Fast decisions on life-and-death cases are the bread and butter of hospital emergency rooms. Nowhere do doctors face greater pressures to overtest and overtreat.

The fear of missing something weighs heavily on every doctor's mind. But the stakes are highest in the ER, and that fear often leads to extra blood tests and imaging scans for what may be harmless chest pains, run-of-the-mill head bumps, and non-threatening stomachaches.

Many ER doctors say the No. 1 reason is fear of malpractice lawsuits. "It has everything to do with it," said Dr. Angela Gardner, president of the American College of Emergency Physicians.

The fast ER pace plays a role, too: It's much quicker to order a test than to ask a patient lots of questions to make sure that test is really needed.

"It takes time to explain pros and cons. Doctors like to check a box that orders a CT scan and go on to the next patient," said Dr. Jeffrey Kline, an emergency physician at Carolinas Medical Center in Charlotte, N.C.

Patients' demands drive overtesting, too. Many think every ache and pain deserves a high-tech test.

"Our society puts more weight on technology than on physical exams," Gardner said. "In other words, why would you believe a doctor who only examines you when you can get an X-ray that can tell something for sure?"

Refusing those demands creates unhappy patients. And concern that unhappy patients will sue remains the elephant in the emergency room.

ER physicians are among the top 10 specialists most likely to be sued for malpractice, according to leading doctor and insurers groups.

The Physicians Insurers Association of America, which represents almost two-thirds of private practice doctors, lists more than 600 lawsuits against ER doctors nationwide between 2006-08. That's about 3 percent of their clients.

Statistics vary by region, and chances of being sued generally are greater for several other specialties, including obstetricians, surgeons and internists.

Still, the risk for a malpractice suit remains high in the ER because of the unique setting.

In a busy emergency room, "when all hell is breaking loose, not a lot of doctors feel they can take the time to sit down with the patient" and build rapport, said Texas family physician Dr. Howard Brody, an outspoken critic of excessive medical care.

The result can be extra costs, and potential harm — including side effects from unneeded drugs and increased chances for future cancer from excessive radiation.

No one tells patients after a CT scan that the test "just imparted three years of radiation to your body as well as significant stress on your kidney, and Medicare just got charged lots of money," Kline said.

Gardner, who works in a Dallas emergency room, said she tries to talk patients out of tests she thinks they don't need, but usually without success.

There are more than 116 million ER visits each year nationwide, national data suggest, and research suggests the number of visits is rising.

The most common reasons adults go to emergency departments are abdominal or chest pain. Both can mean something harmless, or deadly.

To determine which it is, ER doctors turn to X-rays, CT scans and other imaging tests. In 2006, these were done for almost half of all emergency visits; blood tests were ordered for more than a third of ER visits; medicine, including antibiotics, was given to 75 percent of patients.

One of doctors' biggest concerns with belly pain is appendicitis, and CT scans can confirm it. But the scans often are done in patients without classic symptoms.

Patients with suspicious abdominal pain used to go straight into the operating room, where surgeons opened them up to find appendicitis — or rule it out. Dr. Angela Mills of the University of Pennsylvania said CT scans have reduced unnecessary surgeries, "but I think the pendulum has gone to the other side." The trade-off is fewer surgeries and hospitalizations versus a test that costs several hundred dollars but which involves lots of radiation.

Mills is studying a blood test that would detect a marker for appendix inflammation, which might avoid the need for CT scans, and would be safer and cheaper, too.