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Gut Supplement, 1991, S 116-S 122

Cystic disease of the liver and biliary tract

A Forbes, I M Murray-Lyon

AbstractThe widespread availability of ultrasoundimaging has led to more frequent recognitionof cystic disease affecting the liver and biliarytract. There is a wide range ofpossible causes.Cystic disease of infective origin is usuallycaused by an Echinococcal species, or as thesequel of a treated amoebic or pyogenicabscess. The clinical and radiological featuresare often then distinctive and will not be dweltupon in this review, except in respect of theircontribution to the differential diagnosis ofnon-infective disorders. The principal non-infective cysts can be conveniently dividedbetween the simple cyst, the polycystic syn-dromes (usually with coexistent renal disease),Caroli's syndrome, and choledochal cysts.The overlap between constituent members ofthese groups, and the association of cysticdisease with hepatic fibrosis (especially withcongenital hepatic fibrosis) has attracted con-siderable attention, and it has been suggestedthat they may all be considered to belongto a hepatobiliary fibrocystic continuum. Inaddition there are a variety of cystic neoplasmsand a miscellany of unusual forms.

Gastrointestinal Unit,Charing Cross Hospital,LondonA ForbesI M Murray-LyonCorrespondence to:Dr I M Murray-Lyon,Gastrointestinal Unit, CharingCross Hospital, LondonW6 8RF.

Investigation and diagnosisLarge cystic lesions may be recognised clinically,but in most cases will be found at ultrasoundexamination undertaken because of symptoms,or laboratory screening tests suggestive ofhepato-biliary disease; cysts are not infrequently anincidental finding when scans are done for un-related clinical problems.An accurate differential diagnosis will often be

possible from ultrasonography alone.'2 Mostcommonly, one or more clearly defined echo-lucent spaces are identified within the liversubstance. When these have thin walls andreduce the signal from more distant structures,the most likely diagnosis is of simple cyst andfurther investigation is usually unnecessary. It issuggested, however, that magnetic resonance(MR) imaging may be particularly helpful indoubtful cases.34 Thicker walled single or mul-tiple cysts with a multilayer or laminated marginare likely to be hydatid, and the presence ofdaughter cysts within the lesion is virtuallypathognomonic. A supportive history and posi-tive serology will usually allow confirmation ofthis diagnosis. Aspiration ofpresumptive hydatidcysts is contra-indicated because of the perceivedhigh risk of anaphylaxis if cyst contents spill intothe peritoneum, and there is usually no need toconsider aspiration if hydatid disease is suspec-ted. The hazard has perhaps been over empha-sised, however, and if hydatid disease is unlikelyand cysts have inconclusive sonographic appear-

ances, aspiration for microbiological and cyto-logical examination is warranted. Several reports- (for example,5 and our own unpublished obser-vations) of needle diagnosis of unsuspected hy-datid disease, and even therapy by ultrasoundguided transcutaneous injection of sclerosant,6 7indicate that if the transhepatic route is taken therisk ofmorbidity is low.

Distinction of abscess from cyst is relativelysimple if an abscess has viscous echo densecontents with a thick wall and densely com-pressed surrounding hepatic parenchyma. Per-cutaneous aspiration allows confirmation of thediagnosis, provides material for microbiologicalexamination, and may be of major therapeuticbenefit. Positive blood cultures or amoebicserology may, however, render aspiration super-fluous, given that small single abscesses can beeffectively managed with systemic antimicro-bials alone. Open surgical drainage remainsnecessary for optimal results in some patientswith chronic multiloculated abscesses.

Cystic lesions in continuity with the biliarytree or with vascular structures may be identifiedby ultrasound (the latter particularly so withDoppler probes), but it will usually be necessaryto obtain contrast studies (by ERCP or angio-graphy) for complete diagnosis. In this contextcomputed tomography and MR images of thehepatobiliary region do not appear at present tooffer many advantages over high resolution sono-graphic examination. The interested reader isreferred to one of a number of illustrated reviewsin the radiological literature. i2I48

Liver biopsy tends to be avoided in theinvestigation of cystic disorders, a stance cer-tainly justified when there is suspicion ofhydatiddisease, and probably so when imaging suggestscholedochal cyst, but the recognition of under-lying fibrosis is then less likely, and the clinicianis denied potentially important prognosticinformation.

SIMPLE HEPATIC CYSTSBenign non-parasitic cysts of the liver, onceconsidered rare because they are generally smalland asymptomatic, are more commonly shownby modem imaging (prevalence between 0 19and 2.5%),2 more so in women (female:male ratio1 .5),2 more often in the right lobe, and probablyofcongenital origin. The cysts are lined by biliarycolumnar epithelium, but it is relatively unusualfor the fluid contents to be bile. If the typicalappearances at sonography described above areseen, no further investigation or treatment isrequired. The sensitivity of aspiration cytologyin potentially neoplastic cysts with no definitesolid component is low, but may be improved byassay ofcyst contents for tumour markers such as

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Cystic disease ofthe liverand biliary tract

carcinoembryonic antigen.'0 Other than fromserial scans begun at the time of infection it is notclear that postinfective cysts - longterm sequelaeof unaspirated abscesses - can accurately bedistinguished from congenital benign cysts.' 8

All benign cysts appear subject to a variety ofcomplications. Bleeding into or infection of thecyst contents may be responsible for the onset ofpain or other symptoms; enlargement of cystsalso occurs without obvious cause, and may thenlead to the presence of a painful swelling,"obstructive jaundice'2 or intraperitoneal perfora-tion.'3 Although surgical intervention maybecome necessary, in the absence of peritonitisor severe intraabdominal bleeding, conservativemanagement is probably to be preferred,'4 15with'2 or without'6 percutaneous aspiration.Recurrent symptoms may be prevented by in-ternal drainage ofthe cyst'7 or by the instillation ofsclerosant,'891 the latter course in our view to befollowed only after very careful direct cholangio-graphy has excluded communication with thebiliary tree, if biliary sclerosis is to be avoided.Although there does not seem to be a majorproblem with alcohol injection in analogousmanagement of hydatid cysts7 longterm followup data are sparse. Surgical deroofing of cystswithout drainage ofthe residual cavity is stronglyrecommended20 if surgery is thought indicated.Concern that simple cysts represent a premalig-

nant state has been generated by a series ofreports of neoplasia in apparently preexistingbenign cysts. The tumours are, however, ofdisparate histological type - for example, muco-epidermoid carcinoma,2' multifocal papillarycystadenocarcinoma,22 squamous cell car-cinoma23 - and these may represent coincidentalassociations rather than complications. Theobservation that foci of cystadenoma and cysta-denocarcinoma (the most common malignancydescribed with simple cysts) coexisted withhamartomatous bile ducts24 tends, however, tosupport the view22 that there is a causative link.Although these tumours appear to have a gener-ally poor prognosis, their rarity does not seem tous to warrant indefinite surveillance of asympto-matic patients believed to have simple cystsalone. The claimed stronger association betweennon-parasitic liver cysts and benign livertumours" is, at first sight, more convincing, butprobably reflects rather the association betweenvon Meyenburg complexes, hepatic fibrosis andpolycystic disease (see below).

POLYCYSTIC DISEASESAdult polycystic disease, of autosomal dominantinheritance with high penetrance, may present atany age with renal manifestations, but althoughhepatic involvement iscommon, clinically signifi-cant liver disease is rare (

Forbes, Murray-Lyon

tions of non-cirrhotic portal hypertension(especially bleeding), but may present in adult-hood;37 asymptomatic forms are encountered atall ages. It is most often associated with therecessive form of polycystic kidney disease, butat least two groups32 38 give convincing accountsof an association between congenital hepaticfibrosis and autosomal dominant polycysticdisease. Equally, in a few cases the kidneys areapparently normal.36 Histologically there is aconsiderable increase in fibrous stroma dis-tributed in broad bands throughout the liverwith focal epithelial components and islands ofnormal lobular architure. Such 'pure' congenitalhepatic fibrosis may be disguised by coexistenthistological features of polycystic disease, andoften by the presence of Von Meyenburg com-plexes. These biliary microhamartomata liewithin dense fibrous stroma and surroundepithelially lined irregular spaces which maycontain bile. The complexes expand within oradjacent to the portal tracts and, as they areusually multiple, may be confused with micro-metastases. They may be responsible for portalhypertension without more generalised fibrosis.The Liver Unit described the association of

congenital hepatic fibrosis with intra and evenextra hepatic biliary dilatation' producing apicture identical to Caroli's syndrome exceptthat in that situation there is no fibrosis of thecongenital hepatic fibrosis pattern.A recent