Infected von Meyenburg complex causing recurrent gram‑negative septicaemia: the critical diagnostic role of FDG‑PET/CT in a patient with hidradenitis suppurativa

Abstract

Background

von Meyenburg complex (VMC) is a rare ductal plate malformation, typically presenting as asymptomatic benign intrahepatic biliary microhamartomas. However, when secondarily infected, VMC can become the source of cryptic recurrent septicaemia, posing a substantial diagnostic challenge, particularly in patients with a known history of chronic source of comorbid infection.

Case presentation

A 73-year-old man with long-standing hidradenitis suppurativa presented with over ten episodes of recurrent gram-negative septicaemia. Extensive conventional imaging, including a ⁶⁷Gallium scintigraphy in another hospital, failed to identify an infectious source. Due to persistent diagnostic uncertainty, ¹⁸F-FDG PET/CT was performed. The scan revealed an enlarged liver with heterogeneously increased ¹⁸F-FDG uptake exhibiting an “inverted pyramidal” metabolic configuration: a wide base of activity along the subcapsular dome of superior hepatic segments converged centripetally towards the porta hepatis, thereby casting a tree-like three-dimensional anatomy of the biliary radicles. CT findings were non-specific, showing vaguely scattered mixed densities, greatly outnumbered by the hypermetabolic foci. Constellation of these findings suggests a non-dilated ductal infectious process, leading to the presumptive diagnosis of infected VMC with micro-abscesses. Subsequent MRI/MRCP confirmed numerous tiny T2‑weighted bright signals of varying sizes and intensities in agreement with the “starry sky” pattern of biliary hamartomas. Targeted levofloxacin therapy based on susceptibility testing resulted in resolution of fever and septic parameters. A follow-up ¹⁸F-FDG PET/CT scan three weeks after treatment demonstrated complete metabolic quiescence and resolution of previously documented intrahepatic hypermetabolic foci.

Conclusion

¹⁸F-FDG PET/CT has proven value in investigation for fever of unknown origin. This case illustrates the value of this imaging not only in precise localization of the infectious source but also provides a suggestive metabolic pattern leading to the diagnosis of a rare congenital biliary condition, VMC, as a hidden source of infection otherwise masked by other comorbid infectious foci. Revealing the true source of loculated infection and its mechanism of spread leads to appropriate antibiotic therapy and treatment monitoring.

Background

Recurrent septicaemia poses a persistent diagnostic challenge in patients with a well-recognized, long-standing infectious comorbidity, such as hidradenitis suppurativa. There is a substantial risk that repeated fever episodes will be erroneously attributed to the superficial disease. This clinical default can delay the search for the real source of infection, leading to inappropriate or suboptimal antibiotic therapy and recurrent episodes of sepsis.

In such a diagnostic dilemma, conventional imaging modalities are often insufficient to reliably differentiate sterile lesions from active infectious foci, especially when the lesions are small (< 5 mm) or lack specific morphological features of infection such as rim enhancement or abscess formation. It is known that functional imaging with ¹⁸F-FDG PET/CT is useful for investigation of fever of unknown origin (Hess et al. 2024, Abikhzer et al. 2025). It is not just valuable in revealing occult sites of infection; it is also useful in suggesting diagnostic hints to otherwise unsuspected morphological disorders by means of its metabolic pattern of involvement.

We present here a rare case with specific ¹⁸F-FDG PET/CT findings, providing strong supportive evidence for the diagnosis of infected VMCs in a patient with hidradenitis suppurativa presumptively treated as the cause of recurrent septicaemia, enabling prompt targeted antibiotic therapy and treatment monitoring.

Case presentation

Case description

A 73‑year‑old man with a background of hidradenitis suppurativa on long‑term doxycycline was admitted over ten times to his local hospital with recurrent fever, chills, and rigors. During earlier admissions, his symptoms were attributed to infected hidradenitis lesions or perianal/sebaceous ulcers, and he was discharged after short‑course antibiotics. Blood cultures intermittently grew Escherichia coli; however, in several episodes no definite source was identified, and his febrile events were labelled as septicaemia of unknown origin.

Patient’s most recent admission to his referring hospital was more refractory. Clinical notes remarked a mix of visible scarring and cutaneous sinuses, and suspected to have deep seated micro-abscesses in view of his septic symptoms. Blood culture was again positive for E. coli, which was now resistant to amoxicillin‑clavulanate and cotrimoxazole—agents that had been effective previously. Laboratory investigations showed persistent leukocytosis (15 × 10⁹/L), elevated C‑reactive protein (28 mg/L), and a deranged liver profile (alkaline phosphatase 234 U/L, alanine aminotransferase 82 U/L, aspartate aminotransferase 90 U/L). Gamma-glutamyl transferase, total bilirubin, CA19-9 and CEA were normal. A rectal swab was negative for all suspected pathogens.

Imaging investigations

⁶⁷Gallium whole‑body planar imaging performed at the referring hospital revealed no focal tracer loculation to suggest an active infective or inflammatory focus on 24‑ and 48‑hour images (Fig. 1). Because of the negative ⁶⁷Gallium scan and ongoing diagnostic uncertainty, the patient was referred for ¹⁸F‑FDG PET/CT.

Fig. 1.

Anterior and posterior planar ⁶⁷Gallium scintigraphy showed minimally heterogeneous activity in liver but interpreted as within physiologic distribution by outside hospital

¹⁸F‑FDG PET/CT

The patient fasted for 6 h with blood glucose concentration 5.8 mmol/l. 60 min after ¹⁸F-FDG (440 MBq) administration, limited whole body CT (non-contrast) transmission began and followed by PET emission imaging (2 min/bed), spanning a region from base of skull to upper thigh (Biograph Vision, Siemens). On ¹⁸F-FDG PET/CT, the liver was enlarged (craniocaudal dimension ~ 19.5 cm on CT) with a smooth contour and uniform parenchymal density, in which a few low‑attenuation cystic lesions were scattered in both lobes without a specific distribution. On PET, there was patchy, heterogeneously increased ¹⁸F‑FDG uptake throughout the cranial half of the liver. The metabolic abnormality displayed a distinctive “inverted pyramidal” configuration on orthogonal projections: a broad base along the subcapsular dome of the superior segments converging towards the peri‑hilar/portal region (Fig. 2A). This centripetal pattern mirrored the dichotomous branching and coalescence of intrahepatic biliary radicles. Some inner margins exhibited an infiltrative, prong‑like appearance suggestive of ductal confluences, most prominent in the anteromedial dome of segment IVa and the lateral aspect of segments VIII/IVa, best appreciated on sagittal images. No other abnormal FDG‑avid focus was identified in the gallbladder, extrahepatic bile ducts, or elsewhere in the body.

Fig. 2.

(A) Pretreatment PET/CT fusion images showed “inverted pyramidal” metabolic pattern on coronal, sagittal projections and MIP images. Increased ¹⁸F-FDG activities were detected along the subcapsular superior liver segments converging centripetally towards the porta hepatis. No other suspicious site of abnormal tracer loculations. (B) Post-treatment PET/CT after 3 weeks of antibiotics showed complete metabolic quiescence in liver

Taken together with the clinical picture, these findings suggested a loculated infectious process affecting the small intrahepatic bile ducts. Given the absence of dilated peripheral ducts, a diagnosis of multiple infected biliary hamartomas (VMC) complicated by micro‑abscesses was proposed.

MRI and MRCP

Subsequent liver MRI with MRCP confirmed numerous T2‑weighted hyperintense cystic lesions of varying sizes scattered throughout both hepatic lobes. Heterogeneous contrast enhancement in scattered areas suggested associated vascular shunts (Fig. 3). These features were consistent with diffuse biliary hamartomas.

Fig. 3.

Comparing with MR T1-weighted image (A), MR T2-weigted image (B) showed numerous bright signal foci of variable size and intensities, suggestive of “starry sky” pattern with AV shunting (C, red arrow) and mild dilatation of portal intrahepatic ducts

Antibiotic management and follow‑up

Susceptibility testing revealed that the patient’s E. coli isolate was sensitive to levofloxacin. He was treated with intravenous levofloxacin 750 mg daily until clinical stabilization and resolution of septic symptoms, then transitioned to oral levofloxacin 750 mg daily for two weeks after discharge. A follow‑up ¹⁸F‑FDG PET/CT scan performed three weeks after completion of therapy demonstrated complete metabolic resolution of all previously documented intrahepatic hypermetabolic foci, with disappearance of the characteristic “inverted pyramidal” distribution (Fig. 2B).

Based on the combination of PET/CT pattern, MRI/MRCP morphology, microbiology, and therapeutic response, the diagnosis of multiple infected biliary hamartomas (VMC) was strongly supported.

Discussion

The intrahepatic bile ducts develop from the ductal plate, a cylindrical envelope of bipotent hepatic progenitor cells that ensheathes the branching portal vein mesenchyme during embryogenesis. Through a tightly regulated process of selective apoptosis and tubulogenesis, the ductal plate is remodeled into a mature, communicating network of bile ducts. Arrest or disruption of this remodeling at any stage results in persistence of embryonic ductal structures, termed ductal plate malformation (DPM) (Davidoff et al. 2006, Gupta et al. 2016).

Depending on the level at which ductal plate involution fails, DPM gives rise to a spectrum of cystic liver diseases. When the smallest peripheral interlobular ductules fail to involute, the result is von Meyenburg complexes—biliary microhamartomas composed of clusters of irregular, non‑communicating ductules embedded in fibrous stroma (Davidoff et al. 2006, Tarchi et al. 2020). Failure at the level of medium‑sized intrahepatic ducts leads to polycystic liver disease (Lalosevic et al. 2005, Jain et al. 2010), characterized by multiple larger thin‑walled cysts, often in association with autosomal dominant polycystic kidney disease. Arrest at the level of the larger segmental or lobar ducts results in Caroli disease, with saccular dilatation of the major intrahepatic bile ducts(Rocken et al. 2000, Pech et al. 2016). These entities share a common embryological origin and represent points along a continuous DPM spectrum (Fig. 4).

Fig. 4.

Schematic drawing for illustrating different levels of ductal plate involution failure, comparing the smallest von Meyenburg complex (VMC) micro-cysts with Polycystic Liver disease (PCLD) and Caroli disease. Infected VMC spread passes along biliary tree-like, non-dilated bile ducts downstream to the porta hepatis

Although initially purely cystic, DPM‑related lesions often progress to fibrocystic liver disease (CFLD) when chronic inflammation, recurrent infection, or biliary stasis triggers periportal fibroblast activation and collagen deposition. This progressive fibrosis may transform isolated cystic anomalies into a combined fibrocystic phenotype, which in its full expression includes congenital hepatic fibrosis and Caroli syndrome (Jain et al. 2010, Rocken et al. 2000, Pech et al. 2016). Even von Meyenburg complexes, traditionally regarded as benign and clinically silent, can contribute to this process if complicated by repeated infection and micro‑abscess formation, as local inflammatory cascades are capable of initiating fibrogenesis (Hashimoto et al. 2011).

In the present case, the patient’s recurrent E. coli septicaemia posed a persistent diagnostic challenge. Different from case reports on multicystic biliary hamartoma (MCBH) that have focal, mass-forming nodules ranging from 2 to 10 cm (Lian et al. 2022, Wang et al. 2022), VMCs are typically diffuse with tiny hamartoma cysts < 5 mm (Davidoff et al. 2006, Shiraki et al. 2006). In particular, the tiny cysts of diffuse VMC are notoriously difficult to appreciate on unenhanced CT and remain subtle even with intravenous contrast, such that they are often overlooked on routine cross‑sectional imaging (Guo et al. 2019, Wohlgemuth et al. 1998, Jeon and Yoon 2006). T2‑weighted MRI and MRCP offer the greatest sensitivity for detecting these cystic spaces (Boraschi et al. 2021), and in this patient MRCP indeed demonstrated the characteristic innumerable hyperintense “starry sky” lesions throughout both hepatic lobes, establishing the anatomical diagnosis of diffuse biliary hamartomas (Gong et al. 2012, Lancho Munoz et al. 2026, Neubert et al. 2020, Priadko et al. 2022, Toro-Calle et al. 2022, Zeng and Wan 2021). Nevertheless, MRI could not determine whether these cysts were the source of the patient’s fevers; the signal characteristics of VMC on T2‑weighted sequences cannot with certainty distinguish sterile hamartomas from those that have become infected because the small size of the these lesions are limitations to delineate blurry, indistinct, irregular margins or transient peripheral enhancements that are imaging features of infection typically seen in macroscopic infected cysts (Sinakos et al. 2011). Another MR-related finding is an enhanced “mural nodule” sign (Ryu et al. 2010), which is again not specific or sensitive enough for diagnosing infected VMC. In fact, the diagnostic challenge is so formidable that the condition can be interpreted as “image-negative ascending cholangitis,” where a patient presents with severe sepsis and bacteremia. Compounding this, the patient had a well‑recognized alternative infective source in his hidradenitis suppurativa, and multiple prior clinicians had defaulted to this explanation. The negative ⁶⁷Gallium scan also lent false reassurance that no hepatic infection was present.

VMC lesions are often defined by their microscopic to very tiny dead spaces (hamartomas) by their lack of bile duct communication, and yet they could cause both intrahepatic ductal spread and/or severe, recurrent bloodstream septicemia. Although there is no proven mechanism underlying which the communication is made, there are a few case reports with tissue culture and microbiological support that the infectious source of the bile ducts is from the cystic hamartomas (Hashimoto et al. 2011, Neubert et al. 2020) and not ascending cholangitis from bowel. The organisms reported include Klebsiella pneumonia, Klebsiella oxytoca, and E. coli (Neubert et al. 2020). Bile stasis within these cystic dead spaces are ideal sanctuary beds for bacterial colonization, multiplication, micro-abscess formation and subsequent disruption and dissemination (Wajtryt et al. 2017).

¹⁸F-FDG PET/CT proved transformative in this setting (Shono et al. 2022). By mapping glucose hypermetabolism, the scan revealed active inflammatory loculations within the liver while simultaneously excluding any other hypermetabolic focus in the whole body. The distribution of abnormal uptake was particularly instructive: patchy and heterogeneous ¹⁸F-FDG-avid foci coalesced into an “inverted pyramidal” configuration that extended from the subcapsular periphery of the superior segments and converged centripetally towards the porta hepatis. This pattern faithfully reproduced the three‑dimensional anatomy of the converging biliary radicles, from the smallest peripheral ductules to the larger segmental branches, thereby providing a metabolic “road map” of the infected biliary tree. The appearance was specific for a non‑dilated ductal infectious process, leading directly to the diagnosis of infected VMC with micro‑abscesses. Once susceptibility testing identified levofloxacin as an effective agent, targeted therapy was administered. A follow‑up ¹⁸F-FDG PET/CT scan performed three weeks later demonstrated complete clearance of all hepatic hypermetabolism, in parallel with definitive resolution of the patient’s clinical features of pyrexia and septicaemia. The concordance between metabolic imaging and clinical response provided strong supportive evidence that the infected VMC was the causative source and confirmed the efficacy of the directed antibiotic regimen.

Conclusion

This case report illustrates the value of ¹⁸F-FDG PET/CT not only in precisely localizing the infectious source but also in revealing a distinctive metabolic pattern leading to the diagnosis of a rare congenital biliary condition, VMC, otherwise masked by a comorbid long-standing infection (hidradenitis suppurativa) with non-specific structural imaging findings. Although a clinical paradox exists when VMCs are histologically non-communicating microbiliary dead spaces, their functional behavior in causing a biliary-tree pattern of intrahepatic spread (non-dilated cholangitis) can be a rather unique metabolic pattern on ¹⁸F-FDG PET/CT. Revealing the true source of loculated infection and its mechanism of spread may guide the appropriate antibiotic therapy and treatment monitoring.

Author contributions

CLH participated in the conceptualization, data interpretation, data acquisition, and writing of the original draft. SC participated in the data acquisition, writing and revision of the manuscript. YHW, KKW, YY, WCL, SKC participated in the revision of the manuscript. All authors read and approved the final manuscript.

Funding

None.

Data availability

The datasets generated during and/or analyzed during the current study are not publicly available, but are available from the corresponding author on reasonable request.

Declarations

Ethics approval and consent to participate

The study was approved by the institutional review board of our institution, and the requirement for written consent was waived by the institutional review board. All procedures performed in studies involving human participants were in accordance with the Helsinki Declaration as revised in 2024 and its later amendments.

Consent for publication

Written informed consent for publication was not required as the patient’s clinical data and images were fully anonymized, and no personally identifiable information is included in this article.

Competing interests

Chi Lai Ho, Sirong Chen, Yuet Hung Wong, Kwan Kit Wu, Yu Yip, Wai Chi Lin, Shing Kee Cheung declare that they have no conflict of interest.