A gallbladder infection almost always starts with a blockage. In about 90% of cases, a gallstone gets wedged in the narrow duct that drains bile out of the gallbladder, trapping bile inside and triggering a cascade of inflammation that eventually allows bacteria to take hold. The remaining cases happen without any stone at all, usually when blood flow to the gallbladder drops during a critical illness. Either way, the infection isn’t the first thing that goes wrong. It’s the consequence of a gallbladder already under stress.
The Blockage That Starts It All
Your gallbladder stores bile, a digestive fluid made by the liver, and squeezes it into the small intestine when you eat. Bile exits through a small tube called the cystic duct. When a gallstone lodges in that duct and stays there, bile has nowhere to go. It pools inside the gallbladder, and the trouble begins.
Stagnant bile triggers the release of inflammatory enzymes. One key enzyme converts a normal bile component into a compound that directly damages the gallbladder’s inner lining. The damaged lining then secretes more fluid into the gallbladder than it can reabsorb, causing the organ to swell. That swelling releases still more inflammatory chemicals, which worsen the mucosal damage and start to choke off blood flow to the gallbladder wall. It’s a self-reinforcing cycle: obstruction leads to inflammation, inflammation leads to swelling, and swelling makes everything worse.
How Bacteria Enter the Picture
Bacteria don’t cause the initial inflammation. They arrive afterward, colonizing tissue that’s already injured and poorly supplied with blood. A healthy gallbladder resists bacterial growth because bile flows through it regularly and the intact mucosal lining acts as a barrier. Once that lining is damaged and bile is stagnant, bacteria from the gut can migrate up through the bile ducts or spread through the bloodstream into the compromised tissue.
The most common bacteria found in infected bile are E. coli and Enterococcus, each showing up in roughly equal numbers. Klebsiella is the next most frequent, followed by Enterobacter and Pseudomonas. These are all gut-dwelling organisms, which makes sense given the direct connection between the intestine and the biliary system. In severe cases, the gallbladder fills with pus, a condition called empyema. If the infection continues unchecked, portions of the gallbladder wall can die (gangrene), and the organ can eventually perforate, leaking infected material into the abdominal cavity.
Infection Without Gallstones
About 5 to 10% of gallbladder infections develop without a stone blocking anything. This form, called acalculous cholecystitis, typically strikes people who are already critically ill: patients in intensive care with sepsis, those recovering from major surgery, burn victims, or anyone in prolonged shock. The mechanism is different but the result is similar.
In these cases, the problem begins with poor blood flow. The artery supplying the gallbladder is a terminal vessel with very little backup from surrounding blood vessels, making it especially vulnerable when blood pressure drops or cardiac output falls. Reduced perfusion damages the gallbladder wall, causing swelling that decreases the organ’s ability to contract and push bile out. Bile stasis follows, viscosity increases, and intraluminal pressure rises. Stagnant bile combined with ongoing poor blood supply creates ideal conditions for bacteria to colonize the tissue. Imaging studies of gallbladders removed from these patients show irregular, patchy blood flow patterns, compared to the smooth, well-filled vessels seen in stone-related cases.
Risk Factors That Set the Stage
Since gallstones are the primary trigger, anything that raises your risk of gallstones also raises your risk of a gallbladder infection. Being overweight is one of the strongest factors. Rapid weight loss, whether from crash dieting or bariatric surgery, also increases gallstone formation because it changes the chemical balance of bile. A diet high in fat and low in fiber contributes as well.
Beyond stones, certain conditions create vulnerability through other pathways. Severe illness can damage blood vessels and reduce gallbladder perfusion directly. Viral infections, including HIV/AIDS, can inflame the gallbladder on their own. Tumors that press on the bile ducts can prevent normal drainage, causing the same kind of stasis that a lodged stone would. Even thickened bile or tiny particles called sludge, which aren’t true stones, can block the duct or create enough stagnation to start the inflammatory process. Scarring or kinking of the bile ducts from previous inflammation or surgery can do the same.
What a Gallbladder Infection Feels Like
The hallmark symptom is steady, severe pain in the upper right abdomen that lasts for hours rather than the brief waves of discomfort that come with ordinary gallstone attacks. The pain often radiates to the right shoulder or back. Fever, nausea, and vomiting are common. You may notice your heart racing, and in more advanced cases, yellowing of the skin and eyes can develop if the infection or swelling affects the main bile duct.
One of the most reliable physical signs is a sharp spike of pain when you breathe in deeply while pressure is applied just below your right ribcage. Doctors call this Murphy’s sign, and it’s about 97% sensitive for acute gallbladder inflammation, meaning it catches nearly every case. In more serious infections, the tenderness spreads beyond the upper right quadrant. Widespread abdominal rigidity and tenderness suggest that the gallbladder may have leaked or ruptured, allowing inflammatory fluid or infected contents to irritate the abdominal lining.
How the Infection Is Treated
The standard treatment is surgical removal of the gallbladder, typically performed laparoscopically through a few small incisions. Current guidelines favor doing this early, within the first few days of symptoms, rather than waiting weeks for the inflammation to settle. Early surgery shortens hospital stays and reduces the chance of complications like gangrene or perforation. Antibiotics are given alongside surgery to control the bacterial component, but they can’t resolve the underlying problem on their own because the blocked, inflamed organ remains a reservoir for reinfection.
For patients too sick to tolerate surgery, particularly those with acalculous cholecystitis who are already in critical condition, a temporary drain can be placed through the skin into the gallbladder to relieve pressure. This buys time until the patient is stable enough for definitive surgery. Recovery from laparoscopic removal is relatively quick: most people go home within a day or two and return to normal activities within one to two weeks. Your body adjusts to life without a gallbladder by routing bile directly from the liver into the intestine, though some people experience looser stools for a few months as the digestive system adapts.