parasitic infections

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  • 1. Parasitic Infections

2. Amoebiasis

  • Introduction
  • Pathogenesis
  • Clinical Features
  • Investigations
  • Imaging techniques
  • Treatment

3. Amoebiasis

  • Introduction
  • Pathogenesis
  • Clinical Features
  • Investigations
  • Imaging techniques
  • Treatment

4. Introduction

  • Caused byEntamoeba 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

5. Amoebiasis

  • Introduction
  • Pathogenesis
  • Clinical Features
  • Investigations
  • Imaging techniques
  • Treatment

6. Pathogenesis

  • Organismgut (through food/water contaminated with the cyst) cysts hatch trophozoites carried to colon FLASK SHAPED ULCERS(in the submucosa)
  • Trophozoites multiplycysts
  • Portal circulationPassed in faeces
  • Infects others

7. Pathogenesis

  • Portal 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

8. 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 surfacepulmonary complications
  • Abscess cavitychocolate coloured, odourless, anchovy sauce like fluid (mixture of necrotic liver tissue and blood)
  • Secondary infection in the cavity may occurpus
  • Untreated abscesslikely to rupture

9. Pathogenesis

  • Chronic infection in the large bowel
  • granulomatous lesion along the large bowel; most commonly seen in the caecum
  • Amoeboma

10. Amoebiasis

  • Introduction
  • Pathogenesis
  • Clinical Features
  • Investigations
  • Imaging techniques
  • Treatment

11. 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

12. 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

13. 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

14. Amoebiasis

  • Introduction
  • Pathogenesis
  • Clinical Features
  • Investigations
  • Imaging techniques
  • Treatment

15. 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

16. 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

17. Amoebiasis

  • Introduction
  • Pathogenesis
  • Clinical Features
  • Investigations
  • Imaging techniques
  • Treatment

18. 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)

19. Amoebiasis

  • Introduction
  • Pathogenesis
  • Clinical Features
  • Investigations
  • Imaging techniques
  • Treatment

20. 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

21. 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

22. 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 hage, 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

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