Potter Sequence vs. Potter Syndrome: Key Distinctions
Potter sequence and Potter syndrome are distinct entities: Potter sequence refers to the constellation of findings (pulmonary hypoplasia, characteristic facies, limb deformities) that result from severe oligohydramnios from any cause, while Potter syndrome (classic Potter syndrome) specifically refers to bilateral renal agenesis as the underlying etiology.
Defining Potter Sequence
Potter sequence is a mechanically-derived pattern of multiple anomalies initiated by a single factor: severe oligohydramnios 1. The sequence includes:
- Pulmonary hypoplasia - the most life-threatening component, causing respiratory distress incompatible with life 1, 2
- Characteristic facial features - flattened nose, low-set ears, recessed chin 1, 3
- Limb abnormalities - positional deformities from compression 1
- Oligohydramnios or virtual absence of amniotic fluid - the initiating mechanical factor 1, 3
The critical concept is that Potter sequence develops from oligohydramnios regardless of the underlying cause 2. Multiple etiologies can trigger this sequence 2:
- Bilateral renal agenesis (true Potter syndrome)
- Renal cystic dysplasia 4, 2
- Obstructive uropathies (posterior urethral valves) 2
- Polycystic kidney disease 4
- Premature rupture of membranes 4
Defining Potter Syndrome (Classic)
Potter syndrome specifically denotes bilateral renal agenesis (BRA) with its associated findings 1, 3. This is:
- A rare congenital defect where complete absence of both kidneys causes the Potter sequence 1
- Incompatible with life in the neonate 1
- Possibly autosomal recessive in familial cases, though most cases develop sporadically 1
- Associated with oligohydramnios because fetal urine production (which normally contributes to amniotic fluid) is absent 3
Clinical Implications
Prenatal Diagnosis
- Ultrasound scanning in the second trimester can diagnose bilateral renal agenesis by demonstrating absent kidneys and severe oligohydramnios 1, 3
- Serial ultrasonography with clinical observation allows prenatal diagnosis in at-risk fetuses 3
- Early diagnosis is critical to avoid unnecessary cesarean sections, as these pregnancies frequently present with premature labor and breech presentation 1
Differential Diagnosis of Oligohydramnios
When evaluating severe oligohydramnios, consider:
- Bilateral renal agenesis (true Potter syndrome) 1, 3
- Renal cystic dysplasia - can present identically to bilateral renal agenesis 2
- Obstructive uropathy - portable voiding cystourethrography reveals tiny bladder, possible vesicoureteral reflux, or bladder hypertrophy with posterior urethral valves 2
- Bartter syndrome - causes the opposite problem (polyhydramnios from excessive fetal polyuria), not oligohydramnios 5, 6
Important Pitfall
Do not confuse Potter sequence with conditions causing polyhydramnios. Bartter syndrome virtually always causes polyhydramnios when severe fetal polyuria occurs, with no reports of inherited tubular disorders causing severe oligohydramnios 5, 6. If polyhydramnios is present with renal abnormalities, consider Bartter syndrome types 1,2, 4a, or 4b 5, 6.
Postnatal Evaluation
In neonates with respiratory distress and suspected Potter sequence:
- Portable voiding cystourethrography can identify the underlying renal pathology (tiny bladder in cystic dysplasia, reflux, or obstructive valves) 2
- Clinical signs of renal nonfunction syndrome may be subtle and only noted at autopsy if not actively investigated 2
- The underlying renal disease determines whether the condition is Potter syndrome (bilateral renal agenesis) or Potter sequence from another cause 2
Terminology Summary
Use "Potter sequence" when describing the phenotypic constellation resulting from oligohydramnios of any etiology 1, 2. Reserve "Potter syndrome" for cases specifically caused by bilateral renal agenesis 1, 3. This distinction matters for genetic counseling, recurrence risk assessment, and accurate medical documentation.