Anaerobic liver abscesses as initial presentation of silent colonic cancer

Abstract

Background

Rarely, multiple liver abscesses caused by anaerobic organisms are the presenting form of unsuspected colonic cancer in the absence of liver metastases.

Case outline

A 68-year-old man was admitted with abdominal pain, fever and chills. Imaging scans and repeated cytology yielded a diagnosis of multiple liver abscesses. Pus cultures grew Peptostreptococcus anaerobius, Bacteroides melaninogenicus and Peptostreptococcus spp. A search for the underlying cause led to the discovery of an adenocarcinoma of the sigmoid colon. After a 12-month postoperative follow-up, the patient is free of hepatic metastases.

Discussion

Anaerobic liver abscesses should always alert the clinician to possible silent colonic carcinoma.

Introduction

The clinical incidence of colorectal cancer varies between 30 and 50 cases per 100000 inhabitants ¹, whereas pyogenic liver abscess has been reported as between 6 and 22 cases per 100000 hospital admissions ².

Pyogenic hepatic abscess is an exceedingly uncommon presentation of colonic cancer, with only a few reports in the absence of liver metastases ³,⁴,⁵. We describe a patient with this rare clinical presentation.

Case report

A 68-year-old man was admitted with right upper abdominal pain, high fever and chills lasting for 1 week. He denied any change in bowel habits or rectal bleeding. Physical examination revealed pallor, sweating, tachycardia, a temperature of 39°C, right upper quadrant tenderness and 3 cm hepatomegaly. Laboratory data showed leucocytosis, anaemia and cholestasis. Hepatitis and echinococcus serology were negative, as were blood cultures. Abdominal ultrasound (US) scan (Figure 1) and computed tomography (CT) scan (Figure 2) revealed two lesions in the left lobe of liver and another image in the right lobe, which were diagnosed as abscesses.

Figure 1. .

Abdominal ultrasound showing two contiguous lesions of mixed echogeneity in the left lobe of the liver.

Figure 2. .

CT scan revealing three hypo-dense lesions, two in the left tobe and one in the right lobe of the liver, representing multiple liver abscesses.

The patient received antimicrobial treatment with amoxicillin/clavulanic acid that proved ineffective. Aspiration of the larger abscess under US guidance showed frank pus, and the cytological examination revealed no malignant cells. Imipenem was substituted for amoxicillin/clavulanic acid. Cultures of the liver lesions grew Peptostreptococcus anaerobius, Bacteroides melaninogenicus and Peptostreptococcus spp. The patient's condition remained toxic, and a US-guided percutaneous catheter drainage was placed in the larger abscess cavity of the left lobe. In addition, the other two abscess cavities were aspirated. Repeated cytology of the left hepatic lesion confirmed the absence of malignant tissue. Serial US scans showed progressive improvement in the liver lesions paralleling subjective and clinical improvement. After 29 days the patient was discharged.

In the search for an underlying cause, a barium enema and a colonoscopy revealed an irregular stenotic lesion in the sigmoid colon. Biopsies disclosed adenocarcinoma, and the patient underwent sigmoid colectomy. Histopathological examination confirmed adenocarcinoma of the sigmoid colon (Dukes’ stage B). The postoperative course was uneventful, and the patient remains free of disease at 1 year.

Discussion

Anaerobes are recovered from between 15% and 46% of pyogenic liver abscesses ⁶. In most of the intra-abdominal infections for which they are responsible, their portal of entry is the gastrointestinal tract ⁷. We believe that the route of infection in our patient was portal bacteraemia, because there was no evidence of ascending biliary infection on imaging. No evidence of metastasis was found on the two cytological examinations, at surgical exploration, nor yet during follow-up. Invading anaerobic organisms must have found their portal of entry through a break in the mucosal barrier near the tumour, possibly owing to diminished host resistance due to carcinoma ⁸.

Our patient did well with appropriate antibiotic treatment and a combination of percutaneous catheter drainage and needle aspiration, a result consistent with that of other reports ²,⁹,¹⁰.