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

Abstract

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.

Peripartum clinical manifestations of a mesentericorenocaval shunt in a Burmese cat

“…PSSs are anomalous vascular communications between the portal and systemic venous circulation, permitting blood to bypass hepatic processing; these can be aetiologically classified as congenital or acquired. 1 – 3 Feline PSS is uncommonly seen, with a reported incidence of approximately 2.5 per 10,000 cats managed at referral institutions. 4 Four main subtypes predominate feline extrahepatic PSS morphology: left gastrophrenic, splenocaval, left gastrocaval and those originating from the left colic vein, with the former three representing 60–92% of reported cases.…”

“…Congenital PSSs, which are more common in cats, are single abnormal connections between vitelline and cardinal vasculatures that persist post-embryologically, whereas acquired shunts develop secondary to portal hypertension, opening pre-existing fetal vessels of lower resistance between the portal and systemic circulation to offload hydrostatic pressure. 1–3,13–15 Acquired shunt morphology commonly depicts multiple vessels connecting the portal system directly to the perirenal CdVC, renal or gonadal veins. 14–16 True feline acquired PSSs are rarely reported, however.…”

Anatomical and Three-Dimensional Study of the Female Feline Abdominal and Pelvic Vascular System Using Dissections, Computed Tomography Angiography and Magnetic Resonance Angiography

“…In feline medicine, radiography and ultrasound have been the main diagnostic imaging techniques used for the abdomen and pelvis [ 19 , 20 ]. However, the use of CTA and MRA in cats have made it possible to obtain better resolution of the circulatory system.…”