Small intestinal fungal overgrowth

Small intestinal fungal overgrowth (SIFO) is a form of dysbiosis caused by the excessive growth of fungi (primarily Candida species) in the small intestine. Risk factors include immunosuppression caused by conditions like HIV or cancer, the use of medications (e.g., corticosteroids or proton pump inhibitors), and impaired gut motility. Clinical features are similar to those of small intestinal bacterial overgrowth (SIBO), including abdominal pain, bloating, gas, and diarrhea. The diagnosis of SIFO is challenging. Invasive fungal culture of a small intestinal aspirate can confirm the diagnosis, especially in patients with typical symptoms that do not improve after antibiotic treatment. Management is tailored to the individual patient and primarily involves antifungal agents, e.g., fluconazole or nystatin. Dietary approaches, probiotics, and lifestyle modifications can also be part of the treatment plan. Potential complications of SIFO include malabsorption and malnutrition.

Small intestinal fungal overgrowth (SIFO) is a type of dysbiosis characterized by an excessive growth of fungi in the small intestine. ^[1][2]

• Prevalence
  • Exact incidence and prevalence are unknown. ^[2]
  • Occurs in up to 34% of patients with small intestinal bacterial overgrowth (SIBO) ^[2]
  • Found in ∼ 25% of patients with unexplained chronic gastrointestinal symptoms ^[1]
• Populations at increased risk ^[2]
  • Children
  • Older adults
  • Hospitalized patients

Epidemiological data refers to the US, unless otherwise specified.

• Pathogens ^[2]
  • Most common: Candida albicans
  • Others: C. glabrata, C. tropicalis, C. krusei, C. famata, C. parapsilosis
• Risk factors ^[1][2]
  • Prolonged use of antibiotics
  • Immunosuppression (e.g., HIV, cancer treatment)
  • Insufficiently managed diabetes
  • Use of proton pump inhibitors
  • Impaired small intestine motility

Symptoms are similar to those of SIBO.

• Common symptoms ^[2]
  • Bloating
  • Abdominal pain
  • Diarrhea (may be watery diarrhea)
  • Flatulence
• Other symptoms ^[2]
  • Mucus in stool
  • Fecal urgency
  • Belching
  • Chest pain

• Consider SIFO in patients with symptoms suggestive of SIBO who do not respond to antibiotic therapy. ^[2]
• Testing standards have not been established.
• Fungal culture of small intestinal aspirate (gold standard): A fungal count of >10³colony-forming units (CFUs)/mL is typically used to confirm SIFO. ^[1][2]

Breath testing is not indicated for SIFO because fungi do not produce hydrogen or methane and can therefore not be detected. ^[1]

• Small intestinal bacterial overgrowth (SIBO)
• See also:
  • "Differential diagnoses of abdominal pain"
  • “Differential diagnosis of diarrhea”

The differential diagnoses listed here are not exhaustive.

General principles ^[2]

• There is very limited data to guide treatment decisions.
• Treatment may need to be adapted based on comorbidities, severity, and treatment tolerance.
• Consider general lifestyle changes to support gut health, e.g, regular physical exercise, dietary modifications

Antifungal therapy ^[1][2]

• Optimal dosage and duration of antifungal treatment have not yet been established.
• Agents
  • Fluconazole
  • Nystatin
  • Amphotericin B

• Malabsorption of nutrients (potentially leading to malnutrition and unintentional weight loss)
• Irritable bowel syndrome (IBS)
• Possible link to colorectal cancer ^[2]

We list the most important complications. The selection is not exhaustive.