Hydrogen Sulfide Actions in the Vasculature.

Hydrogen sulfide (H2 S) is a small, gaseous molecule with poor solubility in water that is generated by multiple pathways in many species including humans. It acts as a signaling molecule in many tissues with both beneficial and pathological effects. This article discusses its many actions in the vascular system and the growing evidence of its role to regulate vascular tone, angiogenesis, endothelial barrier function, redox, and inflammation. Alterations in some disease states are also discussed including potential roles in promoting tumor growth and contributions to the development of metabolic disease. © 2021 American Physiological Society. Compr Physiol 11:1-22, 2021.

Malignant biliary obstruction: From palliation to treatment.

Malignant obstruction of the bile duct from cholangiocarcinoma, pancreatic adenocarcinoma, or other tumors is a common problem which may cause debilitating symptoms and increase the risk of subsequent surgery. The optimal treatment - including the decision whether to treat prior to resection - depends on the type of malignancy, as well as the stage of disease. Preoperative biliary drainage is generally discouraged due to the risk of infectious complications, though some situations may benefit. Patients who require neoadjuvant therapy will require decompression for the prolonged period until attempted surgical cure. For pancreatic cancer patients, self-expanding metallic stents are superior to plastic stents for achieving lasting decompression without stent occlusion. For cholangiocarcinoma patients, treatment with percutaneous methods or nasobiliary drainage may be superior to endoscopic stent placement, with less risk of infectious complications or failure. For patients of either malignancy who have advanced disease with palliative goals only, the choice of stent for endoscopic decompression depends on estimated survival, with plastic stents favored for survival of < 4 mo. New endoscopic techniques may actually extend stent patency and patient survival for these patients by achieving local control of the obstructing tumor. Both photodynamic therapy and radiofrequency ablation may play a role in extending survival of patients with malignant biliary obstruction.