Bile acids are known to pass the blood–brain barrier and are present at low concentrations in the brain. In a previous work, it was shown that subdural hematomas are enriched with bile acids and that the levels in such hematomas are higher than in the peripheral circulation. The mechanism behind this enrichment was never elucidated. Bile acids have a high affinity to albumin, and subdural hematomas contain almost as high albumin levels as the peripheral circulation. A subdural hematoma is encapsulated by fibrin which may allow passage of small molecules like bile acids. We hypothesized that bile acids originating from the circulation may be ‘trapped’ in the albumin in subdural hematomas. In the present work, we measured the conjugated and unconjugated primary bile acids cholic acid and chenodeoxycholic acid in subdural hematomas and in peripheral circulation of 24 patients. In most patients, the levels of both conjugated and free bile acids were higher in the hematomas than in the circulation, but the enrichment of unconjugated bile acids was markedly higher than that of conjugated bile acids. In patients with a known time interval between the primary bleeding and the operation, there was a correlation between this time period and the accumulation of bile acids. This relation was most obvious for unconjugated bile acids. The results are consistent with a continuous flux of bile acids, in particular unconjugated bile acids, across the blood–brain barrier. We discuss the possible physiological importance of bile acid accumulation in subdural hematomas.

胆汁酸已知能通过血脑屏障，并以低浓度存在于大脑中。在以前的工作中，已显示硬膜下血肿富含胆汁酸，并且这种血肿的水平高于周围循环。从未阐明这种富集的机制。胆汁酸对白蛋白有很高的亲和力，而硬膜下血肿所含的白蛋白水平几乎与外周血循环一样高。硬膜下血肿被纤维蛋白包裹，可能允许小分子如胆汁酸通过。我们假设源自循环的胆汁酸可能被“困”在硬脑膜下血肿的白蛋白中。在目前的工作中，我们测量了硬膜下血肿和周围循环中24位患者的缀合和未缀合的伯胆汁酸胆酸和鹅去氧胆酸。在大多数患者中，血肿中的结合胆汁酸和游离胆汁酸水平都高于循环中，但未结合胆汁酸的富集度明显高于结合胆汁酸。在原发性出血和手术之间的时间间隔已知的患者中，该时间段与胆汁酸蓄积之间存在相关性。对于未结合的胆汁酸，这种关系最为明显。结果与胆汁酸，特别是未结合的胆汁酸穿过血脑屏障的连续通量相一致。我们讨论了硬膜下血肿中胆汁酸积累的可能的生理重要性。