Ultrasound in acute urinary retention and retroverted gravid uterus

In this issue of the Journal, Yang and Huang1 present a five-patient series exploring the pathophysiology of acute urinary retention in association with a gravid uterus. They report the largest number of cases of urinary retention during pregnancy, and as such should be congratulated. They attempt to characterize the sonographic findings of such a rare clinical event and conclude that the cause of retention is not compression of the urethra, but rather mechanical compression of the lower bladder. Urinary retention during pregnancy has been described in all three trimesters. It is an emergency condition and knowledge of the pathophysiology will help to provide a rational approach to the clinical problem. Retention during pregnancy can occur secondary to lumbar disc herniation, paraurethral abscess, breech presentation, ectopic pregnancy and conversion psychological disorder. A retroverted/retroflexed uterus is another predisposing factor for urinary retention during pregnancy. The incidence of urinary retention due to a retroverted uterus is 1.4%2. Although retroversion is often transient, the gravid, retroverted uterus can become impacted in the pelvis as it enlarges causing retention. Other factors that predispose the gravid uterus to become incarcerated within the pelvis are prior gynecological surgery, pelvic adhesions due to pelvic inflammatory disease and/or endometriosis, and leiomyoma. There are no simple diagnostic tests that help identify the cause of urinary retention during pregnancy. Delay in the diagnosis of retention can result in irreversible uterine ischemia and spontaneous miscarriage. Thus Yang and Huang's report can be considered a landmark endeavor. The use of sonography as a non-invasive diagnostic tool to define the underlying cause of retention should be encouraged in a larger group of patients—and a multi-institutional effort to accrue more data is needed. The use of cystoscopy as a diagnostic tool in this clinical problem has been suggested by some3. Because the cause of retention in pregnancy is external compression, I do not believe that cystoscopy can provide an answer. Further elucidation as to why these patients develop retention may lie in a videourodynamic test. Such a study would provide radiological real-time information regarding the anatomy of the lower urinary tract and identify the point of obstruction. Unfortunately, the use of radiation during fluoroscopy precludes its use as a standard diagnostic test during pregnancy.