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True BRA also presents with bilateral agenesis of the ureters. After the creation of the nomenclature system for this sequence, BRA was recognized as possibly being an extreme variation of Potter sequence II. However, some clinicians and researchers still use the term classic Potter sequence so as to emphasize that they are specifically referring to cases of BRA and not another form.
Type I Type I is due to autosomal recessive polycystic kidney disease ARPKD , which occurs at a frequency of approximately one in 16, infants. Type II Type II is usually due to renal agenesis ,  which can also fall under the category known as hereditary urogenital adysplasia or hereditary renal adysplasia HRA.
This is characterized by the complete agenesis or absence of one kidney and the remaining solitary kidney being small and malformed. Bilateral renal agenesis is believed to be the most extreme phenotypic variation of HRA.
However, BRA is often referred to as classic Potter sequence, as it was this particular phenotype of neonates and fetuses that Potter originally reported in her manuscripts when characterizing this birth defect. While ADPKD is considered to be an adult-onset polycytic kidney disease, it can also present in the fetus and neonate in rare cases. This can be due to chance, environment, or genetics. While these types of obstructions occur frequently in fetuses, they rarely tend to lead to fetal demise.
Others Often cystic kidneys that do not fall under the classification of being polycystic will be termed as being multicystic renal dysplasia MRD.
Recently many cases of MRD have been linked to the mutations in the gene PUJO, however, this new possible genetic cause has not been assigned a Potter sequence nomenclature number. Another cause of Potter sequence oligohydramnios or anhydramnios—little or no amniotic fluid can be the rupturing of the amniotic sacs that contain the amniotic fluid of the fetus.
This can happen spontaneously, by chance, environment, maternal trauma and in rare cases - maternal genetics. Signs and symptoms[ edit ] The failure of the metanephros to develop in cases of BRA and some cases involving unilateral renal agenesis URA is due primarily to the failure of the mesonephric duct to produce a ureteric bud capable of inducing the metanephric mesenchyme.
The failed induction will thereby cause the subsequent degeneration of the metanephros by apoptosis and other mechanisms. The mesonephric duct s of the agenic kidney s will also degenerate and fail to connect with the bladder.
Therefore, the means by which the fetus produces urine and transports it to the bladder for excretion into the amniotic sac has been severely compromised in the cases of URA , or completely eliminated in the cases of BRA. This compression can cause many physical deformities of the fetus , most common of which is Potter facies. Sirenomelia , or "Mermaid syndrome" which occurs approximately in , births  can also present.
In fact, nearly all reported cases of sirenomelia also present with BRA. The ears are slightly low and pressed against the head making them appear large. The adrenal glands often appear as small oval discs pressed against the posterior abdomen due to the absence of upward renal pressure.
The bladder is often small, nondistensible and may be filled with a minute amount of fluid. In males the vas deferens and seminal vesicles may be absent, while in females the uterus and upper vagina may be absent. Other abnormalities include anal atresia, absence of the rectum and sigmoid colon , esophageal and duodenal atresia , and a single umbilical artery.
Additionally, the alveolar sacs of the lungs fail to properly develop as a result of the reduced volume of amniotic fluid. Labor is often induced between 22 and 36 weeks of gestation however, some of these pregnancies may go to term and unaborted infants typically survive for only a few minutes to a few hours.
These infants will eventually die as either a result of pulmonary hypoplasia or renal failure. Further information: Oligohydramnios The Potter sequence is due to restricted ability for certain organs to grow due to severe oligohydramnios. In one study, the causes leading to Potter sequence were bilateral renal agenesis in However, recent analysis has estimated that the condition may occur at a much greater frequency. The condition has been reported to occur twice as commonly in males as in females, suggesting that certain genes of the Y chromosome may act as modifiers.
However, no candidate genes on the Y chromosome have yet been identified. BRA appears to have a predominantly genetic etiology and many cases represent the most severe manifestation of an autosomal dominant condition with incomplete penetrance and variable expressivity. There are several genetic pathways that could result in this condition.
The majority of other possible candidate genetic pathways are autosomal recessive in nature and do not coincide with the frequency or penetrance at which BRA typically occurs in the human population. Additionally, candidate genetic pathways would be expected to involve genes expressed in the developing urogenital system UGS. Pathogenesis[ edit ] Development of the mature kidney begins between weeks 5 and 7 of gestation. Fetal urine production begins in early gestation and comprises the majority of the amniotic fluid in the second and third trimesters of pregnancy.
The fetus continuously swallows amniotic fluid, which is reabsorbed by the gastrointestinal tract and then reintroduced into the amniotic cavity by the kidneys via urination. Oligohydramnios occurs if the volume of amniotic fluid is less than normal for the corresponding period of gestation.
The fetal urine is critical to the proper development of the lungs by aiding in the expansion of the airways - alveoli , by means of hydrodynamic pressure and by also supplying proline which is a critical amino acid for lung development.
Alveoli are the small sacs in the lungs that exchange oxygen with the blood. If the alveoli, and thereby the lungs, are underdeveloped at the time of birth the infant will not be able to breathe air properly and will go into respiratory distress shortly after birth due to pulmonary hypoplasia underdeveloped lungs. This is the primary cause of death to Potter sequence infants secondary to renal failure. A series of 23 patients in recorded 7 deaths, 4 in the neonatal period.
All 16 survivors have chronic kidney disease, with half developing end stage renal failure median age 0. After Abigail was born, the procedure was considered a success. The infant did not need artificial respiration and could breathe on her own. Her parents kept her on kidney dialysis at home until old enough for a kidney transplant. Potter analyzed approximately autopsy cases performed on fetuses and newborn infants over a period of ten years and found that 20 of these infants presented with BRA, all of which had distinctive facial characteristics which did not appear to them to have any specific embryologic correlation with the renal anomaly.
It is more accurately described as a "sequence" or chain of events that may have different beginnings absent kidneys , cystic kidneys , obstructed ureters or other causes , but which all end with the same conclusion absent or reduced volume of amniotic fluid.
This is why Potter syndrome is often called Potter sequence or oligohydramnios sequence by some clinicians and researchers. The term Potter syndrome is most frequently associated with the condition of oligohydramnios sequence regardless of the root cause of the absence or reduced volume of amniotic fluid. However, as noted in this article, the term Potter syndrome was initially coined in order to refer to fetuses and infants with BRA.
It was not until later that the term became more encompassing as it was noted that other causes of failed fetal urine production also resulted in similar physical characteristics and prognoses of the fetuses and infants with BRA that which Potter originally described in Since then, the term Potter syndrome has become a misnomer and experts have attempted not to eliminate the terminology, but to modify it in a way so as to be able to determine the different root causes by creating a nomenclature system.
However, this classification system has not caught on in the clinical and research fields.
Syndrome de Potter ou séquence: types, symptômes et causes
Séquence oligohydramnios (syndrome de Potter)
Secuencia de Potter