Multiple biliary hamartomas
Multiple biliary hamartomas (MBH) are a rare cause of multiple benign hepatic lesions. The condition is also known as von Meyenburg complexes, multiple bile duct hamartomas and biliary micro hamartomas. MBH is asymptomatic and usually found incidentally, where it is important to differentiate from other causes of multiple liver lesions, particularly metastases.
The prevalence of MBH is ~3% at autopsy 1, however, prevalence on imaging is <1% as most hamartomas are <5 mm in size and often not detected. MBH is reportedly three times more common in women than men 2.
Biliary hamartomas are composed of small disorganised clusters of dilated cystic bile ducts lined by a single layer of cuboidal cells and surrounded by an abundant fibrocollagenous stroma 1,6-7. Although they may communicate with the biliary tree, they generally do not. They are thought to arise from embryonic bile duct remnants that have failed to involute.
MBH is known to be associated with:
Multiple small round or irregular lesions throughout the liver, with some predilection for subcapsular regions 1. Usually, 5-30 mm in size when detected by imaging (however most lesions are <5 mm when detected by pathologists). Radiographic findings can be non-specific and may be hard to differentiate from metastases and micro-abscesses.
Small hamartomas are usually echogenic if discreetly seen. Often tiny individual hamartomas cannot be resolved and are instead interpreted as diffuse heterogenous liver echotexture. Larger hamartomas (>10 mm) may appear hypoechoic or anechoic and comet tail artefact may be seen 8. Appearances mimic metastases (see ultrasound appearances of liver metastases).
Biliary hamartomas are hypoattenuating and often show no enhancement 6. Occasionally an enhancing nodule or rim may be identified in a small number of lesions.
Only a limited number of the many lesions that are actually present can be seen as grape-like clusters of abnormal vascularity with contrast persisting into the venous phase 9.
Most biliary hamartomas are:
- T1: hypointense compared to liver parenchyma
- depending on TE, may approach that of CSF
T1 C+ (Gd)
- usually no enhancement
- thin peripheral rim enhancement has been described (see below), this may represent compressed normal liver parenchyma 13-14
However, in ~90% of cases an occasional hamartoma can be found containing a mural nodule (fibrocollagenous stroma, see pathology) or rim (see above) that is T1 isodense and T2 intermediate, of which ~90% will enhance. Hamartomas show no diffusion restriction on DWI sequences 2,8,10.
99mTc-DISIDA scan shows delayed uptake and delayed emptying of tracer within larger biliary hamartomas 11.
Treatment and prognosis
Aside from the possible risk of malignant transformation (see associations earlier), MBH is a benign asymptomatic condition with no long-term consequences, and no treatment is required.
History and etymology
It is named after Hans von Meyenburg, pathologist born in Dresden in 1887, who first described the pathology of biliary hamartomas in an article published in 1918 12. Biliary hamartomas to this day remain frequently referred to as "von Meyenburg complexes".
General imaging differential considerations include:
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- 7. Cotran RS, Kumar V, Collins T et-al. Robbins pathologic basis of disease. W.B. Saunders Company. (1999) ISBN:072167335X. Read it at Google Books - Find it at Amazon
- 8. Zheng RQ, Zhang B, Kudo M et-al. Imaging findings of biliary hamartomas. World J. Gastroenterol. 2005;11 (40): 6354-9. World J. Gastroenterol. (link) - Pubmed citation
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- 10. Slone HW, Bennett WF, Bova JG. MR findings of multiple biliary hamartomas. AJR Am J Roentgenol. 1993;161 (3): 581-3. AJR Am J Roentgenol (citation) - Pubmed citation
- 11. Liu CH, Yen RF, Liu KL et-al. Biliary hamartomas with delayed 99mTc-diisopropyl iminodiacetic acid clearance. J. Gastroenterol. 2005;40 (5): 540-4. doi:10.1007/s00535-004-1581-9 - Pubmed citation
- 12. H. von Meyenburg. Über die Zystenleber. Beiträge zur pathologischen Anatomie und zur allgemeinen Pathologie, Jena, 1918, 64: 477-532.
- 13. Lev-toaff AS, Bach AM, Wechsler RJ et-al. The radiologic and pathologic spectrum of biliary hamartomas. AJR Am J Roentgenol. 1995;165 (2): 309-13. AJR Am J Roentgenol (abstract) - Pubmed citation
- 14. Brancatelli G, Federle MP, Vilgrain V et-al. Fibropolycystic liver disease: CT and MR imaging findings. Radiographics. 25 (3): 659-70. doi:10.1148/rg.253045114 - Pubmed citation