Markers of hepatic regeneration associated with surgical attenuation of congenital portosystemic shunts in dogs

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.

Genome-wide based model predicting recovery from portosystemic shunting after liver shunt attenuation in dogs

Background

In dogs with congenital portosystemic shunt (CPSS), recovery after surgical CPSS attenuation is difficult to predict.

Objectives

Our aim was to build a model with plasma albumin concentration and mRNA expression levels of hepatic gene products as predictors of recovery from portosystemic shunting after surgery.

Animals

Seventy‐three client‐owned dogs referred for surgical attenuation of CPSS.

Methods

A prediction model was constructed using 2 case‐control studies of recovered and nonrecovered dogs after surgical CPSS attenuation. In the 1st study, a dog‐specific gene expression microarray analysis was used to compare mRNA expression in intraoperatively collected liver tissue between 23 recovered and 23 nonrecovered dogs. In the 2nd study, preoperative plasma albumin concentration and the expression of microarray‐selected genes were confirmed by RT‐qPCR in intraoperatively collected liver samples of 31 recovered and 31 nonrecovered dogs, including 35 dogs from the 1st study.

Results

In the 1st study, 43 genes were differently expressed in recovered and nonrecovered dogs. The mean preoperative plasma albumin concentration in recovered dogs was higher compared to nonrecovered dogs (23 and 19 g/L, respectively; P = .004). The best fitting prediction model in the 2nd study included preoperative plasma albumin concentration and intraoperative DHDH, ERLEC1, and LYSMD2 gene expression levels.

Conclusion and Clinical Importance

A preclinical model was constructed using preoperative plasma albumin concentration and intraoperative hepatic mRNA expression of 3 genes that were unbiasedly selected from the genome to predict recovery from portosystemic shunting after shunt ligation. Further development is essential for clinical application.

Prospective evaluation of outcome of dogs with intrahepatic portosystemic shunts treated via percutaneous transvenous coil embolization

OBJECTIVE

To report outcome and complications after percutaneous transvenous coil embolization (PTCE) and evaluate the clinical, laboratory, and imaging changes in dogs with intrahepatic portosystemic shunts (IHPSS) pre-PTCE and post-PTCE.

STUDY DESIGN

Prospective clinical trial.

ANIMALS

Twenty-five dogs (15 dogs in imaging subgroup) with IHPSS.

METHODS

Clinical signs, hematologic, and biochemical parameters were recorded before and 3 months after PTCE. All dogs received the same medical treatment and underwent PTCE. In the imaging subgroup, ultrasonography, hepatic portal scintigraphy, and computed tomography-angiography were performed pre-PTCE and post-PTCE.

RESULTS

All evaluated bloodwork values improved by at least 50% of their initial value, by 3 months post-PTCE. Liver volume increased after PTCE (P = .001), but remained lower than normal in 11/15 dogs. Hepatic arterial fraction decreased after PTCE (P = .029), consistent with increased portal blood flow to the liver. Twenty-four of 25 dogs were available for reevaluation at 3 months, and all abnormal clinical signs had resolved in 22/24 dogs.

CONCLUSION

PTCE appears promising as a treatment for IHPSS, as clinical signs resolved in most cases, bloodwork abnormalities often normalized, and the procedure was performed safely with minimal complications. PTCE increased hepatic portal perfusion and liver volume in most dogs. These promising results justify a future randomized clinical trial comparing PTCE, other attenuation options, and medical management alone.

Lipopolysaccharide and toll-like receptor 4 in dogs with congenital portosystemic shunts

Surgical attenuation of a congenital portosystemic shunt (CPSS) results in increased portal vein perfusion, liver growth and clinical improvement. Portal lipopolysaccharide (LPS) is implicated in liver regeneration via toll-like receptor (TLR) 4 mediated cytokine activation. The aim of this study was to investigate factors associated with LPS in dogs with CPSS. Plasma LPS concentrations were measured in the peripheral and portal blood using a limulus amoebocyte lysate (LAL) assay. LPS concentration was significantly greater in the portal blood compared to peripheral blood in dogs with CPSS (P = 0.046) and control dogs (P = 0.002). LPS concentrations in the peripheral (P = 0.012) and portal (P = 0.005) blood of dogs with CPSS were significantly greater than those of control dogs. The relative mRNA expression of cytokines and TLRs was measured in liver biopsies from dogs with CPSS using quantitative PCR. TLR4 expression significantly increased following partial CPSS attenuation (P = 0.020). TLR4 expression was significantly greater in dogs that tolerated complete CPSS attenuation (P = 0.011) and those with good portal blood flow on pre-attenuation (P = 0.004) and post-attenuation (P = 0.015) portovenography. Serum interleukin (IL)-6 concentration was measured using a canine specific ELISA and significantly increased 24 h following CPSS attenuation (P < 0.001). Portal LPS was increased in dogs with CPSS, consistent with decreased hepatic clearance. TLR4 mRNA expression was significantly associated with portal blood flow and increased following surgery. These findings support the concept that portal LPS delivery is important in the hepatic response to surgical attenuation. Serum IL-6 significantly increased following surgery, consistent with LPS stimulation via TLR4, although this increase might be non-specific.

Attenuation of congenital portosystemic shunt reduces inflammation in dogs

Liver disease is a major cause of morbidity and mortality. One of the most significant complications in patients with liver disease is the development of neurological disturbances, termed hepatic encephalopathy. The pathogenesis of hepatic encephalopathy is incompletely understood, which has resulted in the development of a wide range of experimental models. Congenital portosystemic shunt is one of the most common congenital disorders diagnosed in client owned dogs. Our recent studies have demonstrated that the pathophysiology of canine hepatic encephalopathy is very similar to human hepatic encephalopathy, which provides strong support for the use of dogs with a congenital portosystemic shunt as a naturally occurring model of human hepatic encephalopathy. Specifically, we have demonstrated an important role for ammonia and inflammation in the development of hepatic encephalopathy in dogs with a congenital portosystemic shunt. Despite the apparent importance of inflammation in driving hepatic encephalopathy in dogs, it is unclear whether inflammation resolves following the successful treatment of liver disease. We hypothesized that haematological and biochemical evidence of inflammation, as gauged by neutrophil, lymphocyte and monocyte concentrations together with C-reactive protein concentrations, would decrease following successful treatment of congenital portosystemic shunts in dogs. One hundred and forty dogs with a congenital portosystemic shunt were enrolled into the study. We found that the proportion of dogs with a monocyte concentration above the reference range was significantly greater in dogs with hepatic encephalopathy at time of initial diagnosis. Importantly, neutrophil and monocyte concentrations significantly decreased following surgical congenital portosystemic shunt attenuation. We also found a significant decrease in C-reactive protein concentrations following surgical attenuation of congenital portosystemic shunts. Our study demonstrates that haematological and biochemical indices of inflammation reduce following successful treatment of the underlying liver disorder.

Rodent models and imaging techniques to study liver regeneration

The liver has the unique capability of regeneration from various injuries. Different animal models and in vitro methods are used for studying the processes and mechanisms of liver regeneration. Animal models were established either by administration of hepatotoxic chemicals or by surgical approach. The administration of hepatotoxic chemicals results in the death of liver cells and in subsequent hepatic regeneration and tissue repair. Surgery includes partial hepatectomy and portal vein occlusion or diversion: hepatectomy leads to compensatory regeneration of the remnant liver lobe, whereas portal vein occlusion leads to atrophy of the ipsilateral lobe and to compensatory regeneration of the contralateral lobe. Adaptation of modern radiological imaging technologies to the small size of rodents made the visualization of rodent intrahepatic vascular anatomy possible. Advanced knowledge of the detailed intrahepatic 3D anatomy enabled the establishment of refined surgical techniques. The same technology allows the visualization of hepatic vascular regeneration. The development of modern histological image analysis tools improved the quantitative assessment of hepatic regeneration. Novel image analysis tools enable us to quantify reliably and reproducibly the proliferative rate of hepatocytes using whole-slide scans, thus reducing the sampling error. In this review, the refined rodent models and the newly developed imaging technology to study liver regeneration are summarized. This summary helps to integrate the current knowledge of liver regeneration and promises an enormous increase in hepatological knowledge in the near future.

Markers of angiogenesis associated with surgical attenuation of congenital portosystemic shunts in dogs

Background

Dogs with congenital portosystemic shunts (CPSS) have hypoplasia of the intrahepatic portal veins. Surgical CPSS attenuation results in the development of the intrahepatic portal vasculature, the precise mechanism for which is unknown, although new vessel formation by angiogenesis is suspected.

Hypothesis

That the degree of portal vascular development and the increase in portal vascularization after CPSS attenuation is significantly associated with hepatic vascular endothelial growth factor (VEGF) and VEGF receptor 2 (VEGFR2) gene expression and serum VEGF concentration.

Animals

Client‐owned dogs with CPSS undergoing surgical treatment. Forty‐nine dogs were included in the gene expression data and 35 in the serum VEGF data.

Materials and Methods

Dogs surgically treated by partial or complete CPSS attenuation were prospectively recruited. Relative gene expression of VEGF and VEGFR2 was measured in liver biopsy samples taken at initial and follow‐up surgery using quantitative polymerase chain reaction. Serum VEGF concentration was measured before and after CPSS attenuation using a canine specific ELISA. Statistical significance was set at the 5% level (P ≤ .05).

Results

There was a significant increase in the mRNA expression of VEGFR2 after partial attenuation (P = .006). Dogs that could tolerate complete attenuation had significantly greater VEGFR2 mRNA expression than those that only tolerated partial attenuation (P = .037). Serum VEGF concentration was significantly increased at 24 (P < .001) and 48 (P = .003) hours after attenuation.

Conclusions and Clinical Importance

These findings suggest that intrahepatic angiogenesis is likely to occur after the surgical attenuation of CPSS in dogs, and contributes to the development of the intrahepatic vasculature postoperatively.