Determination of inheritance of single congenital portosystemic shunts in Yorkshire terriers

Diagnosis and classification of portosystemic shunts: a machine learning retrospective case-control study

Diagnosis of portosystemic shunts (PSS) in dogs often requires multiple diagnostic tests, and available clinicopathologic tests have limitations in sensitivity and specificity. The objective of this study was to train and validate a machine learning model (MLM) that can accurately predict the presence of a PSS utilizing routinely collected demographic data and clinicopathologic features. Dogs diagnosed with PSS or control dogs tested for PSS but had the condition ruled out (non-PSS) were identified. Dogs were included if a complete blood count and serum chemistry panel were available from PSS diagnostic testing. Dogs with a PSS were subcategorized as having a single intrahepatic PSS, a single extrahepatic PSS, or multiple extrahepatic PSS. An extreme gradient boosting (XGboost) MLM was trained with data from 70% of the cases, and MLM performance was determined on the test set, comprising the remaining 30% of the case data. Two MLMs were created. The first was designed to predict the presence of any PSS (PSS MLM), and the second to predict the PSS subcategory (PSS SubCat MLM). The trained PSS MLM had a sensitivity of 94.3% (95% CI 90.1-96.8%) and specificity of 90.5% (95% CI 85.32-94.0%) for dogs in the test set. The area under the receiver operator characteristic curve (AUC) was 0.976 (95% CI; 0.964-0.989). The mean corpuscular hemoglobin, lymphocyte count, and serum globulin concentration were most important in prediction classification. The PSS SubCat MLM had an accuracy of 85.7% in determining the subtype of PSS of dogs in the test set, with variable sensitivity and specificity depending on PSS subtype. These MLMs have a high accuracy for diagnosing PSS; however, the prediction of PSS subclassification is less accurate. The MLMs can be used as a screening tool to increase or decrease the index of suspicion for PSS before confirmatory diagnostics such as advanced imaging are pursued.

Anomalies of the Portal Venous System in Dogs and Cats as Seen on Multidetector-Row Computed Tomography: An Overview and Systematization Proposal

This article offers an overview of congenital and acquired vascular anomalies involving the portal venous system in dogs and cats, as determined by multidetector-row computed tomography angiography. Congenital absence of the portal vein, portal vein hypoplasia, portal vein thrombosis and portal collaterals are described. Portal collaterals are further discussed as high- and low-flow connections and categorized in hepatic arterioportal malformation, arteriovenous fistula, end-to-side and side-to-side congenital portosystemic shunts, acquired portosystemic shunts, cavoportal and porto-portal collaterals. Knowledge of different portal system anomalies helps understand the underlying physiopathological mechanism and is essential for surgical and interventional approaches.

The inheritance of extra-hepatic portosystemic shunts and elevated bile acid concentrations in Maltese dogs

OBJECTIVES

To determine the heritability of extra-hepatic portosystemic shunts and elevated post-prandial serum bile acid concentrations in Maltese dogs.

MATERIALS AND METHODS

Maltese dogs were recruited and investigated by a variable combination of procedures including dynamic bile acid testing, rectal ammonia tolerance testing, ultrasonography, portal venography, surgical inspection or necropsy. In addition, nine test matings were carried out between affected and affected dogs, and affected and unaffected dogs.

RESULTS

In 135 variably related Maltese, shunt status could be confirmed in 113, including 19 with an extra-hepatic portosystemic shunt (17 confirmed at surgery, 2 at necropsy). Rectal ammonia tolerance testing results and post-prandial serum bile acid concentrations were retrievable for 50 and 88 dogs, respectively. Pedigree information was available for these 135 and an additional 164 related dogs. Two consecutive test matings were carried out between two affected animals (whose shunts had been attenuated), with 2 of 8 (25%) of offspring having an extra-hepatic portosystemic shunt. Six test matings were carried out between an affected and an unaffected animal, with 2 of 22 (9%) offspring affected. Heritability of extra-hepatic portosystemic shunt was 0·61 calculated using variance components analysis [95% confidence interval (CI) 0·14 to 1·0, P=0·001]. The best fitting model from segregation analysis was a common, partially penetrant, recessive model (allele frequency 0·34, penetrance 0·99, CI 0·09 to 1·0). The heritability of elevated post-prandial serum bile acid (and thus likely portal vein hypoplasia) was 0·81 (CI 0·43 to 1·0, P=0·2) after logarithmic transformation of post-prandial serum bile acid concentrations.

CLINICAL SIGNIFICANCE

There is strong support for extra-hepatic portosystemic shunts and elevated post-prandial serum bile acid concentrations both being inherited conditions in Maltese.

Aberrant gene expression in dogs with portosystemic shunts

Congenital portosystemic shunts are developmental anomalies of the splanchnic vascular system that cause portal blood to bypass the liver. Large-breed dogs are predisposed for intrahepatic portosystemic shunts (IHPSS) and small-breed dogs for extrahepatic portosystemic shunts (EHPSS). While the phenotype resulting from portal bypass of the liver of the two types of shunt is identical, the genotype and molecular pathways involved are probably different. The aim of this study was to gain insight into the pathways involved in the different types of portosystemic shunting. Microarray analysis of mRNA expression in liver tissue from dogs with EHPSS and IHPSS revealed that the expression of 26 genes was altered in either IHPSS or EHPSS samples compared with that in liver samples from control dogs. Quantitative real-time PCR of these genes in 14 IHPSS, 17 EHPSS, and 8 control liver samples revealed a significant differential expression of ACBP, CCBL1, GPC3, HAMP, PALLD, VCAM1, and WEE1. Immunohistochemistry and Western blotting confirmed an increased expression of VCAM1 in IHPSS but its absence in EHPSS, an increased WEE1 expression in IHPSS but not in EHPSS, and a decreased expression of CCBL1 in both shunt types. Regarding their physiologic functions, these findings may indicate a causative role for VCAM1 in IHPSS and WEE1 for IHPSS. CCBL1 could be an interesting candidate to study not yet elucidated aspects in the pathophysiology of hepatic encephalopathy.

Distribution of extrahepatic congenital portosystemic shunt morphology in predisposed dog breeds

Background

An inherited basis for congenital extrahepatic portosystemic shunts (EHPSS) has been demonstrated in several small dog breeds. If in general both portocaval and porto-azygous shunts occur in breeds predisposed to portosystemic shunts then this could indicate a common genetic background. This study was performed to determine the distribution of extrahepatic portocaval and porto-azygous shunts in purebred dog populations.

Results

Data of 135 client owned dogs diagnosed with EHPSS at the Faculty of Veterinary Medicine of Utrecht University from 2001 – 2010 were retrospectively analyzed. The correlation between shunt localization, sex, age, dog size and breed were studied. The study group consisted of 54 males and 81 females from 24 breeds. Twenty-five percent of dogs had porto-azygous shunts and 75% had portocaval shunts. Of the dogs with porto-azygous shunts only 27% was male (P = 0.006). No significant sex difference was detected in dogs with a portocaval shunt. Both phenotypes were present in almost all breeds represented with more than six cases. Small dogs are mostly diagnosed with portocaval shunts (79%) whereas both types are detected. The age at diagnosis in dogs with porto-azygous shunts was significantly higher than that of dogs with portocaval shunts (P < 0.001).

Conclusion

The remarkable similarity of phenotypic variation in many dog breeds may indicate common underlying genes responsible for EHPSS across breeds. The subtype of EHPSS could be determined by a minor genetic component or modulating factors during embryonic development.

Inherited liver shunts in dogs elucidate pathways regulating embryonic development and clinical disorders of the portal vein

Congenital disorders of the hepatic portal vasculature are rare in man but occur frequently in certain dog breeds. In dogs, there are two main subtypes: intrahepatic portosystemic shunts, which are considered to stem from defective closure of the embryonic ductus venosus, and extrahepatic shunts, which connect the splanchnic vascular system with the vena cava or vena azygos. Both subtypes result in nearly complete bypass of the liver by the portal blood flow. In both subtypes the development of the smaller branches of the portal vein tree in the liver is impaired and terminal branches delivering portal blood to the liver lobules are often lacking. The clinical signs are due to poor liver growth, development, and function. Patency of the ductus venosus seems to be a digenic trait in Irish wolfhounds, whereas Cairn terriers with extrahepatic portosystemic shunts display a more complex inheritance. The genes involved in these disorders cannot be identified with the sporadic human cases, but in dogs, the genome-wide study of the extrahepatic form is at an advanced stage. The canine disease may lead to the identification of novel genes and pathways cooperating in growth and development of the hepatic portal vein tree. The same pathways likely regulate the development of the vascular system of regenerating livers during liver diseases such as hepatitis and cirrhosis. Therefore, the identification of these molecular pathways may provide a basis for future proregenerative intervention.

Comparison of 99mTcO4(-) trans-splenic portal scintigraphy with per-rectal portal scintigraphy for diagnosis of portosystemic shunts in dogs

OBJECTIVE

To evaluate trans-splenic portal scintigraphy (TSPS) and per-rectal portal scintigraphy (PRPS) for diagnosis of congenital portosystemic shunts (CPSS) in dogs, and compare these results with surgical findings.

STUDY DESIGN

Prospective, randomized cross over clinical trial.

ANIMALS

Dogs (n=42) with suspected CPSS.

METHODS

Dogs had TSPS and PRPS 48 hours apart; quantity of radionuclide administered was recorded. Three independent, blinded reviewers evaluated each scintigraphic study for study quality, shunt presence, number, and location of shunt termination (caudal vena cava, azygos vein). All dogs had exploratory celiotomy. Negative scintigraphic findings were confirmed with intraoperative mesenteric portography. Ameroid constrictors were placed on all extrahepatic CPSS, and hepatic biopsies were obtained.

RESULTS

TSPS was 100% sensitive and specific for diagnosis of CPSS and significantly (P<.05) more likely than PRPS to detect shunt number and termination. Interpretation was consistent between observers, and TSPS required significantly less radionuclide than PRPS.

CONCLUSION

TSPS was as sensitive as PRPS for detection of shunting vessels, and consistently yielded studies of higher quality, allowing detection of shunt number and location with consistent interpretation among radiologists.

CLINICAL RELEVANCE

TSPS provides information about shunt number and location, which allows improved surgical planning. Because it requires significantly less radionuclide, TSPS improves safety, allows for more comprehensive patient care, and earlier surgical intervention.

Association of breed with the diagnosis of congenital portosystemic shunts in dogs: 2,400 cases (1980-2002)

OBJECTIVE

To determine the annual and overall proportion of diagnoses of congenital portosystemic shunts (CPSS) in dogs and identify breeds at increased risk for CPSS.

DESIGN

Retrospective study.

ANIMALS

2,400 dogs with CPSS from veterinary teaching hospitals that reported to the Veterinary Medical Database (VMDB) from January 1, 1980 to February 28, 2002.

PROCEDURE

The proportion of diagnoses of CPSS was calculated for all dogs and each breed recorded in the VMDB annually and for the 22.2-year period. Odds ratios and adjusted confidence intervals were calculated for breeds with at least 100 accessions by comparing odds of each breed with a diagnosis of CPSS with that of mixed-breed dogs.

RESULTS

Congenital portosystemic shunts were reported in 0.18% of all dogs and 0.05% of mixed-breed dogs. The proportion of diagnoses of CPSS increased from 5 in 10,000 dogs in 1980 to 5 in 1,000 dogs in 2001. Yorkshire Terriers had the greatest total number of diagnoses of CPSS. Thirty-three breeds were significantly more likely to have a diagnosis of CPSS, compared with mixed-breed dogs. The greatest proportions of diagnoses were found in Havanese (3.2%), Yorkshire Terriers (2.9%), Maltese (1.6%), Dandie Dinmont Terriers (1.6%), and Pugs (1.3%).

CONCLUSIONS AND CLINICAL RELEVANCE

Certain breeds appear to be at increased risk for CPSS, compared with mixed-breed dogs. The increased odds ratios among specific breeds support the hypothesis of a genetic predisposition for CPSS. Clients and veterinarians should consider appropriate diagnostic tests for dogs with clinical signs and those used for breeding from breeds with increased risk of CPSS.