- Decision analysis is a formal process used to determine
the preferred course of action from two or more potential approaches
to clinical management.
Decision analysis is most appropriate when there is both some
uncertainty about the preferred course of action and a meaningful
trade-off of risks and benefits for the alternative management strategies.
A decision tree or decision diagram is the underlying structure
of the clinical situation, including all uncertainties and choices,
as well as all outcomes.
The expected utility is the estimated typical or average outcome
for a population of patients managed with a particular strategy.
Substituting a range of values for a particular probability
in a decision tree and determining the impact on the expected utility
is referred to as a sensitivity analysis.
A 50-year-old man presented to his physician with a high fever
and severe abdominal pain. This patient occasionally worked as a
house painter, and although he reported heavy use of alcohol, he had
been in generally good health. There was no history of exposure
to toxic substances or intravenous drug use. On physical examination,
the patient was jaundiced, and he had severe tenderness to palpation
in the right upper quadrant of his abdomen. Laboratory examination
revealed leukocytosis accompanied by elevations in the serum levels
of bilirubin, alkaline phosphatase, and serum glutamic oxaloacetic
transaminase (SGOT, aspartate aminotransferase). It was considered
that the patient had either alcoholic hepatitis or cholangitis (inflammation
of a bile duct). It is necessary to differentiate cholangitis, which
requires surgery, from alcoholic hepatitis, in which surgery is
contraindicated. In fact, the postoperative mortality for alcoholic
hepatitis is very high. The issue for the medical decision-maker
is to choose the alternative that will carry the greatest benefit
for the patient with the lowest achievable risk.
Cholangitis, an infection of the biliary ductal system, classically
presents with a triad of fever, jaundice, and pain in the right
upper quadrant of the abdomen. The clinical illness arises in the presence
of bacterial colonization of the bile, most commonly because of
obstruction of biliary tract flow. Historically, the most common
underlying cause of obstruction was blockage of the biliary tract
by stones, although malignant strictures have become increasingly
important contributors in recent years. The increased pressure within
the bile ducts resulting from obstruction produces bacterial reflux
into the hepatic veins and perihepatic lymphatics, with subsequent
bacterial spread into the circulating bloodstream. The bacteria
associated with cholangitis include Escherichia
coli, Klebsiella species, and the enterococci, with a shift
more recently to include Enterobacter and Pseudomonas species. Infections typically
involve multiple species of organisms.
The clinical manifestations of cholangitis range from asymptomatic
illness to severe toxic symptoms, including septic shock. Fever
is present in almost all patients, typically accompanied by chills.
Jaundice and abdominal pain in the right upper quadrant of the abdomen
are part of the classical description of presenting symptoms, although
they may not be present in the absence of obstructive stones. Complications