ACUTE CHOLECYSTITIS CHRONIC CHOLECYSTITIS
Category: Diagnostic Radiology
Abstract : INFLAMMATORY GALLBLADDER DISEASE Cholecystitis is usually associated with
gallstones; the frictional action of stones on the gallbladder wall causes some
degree of inflammation in almost all cases. The inner mucosa of the wall is
injured, allowing the access of enteric bacteria. The inflammatory process may
be long-standing and chronic, acute or a combination of acute inflammation on a
INFLAMMATORY GALLBLADDER DISEASE
Cholecystitis is usually associated with
gallstones; the frictional action of stones on the gallbladder wall causes some
degree of inflammation in almost all cases. The inner mucosa of the wall is
injured, allowing the access of enteric bacteria. The inflammatory process may
be long-standing and chronic, acute or a combination of acute inflammation on a
chronic background.
Acute cholecystitis
Acute inflammation of the
gallbladder presents with severe RUQ pain localized to the gallbladder area. The
pain can be elicited by (gently!) pressing the gallbladder with the ultrasound
transducer—a positive ultrasound Murphy’s sign. (This sign, although a useful
pointer to acute inflammation, is not specific and can frequently be elicited in
other conditions, such as chronic inflammatory cases.) On ultrasound, the
gallbladder wall is thickened greater than 2 mm. This is not in itself a
specific sign, but characteristically the thickening in acute cholecystitis is
symmetrical, affecting the entire wall, and there is an echo-poor ‘halo’ around
the gallbladder as a result of oedematous changes. This is not invariable,
however, and focal thickening may be present, or the wall may be uniformly
hyperechoic in some cases. Pericholecystic fluid may also be present, and the
inflammatory process may spread to the adjacent liver.
Colour or power
Doppler can be helpful in diagnosing acute cholecystitis and in differentiating
it from other causes of gallbladder wall thickening. Hyperaemia in acute
cholecystitis can be demonstrated on colour Doppler around the thickened wall.
In a normal gallbladder, colour Doppler flow may be seen around the gallbladder
neck in the region of the cystic artery but not elsewhere in the wall. The
increased sensitivity of power Doppler, as opposed to colour Doppler, does
enable the operator to demonstrate vascularity in the normal gallbladder wall
and the operator should be familiar with normal appearances for the machine in
use when making the diagnosis of acute cholecystitis. Doppler can potentially
distinguish acute inflammation from chronic disease.15 However, falsepositive
results can be found in cases of pancreatitis and gallbladder carcinoma and the
technique does not add significantly to the grey-scale image. Complications may
occur if the acute inflammation progresses (see below) due to infection,
pericholecystic abscesses and peritonitis.
Further management of acute
cholecystitis
In an uncomplicated acute cholecystitis, analgesia to settle
the patient in the short term is followed by the removal of the gallbladder.
Open surgery, which is increasingly reserved for the more complex cases, is
giving way to the more frequent use of laparoscopic cholecystectomy. If
unsuitable for immediate surgery, for example in cases complicated by
peritonitis, the patient is managed with antibiotics and/or percutaneous
drainage of pericholecystic fluid or infected bile from the gallbladder, usually
under ultrasound guidance. This allows the patient’s symptoms to settle and
reduces morbidity from the subsequent elective operation. Hepatobiliary
scintigraphy has high sensitivity and specificity for evaluating patients with
acute cholecystitis, particularly if the ultrasound examination is technically
difficult or equivocal and has the advantage of being able to demonstrate
hepatobiliary drainage into the duodenum. Plain X-ray is seldom used, but can
confirm the presence of gas in the gallbladder.
Chronic
cholecystitis
Usually associated with gallstones, chronic cholecystitis
presents with lower-grade, recurring right upper quadrant pain. The action of
stones on the wall causes it to become fibrosed and irregularly thickened,
frequently appearing hyperechoic. The gallbladder is often shrunken and
contracted, having little or no recognizable lumen around the stones. Chronic
cholecystitis may be complicated by episodes of acute inflammation on a
background of the chronic condition. Most gallbladders which contain stones show
at least some histological degree of chronic cholecystitis, even if wall
thickening is not apparent on ultrasound.
Acalculous
cholecystitis
Inflammation of the gallbladder without stones is relatively
uncommon. A thickened, tender gallbladder wall in the absence of any other
obvious cause of thickening may be due to acalculous cholecystitis. This
condition tends to be associated with patients who are already hospitalized and
have been fasting, including post-trauma patients, those recovering from
surgical procedures and diabetic patients. It is brought about by bile stasis
leading to a distended gallbladder and subsequently decreased blood flow to the
gallbladder. This, especially in the weakened postoperative state, can lead to
infection. Because no stones are present, the diagnosis is more difficult and
may be delayed. Patients with acalculous cholecystitis are therefore more likely
to have severe pain and fever by the time the diagnosis is made, increasing the
incidence of complications such as perforation. The wall may appear normal on
ultrasound in the early stages, but progressively thickens. Biliary sludge is
usually present and a pericholecystic abscess may develop in the later stages. A
positive Murphy’s sign may help to focus on the diagnosis, but in unconscious
patients the diagnosis is a particularly difficult one. Because patients may
already be critically ill with their presenting disease, or following surgery,
there is a role for ultrasound in guiding percutaneous cholecystostomy at the
bed-side to relieve the symptoms. Chronic acalculous cholecystitis implies a
recurrent presentation with typical symptoms of biliary colic, but no evidence
of stones on ultrasound. Patients may also demonstrate a low ejection fraction
during a cholecystokinin-stimulated hepatic iminodiacetic acid (HIDA) scan. The
symptoms are relieved by elective laparoscopic cholecystectomy in most patients,
with similar results to those for gallstone disease19 (although some are found
to have biliary pathology at surgery, which might explain the symptoms, such as
polyps, cholesterolosis or biliary crystals/tiny stones in addition to chronic
inflamation).
Complications of cholecystitis
Acute-on-chronic
cholecystitis Patients with a long-standing history of chronic cholecystitis may
suffer (sometimes repeated) attacks of acute inflammation. The gallbladder wall
is thickened, as for chronic inflammation, and may become focally thickened with
both hypo- and hyperechoic regions. Stones are usually
present.
Gangrenous cholecystitis
In a small percentage of patients,
acute gallbladder inflammation progresses to gangrenous cholecystitis. Areas of
necrosis develop within the gallbladder wall, the wall itself may bleed and
small abscesses form. This severe complication of the inflammatory process
requires immediate cholecystectomy. The gallbladder wall is friable and may
rupture, causing a pericholecystic collection and possibly peritonitis.
Inflammatory spread may be seen in the adjacent liver tissue as a hypoechoic,
ill-defined area. Loops of adjacent bowel may become adherent to the necrotic
wall, forming a cholecystoenteric fistula. The wall is asymmetrically thickened
and areas of abscess formation may be demonstrated. The damaged inner mucosa
sloughs off, forming the appearance of membranes in the gallbladder lumen. The
gallbladder frequently contains infected debris The presence of a bile leak may
also be demonstrated with hepatobiliary scintigraphy, using technetium99, which
is useful in identifying a bile collection which may otherwise be obscured by
bowel on ultrasound.
Emphysematous cholecystitis
This is a form of
acute gangrenous cholecystitis in which the inflamed gallbladder may become
infected, particularly in diabetic patients, with gasforming organisms. Both the
lumen and the wall of the gallbladder may contain air, which is highly
reflective, but which casts a ‘noisy’, less definite shadow than that from
stones. Discrete gas bubbles have been reported on ultrasound within the
gallbladder wall and may also extend into the intrahepatic biliary ducts. The
air rises to the anterior part of the gallbladder, obscuring the features behind
it. This effect may mimic air-filled bowel on ultrasound. Emphysematous
cholecystitis has traditionally had a much higher mortality rate than other
forms of cholecystitis, requiring immediate cholecystectomy. However,
improvements in ultrasound resolution, and in the early clinical recognition of
this condition, suggest that it is now being diagnosed earlier and may be
managed more conservatively. The gas in the gallbladder may be confirmed on a
plain X-ray, but ultrasound is more sensitive in demonstrating the earlier
stages.
Gallbladder empyema
Empyema is a complication of cholecystitis
in which the gallbladder becomes infected behind an obstructed cystic duct. Fine
echoes caused by pus are present in the bile. These patients are often very ill
with a fever and acute pain. A pericholecystic gallbladder collection may result
from leakage through the gallbladder wall with subsequent peritonitis.
Ultrasound may be used to guide a bedside drainage in order to allow the
patient’s symptoms to settle before surgery is attempted.
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