Retrospective quantitative assessment of liver size by measurement of radiographic liver area in small-breed dogs

Computed Tomographic Hepatic Volumetry in Dogs with Congenital Portosystemic Shunts

CTHV is a non-invasive and accurate method for assessing liver volume in dogs. CTHV has not been studied in each type of extrahepatic PSS in dogs. This study aimed to use CTHV to compare liver volumes in dogs with different types of PSSs that had been confirmed by computed tomography angiography. Dogs with PSSs were retrospectively included and categorized into IH, EHPC, EHPA, or EHPP shunt groups. Manual CTHV was performed, and the normalized liver volume (nLV) and the difference in nLV from the estimated liver volume calculated based on body weight (LV%diff) was calculated. The study included 57 dogs: 20 IH, 21 EHPC, 9 EHPA, and 7 EHPP. The median nLV (cm3/kg) and LV%diff (%) for each group were as follows: IH 17.3 (-40.4%); EHPC 16.9 (-60.3%); EHPA 15.1 (-56.7%); and EHPP 17.2 (-59.2%), respectively. There were no significant differences in nLV among the PSS types. However, LV%diff was significantly more pronounced in the EHPC and EHPA groups compared with the IH group. Additionally, smaller dogs exhibited more severe microhepatia, with a significant positive correlation between LV%diff and body weight (p < 0.01). These findings suggest that microhepatia severity varies by shunt type and is more severe in smaller dogs, highlighting the need for further research to understand the underlying mechanisms.

Body Weight as a Preferred Method for Normalizing the Computed Tomography-Derived Liver Volume in Dogs without Hepatic Disease

The assessment of liver size is usually performed using radiography in dogs. However, due to wide variations in patients' sizes and body conformations, accurate diagnosis of hepatomegaly or microhepatia is difficult. Computed tomographic (CT) volumetry can quantitatively and accurately measure liver volume. However, a reliable method for the standardization or normalization of volume in dogs without hepatic disease using CT has not yet been established. The purpose of this study was to assess seven different anatomic measures for normalizing liver volume in dogs and determine the tentative range of liver volume in dogs without hepatic disease. We retrospectively searched medical records from 1 January 2017 through to 1 June 2020 and included dogs with abdominal computed tomography without hepatic disease. The liver volume, lengths of four vertebrae (T11, T12, L2, L3), diameter of the abdominal aorta, body weight, and body condition scores (BCSs) of the dogs were recorded. Forty-one client-owned dogs without evidence of hepatic disease were included. The CT-derived liver volume was 813.8 ± 326.5 cm3 (mean ± SD). Body weight was determined to be the most reliable single-variable method for normalizing liver volume, with a raw CT-derived liver-volume-to-body-weight ratio of 22.1 cm3/kg (95% CI: 12.9-31.3 cm3/kg) and regression prediction model of volume = 19 × BWkg + 97. However, a better normalizing factor would likely be provided by the fat-free mass if it can be accurately measured.

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.

Pilot Study: The Effects of Slice Parameters and the Interobserver Measurement Variability in Computed Tomographic Hepatic Volumetry in Dogs without Hepatic Disease

Manual computed tomographic (CT) hepatic volumetry is a non-invasive method for assessing liver volume. However, it is time-consuming with large numbers of slices. Reducing the slice number would expedite the process, but the effect of fewer slices on the accuracy of volumetric measurements in dogs has not been investigated. The objectives of this study were to evaluate the relationship between slice interval and the number of slices on hepatic volume in dogs using CT hepatic volumetry and the interobserver variability of CT volumetric measurements. We retrospectively reviewed medical records for dogs without evidence of hepatobiliary disease with abdominal CT from 2019 to 2020. Hepatic volumes were calculated by using all slices, and interobserver variability was calculated using the same dataset in 16 dogs by three observers. Interobserver variability was low, with a mean (±SD) percent difference in the hepatic volume of 3.3 (±2.5)% among all observers. The greatest percent differences in hepatic volume were decreased when using larger numbers of slices; the percent differences were <5% when using ≥20 slices for hepatic volumetry. Manual CT hepatic volumetry can be used in dogs to non-invasively assess liver volume with low interobserver variability, and a relatively reliable result can be acquired using ≥20 slices in dogs.

YAP regulates the liver size during the fasting-refeeding transition in mice

Liver is the central hub regulating energy metabolism during feeding-fasting transition. Evidence suggests that fasting and refeeding induce dynamic changes in liver size, but the underlying mechanisms remain unclear. Yes-associated protein (YAP) is a key regulator of organ size. This study aims to explore the role of YAP in fasting- and refeeding-induced changes in liver size. Here, fasting significantly reduced liver size, which was recovered to the normal level after refeeding. Moreover, hepatocyte size was decreased and hepatocyte proliferation was inhibited after fasting. Conversely, refeeding promoted hepatocyte enlargement and proliferation compared to fasted state. Mechanistically, fasting or refeeding regulated the expression of YAP and its downstream targets, as well as the proliferation-related protein cyclin D1 (CCND1). Furthermore, fasting significantly reduced the liver size in AAV-control mice, which was mitigated in AAV Yap (5SA) mice. Yap overexpression also prevented the effect of fasting on hepatocyte size and proliferation. Besides, the recovery of liver size after refeeding was delayed in AAV Yap shRNA mice. Yap knockdown attenuated refeeding-induced hepatocyte enlargement and proliferation. In summary, this study demonstrated that YAP plays an important role in dynamic changes of liver size during fasting-refeeding transition, which provides new evidence for YAP in regulating liver size under energy stress.

Computed tomography may detect liver infiltration of canine diffuse hepatic lymphoma

BACKGROUND

In dogs, hepatic lymphoma is characterized by neoplastic lymphocyte infiltration into the liver. Reports on the computed tomography (CT) findings of the liver for canine hepatic lymphoma are few, with only one study of multiple liver lesions type.

OBJECTIVES

The purpose of this study was to retrospectively assess the CT findings of the liver in canine diffuse hepatic lymphoma.

METHODS

As control, five dogs without abnormalities in the liver were included. CT data were analysed, and the following were noted: presence of edge bluntness of the liver, presence of periportal collar sign, the liver size:body weight (BW) ratio and the mean attenuation of liver lesions on pre-contrast, arterial-phase, portal-phase and equilibrium-phase post-contrast images.

RESULTS

On CT examination, edge bluntness of the liver was significantly detected in lymphoma (4/5, 80%), as opposed to the control (0/5, 0%) (p = 0.048, φ = 0.82). The periportal collar sign was detected in lymphoma (3/5, 60%), as opposed to the control (0/5, 0%) (p = 0.17, φ = 0.65). The liver size:BW ratio of lymphoma cases was significantly higher compared to that of the control cases (p = 0.0002, r = 0.92). The mean Hounsfield unit of lymphoma cases in the pre-contrast, arterial-phase, portal-phase and equilibrium-phase images were significantly lower than in the control cases (p = 0.005, r = 0.81; p = 0.0003, r = 0.91; p = 0.01, r = 0.75 and p = 0.02, r = 0.71, respectively).

CONCLUSIONS

Hepatic lymphoma should be a differential for a blunted and enlarged liver with hypoattenuation on CT examination.