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Amebiasis, Emergency Medicine

Basics

Description

- Invasive parasitic infection with both intestinal and extraintestinal manifestations - Endemic worldwide, especially areas with poor sanitation - Populations at risk: - Travelers to, citizens of, and immigrants from endemic areas - Institutionalized persons - Practitioners of oral-anal sexual activity - Men who have sex with men (MSM) - HIV infected individuals

- Risk factors for increased severity of disease and complications: - Immunocompromised: Corticosteroid use, HIV infection, malnutrition, malignancy - Pregnancy/postpartum state - Extremes of age

- Toxic megacolon: - Toxic-appearing patient - Profuse diarrhea (>10 stools per day) - Fever - Distended, tympanitic abdomen with signs of peritonitis - Associated with corticosteroid use - High mortality

- Amebic strictures: - Owing to chronic inflammation/scarring - Crampy abdominal pain - Nausea and vomiting (may be feculent) - Partial or complete bowel obstruction

- Chronic amebic colitis: - Mild recurrent episodes of bloody diarrhea, abdominal cramping, and tenesmus - Weight loss - May persist for years

- Extraintestinal disease: - Amebic liver abscess: - Most frequent extraintestinal manifestation (3-9% of cases) - Single abscess in right lobe (50-80%) - May develop months to years postexposure (median of 3 mo) - Fever - Right upper quadrant pain - Hepatomegaly with point tenderness - Rales at right lung base - Concurrent diarrhea unusual (20-33%) - Complication: Rupture into pleural cavity (10-20%), peritoneum, or pericardium (rare) - Increased risk of rupture if >5 cm in diameter or left lobe location

- Cutaneous amebiasis: - Perineum and genitalia - Painful, irregularly shaped ulcers - Purulent exudate

- Abdominal US: - 58-90% sensitive for liver abscess - Sensitivity influenced by size and location - Evaluate abscess for increased risk of rupture (>5 cm or located in left lobe)

  • Invasive parasitic infection with both intestinal and extraintestinal manifestations
  • Endemic worldwide, especially areas with poor sanitation
  • Populations at risk:Travelers to, citizens of, and immigrants from endemic areasInstitutionalized personsPractitioners of oral-anal sexual activityMen who have sex with men (MSM)HIV infected individuals
  • Risk factors for increased severity of disease and complications:Immunocompromised: Corticosteroid use, HIV infection, malnutrition, malignancyPregnancy/postpartum stateExtremes of age

Etiology

  • Entamoeba histolytica, an anaerobic, nonflagellated protozoa
  • Fecal-oral transmission:Humans are sole reservoir.
  • Ingested organisms cause invasive colitis.
  • Extraintestinal spread is hematogenous.

Diagnosis

Signs and Symptoms

  • Intestinal disease:Onset 1 wk to 1 mo postexposureAcute diarrhea (nondysenteric colitis):80% of casesAfebrileOccult blood in stoolBenign abdominal examClassic dysentery:Bloody mucoid diarrheaAbdominal pain/benign abdominal examTenesmusWeight lossFever (rare)Fulminant colitis:Toxic-appearing patientRigid abdomen (25%)FeverSevere bloody diarrheaRapid progression to perforated bowel and frank peritonitis>40% mortalityToxic megacolon:Toxic-appearing patientProfuse diarrhea (>10 stools per day)FeverDistended, tympanitic abdomen with signs of peritonitisAssociated with corticosteroid useHigh mortalityAmeboma:Intraluminal granulated massTender palpable mass on examAmebic strictures:Owing to chronic inflammation/scarringCrampy abdominal painNausea and vomiting (may be feculent)Partial or complete bowel obstructionChronic amebic colitis:Mild recurrent episodes of bloody diarrhea, abdominal cramping, and tenesmusWeight lossMay persist for years
  • Extraintestinal disease:Amebic liver abscess:Most frequent extraintestinal manifestation (3-9% of cases)Single abscess in right lobe (50-80%)May develop months to years postexposure (median of 3 mo)FeverRight upper quadrant painHepatomegaly with point tendernessRales at right lung baseConcurrent diarrhea unusual (20-33%)Complication: Rupture into pleural cavity (10-20%), peritoneum, or pericardium (rare)Increased risk of rupture if >5 cm in diameter or left lobe locationExtrahepatic amebic abscess:BrainLungPerinephricSplenicVaginal/cervical/uterineCutaneous amebiasis:Perineum and genitaliaPainful, irregularly shaped ulcersPurulent exudate

Fulminant colitis is more likely

Fulminant colitis is more likely

History

  • Possible sources of exposure
  • Membership in high-risk group

Physical Exam

  • Identify evidence of peritonitis, sepsis, or shock.
  • Tender abdominal mass mandates workup for liver abscess or ameboma.
  • Digital rectal exam shows gross or occult blood in >70% of patients.

Diagnosis Tests & Interpretation

Lab

  • CBC:Leukocytosis in amebic liver abscess and peritonitis
  • Alkaline phosphatase and ALT:Elevated in amebic liver abscess
  • Serum electrolytes, BUN/creatinine if prolonged diarrhea or evidence of dehydration
  • Stool PCR is diagnostic gold standard:100% sensitive and specific
  • Stool ELISA for E. histolytica-specific antigen:74-95% sensitive, 93-100% specific
  • Serum for anti-E. histolytica antibodies:Essential if suspecting liver abscess. These patients rarely shed parasites in stool90-100% sensitive in amebic liver abscess70-90% sensitive in amebic colitis
  • Stool microscopy is <60% sensitive and no longer the test of choice.
  • Fecal leukocytes and culture:Rule out infection of enteroinvasive bacteria;Negative in amebiasis

Imaging

  • Abdominal US:58-90% sensitive for liver abscessSensitivity influenced by size and locationEvaluate abscess for increased risk of rupture (>5 cm or located in left lobe)
  • Abdominal CT or MRI:Equivalent to US for delineating liver abscessesSuperior to US for detecting abscesses in other organs
  • Head CT or MRI:Suspect amebic brain abscess if patient with known amebiasis has altered mental status or focal neurologic findings.Irregular nonenhancing lesions
  • CXR:Elevated right hemidiaphragm and/or right pleural effusion in liver abscess

Diagnostic Procedures/Surgery

  • Colonoscopy with biopsy provides definitive diagnosis of amebic dysentery, colitis, ameboma, and amebic stricture.
  • Percutaneous fine-needle aspiration of liver abscess to exclude bacterial abscess if nondiagnostic serology or antiamebic therapy failsNot for primary treatment of liver abscesses

Differential Diagnosis

  • Intestinal amebiasis:Enteroinvasive bacterial infection (Staphylococcus, E. coli, Shigella, Salmonella, Yersinia, Campylobacter)Inflammatory bowel diseaseIschemic colitisArteriovenous malformationAbdominal aortic aneurysmPerforated duodenal ulcerIntussusception, diverticulitisPancreatitisColorectal carcinoma
  • Amebic abscess:Bacterial abscessTuberculous cavityEchinococcal cystMalignancyCholecystitis
  • Cutaneous amebiasis:CarcinomaSTDs (condyloma acuminata, chancroid, syphilis)

Treatment

Initial Stabilization/Therapy

  • Airway, breathing, circulation (ABCs)
  • IV 0.9% NS if signs of significant shock

Ed Treatment/Procedures

  • Oral fluids if mild; IV if moderate/severe dehydration
  • Avoid antidiarrheal agents.
  • Correct serum electrolyte imbalances.
  • Stool sample for E. histolytica PCR or ELISA, plus serology for anti-E. histolytica antibodies
  • If stool or serum is positive for E. histolytica:Metronidazole or tinidazole is 1st-line drug for systemic amebiasis (90% cure rate)Chloroquine is an alternative systemic agentAlways follow systemic therapy with a luminal agent to eradicate intestinal colonization (erythromycin, iodoquinol, nitazoxanide, paromomycin, or tetracycline).Do not use the luminal agents alone
  • If stool or serum is negative for E. histolytica:Refer to gastroenterologist for colonoscopy with biopsy.Repeat serology in 7 days.Consider empiric course of metronidazole if high suspicion for amebiasis and patient is critically ill.
  • If evidence of peritonitis or sepsis:Add IV antibiotic directed against anaerobic and gram-negative bacteria.Surgery if toxic megacolon or perforation
  • If liver abscess is suspected:US or CT of hepatobiliary system with concurrent amebic serologyIf imaging demonstrates an abscess but serology is negative, treat with amebicides and repeat serology in 7 days.Consider abscess drainage by surgeon or interventional radiologist in conjunction with amebicidal therapy.If symptoms do not improve after 5-7 days of empiric amebicidal therapy, consider fine-needle aspiration to rule out bacterial abscess or hepatoma.
  • Use metronidazole with caution in 1st-trimester pregnancy, but do not withhold if patient has fulminant colitis or amebic abscess.
  • Use erythromycin or nitazoxanide as intestinal amebicides along with metronidazole.
  • Erythromycin or nitazoxanide may be used alone for mild dysentery in 1st-trimester pregnancy.
  • Chloroquine, iodoquinol, paromomycin, tetracycline, and tinidazole are contraindicated.

Medication

First Line

  • Metronidazole: 500-750 mg (peds: 30-50 mg/kg/24 h) PO/IV q8h for 5-10 d
  • Tinidazole: 2 g/d (peds: 50-60 mg/kg/d) PO for 3-6 d. For children older than 3 yr

Second Line

  • Chloroquine: 1,000 mg/d PO for 2 d then 500 mg/d PO for 14 d; or 200 mg IM for 10-12 d
  • Erythromycin: 250-500 mg (peds: 30-50 mg/kg/24 h) PO q6h for 10-14 d
  • Iodoquinol: 650 mg PO q8h for 20 d
  • Nitazoxanide: 500 mg PO q12. for 3 d (10 d if liver abscess) for children >12 yr
  • Paromomycin: 500 mg (peds: 25-30 mg/kg/24 h) PO q8h for 5-10 d
  • Tetracycline: 250-500 mg (peds[>12 yr]: 25-50 mg/kg/24 h) PO q6h for 10 d
  • Chloroquine and iodoquinol are contraindicated.
  • Tetracycline contraindicated in children <8 yr

Use erythromycin or nitazoxanide only.

Follow-Up

Disposition

Admission Criteria

  • Shock, sepsis, or peritonitis
  • Hypotension or tachycardia unresponsive to IV fluids
  • Children with >10% dehydration
  • Severe electrolyte imbalance
  • Patients unable to maintain adequate oral hydration:Extremes of age, cognitive impairment, significant comorbid illness
  • Fulminant colitis or toxic megacolon
  • Bowel obstruction
  • Extraintestinal abscesses
  • Failure of outpatient regimen

Discharge Criteria

  • Nontoxic presentation of acute or chronic dysentery
  • Able to maintain adequate oral hydration and medication compliance
  • Dehydration responsive to IV fluids

Issues for Referral

Consult surgery if evidence of peritonitis, toxic megacolon, colonic perforation, or liver abscess.

Follow-Up Recommendations

  • Gastroenterology and infectious disease follow-up in 7 days for repeat serology and possible endoscopic evaluation.
  • Physical exam in 14 days to assess for treatment effectiveness and for development of complications or extraintestinal disease.

Pearls and Pitfalls

  • Avoid antidiarrheal medications
  • Always give double therapy with both a systemic amebicidal (metronidazole, tinidazole, or chloroquine) plus an intestinal amebicidal (erythromycin, iodoquinol, nitazoxanide, paromomycin, or tetracycline) unless contraindicated.
  • Always be vigilant for high-mortality complications such as fulminant colitis or extraintestinal disease.

Additional Reading

  • Chavez-Tapia NC, Hernandez-Calleros J, Tellez-Avila FI, et al. Image-guided percutaneous procedure plus metronidazole versus metronidazole alone for uncomplicated amoebic liver abscess. Cochrane Database Syst Rev. 2009;1:CD004886. doi:10.1002/14651858.CD004886.pub2.
  • Escobedo AA, Almirall P, Alfonso M, et al. Treatment of intestinal protozoan infections in children. Arch Dis Child. 2009;94:478-482.
  • Fotedar R, Stark D, Beebe N, et al. Laboratory diagnostic techniques for Entamoeba species. Clin Microbiol Rev. 2007;20:511-532.
  • Gonzalez MLM, Dans LF, Martinez EG. Antiamoebic drugs for treating amoebic colitis. Cochrane Database Syst Rev. 2009;2:CD006085. doi:10.1002/14651858.CD006085.pub2.

See Also (Topic, Algorithm, Electronic Media Element)

Codes

ICD9

  • 006.0 Acute amebic dysentery without mention of abscess
  • 006.1 Chronic intestinal amebiasis without mention of abscess
  • 006.9 Amebiasis, unspecified
  • 006.8 Amebic infection of other sites
  • 006.2 Amebic nondysenteric colitis
  • 006.3 Amebic liver abscess
  • 006.4 Amebic lung abscess
  • 006.5 Amebic brain abscess
  • 006.6 Amebic skin ulceration
  • 006 Amebiasis

ICD10

  • A06.0 Acute amebic dysentery
  • A06.1 Chronic intestinal amebiasis
  • A06.9 Amebiasis, unspecified
  • A06.89 Other amebic infections
  • A06.2 Amebic nondysenteric colitis
  • A06.3 Ameboma of intestine
  • A06.4 Amebic liver abscess
  • A06.5 Amebic lung abscess
  • A06.6 Amebic brain abscess
  • A06.7 Cutaneous amebiasis
  • A06.81 Amebic cystitis
  • A06.82 Other amebic genitourinary infections
  • A06.8 Amebic infection of other sites
  • A06 Amebiasis

SNOMED

  • 111910009 Amebic infection (disorder)
  • 186116005 Acute amebic dysentery (disorder)
  • 23874000 Chronic amebiasis (disorder)
  • 238449000 Amebiasis of skin (disorder)
  • 406559005 Amebic infection of central nervous system
  • 65095005 Amebic lung abscess
  • 75119003 Amebic liver abscess (disorder)