Congenital absence of the portal vein in a cat

Optimal delay for triple-phase hepatic computed tomography using a bolus-tracking technique in cats

The objective of this study was to provide the characteristics of hepatic computed tomography images and optimize their transition delay with a bolus-tracking technique for triple-phase hepatic computed tomography in cats. Dynamic triple-phase computed tomography was performed in nine healthy cats. The upper third of the liver was dynamically scanned every 0.5 s for 40 s. The time density curves of the aorta and hepatic parenchyma mean enhancement were analyzed. Triple-phase hepatic computed tomography was performed three times with a bolus trigger of 200 Hounsfield units of aortic enhancement. The transition delays of the arterial, portal, and hepatic parenchymal phases were respectively 0, 5 and 60 s in the first scan; 2, 7 and 62 s in the second scan; and 4, 9 and 64 s in the third scan. All computed tomography images were evaluated by a certificated radiologist. The arterial vessels and their main branches were well enhanced at a 2 s transition delay. The contrast of the portal vein to the liver parenchyma was most obvious at a 7 s transition delay. The mean enhancement of the hepatic parenchyma peaked at a 62 s transition delay, whereas the degree of enhancement of the hepatic vasculature decreased. In this study, the recommended transition delays for the arterial, portal, and hepatic parenchymal phases were 2 s, 7 s and 62 s, respectively, after triggering at 200 Hounsfield units of aortic enhancement. This information may be helpful in diagnosing feline liver diseases and provides a key reference for the clinical implementation of CT.

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.