There are many different causes of gastroparesis, although the connection between disorders is not completely apparent in many scenarios.
Diabetes is the most common cause
Abdominal surgery (nissen fundoplication, gastric bypass surgery, gallbladder removal). Surgery may injure the vagus nerve which is responsible for causing the stomach muscles to contract, pushing food out of the stomach. If the vagus nerve is damaged, it becomes paralyzed and is unable to perform this function. In some instances, post-surgical gastroparesis is temporary and the stomach returns to normal after healing.
Mitochodrial diseases- affects at least three major organs and can explain why a person may have a number of seemingly unrelated problems
Rheumatoid or immune deficiency disorders (scleroderma, lupus)
Idiopathic (no known cause)- common suspect in idiopathic cases is viral. If caused by a virus, the GP may reverse itself over time
Eating Disorders (Anorexia Nervosa, Bulimia). Gastroparesis often improves once food intake and eating schedules normalize. This is often due to the stomach muscle weakening because of lack of use.
A blockage caused by ulcers and/or tumors could imitate gastroparesis
Temporary gastroparesis can be caused by certain medications such as narcotics and some IBS drugs including levsin and bentyl, calcium channel blockers and certain antidepressants
Cancer and/or radiation treatment and some types of chemotherapy