President Carter described by aides as suffering from "an aggravated hemorrhoid problem" and facing possible surgery, canceled all of his appointments yesterday and spent most of the day in bed in the White House.

White House press secretary Jody Powell said last night that surgery for Carter "is possible but not likely" and that a decision on that would probably be made today. He indicated that if surgery is considered necessary, it would probably occur during the Christmas holidays, which the president had planned to spend at his home in Plains, Ga., and at the presidential retreat at Camp David, Md.

Powell said Carter first began experiencing serious pain from the problem on Tuesday. But Powell quoted White House physician William M. Lukash as saying that "there has been considerable lessening of the discomfort" yesterday for the president, who slept about six hours after getting little sleep on Wednesday night.

Carter was host at a Christmas reception for the White House press corps Wednesday night and stood in a receiving line to greet more than 1,000 guests. He and his wife, Rosalynn, left the reception early, but there was no indication then that he was in pain.

Powell said Lukash would examine the president later last night and again early this morning, after which a decision would be made on whether Carter should go through with plans to leave this afternoon for his home in Plains.

Powell quoted Lukash as saying that "if the improvement continues, the president will probably want to go."

The press secretary said Carter had taken "routine pain medication" for his discomfort, an affliction shared by 30 percent of all adults at somet time.

The president was also examined, Tuesday and yesterday, by Dr. Lee Smith, a specialist from the Bethesda naval hospital, Powell said. In addition, he said, the White House had consulted with Dr. Edwin Lockridge of Atlanta, who treated Carter in 1974 for a similar but less acute attack.

Powell said the president has suffered from a hemorrhoid condition "virtually from the time he was in college." He said Carter has suffered "rather considerable pain the last couple of days" and that the current episode is "certainly the most serious in terms of discomfort" and the president has experienced.

"The man is receiving adequate medical treatment," Powell said. "He's been hurting for three days and he ain't going to die."

Although at times he has shown signs of the physical strain of his job, Carter has generally appeared to be in good health. Yesterday was the first time he was known to have canceled appointments for reasons of health. Those appointments - with his economic advisers and two meeting on the fiscal 1980 budget - were handled by Vice President Mondale.

Lukash said recently that Carter had undergone a simple surgical procedure - "banding," or using rubber bands to cut off the circulation to the offending protrusions and make them atrophy - before he was elected president.

Usually a successful operation or some milder version such as the above ends the problem. But in a few cases there can be a recurrence.

Anatomically, hemorrhoids, or piles, are simple swellings of the veins of the rectal and anal area.

Piles are often the subject of jest or embarrassment, but the condition can be far from trivial. Left untreated it may lead to serious bleeding and even anemia. Or piles may become inflamed and infected and lead to more serious bleeding and even anemia. Or piles may become inflamed and infected and lead to more serious ulcerations or fissures.

Often, simple medical treatment can arrest the problem before it becomes advanced. This may consist of lubrication and medicated suppositories or, sometimes, injections.

If medical treatment doesn't work, the next step usually is some kind of surgery. Sometimes cryosurgery, an ice-cold probe, is used instead of the knife. A patient may have to stay in the hospital three or four days or more after surgery, and is often unable to return to work for 10 days or more.

The operation itself is a simple one that usually takes no longer than 20 or 30 minutes. But the pain afterward may be severe. And it may be several days before the patient recovers normal bowel function.