How much information should a physician provide about a procedure or illness in order to help a patient make an informed choice? Is there such a thing as too much information, or knowledge that is contrary to a patient's best interests? Is withholding information the same as lying?

I've been thinking about these questions because I see a problem developing in medicine. To put it bluntly, too many patients today know too much -- or think they do. In addition, many people believe that the more a patient knows the better. In many cases, that simply is not true.

While a doctor must be honest with a patient, answering all questions truthfully and volunteering information a patient needs to know, it is the physician's responsibility to withhold -- as much as possible -- information that might be harmful to the patient.

Little good can be achieved, for example, when a patient who absolutely must have surgery is told in the greatest detail about the most remote complications possible -- unless the patient insists.

The patient could become virtually paralyzed, rejecting even the most basic and simple treatment out of confusion or fright. An extremely suggestible patient might develop certain side effects from medications after hearing they are possible.

This raises an aspect of the patient-physician relationship everybody finds disturbing: lying. Most medical professionals feel that integrity is probably the most important quality anybody can have. But my experience as a clinician tells me there are some circumstances in which lying is permissible, possibly even preferable. It is, for example, very important for the patient's psyche not to be disturbed in the immediate postoperative period.

Assume that you are the physician, stopping by the recovery room, and the patient asks you the result of the operation. You tell the truth: 'We found cancer, and it is metastasizing.' "

That bit of truthfulness is likely to have dreadful consequences, because the patient may well give up any hope of recovery.

The immediate postoperative course, as I see it, may extend 48 hours, long past the time the patient leaves the recovery room. It may take that long for the patient to come to terms with the massive insult of the operation.

A lot of things can happen in that period. A patient who stops breathing well, because of depression, may develop pneumonia. Another patient may not want to get out of bed, with deleterious long-term effects.

What can a physician say that is neither a direct lie nor potentially devastating? Any number of things, including, "I have not seen the pathologist's report yet," or "Let's talk about it later. Tell me how you are feeling right now."

In part, the current attitude that a physician should tell a patient everything is an understandable reaction to the unfortunate legal realities of our contemporary society. Doctors must protect themselves: providing a patient with every possible detail goes a long way toward establishing a bulwark against legal proceedings should something go wrong.

A patient is best served when the doctor imparts enough information to decide whether to accept the diagnosis and to come to grips with the results of surgery or treatment. That, of course, raises the question, how much and what specific information is necessary?

The truth is, physicians can talk a patient into almost anything if the information they provide is distorted. So while I would hardly like to return to those days when every physician was an almost godlike figure whose word was taken as gospel, I do believe that it is part of our obligation to make judgments.

I recently talked to a colleague who stated that he was absolutely neutral in his recommendations in a controversial area. Patients come to us for our expertise and valued opinion. A patient may seek other opinions -- and often should be encouraged to do so -- and may ultimately reject the doctor's advice. That is his or her right.

But patients should not be making decisions with their minds so cluttered with unrelated data that a sense of perspective is lost.

Misinformation is another aspect of the problem. We live in an era when we are bombarded with "facts." For example: The wife of someone I know developed a mass in her breast, and her doctor quite correctly wanted her to have a mammogram to determine if the lump was malignant. She said she had read somewhere that women under 40 -- she was 26 -- should not undergo mammography since the radiation might cause cancer and therefore refused.

What she had read, of course, is that women under 40 need not undergo screening mammography, which is an entirely different matter.

The tumor was in fact malignant, and two years later she was dead of metastatic cancer. Now there is no indication that things would have turned out differently with a mammogram, but the nature of breast cancer is such that timing is crucial, and successful treatment depends on catching the problem at the earliest possible stage. So this was a case in which the patient had too much information -- misinformation, really -- and not enough knowledge.

Information obtained from television and our newspapers is not necessarily accurate or filtered through editorial boards, as it is in medical journals. Thus, opinions are reported verbatim as presented in a journal or at a meeting without any chance for the other side or rebuttal.

Obviously, not all reports are one-sided or inaccurate, but it requires expertise to decide what information is correct.

I believe that communication is vitally important between a doctor and patient. But just as a professor in a classroom cannot begin to tell students all there is to know about a given subject, so too a doctor cannot -- should not -- try to tell the patient every little detail.

The confidence that a doctor projects, the hope that he or she enables his patient to retain, is in many ways as important and beneficial as anything else he does. Toward that end, the practice of good, sound medicine often requires not total, but rather proper, communication.Lester J. Karafin, a surgeon, is chief of the division of urology at the Medical College of Pennsylvania and professor of urology at Temple University.