Gastroenteritis

Question 1

28yo male returning back BKK with watery diarrhoea x3 days, 8 stools/day, mild cramps. No blood or fever. Ate street food, others in tour group is also ill. Diagnosis and treatment

Answer 1

Traveler’s Watery Diarrhoea, caused by ETEC (toxin related), antibiotics not necessary unless mod or severe. If needed, Azithromycin 500MG daily over 3 days with ORS. Given Loperamide if no blood

Question 2

19yo female with bloody stools, fever, abdominal cramps for 1 day. Attended BBQ 2 days prior. Diagnosis and treatment

Answer 2

Bloody Diarrhoea post BBQ. Causes: Campylobacter. Treatment: Azithromycin 500mg x 3 days. DO NOT give loperamide as there is risk of toxic megacolon risk. Monitor for HUS if EHEC suspected

Question 3

4yo presents with bloody diarrhoea but no fever after eating undercooked beef. Parents want Abx. She is mildly dehydrated, hemodynamically stable

Answer 3

Suspected EHEC/STEC (Shiga toxin producing EColi). Abx contraindicated due to risk of HUS. Supportive care only: Hydration, monitoring. NO loperamide – Toxic megacolon

Question 4

60yo man develop profuse watery diarrhoea on day 6 Augmentin for dental infection. He is febrile with lower abdominal pain

Answer 4

CDifficle from Antibiotic use. Need to confirm with stool toxin assay or PCR. Oral vancomycin or fidaxomicin. DO NOT give loperamide as risk of toxic megacolon

Question 5

35yo migrant from India presents with RUQ pain, fever and hepatomegaly. US shows abscess in right liver lobe. Stool microscopy is negative for cysts

Answer 5

Likely Entamoeba Histolytica. Start Metronidazole or tinidazole. Follow with Diloxanide furoate or Paromomycin (Luminal Amoebicide). Combo therapy to prevent recurrence and transmission

Question 6

Parasite: Giardiasis
What is First Line drug and Rationale

What about special Populations like in paeds and pregnancy

Answer 6

First-line Drugs: Tinidazole 2g once

Paediatric/pregnancy: Nitazoxanide (500mg BD x 3 days)

Question 7

Parasite: Amoebiasis
What is First Line Amoebicide and Rationale

Answer 7

Combination Therapy:
Metronidazole (750mg TDS x 10days) + Paromomycin (500mg TDS x 7days)

1) Trophozoites – Active, invasive form (found in tissues), Invade colon or liver (Amoebic colitis, liver abscess)

• Treatment: Metronidazole

2) Cysts – Infective, resistant form (found in stool)
- Persist in intestines and lead to recurrence or transmission
- Treatment: Paromomycin
Luminal Amoebicide to clear cysts from bowel. These drugs are poorly absorbed hence remain in bowel lumen to eradicate cysts

Question 8

Parasite: Amoebiasis

Why Combination Therapy

Answer 8

• Essential for cure and prevent relapse and transmission
• Metronidazole tackle tissue phase but poor luminal phase activity
• Paromomycin tackle luminal phase activity but no systemic absorption
• Without luminal agent – 10-50% relapse rate from persistent cysts

Question 8

Parasite: Cryptosporidium

First-line drug

Answer 8

Nitazoxanide
(500mg x 3days)
- Class: Broad spectrum antiparasitic

Question 9

When do you give Abx for bacterial diarrhea

Answer 9

• Abx only for mod to severe bacterial, bloody diarrhoea (Except EHEC/STEC) or parasitic infections or in high risk patients
• NO loperamide for bloody diarrhoea or C.Difficle infection – Risk of toxic megacolon/HUS

Question 10

Acute GE VS Chronic GE

Answer 10

Acute
- < 2 weeks
- Inflammatory or Non-inflammatory

Chronic
- > 4 weeks
- Broader differentials to consider

Question 11

Common Bacterial Causes

Answer 11

1. E.Coli (ETEC – Enterotoxigenic E.Coli)
   - Source: Contaminated water
   - Traveler’s Diarrhoea, watery stool
2. Campylobacter
   - Source: Undercooked Poultry
   - BLOODY Diarrhoea, FEVER, Cramps
3. Salmonella (Non-Typhoidal)
   - Source: Eggs (Common), Poultry
   - Watery/BLOODY Diarrhoea, FEVER, Cramps, and Nausea
4. Shigella
   - Source: Person-to-Person
   - Dysentery (Blood/ Pus in Stool)
5. C. Difficile
   - Source: Antibiotic Use
   - Hospital-acquired, Foul-smelling diarrhoea
6. Vibrio Cholerae
   - Source: Contaminated Water (Endemic Area)
   - Rice-water Stools, Severe dehydration
7. Shiga-toxin E.coli (STEC), Enterohemorrhagic E.coli (EHEC)
   - Source: Children, undercooked meat
   - BLOODY diarrhoea, NO fever, HUS risk
   - NO abx – Can cause more Shiga toxins which affects endothelial cells in kidneys (Let immune sys do)

Question 12

Common Parasitic Causes

Answer 12

1. Giardia Lamblia
   - Foul-smelling greasy diarrhoea, bloating, no blood
2. Entamoeba Histolytica
   - Dysentery (Bloody Diarrhoea), Liver abscess (Right lobe)
3. Cryptosporidium
   - Chronic watery diarrhoea, immunocompromised hosts (HIV/AIDS)

Question 13

Goals of Pharmacotherapy for GE

Answer 13

1. Rehydration (Supportive)
   - Oral Rehydration Solution
   - IV fluids
2. Symptom Relief
   Anti-Diarrhea: Opioid Agonist Drygs (Loperamide or Diphenoxylate+Atripone), Colloidal Bismuth Compounds or Intestinal adsorbents (Kaolin-Pectin) or Bile Salt-binding Resins and Somastatin-like peptides

Note: Not to give for bacterial or inflammatory to due to risk of toxic megacolon or HUS

Anti-Emetics: 5-HT3 Antagnoists like Ondansetron, Granisetron or Dopamine antagonists like Metoclopramide

3. Bacterial/Parasitic
   Bacterial: Empiral (Ciprofloxacin or Azithromycin) or Vancomycin for CDiff
   (Not to give for STEC or HETC due to HUS risk)