Abdominal CT: cholecystitis

Imaging cholecystitis

Cholecystitis is inflammation of the gallbladder commonly caused by an obstruction of the cystic duct by a gallstone. Clinically it typically presents with right upper quadrant pain, elevated biliary enzymes and an elevated white blood cell count

Ultrasound is often the first study done for right upper quadrant pain and it is great at looking for gallstones.

CT abdomen cholecystitis ultrasound

Even though ultrasound is the preferred imaging study for diagnosing acute cholecystitis, it is not uncommon to encounter this condition on CT. This is because acute cholecystitis can mimic other causes of abdominal pain.

The good news is that CT is quite good at making this diagnosis. On CT, the normal gallbladder has a thin wall with clean, dark fat surrounding it, and it looks like it is filled with fluid.

CT abdomen normal gallbladder

It is fairly common to encounter gallstones on CT, particularly when they are calcified and have a bright appearance. Here are some examples of gallstones of various sizes and number.

CT abdomen gallstones

Key findings

When diagnosing acute cholecystitis, there are three key CT imaging findings

  • Dilated gallbladder
  • Thick, irregular gallbladder wall
  • Stranding and fluid

Dilated gallbladder When the gallbladder is obstructed, it dilates, and it will look like an inflated balloon compared to the normal gallbladder.

CT abdomen cholecystitis dilated gallbladder

Thick, irregular gallbladder wall The gallbladder wall will become thick and is often irregular when inflammation is present. The normal gallbladder wall is a thin, bright line in comparison.

CT abdomen cholecystitis irregular wall

Stranding and fluid Acute cholecystitis will result in fluid and stranding of the surrounding fat due to inflammation.

CT abdomen cholecystitis stranding

Knowledge iteration

Scroll through these PACS viewer images

  • Scroll down to the gallbladder.
  • The first thing you’ll notice is that the gallbladder is elongated and dilated. There is also subtle stranding near the gallbladder neck, and the fundus is displacing the adjacent hepatic flexure inferiorly.
  • Notice how the gallbladder pushes against the anterior abdominal wall, slightly indenting it. What does that tell us about the gallbladder?
  • The gallbladder must be quite firm to indent the abdominal wall rather than conforming to it, and that can only happen if the gallbladder is obstructed and under pressure. This is called the tensile fundus sign.
  • The tensile fundus sign, along with the surrounding stranding and inflammation, can help us confidently make the diagnosis of acute cholecystitis.

This is an edited excerpt from the Medmastery course Abdominal CT Pathologies by Michael P. Hartung, MD. Acknowledgement and attribution to Medmastery for providing course transcripts


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Assistant Professor of Abdominal Imaging and Intervention at the University of Wisconsin Madison School of Medicine and Public Health. Interests include resident and medical student education, incorporating the latest technology for teaching radiology. I am also active as a volunteer teleradiologist for hospitals in Peru and Kenya. | Medmastery | Radiopaedia | Website | Twitter | LinkedIn | Scopus 

BA MA (Oxon) MBChB (Edin) FACEM FFSEM. Emergency physician, Sir Charles Gairdner Hospital.  Passion for rugby; medical history; medical education; and asynchronous learning #FOAMed evangelist. Co-founder and CTO of Life in the Fast lane | Eponyms | Books | Twitter |

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