Potter's Syndrome--perhaps more accurately referred to as Potter's Sequence as it refers to the pathophysiologic consequences of lack of kidney function in utero--is characterized by absence of renal function, oligohydramnios, pulmonary hypoplasia, and a characteristic "Potter's facies", in which there is a flattened nose, recessed chin, prominent epicanthal folds, and low-set abnormal ears. In addition to other serious cardiovascular, ophthalmologic, and skeletal malformation, Potter's Syndrome also occurs frequently with sirenomelia (a.k.a. "mermaid syndrome", as pictured in the X-ray above.
Any form of severe renal dysfunction in utero can be the root cause of Potter's Syndrome. More common causes include bilateral renal agenesis, autosomal recessive polycystic kidney disease, and congenital obstruction/hydronephrosis. When the kidneys do not produce urine, there is oligohydramnios (since fetal urine production accounts for the majority of amniotic fluid during the 2nd and 3rd trimesters of pregnancy). Since amniotic fluid is also responsible for proper alveoli expansion, these patients commonly get pulmonary hypoplasia and potentially serious respiratory problems at birth.
The syndrome is named after pathologist Edith Potter, who initially characterized this sequence of events.