False-negative results of Hemoccult test in colorectal cancer.

physical dependence varies, the most important factor being the degree to which function of the central nervous system is altered by the drug.4 Our patient received a substantial quantity of powerful drugs acting on the central nervous system over a fairly short period to combat severe pain. In the postoperative period there was no pain and all systemic analgesics were therefore stopped. She then developed the withdrawal syndrome. Normally after a major operation patients require opiate analgesics to relieve pain. Opiate withdrawal symptoms, consequent on preoperative iatrogenic preconditioning, are therefore highly unlikely in the early postoperative stage. Gradually as postoperative pain stops the analgesics are reduced, and this permits some weaning from the narcotic. In this case the morphine acted more effectively in one part of the body (the spinal cord) after the operation than it had done before the operation and yet less effectively in another part, causing withdrawal symptoms. It was this that was so disconcerting and unexpected. Indeed, the diagnosis was made only retrospectively after her complete recovery, coinciding with negative results of all laboratory investigations. As the use of intrathecal morphine increases more patients may develop withdrawal symptoms in the postoperative period, and doctors should therefore be warned of this possibility. Since opiate withdrawal symptoms are easily relieved it is to the patient's immediate benefit that the diagnosis is made early and appropriate treatment begun.