Review Question - QID 106475

This child has Potter's syndrome, which is defined by the characteristic dysmorphic appearance of a neonate secondary to oligohydramnios during fetal development. The most common cause of Potter's syndrome is bilateral renal agenesis.

Any cause of oligohydramnios can lead to Potter's syndrome. The amniotic fluid index (AFI) is an estimate of the amount of amniotic fluid as measured with ultrasound. A normal AFI is between 8-18 and anything less than 5-6 is consistent with oligohydramnios. While bilateral renal agenesis is the most common cause, it can also be caused by renal hypoplasia, urinary tract obstruction, and polycystic kidney disease. Amniotic fluid acts as a cushion for the growing fetus within the uterus. Oligohydramnios reduces this cushioning effect and leads to facial compression resulting in these characteristic dysmorphic features (i.e epicanthal folds, low-set ears that are pressed against his head, widely set eyes, a broad, flat nose, clubbed fleet, and a receding chin). Potter's syndrome is also classically associated with pulmonary hypoplasia and clubbed feet. Bilateral renal agenesis is rare, occurring in 0.1/1,000 births, and prognosis is dismal, as bilateral renal agenesis is incompatible with life.

Weismiller reviews the use of transcervical amnioinfusion as a prophylactic treatment of oligohydramnios, as well as other disorders. This procedure is performed by infusing amniotic fluid into the amniotic cavity. This technique has been shown to be beneficial in the treatment of both variable decelerations (by cushioning the umbilical cord) and thick meconium (diluting effect).

Mercado-Deane et al. discuss the ultrasound findings of renal insufficiency in neonates. They introduce the etiology of bilateral renal agenesis as a vascular insult to the ureteral bud. They describe the common craniofacial findings, as well as other associated abnormalities, such as cardiovascular, anorectal, genital, and skeletal anomalies. Common sonographic findings of bilateral renal agenesis include the absence of kidneys and renal arteries, malformed adrenal glands, and a hypoplastic bladder.

Illustration A: A lateral picture of a child with Potter's syndrome. Note the characteristic facial abnormalities (low set ears pressed against head, flat nose, receding chin).

Incorrect Answers:
Answer 1: Trisomy 18, or Edwards syndrome, manifests with a variety of birth defects, including renal malformation, heart defects, club feet, microcephaly, cleft lip/palate, etc. This presentation is more consistent with Potter's syndrome.
Answer 3: ARPKD is another cause of oligohydramnios and pulmonary hypoplasia, but it is a less common cause than bilateral renal agenesis.
Answer 4: Unilateral renal agenesis is generally clinically silent and is often found incidentally later in life.
Answer 5: DiGeorge syndrome has a characteristic presentation that is remembered by the mnemonic CATCH-22: Cardiac abnormality, abnormal facies, thymic aplasia, cleft palate, hypocalcemia/hypoparathyroidism.