Teaching Case

Right upper abdominal pain, nausea and low-grade fever in a 79-year-old man with history of coronary heart disease and lung emphysema. Positive Murphy’s sign and mild jaundice at physical examination. Slightly raised laboratory inflammation markers, leukocyte count and serum bilirubin.

US at Emergency Department admission was performed mostly through intercostal spaces because of the patient’s large body habitus and reported as technically very limited: gallbladder sludge and multiple stones were detected, but inflammatory changes and common bile duct were not confidently assessed.
Urgent abdominal MRI with MR cholangiopancreatography (MRCP), requested to investigate clinical suspicion of acute cholecystitis with coexistent choledocholithiasis, was performed the next day. Unenhanced MRI showed an overdistended gallbladder with intraluminal T1-hyperintense sludge and multiple T2-hypointense stones, the largest one obstructing the gallbladder neck. The gallbladder wall appeared diffusely thickened with alternating layers of abnormal signal and associated pericholecystic fluid. MRCP images depicted normal-caliber intrahepatic and common bile ducts, along with the characteristic hyperintense “C” sign of perihepatic fluid; common bile duct lithiasis was excluded.
Intravenous broad-spectrum antibiotics were administered; laparoscopic cholecystectomy was performed 5 days after hospital admission with surgical and pathological confirmation of acute uncomplicated calculous cholecystitis.

Acute cholecystitis usually manifests with right upper quadrant pain and tenderness, fever, vomiting, variably associated leukocytosis and abnormal inflammation markers: its common cause (in 90-95% of cases) is a gallstone obstructing the cystic duct or gallbladder neck [1, 2]. Pathologically, the distended gallbladder is filled with exudates and pus, and exhibits thickened oedematous walls [1].
US is the first-line modality to assess biliary tract disease thanks to its accuracy for stones and gallbladder inflammation, with a reported specificity of 60-100% [1, 2]. Its imaging findings in acute cholecystitis include luminal distention, thickening and hyperaemia of the wall, sometimes pericholecystic fluid, and positive sonographic Murphy’s sign [2,3].
As in this patient, US may be significantly impaired by body habitus, with degradation of image quality in overweight individuals: obesity represents an increasingly serious health problem and is significantly associated with cholelithiasis [1]. US is particularly inaccurate to detect cystic duct and choledochal stones, that need to be excluded before cholecystectomy [3, 4].
CT provides inconsistent visualisation of stones (only when calcified or gas-containing) and is reserved to investigate suspected complications such as emphysematous or perforated cholecystitis [2].
Owing to its increasing availability and technological improvements, MRI has been recently reported to be an attractive emergency imaging modality [3]. MRI with MRCP acquisition is considered to a valuable complementary modality for gallbladder evaluation in patients with inconclusive clinical, laboratory and US findings [1, 4].
Gallbladder sludge and stones are visualised on MRI as T1-hyperintense sediment and strongly hypointense foci [2]. Findings indicative of acute cholecystitis include gallbladder distention (transverse diameter over 4 cm), wall thickening (above 3 mm), oedema and stratification (alternating signal intensities in the gallbladder wall), pericholecystic fluid and oedema, and perihepatic fluid (the so-called “C sign”) [4, 5]. MRCP sequences reveal obstructing gallstones as the underlying cause of acute inflammation as roundish hypointense filling defects in the gallbladder neck or cystic duct [1, 4, 5]. Gallbladder distension and pericholecystic fluid help in the differential diagnosis from other causes of gallbladder wall thickening, whereas the entity of maximum wall thickness is not a significant indicator [1, 6].
MRCP provides additional valuable information, since detection of anatomic biliary tract variants helps to avoid intraoperative complications particularly during laparoscopic cholecystectomy; furthermore, as exemplified by this case, the possibility of coexistent choledocholithiasis should be verified in patients with acute cholecystitis to allow correct surgical planning, often avoiding invasive procedures such as ERCP [3].