Single and multiple liver abscesses in adults in Delhi are amoebic in origin: a clinical and microbiological study

Introduction

Liver abscess is an important gastrointestinal disorder in the tropics. It is usually amoebic or pyogenic and rarely tubercular or fungal. It is the most common extraintestinal manifestation of amoebiasis. ¹ Amoebic abscesses generally do not require drainage and amoebicidal agents alone are effective in most cases ² and should be distinguished from pyogenic abscesses which frequently require drainage. This study compares the clinical, radiological and biochemical profile of patients with microbiological findings in order to identify the aetiology of liver abscesses.

Methodology

This cross-sectional study reports on 25 patients who presented to the surgical emergency department from February to September 2012 and who were diagnosed with liver abscess. With informed consent, patients were investigated by: hemogram; amoebic serology; ultrasound guided pus aspiration followed by Gram’s staining; Ziehl-Neelsen staining for acid-fast bacillus (AFB); microscopy for Entamoeba histolytica; pyogenic and anaerobic cultures; and examinations of stools for E. histolytica. Amoebic liver abscess (Group A) was diagnosed based on positive serology (enzyme-linked immunoadsorbent assay, ELISA) and/or evidence of trophozoites in the pus and pyogenic abscess (Group B) based on a positive pus culture. Cases with positive outcomes on both tests were labelled as mixed abscesses (Group C). The fourth group contained patients where no cause could be identified. Data were analysed using descriptive statistics and the Mann Whitney U test.

Intravenous ciprofloxacin and high dose metronidazole were administered for at least 7 days and patients were discharged on oral metronidazole and chloroquine for 14 days.

Results

Twenty-five adult patients were studied and the mean age was 45.72 years (range = 18–82 years). Right upper quadrant (RUQ) pain was present in all, followed by fever in 24 (96%) and chills in 15 (60%). Thirteen (52%) had isolated amoebic liver abscess (Group A) and seven (28%) had amoebic abscess with secondary pyogenic infection (Group B). Only one (4%) patient had isolated pyogenic liver abscess (Group C) and four (16%) were indeterminate (Group D) (Table 1).

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Table 1.

Number and proportion of abscesses of each type.

Type of abscess	No. (n = 25)	%
Amoebic only	13	52
Mixed	7	28
Pyogenic	1	4
Indeterminate	4	16

Four (16%) had anaemia (haemoglobin <8 g%) and all had amoebic pathology. Bilirubin >2 mg/dL was found in only seven (28%) patients, all of whom had amoebic pathology. Serum glutamic oxalo-acetic transaminase (SGOT) and serum glutamic pyruvic transaminase (SGPT) were <three times normal in 19/25 (76%) patients. Fifteen (60%) had alkaline phosphatase (ALP)<300 U/L. Abscesses were predominantly right lobed (18/25, 72%), 16/25 (64%) were solitary (Table 2), 5/13 purely amoebic abscesses (38.5%) were multiple. All seven mixed abscesses were >400 cc in size.

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Table 2.

Number of abscesses on ultrasound and comparison between groups.

Type of abscess
Overall		Amoebic		Mixed		Pyogenic		Indeterminate
No. seen on ultrasonography	No.	%	No.	%	No.	%	No.	%	No.	%
Solitary Multiple	16 9	64 36	8 5	61.5 38.5	6 1	85.7 14.3	0 1	0 100	2 2	50 50

Pus culture was positive in eight cases and three (37.5%) grew Escherischia coli. Staphylococcus aureus was isolated from pyogenic abscess. Ziehl-Neelsen (ZN) staining, anaerobic culture and stool examination were negative in all patients. All responded well to treatment.

Discussion

Liver abscess remains a surgical problem with a high mortality rate, emphasizing the crucial role of timely diagnosis and appropriate management. Amoebic liver abscess is the predominant type in tropics (40%–50%). ³ In our study, 20/25 (80%) patients had amoebic pathology, 13 (52%) being purely amoebic while seven (28%) had secondary bacterial infection (mixed abscesses). The four indeterminate abscesses had biochemical similarities with amoebic abscesses. Thus, in an endemic country such as India, liver abscess may be presumed to have amoebic pathology.

The most common presenting symptoms were RUQ pain and fever. Studies have reported that pyogenic abscesses cause anaemia, jaundice, leucocytosis and deranged liver function tests (LFTs) are more common, ³ while some believe that patients with amoebic abscesses are more acutely ill with fever and RUQ. ⁴ In our study, the patient with a pure pyogenic abscess did not have anaemia, jaundice or deranged LFTs. Stool examinations were negative for E. histolytica in all patients which implies that an intestinal infection is not always present in such patients.

Amoebic liver abscess is traditionally described as a solitary, right lobe abscess ⁵ and pyogenic abscesses are usually multiple. ⁶ However, the reverse is not uncommon. ⁷ In our study, 6/20 patients (30%) with amoebic pathology had multiple abscesses. Thus, multiple abscesses do not necessarily imply a pyogenic origin.

Mixed abscesses were significantly larger (P = 0.03); 5/7 had a volume of >900cm ³ , showing that larger abscesses were more likely to lead to secondary bacterial infection. E. coli was the most common organism alongside amoebiasis (3/8 cases, 37.5%).

Conclusion

Liver abscesses in adults in Delhi are predominantly amoebic and solitary. Contrary to expectations, most multiple abscesses were also amoebic. Mixed abscesses are significantly larger and commonly harbour Gram negative rods, supporting portal circulation as the route of spread for both the organisms. Thus, multiple abscesses do not necessarily mean pyogenic and the presence of bacteria does not imply a primary pyogenic source.