The gallbladder is a small, pear-shaped organ that sits tucked beneath the liver on your right side. In a healthy adult, it measures roughly 6 to 7 centimeters long and about 3 centimeters wide, making it similar in size to a small egg. Its job is to store and concentrate bile, a digestive fluid produced by the liver, and release it into your small intestine when you eat.
Shape, Size, and Color
Picture a small, slightly deflated pear with a greenish or blue-green tint. That color comes from the bile stored inside. The organ has a smooth outer surface and tapers from a wide, rounded bottom (called the fundus) to a narrow neck at the top, where it connects to a short tube called the cystic duct. When full of bile, the gallbladder is firm and distended. After a fatty meal triggers bile release, it contracts and appears smaller and more wrinkled.
Ultrasound studies of healthy adults show the gallbladder holds between about 21 and 38 milliliters of bile, with an average around 27 to 30 milliliters. That’s roughly two tablespoons at capacity. Men tend to have slightly larger gallbladders than women, though the difference is small.
Where It Sits in the Body
The gallbladder rests in a shallow depression on the underside of the liver’s right lobe, nestled against the organ like a small pouch. This puts it in the upper right area of your abdomen, just below the ribcage. Because it’s partially hidden behind the liver, you can’t feel it from the outside under normal conditions. If it becomes inflamed or swollen enough for a doctor to feel it during a physical exam, that itself is a sign something is wrong.
What’s Inside the Walls
The gallbladder wall is thin, only about 1 to 2 millimeters in a healthy organ. It’s made of three layers: an inner lining (mucosa), a middle layer of smooth muscle, and an outer protective coating. The inner lining has small folds that flatten out as the gallbladder fills with bile, similar to how the folds in a deflated balloon smooth out when you inflate it. These folds increase the surface area, allowing the lining to absorb water from bile and concentrate it to five or even ten times its original strength.
On imaging, a wall thickness of 3 millimeters or less is considered normal. When the wall measures more than 3.5 millimeters, it typically signals disease, most often inflammation.
How It Connects to the Digestive System
The gallbladder doesn’t work in isolation. Its narrow neck funnels into the cystic duct, a small tube that merges with the common hepatic duct (coming from the liver) to form the common bile duct. This common duct carries bile down to the first section of the small intestine. When you eat, especially something fatty, the gallbladder contracts, squeezing concentrated bile through the cystic duct, into the common bile duct, and finally into the intestine where it helps break down fats.
If you were looking at the biliary system laid out, it would resemble a small tree. The liver’s bile ducts form the branches, the common bile duct is the trunk, and the gallbladder hangs off to the side like a small reservoir connected by the cystic duct.
What It Looks Like on Ultrasound
Most people will see their gallbladder for the first time on an ultrasound image, not in person. On a standard abdominal ultrasound, a healthy gallbladder appears as a dark (nearly black), pear-shaped sac with a thin, bright white wall. The dark interior represents the liquid bile, which lets sound waves pass through easily. The bright wall stands out clearly against the surrounding liver tissue, which appears gray.
Doctors look for several things on these images: whether the wall is thin and uniform, whether the bile inside appears clear and dark, and whether any bright spots with shadows behind them suggest stones.
How Disease Changes Its Appearance
A gallbladder affected by disease looks noticeably different from a healthy one, both on imaging and during surgery.
Gallstones are the most common finding. On ultrasound, they show up as bright white spots that cast dark shadows behind them, a pattern that makes them easy to identify. Some stones are tiny, like grains of sand, while others can grow large enough to fill the entire organ. On a CT scan, stones are harder to spot because they can appear bright, gray, or dark depending on their composition.
When a stone gets stuck in the neck or cystic duct, it blocks bile from draining. This triggers acute cholecystitis, or gallbladder inflammation, which occurs in 90 to 95 percent of cases because of a trapped stone. The organ swells, its walls thicken well beyond the normal 3 millimeters, and fluid can accumulate around it. On ultrasound, the wall may appear as multiple distinct layers instead of a single thin line. In severe cases, the wall takes on a striped appearance. Visually during surgery, an inflamed gallbladder looks red, swollen, and tense rather than its usual blue-green. If infection progresses, it can turn dark green or even black in areas where tissue has started to die.
Chronic inflammation from repeated episodes of irritation changes the gallbladder over time. The walls become thick and scarred, the organ shrinks, and it may lose its smooth pear shape entirely. A chronically diseased gallbladder can look shriveled and hard, sometimes described as resembling a dried fig rather than a fresh pear.