Methods of Gradual Vascular Occlusion and Their Applications in Treatment of Congenital Portosystemic Shunts in Dogs: A Review

Congenital Portosystemic Shunts in Dogs and Cats: Treatment, Complications and Prognosis

Congenital portosystemic shunts (CPSS) are a common vascular anomaly of the liver in dogs and cats. Clinical signs of CPSS are non-specific and may wax and wane, while laboratory findings can raise the clinical suspicion for CPSS, but they are also not specific. Definitive diagnosis will be established by evaluation of liver function tests and diagnostic imaging. The aim of this article is to review the management, both medical and surgical, complications, and prognosis of CPSS in dogs and cats. Attenuation of the CPSS is the treatment of choice and may be performed by open surgical intervention using ameroid ring constrictors, thin film banding, and partial or complete suture ligation or by percutaneous transvenous coil embolization. There is no strong evidence to recommend one surgical technique over another. Medical treatment strategies include administration of non-absorbable disaccharides (i.e., lactulose), antibiotics, and dietary changes, and are indicated for pre-surgical stabilization or when surgical intervention is not feasible. After CPSS attenuation, short- and long-term post-surgical complications may be seen, such as post-operative seizures and recurrence of clinical signs, respectively. Prognosis after surgical attenuation of CPSS is generally favorable for dogs and fair for cats.

Prediction of outcome after ligation or thin film banding of extrahepatic shunts, based on plasma albumin concentration and hematologic expression of 8 target genes in 85 dogs

BACKGROUND

In dogs with a congenital extrahepatic portosystemic shunt (EHPSS), outcome after surgical attenuation is difficult to predict.

OBJECTIVES

Develop a minimally invasive test to predict outcome after surgical EHPSS attenuation and establish risk factors for postattenuation seizures (PAS).

ANIMALS

Eighty-five client-owned dogs referred for surgical attenuation of a single EHPSS.

METHODS

mRNA expression of 8 genes was measured in preoperatively collected venous blood samples. Outcome was determined at a median of 92 days (range, 26-208) postoperatively by evaluating clinical performance, blood test results and abdominal ultrasonography. Multivariable logistic regression was used to construct models predicting clinical and complete recovery. The associations between putative predictors and PAS were studied using univariable analyses.

RESULTS

Five of 85 dogs developed PAS. Risk factors were age, white blood cell (WBC) count and expression of hepatocyte growth factor activator and LysM and putative peptidoglycan-binding domain-containing protein 2. Clinical recovery was observed in 72 of 85 dogs and complete recovery in 51 of 80 dogs (median follow-up, 92 days). The model predicting clinical recovery included albumin, WBC count, and methionine adenosyltransferase 2 alpha (MAT2α) expression, whereas the model predicting complete recovery included albumin, and connective tissue growth factor precursor and MAT2α expression. The areas under the receiver operating characteristic curves were 0.886 (95% confidence interval [CI]: 0.783, 0.990) and 0.794 (95% CI: 0.686, 0.902), respectively.

CONCLUSIONS AND CLINICAL IMPORTANCE

Two models were constructed for predicting outcome after EHPSS attenuation using venous blood samples. The model predicting clinical recovery showed the best diagnostic properties. Clinical application requires further validation.

Radiologic Evaluation of Portosystemic Shunts in Humans and Small Animals: Review of the Literature with Clinical Case Reports

The portal venous system is a network of vessels that carry blood from the capillary beds of the major abdominal organs to the liver. During embryology, the portal venous system can develop aberrantly, leading to vascular connections between the portal and systemic venous circulation known as portosystemic shunts. The purpose of this comparative review with a few short representative case reports was to present the similarities and differences in portosystemic shunts in humans and small animals and their radiologic evaluation. Aberrant vascular connections between the portal and systemic venous circulation enable portal blood to bypass metabolism and detoxification in the liver, leading to significant clinical implications. Portosystemic shunts are very rare in humans, but these connections are much more common in small animals, affecting up to 0.6% of small animals. Portosystemic shunts can be congenital or acquired and are divided into intrahepatic and extrahepatic types. Because of its ability to accurately assess abdominal structures, large vessels, and their flow dynamics without anesthesia, ultrasonography has become the first imaging modality employed for the diagnostic evaluation of portosystemic shunts in both humans and small animals. This is usually followed by contrast-enhanced computed tomographic angiography in order to better define the exact shunt anatomy and to plan treatment. It is important to understand the embryology, anatomy, pathology, and pathophysiology of portosystemic shunts in order to understand the findings of radiologic imaging and to initiate appropriate treatment.

Evaluation of different blood tests in dogs with extrahepatic portosystemic shunts to assess shunt closure after surgical treatment

OBJECTIVE

To determine the sensitivity and specificity of different individual and combined blood tests to assess extrahepatic portosystemic shunt (EHPSS) closure after gradual attenuation of EHPSS in dogs.

STUDY DESIGN

Clinical prospective study.

ANIMALS

Twenty client-owned dogs with EHPSS.

METHODS

Fasting ammonia (FA), preprandial, postprandial, and paired serum bile acids (SBA), the lidocaine/monoethylglycylxylidide (L/MEGX) test, and serum hyaluronic acid (SHA) were performed at diagnosis, and 1, 3, and 6 months postoperatively. Transsplenic portal scintigraphy was performed to determine EHPSS closure 3 months postoperatively. Their sensitivity and specificity in determining shunt closure postoperatively were calculated.

RESULTS

When assessing a single blood parameter, FA had the highest specificity (100%), whereas SHA and MEGX measured 15 min after lidocaine administration (T15) had the highest sensitivity (96.9% and 96.2%, respectively) for determining shunt closure postoperatively. The most promising blood test combinations were SHA (sensitivity 96.9%, specificity 81.8%), combined with the L/MEGX test (MEGX at T15: sensitivity 100%, specificity 72.4%) or the L/MEGX test (MEGX at T15) combined with either FA (sensitivity 100%, specificity 82.8%) or postprandial SBA (sensitivity 100%, specificity 81.5%).

CONCLUSION

Both SHA and the L/MEGX test were sensitive tests for determining shunt closure after gradual attenuation of EHPSS. Test performances could even be improved by combining these tests with each other or with traditional tests such as FA or postprandial SBA.

CLINICAL SIGNIFICANCE

Although SHA and the L/MEGX test are sensitive blood tests for determining EHPSS closure, especially when combined with traditional blood tests, imaging is still needed to confirm EHPSS closure.

Laparoscopic portosystemic shunt attenuation in 20 dogs (2018-2021)

OBJECTIVE

To describe the technique, complications, and outcome of laparoscopic portosystemic shunt attenuation (LPSSA) in dogs.

STUDY DESIGN

Retrospective study.

ANIMALS

Twenty client-owned dogs.

METHODS

Medical records were searched for dogs with a single congenital extrahepatic portosystemic shunt (CEPSS) that was treated with LPSSA. Signalment, clinical signs, CEPSS location, diagnostic imaging, laparoscopic approach, operative technique, complications, and clinical outcome were reviewed.

RESULTS

Fourteen dogs with CEPSS located in the epiploic foramen had a right (13/14) or left (1/14) paramedian approach. In 6 dogs a CEPSS was not located in the epiploic foramen, and a left paramedian approach was used. A 3 or 4-port technique was used in 7 and 13 dogs, respectively. A thin film band was used for CEPSS attenuation in all dogs. The median operating time for LPSSA was 62 min (range 27-98 min). Intraoperative complications requiring conversion to an open technique occurred in 5 dogs. Mild perioperative self-limiting portal hypertension occurred in 3 dogs, while severe portal hypertension with surgical revision occurred in 1 case. The complications were resolved, and all dogs had a good outcome.

CONCLUSION

Laparoscopic portosystemic shunt attenuation can be performed in dogs, in particular for a CEPSS located in the epiploic foramen using a right paramedian approach. For CEPSS not located in the epiploic foramen, a left paramedian approach is recommended. Conversion to open celiotomy was required in around a third of cases.

CLINICAL SIGNIFICANCE

Laparoscopic attenuation of CEPSSs can be performed in dogs and has a good clinical outcome, particularly for CEPSS located in the epiploic foramen.

Feasibility of thoracoscopic attenuation of the azygos vein as a model for portoazygos shunts: A canine cadaveric study

OBJECTIVE

To evaluate the feasibility of thoracoscopic placement of three vascular attenuation devices by using the azygos vein as a model for portoazygos (PA) shunts and to describe the approach for thoracoscopic placement of these attenuation devices in small breed dogs.

STUDY DESIGN

Randomized, prospective, cadaveric study.

ANIMALS

Cadavers of 10 adult small breed dogs.

METHODS

Cadavers were placed in sternal recumbency with left dorsolateral obliquity, and three thoracoscopic ports were established in the right hemithorax at the mid-10th intercostal space and dorsal third of the ninth and 11th intercostal spaces. The caudal azygos vein was thoracoscopically isolated along three adjacent segments bordered by four intercostal arteries, beginning just cranial to the first intercostal artery visualized cranial to the diaphragm. Three attenuation devices including coated cellophane, uncoated cellophane, and a 5-mm ameroid constrictor were thoracoscopically placed around one segment in each dog. Minor port access modifications were required to improve working space and triangulation in three dogs. Ability to successfully place the device, time required for placement, endoscopic clip configuration, and complications associated with placement were recorded.

RESULTS

Median dog weight was 7.7 kg (range, 1.8-11). All attenuation devices were successfully placed thoracoscopically in all cadavers. No difference was detected in time required for placement between the ameroid constrictor and coated and uncoated cellophane (range, 2.3-33.8 minutes, P = .8).

CONCLUSION

Ameroid constrictors and thin film bands were consistently placed via thoracoscopy around the caudal azygos vein of small breed dogs.

CLINICAL SIGNIFICANCE

These results justify further investigation of thoracoscopic PA shunt attenuation in affected dogs.

Diagnostic value of blood variables following attenuation of congenital extrahepatic portosystemic shunt in dogs

BACKGROUND

The aims of this study were to determine if extrahepatic portosystemic shunt (EHPSS) postoperative closure could be predicted based on preoperative blood analyses and to determine the accuracy of blood variables to evaluate persistence of portosystemic shunting postoperatively (multiple acquired portosystemic shunts (MAPSS) or persistent EHPSS).

METHODS

Retrospectively, 62 dogs treated surgically for congenital EHPSS that underwent postoperative trans-splenic portal scintigraphy or CT angiography three to six months postoperatively were included.

RESULTS

None of the studied preoperative blood variables could unambiguously predict surgical outcome. Elevated postoperative fasting venous ammonia (FA) concentration always indicated surgical failure (persistent shunting or MAPSS), but normal FA did not provide any information on the postoperative shunting status. Paired serum bile acids (SBA) were not reliable enough to confirm or exclude postoperative shunting. In the presence of low normal postoperative FA levels, elevated preprandial SBA was more likely in dogs with persistent shunting (sensitivity of 0.79, specificity of 0.83), whereas postprandial SBA below reference limit was more often observed in case of surgical success (sensitivity of 0.93, specificity of 0.67).

CONCLUSION

Blood variables, and more specifically the combination of FA and SBA, are not a valuable alternative to advanced medical imaging to reliably assess the surgical outcome after EHPSS surgery.

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

Background

Several 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.

Objectives

To 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.

Animals

Not used.

Methods

A 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.

Results

Forty‐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 Importance

The 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.

The chemical and ultra-structural analysis of thin plastic films used for surgical attenuation of portosystemic shunts in dogs and cats

The objective of the study was to (1) characterize and compare the chemical composition at the surface, subsurface and in the bulk of thin plastic films used for portosystemic shunt attenuation in their native state and after plasma exposure. (2) Assess the presence, concentration and location of irritant compounds (e.g dicetyl phosphate) within the films. Attenuated Total Reflectance Infrared Spectroscopy (ATR-IR), X-ray Photoelectron Spectroscopy (XPS) and dynamic Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) were used to analyze thirteen thin plastic films. Sample thickness was visualized and measured using Scanning Electron Microscopy (SEM). Sample thicknesses were compared using a one-way ANOVA. XPS reported low phosphorous concentrations (surrogate marker of dicetyl phosphate) between 0.01 and 0.19% wt at the sample surfaces (top 10 nm). There were significant differences between film thicknesses (P < .001) observed by SEM. The ATR-IR and ToF-SIMS identified four distinct surface and bulk chemical profiles: 1) Cellophane, 2) Polypropylene, 3) Modified Cellophane, and 4) Unique. Following plasma immersion for 6 weeks, samples showed little change in film thickness or chemical composition. This study confirmed that films used to attenuate portosystemic shunts were commonly not pure cellophane, with significant variations in surface and bulk chemistry. Suspected irritant compounds were not readily identifiable in significant proportions. Pronounced variability existed in both the thickness and chemical composition of these films (surface vs. bulk). The present findings lead to a legitimate question about the reproducibility of shunt occlusion when using thin plastic films from different origins.

Survey of surgical specialists' content preferences in radiology reports for extrahepatic portosystemic shunts

The aim of this prospective, survey study was to assess the opinions of specialist surgeons as to the preferred content, nomenclature, and classification of extrahepatic portosystemic shunts for inclusion in radiology reports. A link to an online survey was sent by email to members of the European College of Veterinary Surgeons and the Association of Veterinary Soft Tissue Surgeons, and was made available on the American College of Veterinary Surgeons web forum and Facebook page. There were 93 respondents (survey sent to over 2500 email addresses and made available in two online locations). Most respondents agreed that they both review the images themselves (87/92, 95%) and read the radiology report (82/92, 89%) prior to surgery. Most respondents believed that the radiology report should contain a detailed anatomic description of the insertion (83/92, 90%), origin (54/91, 59%), and course (70/92, 76%) of the shunt, as well as a measure of the diameter of the shunting vessel at its insertion (54/92, 59%). Most respondents (70/90, 78%) disagreed that a brief description of shunt type, such as portocaval or portophrenic, was sufficient. Respondents were undecided regarding the use of an alphanumeric classification system (36/92, 39% agree; 32/92, 35% disagree). There was agreement that details of the presence or absence of urolithiasis (91/93, 98%), renomegaly (54/93, 58%), and peritoneal fluid (72/92, 78%) should be included in the report. The results of this study will help to guide reporting radiologists in providing descriptions of extrahepatic portosystemic shunts that include information most preferred by the recipient surgeons.

Recanalisation of a congenital extrahepatic portosystemic shunt previously attenuated with cellophane banding in a cat

Case summary

A congenital extrahepatic portosystemic shunt was attenuated with commercial roll cellophane banding in a cat and postoperative liver changes were monitored using CT angiography (CTA). The patient clinically improved after cellophane banding, characterised by resolution of hepatic encephalopathy, weight gain, reference interval (RI) bile acid stimulation tests, as well as CTA-documented increased liver size, increased hepatic vasculature and shunt attenuation. Six months later the cat re-presented with recurrence of clinical signs and increased bile acids. CTA confirmed recanalisation of the shunt. Shunt attenuation was repeated using pure cellophane banding and nearly complete closure of the shunt was later documented by CTA. Seven months later, recanalisation was again documented via CTA and associated with clinical signs and increased bile acids. Complete ligation of the shunt was achieved using a polypropylene ligature and a titanium ligating clip. At long-term follow-up, the cat was clinically well, and bile acids and biochemistry were within the RIs.

Relevance and novel information

This is the first report of CTA-documented recanalisation of an extrahepatic portosystemic shunt previously attenuated with cellophane banding. Recanalisation should be considered as a differential for recurrence of hepatic encephalopathy following cellophane banding.

Interventional Radiology Management of Vascular Malformations: Portosystemic Shunts and Vascular Fistulae/Malformations

Vascular malformations are abnormal connections between blood vessels that can have various endothelial characteristics. Although uncommon, these malformations can present challenging diagnostic and therapeutic scenarios. The use of interventional radiology techniques in the management of various vascular malformations is an attractive option because of the ability to treat these malformations at the most appropriate anatomic location and in the most effective manner. Techniques such as coil embolization of intrahepatic portosystemic shunts and liquid embolization of arteriovenous fistulae/malformations have shown tremendous potential as treatments for these challenging diseases.

A Chronic Cardiac Ischemia Model in Swine Using an Ameroid Constrictor

Cardiovascular disease remains the number one cause of mortality in the United States. There are numerous approaches to treating these diseases, but regardless of the approach, an in vivo model is needed to test each treatment. The pig is one of the most used large animal models for cardiovascular disease. Its heart is very similar in anatomy and function to that of a human. The ameroid placement technique creates an ischemic area of the heart, which has many useful applications in studying myocardial infarction. This model has been used for surgical research, pharmaceutical studies, imaging techniques, and cell therapies.

There are several ways of inducing an ischemic area in the heart. Each has its advantages and disadvantages, but the placement of an ameroid constrictor remains the most widely used technique. The main advantages to using the ameroid are its prevalence in existing research, its availability in various sizes to accommodate the anatomy and size of the vessel to be constricted, the surgery is a relatively simple procedure, and the post-operative monitoring is minimal, since there are no external devices to maintain. This paper provides a detailed overview of the proper technique for the placement of the ameroid constrictor.

Effects of repeated gas sterilization on closure rates of ameroid ring constrictors in vitro

OBJECTIVE

To determine the effect of repeated gas sterilization on rate of closure of ameroid ring constrictors in vitro.

SAMPLE

Twenty-four 3.5-mm ameroid ring constrictors.

PROCEDURES

Ameroid ring constrictors were allocated to 1 of 4 treatment groups (6/group) to undergo gas sterilization 0, 1, 5, or 10 times. After sterilization, constrictors were incubated in canine plasma at a protein concentration of 3 g/dL for 27 days. A digital camera was used to obtain images of the constrictors prior to and at various points during incubation, and lumen diameter was measured.

RESULTS

Mean ± SD percentage of lumen closure for all groups of ameroid ring constrictors combined was 85.2 ± 1.6% at day 0 (prior to plasma incubation) and 95.4 ± 0.8% at day 27. Mean lumen area was 3.64 ± 0.43 mm(2) (95% confidence interval, 2.67 to 4.77 mm(2)) at day 0 and 1.32 ± 0.25 mm(2) (95% confidence interval, 0.76 to 2.04 mm(2)) at day 27. None of the ameroid ring constrictors had closed completely by day 27.

CONCLUSIONS AND CLINICAL RELEVANCE

Overall closure rates for ameroid ring constrictors appeared to be unaffected by repeated gas sterilization up to 10 times. Findings suggested that veterinary surgeons can resterilize ameroid ring constrictors up to 10 times with confidence that ring properties would remain suitable for clinical use.

A multimodality imaging approach for guiding a modified endovascular coil embolization of a single intrahepatic portosystemic shunt in dogs

Intrahepatic portosystemic shunts (IHPSS) in dogs are aberrant vascular anomalies that connect the portal and the systemic venous vessels. In most of the patients, the surgical approach is unfavourable due to the difficulties in isolating the IHPSS, making the option of a percutaneous transvenous coil embolization (PTCE) one of the safer occlusive procedures. This study describes the treatment of eight dogs with a single IHPSS using a multimodality imaging approach to guide the modified PTCE procedure. This new technique results in a decrease of 71% of the time of the entire procedure with the reduction of 91% in the time required involved the IHPSS identification and in the fluoroscopy exposure time avoiding the need for iodinated contrast agents during the procedure. Moreover, the placement of the catheter before the caval stent ensures its greater stability, enhancing the procedural safety in the phase when the coils are released and avoiding the risk of their dislocation.

Long-term survival and quality of life in dogs with clinical signs associated with a congenital portosystemic shunt after surgical or medical treatment

OBJECTIVE

To compare long-term survival and quality of life data in dogs with clinical signs associated with a congenital portosystemic shunt (CPSS) that underwent medical or surgical treatment.

DESIGN

Prospective cohort study.

ANIMALS

124 client-owned dogs with CPSS.

PROCEDURES

Dogs received medical or surgical treatment without regard to signalment, clinical signs, or clinicopathologic results. Survival data were analyzed with a Cox regression model. Quality of life information, obtained from owner questionnaires, included frequency of CPSS-associated clinical signs (from which a clinical score was derived), whether owners considered their dog normal, and (for surgically treated dogs) any ongoing medical treatment for CPSS. A Mann-Whitney U test was used to compare mean clinical score data between surgically and medically managed dogs during predetermined follow-up intervals.

RESULTS

97 dogs underwent surgical treatment; 27 were managed medically. Median follow-up time for all dogs was 1,936 days. Forty-five dogs (24 medically managed and 21 surgically managed) died or were euthanized during the follow-up period. Survival rate was significantly improved in dogs that underwent surgical treatment (hazard ratio, 8.11; 95% CI, 4.20 to 15.66) than in those treated medically for CPSS. Neither age at diagnosis nor shunt type affected survival rate. Frequency of clinical signs was lower in surgically versus medically managed dogs for all follow-up intervals, with a significant difference between groups at 4 to 7 years after study entry.

CONCLUSIONS AND CLINICAL RELEVANCE

Surgical treatment of CPSS in dogs resulted in significantly improved survival rate and lower frequency of ongoing clinical signs, compared with medical management. Age at diagnosis did not affect survival rate and should not influence treatment choice.

In vitro effect of multiple hydrogen peroxide gas plasma sterilizations on the rate of closure of ameroid constrictors

OBJECTIVE

To evaluate the effect of multiple hydrogen peroxide gas plasma (HPGP) sterilizations on the rate of closure of ameroid constrictors.

SAMPLE

Thirty-six 5.0-mm ameroid constrictors.

PROCEDURES

Ameroid constrictors were randomly allocated to 6 groups. Each group underwent 1, 2, 3, 4, 5, or 6 HPGP sterilizations. Ameroid constrictors were then incubated for 35 days in canine plasma and digitally imaged at predetermined times during incubation. One individual, who was unaware of the group to which each ameroid constrictor was assigned, measured the lumen area of the constrictor on each digital image. Mean lumen area was compared among groups.

RESULTS

No ameroid constrictors were completely closed after 35 days of incubation in canine plasma. Mean lumen area after incubation did not differ among constrictors that underwent 1, 2, and 3 sterilizations. Constrictors that underwent 4 sterilizations were closed significantly more than were those that underwent 1, 2, or 3 sterilizations. Mean lumen area after incubation did not differ significantly between constrictors that underwent 5 and 6 sterilizations, although the final lumen areas for those constrictors were significantly smaller than those for constrictors that underwent 1, 2, 3, and 4 sterilizations.

CONCLUSIONS AND CLINICAL RELEVANCE

Ameroid constrictors that underwent 5 and 6 HPGP sterilizations had a 9% to 12% decrease in lumen area, compared with that of constrictors that underwent ≤ 4 plasma sterilizations, and the use of such constrictors could increase the risk of portal hypertension and secondary acquired shunting or decrease the risk of persistent shunting.

Endovascular evaluation and treatment of intrahepatic portosystemic shunts in dogs: 100 cases (2001-2011)

OBJECTIVE

To evaluate short- and long-term outcome following endovascular treatment of intrahepatic portosystemic shunts in dogs.

DESIGN

Retrospective case series.

ANIMALS

100 dogs.

PROCEDURES

All patients had angiographic evaluation with or without endovascular shunt attenuation. The medical records were reviewed for pertinent data, complications, outcome, and survival time.

RESULTS

95 dogs with congenital intrahepatic portosystemic shunts received 111 procedures (83% [79/95] had 1 treatment, and 17% [16/95] had > 1 treatment; 5 dogs had no treatment because of excessive portal venous pressure-central venous pressure gradients). Angiography identified 38 right, 33 left, and 19 central divisional single shunts (n = 90) and 10 complex or multiple shunts. Partial shunt attenuation was performed in 92 dogs by means of caval stent placement and insertion of thrombogenic coils within the shunt, and 3 had complete acute shunt occlusion. Major intraoperative complications (3/111 [3%]) included temporary severe portal hypertension in 2 dogs and gastrointestinal hemorrhage in 1 dog. Major postoperative (< 1 week after surgery) complications (14/111 [13%]) included seizures or hepatoencephalopathy (7/111 [6%]), cardiac arrest (2/111 [2%]), jugular site bleeding (2/111 [2%]), pneumonia (1/111 [1%]), suspected portal hypertension (1/111 [1%]), and acute death (1/111 [1%]). Median follow-up time was 958 days (range, 0 to 3,411 days). Median survival time for treated dogs was 2,204 days (range, 0 to 3,411 days). Outcome was considered excellent (57/86 [66%]) or fair (13/86 [15%]) in 70 of 86 (81%) treated dogs.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that endovascular treatment of intrahepatic shunts in dogs may result in lower morbidity and mortality rates, with similar success rates, compared with previously reported outcomes for open surgical procedures. Gastrointestinal ulceration was a common finding among this population of dogs, and lifelong gastroprotectant medications are now recommended.

Multiple Congenital PSS in a Dog: Case Report and Literature Review

A 4 yr old spayed female mixed-breed dog presented with a 2 yr history of recurring increases in liver enzymes. Two congenital portosystemic shunts (PSSs) were identified using computed tomography (CT) angiography, which included a portoazygous and portorenal extrahepatic shunt. Double right renal veins were also identified. The shunts were successfully identified and attenuated with cellophane banding. Multiple congenital PSS is a rare phenomenon, but should be considered during exploratory laparotomy for PSS and in dogs with poor response to surgical attenuation of a single PSS. CT proved to be a crucial part of accurate diagnosis and surgical planning for this dog with multiple congenital PSS.

Use of a Dacron shape-memory intravascular coil to achieve slow, progressive occlusion of the jugular vein in dogs

OBJECTIVE

To investigate the ability of shape memory Dacron polymer vascular coils to induce the complete, gradual occlusion of the canine jugular vein.

STUDY DESIGN

Observational pilot study.

ANIMALS

Nine purpose-bred dogs.

METHODS

Eighteen coils were deployed in nine dogs using fluoroscopic-guided percutaneous transvenous coil implantation. Individual coil formulations varied around a Dacron polymer base. Jugular vein diameter, percent vessel occlusion, and thrombus echogenicity were monitored at weekly intervals using ultrasonography. Affected jugular veins were harvested at 6 weeks post-implantation and histopathological analysis was performed to assess adventitial fibrosis, intimal layer thickening, and inflammation.

RESULTS

Ten coils migrated from the jugular veins to the pulmonary vasculature within 0-2 weeks following implantation. Three jugular veins achieved at least 90% occlusion at six weeks. Histopathology of these jugular veins revealed marked perivascular thickening and fibrovascular proliferation, increased infiltration of macrophages, neutrophils and lymphocytes, and abundant fibroplasia.

CONCLUSIONS

Complete, gradual occlusion of a jugular vein was achieved in three dogs. Significant vessel wall reaction and inflammation can induce gradual vessel occlusion when a Dacron coil remains implanted within the jugular vein. Dacron polymer coils could be a feasible treatment option for the gradual occlusion of congenital portosystemic shunts in dogs using minimally invasive, percutaneous transvenous implantation.

Association between hepatic histopathologic lesions and clinical findings in dogs undergoing surgical attenuation of a congenital portosystemic shunt: 38 cases (2000-2004)

OBJECTIVE

To review hepatic histopathologic lesions in dogs undergoing surgical attenuation of a congenital portosystemic shunt (CPSS) in relation to clinical findings and tolerance of complete surgical attenuation.

DESIGN

Retrospective case series.

ANIMALS

38 dogs that underwent surgical attenuation of a CPSS.

PROCEDURES

Hepatic histologic examination findings and medical records of dogs undergoing surgical attenuation of a single CPSS between August 2000 and July 2004 were reviewed. Liver biopsy specimens were obtained from 38 dogs during surgery prior to complete (n = 16) or partial (22) attenuation of a CPSS and from 13 of the same dogs a median of 3 months following surgical attenuation.

RESULTS

Portal tracts were inadequate for interpretation in 2 liver biopsy specimens. Liver biopsy specimens obtained prior to surgical attenuation of a CPSS had a lack of identifiable portal veins (13/36 dogs), hepatic arteriolar proliferation (25/36), ductular reaction (5/36), steatosis (16/38), and iron accumulation (32/38). Lack of identifiable portal veins on histologic examination was associated with increased hepatic arteriolar proliferation, decreased tolerance to complete surgical CPSS attenuation, and decreased opacification of intrahepatic portal vessels on portovenography. Ductular reaction was always associated with failure to tolerate complete surgical attenuation of a CPSS. Surgical CPSS attenuation resulted in significant clinical, serum biochemical, and portovenographic changes indicative of improved liver function, but only subtle changes in hepatic histologic examination findings.

CONCLUSIONS AND CLINICAL RELEVANCE

Dogs without identifiable intrahepatic portal veins that had a ductular reaction on hepatic histologic examination were less likely to tolerate complete attenuation of a CPSS.

Vascular endothelial growth factor (VEGF) and VEGF receptor expression in biopsy samples of liver from dogs with congenital portosystemic shunts

Surgical attenuation of a congenital portosystemic shunt (CPSS) results in increased liver mass, development of intrahepatic portal vasculature and improved liver function. Vascular endothelial growth factor (VEGF) is a key regulator of angiogenesis. The aim of this study was to investigate the role of VEGF and its receptor in the hepatic response to CPSS surgery. The study included 99 dogs with CPSS treated with either partial or complete suture attenuation. Forty-four dogs with partial attenuation underwent a second surgery for complete attenuation. The expression of VEGF and VEGF receptor 2 (VEGFR2) in biopsy samples of liver was assessed by immunohistochemistry with rabbit anti-human VEGF polyclonal antibody and mouse anti-human VEGFR2 monoclonal antibody. Expression of these molecules was graded. The proportion of samples expressing VEGF was significantly greater in samples from dogs with CPSS compared with control samples (P=0.04) and the proportion of samples expressing VEGFR2 was significantly greater in control samples compared with samples from dogs with CPSS (P=0.04). VEGF labelling grade decreased significantly (P=0.038) and VEGFR2 increased significantly (P=0.046) between first and second surgery. The decrease in VEGF may reflect transient expression, preferential expression of other factors, reperfusion of existing vessels and/or increased angiogenesis before surgery in the form of arterialization and subsequent reduction due to improved portal blood flow. Partial suture attenuation was associated with a degree of 'normalization' of VEGF and VEGFR2 expression when compared with the control samples. Further investigation is needed to provide more information on the hepatic response to CPSS surgery.

Comparison of survival after surgical or medical treatment in dogs with a congenital portosystemic shunt

OBJECTIVE

To compare survival of dogs with a congenital portosystemic shunt (CPSS) that received medical or surgical treatment.

DESIGN

Prospective cohort study.

ANIMALS

126 client-owned dogs with a single CPSS.

PROCEDURES

Dogs were examined at 1 of 3 referral clinics, and a single CPSS was diagnosed in each. Dogs received medical or surgical treatment without regard to signalment, clinical signs, or results of hematologic or biochemical analysis. Survival data were analyzed via a Cox regression model.

RESULTS

During a median follow-up period of 579 days, 18 of 126 dogs died as a result of CPSS. Dogs treated via surgical intervention survived significantly longer than did those treated medically. Hazard ratio for medical versus surgical treatment of CPSS (for the treatment-only model) was 2.9 (95% confidence interval, 1.1 to 7.2). Age at CPSS diagnosis did not affect survival.

CONCLUSIONS AND CLINICAL RELEVANCE

Both medical and surgical treatment can be used to achieve long-term survival of dogs with CPSS, although results of statistical analysis supported the widely held belief that surgery is preferable to medical treatment. However, the study population consisted of dogs at referral clinics, which suggested that efficacy of medical treatment may have been underestimated. Although surgical intervention was associated with a better chance of long-term survival, medical management provided an acceptable first-line option. Age at examination did not affect survival, which implied that early surgical intervention was not essential. Dogs with CPSS that do not achieve acceptable resolution with medical treatment can subsequently be treated surgically.

In vitro expansion patterns of ameroid ring constrictors

OBJECTIVE

To evaluate and quantify in vitro dimensional changes of ameroid ring constrictors (ARCs) with and without the outer stainless steel ring in place over time.

SAMPLE POPULATION

12 ARCs (5.0-mm diameter).

PROCEDURES

6 ARCs were immersed in canine plasma baths for 34 days without the stainless steel outer ring in place (group N), and 6 ARCs were immersed in canine plasma baths with the stainless steel outer ring in place (group R). The ARCs were digitally imaged at day 0, daily for the first 10 days, then on days 14, 20, 27, and 34. Inner diameter, outer diameter, luminal area, and height were measured for each time point. Volume and weight of rings were obtained at the start and completion of the study.

RESULTS

The inner diameter, outer diameter, and luminal area were significantly different between the 2 groups over the course of 34 days. The inner diameter and luminal area of the R-group constructs did not change significantly, while the inner diameter, outer diameter, luminal area, and height of N-group constructs all significantly increased over the course of the study.

CONCLUSIONS AND CLINICAL RELEVANCE

R-group constructs had insignificant centripetal swelling without ring closure, whereas N-group constructs had significant generalized centrifugal expansion. Results of this study indicated that the outer stainless steel ring of an ARC may not be necessary for attenuation and closure of some single extrahepatic portosystemic shunts.

The sonographic search for portosystemic shunts

The diagnostic investigation of portosystemic shunts (PSS) has evolved over the last few decades, helping to understand and identify these vascular anomalies that affect many dogs and cats. Ultrasonography has become an important tool in small animals and high-resolution systems are now widely available. Several sonographic features are observed with the different types of congenital and acquired PSS. A systematic, stepwise approach is described to facilitate ultrasound diagnosis of PSS in small animals.

Ligation of Ameroid-Stenosed Coronary Artery Leads to Reproducible Myocardial Infarction—A Pilot Study in a Porcine Model

OBJECTIVE

Myocardial gene and cellular therapies have revived the use of porcine ischemic heart models. Commonly applied ameroid-obstruction produces inconsistent coronary stenoses and myocardial lesions, whereas abrupt coronary occlusion causes arrhythmias and sudden death. To produce a constant myocardial lesion after adaptation to ischemia, we surgically modified the ameroid-model by ligation. As a pilot study for further cell therapy research, the spontaneous myocardial response is described.

MATERIALS AND METHODS

Simultaneously with ameroid application, a loose loop of nonabsorbable thread was placed around the left circumflex artery (LCx) on 11 domestic piglets. Three weeks later, the loop was tightened. Coronary arteriograms with Rentrop collateral grading from 0 to 3, and 99mTc-single photon emission computerized tomography studies were performed 1 to 5 wk after ligation. At autopsy, the hearts were analyzed macroscopically, histologically, and with von Willebrandt factor-staining.

RESULTS

LCx-banding was well-tolerated in nine animals, of which angiographic occlusion was gained in eight. Postmortem analysis revealed a 5 to 10 cm(2) transmural or subendocardial lateral myocardial infarction in all except one heart. One week after occlusion, LCx showed well-developed collateral filling (Rentrop-grade 2.7 +/- 0.4), which remained unchanged at 5 wk. On single photon emission computerized tomography-scans, lateral wall perfusion increased spontaneously between 1 and 5 wk (P = 0.02), and von Willebrandt factor revealed clusters of neovascularization at the borders of infarct areas.

CONCLUSIONS

This new modification of ameroid model standardizes myocardial lesion, which might reduce animal number in preclinical studies, thus having ethical aspect. The remarked potential for spontaneous recovery in ischemic porcine myocardium should be considered in preclinical therapeutic studies.

Outcome associated with use of a percutaneously controlled hydraulic occluder for treatment of dogs with intrahepatic portosystemic shunts

OBJECTIVE

To evaluate efficacy of a hydraulic occluder (HO) used for treatment of dogs with an intrahepatic portosystemic shunt (IHPSS).

DESIGN

Prospective study.

ANIMALS

10 dogs with an IHPSS.

PROCEDURES

Serum biochemical and postprandial bile acids (PPBA) analyses and transcolonic scintigraphy were performed before surgery. Laparotomy was performed, and an uninflated HO was placed around the portal vein branch leading to the IHPSS. After surgery, 0.9% NaCl solution was injected into subcutaneous injection ports at 2, 4, 6, and 8 weeks to achieve staged occlusion of the HO. Serum biochemical analyses, PPBA analysis, and scintigraphy were performed 2 weeks after occlusion. Serum biochemical analyses were repeated 1 year after surgery.

RESULTS

Implant revision was required in 3 dogs because of rupture of the HO (n = 2) or detachment of the actuating tubing (1). Serum biochemical values and clinical signs improved in all dogs after surgery. Six of 10 dogs had PPBA concentration within reference range 2 weeks after occlusion, and 2 additional dogs had concentrations within reference range at 1 year. Only 5 of 10 dogs had complete resolution of portosystemic shunting 2 weeks after occlusion. Two dogs were lost to follow-up, and 8 dogs remained alive with no recurrence of clinical signs at a median of 22 months after surgery.

CONCLUSIONS AND CLINICAL RELEVANCE

Use of the HO appeared to be an effective method for surgical treatment for dogs with IHPSS, although problems with implant reliability indicate a need for modifications in design and manufacturing.

Evaluation of manufacturing variability, diffusion of filling solutions, and long-term maintenance of occlusion in silicone hydraulic occluders

OBJECTIVE

To evaluate manufacturing variability, diffusion of filling solutions, and maintenance of occlusion over time in 3 sizes of silicone hydraulic occluders (HOs).

SAMPLE POPULATION

2-, 5-, and 20-mm HOs (HO2, HO5, and HO20, respectively).

PROCEDURES

Manufacturing variability was analyzed by comparing variation in internal luminal areas and filling volumes within each size group. Occluders were filled to 100% occlusion with air (n = 4), saline (0.9% NaCl) solution (4), or sodium hyaluronate (4) and submerged in simulated body fluid. Changes in luminal area and weight were recorded for 133 days to evaluate maintenance of occlusion.

RESULTS

Considerable variability in uninflated luminal area and fill volumes was observed among the 3 sizes of HOs. Loss of occlusion developed in the first 12 hours in all air-filled HOs. Fluid-filled occluders were reliable in maintenance of occlusion after 133 days (99.99% for HO20, 99.59% for HO5, and 90.40% for HO2), although diffusion of saline solution and hyaluronate from all HOs was confirmed by detection of significant decreases in weight over time. There was no significant difference in weight loss between HOs filled with saline solution and HOs filled with sodium hyaluronate.

CONCLUSIONS AND CLINICAL RELEVANCE

Saline solution or sodium hyaluronate may be used as a filling solution in the HOs tested. Maintenance of occlusion was best in the larger sizes. Saline solution or sodium hyaluronate should be used in future clinical investigations of HOs. Retrograde filling to remove air should be used when filling HOs with fluid.

Outcomes of Intrahepatic Portosystemic Shunts Occluded with Ameroid Constrictors in Nine Dogs and One Cat

OBJECTIVE

To report outcome after ameroid constrictor (AC) use for single intrahepatic portosystemic shunts (IPSS).

STUDY DESIGN

Retrospective study.

ANIMALS

Nine dogs and 1 cat.

METHODS

Medical records (1999-2003) of dogs and cats with surgically confirmed IPSS were reviewed. Recorded data was: breed, sex, weight, age at surgery, clinical signs, serum biochemical and hematologic data, shunt anatomy, AC size, hospitalization, complications, and owner perception of their animal's response to surgery. Owners were contacted twice postoperatively (between 20 and 75 months) and asked to complete a simple questionnaire.

RESULTS

With this technique, complication rate was low and postligation neurologic dysfunction was not observed. In the cat and 7 dogs, clinical signs attributed to IPPS resolved and animals were fed a non-prescription diet without medication. One dog died suddenly 18 months after surgery from causes unrelated to hepatic disease. One dog was euthanatized 23 months after surgery because of repeated, increasingly refractory episodes of hepatic encephalopathy.

CONCLUSION

AC provides a safe and effective method for occlusion of some IPPS.

CLINICAL RELEVANCE

AC should be considered for occlusion of some IPPS in dogs and cats.