1 Red blood cells (RBCs) are also called erythrocytes. They make up almost half of blood. Red blood cells are filled with hemoglobin. That's a protein that picks up oxygen in the lungs and brings it to cells all around the body.  White blood cells (WBCs) are also called leukocytes.
Pain originating in the stomach or esophagus is often felt in the upper abdomen and can be due to heartburn, gastroesophageal reflux disease (GERD), or hiatal hernia (weakening in the diaphragm that allows the stomach to protrude into the chest). You may also have gastritis (inflammation of the stomach lining) or ulcers.
Re: Can IBS cause upper stomach pain. I've had IBS-D for the last 24 years and I'm 29 years old. Upper stomach pain, right under the ribcage, is exactly where I have my pain. I have been tested for every other stomach condition under the sun, from ulcers to crohn's, and everything has always turned out negative.