Thanks for the query to H.C.M. Forum.
If I were your treating doctor for this case of swelling in the ( under ) left rib cage
,I would come up with these possibilities , these includes.
1 May be Hiatus hernia
, diagnosis can be confirmed by upper G I endoscopy . As you don't mention any pain in the region so may be swelling or lump in the stomach ,so upper endoscopy
will find out the exact nature of disease.
2 May be enlarged mass of spleen
, diagnosis can be confirmed by ultrasound
of spleen .
So in my opinion consult a physician and get his opinion as physical examination is very important in this case.
Good luck. Dr. HET