Simulating bile: Digesting fluid dynamics

Bile is a physiological aqueous solution produced and secreted by the liver through bile ducts. Congenital bile duct anomalies called choledochal cysts (CCs) are a critical risk factor for cholangiocarcinoma, cancer of the bile ducts. Because the cancer symptoms are hard to detect and the causes are poorly understood, the cancer is often detected at a late stage.

Li et al. simulated bile fluid dynamics using MRI scans and computational fluid dynamics methods to investigate the differences between healthy and unhealthy bile.

“CCs present a lifetime risk of 1-15% for developing into gallbladder carcinoma or cholangiocarcinoma,” said author Xiaojian Ni. “Nonetheless, the etiology of CCs remains a topic of ongoing debate. Given the crucial role of bile fluid in digestive processes within the biliary system, analyzing mechanisms from the perspective of bile fluid dynamics is believed to yield additional clinical insights.”

The team reconstructed MRI scans from patients with normal bile ducts, those with suspected biliary dilation, and those with CCs. They then simulated the behavior of the gallbladder emptying and filling and examined the rheological properties of the bile.

“The bile flow velocity in the CCs patients was substantially reduced compared to normal, which implied a higher likelihood of bile accumulation,” said author Yidan Shang. “In healthy biliary systems, Wall Shear Stress (WSS) variations were minimal; however, in CC patients, extreme WSS differences were found — levels 100-250 times higher than in healthy patients.”

Understanding these differences may help uncover the processes contributing to CCs and cancers and pave the way for solutions. The team will continue to investigate the mechanisms that influence tumor growth.

Source: “The impact of choledochal cysts on bile fluid dynamics: A perspective using computational fluid dynamics and surface mapping technique,” by Xueren Li, Xiaojian Ni, Wentao Sun, Jiaying Liu, Yidan Shang, Houbao Liu, and Jiyuan Tu, Physics of Fluids (2024). The article can be accessed at https://doi.org/10.1063/5.0206053 .