Micro gallbladder

First published on SonoWorld

CASE PRESENTATION:
A 22 year old man with history of cystic fibrosis presents with right upper quadrant pain. An abdominal ultrasound was performed.

Differential Diagnosis

Micro gallbladder due to cystic fibrosis

Final Diagnosis

Micro gallbladder due to cystic fibrosis

Discussion

Micro gallbladder is defined as less than 2-3 cm long and 0.5 -1.5 cm wide. Micro gallbladder can be seen most commonly in cystic fibrosis but is also seen in idiopathic neonatal hepatitis and alpha-1-antitrypsin deficiency. 

In cystic fibrosis, which is a hereditary condition, there is abnormal production of thick viscid mucus by the affected glands. According to two studies by Jebbink, et al and by Strandvik, et al; liver and gallbladder abnormalities are quite common in patients with cystic fibrosis.  Noteworthy amongst these complications are- 

1. Fatty infiltration of the liver 
2. Liver fibrosis 
3. Cirrhosis 
4. Cholelithiasis 
5. Micro- gallbladder and 
6. Sclerosing cholangitis.

The exact pathogenetic mechanism of biliary complications in cystic fibrosis is not well understood. Cystic fibrosis occurs due to mutations in the gene for the cystic fibrosis transmembrane conductance regulator channel [the CFTR gene]. In the liver, the CFTR is located in the biliary epithelial cells and appears to be responsible for normal bile formation. Therefore, a defective CFTR channel in cystic fibrosis is responsible for the liver and biliary abnormalities. Jebbink, et al suggested the following meachanism for gallbladder disease:

1. abnormalities in bile acid metabolism, resulting in bile that is supersaturated with cholesterol
2. bile duct stasis due to bile duct abnormalities and/ or impaired gallbladder motility
3. impaired nucleation time

Ultrasound is diagnostic and shows a small contracted gallbladder in cases of micro gallbladder. A micro-gallbladder may provide a clue to the diagnosis of cystic fibrosis.