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Renal Agenesis/Dysgenesis 

Renal Agenesis/Dysgenesis
Renal Agenesis/Dysgenesis

Lewis B. Holmes

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Absence or severe dysplasia of both kidneys.



(bilateral renal agenesis)


(bilateral renal agenesis/dysgenesis)


(unilateral renal agenesis)


(unilateral renal dysgenesis)



(renal agenesis, unilateral)


(renal agenesis, bilateral)


(renal agenesis, unspecified)


(Potter's Syndrome)

Mendelian Inheritance in Man:


(heredity urogenital adysplasia)


(congenital anomalies of the kidney and urinary tract, including vesicoureteral reflux)

Historical Note

In 1946 Edith Potter (1), a pathologist at the Chicago Lying-In Hospital, published the first of several of her descriptions of the phenotype of infants with bilateral renal agenesis (2, 3). She cited several earlier descriptions of bilateral renal agenesis. She noted that males were affected more frequently, and that the physical features included a “peculiar facies,” flattening of the nose, anomalies of derivatives of the Müllerian and Wolffian ducts, absence of the ureters and hypoplasia of the lungs. This was subsequently referred to as “the Potter Syndrome.” She commented: “There is no apparent relationship between the embryologic development of the lungs and the ureters and kidneys. The reason for delayed differentiation of pulmonary tissue remains unexplained.”

Potter (24) contributed further to the classification of kidney malformations by proposing four types:

  1. I) polycystic kidney disease in familiar type, autosomal recessive;

  2. II) multiple dysplastic kidneys;

  3. III) polycystic kidney disease, adult type, autosomal dominant;

  4. IV) urethral obstruction and obstructive renal dysplasia.

Subsequent experience has shown that the external appearance, described by Potter, can be produced by chronic leakage of amniotic fluid and by many conditions that cause decreased renal function, including bilateral renal dysgenesis, hypoplasia, and multicystic dysplastic kidneys.

This summary focuses on two components of this spectrum: absence of both kidneys and severe dysgenesis, referred to as bilateral agenesis/dysgenesis or a/dysgenesis (BRA/D).


The absence of the kidney can be associated with absence of the ureter, but presence of the adrenal gland (Figure 20-1). The term severe dysgenesis refers to the presence of only a “remnant” of a kidney with no normal kidney structure on histologic sections (5), the features of the Potter Type II dysplastic kidneys (2). The placenta also has a distinctive appearance in association with the prolonged oligohydramnios (3). Amnion nodosum, the term which refers to nodules of amorphous granular material, is present on the surface of the amnion (Figure 20-2).

Figure 20.1 Diagram showing absence of both kidneys in an affected fetus. Two BRA phenotypes are shown, one with ureters present and the other with no ureters associated with absence of both kidneys.

Figure 20.1 Diagram showing absence of both kidneys in an affected fetus. Two BRA phenotypes are shown, one with ureters present and the other with no ureters associated with absence of both kidneys.

Figure 20.2 Fetal surface of placenta showing amnion nodosum.

Figure 20.2 Fetal surface of placenta showing amnion nodosum.

Rare features include an apparent phallus in a 46,XX fetus. Another is the presence of a tail (Figure 20-3).

Figure 20.3 Presence of a “tail” in a stillborn infant with bilateral renal agenesis and sacral agenesis.

Figure 20.3 Presence of a “tail” in a stillborn infant with bilateral renal agenesis and sacral agenesis.

Association Malformations

Most infants with bilateral renal agenesis/dysgenesis (BRA/D) have anomalies only in adjacent anatomic structures, such as the ureters, bladder, and genital structures (1, 513). The affected males show absence of the vas deferens and/or seminal vesicles; females often have absence of a portion of the vagina and anomalies or absence of the uterus.

Among infants with BRA/D, a minority will have anomalies of the sacrum or coccyx, heart defects, imperforate anus, and bowel atresia, primarily esophageal atresia and duodenal atresia. Brain abnormalities, including defects in all migration and formation of gyri, and small size have been reported in most affected infants (14).

Renal anomalies are also associated with myelomeningocele and hemivertbrae (15). Many of these abnormalities are unilateral and include unilateral renal agenesis. Bilateral renal agenesis is associated with two more severe malformations of the sacrum and lumbar vertebrae, including the caudal regression syndrome and sirenomelia. The caudal regression syndrome is a pattern of caudal anomalies with absence of the central portion of the sacrum, hypoplasia of the distal portion of the spinal cord, and associated neurologic deficits and hypoplasia of the buttocks (13, 14, 16).

Sirenomelia is a more severe condition that is almost always lethal and is associated with bilateral renal agenesis (13). There is fusion of the fibular sides of the two legs into a single midline leg, reflecting absence of the midline caudal structures. It has been hypothesized that sirenomelia is due to a “vascular steal” phenomenon, in which nutrients are diverted from the affected regions of the body (17, 18).

A nonrandom association of renal anomalies and limb deficiencies, referred to as the “acro-renal syndrome,” has been postulated. However, there is debate (19) as to whether this is a valid pattern. A systematic analysis of 197 infants with limb and renal abnormalities (19), identified in several population-based surveys of over 5 million births, showed that about 50% had a recognized syndrome or chromosome abnormality. Among the infants with no diagnosis, there was no specific pattern of limb deficiency, which argued against the use of the term “acro-renal syndrome.”

An association between unilateral renal agenesis and cystic fibrosis gene mutations (cystic fibrosis transmembrane conductance regulator [CFTR]) has been identified in the evaluation of men infertile because of congenital absence of the vas deferens (20, 21). Most of these men have one or two different CFTR mutations. The men with congenital absence of the vas deferens often have unilateral renal agenesis. As a parent, this man, with fertility restored, has an increased risk of having a child with unilateral or bilateral renal agenesis. An increased frequency of unilateral renal agenesis has also been noted in men with a seminal vesicle cyst (22).

Bilateral renal agenesis or renal agenesis/dysgenesis is a feature of many malformation syndromes, as has been illustrated in many case series and surveys (68, 10, 1113) [Table 20-1].

Table 20-1 Etiologic heterogeneity of renal agenesis/dysgenesis*



Apparent etiology

renal agenesis


1. Mendelian disorders:



  Familial autosomal dominant


  “Private syndrome” (ref. 23)


2. Chromosome abnormalities:



  trisomy 21, mosaic


3. Syndromes:



1 (1)**


  urethral obstruction



  urorectal septum malformation sequence°


  VACTERL Association



4. Environmental

  Infants of diabetic mothers



5. Twinning



6. Unknown etiology Total


70 (1:2, 946)




* Infants identified in survey of 206,244 liveborn and stillborn infants and elective terminations for fetal anomalies in the years 1972–74, 79–2000 at Brigham and Women's Hospital, Boston. These infants were born to women who had planned always to deliver at this hospital. Affected infants have been excluded whose mothers had planned to deliver at another hospital and transferred their care after the prenatal detection of malformations in the fetus.

** “Private syndrome”: four affected infants born to parents with normal kidneys by ultrasound: one male infant had bilateral renal agenesis and sirenomelia, another male had bilateral hydronephrosis attributed to posterior urethral valves; a third male had type IV cystic kidney disease; their fourth infant, a female had bilateral renal agenesis.

*** Monoamniotic twins, one with VACTERL Association; co-twin had tetralogy of Fallot.

+ One affected twin in diamniotic, dichorionic twin pair.

°A lethal malformation syndrome of unknown etiology (ref. 24).

( ) = infants listed twice

Developmental Defect

The metanephros in the human embryo appears at five weeks postfertilization and the first layer of glomeruli forms by the ninth week of gestation. The first sign of kidney development is the interaction between the metanephrogenic mesenchyme and the nephric duct, two tissues derived from the intermediate mesoderm (25). Branching and nephrogenesis continue in the nephrogenic cortex until the 34th week of gestation. Two major theories about the failure of the kidney to develop are: 1) a deficiency of induction of the nephron caused by a lack of activity of the ampulla; 2) abnormal budding of the ureteric bud from the mesonephiric duct (4). Many genes have been identified as having a crucial role in early kidney development OddI, Wntl, PAX 2, EYA2, SIX1, SIX2, SALL1, FOXC1, and HOX11 genes (2629). These genes are expressed in the mesenchyme and encode transcription factors that are involved in the regulation of the gdnf (glial-derived neurotrophic factor).

The findings in experimental studies in mice suggest that mutations in or deletions involving several genes could be causes of renal agenesis. For example, inactivation of both murine Lim1 (30) and PAX2 (31) cause bilateral renal agenesis with other related malformations. A homozygous deficiency of Fras 1 in mice produced cryptophthalmos, renal agenesis, and blebbed phenotype (32), which is a mouse model of the Fraser Syndrome (Mendelian Inheritance in Man #219000) that includes renal agenesis. Targeted mutagenesis of mouse gdnf has caused bilateral renal agenesis or severe dysgenesis associated with failure of outgrowth of the ureteric bud (33). A hypomorphic mutation of Notch 2 caused defects in development of the glomerulus (34).

Theoretically, the lack of (or absence of) kidney tissue could reflect a primary abnormality in the ureteric bud, which should make contact with the metanephric blastema or a lack of responsiveness in the metanephric blastema. Another potential cause could be defective formation of the Wolffian or Müllerian ducts. While there is a wide range of possibilities, no mutation in any gene involved in kidney development has been identified in a significant percentage of infants with BRA/D.

Experimental oligohydramnios, produced by puncturing and draining amniotic fluid in pregnant day16 (but not day 17) Spraque-Dawley rats, produced the non-renal features of bilateral renal agenesis: hypoplastic lungs, cleft palate, and limb deformities (35).


The prevalence rates for bilateral BRA/D in several population-based surveys have been between 1:5,000 to 1:10,000 or 0.2 to 0.1/1,000 (712). In British Columbia (10) from 1952 to 1982, there were 92 cases of bilateral renal agenesis among 625,132 births (live and stillbirths) for a prevalence of 0.12/1,000. In Arkansas (12), between 1985 and 1990, the prevalence rate, based on birth and death certificates, was 0.14/1,000. In the Czech Republic (36), from 1961 to 1995, the prevalence rate of renal agenesis was 0.17:1,000, a rate that included affected fetuses diagnosed prenatally and terminated electively. In Boston, in the years 1972–1974 and 1979–2000, the prevalence rate of bilateral renal agenesis was 0.33:1,000 or 1:2,946 (Table 20-1).

Pediatricians performing deep abdominal palpation in the first day of life in routine examinations of 12,160 consecutive newborns showed that several types of renal anomalies could be identified accurately (37). Three of these newborns were confirmed to have unilateral renal agenesis, for a prevalence rate of 1:4, 053 or 0.25/1,000.


An increased frequency (OR 2.2; 95CI 1.3–4.0) in black infants in comparison to white infants was noted in Colorado (13). However, in California [39] (1989–1998), the frequency of renal agenesis in infants born to African American parents was the same as for white infants. The frequency among U.S.-born Hispanic infants was increased marginally (Adjusted Relative Risk 1.2; 95CI 1.0–1.5).

Birth Status

Infants with BRA/D are often growth-restricted, stillborn, and in a breech presentation with associated oligohydramnios.

Sex Ratio

More affected males than females have been reported in several case series (7, 10, 11, 13) of infants with bilateral renal agenesis or agenesis/dysgenesis.


Absence of the left kidney was present in 56.4% of patients with unilateral renal agenesis and the right kidney in 43.6% in a literature review of 1,498 patients (38).

Parental Age

In a case-control study of infants born with renal agenesis, in Colorado (1989–1998), which did not distinguish between unilateral and bilateral renal agenesis, there were significantly more mothers 18 or younger whose infants had renal agenesis (13).


Reported monozygous twins with bilateral renal agenesis have been concordant (40) and, more often, discordant (7, 41, 42) for bilateral renal agenesis. In some monozygous twin pairs, one infant had unilateral renal agenesis and the co-twin had bilateral agenesis/dysgenesis (43, 44). The co-twin with bilateral renal agenesis/dysgenesis did not have any of the secondary signs of the Potter Syndrome, such as lung hypoplasia and deformations of the face and extremities, because the co-twin with unilateral renal agenesis maintained a normal amount of amniotic fluid.

Genetic Factors

BRA/D has many etiologies (Table 20-1). Among the infants with only BRA/D and anatomically adjacent anomalies, an empiric risk of about 4% of having a second affected child was established in family studies (7, 9, 11). In some families in which one parent has unilateral renal agenesis and the affected child has BRA/D (9, 45), autosomal dominant inheritance has been postulated.

Autosomal recessive inheritance has been postulated in rare consanguineous families with two or more affected infants (46).

Multifactorial inheritance also has been postulated (7, 11). The affected close relatives may have BRA/D or unilateral renal agenesis. Consistent with this hypothesis, in one case series (9), the parents with two or more affected infants had a high frequency of associated “silent” renal anomalies, but this was not the case in another publication-based study (11).

Chromosome abnormalities have been identified usually in less than 10% of infants with BRA/D, but no specific abnormalities have been common (6–13; Table 20-1). Bilateral renal dysplasia with no renal structures, but with both ureters present, has been associated with a de novo translocation (1;2) (q32;p25) [47]. Deletions involving 1q31-32 have been reported in association with bilateral (48) and unilateral (49) renal agenesis in addition to other anomalies.

The REN gene maps to 1q32 and encodes renin, a component of the renin-angiotensin system (RAS). Two other more frequent deletions identified have been 5q32-35 and 16q22 (48). Congenital anomalies of the kidney and urinary tract (CAKUT), including vesico-ureteral reflux, have been associated with deletions of chromosome 13q33-34, in children with developmental delay and other anomalies, but not renal agenesis (50).

There are many multiple anomaly syndromes that include renal agenesis, dysplasia, and hypoplasia as part of the Potter's Syndrome phenotype (Table 20-1). Mutations have been identified in a few of these. For example, a mutation in the PAX2 gene, specifically a deletion of a single nucleotide in exon 5, was identified in one family with an autosomal dominant phenotype that included optic nerve colobomas, renal hypoplasia, proteinuria, and vesicoureteral reflex (51). Another example is the association of EYA1 mutations with the Branchio-Oto-Renal (BOR) Syndrome (MIM #113650), an autosomal dominant disorder that includes renal agenesis and other renal anomalies (52).

Environmental Factors

Among infants of diabetic mothers, renal anomalies, including BRA/D (Table 20-1), are one of the major malformations that are significantly more common than in infants of nondiabetic mothers (36). A 15-fold increase (odds ratio 14.8; 95 CI 3.5–62.1) was identified in one study in Hungary (53).

Renal agenesis was an occasional component of the thalidomide embryopathy (54). Indomethacin has been postulated (55) to be a potential cause of BRA/D, but this has not been confirmed in a large, systematic study.

Treatment and Prognosis

Since BRA/D is associated with a significant degree of oligohydramnios, it is typically fatal in the newborn period. However, theoretically if the affected infant has adequate lung development, it would be possible to use renal dialysis and, later, transplantation of a kidney, to prolong survival.

Genetic Counseling

Because of the significant frequency of associated chromosome abnormalities, the index case should have had these studies. The physical examination will identify significant features of rare phenotypes, such as cryptophthalmos (MIM 21900) or Branchio-Oto-Renal (BOR) Syndrome (MIM #113650).

Case series have shown that some infants with bilateral renal aplasia/dysplasia have absence of the ureters. There can also be other related anomalies of Müllerian duct derivatives, e.g., bicornuate uterus, and Wolffian duct derivatives, e.g., congenital absence of vas deferens. Family studies are needed to determine whether or not the empiric recurrence risk of another affected fetus in the next pregnancy is changed by the presence/absence of associated genitourinary anomalies. Meanwhile, the current empiric risk estimate for bilateral renal agenesis or severe dysgenesis is 4%, based on the risk estimates in three separate family studies in which the rates were 3.5% (9), 3.6% (11), and 4.4% (5), respectively.

Prenatal screening by ultrasound has been used successfully to identify the affected fetus by 16 weeks gestation, by which time urine should be present in the bladder (6). The prenatal ultrasound studies are made more difficult by the associated oligohydiamnios; false positive findings have been reported (56). The sonologist can also look for the characteristic “flattened” adrenal gland (57) and, by color flow imaging, absence of the renal arteries (58).

If the diagnosis of “Potter's Syndrome” is based on findings by prenatal ultrasound, it is essential to establish the nature of the presumed kidney abnormalities by autopsy. Experience in a series of 60 fetuses with Potter's Syndrome showed that 50% did not have any renal anomalies (59).

Family studies (9) have also shown that the parents and sibs of an infant with bilateral renal agenesis/dysgenesis have a risk of about 10% of having “silent” renal anomalies or in females, anomalies of the fallopian tube or uterus. The frequency of unilateral absence of the vas deferens in the father and brothers has not been determined.

Because of the relationship between bilateral renal agenesis/dysgenesis and unilateral renal agenesis/dysgenesis, the healthy man or woman with unilateral renal agenesis/dysgenesis should be counseled about a significant risk of either phenotype in her/his offspring. He/she should be evaluated carefully to make certain the single kidney is healthy, as there can be obstructive lesions, like uretero-pelvic junction structure, and associated hypertension (60).

Unilateral multicystic kidney dysplasia can appear to be unilateral renal agenesis by the end of pregnancy. Close relatives of infants with bilateral renal agenesis/dysgenesis have been found to have unilateral multicystic dysplastic kidney (9). More extensive family studies are needed to confirm and establish the genetic relationship between the multicystic dysplastic kidneys and agenesis/severe dysgenesis (61).


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