Episodic moderate pain in lower left abdomen under and below left ribcage. Ultrasound negative. Appetite healthy. Sometimes seems like muscle. Ideas?

Could be muscle. Often at the edges of the ribcage and illiac/hip bones where the muscle/tendon attach can be strained..Turning too quickly..Such as throwing a ball etc..Can cause a strain/pull on these edges resulting in inflammation and pain..At times lasting for months and much testing done without answer. A good physical exam is all that is needed for these cases..Check with your doc..Again..