(6) The first film is exposed at a predetermined interval following the
injection of the contrast solution. This interval usually ranges from 8 to 20 seconds,
depending upon the circulating time. Subsequent films are exposed at predetermined
intervals. If a conventional x-ray unit is being used, the subsequent exposures should
be made as rapidly as possible, especially during the critical filling phase or when there
is maximal concentration of the contrast material in the cortical and medullary regions of
the kidneys. The patient is instructed to hold in his breath and exposure is made on full
inspiration. If a rapid-sequence serializing apparatus is used, two or more (only when
indicated by the examiner) exposures may be made while the patient continues to hold
his breath. Usually, exposure of films is discontinued approximately 35 seconds
following the completion of the injection.
(7) The identification marker should be placed on each of the cassettes prior
to beginning the examination.
(8) All films should be developed as quickly as possible and presented to
the examiner for reading before the patient is moved off the x-ray table.
(9) Nephrograms may sometimes result as a side-effect. They are apt to
occur during such special procedures as angiocardiography or aortography, wherein
relatively large amounts of contrast solution containing a high percentage of iodine are
introduced at a relatively rapid rate.
(10) A representative nephrogram is shown in figure 2-37.
Figure 2-37. A representative nephrogram.