The periportal region is the anatomical space arranged around the portal vein and it includes branches of the hepatic artery,
bile duct,
nerves,
lymph vessels and virtual space.
(Fig 1) Periportal pathology may involve any of these structures and be diffuse or focal.
Radiological findings may be helpful in the differential diagnosis of this pathology.
Over 80% of lymph from the liver is drained by lymphatic collectors running adjacent to the portal veins and bile ducts at the hepatic hilium,
and they will drain into the cistern chyli.
(Fig 2) The rest of the lymph is drained by lymphatic vessels accompanying the hepatic veins,
and they drain directly into the thoracic duct or retrosternal lymphatics.
Lymph originates mainly in the hepatic sinusoids,
for the free passage of fluid and plasma proteins to the presinusoidal space of Disse,
which continuous the capillaries of the connective tissue that surrounds the portal vessels,
arterioles and bile ducts.
(Fig 3) Compression of these channels leads to dilation of perivascular lymphatic vessels (1).
Perivascular periportal lymphedema was first described in animal experiments after stopping the flow of hepatic lymph channels,
appreciating return to normal lymphatic drainage at 4-6 weeks after regeneration of the lymphatic vessels.
The first human description was given by Marincek TC et al (2) in 1986 in patients who had undergone a liver transplant,
and was attributed to disruption of lymphatic drainage of the transplanted liver.
Periportal space can be increased by inflammatory processes,
tumour infiltration,
bile duct proliferation,
haemorrhage or oedema.
This increase is expressed with a radiological sing called periportal halo,
resulting in a periportal soft tissue hypointensity in TC,
hyperintensity of signal in T2-weighted sequences in RM (3),
and an increased thickness and echogenicity in ultrasound.
(4,5) The periportal halo,
also called periportal cuffing in ultrasound,
can affect the main portal vein or its branches,
in which case the pattern can also be called "starry sky" or "Stars and Stripes".
Periportal cuffing can be hyper or hypoechogenic.
Hyperechogenic periportal cuffing is much more frequent (91%) than hypoechogenic periportal cuffing (9%).
Most times,
hypoechoic periportal cuffing is associated with malignancies,
particularly hematologic,
while hyperechogenic periportal cuffing is more frequent in patients with inflammatory bowel disease.
Hypoechoic periportal cuffing may be due to multiple causes.
One of them is the periportal cellular infiltrate,
as found in Langerhans cell histiocytosis,
the Chediak-Higashi syndrome and acute myeloid leukaemia,
in which case the hypoechoic halo surrounding the main portal vein and its branches is explained by transient lymphedema caused by obstruction of small lymphatic vessels,
secondary to direct periportal infiltration by malignant cells,
which disappeared within two weeks of starting treatment with chemotherapy.
It may also be the result of a lymphedema by lymphatic stasis either secondary to hepatic transplantation,
abdominal trauma (particularly in the absence of liver intraparenchymal damage) or periportal malignant lymphadenopathy (such as in ovarian carcinoma).
It can also be observed in primary liver tumours,
like undifferentiated hepatoblastoma,
as well as in patients with chronic hepatobiliary diseases describing periportal inflammation on histological examination with accumulation of inflammatory cells around the portal tracts and vasodilatation.
It also has been described recently a hypoechoic periportal halo in portal vein and its branches in cases of type 1 autoimmune pancreatitis,
which disappears after treatment,
and the hepatic venooclusive disease.
Other causes may be periportal echolucency due to perivascular inflammation,
possibly secondary to hepatitis or histiocytosis with triaditis portal.
Hyperechoic periportal cuffings are seen like thick echogenic bands around the portal veins in the periportal connective tissue of the portal triad,
and will be mainly in acute hepatitis,
which is observed frequently with an enlargement of the liver with a diffusely decreased echogenicity of the parenchyma that determines a relative increase in the echogenicity of the portal vein walls and explains the sonographic appearance of the liver in "starry sky" or centrilobular pattern.
Also an edema of the gallbladder fossa and thickening with increased echogenicity of the venous ligament,
falciform ligament,
porta hepatis and periportal connective tissue can be seen in acute hepatitis.
It should be remembered that a normal hepatic echotexture not exclude the diagnosis of acute hepatitis,
and in most cases the liver will have a normal sonographic appearance.
Hyperechogenic periportal cuffings also may result from liver inflammation that occurs in inflammatory bowel disease resulting from abnormal cell passage from the intestinal mucosa into the portal system via enterohepatic circulation.
You can see them in cases of hepatobiliary diseases and other processes commonly associated with inflammatory bowel disease and primary sclerosing cholangitis,
pericholangitis,
gallbladder stones and acute cholecystitis (Figs 4,5),
and in chronic hepatitis and pancreatitis (Figs 7 ,
8,10,11).
In patients with closed liver trauma it’s frequently observed periportal halos due to blood or venous pressure elevation.
The periportal oedema can cause this sign in patients with congestive heart failure and secondary hepatic congestion,
hepatitis failure or acute viral hepatitis.
We also can see this sign in cases of lymphatic tumour infiltration of the porta hepatis that obstructs the lymphatic drainage,
and in liver transplant or bone marrow patients.
They are also described in cases of primary biliary cirrhosis and scrub typhus or tsutsugamushi disease.
The CT and MR findings of diffuse fatty infiltration of the periportal space have been described as a different pathology to the periportal oedema.
This finding has been described in alcoholic patients,
either alone or in combination with fatty infiltration around the hepatic veins.
Periportal fatty infiltration may be segmental.
Sometimes periportal fatty tissue can be found around the left portal vein as normal finding,
and usually indicates a path extra hepatic portal vein.