Section III. THE DECUBITUS POSITIONS
2-18. ESSENTIALS OF THE POSITIONS
In any radiographic decubitus position, two conditions coexist:
a. The patient must be lying down.
b. The central ray (CR) must be horizontal.
a. There are four decubitus positions--dorsal, ventral, right lateral, and left lateral
(figure 2-41). These names signify the surface of the body upon which the patient is
resting in a recumbent position. In the dorsal decubitus position, the patient is supine.
In the ventral decubitus position, the patient is supine. In the right lateral decubitus
position, the patient is lying on his right side. In the left lateral decubitus position, the
patient is lying on this left side.
b. Using a horizontal CR, it is possible to secure two different projections for
each decubitus position. The lateral projections (right and left) can be accomplished
with the patient in either the left lateral decubitus or right lateral decubitus position.
c. If a "PA projection of a left lateral decubitus position" is requested, the
projection should be made as the patient lies on his left side. The vertical film holder
should be supported at the anterior aspect of the patient's body; the horizontal CR
should enter the posterior surface and exit at the anterior surface. For a left lateral
projection of a dorsal decubitus position, the patient should be in a supine position. The
vertical film holder should be supported at the left side of the patient; the horizontal CR
should enter the right side and exit from the left. Lateral projections of dorsal or ventral
decubitus positions of the thorax or abdomen may also be referred to as "transthoracic"
2-20. CLINICAL USE
Decubitus positions are used for two main reasons:
a. To effect a shift of fluid, air, contrast media, or anatomical part so that
additional diagnostic information can be obtained in a radiograph.
b. To make desired radiographs that would ordinarily be accomplished by
rotating a part and using a perpendicular CR, but cannot be performed in this instance
because of the condition of the patient.