hydrops

Hydrops is a medical term for abnormal accumulation of fluid in tissues and body cavities. In the fetal context, hydrops fetalis refers to edema and effusions in the fetus, typically defined as fluid accumulation in at least two fetal compartments such as the peritoneal cavity (ascites), pleural or pericardial spaces, and generalized skin edema. In nonfetal contexts, hydrops describes pronounced generalized edema caused by systemic disease.

Causes of hydrops are commonly categorized as immune and nonimmune. Immune hydrops fetalis results from maternal alloimmunization against fetal red cell antigens (most frequently RhD), leading to fetal anemia, high-output cardiac failure, and fluid accumulation. Nonimmune hydrops fetalis has a wide range of etiologies, including congenital heart disease, chromosomal abnormalities, fetal infections (such as parvovirus B19, cytomegalovirus), twin-twin transfusion syndrome, metabolic disorders, and lymphatic or hepatic malformations.

Pathophysiology involves an imbalance between fluid production and clearance. Factors include decreased plasma oncotic pressure from hypoalbuminemia or liver dysfunction, increased capillary hydrostatic pressure, lymphatic obstruction, and fetal anemia with resultant heart failure. These processes promote fluid leakage into interstitial spaces and body cavities.

Diagnosis relies on imaging and laboratory evaluation. In pregnancy, fetal ultrasound can reveal edema, thickened skin, and effusions; Doppler studies assess cardiac function, and maternal antibody screening plus fetal karyotyping help determine immune versus nonimmune causes. Postnatally, diagnosis focuses on identifying the underlying cause after clinical evaluation and appropriate testing.

Management targets the underlying etiology and the clinical status of the fetus or patient. Immune hydrops may require intrauterine transfusions or timely delivery; nonimmune hydrops management depends on the cause and may involve treating structural defects, infections, or heart failure, with supportive care as needed. Prognosis varies by cause and severity, but immune hydrops historically carries higher mortality.