Ectopic liver attached to the gallbladder: An unusual incidentaloma

Flavia C. Soto, MD Research Fellow

Samuel Szomstein, MD

Co-Director

Raul J. Rosenthal, MD

Director

The Bariatric Institute and Section of Minimally Invasive Surgery

Cleveland Clinic Florida

Weston, FL

Ectopic livers are extremely rare and usually found incidentally during autopsy or laparoscopic surgery.¹ They may be located in the ligaments or mesentery and on the surface of the gallbladder, spleen, or adrenal glands.² Hepatic tissue in the gallbladder is typically asymptomatic and is found either incidentally or because of concordant complications. In 1940, Eiserth noted several cases of ectopic liver among 5,500 autopsy patients in Hungary.³ In 1982, Asada and colleagues reported on 1,060 cases in which laparoscopy revealed a 0.47% incidence of ectopic liver and a 0.09% incidence of accessory lobe.⁴We report the case of ectopic liver tissue discovered incidentally in the gallbladder of a patient who underwent elective laparoscopic cholecystectomy, and we provide a review of the literature.

Case report

A 32-year-old woman presented to our institution after experiencing several months of right upper quadrant pain, accompanied by nausea and flank pain. Her symptoms worsened after meals, and episodes were increasing in frequency. The patient's physical examination was unremarkable, except for mild tenderness elicited during deep palpation of the right upper quadrant. There was no evidence of hepatosplenomegaly or jaundice, and tests for liver function and amylase levels were normal. Ultrasonography revealed multiple gallstones, without common bile duct dilatation.

The patient was taken to the operating room, and laparoscopic cholecystectomy with a cholangiogram was performed with no complications. The only significant finding was a well-defined, 1 x 1-cm mass attached to the posterior wall of the gallbladder serosa and isolated from the liver (Figure 1). The patient tolerated the procedurewell, her postoperative recovery was unremarkable, and she was discharged to home on postoperative day 2.

The excised gallbladder measured 8 x 2 x 2 cm, contained numerous green-to-yellow stones, and had an edematous serosal surface. A small, well-defined, gray nodule, measuring approximately 0.8 cm at its greatest dimension, was attached to the serosal surface midway between the fundus and the neck.Microscopic examination showed the nodule was composed of portal triads and lobules, which are characteristic of hepatic tissue (Figure 2). High-power observation revealed detailed components of the portal tract, including the vein, artery, and bile ducts (Figure 3).

Discussion

Embryological development of the liver and bile ducts begins between days 21 and 30 of gestation, with the appearance of an endodermal bud and the formation of the duodenum in the ventral angle between the foregut and the yolk sac.^5,6This hepatic bud divides into a larger cranial portion, known as pars hepatica, and a smaller caudal portion, known as pars cystica. The pars hepatica extends into the mesenchymal tissue of the septum transversum and divides into the right and left lobes of the liver, which eventually give rise to the liver cells and intralobular bile ducts. The septal mesodermal cells form the hepatic capsule and the connective tissue of the liver.

The pars cystica gives origin to the gallbladder and cystic duct around week 5 of gestation. Recanalization commences dur?ing week 6, starting with the common bile duct. The gallbladder gains its lumen during week 12. The close relationship between the development of the cystic portions and the trabecular parenchymal cell cords explains why ectopic livers may be found in the gallbladder.^5-7

The term choristoma, from the Greek word meaning "to separate," describes displacement and was introduced by Albrecht in 1904. In pathological terms, choristo?mas are microscopically normal cells or tissues in abnormal locations.⁸

Liver tissue that forms outside the liver varies considerably and is usually found near or communicating with the liver or extrahepatic biliary system. Abnormally positioned liver tissue occasionally causes clinical symptoms.⁹ Several possible mech?anisms may explain ectopic livers at various sites. Two probable explanations are the development of an accessory liver lobe with atrophy or regression of the original connection to the main liver and the displacement or migration of a portion of the pars hepatica to the rudiment of various organs including hepatic ligaments, adrenal glands, pancreas, and umbilical cord.^10,11 The most common location of ectopic liver is on the gallbladder.⁵

Liver choristomas or ectopic nodules of liver tissue that are attached to the gallbladder by their own mesentery and are completely detached from the liver are uncommon.^6,12,13Their typical location is in the gallbladder wall but, in some cases, they are found within the submucosa of the gallbladder.

Anomalous liver tissue in the wall of the gallbladder has been described by various categories and names. Simple classifications based on previous definitions are (1) accessory liver lobe, when there is attachment to the main liver organ; (2) ectopic or heterotopic liver nodule, when the choristoma is completely detached from the liver and is found in an abnormal location, usually attached to the gallbladder (choristoma); and (3) aberrant microscopic tissue, in cases of ductal origin, when the tissue is present within the lumen of a true Luschka duct in the wall of the gallbladder.⁵

The histologic appearance of ectopic liver tissue is similar to that of the liver, with lobules, central veins, and normal portal areas.¹⁴ Therefore, these anomalies may be underdiagnosed and, because of incomplete development, may quickly undergo atrophy or fibrosis, resolving prior to diagnosis.⁵

Liver choristomas are usually incidental asymptomatic findings, as in our case²; however, a pedunculated and aberrant liver may become strangulated and cause acute abdominal symptoms.¹³ Ectopic liver with portal cirrhosis,⁶ fatty infiltration,¹² and hepatocarcinoma have also been report?ed.¹⁵ These conditions occur because small ectopic liver tissue lacks a complete, functional architecture and may be metabolically handicapped, thereby facilitating the carcinogenetic process.¹⁵In our case, the hepatic nodule was situated in the serosa without any connection to the liver and was histologically normal tissue.

Conclusion

Liver choristomas are exceedingly rare. While they are generally asymptomatic and an incidental finding during laparoscopy for unrelated issues, they should be considered in the differential diagnosis of any patient presenting with abdominal symptoms.

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