The Fetal Urinoma Revisited

Abstract

The Fetal Urinoma Revisited he fetal urinoma is quite rare and presents as an encapsulated fluid collection caused by the extravasation of urine into the perirenal spaces. Fetal urinomas are strongly associated with obstructive uropathy usually secondary to posterior urethral valves or ureteropelvic junction obstruction. 1,2 Urinomas have been associated with minimal or no function in the affected kidney. 3,4 A recent meta-analysis reported the probability of an ipsilateral nonfunctioning kidney to be as high as 80%. 5 However, this point remains controversial, and there are contradicting and limited data in the literature. 6 Preservation of renal function is reportedly better in lower urinary tract obstruction than in upper urinary tract obstruction. Additional factors at play in predicting renal function include age at presentation and underlying pathologic conditions. 7 Materials and MethodsWe performed a retrospective review of our institution's imaging database, which identified 25 cases of fetal urinomas imaged prenatally at the University of California San Francisco Fetal Treatment Center between 2000 and 2011. Fetal sonograms were reviewed by all authors for specific features, including sex, the side of the urinoma, the location of the urinoma with respect to the kidney, size, and etiology. When available, the prenatal imaging findings were correlated with interventions and outcomes. The fetal urinoma is a rare but important diagnosis, as it indicates substantial underlying obstruction with implications for the functionality of the affected kidney. This case series describes a single center's experience with the diagnosis and management of fetal urinomas. All 25 cases were diagnosed or referred to our medical center over an 11-year period. Most cases were secondary to either posterior urethral valves or ureteropelvic junction obstruction. Fetal interventions, including percutaneous drainage of the urinoma and cystoscopic alleviation of bladder outlet obstruction, were performed in 4 cases.

Fetal urinoma: A case report and review of the literature

“…The sonographic appearance of an urinoma is a featureless ellipsoid or crescent‐shaped cystic mass adjacent to the kidney and spine. Large urinomas can be difficult to image as they can distort and displace the kidney, with the direction of renal displacement indicating whether the urinoma is in the anterior or posterior paranephric space 4 . Furthermore, small urinomas can also be difficult to diagnose as they may mimic a dilated calyx in the setting of hydronephosis.…”

Prenatal Diagnosis of a Urinoma and Dilated Azygous Vein

“…The rupture of renal calyces can be due to microperforation of the renal pelvis with secondary extravasation of urine into the retroperitoneal spaces. The urinoma may act as a “pop‐off valve” and can be associated with preservation of some urinary function, if obstruction is located in lower urinary tract, but when obstruction is located in the ureteropelvic junction, the prognosis for renal function on the affected side is poor, as seen in this case …”

“…The appearance of a urinoma on a US examination typically involves a cystic mass, which lies adjacent to the kidney and spine. In fact, Yitta et al stated that any fluid‐filled mass that touches the lumbar spine is presumed to be a urinoma. Magnetic resonance imaging is rarely used for diagnostic purposes and is reserved for cases in which US is unable to conclusively show the relationship of the kidney to the mass …”

“…The urinoma may act as a "pop-off valve" and can be associated with preservation of some urinary function, if obstruction is located in lower urinary tract, but when obstruction is located in the ureteropelvic junction, the prognosis for renal function on the affected side is poor, as seen in this case. 6,7 The appearance of a urinoma on a US examination typically involves a cystic mass, which lies adjacent to the kidney and spine. In fact, Yitta et al 7 stated that any fluid-filled mass that touches the lumbar spine is presumed to be a urinoma.…”

Neonatal Imaging Evaluation of Common Prenatally Diagnosed Genitourinary Abnormalities

“…4 However, it has recently been reported that the presence of a fetal urinoma suggests a poor prognosis for the ipsilateral kidney's functionality and that the probability of a nonfunctional, dysplastic ipsilateral kidney in these patients may be as high as 80%. 79,80 PUVs may be associated with renal dysplasia with or without cysts, which can be detected on US, preferably with the use of linear transducers. 75,76,81 VCUG remains the reference standard imaging for the diagnosis of PUV.…”