History and exam

Key diagnostic factors

common

presence of risk factors

Key risk factors include exposure in endemic areas, institutionalisation (particularly of those with intellectual disability), men who have sex with men, and male sex.

diarrhoea

Patients may have had diarrhoea for 1 week or more at the time of presentation.[1][10]​​[28]​​Entamoeba histolytica diarrhoea may be watery or bloody, and be clinically-indistinguishable from diarrhoea caused by inflammatory bowel disease or a variety of other enteropathogens.[7]

Less than 50% of patients with a liver abscess will have diarrhoea at time of presentation, although a past history of diarrhoea or dysentery is common.

Other diagnostic factors

common

generalised abdominal pain

Present in most patients with amoebic colitis.[7]

right upper quadrant abdominal pain

May indicate an amoebic liver abscess.[1][5][7]

weight loss

About half of patients may report weight loss due to the subacute nature of the disease.[1][7]

cough

Present in up to half of patients with liver abscess.[7]​ Caused by phrenic nerve irritation and/or pleural effusion.[1]

uncommon

fever

Rare in intestinal infections but common in extraintestinal infections, such as liver and brain abscesses.[1][7]

altered mental status or limb weakness

Present with amoebic brain abscess.[1][3]​​​[5]​​

dyspnoea

Extension of liver abscess can cause pleural or pericardial effusion.

guarding and rebound tenderness of the abdomen

Present with acute necrotising colitis, toxic megacolon, or peritonitis due to amoebiasis.[1]

jaundice

More common with pyogenic than amoebic liver abscess.[1][5]

right lung decreased air entry and percussion note

If pleural effusion is present.

Risk factors

strong

exposure in endemic areas

Most patients with amoebiasis will have visited or resided in an endemic area within the previous 12 months.[1][2][4][21][22]

institutionalisation (particularly of people with intellectual disability)

Outbreaks in institutions for people with intellectual disability have been reported.[2][3]​​​[4][5]​​

men who have sex with men

There is an increased prevalence of sexually transmitted amoebiasis among men who have sex with men.[2][7]​​[12][19]​​​​​ Commensal amoeba Entamoeba dispar is responsible for most infections, but Entamoeba histolytica infections also occur in this population.[2][3]​​​​[4][5]​​​​​​​[12][23]

oral-anal sexual contact

Oral-anal sexual contact is a risk factor for sexual transmission of amoebiasis.[3][12][19]​​ ​Clustering of Entamoeba histolytica strains has been found due to oral-anal sexual contact.[18]

Those with multiple partners, including commercial sex workers, may be at increased risk.[14][18]​​

male sex

Ninety percent of amoebic liver abscesses are found in men aged 20 to 40 years.[1][2][3]​​​​[4][5]​​

weak

HIV infection, past or current syphilis infection

Comorbid HIV infection and past history or positive serology of syphilis have been associated with increased prevalence of sexually transmitted amoebiasis. The reasons for these associations are unclear, but may reflect similar risk factors for these infections.[11][14][15][24]​​ The strength of these associations may depend on the local epidemiology. 

Use of this content is subject to our disclaimer