Pancreatic Cancer: This is often considered the most likely diagnosis due to the common presentation of weight loss and jaundice, especially in older adults. The tumor can obstruct the bile duct, leading to jaundice, and cause significant weight loss due to its impact on digestion and metabolism.

Cholangiocarcinoma: A cancer of the bile duct, which can also cause obstructive jaundice and significant weight loss due to its location and impact on bile flow and digestion.
Hepatocellular Carcinoma: The most common type of liver cancer, which can present with jaundice and weight loss, especially in patients with underlying liver disease.
Gallbladder Cancer: Though less common, it can also cause obstructive jaundice and weight loss, particularly if it obstructs the bile duct.

Hepatitis: Acute or chronic hepatitis can cause jaundice, and if severe, can lead to significant weight loss. It's crucial to diagnose and treat hepatitis promptly to prevent liver damage.
Sepsis: Infections such as cholangitis (infection of the bile duct) can cause jaundice and weight loss. Sepsis is a life-threatening condition that requires immediate diagnosis and treatment.
Bile Duct Stricture: A narrowing of the bile ducts, which can be due to various causes including iatrogenic (after medical procedures), can cause obstructive jaundice and weight loss if not properly managed.

Ampullary Cancer: A rare tumor located at the ampulla of Vater, where the bile and pancreatic ducts empty into the small intestine. It can cause obstructive jaundice and weight loss.
Caroli's Disease: A rare congenital disorder of the bile ducts that can cause recurrent cholangitis, leading to jaundice and potentially weight loss if not managed properly.
Primary Sclerosing Cholangitis (PSC): A chronic liver disease that leads to scarring, inflammation, and destruction of the bile ducts, which can cause jaundice and weight loss. It's more common in patients with inflammatory bowel disease.