INTRODUCTION

Ectopic liver is a rare congenital developmental abnormality of the position of liver tissue with an estimated incidence of 0.24-0.48 % and a prevalence rate of 0.47 % (^{Martinez et al., 2013}). There are two forms of abnormal position of liver tissue: ectopic liver with no connection with the mother liver and accessory lobe of ectopic liver, where the connection exists. ^{Collan et al. (1978}) classified four categories of ectopic livers: the first category is ectopic liver tissue that is not connected to the main liver and is typically attached to the gallbladder or intra-abdominal ligaments; the second is microscopic ectopic liver found mostly in the gallbladder wall; the third is a large accessory liver lobe attached to the main liver by a stalk; and the fourth is a small accessory liver lobe attached to the main liver. In a laparoscopic series of 1060 cases, the incidences of ectopic liver with no connection and accessory lobe of the liver were 0.47 % and 0.09 %, respectively (^{Watanabe et al., 1989}).

Ectopic livers are generally small in diameter and do not often cause clinical symptoms. For these reasons the diagnosis of ectopic liver in the majority of cases is made incidentally during surgery, laparoscopy or autopsy. It may be localized in the majority of cases in the walls of gallbladder but also in other sites in the abdominal cavity or in thoracic cavity (^{Caygill & Gatenby, 2004}; ^{Chen et al., 2014}). In this case report we want to assess the importance of CT examination in the preoperative diagnose of an ectopic liver localized in the left hypocondrium, attached to the serosa of stomach, as a differential diagnose among other benign and malign condition in this region.

CASE REPORT

A 70-year-old patient presented at the Radiology department of UHC “Mother Tereza” with complaints of abdominal pain. Previous medical history included the intervention for a tumor of ascending colon performed some years ago. The patient had undergone a CT Scanner examination for further evaluation. The patient was diagnosed with postoperative adhesive ileus and was referred to the surgery department. During the CT scanner examination a mass was detected in the left subdiafragmatic region. It was attached to the serosa of stomach near the fundus, and the most probable suspected diagnosis was a tumor of the stomach wall. The examination of upper digestive endoscopy resulted normal. During the CT examination it was noticed that the formation had similar structure with the mother liver and was connected to it by a stalk.

The patient underwent surgery for adhesive ileus and the presence of ectopic liver was confirmed intra-operatively, classified according Collan classification as type three, because it was presented as a large accessory liver lobe attached to the main liver by a stalk. (Fig. 1).

Fig. 1 Abdominal CT: A left subdiafragmal mass next to the lateral wall of stomach (white arrow) connected to the mother liver by a stalk. 

DISCUSSION

The liver develops from the hepatic diverticulum in the fourth week of gestation. It derives from an endodermal bud from the most caudal part of foregut and projects into the septum transversum (^{Hamilton et al., 1972}). The hepatic diverticulum differentiates into cranial or pars hepatica portion from which will derive the future liver and caudal or pars cystica portion from which the future gallbladder and cystic duct will derive (^{Tejada & Danielson, 1989}). Most researchers believe that the cause of ectopic liver is an aberrant migration during the embryologic development of the liver (Tejada & Danielson; Watanabe et al.; Martinez et al.). Hepatocytes in an ectopic liver behave like normal hepatocytes therefore they share the same risk factors for fatty changes, haemosiderosis, cholestasis or cirrhosis as hepatocites in the mother liver. It is important to assess the fact that they may demonstrate an increased risk of carcinogenesis likely secondary to incomplete anatomic architecture and metabolic derangement (^{Arakawa et al., 1999}).

Different sites of locations intrathoracic and intraabdominal have been reported. The majority of the intrathoracic ectopic or accessory liver lobes were connected to the orthotopic liver by means of a small pedicle that pierced the diaphragm or passed through a small hiatus (Chen et al.). From intra abdominal sites the most frequent site where are found the majority of ectopic livers is the gallbladder (Tejada & Danielson; Arakawa et al.; ^{Sakarya et al., 2002}; ^{Acar et al., 2002}; ^{Catani et al., 2011}; Martinez et al.; ^{Bal et al., 2015}; ^{Yahya et al., 2016}; ^{Karaca et al., 2016}). Occasionally ectopic liver have been found in other organs like stomach (^{Huang et al., 2015}, ^{Barazza et al., 2016}), in the upper pole of the spleen (^{Zonca et al., 2013}), in the ligamentum hepato-umbilicalis (^{Lara-Díaz et al., 2011}; ^{Vaideeswar et al., 2011}; Zonca et al.), in the pancreas (^{Li et al., 2017}), kidney (^{Merve & Scheimberg 2014}), left adrenal gland (^{Hashimoto et al., 1997}) or have been found as intracaval floating mass (^{Morris et al., 2012}; ^{Rafiei et al., 2012}). From the review of the literature a few cases of ectopic liver have been reported in the walls of stomach as submucosal tumors (Huang et al.) or attached to serosa of stomach (Barazza et al.). To our knowledge, only one case attached to serosa of stomach (Barazza et al.) has been reported as a subdiaphragmatic mass adjunct to the fundus of stomach, similarly to our case which confirms the fact that this location of ectopic liver is very rare.

The differential diagnosis of a mass localized or attached to stomach wall is broad and includes both benign and neoplastic formations like leiomyoma, schwannoma, neurofibroma, GIST, lymphoma, and carcinoid or metastases and CT examinations are very important for the diagnosis, especially of unusual gastric tumors and tumor-like lesions (^{Lin et al., 2017}). In our case the mass had the characteristics of an ectopic liver because of the similar structure with the mother liver and the presence of the stalk which connected it with the left lobe of the liver and which contains the blood vessels. Furthermore this diagnosis was confirmed intraoperatively during surgery.

CONCLUSION

In summary, ectopic liver is a rare and commonly incidentally discovered developmental abnormality, especially those in the left hypocondrium attached to the stomach wall. Imaging examinations are of great importance in the differential diagnosis and despite the low incidence of ectopic liver radiologist should be aware of this entity.