The recent advances in the understanding of cholangiopathies
The biliary tree is formed by intrahepatic and extrahepatic bile ducts,
is lined by biliary epithelial cells (the cholangiocytes) and also has peribiliary glands around the intrahepatic large bile ducts and extrahepatic bile ducts.
Cholangiopathies are considered to be all pathologies affecting the biliary tree and targeting cholangiocytes.
In general,
cholangiopathies lead to a change in normal cholangiocyte function,
and encompass a series of diseases that are commonly chronic,
many without effective treatment,
progressive and potentially fatal.
However,
each cholangiopathy has a different pathogenesis and the understanding of this pathogenesis may lead to a therapeutic evolution of this group of diseases.
Some primary pathophysiological mechanisms have already been elucidated on cholangiopathies,
such as: primary ciliary dysfunction mechanism,
specific miRNA expression,
influence of gastrointestinal hormones,
bile acids,
angiogenic factors,
steroids,
neuropeptides and neurotransmitters,
and other abnormal hormones in general,
abnormal mechanism of apoptosis and cellular repair,
as well as the mechanism reactive to various injuries.
Each of these mechanisms leads to a cellular response of the cholangiocyte to maintain its homeostasis or adaptation to an inflammatory state,
which ultimately leads to a change in normal cholangiocyte function and to the development of cholangiopathy.
According to the several mechanisms described above,
it was proposed to classify cholangiopathies into several categories: genetic,
immune-mediated,
idiopathic,
infectious,
vascular,
obstructive,
among others.
However,
these categories overlap and more than one pathogenic mechanism may be operative in a given cholangiopathy.
We believe it is important for the radiologist to be familiar with the classification and diseases that are part of this group (which have a molecular basis),
as well to be aware of the new terminologies adopted.
Current classification of cholangiopathies
There is a lot of overlapping terms in the scientific literature with no relevance to cholangiopathies.
However,
according to the current scientific literature,
we have the following definitions:
- Cholangiopathies: Diseases that mainly target the biliary tree (cholangiopathies) can be divided into several categories according to the pathogenetic mechanism involved.
- Cholangitis: one of the mechanisms of cholangiopathy,
is characterized by biliary epithelial damage with inflammatory cell infiltration.
Some cholangitis are also associated with ductal and periductal fibrosis.
It occurs along the biliary tree,
and the term cholangitis is used for inflammatory damage to bile ductules.
They can be divided into suppurative and nonsuppurative forms.
- Sclerosing cholangitis: subtype of cholangitis (inflammatory form) with evident ductal fibrosis developed as a consequence of long-standing bile duct inflammatory,
obstruction,
or ischemic injuries.
- Primary sclerosing cholangitis: (PSC) is defined by idiopathic involvement of the biliary tract,
and exclusion of other possible causes of cholangiopathy is mandatory.
It is a rare disease that predominates in male patients and around the 4th decade of life.
Approximately 60 to 80% of patients with PSC have inflammatory bowel disease,
about 85% with ulcerative colitis and 15% with Crohn's disease.
Drug therapy is limited to symptomatic relief and attempted retardation of progression,
and liver transplantation is the only curative therapy.
- Secondary sclerosing cholangitis: (SSC) is characterized by the identification of a causal factor responsible for cholangiopathy,
has a wide spectrum of etiologies,
but its prevalence is not yet known.
Its main reported causes are: recurrent pyogenic cholangitis,
ischemic,
HIV-associated,
eosinophilic,
IgG4-related,
among others.
The SSC has a phenotypic,
clinical and radiological similarity with the PSC,
but its natural history has a worse outcome in relation to the primary etiology.
Its treatment is specific according to the identified cause,
and the lesion may reverse in some cases.
- Primary biliary cholangitis: formerly known as primary biliary cirrhosis.
Although accepted since 2015,
we still find the old term in many of the previous articles and book texts.
The change of nomenclature was mainly requested by the associations of patients affected by this disease,
due to the stigma that the term cirrhosis carries,
popularly associated with alcohol abuse and reserved prognosis.
The alteration of this nomenclature has an essentially psychosocial value for the patients affected by this disease.
The change in this term removes the sensation of terminal illness implied in the term cirrhosis,
improves their opportunities in the workplace and in their everyday social lives.