A gallbladder is a small, pear-shaped sac that sits just under the liver on the right side of the abdomen, measures roughly 7 to 10 centimeters long, and holds about 30 to 80 milliliters of dark green bile. That compact pouch concentrates bile between meals, then squeezes it into the small intestine once food arrives, and its appearance on imaging reflects both its quiet storage role and any disease process at work.
This article covers the gallbladder’s pear-shaped silhouette, the three regions and wall layers that define its anatomy, and how that appearance shifts on ultrasound and in disease.
A Small, Pear-Shaped Sac Tucked Beneath the Liver
Imagine a deflated green balloon resting in a shallow groove on the underside of the liver, and you have the rough mental image most anatomists use. The gallbladder sits in the right upper quadrant of the abdomen, just below the diaphragm, cradled against the visceral surface of the liver in a bed called the gallbladder fossa.
Its size and shape stay remarkably consistent across healthy adults, so a normal scan tends to look predictable. Here is what to expect from a gallbladder that looks and behaves as it should:
- Length: usually 7 to 10 centimeters when moderately full.
- Width: up to about 4 centimeters at the widest part.
- Capacity: around 30 to 80 milliliters of bile, roughly the volume of a small shot glass.
- Color: deep olive-green, owing to concentrated bile pigments such as bilirubin and biliverdin stored inside.
- Texture: thin-walled and pliable when healthy, slightly translucent in a fresh specimen.
Bile concentration varies meal to meal, so the apparent size on any scan depends on whether the organ has just emptied or has been quietly filling for hours. A scan done after fasting usually shows the gallbladder more clearly than one taken right after a fatty meal.
The Three Main Regions: Fundus, Body, and Neck
Like a small flask, the gallbladder divides into labeled sections that show up clearly on imaging and in textbooks, and each region has its own job. Knowing those roles makes a radiology report or an anatomy illustration far easier to follow.
Fundus, Body, and Neck in Plain English
Translating the clinical labels into everyday language keeps the terminology useful rather than intimidating, and the table below pairs each anatomical term with a plain-English equivalent and its function.
| Clinical term | Plain-English name | What it does |
|---|---|---|
| Fundus | The rounded bottom tip | Pokes slightly past the liver edge and is often the first part a doctor measures on a scan. |
| Body | The main pouch | Stores and concentrates bile while you fast. |
| Neck | The narrow exit spout | Tapers toward the liver and funnels bile into the cystic duct. |
Together those three regions form the gallbladder’s distinctive silhouette. The neck continues into the cystic duct, which joins the common hepatic duct to form the common bile duct, and that duct then empties into the small intestine where bile finally does its digestive work.
If a scan report mentions that the fundus projects beyond the liver edge, the wording simply means the rounded tip of the gallbladder is the part hanging out below the liver, where it can be measured most easily.
The Three Layers That Make Up the Wall
Three distinct layers make up the wall of the gallbladder, and each one plays a visible role despite the organ’s simple sac-like appearance. A healthy wall measures only in millimeters, and that single measurement tells clinicians a great deal about the organ’s condition.
Mucosa, Muscularis, and Serosa
The innermost mucosa folds into tiny ridges that flatten as bile fills the organ, creating a velvety, honeycomb-like surface when the gallbladder is empty. The cells lining those folds actively pump water out of bile to concentrate it for storage.
The middle muscularis is a thin sheet of smooth muscle that contracts in response to the hormone cholecystokinin after a meal. Without that squeeze, bile would sit in storage rather than move into the digestive tract.
The outer serosa is a slick membrane that lets the gallbladder glide against the liver and nearby intestine without friction, and it is what gives the organ its glossy look in surgical photos.
On ultrasound, all three layers blur into a single bright line that should measure roughly 2 to 3 millimeters thick in a fasted adult. A wall above 4 millimeters is generally considered thickened, which can signal inflammation, fluid overload, or a chronic condition such as cholecystitis.
How the Gallbladder Looks on an Ultrasound
Ultrasound imaging reveals the gallbladder as a dark, oval shadow tucked beneath the brighter dome of the liver above it. Because bile is fluid, sound waves pass straight through it, leaving the interior almost black on the screen, while the wall reflects a crisp white outline.
Reading a Normal Ultrasound Image
A healthy ultrasound shows a clean, echo-free interior, smooth borders, and a thin bright wall, with nothing floating, glowing, or casting shadows inside the bile. A scan done after fasting usually makes the organ look plump and well-defined, while one done right after eating may show a small, wrinkled, or partially collapsed shape.
Three features make ultrasound the first imaging choice for gallbladder problems. The exam is fast, often under 15 minutes. It uses no radiation, which matters for pregnant patients and repeat scans. And it reliably catches the three findings doctors look for most, namely gallstones, wall thickening, and pericholecystic fluid pooling around the organ.
When CT or MRI Adds Detail
CT and MRI step in when ultrasound leaves questions unanswered, and each brings a different strength. CT excels at showing calcified, bright-white gallstones and signs of inflammation in surrounding fat. MRI, specifically MRCP, maps the bile ducts in remarkable detail and becomes the go-to choice when a stone is suspected in the common bile duct rather than inside the gallbladder itself.
What an Unhealthy Gallbladder Looks Like Step by Step
Diseases of the gallbladder change its appearance in recognizable ways, and matching a scan finding to a real condition becomes much easier once you know what to look for.
Gallstones, Sludge, and Polyps
Gallstones show up as bright white spots or clusters that move when the patient changes position during the scan, and they cast an acoustic shadow because sound waves cannot pass through them. Sludge looks more like a layer of low-level echoes settling in the lowest part of the gallbladder, occasionally called biliary sand. Polyps are small soft-tissue bumps that cling to the inner wall, do not cast a shadow, and do not shift with gravity.
Acute and Chronic Inflammation
An acutely inflamed gallbladder typically looks swollen, with a wall thicker than 4 millimeters, fluid pooling around it, and tenderness when the ultrasound probe presses over the area. This combination goes by the name Murphy’s sign on imaging and often pairs with right-sided abdominal pain, fever, and nausea.
A chronically diseased gallbladder looks shrunken, scarred, and sometimes packed with sludge or debris. Radiologists describe this appearance with terms such as contracted gallbladder or wall-echo-shadow, the latter referring to the bright wall, the dark sludge layer, and the acoustic shadow from a packed stone stacked together.
Knowing each sign in isolation is useful, but most reports mention several findings together and want to know how to weigh them.
Polyps Versus Stones at a Glance
| Feature | Gallstone | Gallbladder polyp |
|---|---|---|
| Moves with gravity | Yes | No |
| Acoustic shadow | Yes | No |
| Attached to wall | No (typically free-floating) | Yes |
| Most common size concern | Any size if symptomatic | Usually flagged above 10 mm |
Reading Your Own Scan Report With Confidence
Once you know what a healthy gallbladder should look like, the words in a radiology report start to make sense. Reports lean on a small set of phrases to describe the organ’s appearance, and most of those phrases translate into plain English quickly.
Phrases That Signal a Normal Scan
Words that point to a healthy gallbladder include anechoic (the fluid inside reflects no sound waves), thin-walled, no filling defects, and within normal limits. Seeing any of those on a report is reassuring.
Phrases Worth Asking About
Terms that suggest a closer look include thickened wall, pericholecystic fluid, cholelithiasis (the formal name for gallstones), sludge, polyp, and distended. None of those is automatically alarming, but each one deserves a conversation with the doctor who ordered the scan.
Measurements to Bring Into Context
Numbers on a report only mean something in context. A gallbladder over 10 centimeters long or wider than 4 centimeters is often described as distended, sometimes because a stone is blocking the neck, while one under 5 centimeters may be called contracted, which usually just means it has emptied recently.
Pair the report with how you feel. A gallbladder that looks unusual on imaging but causes no symptoms often needs monitoring rather than urgent action, while a normal-looking gallbladder paired with classic right-sided pain may need a follow-up scan or blood work to catch what the first picture missed.
A confident reading matters most when it feeds into a practical next step, so it helps to pull the whole picture into one short checklist.
Putting It Together
The clearest mental image is also the simplest: a small, dark-green, pear-shaped pouch sitting in a shallow cradle on the underside of the liver, holding about a shot glass of bile, with three labeled regions (fundus, body, neck), a thin three-layer wall, and a distinctive ultrasound shadow. When something goes wrong, that tidy silhouette begins to change, and stones appear, walls thicken, fluid pools, or the organ shrinks into a scarred shadow of itself.
Recognize those changes and the scan report stops feeling like a foreign language.
FAQ
What does a gallbladder look like in the human body?
A gallbladder looks like a small, dark-green, pear-shaped pouch tucked against the underside of the liver in the right upper abdomen, measuring roughly 7 to 10 centimeters long and holding 30 to 80 milliliters of concentrated bile.
Where is the gallbladder located?
The gallbladder sits in the right upper quadrant of the abdomen, nestled in a shallow groove on the undersurface of the liver, with its fundus often peeking just past the liver’s edge.
How big is a normal gallbladder?
Most adult gallbladders stretch 7 to 10 centimeters in length, swell up to 4 centimeters wide at the body, and store roughly 30 to 80 milliliters of bile when moderately full.
What color is a healthy gallbladder?
Concentrated bile pigments give a healthy gallbladder a deep olive-green hue, and its thin, pliable wall appears slightly translucent in a fresh specimen.
What are the main parts of the gallbladder?
Three main regions define the gallbladder’s structure: a rounded fundus at the bottom, a wider body in the middle for bile storage, and a tapered neck that funnels bile into the cystic duct.
What does a gallbladder look like on an ultrasound?
On ultrasound, a healthy gallbladder appears as a dark, oval, echo-free shadow with a smooth thin wall, sitting under the brighter dome of the liver, with no internal echoes, stones, or surrounding fluid.
