Entamoeba histolytica - Clinical manifestations
Clinical manifestations of Entamoeba histolytica
The clinical manifestations of Entamoeba histolytica can be variable from asymptomatic carriers to intestinal amoebiasis to extra-intestinal invasive amoebiasis involving multiple organs such as lungs, heart, spleen, brain, and stomach.
Intestinal amoebiasis
Asymptomatic intestinal amoebiasis
Symptomatic intestinal amoebiasis
Asymptomatic intestinal amoebiasis
Around 10% of Entamoeba histolytica are asymptomatic intestinal amoebiasis where the host shows no signs of infection but passes the cysts in the feces.
Symptomatic intestinal amoebiasis
In these cases of Entamoeba histolytica symptomatic intestinal amoebiasis, the symptoms may range from mild diarrhea (amoebic colitis) to severe hemorrhagic dysentery (acute amoebic dysentery).
Complications may or may not be present in symptomatic intestinal amoebiasis.
Non-dysenteric amoebic colitis
is usually chronic
symptoms include mucus diarrhea, weight loss, abdominal pain, flatulence
the presence of small ulcers and less inflammation in the colon
Entamoeba histolytica is present in the feces
specific antibodies can be found in the serum
Acute amoebic dysentery
the most common form of infection
symptoms might be gradual or acute and include abdominal pain, tenderness, stool with visible blood and mucus, rectal tenesmus, tender hepatomegaly
fever may be seen, but is uncommon, only occurring in less than one-third of the cases
Complications
Toxic megacolon:
if treatment with anti-amoebic drugs is unachievable to be drug-resistant, colectomy is required
occurs in 0.5 % of the cases
Fulminant amoebic colitis
high mortality
occurs mostly in pregnant women, malnourished individuals, or immunocompromised / individuals under corticosteroid treatment
symptoms include high fever (104-105°F), leucocytosis, abdominal pain, severe bloody mucosal diarrhea, rectal tenesmus
necrotic involvement is seen in the colon with colonic perforation as well as frequent hemorrhage
Amoeboma
pseudo-tumoral and localized chronic infection of the rectum or caecum occurs
single lesion or multiple lesions may occur
the lesion may contain a limited number of trophozoites while antibodies against the parasite are seen in the patient's serum
Other complications
peritonitis
perianal ulceration
urogenital infection
colonic stricture
intussusception
hemorrhage
Extra-intestimal amoebiasis
Extra-intestinal amoebiasis occurs after dissemination of the intestinal Entamoeba histolytica and depends on the organ involved such as:
Hepatic amoebiasis
Pulmonary amoebiasis
Cerebral amoebiasis
Genitourinary amoebiasis
Splenic amoebiasis
Cutaneous amoebiasis
Amoebic peritonitis
Amoebic pericarditis
Hepatic amoebiasis
Hepatic amoebiasis caused by Entamoeba histolytica with hepatic involvement (non-suppurative amoebic hepatitis) may progress to form an amoebic liver abscess or suppurative amoebic hepatitis.
Non-suppurative amoebic hepatitis
occurs during colitis
results from non-specific peripheral inflammation of the liver
syndromes include tender hepatomegaly, fever, right upper quadrant pain, and leucocytosis in individuals with dysentery
Amoebic liver abscess (ALA)
Amoebic liver abscess (ALA) is the most common type of extra-intestinal amoebiasis (10-50% of invasive cases)
its characteristic is a sudden onset of high fever, right upper abdominal pain as well as tenderness
the abdominal pain, which is intense and constant, occurs due to stretching of the liver capsule. The pain radiates to the right scapula and right shoulder which may become pleuritic and increases when the patient lies on the right side
other symptoms include anorexia, vomiting, nausea, fatigue, weight loss
sometimes mild jaundice is observed
if the Entamoeba histolytica abscess is located in the right lobe of the liver, which is more common, it is present in its posterior, superior, and external surfaces.
In cases of abscess being present in the left lobe, the pain occurs in the epigastric area which is then radiated to the left shoulder
ALA usually heals without the formation of scar tissue
if after necrosis, fibrotic tissue is absent, it is characteristic of this manifestation
Complications of ALA:
About 40% of amoebiasis death occurs due to the complication of ALA
Complications of ALA caused by Entamoeba histolytica include:
* rupture of liver abscess into pleural space and into the abdomen, esophagus, stomach, or retroperitoneal area.
* Secondary bacterial infection
* serious but less common complications include amoebic pericarditis, pneumo-pericardium – especially of the left lobe
Pulmonary amoebiasis
Pulmonary amoebiasis is an uncommon but serious form of complication of ALA
occurs mostly due to direct extension from liver abscess rather than due to dissemination from the intestine through blood
occurs in 10% of ALA patients
the rupture of a superior right upper lobe abscess through the diaphragm results in this complication
severe chest pain radiating to the right shoulder, non-productive cough, and dyspnoea is a symptom of pulmonary amoebiasis
sputum contains Entamoeba histolytica trophozoites
Cerebral amoebiasis
Cerebral amoebiasis is uncommon, observed in 0.66-4.7% of patients with ALA
a single, small abscess located in the cerebral hemisphere
abrupt onset which is characterized by focal neurological signs and altered consciousness
brain biopsy shows Entamoeba histolytica trophozoites
patients with this condition may suffer rupture or involvement of the cerebellum which may result in death within 12-72 hours
Genitourinary amoebiasis
Genitourinary amoebiasis involves infestation of the Entamoeba histolytica trophozoites in the kidney or reproductive organs
this condition may arise through direct extension from ruptured amoebic liver abscess, spread from lungs, liver lesions through blood, or extensions through lymphatics
when genital organs are involved, males may acquire infection by vaginal or anal intercourse where legions such as ulcers produce discharge. In females, amoebiasis of the vagina/cervix may be caused by rector-vaginal fistulas