Jeanne S. Chow MD, Abstract Co-Author: Nothing to Disclose

Carol Beer Benson MD, Presenter: Nothing to Disclose

Robert Lawrence Lebowitz MD, Abstract Co-Author: Nothing to Disclose

To characterize the significance of an empty renal fossa seen on prenatal ultrasound.

From a prospectively collected database at our institution, we identified all fetuses in whom no kidney was found in one renal fossa on prenatal ultrasound between 1989 and 2003. The gestational age at diagnosis, the side of the absent kidney, fetal gender, presence of an ectopic or fused kidney, other congenital anomalies diagnosed prenatally and postnatally, and results of subsequent prenatal and postnatal imaging studies, and autopsy studies were recorded when available.

Ninety-three fetuses were found on prenatal ultrasound to have a unilateral empty renal fossa: 49 cases were absent on the left and 41 on the right. In 3 cases, the side was not recorded. Forty-four (60%) of the fetuses were male and 29 fetuses were female. For 20, the gender was not recorded. The gestational age at diagnosis ranged from 17.3 to 39.9 weeks (mean 29.5 weeks). In 36 cases prenatal diagnoses were confirmed postnatally by imaging studies or by autopsy. The missing kidney was found in the pelvis in 34 cases. In 4 cases, the kidneys were fused. One kidney was found in the chest in a patient with congenital diaphragmatic hernia. One of the unidentified kidneys was infiltrated by tumor. The absent kidney was never located in 44 cases and presumed to be congenitally absent. Seven kidneys originally thought to be absent were normally located but dysplastic. Two were later found to be normal appearing and normally located. In 42 patients, other congenital anomalies were identified either prenatally, postnatally or both with the most common being genitourinary (31) and cardiovascular (11). Of the 77 cases with the number of umbilical cord vessels recorded, 68 had normal three vessel cords and 9 (12%) had two vessel cords.

If one kidney is not found in the renal fossa, 37% can be found in the pelvis and 47% are absent. An empty renal fossa is more common in male than female fetuses and is often (43%) associated with other congenital anomalies, most often involving the genitourinary and cardiovascular systems.

Chow, J, Benson, C, Lebowitz, R, The Clinical Significance of an Empty Renal Fossa on Prenatal Ultrasound.  Radiological Society of North America 2004 Scientific Assembly and Annual Meeting, November 28 - December 3, 2004 ,Chicago IL. http://archive.rsna.org/2004/4408409.html