Extrahepatic Portosystemic Shunts In Dogs Research Articles

Outcomes in dogs with congenital extrahepatic portosystemic shunts treated with surgical ligation or medical management.

The objective of this study was to evaluate differences in outcomes in dogs treated for extrahepatic portosystemic shunts (EHPSS) by either complete suture ligation, partial suture ligation or medical management. This wasa retrospective, single institutional study. Dogs (n = 152) with EHPSS treated with suture ligation (n = 62), surgery with no ligation (n = 2), or medical management (n = 88). Medical records were reviewed for data on signalment, treatment variables, complications, and outcome. Kaplan-Meier plots were generated to assess survival across groups. Cox's proportional hazard models were used to assess the relationship between survival times and multiple predictor variables. For outcomes of interest, backwards, stepwise regression was performed (p < 0.05). Complete suture ligation was possible in 46/64 (71.9%) of dogs where surgical attenuation was attempted. One dog was euthanized following partial suture ligation due to suspected portal hypertension. Dogs with complete suture ligation of the EHPSS had a significantly longer median survival time (MST) compared to the medical management group (MST not reached vs. 1730 days [p < 0.001]). Complete resolution of clinical signs (without the need for further medical treatment or dietary changes) was achieved in 16/20 (80.0%) dogs with complete suture ligation and 4/10 (40.0%) dogs with partial suture ligation of their EHPSS. Suture ligation (complete or partial) for the treatment of EHPSS, where clinically possible, yielded the best clinical outcome and increased longevity compared to medical management in this study. While medical management for the treatment of EHPSS in dogs is a valid treatment option, better clinical outcomes are achieved with surgical intervention.

Short- and long-term outcomes of polyethylene band attenuation of congenital extrahepatic portosystemic shunts in dogs: 60 cases (2010-2020).

To report the short- and long-term outcomes following attenuation of congenital extrahepatic portosystemic shunts in dogs using a novel polyethylene band. Records were retrospectively reviewed for dogs that underwent congenital extrahepatic portosystemic shunt attenuation by a polyethylene banding technique, at a single institution between 2010 and 2020. Short-term outcome data were collected from peri-operative clinical records with follow-up examinations, scheduled at 6 and 18 weeks post-operatively, and post-operative imaging when performed. Long-term follow-up was collected by validated owner questionnaire, telephone interview or medical records. Long-term outcomes were categorised by "excellent", "good" or "poor". Sixty dogs were included. Post-operative complications occurred in 10 of 60 dogs (16.7%), four major and six minor, with a peri-operative mortality of 6.7%. Persistent shunting was identified in nine of 53 dogs (17%) available for follow-up examination and four dogs underwent a revision surgery. Long-term follow-up was available for 44 dogs at a median of 75 months post-operatively (range 7 to 128). Long-term outcomes were "excellent" (26) or "good" (8) in 81.8% of dogs and "poor" (8) in 18.2%. At the time of follow-up, 30 of 44 (68.2%) dogs were not receiving any medical treatment and 27 of 28 (96.4%) questionnaire respondents were satisfied with the response to surgery. Polyethylene band attenuation of congenital extrahepatic portosystemic shunts provides comparable outcomes to cellophane. The material used in this study is widely available and consistent while being pre-sterilised and pre-folded makes it easy to use.

Total lipid concentration of hairs increases after successful attenuation of extrahepatic portosystemic shunts in dogs.

Skin and coat quality can reflect nutritional deficiencies in humans and dogs with liver diseases. Determine skin and coat quality based on a scoring protocol and skin biopsies in dogs with an extrahepatic portosystemic shunt (EHPSS), and determine total lipid concentrations in hairs of dogs at time of surgery and 3 months after successful shunt closure. Ten client-owned dogs that underwent successful gradual attenuation of EHPSS, as defined by transsplenic portal scintigraphy, were included. A prospective cohort study was performed. All dogs underwent gradual attenuation of the EHPSS. Skin and coat scoring was performed at diagnosis, surgery, and 1 and 3 months postoperatively. Hair was plucked from the lumbar region for total lipid analysis and an 8 mm punch skin biopsy was taken at time of surgery and 3 months postoperatively, when the dogs underwent transsplenic portal scintigraphy to determine EHPSS closure. No significant differences were observed in skin and coat scoring over time. Total lipid concentrations of hairs increased significantly from surgery to 3 months postoperatively [30 μg/mg hair (13-56 μg/mg hair) to 47 μg/mg hair (25-63 μg/mg hair); p= 0.005]. Skin biopsies showed the presence of significantly more scales 3 months postoperatively (p= 0.018). A significant increase in total lipid concentrations in hairs suggests that successful surgical attenuation of EHPSS improves either intestinal absorption of lipids, fat metabolism in the liver, or a combination of both.

Use of an ameroid constrictor ring for gradual occlusion in canine congenital extrahepatic portosystemic shunts: Review

Congenital extrahepatic portosystemic shunts may be caused by embryological failure and are related to normal abdominal vascular development. They are noteworthy due to the higher prevalence of portosystemic vascular shunts and small to miniature breeds are the most affected. In this literature review, we carefully compiled in international articles in the field on the use of the ameroid constrictor ring in surgery for the gradual occlusion of unique congenital extrahepatic portosystemic shunts in dogs. In this sense, aspects of pathophysiology, etiopathogenesis, clinical symptoms and technical aspects regarding the surgical area were addressed. It is concluded that the use of the constrictor ring becomes a safe and highly recommended method, resulting in low rates of morbidity and mortality and prolonged postoperative survival in dogs.

Does surgical or medical management of extrahepatic portosystemic shunts in dogs carry a better prognosis for the resolution and reduction of neurological dysfunction?

PICO question&#x0D; In dogs with congenital extrahepatic portosystemic shunts that are treated with surgical attenuation what is the persistency, frequency, severity and outcome of neurological signs when compared to dogs that are treated medically?&#x0D; &#x0D; Clinical bottom line&#x0D; Category of research question&#x0D; Prognosis&#x0D; The number and type of study designs reviewed&#x0D; Ten papers were critically reviewed&#x0D; Strength of evidence&#x0D; Weak&#x0D; Outcomes reported&#x0D; For short-term success, owners reported an overall decrease in neurological signs associated with neurological dysfunction and an increase in quality of life after the initiation of either medical management or surgical management. Surgical management has a weak association with higher mortality or severe neurological signs in the immediate postoperative period&#x0D; Conclusion&#x0D; It is challenging to make a direct comparison between medical and surgical management but, overall, both strategies seemed to decrease neurological signs in the short term. There was a lack of evidence and available data about the efficacy of each for long-term control of neurological signs&#x0D; &#x0D; How to apply this evidence in practice&#x0D; The application of evidence into practice should take into account multiple factors, not limited to: individual clinical expertise, patient’s circumstances and owners’ values, country, location or clinic where you work, the individual case in front of you, the availability of therapies and resources.&#x0D; Knowledge Summaries are a resource to help reinforce or inform decision making. They do not override the responsibility or judgement of the practitioner to do what is best for the animal in their care.&#x0D; &#x0D;

Treatment of congenital extrahepatic portosystemic shunts in dogs: A systematic review and meta-analysis.

BackgroundSeveral options have been proposed for the treatment of congenital extrahepatic portosystemic shunts (cEHPSS) in dogs, but formal comparisons among different treatment options are currently unavailable. A previous evidence‐based review (2012) found low quality of evidence for papers assessing the treatment of cEHPSS in dogs.ObjectivesTo assess the quality of evidence available in the treatment of cEHPSS, summarize the current state of knowledge with respect to outcome after cEHPSS management, and compare different treatment techniques.AnimalsNot used.MethodsA bibliographic search was performed without date or language restrictions. Studies were assessed for quality of evidence (study design, study group sizes, subject enrollment quality, and overall risk of bias) and outcome measures reported (perioperative outcome, clinical outcome, and surgical or interventional outcome), all reported with 95% confidence intervals. A network meta‐analysis was performed.ResultsForty‐eight studies were included. Six retrospective studies (grade 4b) compared 2 techniques and 7 were abstracts (grade 5). The quality of evidence was low and risk of bias high. Regarding surgical outcome, statistically significant superiority of ameroid constrictor over thin film band was observed (P = .003). No other comparisons were statistically significant.Conclusions and Clinical ImportanceThe evidence base of choice of treatment of cEHPSS in dogs remains weak despite recent publications on the subject. Ameroid is superior to thin film band in causing EHPSS closure. Blinded randomized studies comparing different treatment modalities, which routinely include postoperative imaging to assess cEHPSS closure and acquired portosystemic shunt development are essential.

New perspectives on the development of extrahepatic portosystemic shunts.

In this essay we use clinical evidence and knowledge of anatomy to examine the relationship between blood flow and formation of congenital extrahepatic portosystemic shunts in dogs and cats. First we report on the clinical findings in a series of 50 dogs and 10 cats and then systematically review peer-reviewed data on the detailed anatomy of shunts in dogs and cats. In dogs four types of shunt: spleno-caval, left gastro-phrenic, left gastro-azygos and those involving the right gastric vein account for 94% of extrahepatic shunts. Cats also exhibit four types of shunt: spleno-caval, left gastrophrenic, left gastro-caval and left gastro-azygos, and the first three of these account for 92% shunts in this species. Our findings lead us to propose that preferential blood flow influences the subsequent formation of one of a number of defined and consistent congenital extrahepatic portosystemic shunts in dogs and cats.

Does hepatic steatosis have an impact on the short term hepatic response after complete attenuation of congenital extrahepatic portosystemic shunts? A prospective study of 20 dogs.

To evaluate the relationship between hepatic steatosis and increase in liver size and resolution of shunting after surgical attenuation of congenital extrahepatic portosystemic shunts in dogs. Prospective study. Dogs (n = 20) with congenital extrahepatic portosystemic shunts. Shunts were attenuated using ameroid ring constrictors. Portal blood flow and liver volume were evaluated using computed tomography before and ≥8 weeks after surgery. Hepatic steatosis was quantified by stereological point counting of lipid droplets and lipogranulomas (LG) in liver biopsies stained with Oil-red-O. Associations between steatosis and preoperative liver volume, liver growth after surgery, and development of acquired shunts were evaluated. Acquired shunts developed in 2 dogs (10%). Dogs with larger preoperative liver volumes relative to bodyweight had fewer lipid droplets per tissue point (P = .019). LG per tissue point were significantly associated with age: 0.019 ± 0.06 for dogs <12 months versus 0.25 ± 0.49 for dogs >12 months (P = .007). There was a significant positive association between liver growth after surgery and the number of LG/month of age in dogs >12 months (P = .003). There was no association between steatosis, presence of macrosteatosis, the number of LG or development of acquired shunts. This preliminary study suggests that the presence of hepatic lipidosis and LG has no demonstrable effect on development of acquired shunts or the magnitude of increase in liver volume after attenuation of congenital extrahepatic portosystemic shunts in dogs.

Evaluation ofIn VivoBehavior of Ameroid Ring Constrictors in Dogs with Congenital Extrahepatic Portosystemic Shunts Using Computed Tomography

To evaluate the in vivo pattern of ameroid constrictor closure of congenital extrahepatic portosystemic shunts in dogs. Prospective study. Dogs (n = 22) with congenital extrahepatic portosystemic shunts. Contrast-enhanced computed tomography was performed immediately before, and at least 8 weeks after placement of ameroid ring constrictors. Plastic-encased ameroid constrictors were used in 17 dogs and metal constrictors in 5 dogs. Presence of residual flow through the portosystemic shunt, additional anomalous vessels, acquired shunts and soft tissue associated with the ameroid constrictor was recorded. Postoperative internal diameter was recorded for the 17 plastic constrictors. Correlations between internal diameter and pre- and postoperative serum protein concentration were analyzed. No ameroid constrictor closed completely: shunt occlusion was always dependent on soft tissue within the ameroid ring. Residual flow through the shunt was present in 4 dogs (18%), although this caused persistent elevation of shunt fraction in only 1 dog (dog 8). The change in ameroid constrictor internal diameter was not significantly correlated with serum protein concentration. Complete shunt occlusion after AC placement is usually dependent on soft tissue reaction. Ameroid constrictors ≥5 mm diameter may not promote complete shunt occlusion.

Long‐term outcome after surgical ameroid ring constrictor placement for treatment of single extrahepatic portosystemic shunts in dogs

To report long-term clinical outcome in dogs treated for single congenital extrahepatic portosystemic shunt (CEHPSS) with a ameroid ring constrictor (ARC) and to identify perioperative variables associated with outcome. Retrospective, multi-institutional study. Dogs (n = 206) with CEHPSS. Medical records of dogs with CEHPSS treated by ARC were reviewed for perioperative and short-term (<1 month) data. Long-term follow-up information was obtained by telephone interview with referring veterinarians and/or owners. Kaplan-Meier analysis was used to estimate median survival time. Factors associated with short-term survival, outcome grade, and total survival time were identified. Fifteen dogs died <1 month after ARC placement. Follow-up data were obtained for 112 of 191 dogs that survived >1 month; median follow was 54 months (range, 1-175 months) and 103 (92%) dogs had no clinical signs. Estimated median survival time was 152 months. Variables significantly associated with short-term survival included being intact and a low total white blood cell (WBC) count. Variables significantly associated with a successful outcome included having surgery later in the study period and negative postoperative nuclear scintigraphy. In the long-term survival analyses, intact dogs and those with higher WBC counts and occlusion pressures and lower bile acid concentrations were more likely to survive. Dogs with CEHPSS treated by ARC generally have a good prognosis and prolonged postoperative survival.

Intravascular Occlusion for the Correction of Extrahepatic Portosystemic Shunts in Dogs

Congential extrahepatic portosystemic shunts (EHPSS) are common in dogs. An effective minimally invasive technique for correction of EHPSS could result in reduced morbidity, reduced costs, and reduced hospitalization times. Use of an intravascular occlusion device can effectively and safely result in acute complete occlusion of EHPSS in dogs. Seven dogs with naturally occurring EHPSS that presented to the Purdue University Veterinary Teaching Hospital. Prospective, clinical trial. The 7 dogs were consecutively enrolled over a 2-year period. Results of serum biochemistry, total serum bile acids, fasting plasma ammonia, abdominal radiography, and ultrasonography suggested the diagnosis of portosystemic shunts in all dogs. Definitive diagnosis of EHPSS was achieved with cranial mesenteric arterial portography and acute occlusion was attempted by the deployment of the Amplatzer vascular plug (AVP). EHPSS were identified in all dogs consisting of 5 portocaval and 2 portoazygous variants; 1/7 dogs (14%) were intolerant to temporary complete occlusion of the EHPSS. Of the remaining 6 dogs, 5 (83%) had complete occlusion of the EHPSS by the AVP. There were no complications and resolution of abnormal clinical signs and laboratory values was achieved in 4/5 (80%) dogs with complete occlusion. Intravascular correction of EHPSS by the AVP is a viable option to surgical correction while larger studies will be required to determine the clinical applicability of this procedure in the broader portosystemic shunt population.

Liver Size, Bodyweight, and Tolerance to Acute Complete Occlusion of Congenital Extrahepatic Portosystemic Shunts in Dogs

To investigate the relationship between preoperative liver size, bodyweight, and tolerance to shunt occlusion in dogs with congenital extrahepatic portosystemic shunt(s) (CPSS). Longitudinal cohort study. Dogs with CPSS (n=35). Ultrasonography was used to measure preoperative maximum transverse dimension of the liver (TS) of each dog. Intraoperative portal pressures were measured, before and after CPSS occlusion, via a jejunal vein catheter. Tolerance to shunt occlusion was judged on gross visceral observations, and on changes in portal pressure, central venous and mean arterial pressures. TS was significantly related to bodyweight (P<.05). Mean ratios for TS/bodyweight were calculated for dogs tolerant and intolerant of acute complete shunt occlusion. Dogs tolerant to occlusion had significantly higher TS/bodyweight ratios than dogs intolerant to occlusion (P=.025). Dogs with a TS/bodyweight ratio of >7 were more likely to tolerate CPSS occlusion than dogs with a TS/bodyweight ratio of <5 (P=.036). A model was generated to predict portal pressure rise after shunt occlusion, based on liver dimensions and bodyweight (R=0.668). Intestinal oxygenation did not correlate significantly with tolerance to CPSS occlusion (P=.29). In dogs with CPSS, liver size (relative to bodyweight) is significantly greater (P=.025) in dogs that are tolerant of full ligation than intolerant of occlusion. Preoperative measurement of bodyweight and liver size help indicate the likelihood of tolerance to acute complete occlusion of CPSS in dogs.

Use of transcolonic portal scintigraphy to evaluate efficacy of cellophane banding of congenital extrahepatic portosystemic shunts in 16 dogs

To evaluate the efficacy of cellophane banding of single congenital extrahepatic portosystemic shunts in dogs using transcolonic portal scintigraphy. To investigate the portal circulation of those dogs with elevated postoperative shunt fractions to determine the cause of the persistent shunting. Further, to evaluate whether presenting signs, clinical pathology findings and liver histopathology are predictive of outcome. Prospective study of 16 dogs presenting with single congenital extrahepatic portosystemic shunts. Dogs with single extrahepatic portosystemic shunts attenuated by cellophane banding underwent portal scintigraphy and bile acids tolerance testing pre- and post-operatively. Dogs identified with elevated shunt fractions at 10 weeks post-operatively underwent mesenteric portovenography. Qualitative hepatic histopathology from all dogs was reviewed by a veterinary pathologist and assigned a semi-quantitative score to identify any abnormalities that may predict surgical outcome. At 10 weeks post cellophane banding, 10 of 16 cases (63%) had normal shunt fractions, whilst six dogs (37%) had increased shunt fractions and seven dogs (44%) had increased serum bile acids. Of these dogs, mesenteric portovenography revealed incomplete closure of the shunt in three dogs (18.6%) and multiple acquired shunts in three dogs (18.6%). Liver histopathology findings were similar for all dogs, regardless of outcome. Cellophane banding is an efficacious method for complete gradual occlusion of single extrahepatic shunts when the shunt vessel is attenuated to < or = 3 mm. Transcolonic portal scintigraphy is a reliable method for assessment of shunt attenuation and, unlike serum bile acids, is not influenced by other causes of liver dysfunction.

Surgical management of congenital extrahepatic portosystemic shunts in dogs and cats

Surgical management of congenital extrahepatic portosystemic shunts in dogs and cats

Evaluation of cellophane banding with and without intraoperative attenuation for treatment of congenital extrahepatic portosystemic shunts in dogs

To evaluate the effect of intraoperative attenuation of congenital extrahepatic portosystemic shunts (CEPSSs) during cellophane banding procedures in dogs. Retrospective case series and prospective study. 18 cases evaluated retrospectively and 14 dogs evaluated prospectively. Gradual occlusion of CEPSSs was performed via cellophane banding. Shunts were occluded to a diameter < 3.0 mm during surgery in dogs prospectively enrolled in the partial attenuation group, whereas the shunt was not attenuated during surgery in dogs prospectively enrolled in the no-attenuation group or in dogs that had previously undergone surgery and were retrospectively evaluated. Postprandial serum bile acids (PPSBA) concentrations were measured before surgery and at various time points after surgery. Mean +/- SD PPSBA concentrations were 26.8 +/- 24.5 micromol/L at < 2.25 months after surgery (n = 16 dogs), 22.1 +/- 14.0 micromol/L from 2.25 to 6 months after surgery (12 dogs), and 34.9 +/- 32.5 micromol/L at > 6 months after surgery (22 dogs). In the prospectively enrolled dogs, mean PPSBA concentrations increased over time in dogs in the partial attenuation group, but not in dogs in the no-attenuation group. Cellophane banding may be used to occlude larger CEPSSs and may decrease the need for intraoperative monitoring of portal vein blood pressure. The technique may facilitate minimally invasive treatment of CEPSSs in dogs. Intraoperative attenuation of CEPSSs to a diameter < 3.0 mm is not necessary and may result in a less favorable outcome.

Evaluation of ameroid ring constrictors for treatment for single extrahepatic portosystemic shunts in dogs: 168 cases (1995–2001)

To evaluate use of an ameroid ring constrictor (ARC) for treatment for single extrahepatic portosystemic shunts (PSSs) and identify factors associated with postoperative death, continued portosystemic shunting, and long-term outcome in dogs. Retrospective study. 168 dogs with a single extrahepatic PSS. Medical records of dogs that had a single extrahepatic PSS and were treated with an ARC were reviewed. Signalment, history, clinical signs, results of preoperative blood analyses and portal pressure measurements, PSS location, ARC size, postoperative complications, and postoperative scintigraphy results were recorded. Owners were interviewed 6 months to 6 years after surgery. Results-Postoperative complications developed in 10% of dogs. Postoperative mortality rate was 7.1%. Predictive factors for postoperative death included high preoperative WBC count and postoperative complications. Twenty-one percent of dogs in which portal scintigraphy was performed 6 to 10 weeks after surgery had continued shunting. Predictive factors for persistent shunting included low preoperative plasma albumin concentration, high portal pressure after complete occlusion, and high portal pressure difference (postocclusion minus baseline). Clinical outcome in 108 dogs was classified as excellent (80%), good (14%), or poor (6%). Predictive factors for excellent long-term clinical outcome included high preoperative plasma albumin concentration, low preoperative leukocytosis, low portal pressure after complete occlusion, absence of postoperative seizures, and absence of continued shunting. Use of an ARC for treatment for a single extrahepatic PSS resulted in low morbidity and mortality rates. Certain preoperative factors were associated with increased risk of postoperative death, continued portosystemic shunting, and long-term outcome.

Ultrasonographic assessment of hemodynamic changes in the portal vein during surgical attenuation of congenital extrahepatic portosystemic shunts in dogs.

To determine portal hemodynamic changes associated with surgical shunt ligation and establish ultrasonographic criteria for determining the optimal degree of shunt narrowing and predicting outcome. Case series. 17 dogs, each with a single congenital extrahepatic portosystemic shunt. Pre- and postligation flow velocities and flow directions were determined by Doppler ultrasonography intraoperatively in the shunt and in the portal vein cranial and caudal to the shunt origin. Outcome was evaluated 1 month after surgery by measuring blood ammonia concentration and performing abdominal ultrasonography. Hepatofugal flow was detected in 9 of 17 dogs before shunt attenuation in the portal segment that was between the shunt origin and the entering point of the gastroduodenal vein. If hepatofugal flow became hepatopetal after shunt ligation, hyperammonemia resolved. Hepatofugal portal flow was caused by blood that flowed from the gastroduodenal vein toward the shunt. Shunt attenuation converted hepatofugal flow to hepatopetal in the shunt in 12 of 17 dogs. Chronic portal hypertension developed or perioperative death occurred when the portal congestion index caudal to the shunt origin increased by > 3.6 times. After hepatopetal flow in the cranial portal vein and the shunt is established, further shunt narrowing is contraindicated. Increase of the portal congestion index caudal to the shunt > 3.5 times should be avoided. Poor outcome because of severe hypoplasia of the portal branches can be expected if the flow direction remains hepatofugal after shunt occlusion cranial to the shunt origin.

Outcomes after extrahepatic portosystemic shunt ligation in 49 dogs.

To evaluate outcomes after attenuation of extrahepatic portosystemic shunts in dogs using surgical silk. Retrospective study. Case records were reviewed for degree of surgical attenuation, experience of the primary surgeon, perioperative mortality and problems related to persistent portosystemic shunting or shunt ligation. Presence of portosystemic shunting after surgery was evaluated by ammonia tolerance testing, measurement of postprandial serum bile acid, plasma urea and cholesterol concentrations and liver enzyme activity. The influence of age, postocclusion portal pressure, primary surgeon, degree of attenuation and postoperative biochemical findings on the occurrence of postoperative problems was assessed. The mortality rate was 2.1%. Shunt attenuation was complete in 34% and partial in 66% of dogs. Portal hypertension necessitating ligature removal was encountered in only one dog. Five dogs experienced neurological abnormalities (seizures or ataxia), possibly as a manifestation of 'postligation seizure syndrome'. Postoperative liver function was normal in 78% of dogs, including 70% with partial shunt attenuation. Experience of the surgeon was related positively to outcome after partial attenuation (P = 0.002). Postoperative biochemical evidence of abnormal liver function was the most sensitive predictor of recurrence of clinical signs referable to persistent portosystemic shunting. In the hands of an experienced surgeon, surgical attenuation of single extrahepatic shunts was safe and effective, even in animals with partial attenuation. Most dogs with biochemical evidence of persistent shunting suffer relapse of clinical signs within 18 months of surgery. Postligation neurological syndromes of variable intensity may be more common than previously thought.

Experimental evaluation of four methods of progressive venous attenuation in dogs.

To determine the most effective and reliable method for progressive attenuation of single extrahepatic portosystemic shunts in dogs. The effects of the four treatments on femoral vein diameter and histology were compared with controls. Fourteen healthy adult dogs. 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. 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. 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. 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.

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.