What is Gb (Gallbladder) hydrops, also known as hydrops fetalis, in pregnant women?

What is Gallbladder Hydrops (Hydrops Fetalis)

The term "GB hydrops" in obstetrics refers to hydrops fetalis, a serious fetal condition characterized by abnormal fluid accumulation in two or more extravascular fetal compartments (ascites, pleural effusion, pericardial effusion, and/or skin edema), not gallbladder pathology. 1, 2

Definition and Classification

Hydrops fetalis represents the final common pathway of numerous pathological conditions affecting the fetus. 3 The diagnosis is made ultrasonographically when fluid accumulation is detected in at least two fetal body compartments, which may include: 1, 4

• Peritoneal cavity (ascites)
• Pleural space (pleural effusion)
• Pericardial space (pericardial effusion)
• Subcutaneous tissue (skin edema/anasarca)

The condition is classified into two categories based on etiology: 1, 5

• Immune hydrops: Caused by maternal antibodies against fetal red blood cells (historically Rh alloimmunization)
• Non-immune hydrops fetalis (NIHF): All other causes, which now account for over 90% of cases 1, 5

Common Etiologies of Non-Immune Hydrops Fetalis

The Society for Maternal-Fetal Medicine identifies multiple categories of causes: 1, 6

Cardiovascular Abnormalities (17-35%)

• Structural cardiac defects
• Cardiac arrhythmias (tachyarrhythmias and bradyarrhythmias)
• High-output cardiac failure 1, 6

Chromosomal Abnormalities (7-16%)

• Turner syndrome (45,X) - most common, associated with cystic hygromas
• Trisomy 21 (Down syndrome)
• Trisomies 13 and 18 1, 6

Hematologic Disorders (4-12%)

• Alpha thalassemia (accounts for 28-55% in Southeast Asian populations)
• Fetal anemia from fetomaternal hemorrhage
• G-6-PD deficiency
• Red cell enzymopathies 1, 6

Infectious Causes (5-7%)

• Parvovirus B19 (most common infectious cause)
• Cytomegalovirus
• Toxoplasmosis
• Syphilis 1, 6, 4

Thoracic Abnormalities (6%)

• Congenital pulmonary airway malformation (CPAM)
• Congenital hydrothorax/chylothorax
• Bronchopulmonary sequestration 1, 6

Twin Complications (3-10%)

• Twin-twin transfusion syndrome
• Twin-reversed arterial perfusion sequence 1, 6

Other Causes

• Lymphatic dysplasia (5-6%)
• Tumors including chorioangiomas (2-3%)
• Skeletal dysplasias (3-4%)
• Inborn errors of metabolism (1-2%)
• Idiopathic (15-25% remain unexplained) 1, 6

Pathophysiology

The mechanisms leading to hydrops vary by etiology but include: 1, 7

• Impaired venous return and increased central venous pressure
• High-output cardiac failure from arteriovenous shunting
• Hypoproteinemia from liver dysfunction or protein loss
• Severe fetal anemia causing tissue hypoxia
• Lymphatic obstruction or dysplasia
• Increased capillary permeability from infection or inflammation 1

Clinical Significance and Prognosis

The prognosis of hydrops fetalis is generally poor, with overall neonatal survival often less than 50% even in the absence of chromosomal abnormalities. 6, 8 Outcomes depend heavily on: 6, 8

• Underlying etiology: Cardiac structural abnormalities have 92% combined fetal and infant mortality, while isolated chylothorax may have mortality as low as 6% 6
• Gestational age at diagnosis: Younger gestational age is an independent predictor of mortality 6, 8
• Treatability: Conditions like fetal tachyarrhythmias, parvovirus-induced anemia, and pleural effusions have better outcomes with intervention 1, 6, 8

Associated Maternal Complications

Mirror syndrome (Ballantyne syndrome) is a critical maternal complication where the mother develops preeclampsia-like symptoms (edema, hypertension, proteinuria) mirroring the fetal hydrops. 8, 7 This condition necessitates delivery in most cases and requires serial maternal blood pressure monitoring throughout the pregnancy. 8, 7