Address correspondence to Carlo A. Dell"Agnola, MD, University of Milan - Italy, Dept. of Pediatric Surgery - Istituti Clinici di Perfezionamento, Via Petrarca 18, 20123 - Milano, Italy; Ph: 39-2-4800-2063; Fax: 39-2-5830-9597; ¶ Dept. of Urology - Ospedale S.Gerardo-Monza, ºDept. of Ob-Gyn, Ospedale S.Paolo

Synonyms: None.

Definition: Obstruction of the urinary tract at the junction of the renal pelvis and the ureter.

Prevalence: Unknown. M5:F1 in cases diagnosed postnatally.

Etiology: Sporadic, but familial cases have been reported.

Pathogenesis: In most cases, ureteropelvic junction obstruction seems to be of functional nature. Abnormalities in the development of the innervation of the muscularis of the ureter seem to play an important role in the pathogenesis of ureteropelvic junction obstruction.

Associated anomalies: Extraurinary anomalies in up to 19% of cases and include: Hirschsprung"s disease, cardiovascular abnormalities, neural tube defects, sagittal synostosis, mandibular hypoplasia, esophageal atresia and distal fistula, imperforate anus, syndactiyly.

Differential diagnosis: Includes multicystic dysplastic kidneys and perinephric urinoma secondary to rupture of the severely dilated renal pelvis.

Prognosis: Good.

Management: Unilateral ureteropelvic junction obstruction should not alter standard obstetrical management as long as the contralateral kidney looks normal. Management of bilateral ureteropelvic junction obstruction depends upon the gestational age, amount of amniotic fluid and functional renal reserve provided by chemical analysis of a fetal urine sample. Associated anomalies should always be searched for and rapid fetal karyotyping is indicated.

MESH Ureteral obstruction ICD9 753.2 CDC 753.210

Introduction

Invasive procedures or fetal surgery to drain obstructed urinary tract appear as an attractive extension of prenatal diagnosis but mixed results may decrease the value of these prenatal interventions¹. Even a less invasive procedure such as fetal urine sampling for the evaluation of renal function may be questionable, and the predictive value of urine testing is controversial². Moreover, a high incidence of maternal and fetal complications has been reported after these procedures³ (Table 1). Major neonatal complications related to prenatal procedures can also occur. The following case illustrates limits and possible complications that must be taken into account by the obstetrician planning invasive intervention on fetal uropathy.

Table 1: Complications of fetal intervention³

Case report

Prenatal management

A 25-year-old white woman G₁P₀ was referred to our Perinatal Unit after a routine ultrasound scan raised the suspicion of unilateral obstructive uropathy at 32 weeks. On our ultrasound examination, the diagnosis of renal cyst (41 x 46 mm) and severe hydronephrosis was made (fig. 1).

An echocardiography revealed mitral regurgitation. We had previously observed a case of heart failure following compression by a renal mass. Therefore, aggressive intervention consisting of renal drainage was decided upon in order to avoid further possible compressive complications. At 33 weeks, 50 cc of fetal urine were drained from the kidney using a 20 gauge needle under continuous ultrasound guidance. A fetal blood sample was also obtained from the placental insertion of the umbilical cord for rapid fetal karyotyping. The whole procedure lasted 10 minutes and the kidney appeared to be totally emptied. Fetal renal function was assessed (Table 2) showing the following results: Natrium: 78 mEq/l, Chloride: 76 mEq/l and osmolarity: 226 mOsm/l. The fetal karyotype was normal (46, XX).

A repeat ultrasound examination at 35 weeks and 2 days demonstrated the reformation of the renal cyst (42 x 43 mm). Controversies in the interpretation of functional and sonographic data did not allow a definitive diagnosis. At this point the suspicion was that the renal puncture had caused a urinary fistula; in fact, the posterior localization of the cystic mass led us not to consider a ureteropelvic junction obstruction. A cesarean section was decided upon at 38 weeks for breech presentation. A female neonate weighing 3020g was delivered (Apgar 6 and 10 at 5 and 10 minutes).

Table 2: Prognostic indicators of renal function⁴ in the fetal urine

Diagnostic procedures at birth

An ultrasound examination performed at 3 days of life revealed a double cystic mass, and kidney parenchyme was not visible; thus, a diagnosis of multicystic kidney was suspected. The diagnosis was confirmed at 23 days by a mercaptoacetiltriglicine isotope renogram showing a right nonfunctioning kidney (fig 2).

Of course, the nonfunctioning kidney could have been explained by a high pressure preventing glomerular function, but up to this point a diagnosis of multicystic kidney disease still appeared to be reasonable. Cystography excluded vesico-ureteral reflux. Following our policy in cases of multicystic kidney, a nephrectomy was decided upon.

Surgery

Through a right extraperitoneal lombotomy the kidney was exposed, and a huge hydronephrosis due to a ureteropelvic junction obstruction was found with a thin residual parenchyme of soft consistency (fig. 3).

Since the renogram had excluded any function at all, the nephrectomy was undertaken.

Dissection of the hylum was easily accomplished. Normally developed artery and vein were found and resected. Major difficulties arose while attempting to remove the kidney because of the adherence of the upper pole to the diaphragm and adrenal gland. The adherence with the diaphragm imposed a partial resection (30 x 30 mm), creating a diaphragmatic hernia. Because a hematoma was found between the adrenal gland and the upper pole of the kidney, three quarters of the gland had to be sacrificied, leaving only the cortical part. The right lower lobe of the lung was intact. Finally, adhesions with the cava were carefully dissected, allowing a total removal of the kidney. The diaphragmatic hernia was successfully repaired. The surgical procedure lasted 5 hours and 30 cc of blood had to be transfused. The postoperative course was uneventful. At two months, the girl is doing well.

Pathology

The pathological examination confirmed the surgical diagnosis of hydronephrosis due to fibrotic pyeloureteral junction obstruction. There was diffuse parenchymal dysplasia but normal glomeruli and tubular structures (fig. 4).

Discussion

Several considerations can be drawn. The first is that prenatal renal function tests are unlikely to be accurate to assess the effective condition of the kidney. In fact, the renal scintigraphy performed early after birth excluded any function. Renal scintigraphy is, at present, the best examination for identifying renal function¹. Since urinary tract infections did not occur before the surgery, the cause of parenchyme deterioration must be searched for in the prolonged exposure to a high pressure due to the ureteropelvic junction obstruction starting from the early intrauterine period. Actually, the presence of dysplastic areas among normal parenchyme would suggest an obstruction occurring early in gestation^1,5. We must therefore conclude that renal function test is not useful in borderline cases.

The second major consideration about this intrauterine procedure is that it transformed a simple nephrectomy into a complicated operation, endangering the patient"s life.

In conclusion, more precise indications to intrauterine procedures have to be selected and a more anatomical approach must be found for fetal urine sampling.

References

1) Thomas DFM, Gordon AC: Management of prenatally diagnosed uropathies. Arch Dis Child 64:58-63, 1989.

2) Wen J-G, Tong E-C, Yuan J-Y: The study of pelvic pressure, renal structure and function in congenital hydronephrosis 2nd Beijing International Conference of Urological Surgeons (Asian Association of Pediatric Surgeons). Beijing (China) September 16th-19th 1991.

3) Selder JS, Duckett Jr. JW, Snyder HM: Intervention for fetal obstructive uropathy: has it been effective? Lancet 31:1007-9, 1987.

4) Crombleholme TM, Harrison MR, Golbus MS, et al: Fetal intervention in obstructive uropathy: prognostic indicators and efficacy of intervention.  Am J Obstet Gynecol 162:1239-44, 1990.

5) Beck AD: The effect of intra-uterine urinary obstruction upon the development of the fetal kidney. J Urol 105:783-9, 1971.