What are the differentiating aspects of infectious diarrhea and irritable bowel syndrome (IBS) diarrhea?

From the Guidelines

Infectious diarrhea and irritable bowel syndrome (IBS) diarrhea are distinct conditions with different causes, presentations, and treatment approaches, and it is crucial to differentiate between them to provide appropriate management and improve patient outcomes. Infectious diarrhea is caused by pathogens like bacteria (E. coli, Salmonella), viruses (norovirus, rotavirus), or parasites (Giardia, Cryptosporidium) and typically has an acute onset with symptoms lasting days to weeks, as described in the 2017 Infectious Diseases Society of America clinical practice guidelines for the diagnosis and management of infectious diarrhea 1. It often presents with fever, bloody stool, severe abdominal pain, and sometimes vomiting. Stool tests may reveal white blood cells, blood, or specific pathogens. Treatment includes rehydration with oral rehydration solutions (containing sodium, potassium, glucose, and water), antibiotics for bacterial causes (such as ciprofloxacin 500mg twice daily for 3-5 days for traveler's diarrhea), and specific antiparasitic medications when indicated.

In contrast, IBS diarrhea is a chronic functional disorder without identifiable pathogens, typically lasting months to years with symptom fluctuations. It features abdominal pain relieved by defecation, bloating, mucus in stool, and diarrhea often triggered by stress, certain foods, or hormonal changes. Diagnosis requires ruling out other conditions, as tests are typically normal. Treatment focuses on symptom management with antispasmodics like dicyclomine (10-20mg three times daily), antidiarrheals like loperamide (2mg as needed), dietary modifications (low-FODMAP diet), and stress reduction techniques, as recommended in the 2022 American Gastroenterological Association (AGA) Clinical Practice Update on the role of diet in irritable bowel syndrome 1. The key distinction is that infectious diarrhea represents an active infection requiring pathogen elimination, while IBS diarrhea reflects gut-brain dysregulation requiring long-term symptom management.

Some key points to consider in differentiating between infectious diarrhea and IBS diarrhea include:

• The duration of symptoms: infectious diarrhea typically lasts days to weeks, while IBS diarrhea can last months to years
• The presence of fever, bloody stool, and severe abdominal pain: these symptoms are more commonly associated with infectious diarrhea
• The presence of white blood cells, blood, or specific pathogens in stool tests: these findings are more commonly associated with infectious diarrhea
• The response to treatment: infectious diarrhea typically responds to antimicrobial therapy, while IBS diarrhea requires long-term symptom management with dietary modifications, antispasmodics, and stress reduction techniques.

Overall, accurate diagnosis and treatment of infectious diarrhea and IBS diarrhea are crucial to improve patient outcomes and reduce morbidity and mortality, and clinicians should be aware of the distinct causes, presentations, and treatment approaches for these conditions, as described in the 2017 IDSA guidelines 1 and the 2022 AGA Clinical Practice Update 1.

From the Research

Infectious Diarrhea

• Infectious diarrhea is the most common cause of diarrhea worldwide, responsible for more deaths than other gastrointestinal tract diseases 2
• The majority of cases can be divided into three principal clinical presentations: acute watery diarrhea, bloody diarrhea (dysentery), and persistent diarrhea with or without intestinal malabsorption 2
• Specific diagnosis and identification of the causative agent remain crucial from public health and epidemiological perspectives, and can be reserved for patients with severe dehydration, more severe illness, persistent fever, bloody stools, immunosuppression, and for cases of suspected nosocomial infection or outbreak 2

Irritable Bowel Diarrhea

• There is no direct evidence provided in the studies to discuss irritable bowel diarrhea, however, it can be noted that the provided studies focus on infectious diarrhea and its management

Management of Infectious Diarrhea

• The main therapeutic measure for infectious diarrhea is sufficient oral rehydration 3, 4
• Oral rehydration therapy is inexpensive, effective, and adaptable, and has become a powerful intervention for improvement in health care for all ages 4
• Antibiotics are effective against shigellosis, campylobacteriosis, C. difficile colitis, traveler's diarrhea, and protozoal infections, but routine antibiotic use is not recommended for most adults with mild, watery diarrhea 2, 3
• Empirical antibiotic treatment should be considered in patients with fever and/or bloody diarrhea and in patients at risk 3

Treatment Options

• Azithromycin or ciprofloxacin are recommended for the treatment of traveler's diarrhea, taking into account local antimicrobial resistance in the country of travel and possible side effects 3
• Oral rehydration solutions, such as the standard World Health Organization ORS, have been shown to decrease mortality associated with acute diarrheal illnesses in children and adults 5
• Modifications to the standard ORS, such as hypo-osmolar or hyperosmolar solutions, use of rice-based ORS, zinc supplementation, and the use of amino acids, have been derived and are under investigation 5