The Ten Day rule and Its Implementation at the Kenyatta National Hospital

Abstract

Of all sources of ionising radiation, medical radiation contributes the greatest amount of man made radiation. With the discovery of X-rays in 1895 (publicly announced in the press, January 4th, 1896) by Professor Rontgen, there was a world wide enthusiastic use of its diagnostic potentials. It was however soon after (early 1901) discovered that it was potentially dangerous if not used properly. Its teratological potential was realised much later in the 1920's. During this period published reports described developmental abnormalities in children who had been heavily irradiated in utero (14). It can be stated that if the pre-implantation embryo is exposed to ionising radiation it may be killed and absorbed and the woman never·know she had conceived (1). X-radiation soon after conception is likely either to be lethal or to allow the embryo to survive without evidence of anomalies. When the embryo consists of only a few cells at the time of irradiation the damage to even one cell is likely to be fatal to the whole embryo. From implantation, (8th to 9th day) through the

first six weeks is the most radiosensitive period, known as the period of major organogenesis. At this time X-radiation could cause any of a great number of possible congenital abnormalities as reported in the literature. It is during this period that most of the embryonic cells are in their "blast" stage, (enythroblast, myoblast, condroblast, neuroblast, etc.). At this stage of transformation all cells are particularly sensitive to radiation. (This happens to be the period in the human embryo during which the tranquilisor, thalidomide, had its effects and also the period when rubella is most damaging). From six weeks to the end of pregnancy recognisable structural abnormalities are much less likely to occur, but cell depletions resulting from radiation insult can cause functional disabilities. Data from various experiments with animals show that even diagnostic exposure levels may be teratogenic to the embryo or foetus (21, 23, 24, 32, 36). There is probably no developmental stage which is "safe" in the sense of being entirely imune to some effects of ionising radiation. That is why an X-ray request form should have a question relating to menstrual history, so that any pelvic radiography should be scheduled during the first ten days following the

onset of the last menstrual period. During this period, there is less chance that unrecognised pregnancy could be missed. Ovulation is known to be any time after the tenth day, up to the fourteenth day after the first day of the L.M.P. After ovulation conception is most likely, therefore all radiological procedures of abdominal lesion in female patients of productive age should be done, before this period, that is during the first ten days after the commencement of the menstrual period. The referring physician should take positive steps to ascertain and document whether the patient mayor may not be pregnant. The nature and degree of the risks to the developing embryo from diagnostic radiological procedures must be well appreciated and care and concern shown by all attending such patients.