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142 Parasitic Infestations of Surgical Importance in Children
Amoebic Colitis Imaging studies
Amoebic colitis affects all age groups, but its incidence is strikingly • Chest radiography may reveal an elevated right hemidiaphragm and
high in children 1–5 years of age. The clinical features depend upon a right-sided pleural effusion in patients with amoebic liver abscess.
the transmural as well as the longitudinal extent of the disease. The
onset may be insidious, with nonspecific dysenteric symptoms, and • Ultrasonography is preferred for the evaluation of amoebic liver
is often confused with gastroenteritis or herbal intoxication. Severe abscess due to its low cost, rapidity, and lack of adverse effects. A
amoebic colitis in infants and young children tends to be rapidly pro- single lesion is usually seen in the posterosuperior aspect of the right
lobe of the liver. Multiple abscesses may occur in some patients.
gressive with frequent extraintestinal involvement and high mortality
rates. Rectal loss of blood and mucus is a frequent but not constant • Computed tomography (CT) and magnetic resonance imaging
finding and may raise suspicion of intussusception or typhoid. The (MRI) may be done in selected cases.
association between progressive disease and clinically overt malnutri- Other tests
tion is striking, and the relationship may be provocative. The passage
of large volumes of malodourous stools with slough from the mucosa • Leucocytosis without oesinophilia is observed is 80% of cases.
in a child with preexisting malnutrition suggests amoebic colitis. • Mild anaemia may be noted.
Occasionally, amoebic dysentery is associated with sudden onset of
fever, chills, and severe diarrhoea, which may result in dehydration • Liver function tests reveal elevated alkaline phosphatase levels (in
and electrolyte disturbances. 80% of patients), elevated transaminase levels, mild elevation of
Progressive disease in children is manifested by increasing serum bilirubin level, and reduced albumin levels.
abdominal distention with discomfort, tenderness, and toxaemia. • The erythrocyte sedimentation rate is elevated.
Classical signs of peritonitis may develop very late, if at all, due to
omental wrap. Medical Treatment
Asymptomatic infections are not treated in endemic areas. However,
Amoebic Liver Abscess in nonendemic areas asymptomatic infection should be treated because
Amoebic liver abscess, a serious manifestation of disseminated infec- of its potential to progress to invasive disease. Luminal agents that are
tion, is uncommon in children, although some cases have been reported. minimally absorbed by the gastrointestinal (GI) tract (e.g., paromomy-
Although diffuse liver enlargement has been associated with intestinal cin) are best suited for such therapy.
amoebiasis, liver abscess occurs in <1% of infected individuals and Metronidazole is the mainstay of therapy for invasive amoebiasis.
may appear in patients with no clear history of intestinal disease. This Tinidazole is being used for intestinal or extraintestinal amoebiasis.
contrasts with the high incidence of cases of amoebic liver abscess Nitroimidazole therapy leads to clinical response in approximately
(61%) seen in the surgical ward in Natal, South Africa, which occurred 90% of patients with mild to moderate colitis. Chloroquine has also
in association with active amoebic colitis. been used for patients with hepatic amoebiasis. Intraluminal parasites
Numerous small abscesses may coalesce to form large abscesses, are not affected by nitroimidazole therapy. Therefore, nitroimidazole
which expand towards the surface and may rupture, giving rise to therapy should be followed by treatment with a luminal agent such as
amoebic peritonitis. Amoebic liver abscess may occur months to paromomycin to prevent a relapse.
years after exposure, so a high index of suspicion is very important. Broad-spectrum antibiotics may be added to treat bacterial
In children, fever is the hallmark of amoebic liver abscess and is superinfection in a case of fulminant amoebic colitis and suspected
frequently associated with abdominal pain, distention, and enlargement perforation. Bacterial coinfection with amoebic liver abscess has
and tenderness of the liver. Changes at the base of the right lung, such as occasionally been observed (both before and as a complication of
elevation of the diaphragm and atelectasis or effusion, may also occur.
drainage), and adding antibiotics to the treatment regime is reasonable
Investigations in the absence of a prompt response to nitroimidazole therapy.
Stool examination Surgical Treatment
Light microscopy examination of a fresh stool smear for trophozoites Surgical intervention is required for acute abdomen due to perforated
that contain ingested red blood cells (RBCs) is rather insensitive. It is amoebic colitis, massive GI bleeding, or toxic megacolon. Toxic mega-
positive in 10% of patients, showing the presence of haematogenous colon is rare, however. Surgical attempts to correct amoebic bowel
amoebae. It cannot distinguish other species of Entamoeba from E. his- perforation or peritonitis should be avoided, although some patients
tolytica. Fulminant amoebic colitis or its complications may exist with may benefit from peritoneal lavage.
a negative stool parasitology if treatment has started prior to referral. Unlike pyogenic liver abscess, amoebic liver abscess generally
Stools for examination must be fresh when examined or be preserved in responds to medical therapy alone, and drainage is seldom necessary.
polyvinyl alcohol for later microscopy. Material from rectal scrapings When necessary, imaging guided percutaneous treatment (needle
has also proved most helpful. An enzyme immunoassay kit to specifi- aspiration or catheter drainage) has replaced surgical intervention as the
cally detect E. histolytica in fresh stool specimens is now commercially procedure of choice for reducing the size of an abscess. The indications
available in specialised centres. for drainage of amoebic liver abscess include the presence of left-lobe
Serologic studies abscess (>10 cm in diameter), and impending rupture and abscess that
Serum antibodies against amoebae are present in 70–90% of individu- does not respond to medical therapy within 3 to 5 days.
als with symptomatic intestinal E. histolytica infection. Antiamoebic Ascariasis
antibodies are present in as many as 99% of individuals with liver Ascariasis is the parasitic infestation by the largest intestinal nematode
abscess who have been symptomatic for longer than a week. However, of man, which is found worldwide. It is now a significant public health
serologic tests do not distinguish new from past infection because problem in many parts of the world. The organism maintains an ideal
the seropositivity persists for years after an acute infection. Several host-parasite relationship without any observable harm in the vast
methods, such as indirect haemoagglutination antibody (IHA), enzyme- majority of individuals, but heavy parasitisation of the intestinal tract
linked immunosorbent assay (EIA), and immunodiffusion (ID) tests are by Ascaris lumbricoides may be associated with nutritional disturbanc-
now commercially available in specialised centres. es and, more important, intestinal obstruction or perforation.