In an infant with gallbladder agenesis, why are the stools green-colored?

Gallbladder Agenesis and Green Stools in Infants

Direct Answer

In an infant with gallbladder agenesis, green-colored stools are actually NOT expected and would suggest a different underlying pathology—most likely cholestasis from biliary atresia or another cholestatic disorder, not the gallbladder agenesis itself.

Critical Distinction

The question appears to conflate two separate entities that require immediate clarification:

Gallbladder Agenesis

• Gallbladder agenesis is an extremely rare congenital anomaly (1 per 6,500 live births) where the gallbladder simply fails to develop 1
• 50-70% of patients with gallbladder agenesis remain completely asymptomatic throughout life 1
• The bile ducts and bile flow remain intact—bile flows directly from the liver through the common bile duct into the duodenum 2
• Stool color remains NORMAL (brown) because bile pigments still reach the intestine normally 2, 3

Green Stools in Cholestatic Infants

If an infant presents with green stools and cholestasis, you must urgently evaluate for:

• Biliary atresia—the most common cause of neonatal cholestasis and a surgical emergency requiring Kasai portoenterostomy before 60 days of age 4, 5
• Progressive familial intrahepatic cholestasis (PFIC)—characterized by low/normal GGT with conjugated hyperbilirubinemia 6
• Alpha-1 antitrypsin deficiency—presenting with prolonged jaundice and conjugated hyperbilirubinemia in 7% of PI*ZZ infants 4
• Alagille syndrome—multisystem disorder with cholestasis and characteristic facial features 4

Pathophysiology of Stool Color

Normal brown stool color results from bacterial conversion of bilirubin to stercobilin in the intestine 7

Green stools in cholestatic disease occur when:

• Conjugated bilirubin fails to reach the intestine due to bile duct obstruction or severe hepatocellular dysfunction 5
• Biliverdin (green pigment) is excreted instead of being fully converted to stercobilin 7
• This represents ACHOLIC or pale/clay-colored stools in severe cases, not truly "green"—green stools more commonly indicate rapid intestinal transit or dietary factors in healthy infants 5

Urgent Diagnostic Algorithm

If an infant presents with suspected cholestasis (jaundice beyond 2-3 weeks):

1. Immediately measure total and direct/conjugated bilirubin—this is a medical emergency 5
2. Obtain complete blood count, liver function tests, GGT level, and review newborn screening results 5
3. Refer urgently to pediatric gastroenterology/hepatology for hepatobiliary ultrasound and HIDA scan 5
4. Rule out biliary atresia FIRST, as it requires surgery before 60 days of age to prevent death 6, 5
5. If GGT is low/normal with conjugated hyperbilirubinemia, obtain genetic testing for PFIC (ABCB11, ATP8B1, ABCB4 mutations) 6

Critical Pitfall

Never assume gallbladder agenesis causes cholestasis or abnormal stool color—it does not. If cholestasis is present, another serious pathology exists that requires immediate investigation 1, 2, 3. The gallbladder is simply a storage organ; its absence does not impair bile flow to the intestine in isolated cases 2.