Dedicated portable ultrasound devices generally offer a rapid, noninvasive, largely operator-independent means of assessing post-void residual urine (PVR) volume. In most published series, PVR measured by portable ultrasound correlates well with catheterized urine volume. We report 3 cases in which follow-up of falsely elevated PVR measurements on ultrasound resulted in comparatively low catheterized volumes. In all 3 cases, the elevated readings were due to cystic ovarian pathology, which was diagnosed by formal radiologic evaluation and ultimately confirmed operatively in 2 cases. Cystic pathology of the pelvis or lower abdomen may present as an elevated PVR on ultrasound and low urine volume on subsequent catheterization and should prompt further evaluation.