Applied Radiology

CASE SUMMARY

A 76-year-old woman presented to the emergency department with intractable nausea and vomiting. Initial evaluation included an abdominal computed tomographic (CT) scan that demonstrated nonspecific intrahepatic ductal dilatation (Figure 1) and a normal hepatobiliary scan (not shown). The patient was treated conservatively. A few months later, she developed vague abdominal pain, fever, leukocytosis, and elevated pancreatic enzymes. Abdominal sonography was interpreted as normal. Repeat abdominal CT demonstrated a 4.5-cm irregularly enhancing cystic mass within the gallbladder fundus, persistent intrahepatic ductal dilatation, and common bile duct dilatation (Figure 2). A preliminary diagnosis of gallbladder carcinoma was made. Pathology following open cholecystectomy found no evidence of malignancy.

DIAGNOSIS

Xanthogranulomatous cholecystitis (XGC)

IMAGING FINDINGS

In October 2000, an emergent abdominal CT scan showed mild nonspecific intrahepatic ductal dilatation. Retrospectively, an eccentric gallbladder mass was evident at this time, but the mass mimicked contrast within the hepatic flexure of the colon (Figure 1). When the patient was re-evaluated in January 2001 due to worsening symptoms, abdominal sonography was interpreted initially as normal, but repeat abdominal CT revealed a complex cystic mass within the gallbladder fundus as well as mild intrahepatic and extrahepatic dilatation (Figure 2). After a surgical diagnosis was made, review of the earlier ultrasound determined that what was originally thought to be debris within the adjacent stomach was actually an atypically appearing fundal gallbladder mass (Figure 3).

PATHOLOGIC FINDINGS

Gross pathologic examination showed a large, chronically inflamed gallbladder measuring 5 * 4 cm and cholelithiasis (Figure 4). Histologic analysis found xanthogranulomatous cholecystitis and malacoplakia, with focal microscopic sinus formation (Figure 5).

DISCUSSION

Christensen and Ishak ¹ first coined the pathologic diagnosis of XGC, describing seven patients with pseudotumors of the gallbladder. Many pseudonyms such as ceroid granulomas, ceroid-like histiocytosis, and fibroxanthogranulomatous inflammation existed before the Armed Forces Institute of Pathology formally characterized XGC. ² The reported incidence of XGC varies from 0.66% to 1.8%. ^2-5 Preoperative diagnosis is rarely made. Frequently, the patients are misdiagnosed as having cholelithiasis or a primary cancer. Xanthogranulomatous cholecystitis was initially thought to be a malignant disease process; many studies now show that this disease behaves in a similar fashion to another benign disorder, xanthogranulomatous pyleonephritis (XGP). ^6,7

Both of these disease processes are associated with chronic infection and calculi that induce histiocytes to begin the inflammatory cascade. ^6-8 Sjodahl ⁹ first speculated that gallbladder calculi creating mechanical trauma along the mucosa incite the inflammatory response. The inflammation causes lechitin in the bile to react with free fatty acids, producing lysolecithin. This results in further damage to the gallbladder mucosa, initiating a destructive cascade. ^3,10 This inflammatory process progresses from cholecystitis to XGC when the Rokitansky-Aschoff sinuses become occluded and inspissated with bile and mucin. ^3,4,8,10,11 When the wall tension of the distended gallbladder exceeds its natural compliance, the Rokitansky-Aschoff sinuses rupture, spreading inflammation to the adjacent tissues. ^2-4,10 The degradation of bile results in phagocytosis of insoluble cholesterol and bile salts by histiocytes, giving the characteristic XGC appearance of macrophage-laden and foamy histiocytes. ^2,10

Xanthogranulomatous cholecystitis has many similarities to its original counterpart, but it is generally more severe. Similar pathogens found in both XGC and cholecystitis include Klebsiella , E. coli , Proteus mirabilis , Enterobacter , and Citrobacter . ¹² Since XGC is usually not suspected preoperatively, neither are its sequelae. Complications such as gallbladder perforation, hepatic abscess, biliary ductal stricture and obstruction, ascending cholangitis, and biliary fistula are associated more commonly with XGC. ^2-5 Although imaging modalities ^13,14 such as CT, ultrasound, endoscopic retrograde cholangiopancreatography, and percutaneous transhepatic cholangiography aid in diagnosing the complications of XGC, only histologic examination of a surgical specimen will accurately give the diagnosis. ⁵ In addition, there is an increased association of underlying carcinoma in patients with XGC than in those with ordinary cholecystitis. ^15-17

Due to the high prevalence of primary fistulas, cholecystectomy is accompanied by excision of all surrounding xanthogranulomatous tissue to assure removal of any fistula. ^2-5 Since dissection in Calot's triangle is difficult due to the dense fibrosis, laparoscopic surgery is rarely successful. ^2,8 Some have advocated subtotal cholecystectomy with drainage of the subhepatic space to decrease the likelihood of iatrogenic injury. ¹⁷ Also, due to the high incidence of associated fistulas and malignancies, many advocate intraoperative cholangiography. ⁵

CONCLUSION

Xanthogranulomatous cholecystitis is an uncommon variant of cholecystitis that is rarely diagnosed preoperatively. It is generally more virulant than ordinary cholecystitis, but the same pathogens are isolated from both, implicating a primarily histiocytic driven inflammatory mechanism as the cause of complicating sequelae.