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J Hepatobiliary Pancreat Surg (2006) 13:252255DOI 10.1007/s00534-005-1044-6

Case reports of interest

Amebic liver abscess rupturing into the lesser omentum spaceYoichiro Nushijima1, Hideyuki Ishida1, Yasunori Watanabe1, Kazunori Nakaguchi1, Katsuaki Nakanishi2,Yoshihiko Hoshida3, and Toshiyuki Kabuto1

1 Department of Surgery, Osaka Seamens Insurance Hospital, 1-8-30 Chikkou, Minato-ku, Osaka 552-0021, Japan2 Department of Radiology, Osaka Seamens Insurance Hospital, Osaka, Japan3 Department of Pathology, Osaka University, Suita, Japan

but had experienced no other relevant symptoms, suchas abnormal pain, fever, or diarrhea in the previousyear. On admission, he was 162cm tall and weighed

59kg. His body temperature was 37.3C and his arterialblood pressure was 112/62mmHg. A physical examina-tion revealed a palpable hard mass with a smooth sur-face in the left upper quadrant of the abdomen, whichwas difficult to move. Laboratory examination revealeda hematocrit of 28.7%, a white blood cell count of 7100/mm3 with 75.0% polymorphonuclear leukocytes, anda C-reactive protein concentration of 10.2mg/dl. Liverfunction and the serum levels of carcinoembryonic anti-gen, carbohydrate antigen 19-9 and -fetoprotein werewithin normal ranges. Abdominal ultrasonography(US) revealed an isoechoic mass with a hypoechoic areameasuring 6.5 cm in diameter and bordering the body of

the pancreas (Fig. 1). A pre-contrast computed tomo-graphy (CT) scan revealed a heterogeneous low-densitymass measuring 5cm in diameter between the body ofthe pancreas and the left lobe of the liver. The areacontacting the mass in the left lobe of the liver hadlow density (Fig. 2). The early phase of the contrast-enhanced CT scan revealed a strongly enhanced marginof the mass and no enhancement of the inside of themass. The area contacting the mass in the left lobe ofthe liver was also shown as low density (Fig. 3). The latephase of the contrast-enhanced CT scan revealed thatthe inside of the mass was still not enhanced but the

area contacting the mass in the left lobe of the liver wasenhanced and had the same density as the surroundingnormal liver (Fig. 4). T1-weighted magnetic resonanceimaging (MRI) revealed a low-intensity mass (Fig. 5).T2-weighted MRI revealed a mildly high-density mass,with a high-density area contacting the mass in the leftlobe of the liver (Fig. 6). Abdominal angiographyshowed a small shift surrounding the tumor, but notumor stains (Fig. 7). The preoperative diagnosis was apancreatic tumor containing an abscess. A tumor ofunknown origin containing an abscess or an unknown

Abstract

A case of an amebic abscess localized in the lesser omentum isreported. There was no sign of a liver abscess in the imagingexamination or the operative findings. However, it is likely

that the amebic infection occurred after a liver abscess rup-tured into the abdominal cavity. Early diagnosis and therapyare required when an abscess of unknown origin borders theliver, given the possibility of amebic abscess.

Key words Entamoeba histolytica Amebic abscess Lesseromentum

Introduction

Amebiasis is caused by Entamoeba histolytica, and in-

fection is acquired by ingesting food or water containingthe cysts of this protozoan. The adult trophozoite colo-nizes the large intestine and causes amebic colitis. Thetrophozoites often enter the circulation, where they arefiltered in the liver and produce abscesses.1 Here, wepresent the first case of an amebic liver abscess ruptur-ing into the space in the lesser omentum. The imagingexaminations revealed no sign of a liver abscess andtherefore it was diagnosed preoperatively as a pancre-atic tumor containing an abscess.

Case report

A 60-year-old Japanese man presented at hospitalbecause of abdominal distention on April 5, 2004. Hisfamily medical history was uneventful. He had beensuffering from abdominal distention since March 2004

Offprint requests to: Y. NushijimaReceived: May 9, 2005 / Accepted: August 3, 2005

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age operation. A pathological examination on April 30,2004, revealed that the abscess partially consisted of agranulomatous wall in the pancreatic parenchyma, andmature trophozoites of E. histolytica were detected inits exudative contents (Fig. 9). We confirmed thepatients previous history, and it was revealed that hehad visited Taiwan in January 2004. The patients serumwas weakly positive for E. histolytica when tested with adetection kit (Amoeba-Spot IF, Biomerieux, Tokyo,Japan), but the patients stool contained no parasites or

Fig. 1. Abdominal ultrasonography revealed an isoechoicmass with a hypoechoic area inside measuring 6.5cm in diam-eter bordering the body of the pancreas (Panc.)

Fig. 3. The early phase of the contrast-enhanced CT scanrevealed a strongly enhanced margin of the mass and no en-hancement of the inside of the mass. The area contacting themass in the left lobe of the liver was also low density

abdominal abscess were considered as differential diag-noses. We conducted a laparotomy on April 23, 2004.The operative findings revealed no tumors and only anabscess. The abscess wall was composed of the left lobeof the liver, the lesser curvature of the stomach, thebody of the pancreas and the second portion of theduodenum, which was considered as being in the lesseromentum (Fig. 8). Intraoperative examination of theabscess wall revealed the presence of non-specificgranulomatous tissue. The patient underwent a drain-

Fig. 2. A pre-contrast computed tomography (CT) scan re-vealed a heterogeneous low-density mass measuring 5cm indiameter between the body of the pancreas and the left lobe ofthe liver. The area contacting the mass in the left lobe of theliver was low density (arrow)

Fig. 4. The late phase of the contrast-enhanced CT scan re-vealed that the inside of the mass was still not enhanced butthe area contacting the mass in the left lobe of the liver wasenhanced and had the same density as the surrounding normalliver

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254 Y. Nushijima et al.: Amebic abscess in lesser omentum

ova. The patient was treated with metronidazole andresponded well. He was discharged from hospital onJune 2, 2004. A contrast-enhanced CT scan 2 weeks

after the operation showed that the mass had disap-peared completely. The pancreatic body and left lobe ofthe liver were almost intact.

Discussion

This is the first report of an amebic liver abscess local-ized in the lesser omentum. In this case, neither theimaging examination or the operative findings revealedan abscess in the patients liver, so there was the possi-

Fig. 5. T1-weighted magnetic resonance images (MRI) showa low-intensity mass

Fig. 6. T2-weighted MRI revealed a mildly high-density massand a high-density area contacting the mass in the left lobe ofthe liver

Fig. 7. Arterial phase superior mesenteric angiogram (left)and left gastric angiogram (right) showed a small shift sur-rounding the tumor (arrows), but no tumor stains

Fig. 8. Operative findings revealed that the abscess wall wascomposed of the left lobe of the liver, the lesser curvature ofthe stomach, the body of the pancreas and the second portionof the duodenum

bility of direct amebic infection in the abdominal cavity.

However, it is known that extra-intestinal infection iscaused when trophozoites in amebic colitis enter thecirculation. The liver is a definitive organ that filtersthe portal circulation, and therefore liver abscess is themost common extra-intestinal manifestation of amebia-sis.1 It is likely that the abscess in this case occurred byrupture of the amebic liver abscess, which may havebeen small enough after rupture to evade detection.There have been many cases of an amebic liver abscessrupturing into the abdominal cavity and causing gener-alized peritonitis.2 Rare cases have been reported of

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rupture into the pericardial cavity,36 the pleuralcavity,7,8 the biliary tract,9,10 a hepatic aneurysm,11 theretroperitoneum,12 the stomach,13 and the greater omen-tum,8 but there have been no reports of rupture into thelesser omentum producing a localized abscess.

In the present case, the patient had no symptoms thatwere useful for making a diagnosis of amebic colitis oramebic liver abscess, for example diarrhea, abdominalpain, nausea, vomiting, abdominal malaise, appetiteloss, general fatigue, body weight loss, or bloody stool

with mucus. The mass was located between the liver andthe pancreas, as if the mass had originated in the pan-creas and was protruding into the liver. Although imag-ing examinations revealed signs of liver abscess in otherpreviously reported cases,313 the present case showedno evidence of a liver abscess (Figs. 14). It is vital toconsider the possibility of amebiasis when an abdominalabscess of unknown origin borders the liver. The tradi-tional therapy for a ruptured amebic liver abscess hasbeen immediate operative drainage and complementarydrug therapy. Percutaneous catheter drainage is now amajor player in the management of pyogenic hepaticabscess,14 but its role in the management of amebic ab-

scesses remains controversial.8

In conclusion, we treated a patient with an amebicabscess localized in the lesser omentum. Early diagnosisand therapy are required when an abscess of unknownorigin borders the liver given the possibility of amebicabscess.

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Fig. 9. Histologically, the abscess partically consisted of agranulomatous wall in the pancreatic parenchyma (H&E,25).Inset: a mature trophozoite ofE. histolytica was detectedin the abscesss exudative contents (arrow) (H&E, 200)