Acalculous cholecystitis is inflammation of the gallbladder that occurs without gallstones. While most gallbladder inflammation is caused by stones blocking the bile ducts, roughly 5 to 10 percent of cholecystitis cases happen in gallbladders that are completely stone-free. This form tends to be more dangerous than its stone-related counterpart, largely because it strikes people who are already critically ill and because it can be harder to diagnose quickly.
How It Develops Without Gallstones
In typical gallbladder inflammation, a gallstone gets lodged in a duct, bile backs up, and the gallbladder becomes irritated and swollen. Acalculous cholecystitis follows a different path. It starts when blood flow to the gallbladder drops, a situation called ischemia. This low-flow state can result from fever, dehydration, heart failure, or the general circulatory stress that comes with being critically ill.
When the gallbladder doesn’t get enough blood, its inner lining starts to break down. At the same time, if a person hasn’t eaten for an extended period, the gallbladder never gets the hormonal signal to contract and release bile. Bile sits stagnant, thickens, and the pressure inside the gallbladder rises. That combination of reduced blood flow, stagnant bile, and rising pressure creates the perfect conditions for inflammation. Once the lining is damaged, bacteria from the intestines can migrate in and establish an infection, making the situation worse.
Who Is Most at Risk
This condition is strongly associated with severe illness and major physical stress. The classic patient is someone already in an intensive care unit. Specific risk factors include:
- Major surgery, particularly cardiac surgery and abdominal vascular procedures
- Severe trauma or burns
- Prolonged fasting or being fed entirely through an IV (total parenteral nutrition), which removes the normal stimulus for the gallbladder to contract
- Sepsis, a body-wide infection that disrupts blood flow to organs
- Heart failure or shock, both of which reduce blood delivery to the gallbladder
Outside the ICU, acalculous cholecystitis can also occur in people with HIV, diabetes, or chronic kidney disease. It occasionally appears in otherwise healthy individuals, though this is uncommon. Men are affected slightly more often than women, which is the reverse of gallstone-related cholecystitis.
Symptoms and Warning Signs
Recognizing acalculous cholecystitis is tricky because the people who develop it are often sedated, on a ventilator, or too sick to clearly describe their symptoms. In patients who can communicate, the hallmarks are similar to standard gallbladder inflammation: pain or tenderness in the upper right side of the abdomen, fever, nausea, and sometimes vomiting.
On physical examination, the gallbladder may feel distended. A rapid heart rate and low blood pressure can signal that the condition is progressing. Blood tests often show elevated white blood cell counts and sometimes mildly elevated liver enzymes or bilirubin levels. None of these findings are unique to this condition, which is part of what makes it so easy to miss in a patient who already has multiple reasons to be feverish or have abnormal lab results.
How It Is Diagnosed
Ultrasound is the first imaging test used. Because no gallstones will be visible, doctors look for indirect signs of inflammation: a gallbladder wall thicker than 3 millimeters, fluid collecting around the gallbladder, gallbladder distension beyond 4 centimeters in diameter, and swelling within the wall itself. Pressing the ultrasound probe directly over the gallbladder and checking whether it causes sharp pain (called a sonographic Murphy sign) also helps point toward the diagnosis.
If ultrasound results are unclear, a specialized nuclear medicine scan can assess how well the gallbladder is functioning. In this test, a tracer is injected into the bloodstream and tracked as it moves through the liver and bile ducts. If the gallbladder fails to fill with the tracer, it suggests the organ is blocked or severely inflamed. CT scans can also reveal wall thickening, surrounding fluid, and other complications like tissue death within the gallbladder wall.
Why It Is Considered More Dangerous
Acalculous cholecystitis carries a significantly higher mortality rate than gallstone cholecystitis. Estimates vary, but the death rate in critically ill patients can reach 30 to 50 percent, compared to under 5 percent for typical gallstone-related inflammation. Much of that difference comes from the patient population itself, since most people with acalculous cholecystitis are already fighting life-threatening conditions. But the disease process also tends to move faster: the gallbladder wall can lose its blood supply entirely, leading to gangrene, and the weakened tissue can perforate. Gangrene and perforation occur more frequently in acalculous cases than in stone-related ones, and both are surgical emergencies.
Treatment Options
The definitive treatment is removing the gallbladder, a procedure called cholecystectomy. When it can be done laparoscopically (through small incisions using a camera), outcomes tend to be better in terms of recovery time, complication rates, and overall cost. The challenge is that many patients with acalculous cholecystitis are too unstable to tolerate surgery right away.
For those patients, a temporary drainage procedure offers an alternative. A thin tube is placed through the skin and into the gallbladder, guided by ultrasound or CT imaging, to drain infected bile and relieve pressure. This can stabilize a patient enough to either recover without surgery or become well enough for a later operation. However, drainage tubes come with their own risks, including higher rates of infection and longer hospital stays compared to direct surgical removal. Once the patient is stable enough, most surgeons will proceed with gallbladder removal.
Antibiotics are started early to address bacterial infection, and supportive care focuses on correcting the underlying conditions that triggered the inflammation in the first place: restoring adequate blood flow, managing fever and dehydration, and resuming some form of feeding through the gut when possible to stimulate normal gallbladder function.
Recovery and Long-Term Outlook
For patients who survive the acute episode and undergo gallbladder removal, the gallbladder-related problem is resolved permanently. The body adjusts well to life without a gallbladder, since bile simply flows directly from the liver into the small intestine. Some people notice looser stools or mild digestive changes for a few weeks or months after surgery, but these typically settle on their own.
The broader recovery depends heavily on whatever condition landed the patient in the hospital originally. Someone who developed acalculous cholecystitis after major trauma or cardiac surgery may face a long rehabilitation unrelated to the gallbladder itself. For the smaller number of people who develop this condition outside of a critical care setting, recovery after surgery is generally straightforward, similar to a standard gallbladder removal for gallstones.