Download - Parasitic Infections
Parasitic Infections
Amoebiasis
• Introduction• Pathogenesis• Clinical Features• Investigations• Imaging techniques• Treatment
Amoebiasis
• Introduction• Pathogenesis• Clinical Features• Investigations• Imaging techniques• Treatment
Introduction
• Caused by Entamoeba histolytica• Common in the Indian subcontinent, Africa, parts
of South America (> 50% population affected)• Mode of infection: faeco – oral• Substandard hygiene and sanitation • Amoebic liver abscess (MC extra intestinal
manifestation): 10% of infected population• Immunocompromised and alcoholic: susceptible
Amoebiasis
• Introduction• Pathogenesis• Clinical Features• Investigations• Imaging techniques• Treatment
Pathogenesis
• Organism gut (through food/water contaminated with the cyst)cysts hatch trophozoites carried to colon FLASK SHAPED ULCERS (in the submucosa)
• Trophozoites multiply cysts
Portal circulation Passed in faeces
Infects others
PathogenesisPortal circulation
Trophozoites are filtered and trapped in the interlobular veins of the liver
Multiply in the portal triads; local infarction & liquefactive necrosis (proteolytic enzymes)
Areas ofnecrosis – coalesce to form Amoebic Liver Abscess Cavity
Pathogenesis –Amoebic Liver Abscess• Right lobe> Left lobe (80% > 10%); remaining 10% are
multiple• Right lobe: blood from the superior mesenteric artery
runs n a straighter course through the portal vein into the larger lobe
• More common in the diaphragmatic surface pulmonary complications
• Abscess cavity chocolate coloured, odourless, ‘anchovy – sauce’ like fluid (mixture of necrotic liver tissue and blood)
• Secondary infection in the cavity may occur pus• Untreated abscess likely to rupture
Pathogenesis…
Chronic infection in the large bowel
granulomatous lesion along the large bowel; most commonly seen in the caecum
Amoeboma
Amoebiasis
• Introduction• Pathogenesis• Clinical Features• Investigations• Imaging techniques• Treatment
Clinical Features: Symptoms
• Young adult male• h/o pain, fever, insidious onset of non specific
symptoms (anorexia, night sweats, cough, weight loss) gradually progresses to more specific symptoms: pain in the rt upper abdomen, shoulder tp pain, hiccoughs, non productive cough
• Past h/o bloody diarrhoea and travel to an endemic area
Clinical Features: signs
• Toxic, Anemic patient• Upper abdomen rigidity• Tender hepatomealy• Tender and bulging intercostal spaces, overlying
skin edema, pleural effusion and basal pneumonitis
• Occasionally – trace of jaundice, ascites• Rarely – emergency due to rupture into the
peritoneal, pleural or pericardial activiy
Amoeboma
• Chronic granuloma • Arising in the large bowel, most commonly seen
in the caecum• Prone to occur in longstanding amoebic infection
that has been treated intermittently with drugs without completion of a full course
• Suspected when a patient from an endemic area with generalized ill health, pyrexia, mass in the rt iliac fossa with a h/o blood stained mucoid diarrhoea
Amoebiasis
• Introduction• Pathogenesis• Clinical Features• Investigations• Imaging techniques• Treatment
Investigations
• Haematological & Biochemical investigations: anemia, leucocytosis, raised ESR, raised CRP, hypoalbuminemia, deranged LFT (particularly raised ALP)
• Serological tests: more specific; tests for complement fixation, indirect haemagglutination, indirect immunofluorescence and ELISA.
• Especially useful in non endemic areas
Investigations
• Rigid sigmoidoscopy– Most ulcers occur in the rectosigmoid & therefore
within reach of the sigmoidoscope– Shallow, flask shaped or collar stud, undermined
ulcers– Biopsy/ scrapings can be taken for microscopic
examination
Amoebiasis
• Introduction• Pathogenesis• Clinical Features• Investigations• Imaging techniques• Treatment
Imaging Techniques
• Ultrasound: abscess cavity in the liver is seen as a hypo/ anechoic leson with ill defined borders; accurate; used for aspiration (diagnostic and therapeutic)
• CT may be helpful if doubt in diagnosis• Barium enema• Colonoscopy & biopsy (to differentiate from
carcinoma)
Amoebiasis
• Introduction• Pathogenesis• Clinical Features• Investigations• Imaging techniques• Treatment
Treatment
• Medical– Effective– First choice – Surgery reserved for complications– Metronidazole and tinidazole: effective drugs– After treatment with metro/tinidazole; diloxanide
furoate which is not effective against hepatic infestation, is used for 10 days to destroy any intestinal infestation
Management…
• Aspiration– When imminent rupture of an abscess is expected– Helps in the penetration of metronidazole; hence
reduces the morbidity– Theshold for aspirating an abscess in the left lobe
is lower because of its predilection for rupturing into the pericardium
Management…• Surgical– Reserved for complications of rupture into the pleural
(usually the rt side), peritoneal or pericardial cavities– Resuscitation, drainage and appropriate lavage with
vigorous medical treatment – key principles– Large bowel – severe h’age, toxic megacolon are rare
complications• General principles of a surgical emergency apply• Resuscitation followed by resection of the bowel with
exteriorisation• Vigorous supportive therapy• ICU care