My niece, aged about 40, has recently been diagnosed with a disease of
the liver which goes by the name of something like Carolla's Disease.
It is genetic in origin and can only be cured by a transplant but it
has caused enlargement of the bile duct which is partially blocking
her portal vein which may require a cadaver transplant. Does this tell
you anything and if so, can you identify this apparently very rare
disease? David Joy

Dear gaudium,

The disease your niece suffers from is, without any doubt, "Caroli's
Disease", also known as Caroli Disease, Caroli's Syndrome, or Caroli
Syndrome.

Here is a description and a Clinical Synopsis of Caroli's Disease:

"Congenital polycystic dilatation of intrahepatic bile ducts was first
described by Caroli et al. (1958). The condition is characterized by
polycystic segmental dilatation of the intrahepatic bile ducts and a
marked predisposition to cholangitis and liver abscess. As indicated
in the discussion of infantile polycystic kidney disease, involvement
of the liver compatible with Caroli disease is seen in association
with that of kidney disease and possibly also with the adult form of
polycystic kidney disease. It is possible that isolated Caroli disease
occurs as a genetic entity in some families."

GI : 
Congenital polycystic dilatation of intrahepatic bile ducts 
Cholangitis 
Liver abscess 
Epigastric pain 
Vomiting 
Hepatomegaly 
Bleeding esophageal varices 
Portal hypertension 

Misc : 
Polycystic kidney disease association 
Recurrent episodic fever 

Inheritance : 
Autosomal dominant

(Source: National Center for Biotechnology Information)

For more information on Caroli's Disease and the possible treatments,
please have a look at the following websites:

National Center for Biotechnology Information: OMIM Database - Caroli
Disease, Isolated
http://www.ncbi.nlm.nih.gov/htbin-post/Omim/dispmim?600643

eMedicine: Caroli Disease
http://www.emedicine.com/ped/topic325.htm

Health On The Net Foundation: Rare Diseases - Caroli's Disease
http://www.hon.ch/HONselect/RareDiseases/C06.130.120.175.html

Northwestern Memorial Hospital: Caroli's Disease
http://health_info.nmh.org/Library/HealthGuide/IllnessConditions/topic.asp?hwid=nord606

Search terms used:
"genetic diseases" database
://www.google.de/search?q=%22genetic+diseases%22+database&ie=UTF-8&oe=UTF-8&hl=de&meta=
"Caroli's disease"
://www.google.de/search?hl=de&ie=UTF-8&oe=UTF-8&newwindow=1&q=%22Caroli%27s+disease%22&meta=
"Caroli disease" genetic
://www.google.de/search?hl=de&lr=&ie=UTF-8&oe=UTF-8&newwindow=1&q=%22Caroli+disease%22+genetic&spell=1

I hope that this answers your question and that the treatment of your
niece will be successful.
Best regards,
Scriptor

Perfectly adequate broad answer with suggestions pointing the way to
further research.