History

Fact Explanation
Cramping abdominal pain. Amoebae invade and penetrate the intact colonic mucosa and enter the submucosa, causing lysis and necrosis of its cells [1]. This would result in colitis which would cause pain.
Blood and mucus diarrhoea. The mucosal invasion results in ulceraration, which is associated with an outflow of tissue fluids, erythrocytes, neutrophils, lymphocytes, epithelial cells, etc, which gives rise to the blood and mucus nature of the diarrhoea [2].
Fever, anorexia, etc. it occurs as part of a systemic inflammatory response due to the lysis of tissue cells by E. histolytica [2].
weight loss. This occurs as a result of the gradual onset of the disease [3].
Gradual onset of disease. This helps to differentiate it from bacillary dysentery, which is of sudden onset [4].
Rectal bleeding without diarrhoea. It can occur in some children when an amebic ulcer erodes a blood vessel [5].
History of very high fever, severe abdominal bloating and pain, worse on movement. These are features of peritonitis which occur in the case of fulminant colitis. Peritonitis develops either because of frank perforation or a slow leak through an extensively diseased bowel [6].
Symptoms lasting more than 2 weeks. Amebiasis is known to cause a chronic colitis [7].
References
  1. HARRIES J. Amoebiasis: a review. J R Soc Med [online] 1982 Mar, 75(3):190-197 [viewed 03 September 2014] Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1437583
  2. BRUCKNER, David A. "Amebiasis." Clinical microbiology reviews [online] 1992, 5(4): 356-369 [viewed 03 September 2014] Available from: 10.1128/CMR.5.4.356
  3. PETRI W. A., SINGH U.. Diagnosis and Management of Amebiasis. Clinical Infectious Diseases [online] 1999 November, 29(5):1117-1125 [viewed 03 September 2014] Available from: doi:10.1086/313493
  4. BOYD JS. The Dysenteries Br Med J [online] 1951 Jun 23, 1(4720):1440-1443 [viewed 06 September 2014] Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2069479
  5. TURNER JA, LEWIS WP, HAYES M, ZIMENT I. Amebiasis--A Symposium Calif Med [online] 1971 Mar, 114(3):44-55 [viewed 06 September 2014] Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1501919
  6. GUPTA SHILPI SINGH, SINGH ONKAR, SHUKLA SUMIT, RAJ MATHUR K. Acute fulminant necrotizing amoebic colitis: a rare and fatal complication of amoebiasis: a case report. Cases J [online] 2009 September [viewed 06 September 2014] Available from: doi:10.4076/1757-1626-2-6557
  7. COOK G C. Persisting diarrhoea and malabsorption.. Gut [online] 1994 May, 35(5):582-586 [viewed 06 September 2014] Available from: doi:10.1136/gut.35.5.582

Examination

Fact Explanation
Lower abdominal tenderness. Amoebae invade and penetrate the intact colonic mucosa and enter the submucosa, causing lysis and necrosis of its cells [1]. This would resulting colitis could cause peritoneal irritation.
Febrile patient. It occurs as part of a systemic inflammatory response due to the lysis of tissue cells by E. histolytica [2].
Anthropometric examination revealing weight loss. This occurs as a result of the gradual onset of the disease [3].
Abdominal distention. It occurs in fulminant amebic colitis and frequently represents leakage through a grossly intact colon rather than a discrete perforation [4].
Rebound tenderness. This is a warning sign of peritonitis and indicates that perforation of the colon may have occurred [4].
References
  1. HARRIES J. Amoebiasis: a review. J R Soc Med [online] 1982 Mar, 75(3):190-197 [viewed 03 September 2014] Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1437583
  2. BRUCKNER, David A. "Amebiasis." Clinical microbiology reviews [online] 1992, 5(4): 356-369 [viewed 03 September 2014] Available from: 10.1128/CMR.5.4.356
  3. PETRI W. A., SINGH U.. Diagnosis and Management of Amebiasis. Clinical Infectious Diseases [online] 1999 November, 29(5):1117-1125 [viewed 03 September 2014] Available from: doi:10.1086/313493
  4. TURNER JA, LEWIS WP, HAYES M, ZIMENT I. Amebiasis--A Symposium Calif Med [online] 1971 Mar, 114(3):44-55 [viewed 06 September 2014] Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1501919

Differential Diagnoses

Fact Explanation
Crohn's disease. it also presents with diarrhoea and weight loss but the abdominal pain is usually postprandial and finger clubbing may be present [1].
Irritable bowel syndrome. It also presents with diarrhoea and abdominal pain but the diarrhoea is not bloody [1].
Campylobacter infections. It also presents with diarrhoea and abdominal cramps associated with fever, but the diarrhoea initially is profuse and watery [2].
Ischemic colitis. It also presents with abdominal pain and blood mixed with stool, but fever is unusual [3].
Diverticulitis. It also presents with abdominal pain, but the pain usually begins in the hypogastrium and then localizes to the left lower quadrant. Also diarrhoea, often bloody, alternates with constipation [4].
Shigellosis. It also presents with fever, abdominal cramps and bloody diarrhoea, but the bloody diarrhoea is usually preceeded by profuse watery diarrhoea [5].
Salmonellosis. It also presents with fever, abdominal pain and occasional diarrhoea, but constipation is a frequent symptom [6].
References
  1. HENDRICKSON B. A., GOKHALE R., CHO J. H.. Clinical Aspects and Pathophysiology of Inflammatory Bowel Disease. Clinical Microbiology Reviews [online] 2002 January, 15(1):79-94 [viewed 03 September 2014] Available from: doi:10.1128/CMR.15.1.79-94.2002
  2. BLASER MARTIN J.. Epidemiologic and Clinical Features of Infections . J INFECT DIS [online] 1997 December, 176(s2):S103-S105 [viewed 03 September 2014] Available from: doi:10.1086/513780
  3. THEODOROPOULOU ANGELIKI. Ischemic colitis: Clinical practice in diagnosis and treatment. WJG [online] 2008 December [viewed 05 September 2014] Available from: doi:10.3748/wjg.14.7302
  4. FERZOCO L.B., RAPTOPOULOS V., SILEN W.. Acute Diverticulitis. N Engl J Med [online] 1998 May, 338(21):1521-1526 [viewed 05 September 2014] Available from: doi:10.1056/NEJM199805213382107
  5. VINH HA, NHU NGUYEN, NGA TRAN, DUY PHAM, CAMPBELL JAMES I, HOANG NGUYEN, BONI MACIEJ F, MY PHAN, PARRY CHRISTOPHER, NGA TRAN, VAN MINH PHAM, THUY CAO, DIEP TO, PHUONG LE, CHINH MAI, LOAN HA, THAM NGUYEN, LANH MAI, MONG BUI, ANH VO, BAY PHAN, CHAU NGUYEN, FARRAR JEREMY, BAKER STEPHEN. A changing picture of shigellosis in southern Vietnam: shifting species dominance, antimicrobial susceptibility and clinical presentation. Array [online] 2009 December [viewed 05 September 2014] Available from: doi:10.1186/1471-2334-9-204
  6. COBURN BRYAN, GRASSL GUNTRAM A, FINLAY B B. Salmonella, the host and disease: a brief review. Immunol Cell Biol [online] December, 85(2):112-118 [viewed 06 September 2014] Available from: doi:10.1038/sj.icb.7100007

Investigations - for Diagnosis

Fact Explanation
Leukocytosis in full blood count and an elevated erythrocyte sedimentation rate. A systemic inflammatory response occurs due to the lysis of tissue cells by E. histolytica [1].
Microscopic examination of fresh stool smears revealing trophozoites that contain ingested red blood cells. The motile form of E. histolytica, the trophozoite, lives in the lumen of the large intestine and has the ability to invade the colonic mucosa [2]. The trophozoites can differentiate in to cysts (the infective form), which will be then excreted in stool.
Enzyme-linked immunosorbent assay (ELISA) to detect antigens from E. histolytica in stool. Galactose-inhibitable lectin of E. histolytica is a highly conserved antigen. Detection of amoebic lectin antigen in faeces using epitope-specific monoclonal antibodies provides a quantitative method for differentiating E. histolytica from E. dispar. The sensitivity and specificity of this assay is also high [3].
Serum antilectin immunoglobulin G (IgG) antibodies detected using ELISA. They are present within 1 week after onset of symptoms in over 95% of patients [3]. But they may be persistent for years so differentiation between past and present infection is difficult.
Colonoscopy to diagnose amebic colitis. It is used when antigen tests are negative. It can be used to detect motile trophozoites using material aspirated or scraped from the base of ulcers. Also, biopsy specimens obtained could be stained with Periodic acid–Schiff, which stains the parasites a magenta color, increasing the ease of detection [4].
Stool examination revealing occult blood. The mucosal invasion results in ulceraration, which is associated with an outflow of tissue fluids and erythrocytes [1].
References
  1. BRUCKNER, David A. "Amebiasis." Clinical microbiology reviews [online] 1992, 5(4): 356-369 [viewed 03 September 2014] Available from: 10.1128/CMR.5.4.356
  2. ESPINOSA-CANTELLANO M., MARTINEZ-PALOMO A.. Pathogenesis of Intestinal Amebiasis: From Molecules to Disease. Clinical Microbiology Reviews [online] 2000 April, 13(2):318-331 [viewed 03 September 2014] Available from: doi:10.1128/CMR.13.2.318-331.2000
  3. ABD-ALLA MOHAMED D., RAVDIN JONATHAN I.. Diagnosis of amoebic colitis by antigen capture ELISA in patients presenting with acute diarrhoea in Cairo, Egypt. Trop Med Int Health [online] 2002 April, 7(4):365-370 [viewed 03 September 2014] Available from: doi:10.1046/j.1365-3156.2002.00862.x
  4. PETRI W. A., SINGH U.. Diagnosis and Management of Amebiasis. Clinical Infectious Diseases [online] 1999 November, 29(5):1117-1125 [viewed 03 September 2014] Available from: doi:10.1086/313493

Investigations - Screening/Staging

Fact Explanation
Reduced hemoglobin levels in full blood count. The mucosal invasion results in ulceraration, which is associated with a outflow of tissue fluids and erythrocytes [1]. This blood loss would result in anemia.
References
  1. BRUCKNER, David A. "Amebiasis." Clinical microbiology reviews [online] 1992, 5(4): 356-369 [viewed 03 September 2014] Available from: 10.1128/CMR.5.4.356

Management - General Measures

Fact Explanation
Adoption of preventive measures: -Boiling of water before drinking. -Washing of raw vegetables and soaking them in vinegar before consumption. Prevention of amebiasis requires interruption of the fecal-oral spread of the infectious cyst stage of the parasite [1].
References
  1. PETRI W. A., SINGH U.. Diagnosis and Management of Amebiasis. Clinical Infectious Diseases [online] 1999 November, 29(5):1117-1125 [viewed 03 September 2014] Available from: doi:10.1086/313493

Management - Specific Treatments

Fact Explanation
Metronidazole. 750 mg, 3 times a day, for 5-10 days given orally. it is a tissue amebicide that is readily absorbed in to the blood stream. Therefore it is useful for intestinal invasive disease [1]. Therapy with metronidazole is usually followed by a luminal agent.
Paromomycin. 10-day course at 30 mg/kg per day. It is given usually to treat asymptomatic infection. It is a luminal amebicide [1].
Surgical interventions. Surgery is needed in instances where complications such as colonic perforation occur in cases of fulminant colitis [2].
References
  1. PRITT BOBBI S., CLARK C. GRAHAM. Amebiasis. Mayo Clinic Proceedings [online] 2008 October, 83(10):1154-1160 [viewed 03 September 2014] Available from: doi:10.4065/83.10.1154
  2. STEIN D., BANK S.. Surgery in amoebic colitis. Gut [online] 1970 November, 11(11):941-946 [viewed 05 September 2014] Available from: doi:10.1136/gut.11.11.941