Absent fetal gallbladder

Absent fetal gallbladder (AFGB) is an uncommon prenatal ultrasound finding. Its significance ranges from a completely normal variant with excellent outcome to a marker of serious genetic, biliary, or syndromic disease. Prognosis depends largely on whether it is isolated or associated with other abnormalities.

Definition
The fetal gallbladder is usually visible on ultrasound from about 14–16 weeks onward as a small anechoic elongated structure in the right upper abdomen.
A diagnosis of "absent fetal gallbladder" should be made cautiously because:
• The gallbladder can intermittently contract and become temporarily invisible.
• Visualization depends on fetal position, gestational age, maternal habitus, and operator experience.
Therefore, non-visualization on a single scan is not equivalent to true agenesis.

Differential Diagnosis

1. Physiologic non-visualization (most common)
The gallbladder is present but not seen due to:
• Fetal position
• Gallbladder contraction
• Technical limitations

Many such cases become visible on repeat scans.

2. Isolated gallbladder agenesis
True congenital absence of the gallbladder.
Postnatal outcome is usually excellent.

3. Cystic fibrosis
• Thick biliary secretions
• Gallbladder hypoplasia
• Gallbladder non-visualization
Risk is particularly increased when:
• Echogenic bowel is present
• Family history exists
• Both parents carry CFTR variants

4. Biliary atresia
Prenatally:
• Gallbladder may be absent or very small.
• Liver usually appears normal.
Postnatally:
• Persistent jaundice
• Pale stools
• Progressive liver damage

Early diagnosis is critical because surgery before 60 days improves outcomes.

5. Chromosomal abnormalities
• Trisomy 21, Trisomy 18, Trisomy 13

Genetic Associations
CFTR-related disease
Most important single-gene association.
Gene:
• CFTR
Can present with:
• Absent gallbladder
• Echogenic bowel
• Meconium ileus
If absent gallbladder coexists with echogenic bowel, CFTR analysis is often recommended.
Ciliopathies
Occasionally associated with:
• Joubert syndrome
• Meckel syndrome
Usually accompanied by:
• Renal abnormalities
• CNS abnormalities
• Polydactyly

HNF1B-related disorders
Gene:
• HNF1B
Can produce:
• Biliary anomalies
• Renal abnormalities
• Diabetes predisposition
Look carefully for:
• Echogenic kidneys
• Renal cysts
Alagille syndrome
Gene:
• JAG1
• NOTCH2
Features:
• Bile duct paucity
• Cardiac defects
• Characteristic facies

1. EHBA (Extrahepatic Biliary Atresia)
Also called:
• Biliary Atresia
Pathology
Progressive obliteration of the extrahepatic bile ducts leading to:
• Cholestasis
• Fibrosis
• Cirrhosis

Prenatal Ultrasound Findings
Unfortunately, prenatal diagnosis is difficult because many fetuses appear normal.
Possible findings:
• Absent or very small gallbladder
• Irregular gallbladder
• Enlarged hepatic artery (occasionally)
• Cyst at porta hepatis (cystic biliary atresia subtype)

Most fetuses with EHBA have otherwise normal anatomy.
Genetics
Unlike many fetal anomalies, classic EHBA is usually not a monogenic genetic disorder.
Most cases are considered:
• Sporadic
• Multifactorial
Rare associations:
• Laterality defects
• Heterotaxy
• Ciliary dysfunction genes

Prognosis
Depends on timing of surgery.
Treatment:
• Kasai Portoenterostomy
Best outcomes when performed before ~60 days of age.
Many patients eventually require:
• Liver Transplantation

2. PFC (Progressive Familial Intrahepatic Cholestasis)
Usually abbreviated PFIC, not PFC.
Definition
A group of inherited disorders causing defective bile secretion.
PFIC Type Associated Gene PFIC1 ATP8B1 PFIC2 ABCB11 PFIC3 ABCB4 PFIC4 TJP2 PFIC5 NR1H4 PFIC6 MYO5B

These are typically autosomal recessive disorders.
Prenatal Ultrasound
Most fetuses show:
• Normal anatomy
• Normal gallbladder
Therefore PFIC is not a common cause of absent fetal gallbladder.
Rarely:
• Small gallbladder
• Biliary abnormalities
may be reported.

Postnatal Presentation
• Neonatal cholestasis
• Jaundice
• Severe pruritus
• Elevated bile acids
Prognosis
Highly variable:
• Some respond to medication
• Some require biliary diversion surgery
• Some ultimately need liver transplantation

HBA vs PFIC in a Fetus with Absent Gallbladder

Prognosis
Isolated absent fetal gallbladder
Generally excellent.
Outcomes include:

Gallbladder later visualized
Most favorable scenario.
True gallbladder agenesis
Usually normal childhood and adult life.
Small proportion diagnosed with biliary disease
Minority of cases.
Overall prognosis is usually very good.

What exome can do
Exome may identify a syndrome that includes biliary abnormalities, such as:
• Alagille Syndrome
• HNF1B-related disorders
• Certain ciliopathies
• Some laterality/heterotaxy syndromes
• Rare cholestatic disorders (including some PFIC-related genes)
If the fetus has:
• Absent gallbladder plus
• Cardiac anomalies
• Renal anomalies
• Heterotaxy
• Growth abnormalities
• Other structural findings

What a normal exome means
Suppose you have:
• Persistently absent gallbladder
• Otherwise normal anatomy
• Normal microarray
• Normal exome

A normal exome makes syndromic genetic causes less likely, which is reassuring.
However, it does not reliably exclude:
• Biliary atresia
• Isolated gallbladder agenesis
• Many non-genetic causes of neonatal cholestasis
Therefore, the post-test probability shifts toward:
1. Normal variant/gallbladder seen later
2. Isolated gallbladder agenesis
3. Less commonly, biliary atresia
rather than toward a major genetic syndrome.