*     Service de Gynécologie, Hôpital F. Guyon, 97400 Saint-Denis, Réunion, France;
**    Service de Néonatologie, Hôpital F. Guyon, 97400 Saint-Denis, Réunion, France;
***   Cabinet d’Echographie, Route du Moufia, 97400 Saint-Denis, Réunion, France;
****  Service de Néphrologie, Hôpital F. Guyon, 97400 Saint-Denis, Réunion, France;
***** Student, Arizona State University. University Drive and Mill Avenue Tempe, Arizona 85281.

Case report

A 30-year-old G4P2, from a non-consanguineous couple, was referred to our center at 25th week of pregnancy due to the intrauterine growth restriction of the fetus and oligohydramnios.

Her first twin pregnancy was terminated at 27th week (dichorial, diamniotic) due to oligohydramnios and hyperechoic, hypoplastic kidneys of the fetuses. Pathological analysis found renal tubular dysgenesis of both babies (male and female) (2001).

The second pregnancy was normal and the patient had delivered a healthy baby by cesarean section due to the breech presentation (2002).

The third pregnancy ended by spontaneous miscarriage (2005).

Her current fourth pregnancy was complicated by the intrauterine growth restriction and oligohydramnios. Our ultrasound at 25th week of gestation found the anhydramnios and the kidneys were hyperechoic, but of normal size. Perfusion of the renal arteries was normal. At 26th week the same anomalies were observed.

Based on the patient"s anamnesis and our ultrasound findings we assumed the diagnoses of the renal tubular dysgenesis in the fetus. The parents opted for termination of the pregnancy. An autopsy was done and demonstrated abnormality of renal development with particular expression in the maturation and differentiation of tubules. The final diagnosis of the renal tubular dysgenesis was confirmed.

Images 1, 2: 25th week of pregnancy. The images show hyperechoic kidneys of normal size.

Images 3, 4: 25th week of pregnancy. Gray scale and color Doppler images show hyperechoic kidneys of normal size and normal perfusion of the kidneys (Image 3).

Images 5, 6: 25th week old fetus. Parasagittal (image 5) and transverse (image 6) images show hyperechoic kidneys of normal size.

Images 7, 8: Pathological specimens; a rectal prolapse was present in the baby (image 8)

Definition

Renal tubular dysgenesis is a rare congenital abnormality of renal development, characterized by the anomalies of the maturation/differentiation of tubules. The proximal tubules are short and poorly developed [1].

History

Renal tubular dysgenesis was first described by Allanson et al in 1983, in two stillborn siblings from a nonconsanguineous couple, with diffuse renal tubular dysgenesis [2, 3].

Prevalence

Renal tubular dysgenesis is a rare congenital anomaly and the exact incidence is unknown. Recently Klassen et al (2007) described 23 fetuses with renal oligohydramnios, among which three fetuses showed to have the renal tubular dysgenesis [5].

Etiology

Renal tubular dysgenesis has been described as a congenital familial disease (autosomal recessive), variably with features of oligohydramnios and pulmonary hypoplasia. Nevertheless, a similar tubular lesion has been reported for conjoined twins with twin-twin transfusion syndrome or acardia and in infants of mothers taken antihypertensive agents, including angiotensin-converting enzyme inhibitors. Renal tubular dysgenesis can be seen either as a unilateral lesion in young infants with renal artery stenosis due to arteritis or medial arterial calcinosis [6].

Renal tubular dysgenesis can be associated with: 

• Fetal exposure to angiotensin-converting enzyme inhibitors (for example Captopirl, Enalapril) [1];
• Fetal exposure to angiotensin II receptors antagonists (Sartans) [8];
• Fetal exposure to non steroidal anti-inflammatory drugs [4];
• Twin-twin transfusion syndrome [4];
• Genetic form of renal tubular dysgenesis [1]. 

Pathogenesis

Poorly developed renal proximal convoluted tubules are the cause of consequent clinical findings in renal tubular dysgenesis (oligohydramnios, renal insufficiency).

Sonographic findings

Renal tubular dysgenesis usually manifests by:

• Oligohydramnios - the onset of oligohydramnios is delayed and variable, usually after 22 weeks, resulting in various deformities from the uterine oppression;
• Potter’s sequence - with distinctive compressed face and often limb deformities;
• Pulmonary hypoplasia - is not a systematic finding and depends on the duration of the exposure to oligohydramnios;
• Hyperechoic kidneys (as in our case).

Implication for targeted examination

Prenatal diagnosis of the renal tubular dysgenesis is very difficult and nearly impossible in the first proband. According to Ramalho [3], the condition can only be suspected with the late appearance of oligohydramnios in the presence of normal kidneys on the ultrasound. Nevertheless, in our case the fetus presented with hyperechoic kidneys.

Differential diagnosis

Hyperechogenic kidney is increasingly diagnosed during the prenatal period. The sonographic signs may correspond too numerous kidney diseases with very different prognoses and outcomes. They include obstructive dysplasia, bilateral multicystic dysplasia, genetically inherited renal diseases, genetic syndromes, renal vein thrombosis, toxic injury, infections (particularly CMV), ischemia, aneuploidy, and in some cases, the hyperechogenicity of the kidneys represents just a normal variant [2].

The hyperechogenicity can be present in different regions of the kidneys [10]:

• Diffuse hyperechogenicity:
  • Autosomal recessive polycystic kidney disease (prenatal diagnosis is possible only during the second half of pregnancy, when bilaterally and enlarged echogenic kidneys are visible on the ultrasound;
  • Autosomal dominant polycystic kidney disease (although the age of clinical onset of this disorder is typically in the third to fifth decade of life, early manifestations during the prenatal life have been reported, and the most common finding was the enlarged hyperechogenic kidneys);
  • Ivemark II syndrome;
  • Cystic kidney dysplasia;
  • Obstructive uropathy;
  • Bardet-Biedl syndrome;
  • Meckel syndrome.
• Hyperechogenicity of the cortical part of the kidneys:
  • Autosomal dominant polycystic disease;
  • Trisomy 21;
  • Meckel syndrome.
• Hyperechogenicity of the medullar part of the kidneys:
  • Medullar of the kidney;
  • Bardet-Biedl syndrome;
  • Autosomal recessive polycystic disease;
  • Renal vein thrombosis.

Prognosis

The prognosis is always poor [5, 6]. In the postnatal period, the neonates with renal tubular dysgenesis present with anuria and renal insufficiency and usually die a few hours or days after birth. 

Recurrence risk

The renal tubular dysgenesis is inherited by an autosomal-recessive trait, with 25 % risk of recurrence in another pregnancy.

Management

Parents of an affected child must be informed about the autosomal recessive trait of inheritance, with 25% risk of recurrence and about the impossibility of the prenatal diagnosis before the appearance of the oligohydramnios. With positive anamnesis of the renal tubular dysgenesis in previous pregnancy, an interruption of pregnancy can be proposed when oligohydramnios appears. Nevertheless, the definitive diagnosis is only accomplished postnatally by autopsy, as in our case. Perhaps, the diagnosis could be improved by antenatal biopsy of the kidneys.

References

1. Lacoste M., YI CAI, Guicharnaud L., Mounier F., Dumez Y. et al- Renal tubular dysgenesis, a not uncommon autosomal recessive disorder leading to oligohydramnios: Role of the rennin-Angiotensin system. J Am Soc Nephrol 2006; 17: 2253-63. 

2. Brun M, Maugey-Laulom B, Eurin D, Didier F, Avni EF. Prenatal sonographic patterns in autosomal dominant polycystic kidney disease: a multicenter study.Ultrasound Obstet Gynecol. 2004 Jul; 24(1):55-61.

3. Wisser J, Hebisch G, Froster U, Zerres K, Stallmach T, Leumann E, Schinzel A, Huch A. Prenatal sonographic diagnosis of autosomal recessive polycystic kidney disease (ARPKD) during the early second trimester. Prenat Diagn. 1995 Sep;15(9):868-71.

4. Ramalho C, Matias A, Brandao O, Montenegro N. Renal tubular dysgenesis: report of two cases in a non-consanguineous couple and review of the literature. Fetal Diagn Ther. 2007;22(1):10-3. 

5. Klaassen I, Neuhaus TJ, Mueller-Wiefel DE, Kemper MJ. Antenatal oligohydramnios of renal origin: long-term outcome. Nephrol Dial Transplant. 2007 Feb;22(2):432-9.

6. Kemper MJ, Neuhaus TJ, Timmermann K, Hueneke B, Laube G, Harps E, Mueller-Wiefel DE. Antenatal oligohydramnios of renal origin: postnatal therapeutic and prognostic challenges. Clin Nephrol. 2001 Dec;56(6):S9-12.

7. Landing BH, Ang SM, Herta N, Larson EF, Turner M. Labeled lectin studies of renal tubular dysgenesis and renal tubular atrophy of postnatal renal ischemia and end-stage kidney disease. Pediatr Pathol. 1994 Jan-Feb;14(1):87-99.

8. Vendemmia M, Garcia-Meric P, Rizzotti A, Boubred F, Lacroze V, Liprandi A, Simeoni U. Fetal and neonatal consequences of antenatal exposure to type 1 angiotensin II receptor-antagonists. J Matern Fetal Neonatal Med. 2005 Aug;18(2):137-40.

9. Kumar D, Moss G, Primhak R, Coombs R. Congenital renal tubular dysplasia and skull ossification defects similar to teratogenic effects of angiotensin converting enzyme (ACE) inhibitors. J Med Genet. 1997 Jul;34(7):541-5. 

10. Vavasseur C.- Conduite à tenir échographique devant des reins hyperéchogènes. Med Foet Echo Gynecol 2006; N°66: 30-39.