Caroli disease is a congenital, non-obstructive saccular or fusiform dilatation of the large intrahepatic bile ducts that stays in communication with the biliary tree. On imaging, the diagnosis rests on two findings: cystic spaces that connect to the bile ducts on MRCP, and the central dot sign, an enhancing portal vein radicle inside a dilated duct. Caroli syndrome is the same duct malformation plus congenital hepatic fibrosis, and usually renal collecting duct ectasia [1].
This page is a working reference for reporting it: the imaging on each modality, how to separate Caroli disease from polycystic liver disease, biliary hamartomas and obstructive dilatation, where it sits in the Todani classification, the complications to look for, and what the 2022 EASL cystic liver disease guideline recommends for surveillance and treatment [1].
- Key facts for practice and radiology board exams
- Caroli disease versus Caroli syndrome
- Pathogenesis: ductal plate malformation
- Clinical presentation
- Imaging findings by modality
- The central dot sign
- Where Caroli disease fits in the Todani classification
- Differential diagnosis
- Complications to look for
- What EASL 2022 recommends
- How to report suspected Caroli disease
- Frequently asked questions
- References
Key facts for practice and radiology board exams
- Definition: segmental, saccular or fusiform dilatation of the large intrahepatic ducts, communicating with the biliary tree. Todani type V [2].
- Caroli disease versus syndrome: syndrome adds congenital hepatic fibrosis, and hepatic fibrosis is the histological dividing line [1].
- Best test: MRI with MRCP, which shows the ductal communication; post-contrast CT or MRI shows the central dot [1].
- Central dot sign: an enhancing portal radicle engulfed by a dilated duct, described on CT in 1990 [3]. See the central dot sign spotter.
- Extrahepatic ducts: often mildly dilated too, thought to be secondary to cholangitis and stone passage; a dominant extrahepatic cyst means Todani IVA instead [1].
- Complications: intrahepatic stones in about half, cholangitis, abscess, lobar atrophy, and cholangiocarcinoma in about 7 percent [4] [5].
- Surveillance: EASL suggests MRCP every 12 months after diagnosis (weak recommendation); not ERCP [1].
- Treatment: ursodeoxycholic acid, treat cholangitis, resect monolobar disease, transplant for bilobar disease with recurrent cholangitis or fibrosis [1].
Caroli disease versus Caroli syndrome
Jacques Caroli described communicating cavernous ectasia of the intrahepatic ducts in 1958 [6]. Two forms were recognised early. In the pure form the dilatation is segmental and saccular, with stones and recurrent bacterial cholangitis. In the form with congenital hepatic fibrosis the ducts are often less dilated, and portal hypertension dominates [6]. EASL now treats Caroli syndrome as part of the phenotypic spectrum of autosomal recessive polycystic kidney disease (ARPKD) [1].
| Feature | Caroli disease | Caroli syndrome |
|---|---|---|
| Duct malformation | Large intrahepatic ducts | Large intrahepatic ducts plus small interlobular ducts |
| Liver parenchyma | No congenital hepatic fibrosis | Congenital hepatic fibrosis |
| Dominant clinical picture | Cholangitis, stones, abscess | Portal hypertension, splenomegaly, varices, plus cholangitis |
| Kidneys | Renal cystic disease reported in some | Collecting duct ectasia or cysts in most; ARPKD spectrum |
| Inheritance | Mostly sporadic | Autosomal recessive; PKHD1 variants in some |
| Imaging extras | Stones, segmental atrophy | Enlarged left lateral and caudate lobes, splenomegaly, varices, portosystemic shunts |
| Course | Better | Worse: in one cohort all varices, decompensation, cancers and deaths were in the syndrome group |
The distinction matters for prognosis. In a 2026 cohort of 19 patients, all cases of oesophageal varices, hepatic decompensation, cholangiocarcinoma (3) and death (3) occurred in the 12 patients with Caroli syndrome, and median survival was shorter than in Caroli disease (45 against 59 months) [7]. EASL recommends that finding multiple segmental saccular duct dilatations should trigger a search for congenital hepatic fibrosis (strong recommendation, 100 percent consensus); liver stiffness measurement can be used to assess it non-invasively [1].
Pathogenesis: ductal plate malformation
The intrahepatic ducts form from the ductal plate, a sleeve of cells around each portal vein branch that is normally remodelled and partly resorbed during fetal life. Failure of that remodelling leaves persistent embryonic duct structures [1]. The level of the biliary tree affected decides the disease:
- Large intrahepatic ducts affected: Caroli disease.
- Small interlobular ducts affected: congenital hepatic fibrosis, or biliary hamartomas (von Meyenburg complexes).
- Both: Caroli syndrome.
Because the malformed duct wraps around the portal tract instead of sitting beside it, the portal vein and hepatic artery end up bridging or lying inside the dilated lumen. That is the anatomical basis of the central dot sign [3]. Bile stasis in the ectatic segments explains the rest of the disease: stones, bacterial cholangitis, periductal fibrosis and, over time, malignant change [8]. PKHD1, the ARPKD gene, is mutated in some patients with Caroli syndrome, but EASL sees little role for genetic testing in routine practice because the gene is large and variants are hard to interpret [1].
Clinical presentation
The typical story is recurrent cholangitis: fever, right upper quadrant pain and jaundice, often from adolescence or early adulthood. Caroli disease should be considered in chronic cholestasis without an obvious cause [9]. In the French multicentre series of 155 surgical patients, the median age at surgery was 55.7 years, intrahepatic stones were present in 48.4 percent, lobar atrophy in 27.7 percent, bilobar disease in 31.0 percent and Caroli syndrome in 19.4 percent [4]. Patients with Caroli syndrome may instead present with variceal bleeding or splenomegaly, or with renal impairment from the kidney disease [1]. Increasingly, the diagnosis is first suggested by an incidental finding on CT or MRI [10].
Imaging findings by modality
| Modality | Findings | Notes |
|---|---|---|
| Ultrasound | Anechoic tubular or saccular spaces that connect with each other and follow the portal tracts; echogenic stones with shadowing; bridging septa; an echogenic portal radicle inside the cyst with flow on colour Doppler | Usual first test. The Doppler signal in the intraluminal dot helps separate a dilated duct from a simple cyst. |
| CT | Low-attenuation, branching or saccular spaces in continuity with the ducts; tiny strongly enhancing dots inside them (central dot sign); intrahepatic calculi; segmental atrophy | Choi 1990 described the dots on CT and matched them to intraluminal portal veins on ultrasound [3]. |
| MRI and MRCP | T2-bright saccular or fusiform duct dilatations that communicate with the biliary tree; T2-dark intraluminal dots that enhance after gadolinium; stones as filling defects | Modality of choice [1]. MR imaging alone confirmed the diagnosis in 7 of 9 patients in one series [11]. |
| Hepatobiliary-phase MRI | Excreted contrast fills cystic spaces that communicate with the ducts | Useful when MRCP communication is equivocal; non-communicating cysts stay dark. |
| ERCP or PTC | Saccular ectasia of intrahepatic ducts filling with contrast; stones | Reserved for doubtful cases or intervention: risk of cholangitis [11] [1]. |
| Fetal ultrasound and MRI | Multiple dilated intrahepatic ducts in a comb-like arrangement on ultrasound; central dot on fetal MRI; associated enlarged echogenic kidneys | Visible from the late second to early third trimester in one series; all five fetuses had kidney abnormalities [12]. |
Distribution drives management. Diffuse disease involves both lobes. Localised disease is confined to one lobe or segment, often the left, and is the form that can be resected [9]. In Caroli syndrome, the duct changes may be modest while fibrosis produces morphology like cirrhosis, with an enlarged left lateral segment and caudate lobe, and signs of portal hypertension [8]. Levy and colleagues emphasised that fibrosis, duct dilatation, cholangitis, stones and malignancy all overlap on imaging, which is why a single appearance does not prove or exclude the diagnosis [8].
The central dot sign
The central dot sign is a small focus, a few millimetres across, lying in the middle of a dilated intrahepatic duct. It is the portal vein radicle, usually with its hepatic artery branch, completely surrounded by the ectatic duct [3]. On contrast CT and post-gadolinium MRI it enhances like the portal veins elsewhere; on T2-weighted MRI it is a dark dot within bright bile; on Doppler ultrasound it shows flow. A dot seen in cross-section becomes a linear bridge when the same vessel is seen along its length.
It is typical of Caroli disease and is highlighted in both the EASL guideline and a 2026 European imaging review [1] [10]. Two cautions apply. It is not seen in every patient, so its absence does not exclude Caroli disease if the dilated spaces clearly communicate with the ducts. And it should be looked for inside a duct: a vessel running along the wall of a simple or hydatid cyst is not the same sign. For the spotter version, see the central dot sign post.
Where Caroli disease fits in the Todani classification
Todani and colleagues classified congenital bile duct cysts in 1977 [2]. Caroli disease is type V. The main source of confusion is type IVA, which also has intrahepatic cysts.
| Todani type | Location of dilatation | Relevance to Caroli |
|---|---|---|
| I | Extrahepatic duct: cystic (IA), focal (IB) or fusiform (IC) | Commonest choledochal cyst; intrahepatic ducts normal or minimally dilated upstream |
| II | Diverticulum of the extrahepatic duct | Not related |
| III | Choledochocele, intraduodenal distal CBD | Not related |
| IVA | Multiple cysts, intrahepatic and extrahepatic | Main differential: here the extrahepatic cyst is primary and dominant |
| IVB | Multiple extrahepatic cysts only | Not related |
| V | Intrahepatic duct cysts only, single or multiple | Caroli disease |
EASL notes that extrahepatic dilatation is common in Caroli disease and is thought to follow recurrent cholangitis and stone passage [1]. So mild common duct dilatation does not move a patient from type V to IVA. A fusiform or cystic extrahepatic segment that is clearly the dominant abnormality, especially with an abnormal pancreaticobiliary junction, does.
Differential diagnosis
| Condition | Communicates with ducts? | Key discriminator |
|---|---|---|
| Caroli disease or syndrome | Yes | Saccular or fusiform duct ectasia; central dot; stones; segmental distribution |
| Polycystic liver disease (ADPKD or ADPLD) | No | Round cysts of varied size through the parenchyma; no central dot; kidneys often cystic in ADPKD. See ADPKD |
| Biliary hamartomas (von Meyenburg complexes) | No | Many small uniform cysts, usually under 1.5 cm, scattered through both lobes; no duct dilatation |
| Peribiliary cysts | No | Small cysts along both sides of the portal tracts, mimicking dilated ducts; ducts themselves normal |
| Todani IVA choledochal cyst | Yes | Dominant extrahepatic cyst; often pancreaticobiliary maljunction |
| Obstructive biliary dilatation | Yes | Smooth, progressive tapering dilatation upstream of a stricture, stone or mass; no saccules |
| Recurrent pyogenic cholangitis | Yes | Acquired; marked dilatation of central and extrahepatic ducts with abrupt peripheral tapering, pigment stones, left lateral and right posterior segments; no central dot |
| Primary sclerosing cholangitis | Yes | Beaded ducts with alternating strictures and mild dilatation; intra- and extrahepatic |
| Liver abscesses | Sometimes | Enhancing wall, surrounding oedema; can complicate Caroli disease itself |
| Mucinous cystic neoplasm | Rarely | Solitary septated cyst, usually left lobe, middle-aged women; nodularity |
The question that settles most cases is whether the cystic spaces are the ducts themselves. MRCP is the primary tool for this [10] [1]. Polycystic liver disease has negligible malignant potential, while Caroli disease carries a substantial one, so the distinction changes follow-up [10].
Complications to look for
- Intrahepatic stones: filling defects in dependent parts of the saccules; present in 48.4 percent of the French surgical series [4].
- Cholangitis and abscess: duct wall thickening and enhancement, periductal oedema, heterogeneous parenchymal enhancement, gas or debris in cysts [8].
- Segmental or lobar atrophy: from long-standing obstruction and infection; 27.7 percent of surgical patients [4].
- Portal hypertension in Caroli syndrome: splenomegaly, varices, portosystemic shunts [1].
- Cholangiocarcinoma: an enhancing mural nodule, a mass replacing a saccule, or a new stricture. Overall incidence 6.6 percent across 12 studies and 561 patients, range 2.7 to 37.5 percent [5]. See mass-forming cholangiocarcinoma.
- Renal disease in Caroli syndrome: collecting duct ectasia or cysts; renal severity does not track liver severity [1].
Cholangiocarcinoma is the complication that matters most and the one imaging finds worst. In the systematic review, tumours were usually an incidental finding in the resected specimen, one-year survival was 36 percent and recurrence reached 75 percent [5]. In the French series, 8 patients (5.2 percent) had coexistent cholangiocarcinoma, with one-year survival of 33.3 percent [4]. EASL notes there is no disease-specific imaging literature for detecting it; MRI with MRCP is the most accurate test for cholangiocarcinoma in general [1].
What EASL 2022 recommends
| Question | EASL 2022 recommendation | Strength |
|---|---|---|
| How to diagnose | Diagnostic accuracy is highest with MRCP; diagnosis best confirmed in expert centres | Supporting text |
| Disease or syndrome | Multiple segmental saccular duct dilatations should prompt a search for congenital hepatic fibrosis | LoE 4, strong, 100 percent consensus |
| Cancer surveillance | MRCP every 12 months after diagnosis may be offered; ERCP not recommended for screening; CA19-9 performs poorly | LoE 4, weak, 90 percent consensus |
| Medical treatment | Ursodeoxycholic acid 13 to 15 mg/kg per day, even if asymptomatic; antibiotics or ERCP for cholangitis; drain abscesses | Supporting text |
| Resection | First surgical option for symptomatic monolobar disease without fibrosis or portal hypertension | Supporting text |
| Transplant referral | Recurrent cholangitis with bilobar disease, or monolobar disease with fibrosis or portal hypertension, when resection is not possible | LoE 3, strong, 96 percent consensus |
| Kidneys | Monitor renal function in Caroli syndrome; combined liver-kidney transplant may be preferred to sequential | Supporting text |
Surgical outcomes are good when surgery is timely. In the French series, mortality was nil after 111 anatomical liver resections and 10.7 percent after 28 transplants, 5-year overall survival was 88.5 percent, and 90.5 percent of operated patients had complete removal of the abnormal ducts [4]. EASL reports 5-year patient survival of 62 to 100 percent and graft survival of 72 to 100 percent after transplantation [1]. The European Liver Transplant Registry analysis of 110 patients supported transplantation once severe cholangitis or suspected malignancy is present, and early kidney transplantation when ARPKD is associated [13].
How to report suspected Caroli disease
- State the pattern: saccular or fusiform intrahepatic duct dilatation, and whether it is segmental (name the segments or lobe) or diffuse.
- Confirm communication with the biliary tree on MRCP or hepatobiliary-phase images, and say whether a central dot sign is present.
- Describe the extrahepatic duct: normal, mildly dilated, or a dominant extrahepatic cyst that suggests Todani IVA.
- Stones, cholangitis, abscess and segmental atrophy.
- Features of congenital hepatic fibrosis and portal hypertension: liver morphology, spleen size, varices, shunts. These separate disease from syndrome.
- Kidneys: collecting duct ectasia, cysts, size and echogenicity.
- Any mural nodule, enhancing soft tissue, new stricture or mass that could be cholangiocarcinoma, with a recommendation for dedicated evaluation.
- For surgical planning: whether disease is confined to one lobe and resectable.
Frequently asked questions
References
- European Association for the Study of the Liver. EASL Clinical Practice Guidelines on the management of cystic liver diseases. J Hepatol. 2022;77(4):1083-1108. PMID 35728731.
- Todani T, Watanabe Y, Narusue M, Tabuchi K, Okajima K. Congenital bile duct cysts: classification, operative procedures, and review of thirty-seven cases including cancer arising from choledochal cyst. Am J Surg. 1977;134(2):263-269. PMID 889044.
- Choi BI, Yeon KM, Kim SH, Han MC. Caroli disease: central dot sign in CT. Radiology. 1990;174(1):161-163. PMID 2294544.
- Mabrut JY, Kianmanesh R, Nuzzo G, Castaing D, Boudjema K, Letoublon C, et al. Surgical management of congenital intrahepatic bile duct dilatation, Caroli’s disease and syndrome: long-term results of the French Association of Surgery Multicenter Study. Ann Surg. 2013;258(5):713-721. PMID 24121258.
- Fahrner R, Dennler SG, Inderbitzin D. Risk of malignancy in Caroli disease and syndrome: a systematic review. World J Gastroenterol. 2020;26(31):4718-4728. PMID 32884228.
- Miller WJ, Sechtin AG, Campbell WL, Pieters PC. Imaging findings in Caroli’s disease. AJR Am J Roentgenol. 1995;165(2):333-337. PMID 7618550.
- Hanafy AS, Fahmy EK, Naguib R, Abulfaraj M, Omar AF, Naguib H, et al. Clinical outcomes in Caroli disease and Caroli syndrome: a longitudinal observational cohort study. Sci Rep. 2026;16(1):10482. PMID 41888235.
- Levy AD, Rohrmann CA Jr, Murakata LA, Lonergan GJ. Caroli’s disease: radiologic spectrum with pathologic correlation. AJR Am J Roentgenol. 2002;179(4):1053-1057. PMID 12239064.
- Yonem O, Bayraktar Y. Clinical characteristics of Caroli’s disease. World J Gastroenterol. 2007;13(13):1930-1933. PMID 17461492.
- Maino C, Franco PN, Cristoferi L, Cannella R, Mensi E, Donati F, et al. Congenital biliary abnormalities in adults: a practical CT and MRI guide. Eur J Radiol. 2026;205:113241. PMID 42753334.
- Guy F, Cognet F, Dranssart M, Cercueil JP, Conciatori L, Krause D. Caroli’s disease: magnetic resonance imaging features. Eur Radiol. 2002;12(11):2730-2736. PMID 12386765.
- Wei YL, Cao JF, Xing C, Shang N, Ding HK, Zhang LM, et al. Prenatal diagnosis of Caroli’s disease by ultrasound and MRI imaging. Prenat Diagn. 2025;45(4):544-550. PMID 39821604.
- De Kerckhove L, De Meyer M, Verbaandert C, Mourad M, Sokal E, Goffette P, et al. The place of liver transplantation in Caroli’s disease and syndrome. Transpl Int. 2006;19(5):381-388. PMID 16623873.
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