS) was performed on all 14 animals preoperatively and 10, 20, 30, and 60 days postoperatively. Two dogs (14%) died from portal hypertension in the early postoperative period. One dog and one cat developed multiple acquired PSS, confirmed by mesenteric portography 90 days after the operation. Portal scintigraphy confirmed total occlusion of the primary shunt in the other 10 animals. Shunt fractions (SF), as measured by PS on postoperative days 30 and 60, declined significantly from preoperative values. Significant decreases were noted between preoperative and postoperative values for preprandial SBA on postoperative day 60 and for postprandial SBA on postoperative day 30. SBA concentrations did not correlate with SF. Based on this study, gradual vascular occlusion using the AC is recommended as a method for treatment of single, extrahepatic, PSS.     

Surgical management of left-divisional intrahepatic portosystemic shunts: outcome after partial ligation of, or ameroid ring constrictor placement on, the left hepatic vein in twenty-eight dogs (1995-2005)

OBJECTIVES: To evaluate outcome in dogs with left divisional intrahepatic portosystemic shunts (PSS) treated by partial ligation (PL) or ameroid ring constrictor (ARC) placement on the left hepatic vein. DESIGN: Retrospective study. ANIMALS: Dogs (n=28) with left divisional intrahepatic PSS. METHODS: Retrieved data from medical records of dogs with left divisional intrahepatic PSS that had PL (n=17) or ARC (n=11) were signalment, history, clinical signs, preoperative blood work, portal pressure measurements, ARC size, complications and postoperative technetium scintigraphy. Outcome assessed by owner interview 6 months-10 years after surgery was classified as excellent, good or poor. Differences were tested by exact chi2 test. RESULTS: Major complications occurred in 3 dogs: coagulopathy (1 PL dog died), ascites (1 PL dog survived) and seizures (1 ARC dog died). Eight PL dogs had technetium portal scintigraphy; 1 dog was negative and 7 dogs positive for persistent shunting. Seven ARC dogs had scintigraphy; 4 dogs were negative and 3 positive for persistent shunting. In PL dogs, long-term clinical outcome was excellent (92%) or good (8%) whereas, in ARC dogs it was excellent (20%), good (50%) or poor (30%). This outcome difference between treatment groups was significant (P=.0012). CONCLUSION: Dogs treated by PL had significantly better long-term outcome compared with ARC treated dogs. CLINICAL RELEVANCE: Based on these data, ARC placement on the left hepatic vein in dogs with left-divisional intrahepatic PSS cannot be recommended.     

Perioperative outcomes after three different single extrahepatic portosystemic shunt attenuation techniques in dogs: partial ligation, complete ligation and ameroid constrictor placement

OBJECTIVE: To compare the perioperative outcomes of single extrahepatic portosystemic shunt occlusion by complete and partial silk ligation and ameroid constrictor placement in dogs. DESIGN: A retrospective analysis of 30 dogs with single congenital extrahepatic shunts. PROCEDURE: Records between 1990 and 2000 were reviewed. Patient age, breed, weight, presenting clinical signs, clinical pathology results, diagnostic imaging results, the surgery procedure performed, implant used, time taken, intra operative complications and perioperative complications were recorded. Mortality rates were calculated. RESULTS: Twenty dogs had a silk ligation procedure, 10 partially occluded and 10 completely. Ten dogs had an ameroid constrictor placement procedure. Ameroid constrictor surgery was significantly shorter in duration than silk ligation. Time for silk ligation was 91.8 +/- 35.2 minutes (median 90.0); time for ameroid constrictor placement was 71.5 +/- 12.0 (median 72.5, P = 0.049). A reduction in intraoperative complications was also noted in the ameroid constrictor surgery group. CONCLUSION: The ameroid constrictor offered a surgical occlusion procedure of single extrahepatic portosystemic shunts in dogs that was clinically as effective as silk ligation in the perioperative period, with a significantly shorter surgery time.     

ULTRASONOGRAPHIC DIAGNOSIS OF PORTAL VEIN THROMBOSIS IN FOUR DOGS

Ante mortem diagnosis of portal vein thrombosis was determined ultrasonographically in four dogs. In each dog the thrombus was visible in two-dimensional, grey-scale images of the portal vein obtained through a right intercostal window. Duplex-Doppler measurements and color-Doppler images provided information about the effects of thrombosis on portal blood flow. Reduced portal blood flow compatible with portal hypertension was detected in three dogs. A hypercoagulable state was probably involved in the pathogenesis of portal vein thrombosis in two dogs, one with pancreatitis and gastrointestinal blood loss and another with protein-losing nephropathy and probable immune-mediated anemia. The third dog had chronic ehrlichiosis; thrombosis was probably secondary to vasculitis. The remaining dog had thrombosis secondary to invasion of the portal vein by a recurrent duodenal neoplasm. This dog was euthanized because the tumor was considered inoperable. The dog with pancreatitis developed acute portal hypertension due to obstruction of the portal vein by the thrombus and was euthanized. The dogs with protein-losing nephropathy and ehrlichiosis were treated medically and recovered. Although portal vein thrombosis is uncommon, this complication should be considered in dogs with a variety of abdominal or systemic disorders. Ultrasonography is a practical method for diagnosis of portal vein thrombosis and detection of the underlying cause.     

Transportal Approach for Attenuating Intrahepatic Portosystemic Shunts in Dogs

A novel surgical approach, using portal venotomy during total hepatic vascular occlusion, was used to locate and attenuate congenital intrahepatic portosystemic shunts in nine dogs. Shunt location was consistent with a persistent ductus venosus in only two dogs. In the remaining seven dogs the shunts were window-like orifices arising from either the left (two dogs) or right portal vein branch (five dogs) and communicating with the ipsilateral hepatic vein or caudal vena cava. The transportal approach using total hepatic vascular occlusion consistently provided good access to the portosystemic shunts, including those with window-like communications. A 7 to 16 minute period of total vascular occlusion was well-tolerated hemodynamically, with few intraoperative complications. Intrahepatic shunts were successfully attenuated in eight dogs, while one dog with portal atresia was euthanatized. The postoperative course was complicated by high protein pulmonary edema (one dog), an encapsulated biliary pseudocyst (one dog) and uncontrollable hemorrhage caused by an uncharacterized coagulopathy (one dog). Three dogs required a second operation to further attenuate their shunts. The clinical condition of all seven surviving dogs was improved after surgery.     

Thoracoscopic visualization and ligation of the thoracic duct in dogs

OBJECTIVE: To develop a technique for thoracoscopic visualization and ligation of the thoracic duct in dogs. STUDY DESIGN: In vivo experimental study. ANIMALS: Five mature, healthy dogs. METHODS: Dogs were normal based on physical examination, negative occult heartworm test, normal complete blood count and biochemical profile, and normal thoracic radiographs. The dogs were anesthetized, and a ventral midline laparotomy was performed for catheterization of a mesenteric lymphatic. Lymphangiography was performed to determine thoracic duct anatomy. Thoracoscopy was performed in the caudal, right hemithorax after single lung intubation or bronchial blockade. At least two 10-mm clips were placed across the thoracic duct in each dog. Lymphangiography was repeated to assess duct ligation. If complete duct occlusion was not achieved, thoracoscopy was repeated for additional clip placement. After surgery the dogs were euthanatized, and necropsies were performed. RESULTS: Lymphangiography showed that multiple branches of the thoracic duct were present in every dog; bilateral thoracic duct branches were most common. Thoracoscopic identification and ligation of the thoracic duct was successful in all five dogs. Two dogs required a second thoracoscopic procedure to completely occlude flow of contrast through the thoracic duct. Surgery time for thoracoscopy averaged 59 plus minus 9.6 minutes. Retroperitoneal contrast accumulation after thoracic duct ligation occurred in two dogs. One dog required bilateral pulmonary ventilation. CONCLUSION: Thoracoscopy can be used to visualize the thoracic duct for ligation in normal dogs. CLINICAL RELEVANCE: Thoracoscopic ligation of the thoracic duct may be a therapeutic option for management of chylothorax in dogs.     

Outcome of ameroid constrictor occlusion of single congenital extrahepatic portosystemic shunts in cats: 12 cases (1993-2000)

OBJECTIVE: To determine postoperative (< or = 6 days), short-term (< or = 90 days), and long-term (> or = 6 months) outcomes of cats undergoing ameroid constrictor occlusion of single congenital extrahepatic portosystemic shunts (PSS) and identify factors associated with outcome. DESIGN: Retrospective study. ANIMALS: 12 cats. PROCEDURE: Cats with single congenital PSS that underwent surgical placement of ameroid constrictors were identified. Follow-up information was obtained through telephone interviews and facsimile correspondence with referring veterinarians and owners. Results-All cats survived the surgery and were discharged from the hospital. One cat had seizures during the postoperative period. Five cats were clinically normal during follow-up evaluations within 90 days after the surgery. Long-term follow-up information was available for 9 cats. Three were clinically normal, 4 had been euthanatized because of progressive neurologic disease, and 2 had neurologic abnormalities that could not be controlled with medication. Four of 7 cats with continued or recurrent neurologic abnormalities 1 or more months after surgery had normal scintigraphic or hepatic function test results 2 to 6 months after surgery. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that the long-term outcome of ameroid constrictor occlusion of PSS in cats is poor. Owners of older cats and cats with preexisting neurologic signs should be made aware of the potential for a poor outcome when considering surgical correction of this disease.     

Evaluation of a portocaval venograft and ameroid ring for the occlusion of intrahepatic portocaval shunts in dogs

OBJECTIVE:To evaluate the use of a portocaval venograft and ameroid constrictor in the surgical management of intrahepatic portosystemic shunts (PSS). STUDY DESIGN: Prospective, clinical study. Animal Population: Ten client-owned dogs with intrahepatic PSS. METHODS: Portal pressure was measured after temporary suture occlusion of the intrahepatic PSS. In dogs with an increase in portal pressure greater than 8 mm Hg, a single extrahepatic portocaval shunt was created using a jugular vein. An ameroid ring was placed around the venograft and the intrahepatic PSS was attenuated. Transcolonic pertechnetate scintigraphy was performed before surgery, 5 days after surgery, and 8 to 10 weeks after surgery. Dogs with continued portosystemic shunting were evaluated further by laparotomy or portography. Clinical outcome and complications were recorded. RESULTS: Mean (+/- SD) portal pressure increased from 6 +/- 3 to 19 +/- 6 mm Hg with PSS occlusion; in all 10 dogs, the increase in portal pressure was greater than 8 mm Hg. There were no intraoperative complications, and, after creation of the portocaval shunt, the intrahepatic PSS could be completely ligated in 8 of 10 dogs. The final portal pressure was 9 +/- 4 mm Hg. Postoperative complications included coagulopathy and death (1 dog), ascites (3 dogs), and incisional discharge (3 dogs). Five of 8 dogs had continued portosystemic shunting at 8 to 10 weeks after surgery. Multiple extrahepatic PSS were demonstrated in 4 of these dogs. Clinical outcome was excellent in all 9 surviving dogs. CONCLUSIONS AND CLINICAL SIGNIFICANCE: The surgical technique resulted in a high incidence of multiple extrahepatic PSS. Short-term clinical results were promising, but long-term outcome must be evaluated further.     

192iridium brachytherapy, using an intracavitary afterload device, for treatment of intranasal neoplasms in dogs.

After surgical removal of a primary intranasal neoplasm, an implant device, designed to deliver 192iridium (192Ir) brachytherapy, was positioned in the nasal cavity of 8 dogs. Ribbons containing 192Ir seeds were placed in the device, using an afterloading technique. Dosimetry, to a dose of 7,000 to 10,000 centiGray (cGy), was calculated to encompass the site previously occupied by the tumor and a 1-cm margin of surrounding normal tissue. The quantity of 192Ir implanted varied between 16.69 and 100.80 mg of radium equivalent. The duration of implantation ranged from 90 to 168 hours. All dogs tolerated the implant well, but had a mucoid nasal discharge after radiotherapy. The implant device allowed rapid application and removal of the radioactive ribbons. Mean (+/- SD) radiation exposure to each radiotherapist during seed loading and unloading was 14.4 (+/- 5.3) and 4.5 (+/- 0.9) mrem, respectively. A uniform dose distribution around the intranasal implant device was achieved; however, dogs that received doses in excess of 9,400 cGy at the dorsolateral surface of the nose and/or hard palate had bone and soft tissue necrosis between 70 and 120 days after treatment. One dog was euthanatized 50 days after treatment because of metastatic disease, and 2 dogs were euthanatized because of local tumor recurrence at 125 and 212 days. Death, considered unrelated to treatment, occurred in 1 dog that was euthanatized 27 days after treatment and in 3 dogs that died 30, 93, and 456 days after treatment. Necropsy was performed on 3 of these dogs and evidence of intranasal neoplasia was not observed. One dog remained disease-free at 587 days after treatment.     

Nontraumatic rupture of an adrenal gland tumor causing intra-abdominal or retroperitoneal hemorrhage in four dogs

Diagnosis and surgical management of intra-abdominal or retroperitoneal hemorrhage in 4 dogs with rupture of an adrenal gland tumor were determined. All 4 dogs were lethargic and weak with pale mucous membranes on initial examination. Three dogs did not have any history of clinical signs of hyperadrenocorticism or pheochromocytoma prior to examination. In 3 of the dogs, a mass in the area of the adrenal gland was identified with ultrasonography prior to surgery. All dogs developed ventricular premature contractions before or during anesthesia. Three dogs survived adrenalectomy; 1 dog was euthanatized during surgery because of an inability to achieve adequate hemostasis. The remaining 3 dogs all survived more than 5 months after surgery; 1 was euthanatized 9 months after surgery because of rupture of a hepatic mass. On the basis of these results, we suggest that hemodynamic stabilization followed by adrenalectomy is the treatment of choice for dogs with nontraumatic rupture of an adrenal gland tumor and resulting life-threatening hemorrhage.     

A Method for Controlling Portal Pressure After Attenuation of Intrahepatic Portacaval Shunts

Two dogs had right divisional intrahepatic portacaval shunts within the right lateral lobe of the liver. In both dogs, an extrahepatic portacaval vascular anastomosis was created, using an autologous right external jugular vein graft. The intrahepatic shunts were completely attenuated using a prehepatic intravascular caval approach. The creation of the vascular graft allowed postattenuation rises in portal pressure to be controlled, preventing the development of life threatening portal hypertension. Both dogs recovered from the procedure. One dog is clinically normal and does not require medication (8 months postoperatively); the other dog was euthanatized 5 months after surgery because of renal failure. Scintigraphy studies, performed before surgery, showed significant shunting of portal blood away from the liver (shunt indices 65% and 59%), whereas, similar studies done 4 weeks afterwards showed almost normal portal blood flow (shunt indices 16% and 18%, respectively).     

Kidney graft survival in transfused and nontransfused sibling beagle dogs

In 6 pairs of sibling Beagle dogs, 1 kidney was exchanged between pairs, and contralateral nephrectomy was done. Previously, one dog of each pair was given blood transfusions from the donor of its allograft. All dogs were given azathioprine and prednisone postoperatively for immunosuppression. Four of 6 dogs given pretransplantation transfusions were healthy 1 year after surgical manipulation was done, and 2 died for reasons other than graft rejection. Of the 6 dogs that were not given pretransplantation transfusions, 3 were healthy after 1 years, but 2 were euthanatized because of graft rejection, and the last was euthanatized because of both graft rejection and intussusception. Other complications in these dogs were leukopenia (7 dogs), interdigital abscesses (2 dogs), urinary infection (3 dogs), and renal vein thrombosis (1 dog). Considering the lack of alternative methods for effective therapy for chronic renal failure in dogs, results of this study seem encouraging for selective use of renal transplantation, clinically. This study supports previous reports which indicated that pretransplantation transfusion enhanced graft survival in dogs.     

Effect of petrolatum coating on the rate of occlusion of ameroid constrictors in the peritoneal cavity

OBJECTIVE : To document rate of closure and degree of inflammation associated with petrolatum coated (PCA) and non-coated ameroid constrictors (NCA) in the peritoneal cavity. STUDY DESIGN : Experimental study. ANIMALS : 18 Sprague-Dawley rats. METHODS : Thirty-six ameroid constrictors (AC; 5 mm) were digitally scanned and luminal area measured. Rats were anesthetized, and 1 PCA and 1 NCA were inserted in the peritoneal cavity by median celiotomy. Rats were euthanatized at 2 weeks (6 rats), 4 weeks (6), or 6 weeks (6) after surgery. AC were harvested, digitally scanned, and luminal area determined. Inflammation associated with the AC was subjectively graded (1-5). The effects of petrolatum coating on luminal area measurements and inflammatory score were statistically analyzed. RESULTS : Closure of AC occurred most rapidly during the first 2 weeks, but luminal area decreased only 32% at 6 weeks after implantation. There was no significant difference in rate of closure for PCA compared to NCA at 2, 4, or 6 weeks. Inflammation scores were not significantly different between PCA and NCA. CONCLUSIONS : Petrolatum coating did not slow the rate of closure of AC in the peritoneal cavity. CLINICAL RELEVANCE : The lack of closure of AC supports the conclusion that vascular attenuation is not dependent on luminal constriction alone. Petrolatum coating did not slow the rate of casein expansion and is unlikely to be clinically useful.     

Repair of urethral defects using fascia lata autografts in dogs

OBJECTIVE: To evaluate the feasibility of urethroplasty using a free fascia lata (FL) graft in the dog. STUDY DESIGN: In vivo experimental study. ANIMALS: Mixed-breed dogs (n=14). METHODS: Half of the circumference of the urethra, approximately 1.5 cm long, was excised in 14 male dogs to induce a urethral defect. FL (approximately 2 cm x 2 cm) harvested from the lateral thigh was sutured to the urethra using a 3-0 polyglactin 910 continuous pattern. Dogs were monitored daily for bladder distention and had urethral catheters until normal voiding was observed. On day 60, each dog had a positive contrast urethrogram, and then 8 dogs were euthanatized for gross and histologic examination. Six dogs were monitored for urologic problems for 6 months, and a positive contrast urethrogram was repeated. RESULTS: All dogs recovered successfully; 4 dogs had difficulty voiding for 2-3 days and urine was aspirated from these dogs every 3 hours until signs of painful urination disappeared. On positive contrast urethrograms, urethral anatomy was considered normal except in 4 dogs that had an irregular contour. Gross urethral examination confirmed an absence of ulceration, stricture, diverticula, or fistula formation, and the FL-lined graft survived in all dogs. No degenerative and reparative responses were observed. On histologic examination of the penile urethra, the lumen was intact, covered with transitional epithelium, and surrounded by corpus spongiosum with cavernous spaces and blood-filled vessels. CONCLUSIONS: Free FL grafts are incorporated satisfactorily and would appear to be useful for repairing urethral defects. CLINICAL RELEVANCE: FL grafts should be considered for repair of urethral defects in dogs.     

Transarterial ductal occlusion with the Amplatzer vascular plug in 31 dogs

Background: Transarterial ductal occlusion with the Amplatzer vascular plug was first reported in dogs by Hogan et al in 2005. Hypothesis: Use of the Amplatzer vascular plug is a safe, efficacious method of patent ductus arteriosus (PDA) occlusion. Animals: Thirty‐one client‐owned dogs with PDA. Methods: Records of 31 dogs in which transarterial occlusion of PDA with an Amplatzer vascular plug was attempted were reviewed. Results: All dogs had a type II PDA, with 27 dogs having type IIA morphology and 4 dogs having type IIB morphology. Appropriate device deployment was achieved in 29 of 31 dogs. Postdeployment angiography in 21 dogs documented complete occlusion in 10 dogs, trivial residual flow in 5 dogs, mild residual flow in 2 dogs, moderate residual flow in 3 dogs, and severe residual flow in 1 dog. Transthoracic color Doppler echocardiography documented complete occlusion in 22 dogs, whereas 2 dogs had trivial residual flow, 2 dogs had mild residual flow, 2 dogs had mild to moderate residual flow, and 1 dog had severe residual flow. Of the 7 dogs with residual flow, 2 had complete occlusion 2–4 months postoperatively, 1 had moderate residual flow 1 month postoperatively, and 4 were lost to follow‐up. One dog required a larger device than was able to be deployed through the largest sheath placed in the femoral artery. Pulmonary embolization of the device occurred in 1 dog. Conclusion: We conclude that ductal occlusion with an Amplatzer vascular plug is a safe and efficacious therapy for PDA in dogs.     

Transvenous retrograde portography for identification and characterization of portosystemic shunts in dogs

Transvenous retrograde portography for identification and characterization of portosystemic shunts in dogs A method for transvenous retrograde portography (TRP) in dogs suspected to have a portosystemic shunt (PSS) and results in 20 dogs are described. For TRP, dogs were anesthetized and positioned in left lateral recumbency A dual-lumen balloon-tipped catheter was inserted into the right jugular vein and advanced into the azygos vein. The balloon was inflated to occlude the azygos vein, and contrast material was injected during fluoroscopic evaluation. The catheter was then positioned in the caudal vena cava just cranial to the diaphragm. The balloon was again inflated to occlude the vena cava, and contrast material was again injected. Once a shunt was identified, selective catheterization was attempted with a guide wire and angled catheter. A PSS was identified in 18 of the 20 dogs. In 10 of the 18, the shunt vessel could be selectively catheterized, allowing measurement of portal pressures while the shunt was occluded with the balloon. In 1 dog, results of TRP were normal, but subsequent exploratory celiotomy revealed a single extrahepatic PSS, which was surgically attenuated. The other dog in which results of TRP were normal did not have a macroscopic PSS. In dogs suspected to have a PSS, TRP may be a useful adjunctive diagnostic test that is less invasive than operative mesenteric vein portography and allows measurement of portal pressures before and after temporary shunt occlusion.     

Microemulsified cyclosporine-based immunosuppression for the prevention of acute renal allograft rejection in unrelated dogs: preliminary experimental study

OBJECTIVES: To determine whether the microemulsified formulation of cyclosporine (MCsA; Neoral; Novartis A.G.), combined with azathioprine (Imuran; Glaxo Wellcome), and prednisolone (Delta-Cortef; Upjohn), would be effective in preventing acute renal allograft rejection in unrelated mongrel dogs. To document any toxic effects associated with this drug combination. STUDY DESIGN: rospective, pilot study. ANIMALS: Four healthy, adult, mongrel, canine renal allograft recipients. METHODS: Heterotopic renal transplantation, with bilateral nephrectomy, was performed in 4 dogs. Allografts were harvested from 2 unrelated dogs that were to be euthanatized for reasons unrelated to this study. The dogs were treated for 100 days or until signs of illness or allograft rejection required euthanasia. Microemulsified cyclosporine (20 mg/kg/day), azathioprine (5 mg/kg every other day), and prednisolone (1 mg/kg/day) were administered for the prevention of acute rejection. Body weight, serum biochemistry profiles, complete blood counts, and trough whole-blood cyclosporine concentrations were measured throughout the study. Cyclosporine dose was adjusted to maintain a trough concentration of 400-500 ng/mL. Azathioprine dose was decreased if evidence of hepatotoxicity developed or if the total blood white cell count was <4,000 cells/micro L. The prednisolone was tapered by 0.25 mg/kg increments every 3 weeks and discontinued 14 days before the end of the study in the surviving dogs. Complications were recorded. A complete necropsy and histopathologic examination were performed in each recipient. RESULTS: Two of the 4 dogs survived the 100-day period. One dog was euthanatized at 8 days because of an intestinal intussusception. One dog was euthanatized at 64 days because of a severe upper respiratory infection. At the time of death, these 2 dogs had plasma creatinine concentrations of 1.5 and 2.6 mg/dL, respectively, with no histopathologic evidence of allograft rejection. All dogs had transient weight loss (range, 4.6%-17.7% of preoperative body weight) between days 7 and 14. Two dogs had evidence of hepatotoxicity. The 2 dogs surviving to 100 days had normal serum creatinine concentrations and no clinical signs of rejection. One of these dogs had evidence of a grade IIa acute/active rejection based on the modified BANFF 97 histopathologic classification. The second dog had no evidence of rejection or inflammation within the allograft. CONCLUSIONS: This preliminary experimental study shows that immunosuppression using MCsA, combined with azathioprine and prednisolone, may be effective in preventing acute renal allograft rejection in unrelated mongrel dogs for 100 days. Complications included ileocolic intussusception, upper respiratory infection, weight loss, and transient hepatotoxicity. CLINICAL RELEVANCE: Immunosuppression using MCsA, azathioprine, and prednisolone may be effective in preventing acute renal allograft rejection in unrelated, mongrel dogs. This triple drug protocol is cost-effective and was easy to administer. Further investigation is warranted to minimize toxic effects and to determine the efficacy of prophylactic renal biopsies to detect and treat subclinical acute/active rejection.