Blackwell's Five-Minute Veterinary Consult Clinical Companion

Small Animal Gastrointestinal Diseases

Jocelyn Mott, Jo Ann Morrison, Jocelyn Mott, Jo Ann Morrison

• Publisher: Wiley-Blackwell
• Year: 2019
• Print ISBN: 9781119376347
• eBook ISBN: 9781119376323
• Edition: 1
• Topic: Medicine
• Subtopic: Veterinary Medicine

Blackwell's Five-Minute Veterinary Consult Clinical Companion: Small Animal Gastrointestinal Diseases offers a highly accessible resource for the most common and not-so common diseases of the gastrointestinal system, pancreas, liver, and gallbladder in small animals.

• Covers diseases and disorders of the oral cavity and salivary glands, esophagus, stomach, small intestine, colon, anus and perianal region, pancreas, liver, and gall bladder
• Provides a comprehensive yet concise reference to gastrointestinal and hepatologic diseases encountered in daily veterinary practice
• Presents the most important information for each disease in a highly accessible format
• Depicts the clinical conditions discussed with helpful color photographs

Section IX
Diseases of the Liver

Chapter 105
Arteriovenous Malformation of the Liver

DEFINITION/OVERVIEW

• Intrahepatic arteriovenous (AV) malformations are communications between proper hepatic arteries (high pressure) and intrahepatic portal veins (low pressure); this anatomic union results in hepatofugal (away from the liver) splanchnic circulation.
• Blood flows directly from a hepatic artery into the portal vasculature retrograde into the vena cava through multiple acquired portosystemic shunts (APSS).
• Associated with ascites, intrahepatic and extrahepatic portal hypertension, and APSS.
• Uncommon, usually congenital, but may be acquired (surgical injury, trauma, neoplasia).

ETIOLOGY/PATHOPHYSIOLOGY

• Although rare, it is typically congenital in dogs and cats.
• In most cases, a branch of the hepatic artery communicates directly with the portal vein by multiple aberrant shunting vessels within the liver. This creates a high‐pressure system that results in blood flow away from the liver and arterialization of the portal vein. Due to the excessive portal hypertension that results, multiple extrahepatic shunts open to decompress the portal system.

Systems Affected

• Gastrointestinal – vomiting, diarrhea, anorexia, gastrointestinal (GI) bleeding/melena/hematemesis.
• Nervous – ataxia, unresponsiveness, pacing, circling, blindness, seizures, and coma.
• Renal/urologic – stranguria, pollakiuria, hematuria, dysuria, ammonium urate stones.

SIGNALMENT/HISTORY

• Dogs, less common in cats.
• Age‐related presentation (congenital): <2 years.
• No sex or breed predilection.

Risk Factors

• Usually congenital vascular malformations (single or multiple vessels) reflecting failed differentiation of common embryologic anlage.
• Rarely secondary to abdominal trauma, inflammation, neoplasia, surgical interventions, or diagnostic procedures (e.g., liver biopsy).
• Portal hypertension.

Historical Findings

Vague or acute illness – lethargy, anorexia, vomiting, diarrhea, weight loss, polydipsia, dementia, abdominal distension, stranguria/signs of obstructive uropathy, stunted growth.

CLINICAL FEATURES

• Lethargic, poor body condition.
• Ascites in 75% of dogs (Figure 105.1a,b).
• Heart murmurs in 20% of dogs.
• Rarely, bruit auscultated over AV malformation.

Fig. 105.1. (a) Anesthetized hepatic arteriovenous malformation (HAVM) boxer puppy with massive ascites. Dachshund puppy with HAVM prior to embolization (b) and a few weeks after embolization (c) demonstrating dramatically reduced ascites but also the often underestimated cachexia that accompanies this condition due to portal hypertension and reduced gastrointestinal absorption. (d) HAVM intraoperative picture demonstrating too numerous to count acquired extrahepatic shunts secondary to the HAVM portal hypertension. (e,f) Intraoperative pictures of HAVMs demonstrating the vascular dilation present throughout the affected liver lobes(s), multiple shunts with distended renal veins and vena cava, and often some associated bleeding.

DIFFERENTIAL DIAGNOSIS

• Central nervous system (CNS) signs – infectious disorders (e.g., distemper); toxicity (e.g., lead); hydrocephalus; idiopathic epilepsy; metabolic disorders (e.g., hypoglycemia, hypokalemia or hyperkalemia); hepatic encephalopathy (HE) (e.g., acquired liver disease or portosystemic vascular anomalies (PSVA)).
• Abdominal effusion.
  • Pure transudate: ascites, protein‐losing nephropathy, protein‐losing enteropathy, liver...

Table of contents

• Cover
• Table of Contents
• Contributors
• About the Companion Website
• Section I: Clinical Signs of Gastrointestinal Disease
• Section II: Diseases of the Oral Cavity
• Section III: Diseases of the Esophagus
• Section IV: Diseases of the Stomach
• Section V: Diseases of the Intestines
• Section VI: Diseases of the Colon
• Section VII: Diseases of the Pancreas
• Section VIII: Clinical Signs of Hepatobiliary Disease
• Section IX: Diseases of the Liver
• Section X: Diseases of the Biliary Tract
• Index
• End User License Agreement