Morphology of splenocaval congenital portosystemic shunts in dogs and cats

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.

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.

Intramural esophageal location of a portosystemic shunt in a dog with two congenital portosystemic shunts on CT angiography

A 5-year-old male neutered pug with hematuria was presented to a referral hospital after identification of an extrahepatic portosystemic shunt (EHPSS) during abdominal ultrasonography. Computed tomographic-angiography revealed two anomalous blood vessels (left gastroazygous and left gastrophrenic). The left gastroazygous vessel followed an atypical path within the dorsolateral esophageal wall before entering the azygous vein. The morphology of this highly unusual vessel has not, based on the authors' review of the literature, been previously reported. In combination with a second anomalous vessel, this resulted in a unique presentation of an EHPSS. Computed tomography-angiography was essential for diagnosis and surgical planning in this case.

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.

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.

Computed tomography angiography of a congenital extrahepatic splenocaval shunt in a foal

Congenital portosystemic shunts in foals are rare and only a small number of cases have been described. Detailed description of the course of the shunt is lacking in earlier reports. This is the first detailed description of a computed tomography angiography (CTA) displaying an extra-hepatic splenocaval shunt. A 1-month old colt showing increasing signs of dullness, ataxia, circling, lip-smacking and coordination problems was presented. Hyperammonemia was detected and abdominal CTA revealed an extra-hepatic portocaval shunt. During surgery, ligation of the abnormal vessel could not be achieved, and the foal was euthanized because of complications during surgery. CTA provided a detailed overview of portal vasculature. If a portosystemic shunt is suspected in a foal, CTA can be used to confirm the diagnosis and for surgical planning.

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.

Diagnostic imaging for the assessment of acquired abdominal vascular diseases in small animals: A pictorial review

Advances in interventional radiology and surgical techniques now allow complex abdominal diseases to be more successfully treated in small animals. Abdominal vascular alterations, acquired as individual process or as complication of other lesions such as neoplasia, can be life-threatening or at least greatly limit curative interventions of underlying diseases. Computed tomography (CT) and high-definition ultrasonography are now readily available in veterinary referral centers. Yet, there is little information currently available on the use of these modalities for the diagnosis and characterization of these vascular alterations. The purpose of this article is to review the CT and ultrasonographic findings of acquired vascular diseases in the abdomen of dogs and cats, using both the veterinary and human medicine literature as references, and highlighting essential concepts through figures.

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.