The advent of intravenous kidney dyes has opened up additional fields of investigation. Prior to the period of the dyes, the investigation of the urinary tract in pregnancy was disturbing and possibly harmful to the patient. In consequence, comparatively few complete studies of the normal urinary tract in pregnancy were done. In the last few years, several such studies have been made.1 These studies have disclosed certain facts which have been valuable in clinical investigation of pathologic conditions existing in pregnancy, such as pyelitis.
The study by intravenous dyes of the urinary tract in pregnancy meets ideal conditions. It is known that intravenous urography succeeds best when a certain degree of obstruction between the kidney and the bladder coexists with a fair to good excretory function of the kidneys. Such a combination of clinical circumstances is found in pregnancy. These studies have revealed a high degree of dilatation of the upper
BAKER EC, LEWIS JS. COMPARISON OF THE URINARY TRACT IN PREGNANCY AND PELVIC TUMORS. JAMA. 1935;104(10):812–815. doi:10.1001/jama.1935.02760100022007