What could cause intense upper left abdomen pain?

Lots of things... Anatomically, the left upper quadrant (luq) of abdomen includes: spleen, pancreatic tail, stomach, descending duodenum, splenic flexure of the colon, associated vessels. Don't forget the diaphragm, heart, and lower chest are pretty close by. The abdominal musculature, ribs, and skin can all contribute as well to localizing luq pain. An exam is appropriate for clarity of diagnosis and treatment.

Related Questions

I started to have lower and upper left abdomen pain yesterday. The pain is constant and gets worse when lightly touched or when I move. Causes?

Can't tell here. Could be lots of things, ranging from musculoskeletal problems, constipation, to serious internal issues, including but not limited to: ulcer (with or without complication), gyn issues, kidney stone or infection, bowel issues, infections, etc. See your doc.
Need exam. Depending upon where you are in your cycle and if it came on all of a sudden, you may have a cyst on your ovary or a ruptured cyst. There are also some more unusual things. An exam would be helpful.

Upper left abdomen pain. What is this pain likely to be from?

Number of things. This could be something as minor as gas to as serious as an ulcer or spleen injury. In that general area, you have your stomach, spleen, parts of large and small intestine, diaphragm, and a portion of your pancreas. With all of these structures, a physical exam is recommended to be sure to not miss serious issues.