Hydrops

Paula J. Woodward, MD

DIFFERENTIAL DIAGNOSIS

Common

Nonimmune Hydrops
- Idiopathic
- Cardiac
  - Structural Cardiac Defect
  - Tachyarrhythmia
  - Bradyarrhythmia
- Fetal Masses
  - Hemangioendothelioma
  - Teratoma
  - Vascular Malformations
- Placental Chorioangioma
- Chromosome Abnormalities
  - Turner Syndrome (XO)
  - Trisomy 21
- Twin-Twin Transfusion Syndrome
- Infection
Immune Hydrops
- Rh Incompatibility
- Other Antibodies

ESSENTIAL INFORMATION

Key Differential Diagnosis Issues

Defined as fluid accumulation in 2 or more body cavities
- Skin/subcutaneous edema
  - Scalp edema often first sign
- Ascites
- Bilateral pleural effusions
- Pericardial effusion
- Other findings
  - Placentomegaly (placenta thickness > 40 mm)
  - Polyhydramnios
  - Hepatosplenomegaly
Broadly classified as immune (hemolytic disease → fetal anemia) and nonimmune (all others)
- 90% are nonimmune hydrops
- 10% immune

Helpful Clues for Common Diagnoses

Idiopathic
- Over 50% of cases will not have an identifiable cause
Structural Cardiac Defect
- Poor contractility → heart failure → hydrops
- May be accompanied by bradycardia
Tachyarrhythmia
- Sustained heart rate > 200 bpm
- Supraventricular tachycardia (SVT) most common cause
- Hydrops develops in 50-75% fetuses with sustained tachycardia
- Increased risk of ischemic brain injury when hydrops is present
Bradyarrhythmia
- 50% associated with cardiac malformation, particularly atrioventricular septal defects
- 50% of cases seen in mothers with connective tissue disease
- Increased mortality with heart rate < 50 bpm
Fetal Masses
- Any mass causing increased cardiac output may lead to failure and hydrops
  - Teratomas and vascular malformations most common
  - Hemangioendothelioma may cause hemolytic anemia in addition to arteriovenous shunting
- Chest masses may also impede cardiac return
Placental Chorioangioma
- Benign, vascular placental tumor
- Fetal hydrops from arteriovenous shunting or from fetal anemia secondary to hemolysis
  - Hydrops uncommon if mass is < 5 cm
- Polyhydramnios common with large masses
Turner Syndrome (XO)
- Female fetus with large, septated cystic hygroma
  - Failed or delayed connection between internal jugular veins and nuchal lymph sacs
- Hydrops secondary to fluid overload from lymphatic obstruction
  - Edema is diffuse and may be dramatic
  - Dorsal pedal edema prominent feature
- Hydrops can be seen in first trimester
- Prognosis with hydrops is dismal
Trisomy 21
- Small cystic hygroma (increased nuchal translucency in 1st trimester) becomes nuchal thickening in 2nd trimester
- May present with hydrops
- Other markers often seen
Twin-Twin Transfusion Syndrome
- Monochorionic twins with artery-to-vein anastomoses in the placenta
- Recipient at risk for hydrops
  - Larger twin with polyhydramnios
- Donor at risk for growth restriction
  - Smaller twin with oligohydramnios
- Twin-twin transfusion syndrome (TTTS) staging
  - Stage 1: Donor bladder visible, normal Doppler
  - Stage 2: Donor bladder empty, normal Doppler
  - Stage 3: Donor bladder empty, abnormal Doppler
  - Stage 4: Hydrops in recipient
  - Stage 5: Demise of one or both
Infection
- Parvovirus most common but can occur with any severe infection
- Infection → anemia, myocarditis
- Look for other signs of infection
  - Intracranial and liver calcifications, ventriculomegaly, hepatosplenomegaly, echogenic bowel, growth restriction
Immune Hydrops
- Maternal antibodies cross placenta and cause lysis of fetal red blood cells, leading to fetal anemia
- Anemia causes an elevated middle cerebral artery (MCA) peak systolic velocity (PSV)
- Need for intervention (transfusion) generally based on relationship of MCA PSV to gestational age
- Rh Incompatibility
  - Maternal lack of D antigen on erythrocyte membrane (Rh -)
  - Sensitization 2° to fetal-maternal hemorrhage
  - Fetal D antigen causes maternal antibody response (< 1 cc fetal cells can lead to anti-D antibody response)
  - With subsequent pregnancy, maternal antibodies attack fetal red blood cells
  - Leads to lysis of fetal erythrocytes
  - Causes anemia and may progress to hydrops if left untreated
- Other Antibodies
  - Non-D antigen causes alloimmunization (usually from incompatible blood transfusion)
  - Kell, Duffy, Kidd, E, C, c, and others
  - Most are variably present in different ethnic populations

Other Essential Information

First trimester hydrops highly associated with aneuploidy
- Turner, trisomy 21 most common
Nonimmune hydrops
- Over 50% have no unifying diagnosis or directly identifiable cause
- 22% have a cardiac defect
- 16% have aneuploidy
  - Turner syndrome > trisomy 21
  - Trisomy 18 and 13 less likely to present with hydrops (growth restriction more common)

Image Gallery

Axial color Doppler ultrasound of the pelvis shows ascites

on either side of the bladder

, which is flanked by the umbilical arteries (skin edema

). No obvious etiology was found for the hydrops.

Sagittal ultrasound in the same case shows marked scalp and face edema

. The scalp is one of the first places to see skin edema. This fetus died in utero with no unifying diagnosis found at autopsy.

Image Gallery

(Left) Coronal T2WI MR shows the typical MR findings of hydrops including high-signal skin edema

, pleural effusions

, and ascites

. Hydrops resulted from poor cardiac return secondary to ectopia cordis (seen on other images). (Right) Four chamber view shows both a ventricular septal defect