Complaints of abdominal pain from patients seeking treatment in hospital emergency rooms nationally rose 31.8 percent from 1999-2008, but about one-half of those patients were discharged without a diagnosis, according to data from the U.S. Centers For Disease Control and Prevention. In fact, the CDC reports that abdominal pain and chest pain continue to be the most common ailments for a visit to the ER for patients aged 15 years and over. Statistics show that about 7 million people aged 18 and older visit the ER each year with complaints of abdominal pain. In Connecticut, emergency room doctors concur that abdominal pain is among the top ailments treated and among the most difficult to diagnosis. “It is like finding a needle in a haystack, in which you think ‘Please let them not be the 50 percent where I can’t tell them what is wrong,’ ” said Dr. Jeff A. Finkelstein, director of Hartford Hospital’s emergency department. The hospital’s ER reported treating 1,674 cases of abdominal pain during the months of April and May. Because the abdominal area contains multiple organs: the stomach, small and large intestines, pancreas, liver and gallbladder, “abdominal pain is very challenging to find the specific cause in a short time frame,” said Finkelstein.