PBC are rare cystic hepatic lesions in typical location with the potential to mimic hepatic malignancy or other hepatobiliary conditions [1, 15]. Nevertheless, they exhibit characteristic imaging features that, when recognized, can substantially aid in accurate differentiation. This study provides a systematic MRI-based assessment of peribiliary cysts in a consecutive liver MRI cohort and highlights two clinically relevant aspects that have not been well quantified in prior literature: longitudinal imaging evolution and real-world reporting accuracy. PBC were uncommon, identified in 2.0% of patients, but showed a characteristic imaging pattern with almost exclusively intrahepatic location, frequent bilobar involvement, and predominant central peribiliary distribution. More than half of patients with follow-up MRI demonstrated interval progression in cyst size, number, or distribution, suggesting that PBC may slowly evolve over time. Importantly, PBC were correctly identified in fewer than one-third of original radiology reports, underscoring that this entity remains underrecognized in routine practice despite its typical imaging appearance. Peribiliary cysts should be considered when multiple small fluid-signal cystic lesions are arranged along the central portal tracts or bile ducts, particularly in patients with cirrhosis, portal hypertension, or chronic liver disease. Features supporting the diagnosis include a linear or clustered periductal distribution (“string of pearls”), absence of enhancement or solid components, absence of biliary communication on MRCP or hepatobiliary phase imaging, and preservation of adjacent bile duct caliber unless secondary compression is present.

In our cohort, PBC were identified in 35 of 1708 patients undergoing liver MRI for various clinical indications between 2021 and 2022, a prevalence substantially lower than previously reported. Bazerbachi et al. [1], for example, reported a prevalence of approximately 9% in patients with cirrhosis based on a systematic review integrating imaging and histopathologic data. This discrepancy is likely attributable to differences in study populations: while our cohort included both cirrhotic and non-cirrhotic patients, the analysis by Bazerbachi et al. focused predominantly on cirrhotic livers, in which PBC are more common. Additionally, many PBC are microscopic and detectable only at histopathology. Earlier autopsy studies, for instance, identified peribiliary cysts in up to 20.2% of cases [16]. The inclusion of autopsy data in the systematic review therefore plausibly contributed to the higher reported prevalence.

The imaging phenotype observed in our cohort was highly consistent with the known anatomical origin of PBC from extramural peribiliary glands. Nearly all cases were intrahepatic (97.1%), with only one patient demonstrating combined intra- and extrahepatic involvement and no cases limited solely to the extrahepatic ducts. This distribution aligns with prior reports indicating that 85–90% of PBC arise intrahepatically, whereas mixed or exclusively extrahepatic presentations are uncommon [1]. Lobar involvement most frequently affected both hepatic lobes (80%), while 20% of cases were confined to the left lobe; no right-lobe–only cases were observed. This pattern is consistent with previous descriptions of central peribiliary predominance and frequent bilobar distribution, likely reflecting the anatomic distribution of peribiliary glands. As the peribiliary glands, from which these peribiliary cysts are thought to arise, are primarily located in the lamina propria of the major bile duct and peribiliary cysts are therefore found in association with larger portal tracts [17]. Furthermore, very tiny cysts in the far peripheral regions may be too small to be detectable on imaging. The median cyst diameter in our cohort was 9 mm (range, 2–34 mm), consistent with previously reported size ranges, although some studies have described larger maximum dimensions [1, 11, 14, 16]. Biliary duct dilatation was present in roughly one-quarter of patients - slightly higher than in earlier reports where this finding appeared less frequent [1]. This discrepancy may relate to differences in disease severity across cohorts or to variations in imaging techniques and diagnostic thresholds. Over a median follow-up period of 40 months, cyst progression was observed in 59.3% of patients—substantially higher than the ~37.5% reported by Bazerbachi et al. [1], whose cohort was monitored for shorter intervals. This discrepancy suggests that longer observation increases the likelihood of detecting interval growth or extension. Variability in cohort composition, imaging protocols, and definitions of progression may also account for differences in reported rates. Collectively, these findings reinforce the diffuse nature of PBC, characterized by central predominance and frequent bilobar involvement, and underscore the importance of extended imaging follow-up to better define their natural history and potential implications, particularly regarding biliary obstruction.

The strong association between PBC and liver cirrhosis supports the hypothesis that PBC may reflect structural alterations arising from chronic liver injury, consistent with prior reports linking biliary cystic changes to portal hypertension or advanced fibrosis [1, 4]. In multivariable logistic regression adjusting for age, sex, and intrahepatic malignancy, cirrhosis emerged as the strongest independent predictor of PBC (aOR 3.62, p < 0.001), confirming that this association is not explained by confounding with other clinical variables. Older age remained independently associated with PBC after adjustment (aOR 1.04 per year, p = 0.011), whereas the apparent association with male sex attenuated to a non-significant trend (aOR 0.48, p = 0.075), suggesting that the observed sex difference is at least partly mediated by the age and cirrhosis distribution within our cohort. The male predominance and older age observed in patients with PBC may reflect the demographic characteristics of cirrhosis or other underlying hepatic disorders; however, additional studies are needed to determine whether sex constitutes an independent risk factor. A systematic review [1] similarly reported that 80% of individuals with PBC were male, with a mean age of 63 years, demonstrating strong concordance with our findings.

In addition to cirrhosis as a structural marker of advanced chronic liver disease, specific hepatic insults may directly contribute to PBC formation. Matsubara et al. [18] reported PBC in 35.5% of patients with alcohol-related hepatic or pancreatic disease and in 14% of chronic heavy drinkers at autopsy, with prevalence increasing alongside the severity of alcohol-induced fibrosis. These findings support a mechanism in which alcohol-related injury to peribiliary glands causes inflammation, ductal obstruction, and cystic dilatation, consistent with PBC representing retention cysts of damaged glands. While our cohort was not specifically designed to assess alcohol-related liver disease as a distinct etiologic category, alcohol related liver disease was present in 17.1% of patients with PBC. The heterogeneous etiologies of chronic liver disease in our cohort may explain why no single cause differed significantly between groups, suggesting that PBC formation is more strongly associated with cumulative liver injury than with a specific etiology, although alcohol may be a particularly potent contributor through direct glandular injury.

Although symptoms in patients with PBC were not consistently attributable to the cysts themselves, their identification on MRI remains clinically relevant to avoid misdiagnosis and unnecessary treatment. In our cohort, PBC were more frequently observed in patients with cirrhosis, consistent with their known association with chronic hepatic dysfunction. Recognizing this relationship is clinically relevant, as awareness of PBC in the setting of advanced liver disease may help avoid misinterpretation of these cysts as other biliary pathologies, including malignancy.

Although intrahepatic malignancies appeared more frequently in patients with PBC, this association disappeared after adjustment for cirrhosis (aOR 0.80, p = 0.645). Prior case reports [4, 19] have described the coexistence of PBC with hepatocellular carcinoma or cholangiocarcinoma, but these observations likely reflect the shared background of chronic liver disease rather than a direct relationship between PBC and malignancy. Given that cirrhosis and chronic liver disease are associated with development both PBC and primary hepatic cancers, the observed overlap may be confounded by the high prevalence of advanced chronic liver disease in these patient populations rather than indicating a causal link.

In those patients where follow-up imaging was available, approximately 60% demonstrated a progression of the number and extent of peribiliary cysts indicating a dynamic, potentially progressive process. This finding aligns with prior work, including Bazerbachi et al. [1], who reported progression in 37.5% of patients over a shorter follow-up interval, and Koth et al. [15], who similarly noted gradual cyst enlargement, often in the setting of chronic liver disease. These data support the concept that peribiliary cysts may show slow structural evolution, particularly when underlying hepatic pathology is present. Such longitudinal changes underscore the value of continued imaging surveillance to monitor cyst morphology over time. The clinical significance of this progression, however, remains uncertain, and it is unclear whether enlargement of PBC reflects worsening of the underlying chronic liver disease or represents an independent imaging phenomenon.

Review of the original radiology reports demonstrated that PBC were either not mentioned or were misclassified in 72% of cases. This high rate of underrecognition represents one of the most clinically relevant findings of our study and suggests that, despite their characteristic imaging appearance, PBC remain insufficiently recognized in routine radiological practice.is one of the clinically most relevant findings of our study and suggests that, despite their characteristic imaging appearance, PBC remain insufficiently familiar in routine radiological practice. Although PBC are typically benign and often incidental, accurate recognition is important because their clustered peribiliary distribution can mimic biliary ductal dilatation, bile duct strictures, Caroli disease, or even infiltrative hilar pathology. Misinterpretation may therefore lead to diagnostic uncertainty, additional imaging, unnecessary follow-up, or referral for further hepatobiliary evaluation. Conversely, when the typical imaging constellation is recognized, namely multiple small fluid-signal cysts arranged along central portal tracts or bile ducts (“string of pearls”), absence of communication with the biliary tree on MRCP or hepatobiliary phase imaging, and lack of suspicious enhancement, PBC can usually be confidently diagnosed as a benign peribiliary entity (Fig. 5 provides a practical MRI checklist). Greater awareness of these key features may therefore improve reporting accuracy, reduce unnecessary concern for biliary or malignant mimickers, and support more appropriate patient management.

Several limitations should be acknowledged when interpreting the findings of this study. First, this was a retrospective single-center study of patients undergoing clinically indicated liver MRI at a tertial referral center, which introduces selection bias and limits generalizability to broader populations. Accordingly, the observed prevalence of imaging-visible PBC should not be interpreted as a population-based prevalence estimate. The cohort likely overrepresents patients with chronic liver disease, oncologic indications, or hepatobiliary abnormalities, while microscopic PBC not visible on MRI would not be captured. Second, although this represents a comparatively large MRI-based PBC cohort, the absolute number of PBC cases was small, limiting the power for subgroup analyses. Third, MRI protocols reflected routine clinical practice and varied according to indication, field strength, contrast agent, and availability of MRCP, which may have influenced detection sensitivity. Fourth, histopathologic confirmation was not available, however, diagnosis was based on characteristic MRI features and consensus review by experienced abdominal radiologists. Finally, imaging follow-up was not available in all patients, which may have influenced the assessment of longitudinal cyst evolution, and the clinical implications of imaging progression remain uncertain. Despite these constraints, this study represents the first systematic MRI-based evaluation of peribiliary cysts and provides meaningful insights into the imaging and clinical characteristics of PBC and contributes to the limited body of literature on this rare entity. Future larger-scale studies will be important to further clarify the associations between peribiliary cysts, chronic liver disease severity, and potential clinical outcomes.