Definition:  Bilateral absence of the kidneys, usually associated with the oligohydramnios sequence.

Synonyms: Potter syndrome (no longer used).

Incidence: 1-2:10,000

Etiology: Usually sporadic occurrence but 20-36% of bilateral renal agenesis (BRA) present a familial recurrence (possibly autosomal dominant with incomplete penetrance and variable expression).

Pathogenesis: result from a lack of induction of the metanephric blastema by the ureteral bud.  The absence of kidney results in the absence of amniotic fluid after 12-13 weeks (before fluid is an exsudate or an extension of the intercellular fluid of the fetus). The oligohydramnios causes the pulmonary hypoplasia. In rare cases of monozygotic twin discordant for the renal agenesis, the pulmonary hypoplasia does not occur[1],[2],[3].

Diagnosis: The diagnosis is first suggested by the absence of amniotic fluid then by the absence of the bladder (Fig. 1) and the lack of kidneys[4]. Color Doppler has been found useful in those difficult exam to identify the lack of renal arteries[5] (fig.2). Before a final diagnosis is made one should think and if possible exclude the possibility of pelvic or ectopic kidneys that could compress the bladder and exclude the possibility of ectopic ureter that could explain the absence of bladder.

Figure 1: Anhydramnios at 15 weeks. This is actually not a bilateral renal agenesis as is demonstrated in fig. 2. The fetus had kidneys. Even with good equipment the gray-scale diagnosis of kidney is not always easy at that age, in part due to the oligohydramnios.

Figure 2: Bilateral renal arteries. Notice how much better the renal arteries are seen in color Doppler than are the actual kidneys. This teenage patient elected to continue the pregnancy but it spontaneously miscarried a month later. The placenta was inserted on a uterine septum, severely limiting the rate of exchanges.

Genetic anomalies: Unknown.

Differential diagnosis: Bilateral renal medullary cystic dysplasia and bilateral renal hypoplasia may appear as BRA[6]. Further normal but non-functioning kidneys anormal placental implantation (on a uterine septum for instance) can lead to the same presentation of severe oligohydramnios. This information is important to convey during patient’s counseling: The concern is not only the renal agenesis (which may be absent) but the oligohydramnios that will lead to pulmonary hypoplasia.

Associated anomalies: Since this is a common anomaly, many different associations have been described (Vacterl, Meckel, chromosome 22 malformations…). In practice most of these are difficult to identify by ultrasound because of the oligohydramnios.

Prognosis: Lethal.

Management: Many authors have suggested the use of amnioinfusion or even intraabdominal infusion of saline in order to better visualize the anatomy[7]. Although there might be indications for such aggressive approach in a non-viable fetuses, these are quite uncommon, and not justified in the majority of cases. Termination of pregnancy can be offered before viability. Standard prenatal care is not altered when continuation the pregnancy is opted for. Confirmation of diagnosis after birth is important for genetic counseling.

Reference:

[1] Lebel RR, Jones G, Israel J, Senica W: Renal agenesis without lung hypoplasia, Vacterl Syndrome. The Fetus 4:3, 7530-5-6

[2] Klinger G, Merlob P, Aloni D, Maayan A, Sirota L Normal pulmonary function in a monoamniotic twin discordant for bilateral renal agenesis: report and review. Am J Med Genet 1997 Nov 28;73(1):76-9

[3] Cilento BG Jr, Benacerraf BR, Mandell J Prenatal and postnatal findings in monochorionic, monoamniotic twins discordant for bilateral renal agenesis-dysgenesis (perinatal lethal renal disease). J Urol 1994 Apr;151(4):1034-5

[4] Bronshtein M, Amit A, Achiron R, Noy I, Blumenfeld Z The early prenatal sonographic diagnosis of renal agenesis: techniques and possible pitfalls. Prenat Diagn 1994 Apr;14(4):291-7

[5] Sepulveda W, Stagiannis KD, Flack NJ, Fisk NM Accuracy of prenatal diagnosis of renal agenesis with color flow imaging in severe second-trimester oligohydramnios. Am J Obstet Gynecol 1995 Dec;173(6):1788-92

[6] Latini JM, Curtis MR, Cendron M, Crow HC, Baker E, Marin-Padilla M Prenatal failure to visualize kidneys: a spectrum of disease. Urology 1998 Aug;52(2):306-11

[7] Haeusler MC, Ryan G, Robson SC, Lipitz S, Rodeck CH The use of saline solution as a contrast medium in suspected diaphragmatic hernia and renal agenesis. Am J Obstet Gynecol 1993 May;168(5):1486-92