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2004-07-14-11 Answer to the Case of the week # 128 © Cuillier www.TheFetus.net


Case of the week # 128

September 24-October 7, 2004

Fabrice Cuillier, MD

Department of Gynecology, Félix Guyon Hospital, 97400 Saint-Denis, Réunion Island, France.

This is a 23-year-old mother with no history of consanguinity. A scan performed at 13 weeks of gestation was normal, while a scan at 19 weeks demonstrated a thick nuchal fold [6mm] with normal amniotic fluid volume.

The following are scans performed at 25 and 29 and 31 weeks of gestation:

  

 

The serial scans shown above and performed at different intervals demonstrate a left anechoic mass, gradually increasing in size and occupying more than half of the abdomen. The left kidney is in close proximity to the mass but appears normal. The right kidney and urinary bladder were also normal. At this point, the diagnosis of multicystic disease was ruled out and an obstructive uropathy was considered.

 

The diaphragm was greatly elevated, a pronounced upward shift of the heart was seen and the lungs were so compressed that they could hardly be visualized, suggesting pulmonary hypoplasia. This patient gradually developed polyhydramnios.

 

Due to patient distress, the polyhydramnios and the cystic mass in the abdomen were tapped at 29 weeks of gestation. The fluid from the mass was diagnosed to be urine. A diagnosis of a giant left urinoma without urinary obstruction was made. The decompression procedure was repeated at weeks 30 and 31, as both the polyhydramnios and the urinoma refilled.

 

The female baby delivered prematurely at 33 weeks of gestation and had respiratory distress at birth. She died 20 minutes after birth. An autopsy was performed which showed a fluid collection overlying the left kidney. An absence of the left ureter was noted. The rest of the renal system was normal.

 

Introduction:
Fetal urinoma is a clinical entity that occurs due to urinary extravasation and can be diagnosed early in fetal and/or neonatal period. Its clear association with upper and /or lower severe urinary tract obstruction has been established1. The urinary extravasation may remain contained in the fascia of Gerota, but often extends into perinephric space or beyond, which is the result of increased tubular pressure 2. The direct relationship between urinary tract obstruction and urine extravasation in the perirenal and / or retroperitoneal space has been established since 1953 2-3.
The formation of an urinoma requires the presence of:

  • a functioning kidney,
  • a ruptured collecting system and
  • a distal obstruction 3.

This is thought to occur because of micro-perforation of the renal pelvic walls with subsequent collection of urine either beneath the renal fascia or in the retroperitoneal location.
 
The major causes of urinoma are:

  • renal trauma and or
  • obstructive uropathy.

Fetal urinoma is an uncommon finding in prenatal investigations and previous cases have almost in every instance referred to the presence of an obstructive uropathy, mostly of the

  • posterior urethral valves,
  • uretro-pelvic junction obstruction,
  • primary obstructive megaureter,
  • anterior urethral diverticulum and
  • rarely vesico-uretral reflux 4-5.

However, the prenatal diagnosis of fetal urinoma can be challenging. In this case the giant urinoma occurred in the absence of an apparent obstructive uropathy but was in fact associated with an ipsilateral missing ureter. 

Diagnosis:
Fetal urinoma is an uncommon finding in prenatal investigations 6. Most previous reports have almost in every case referred to the presence of an obstructive uropathy and thus to very high pressures in the upper urinary tract during fetal life causing urinomas. The peculiarity of the urinoma demonstrated in our case was in the fact that there was no demonstratable obstruction in the uretero-pelvic junction or in other tracts (lower ureter, bladder or urethra). The cause of urinoma is often not visible on prenatal investigations. Urinoma secondary to an obstructive uropathy are easy to correlate, since the renal rupture represents a protective mechanism to reduce the high pressure in the urinary tract and to preserve the integrity of the kidney 6-7.

In our case, a nephrostomy tube was inserted in the cystic mass at an early stage and the aspirated fluid was found similar to normal urine.

 

This led to a reasonable suspicion of an obstructive hydronephrosis or other cystic renal diseases such as multicystic dysplasia or polycystic kidney. Other possibilities such as posterior urethral valves, uretro-pelvic junction obstruction, vesico-ureteral reflux and rupture of a cyst in a small dysplastic upper pole need to be considered as well 7-8. Fetal urinoma is also known to occur secondary to urinary tract obstruction such as that found in ectopic ureterocele or partial ureteral atresia 3. There have been reports of fetal urinoma developing after the performance of a traumatic amniocentesis 3.

Prenatal identification of urinoma can be challenging as shown in our case. The diagnosis should be considered when a retroperitoneal cystic mass is associated with signs of upper or lower urinary tract obstruction 9. Urinomas usually lead to anterior displacement of the ipsilateral kidney and this should be remembered whenever a retroperitoneal cystic mass is detected. Urinoma must first be differentiated from hydronephrosis. Thereafter other causes of a retroperitoneal cystic mass, such as lymphangioma, hemorrhagic neuroblastoma, mesenteric cyst, enteric duplication and other cystic renal diseases, namely multicystic kidney, polycystic kidney disease and Wilms tumor have to be excluded 9,10,11.

In a fetus with a unilateral non-communicating urinoma, development of the lungs can be impaired by the associated oligohydramnios and severe longstanding elevation of the diaphragm that resulted from the pressure of the cyst 10. So large urinomas have usually been associated with neonatal death due to pulmonary hypoplasia 12,13,14.

Percutaneous drainage is an effective and safe diagnostic as well as therapeutic treatment. In-utero shunting procedures have not been shown to improve renal function, but they should be reserved for cases of large urinomas that appear to interfere with the functioning of other organ systems, as was in our case 12. Nevertheless the prenatal visualization of a urinoma usually has a poor prognosis. In our case, on the contrary, polyhydramnios was speculated to result from impaired fluid uptake due to compression of the bowels with normal function of the contralateral kidney 6.

References:
1. Adorisio S., Pane A., Zaccara A., Bilancioni E., Giorlandino C., De Gennaro M.- Fetal monolateral urinoma and neonatal renal function outcome in posterior urethral valves obstruction :  the pop-off mechanism. Ped med Chir (Med Surg Ped) 2002 ; 24 : 394-6.
2.Adzick N.S., Harrison M.R., Flake A.W., De Lorimier A.A.- Urinary extravasation in the fetus with obstructive uropathy. J Pediatr Surg 1985 ; 20 : 608-15.
3.Miller M., Korzets Z, Blumenfeld Y., Pomeranz M., Aviram R., Rathaus V., Pomeranz A.- Fetal urinoma as a sign of a dysplastic kidney. Pediatr Nephrol 2003 ; 18 : 65-7.
4.Balcom A.H., Pircon R., Worthington D., Carr M.- Spontaneous resolution of an in utero perirenal urinoma associated with posterior urethral valves. Urology 1999 ; 54 : 366-7.
5.Lowenstein L., Solt I., Talmon R., Pery M., Suhov P., Drugan A.- In utero diagnosis of Bladder perforation with urinary ascites. Fetal Diagn Ther 2003 ; 18 : 179-82.
6.Cimador M., Castagnetti M., Rosone G., Lima M., De Grazia E.- A giant fetal urinoma in a neonate without detectable obstructive uropathy. Eur J pediatr Surg 2003 ; 13 : 355-9.
7.Zimmermann R., Huch A.- A large unilateral contained urinoma in a fetus : an indication for intra-uterine urinary shunting. Fetal Diagn Ther 1993 ; 8 : 268-72.
8.Silveri M., Adorisio O., Pane A., Zaccara A., Bilancioni E., Giorlandino C., De Gennaro M.- Fetal monolateral urinoma and neonatal renal function outcome in posterior urethral valves obstruction: the pop-off mechanism. Pediatr Med Chir 2002 ; 24 : 394-6.
9.Ghidini A., Strobelt N., Lynch L., Berkowitz R.L.- Fetal urinoma : a case report and review of its clinical significance. J Ultrasound Med 1994 ; 13 : 989-91. 
10.Bettelheim D., Pumberger W., Deutinger J., Bernaschek G.- Prenatal diagnosis of fetal urinary ascites. Ultrasound Obstet Gynecol 2000 ; 16 : 473-5.
11.Yerkes E.B., Cain M.P., Padilla L.M.- In utero perinephric urinoma and urinary ascites with posterior urethral valves : a paradoxical pop-off valve ? J Urol 2001 : 166 ; 2387-8.
12.Hutcheson J.C., Canning D.A., Hubbard A.M., Johnson M.P., Carr M.C.- Magnetic resonance imaging of fetal urinoma. Urology 2002 ; 60 : 697.
13.Patti G., Galluzzo M., Rastelli D., Bellussi A., Miele V., Calisti A.- Fetal urinoma caused by pyelo-ureteral obstruction; spontaneous remission. Pediatr Med Chir 1999 ; 21 ; 97-9.

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