AMOEBA Amebiasis is an infection caused by the protozoal organism Entamoeba histolytica and includes amebic colitis and liver abscess.Transmission usually occurs by food-borne exposure, particularly when food handlers are shedding cysts or food is cultivated in feces-contaminated soil, fertilizer, or water. Less common means of transmission include contaminated water, oral and anal sexual practices, and direct rectal inoculation through colonic irrigation devices.Pathophysiology: -E histolytica is a pseudopod-forming, nonflagellated protozoal parasite that exerts a lytic effect on tissue, a characteristic for which the organism is named. -Host cells are killed via the induction of apoptosis; therefore, the parasite does not kill the host cell but rather induces its self-destruction.-Incubation period is 2-26 days with majority 14 days. Infective dose >103 organisms- Ingestion of the cyst is followed by excystation in the small bowel and trophozoite colonization of the colon. Upon colonization of the colonic mucosa, the trophozoite may encyst and be excreted in the feces or it may invade the intestinal mucosal barrier, thereby gaining access to the circulation, resulting in involvement of the liver, lung, and other sites. -Whether infection results in colonization or invasion, the E histolytica strain and its interaction with bacterial flora; host genetic susceptibility; and factors such as malnutrition, sex, age, and immunocompetence may influence the infection.Liver involvement occurs following invasion of E histolytica into mesenteric venules. Amebae then enter the portal circulation and travel to the liver where they typically form large abscesses. The abscess contains acellular proteinaceous debris, which is thought to be a consequence of induced apoptosis and is surrounded by a rim of amebic trophozoites invading the tissue. The right lobe of the liver is more commonly affected than the left lobe. This has been attributed to the fact that the right lobe is supplied predominantly by the superior mesenteric vein, whereas the left lobe is supplied by the splenic vein.NB. Patients with amoebic dysentery are not infective-passing trophozoites.Morbidity-E.histolytica probably is second only to malaria as a protozoal cause of death. -Asymptomatic intestinal infection occurs in 90-99% of infected individuals.- Most infected individuals eliminate the parasite from the gut within 12 months; however, colonization with E histolytica carries a low but definite risk of developing into invasive amebiasis.-Amebic colitis is complicated by fulminant or necrotizing colitis with high mortality rate.

-Amebic liver abscess is complicated by intraperitoneal rupture.Sex: -Amebic liver abscess is 7-12 times more common in men than in women, although the sex distribution is equal in children.Amebic colitis affects both sexes equally.Age:-Young children appear to be at higher risk for fulminant invasive disease, resulting in a higher mortality rateClinical presentationHistory: Amebic colitis1 .Dysentry Mobile dysentery as patients not usually very sick looking as in bacillary dysentery where patients are bed ridded.2.Fulminant colitisFulminant or necrotizing colitis is the most serious manifestation, has high a mortality rate. Predisposing factors for fulminant colitis include Poor nutrition, Pregnancy, corticosteroid use, very young age3.Chronic post amoebic colitis-Sclerotic changes in the bowel-Irritable bowel-No amoeba in the stool4.Amoeboma of the colon or rectum-Can be ,mistaken for colorectal cancer but responds well by medical treatment 5.PerfoarationAmoebia peritonitisPericolic abcessInternal intestinal fistula.Amoebic dysentery may present as:1) Several weeks of abdominal pain, diarrhea, and bloody stools.2) Fever is uncommon and occurs in approximately 10-30% of patients.3) Weight loss is a common complaint and may be accompanied by symptoms of volume depletion (eg, orthostasis).Amebic liver abscess1) Fever and right upper quadrant abdominal pain.Unlike amebic colitis, amebic liver abscess is associated with fever in 85-90% of patients.2) Most do not have concomitant colitis, although a history of dysentery may be obtained.-History of alcohol abuse is commonClinically, almost all patients reveal an enlarged liver and tenderness in the right upper quadrant. Polymorphonuclear leukocytosis is usually 15,000 to 20,000/mL, and there is moderate anemiaPleuropulmonary amebiasis-Rare but serious complication of amebic liver abscess, -Caused rupture of a superior right upper lobe abscess with erosion through the diaphragm.-Patients with this complication present with cough, pleuritic chest pain, dyspnea, and, occasionally, necrotic sputum.

Intraperitoneal ruptureFrom amebic liver abscess occurs. These patients can present with a rigid abdomen that may be diagnosed erroneously as a perforated viscus.Cerebral amebiasis -Is a rare cause of brain abscess and is characterized by an abrupt onset of mental status change and/or focal neurologic deficits. -Progression to death occurs over 12-72 hours without adequate therapy. Physical examination Amebic colitis-Fever-some patients-Weight loss -Diffuse abdominal tenderness -Heme-positive stools -Patients with fulminant colitis are more likely to present with abdominal pain, distension, and rebound tenderness.Amebic liver abscess-Fever -Right upper quadrant abdominal tenderness-Durbans sign-intercostal tenderness consistent sign of amoebic dysentery.-Weight loss -Tender Hepatomegaly -Jaundice

-Right pleural effusion-Serous and straw coloured.-Rapture of the liver abcess into the pleural space or peritoneal cavityDDXAmoebic coliti s

1) Arteriovenous Malformations 2) Campylobacter Infections 3) Diverticulitis 4) Escherichia Coli Infections 5) Inflammatory Bowel Disease 6) Salmonellosis 7) Shigellosis 8) Ischemic colitis9) Inflammatory bowel disease

Amoebic liver abcess10) Hepatocellular Adenoma 11) Echinococcal cyst12) Pyogenic Hepatic Abscesses 13) Abdominal Absces

INVESTIGATIONSLABFHG-Lecocytosis with eosinophilia-AmaebomaPresence of PMN cells predominant-Liver abscessAnemia may occur.ESR-elevatedMicroscopy-Finding quadrinucleated cysts or trophozoites containing ingested erythrocytes in stool is considered by many to be diagnostic for amebic colitis.Antigen detection-A stool antigen test specific for E histolytica is available - Monoclonal antibodies specific for the galactose (Gal)/N-acetyl-D-galactosamine (GalNAc) lectin of E histolytica >95 % sensitive and specificSerology-Serum antiamebic antibody tests are an important adjunct to antigen detection, particularly in cases of amebic liver abscess, in which the parasite is found less commonly in the stoolHowever, antibody persists for years after the initial infection; therefore, differentiating between current and previous infection may be difficult, especially in individuals from endemic areas.IMAGINGCXR-Raised right diaphragm and right pleural effussionUltrasound: An amebic liver abscess will appear as a homogenous hypoechoic round lesion.CT scanWith contrast, an amebic liver abscess appears as a rounded, low-attenuation lesion with an enhancing rim. The abscess may be homogenous or septated, with or without observable fluid levels.PROCEDURESLiver aspirationIf an amebic or pyogenic cause of liver abscess cannot be differentiated on clinical grounds and the patient is not stable enough to await serology or antigen detection, liver aspiration under CT scan or ultrasound guidance should be performed.Aspiration of an amebic liver abscess yields an odorless yellow-brown liquid that should be sent for microscopic examination, culture, and antigen detection.Colonoscopy-Colonoscopy is recommended if stool and serologic study results are negative in a patient thought to have amebic colitis.-A relative contraindication to endoscopy is if the patient is thought to have fulminant colitis, in which an increased risk of intestinal perforation exists.-The appearance of amebic colitis may resemble that of inflammatory bowel disease, with a friable and diffusely ulcerated mucosa. -In addition, an ameboma may be present in the form of an annular lesion, which usually occurs in the cecum and ascending colon and often is visually indistinguishable from colonic carcinoma.

Histologic Findings: -Endoscopically obtained biopsy specimens should be taken from the edge of ulcers and evaluated for motile trophozoites. -Pathologic evaluation of colonic lesions may vary from mucosal thickening to flask-shaped ulcerations to necrosis. Periodic acid-Schiff stains E histolytica magenta and may increase detection of the parasite in biopsied material.MANAGEMENTMedicalAsymptomatic colonization with E histolytica is a risk factor for future development of invasive disease; therefore, affected patients should be treated, and a luminal agent (eg, iodoquinol, paromomycin, diloxanide furoate) should suffice. Patients with invasive amebiasis (eg, colitis, liver abscess) should be treated with metronidazole or tinidazole plus a luminal agent to eradicate colonizationAmoebic liver abcess-Metronidazole remains the drug of choice for amebic liver abscess. Metronidazole enters the protozoa by passive diffusion and is converted to reactive cytotoxic nitroradicals by reduced ferredoxin or flavodoxin.. Tinidazole is well tolerated by patients, and it may be administered once daily.Metronidazole, 750 mg 3 times a day orally for 10 days,. The drug also is available for intravenous administration for those patients who are unable to take medication by the oral route. Chloroquine phosphate may be substituted or added in the event of failure of resolution of clinical symptoms with metronidazole or another nitroimidazole within 5 days or intolerance to metronidazole or a nitroimidazole. Chloroquine has the disadvantage of being associated with higher relapse rates than nitroimidazoles. Adverse effects include gastrointestinal upset, headache, dizziness, and blurred vision. Retinopathy does not occur at the dose used for amebic liver abscess.Luminal amebicidal agent to eradicate the intestinal carriage after the amebic liver abscess has been treated with one of the above tissue amebicides. Failure to use luminal agents can lead to relapse of infection in approximately 10% of patients. Luminal agents with proven efficacy include diloxanide furoate, iodoquinol, and paromomycin.Diloxanide furoate is free of major adverse effects. The most common adverse effect is flatulence and occasional gastrointestinal upset. Give 500mg TDS for 10 daysIodoquinol (diiodohydroxyquin) rarely causes abdominal pain, diarrhea, or rash. A structurally related diiodohydroxyquin caused subacute myelopticoneuropathy and is obsolete now.Although paromomycin may occasionally cause nausea, abdominal cramps, or diarrhea, it is the preferred luminal amebicidal

Antibiotics-The oral tetracyclines indirectly affect luminal amebas by inhibiting the bacterial associates of E histolytica in the bowel lumen. Paromomycin and erythromycin are directly amebicidal . Except for paromomycin(Aminocidine), none of the antibiotics are highly effective against intestinal organisms and therefore should not be used by themselves in treatment. Parenteral antibiotics have little antiamebic activity in any site.

Surgical careIndications for surgery in fulminant amebic colitis include perforation and persistence of abdominal distension and tenderness despite antiamebic therapy.Surgical intervention for intrathoracic or intraperitoneal rupture of an amebic liver abscess rarely is indicated, except in cases complicated by secondary bacterial infection.Consider therapeutic aspiration of amebic liver abscess in the following situations: (1) high risk of abscess rupture, as defined by cavity size greater than 5 cm; (2) left lobe liver abscess, which is associated with higher mortality and frequency of peritoneal leak or rupture into the pericardium;(3) failure to observe a clinical medical response to therapy within 5-7 days(4) cannot differentiate from a pyogenic liver abscess.Imaging-guided needle aspiration or catheter drainage is the procedure of choice. Simple needle aspiration is less invasive, less expensive, and has the advantage of being able to drain multiple abscesses in the same session. Simple needle aspiration avoids problems related to catheter care