Treatment of dysentry

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Treatment of Dysentery

Dysentery is broadly divided into two types: bacillary dysentery (caused mainly by Shigella spp.) and amoebic dysentery (caused by Entamoeba histolytica). Management differs significantly between them.

1. General Principles (Both Types)

Rehydration

Fluid replacement is the most important initial step.

Oral rehydration is preferred unless the patient is comatose or in shock.
WHO/UNICEF standard reduced-osmolarity ORS (245 mOsm/L): sodium 75 mmol/L, glucose 75 mmol/L, potassium 20 mmol/L, chloride 65 mmol/L, citrate 10 mmol/L.
IV fluids are reserved for severe dehydration, shock, or inability to tolerate oral intake.

Nutrition

Early refeeding is safe, well-tolerated, and clinically beneficial.
Continue breastfeeding in infants (unless contraindicated, e.g., maternal HIV).

Agents to AVOID

Antimotility agents (loperamide, opioids, anticholinergics) are contraindicated in bloody dysentery - they may worsen symptoms, prolong fever, increase risk of toxic megacolon, and have been implicated in HUS in children with EHEC.
Antispasmodics are also contraindicated.

2. Bacillary Dysentery (Shigellosis)

When to Use Antibiotics

Shigellosis is self-limited in healthy adults (5-7 days without treatment), but antibiotic therapy:
- Shortens symptom duration
- Reduces fecal bacterial shedding
- Decreases spread to contacts
- Reduces complications (especially important in children <5 years)
Antibiotics are recommended for: severe infections, malnourished/very young/elderly patients, immunocompromised patients, outbreak settings, and food handlers.

First-Line Antibiotics

Drug	Adult Dose	Duration	Notes
Ciprofloxacin	500 mg PO twice daily	3-5 days (7-10 days for severe)	First-line fluoroquinolone; 30 mg/kg/day in 2 divided doses for children
Azithromycin	500 mg PO daily (or 1-1.5 g single dose)	3-5 days	Useful for resistant strains; first-line in many areas now due to fluoroquinolone resistance
Ceftriaxone	50-100 mg/kg/day IV/IM	2-5 days	Preferred for severe disease, children, and resistant cases

Second-Line / Alternative Antibiotics

Cefixime 400 mg once daily for 3 days - oral option where ciprofloxacin-resistant strains are present
Pivmecillinam - used in some guidelines for susceptible strains

Resistance Warning (Important)

TMP-SMX and ampicillin are no longer recommended as first-line - widespread resistance in the US and many other regions.
Emerging resistance to ciprofloxacin is being tracked by the CDC globally.
Ceftriaxone resistance has been reported, though still uncommon.
Strains with reduced susceptibility to azithromycin have also been described.
Always guide antibiotic selection by local susceptibility data when available.

- Harrison's Principles of Internal Medicine 22E, p. 1368 - Jawetz, Melnick & Adelberg's Medical Microbiology 28E, p. 250 - Sleisenger and Fordtran's GI and Liver Disease, p. 2194

3. Amoebic Dysentery (Entamoeba histolytica)

Step-wise Treatment

Step 1 - Treat tissue trophozoites (invasive disease):

Metronidazole 750 mg PO/IV three times daily for 7-10 days (adults) - drug of choice
Tinidazole 2 g PO daily for 3-5 days - alternative nitroimidazole; better tolerated, shorter course

Step 2 - Eradicate luminal cysts (essential to prevent relapse and transmission):

Paromomycin 500 mg PO three times daily for 7 days - acts on organisms in the lumen; follow after metronidazole/tinidazole
Diloxanide furoate 500 mg PO three times daily for 10 days - alternative luminal agent

Special situations:

Asymptomatic cyst carriers: treat with paromomycin (luminal agent only; metronidazole not necessary)
Amoebic liver abscess: metronidazole + chloroquine; surgical/percutaneous drainage if large or rupture risk
Dehydroemetine was previously used but is now obsolete

- The Essentials of Forensic Medicine and Toxicology 36th ed., p. (block 6) - Sleisenger and Fordtran's GI and Liver Disease

4. Treatment of Complications

Complication	Management
Toxic megacolon	Correct hypokalemia/dehydration; nasogastric decompression; surgical review; colectomy if no improvement in 48-72 h
Rectal prolapse	Gentle manual reduction with patient in knee-chest position; osmotic reduction with warm MgSO₄ if edema present
HUS	Supportive (dialysis if needed); avoid antibiotics in EHEC-associated HUS
Seizures in children	Correct hypoglycemia, hyponatremia, and fever; neurological support
Intestinal perforation	Emergency surgery + aggressive medical support

5. Special Populations

Children <5 years: highest risk of severe disease and death; ciprofloxacin is an accepted indication despite limited quinolone data in children; ceftriaxone preferred for IV treatment; dose-adjust carefully
Malnourished children: zinc supplementation may reduce severity; early refeeding is important
Pregnant women: avoid fluoroquinolones and metronidazole in first trimester if possible; azithromycin or ceftriaxone preferred
HIV-infected patients: higher risk of bacteremia and severe complications; treat aggressively

Recent Evidence Note

A 2024 systematic review (PMID: 39472797) found high rates of Shigella antimicrobial resistance across Africa, and a 2025 meta-analysis (PMID: 39827134) documented ESBL and carbapenemase-producing Shigella strains - highlighting that empiric antibiotic choices must increasingly account for local resistance profiles, particularly in resource-limited settings.

Key Takeaway: Rehydration is the cornerstone for all dysentery. For bacillary dysentery, ciprofloxacin or azithromycin are current first-line choices, but always check local resistance patterns. For amoebic dysentery, treat invasive disease with metronidazole/tinidazole, then always follow with a luminal agent (paromomycin) to clear cysts and prevent relapse.

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