Pancreatitis: This condition is highly associated with alcohol abuse. The symptoms of weight loss, abdominal pain, and loose, greasy stools (steatorrhea) are consistent with chronic pancreatitis, where the pancreas is damaged, leading to malabsorption of fats and other nutrients. Elevated labs would include lipase and amylase, although in chronic cases, these may not always be elevated.

Alcoholic Liver Disease: Alcohol abuse can lead to liver damage, manifesting as steatosis (fatty liver), alcoholic hepatitis, or cirrhosis. While liver disease itself might not directly cause greasy stools, malabsorption due to pancreatic insufficiency secondary to liver disease or direct alcohol toxicity could contribute to these symptoms. Elevated labs might include AST, ALT, GGT, and bilirubin.
Malabsorption due to Small Intestine Bacterial Overgrowth (SIBO): Alcohol abuse can lead to altered gut motility and anatomy, predisposing to SIBO. This condition causes malabsorption of nutrients, leading to weight loss and loose, greasy stools. Elevated labs might include hydrogen breath tests.
Gastroesophageal Reflux Disease (GERD) and Peptic Ulcer Disease: Alcohol can irritate the stomach lining, leading to GERD and peptic ulcers, which might cause abdominal pain and weight loss. However, greasy stools are less commonly associated with these conditions.

Pancreatic Cancer: Although less common, pancreatic cancer can present with similar symptoms, especially weight loss and abdominal pain. It's crucial to consider this diagnosis, especially if there's a significant smoking history alongside alcohol abuse. Elevated labs might include CA 19-9.
Infectious Causes (e.g., Giardiasis): In immunocompromised individuals, such as those with chronic alcohol abuse, infectious causes of malabsorption and gastrointestinal symptoms should not be overlooked. Stool tests for ova and parasites would be diagnostic.

Celiac Disease: An autoimmune reaction to gluten, which can be triggered or worsened by alcohol abuse, leading to malabsorption and similar gastrointestinal symptoms. Elevated labs would include tissue transglutaminase antibodies and endomysial antibodies.
Whipple's Disease: A rare, systemic bacterial infection that can cause malabsorption, weight loss, and abdominal pain. Diagnosis is typically made through small intestine biopsy.
Short Bowel Syndrome: Could result from surgical removal of a significant portion of the small intestine, often due to complications of alcohol-related diseases like pancreatitis. This would lead to severe malabsorption.