Doctors have been warned to be on the look out for a potentially deadly complication of gallstones.
Surgery may be required
Up to one in 11 UK hospital patients with gallstones develops associated inflammation, called acute cholangitis.
The condition can quickly spread from the gall bladder and bile ducts and lead to shock and even death, warns Drug and Therapeutics Bulletin.
About 40% of patients will not display the classic symptoms and doctors should have a high suspicion for it, it adds.
The three classic symptoms of fever, abdominal pain and jaundice - a yellow discolouring of the skin and the eyes - are only seen in about 60% of patients.
Therefore, the DTB advises doctors to have a high suspicion for the condition even in patients with unexplained fever and abnormal liver test results, whether or not they have pain and jaundice.
Editor Ike Iheanacho said: "Acute cholangitis is a medical emergency and needs to be spotted and dealt with quickly.
"Doctors need to consider it as a possibility even in patients who do not have all the classical features of the disease."
Acute cholangitis is most often caused by gallstones.
The stones block the normal flow of bile and infection can occur in the stagnant fluid.
More rarely, it can be triggered by surgery to the bile ducts or a disease of the pancreas called chronic pancreatitis.
It kills as many as five in every 100 patients who develop it and prompt diagnosis and treatment are key to increasing the chance of survival.
Dr John Bennett, chairman of the gut and liver disorder charity CORE, said: "This is good advice."
He said if a doctor had any doubt, a standard blood test should show that there is a liver problem and alert them to the fact that the feverish patient might have cholangitis.