Abstract
Many pathologies can occur in the periportal space and manifest as fluid accumulation, visible in Computed tomography (CT) images as a circumferential region of low attenuation around the intrahepatic portal vessels, called periportal halo (PPH). This finding is associated with different types of hepatic and extra-hepatic disease in humans and remains a non-specific sign of unknown significance in veterinary literature. The aim of this study was to investigate the prevalence of PPH in a population of patients undergoing CT examination and to assess the presence of lesions related to hepatic and extra-hepatic disease in presence of PPH. CT studies including the cranial abdomen of dogs and cats performed over a 5-year period were retrospectively reviewed. The prevalence of PPH was 15% in dogs and 1% in cats. 143 animals were included and the halo was classified as mild, moderate and severe, respectively in 51%, 34% and 15% of animals. The halo distribution was generalized in 79 cases, localized along the second generation of portal branches in 63, and along the first generation only in one. Hepatic disease was present in 58/143 and extra-hepatic disease in 110/143 of the cases. Main cause of hepatic (36%) and extra-hepatic disease (68%) was neoplasia. Associations between halo grades and neoplasia revealed to be not statistically significant (p = 0.057). In 7% of animals the CT examination was otherwise unremarkable. PPH is a non-specific finding, occurring in presence of a variety of diseases in the examined patient population.
Highlights
The periportal space is an anatomic region that surrounds the portal vein (PV) and its branches and is embedded in a loose connective tissue that contains the hepatic artery, bile duct, nerves and lymphatic vessels
Final decisions for subject inclusion or exclusion were made based on jointly consensus of 2 of the authors (SD and FDC), taking into account the following objective criteria: Animals were included in the study if a periportal halo (PPH) was present in a complete computed tomography (CT) examination and if medical records of the patients were available for review
1168 abdominal CT examinations were reviewed for Institution 1, and 125 of 858 (15%) dogs and 4 of 310 (1%) cats showed PPH on CT studies
Summary
The periportal space is an anatomic region that surrounds the portal vein (PV) and its branches and is embedded in a loose connective tissue that contains the hepatic artery, bile duct, nerves and lymphatic vessels. Hypoattenuating periportal halo on CT can occur in a variety of diseases space via hematogenous, biliary, lymphatic, neural and peritoneal routes and manifest as fluid accumulation. This leads to a distention of the interstitial tissue around the portal triad structures and appears as a circumferential region of low attenuation parallel to the intrahepatic portal system, called periportal halo (PPH) [1]. These circumferential regions parallel to the portal branches are hyperattenuating (attenuation range -3 to 10 Hounsfield units) [3] compared to the density of fat tissue [4]. Other synonyms that have been used in the radiology literature include “periportal collar”, “periportal tracking”, “periportal ring” or “tram line” and “periportal hypodense zones” [5–7]
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