Teaching Case

We report the case of a 66-year-old female patient with signs and symptoms of pneumonia and an unexpected finding on chest computer tomography (CT).

A 66-year-old female presents with signs and symptoms of left upper lobe pneumonia. CT confirms pneumonia and showed in addition curvilinear calcifications next to the liver (Fig. 1). US demonstrated the presence of gallbladder wall calcifications (Fig. 2).
After the imaging examinations, the patient was questioned and revealed a long standing history of upper right abdominal post-prandial discomfort which had caused her to limit her diet, but she had not seen a doctor about it.

Porcelain gallbladder (PG) refers to the macroscopic aspect of the calcified gallbladder wall with fragile and brittle consistency and bluish discoloration [1].

Cornell [2] attributes the first description of PG to Grandchamps, in 1797.
The incidence of this finding is low: about 0.06% to 0.8% of cholecystectomies. It is five times more common in women [3] with a series of cases reporting mean age of 54 years [2].
Histologically there are two types of calcification: one consisting of a continuous band within the muscularis, seen radiographically as plaque-like areas, the other scattered microliths in the mucosa and submucosa [4].
A relation between PG and gallbladder cancer was proposed by Kazmiersky in 1951 [5]. One study reported the incidence of cancer in PG between 12% and 61% [6], making it an important indication for cholecystectomy. Rooholamini et al [7] report PG in 4% of the gallbladder carcinomas reviewed. Recent studies suggest a lower incidence [8, 9], raising controversy over the association and therefore over the indication for prophylactic cholecystectomy [10].
The condition can present with symptoms associated with biliary disease, such as right-upper-quadrant abdominal discomfort after a fatty meal, as well as nausea, or fever. This condition can also be asymptomatic and an incidental finding on an imaging modality, as in our clinical case.
The possible absence of symptoms, along with associated risk for gallbladder cancer makes it important for the radiologist to alert to this finding.

PG presents as rim-like calcification on abdominal plain films, but CT is more sensitive to this finding.
On Ultrasound (US) there are three patterns described [11].
Type I, presenting as hyperechoic semilunar structure with complete posterior acoustic shadowing. Type II: a biconvex curvilinear echogenic structure with less posterior shadowing than type I. Type III presents as an irregular aggregate of echoes with less posterior acoustic shadowing than type I. US findings of this case are presented, corresponding to a type II PG US pattern.
CT scans of PG usually show a curvilinear or rim calcification, often with calculi within the gallbladder. If gallbladder carcinoma is present, associated pericholecystic mass, intrahepatic metastases and hilar lymphadenopathy may be found.
The obtained CT images show the curvilinear calcification, without solid content.

Our institution is in an endemic area for hydatid disease. A calcified hydatid cyst in this topography may be similar on US but will present with linear hyperechoic content (endocyst) or dependent echogenic dots (hydatid sand). It will be round and may have daughter-cysts. On CT, the round morphology of the hydatid cyst differentiates it from the gallbladder.

On US, the type I PG should be differentiated from echogenic content of the bladder, such as milk of calcium, gallbladder filled with stones (the “wall-echo-shadow” sign), or collapsed gallbladder with one large gallstone. This can be accomplished with identification of the hypoechoic non-calcified gallbladder wall externally to the hyperechoic gallbladder content (11). Similarly, enphysematous cholecystitis (with non-dependent gas casting a “shadow” posteriorly) could simulate type II calcification, but a careful technique should make the distinction (11). In the aforementioned situations radiography or CT may aid the diagnosis.