There are numerous reasons for left-side pain beneath the ribs; heartburn or acid reflux, spleen irritation, gas, costochondritis, a broken rib, pneumothorax and stomach ulcers can all cause this type of pain. Irritable bowel syndrome, or IBS, can also be to blame. More rarely, diverticulitis, infection of the intestines, pancreatitis, pericarditis and abdominal aortic aneurysm cause left-side pain below the ribs, according to MedGuidance.
One of the most common causes of left-side pain under the ribs is heartburn or acid reflux disease triggered by eating foods that cause indigestion. MedGuidance states that this pain is sometimes quite sharp and may be accompanied by a feeling of bloating.
Spleen irritation is also quite common and can cause this pain. When caused by spleen irritation or rupture, it may be accompanied by pain in the left shoulder as well.
Trapped gas can cause this type of pain. Per MedGuidance, when gas becomes trapped in the colon, it can be caused by splenic flexure syndrome.
Although not as common, infection of the cartilage that bonds the breastbone to the ribs, which is known as costochondritis, can cause pain in the left side under the ribs. The condition is generally caused by an impact to the rib cage or a viral infection. It can be quite serious and requires medical attention, according to MedGuidance.