New perspectives on the development of extrahepatic portosystemic shunts

A Window Opens and a Shunt Closes: A New Laparoscopic Approach for the Attenuation of the Gastrophrenic Shunt

The portosystemic shunt is characterized by the presence of an anomalous vessel, whether congenital or acquired, that connects the portal circulation to the systemic circulation. Surgical treatment is indicated in congenital cases and involves the progressive occlusion of the anomalous vessel. The objective of this study is to report the use of an innovative and fully laparoscopic technique for the attenuation of a gastrophrenic shunt. The procedure was performed on a two-year-old female German Spitz dog with a history of frequent vomiting and diarrhea. The diagnosis was established through computed tomography. For the procedure, three portals were placed in the left lateral region, employing an ameroid constrictor. This device featured a specific perforation for the passage of a pre-mounted suture, which was subsequently occluded intracorporeally, facilitating the closure of the ring defect. The absence of flow in the anomalous vessel was confirmed five weeks after the procedure. It is concluded that the reported implantation technique represents a new modality for the treatment of this type of shunt using a minimally invasive approach.

Cellophane Banding Without Intraoperative Attenuation of Congenital Gastrophrenic Shunts in 12 Cases

Reports on patients with a gastrophrenic shunt treated with cellophane banding without attenuation are scarce. This case series evaluated the outcomes of cellophane banding without intraoperative attenuation in patients with a congenital left gastrophrenic shunt. Seven client-owned dogs and five client-owned cats with congenital left gastrophrenic shunt were included. Data collected from the medical records included signalment, history, physical examination, clinicopathologic testing, diagnostic imaging (pre and postoperative), perioperative complications, hepatic histopathological evaluation, and clinical outcomes. The application of a cellophane band without intraoperative attenuation of congenital left gastrophrenic shunts resulted in complete closure in 10/11 patients at a median follow-up of 60 days (range: 33-174) based on ultrasound. The mean shunt diameter was 6.1 mm (range: 4.2-8). One dog had partial closure of the shunt at 3 months but was lost to follow-up. One dog died perioperatively from seizures. One cat experienced post-attenuation neurologic signs that completely resolved. Cellophane banding without intraoperative attenuation appeared to be a safe and potentially effective approach for managing gastrophrenic shunts. The percentage of shunt closure observed in this cases series is higher than that historically reported for other shunt localizations. Shunt localization may influence closure. Residual shunting may not be associated with shunt diameter. Further studies with larger sample sizes and standardized follow-ups are needed to confirm its efficacy.

[Congenital porto-phrenico-pulmonary shunt in a cat]

An 8-month-old castrated male Birman showing hematuria, stranguria, and intermittend head tremor was presented for further diagnostic work-up on suspicion of hepato-encephalopathic syndrome. Computed tomography examination revealed a shunt vessel emanating from the vena gastrica sinistra which connected to both the vena phrenica sinistra and a pulmonary vessel from the left caudal lung lobe draining into the left atrium. This represents the first case report describing the radiologic appearance, surgical ligation as well as the post-operative outcome of a cat with such a shunt form.

Single Posthepatic Portosystemic Shunt Communicated With Internal Thoracic Vein and Azygos Continuation of the Caudal Vena Cava in a Dog

Computed tomography angiography (CTA) was performed under general anaesthesia on a 7-month-old toy poodle that was referred with the chief complaints of salivation and neurological symptoms. The CTA revealed a rare form of posthepatic portosystemic shunt (PSS) via the suspected persistent left umbilical vein communicating with the internal thoracic vein in addition to an azygos continuation of the caudal vena cava (CVC). The patient underwent surgery for partial ligation of PSS on Day 4 after the initial examination. On Day 71, after the initial examination, a second surgery was performed for complete ligation. Approximately 10 years have passed since the patient's second surgery, and he is still healthy, and generally in good condition. Although the morphology of the shunt in this case was unusual and was accompanied by an azygos continuation of the CVC, a favourable course of treatment was obtained by ligating the shunt vessel. This case report suggests that CTA can reveal the complex morphological characteristics like our case. Surgical treatment in this case resulted in favourable progress, similar to that in dogs with commonly observed extrahepatic PSS.

Computed tomographic evaluation of portal vein indices in cats with the extrahepatic portosystemic shunts

IMPORTANCE

The portal vein to aorta (PV/Ao) ratio is used to assess the clinical significance of extrahepatic portosystemic shunt (EHPSS). Previous studies using computed tomography (CT) were conducted in dogs but not in cats.

OBJECTIVE

This study aimed to establish normal reference values for PV indices (PV/Ao ratio and PV diameter) in cats and determine the usefulness of these for predicting symptomatic EHPSS.

METHODS

This study included 95 dogs and 114 cats that underwent abdominal CT. The canine normal (CN) group included dogs without EHPSS. The cats were classified into feline normal (FN, 88/114), feline asymptomatic (FA, 16/114), and feline symptomatic (FS, 10/114) groups. The PV and Ao diameters were measured in axial cross-sections.

RESULTS

The group FN had a higher PV/Ao ratio than the group CN (p < 0.001). Within the feline groups, the PV indices were in the order FN > FA > FS (both p < 0.001). The mean PV diameter and PV/Ao ratio for group FN were 5.23 ± 0.77 mm and 1.46 ± 0.19, respectively. The cutoff values between groups FN and FS were 4.115 mm for PV diameter (sensitivity, 100%; specificity, 97.7%) and 1.170 for PV/Ao ratio (90%, 92.1%). The cutoff values between group FA and FS were 3.835 mm (90%, 93.8%) and 1.010 (70%, 100%), respectively.

CONCLUSIONS AND RELEVANCE

The results demonstrated significant differences in PV indices between dogs and cats. In cats, the PV/Ao ratio demonstrated high diagnostic performance for symptomatic EHPSS. The PV diameter also performed well, in contrast to dogs.

Enlargement of the hepatic artery is present in dogs with a congenital extrahepatic portosystemic shunt and is independent of shunt insertion into the systemic circulation

The accurate diagnosis of portovascular anomalies has been facilitated by improvements in diagnostic imaging technology. In humans, hepatic arterial blood flow changes in response to the reduction in portal blood flow. The hepatic arterial buffer response characterizes an intrinsic regulatory mechanism in response to reduced portal venous blood flow, which results in hepatic arterial enlargement. At the authors' institution, enlargement of the hepatic artery has been anecdotally observed in a population of dogs with extrahepatic portosystemic shunting, consistent with previous literature that documents variability in hepatic arterial size. In this retrospective, blinded, analytical study, a hepatic artery:aorta (Ha:Ao) ratio was assessed on CT studies from 112 dogs, with (n = 43) and without (n = 69) an extrahepatic congenital portosystemic shunt in order to compare the hepatic artery size independent of body weight between the two populations. A significant increase in the Ha:Ao ratio was documented in dogs with an extrahepatic portosystemic shunt (EHPSS) compared with those dogs with no EHPSS independent of the location of shunt insertion into the systemic circulation (P < .001). Three cases had repeat CT after surgery, and all had Ha:Ao ratio reductions following treatment. The authors propose that this may be an additional imaging feature observed in dogs with an EHPSS.

Clinical presentation and short-term outcomes of dogs ≥15 kg with extrahepatic portosystemic shunts

OBJECTIVE

To describe demographics, clinical presentation, shunt anatomy, clinical progression, and complications in large dogs ≥15 kg with single extrahepatic portosystemic shunts (EHPSS) treated with or without surgery.

STUDY DESIGN

Multicenter retrospective (10 university hospitals, one private referral institution).

ANIMALS

Dogs ≥15 kg (n = 63).

METHODS

Medical records of dogs ≥15 kg diagnosed with EHPSS between January 01, 2005 and December 31, 2020 were reviewed. Dogs had a minimum follow-up of 90 days. Signalment, clinical signs, diagnostics, shunt anatomy, treatment interventions, and perioperative complications were assessed.

RESULTS

Median age was 21.9 months (IQR: 9-36.8). The breed most represented was the Golden retriever (17/63 dogs). Portocaval (17/63) and splenocaval (15/63) shunt configurations were most common. Portal vein hypoplasia was noted in 18 imaging reports. Of the surgically treated dogs, 14/45 (35.6%) had short-term complications, and 3/45 (6.7%) had shunt-related deaths. Medical management was discontinued in 15/40 and reduced in 9/40 of surviving dogs who had surgical attenuation. All medically managed, nonattenuated dogs (18/18) were maintained on their original shunt-related medication regimens.

CONCLUSIONS

Clinical presentation of dogs ≥15 kg with extrahepatic portosystemic shunts was similar to the more commonly reported small breed dogs. Surgical management of single EHPSS in large dogs ≥15 kg had similar clinical short-term outcomes as small breed dogs.

CLINICAL SIGNIFICANCE

Clinicians should be aware that large breed dogs with EHPSS share similar characteristics and clinical outcomes to small breed dogs. The significance of the presence of a hypoplastic portal vein warrants further research. Surgical treatment is a viable option for large breed dogs with EHPSS.

Diagnosis and treatment of a congenital portosystemic shunt in a ferret (Mustela putorius furo)

A 3-year-old female neutered ferret presented with progressive weight loss was diagnosed with portosystemic shunting based on increased fasting bile acids, rectal ammonia tolerance testing and advanced imaging. Ammonia reference values were determined in 16 healthy ferrets. A congenital extrahepatic spleno-caval shunt was visualised with ultrasonography and CT angiography of the abdomen. Complete surgical shunt closure by suture ligation was performed, without clinical improvement after surgery. Euthanasia was elected 4 months postoperatively because the clinical condition deteriorated. This is a case report of advanced diagnostics and surgical treatment of a congenital extrahepatic portosystemic shunt in a ferret, demonstrating rectal ammonia tolerance testing and imaging as feasible techniques for the diagnosis.

Diameter of the shunt vessel in dogs with incidental extrahepatic portosystemic shunts

Clinical signs of extrahepatic portosystemic shunts (EHPSS) depend on the amount of blood shunted. In this study, dogs with EHPSS without noticeable clinical signs including 34 left gastro-phrenic, 3 left gastro-azygos and 2 left spleno-gonadal shunts were evaluated. In dogs with EHPSS without noticeable clinical signs, the median maximum diameter of the shunt vessel was significantly smaller compared to PV (p < 0.005). Whenever the diameter of the EHPSS is small in relation to the diameter of the PV, it seems likely that no obvious clinical signs of EHPSS are observed by the owners.

Congenital Portosystemic Shunts in Dogs and Cats: Classification, Pathophysiology, Clinical Presentation and Diagnosis

Congenital portosystemic shunts (CPSS) are abnormal vascular communications between the portal and the systemic circulation, bypassing the hepatic parenchyma and resulting in liver hypoplasia and hepatic insufficiency. Such connections develop in utero and persist postnatally. CPSS are among the two most common congenital vascular anomalies of the liver in small animals, along with primary hypoplasia of the portal vein without portal hypertension (PHPV without PH). CPSS can be extrahepatic (ECPSS), most commonly diagnosed in small and toy breed dogs and cats, or intrahepatic (ICPSS), most commonly seen in large breed dogs. Single ECPSS is the most common type encountered in both dogs and cats. Clinical signs of CPSS are non-specific and may wax and wane, while laboratory findings can raise clinical suspicion for CPSS, but they are also not specific. Definitive diagnosis will be established by evaluation of liver function tests, such as determination of fasting plasma ammonia (FA) levels, and pre- and postprandial serum bile acids concentrations, and diagnostic imaging. The purpose of this article is to review the definition, classification, pathogenesis, clinical presentation, and diagnosis of CPSS in dogs and cats, highlighted by the authors' clinical experience.

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.

Congenital portopulmonary shunt in a cat

A 9-year-old spayed female crossbreed cat with chief complaints of anorexia and hypersalivation had high serum concentrations of ammonia and fasting and postprandial total bile acid. Therefore, she was referred to our hospital. On the first evaluation, haematology, serum chemistry, radiography and ultrasonography findings suggested that she had a congenital portosystemic shunt. CT revealed a shunt vessel from the left gastric vein to the left pulmonary vein. During median celiotomy and sternotomy, gross findings and mesenteric portography revealed abnormal vessel shunting from the left gastric vein to the left pulmonary vein. Complete ligation of the shunt vessel was achieved. She recovered without any complications. Postoperative serum chemistry revealed that ammonia and total bile acid levels decreased to within the reference intervals. This report is the first to describe the clinical features and surgical outcome of a cat with a congenital portopulmonary shunt.

Percutaneous transvenous coil embolization of an extrahepatic portosystemic shunt in a cat

Case summary

A 10-month-old male domestic shorthair cat presented for surgical treatment of a congenital portosystemic shunt. The cat had a history of lethargy and ptyalism. Pre- and postprandial bile acids were markedly elevated. CT was performed, which revealed a single, congenital, left gastrophrenic, extrahepatic portosystemic shunt. A minimally invasive surgical approach was considered by transjugular percutaneous coil embolization of the venous shunt, which was performed without complications. Follow-up protein C and serum biochemical analyses were performed at 1, 2 and 5 months postoperatively, and were improved. The cat is alive and clinically normal 11 months postoperatively.

Relevance and novel information

This is the first report of percutaneous transvenous coil embolization for the treatment of an extrahepatic portosystemic shunt in a cat. The outcome was excellent in this patient, with no complications and complete resolution of clinical signs.

Peripartum clinical manifestations of a mesentericorenocaval shunt in a Burmese cat

Case summary

A 3-year-old entire female Burmese cat was presented for investigation of intermittent lethargy during gestation followed by persistent hypersalivation and ataxia postpartum. The cat had queened three litters in total, with clinical signs worsening during the most recent lactation period. Mild anaemia (26%), hypoglycaemia (2.4 mmol/l; reference interval [RI] 3.9–8.3 mmol/l) and increased postprandial serum bile acids (74 µmol/l; RI <25 µmol/l) were identified on initial bloodwork. Multiphase contrast-enhanced CT identified a mesentericorenocaval portosystemic shunt; this was attenuated surgically with an ameroid constrictor. Clinical signs resolved after surgery. Follow-up 3 months postoperatively revealed normal pre- and postprandial serum bile acids (2 µmol/l and 3 µmol/l, respectively) with repeat CT identifying evidence of shunt attenuation. The cat continued to be healthy and free of clinical signs 12 months postoperatively.

Relevance and novel information

Mesentericorenocaval portosystemic shunt morphology has not been previously reported in the cat and should be considered as a differential diagnosis for cats presenting with peripartum onset of malaise, ptyalism or ataxia.

Classification of portosystemic shunts entering the caudal vena cava at the omental foramen in dogs

OBJECTIVE

To re-evaluate the anatomy and classification of congenital extrahepatic portosystemic shunts entering the caudal vena cava at the level of the omental foramen.

MATERIAL AND METHODS

A retrospective review of a consecutive series of dogs undergoing CT angiography as part of the diagnostic work-up for a congenital extrahepatic portosystemic shunt.

RESULTS

In total, 53 dogs met the inclusion criteria revealing four anatomically distinct omental foramen shunt types; one of which (32 of 53 dogs) showed no shunting blood flow through the right gastric vein and three of which (21 of 53 dogs) involved shunting flow through this vessel. The anatomy of these four distinct shunt types, as defined by CT angiography, was found to be highly consistent. In all cases, regardless of the tributary vessels, the left gastric vein was the final vessel that communicated with the caudal vena cava. Using these findings, a more accurate naming classification for congenital portosystemic shunts entering the caudal vena cava at the level of the omental foramen was proposed.

CLINICAL SIGNIFICANCE

A precise pre-treatment anatomical classification of congenital extrahepatic portosystemic shunts entering the caudal vena cava at the level of the omental foramen is important for a more complete understanding of the severity of clinical signs and prognosis, and for the better communication between clinicians and researchers in this clinical field.

Canine intrahepatic portosystemic shunt insertion into the systemic circulation is commonly through primary hepatic veins as assessed with CT angiography

Congenital intrahepatic portosystemic shunts (IHPSS) in dogs are traditionally classified as right, left, or central divisional. There are few descriptive studies regarding the variation of IHPSS within these categories. This multicenter, analytical, cross-sectional study aimed to describe a large series of dogs with CT angiography (CTA) of IHPSS, hypothesizing that there would be variation to the existing classification. Ninety CTA studies were assessed for IHPSS type, insertion, and the relationship of the insertion to the primary hepatic veins. Ninety-two percent of IHPSS inserted into a primary hepatic vein (HV) or phrenic vein, 8% inserted directly into the ventral aspect of the intrahepatic caudal vena cava. The most common IHPSS type was a single right divisional (44%), including those inserting via the right lateral HV or the caudate HV. Left divisional IHPSS (33%) inserted into the left HV or left phrenic vein. Central divisional IHPSS (13%) inserted into the quadrate HV, central HV, dorsal right medial HV, or directly into the ventral aspect of the intrahepatic caudal vena cava. Multiple sites of insertion were seen in 9% of dogs. Within left, central, and right divisional types, further subclassifications can therefore commonly be defined based on the hepatic veins with which the shunting vessel communicates. Relating IHPSS morphology to the receiving primary HV could make IHPSS categorization more consistent and may influence the type and method of IHPSS attenuation recommended.

Feline abdominal ultrasonography: what's normal? what's abnormal? Hepatic vascular anomalies

PRACTICAL RELEVANCE

Abdominal ultrasound plays a vital role in the diagnostic work-up of many cats presenting to general and specialist practitioners. Although hepatic vascular anomalies are less common than disorders of the hepatic parenchyma and biliary tree, our understanding and recognition of these is gradually increasing with advancements in ultrasound technology and image quality.

CLINICAL CHALLENGES

Despite ultrasonography being a commonly used modality, many practitioners are not comfortable performing an ultrasound examination or interpreting the resulting images. Even differentiating between normal variation and pathological changes can be challenging for all but the most experienced. In addition, some views may be obscured by overlying structures; for example, the termination of a shunt entering the left phrenic or azygous veins is often difficut to see due to the high probability of lung passing between the shunt and the transducer as the cat breathes.

EQUIPMENT

Ultrasound facilities are readily available to most practitioners, although use of ultrasonography as a diagnostic tool is highly dependent on operator experience.

AIM

This review, part of an occasional series on feline abdominal ultrasonography, discusses the appearance of various hepatic vascular anomalies. It is aimed at general practitioners who wish to improve their knowledge and confidence in feline abdominal ultrasound and is accompanied by high-resolution images. Ultrasound of the liver and biliary tree were discussed in articles published in January and May 2019, respectively.

EVIDENCE BASE

Information provided in this article is drawn from the published literature and the author's own clinical experience.

Implications of shunt morphology for the surgical management of extrahepatic portosystemic shunts

OBJECTIVE

To describe the implications of extrahepatic portosystemic shunt morphology for the chosen site of shunt closure in dogs and cats.

METHODS

A retrospective review of a consecutive series of dogs and cats managed for congenital extrahepatic portosystemic shunts.

RESULTS

In total, 54 dogs and 10 cats met the inclusion criteria, revealing five distinct shunt types: left gastrophrenic, right gastrocaval (types Ai, Aii and Aiii), splenocaval, colocaval and left gastro-azygos. Without exception, findings of computed tomography angiography and direct gross observations at the time of surgery confirmed four consistent sites of communication between the anomalous shunting vessel and the systemic venous system: the caudal vena cava at the level of the epiploic foramen; the left phrenic vein at the level of the oesophageal hiatus; the azygos vein at the level of the aortic hiatus; and the caudal vena cava or iliac vein at the level of the 6th or 7th lumbar vertebrae. The use of intraoperative mesenteric portography was effective for confirming that at the time of surgery all portal tributary vessels were proximal to the point of shunt attenuation.

CONCLUSIONS

Findings confirmed that for the common types of extrahepatic portosystemic shunts there were only four consistent sites of communication between the shunt and the systemic venous system. This information supports the use of a systematic approach for the location and attenuation of shunts in dogs and cats.