Fetid belching with a sulfur smell

Specialty: Gastrointestinal.

• Sulfur belches
• burps that smell like rotten eggs
• foul belching due to fermentation

Why it occurs

• Bacterial overgrowth in the small intestine (SIBO) due to the proliferation of sulfate-reducing bacteria that produce hydrogen sulfide gas ($H_2S$)
• Gastroparesis or severe gastric retention that allows the prolonged breakdown of proteins rich in sulfur amino acids in the stomach
• Giardia lamblia infection that drastically alters the microbiota of the proximal intestine and generates foul fermentation
• Diet very rich in foods containing sulfur (eggs, red meat, garlic, onion, cruciferous vegetables) combined with hypochlorhydria due to prolonged use of PPIs.

Initial workup

Breath test for SIBO with specific measurement of hydrogen sulfide ($H_2S$, using latest generation breath analyzers) | Serial parasitological examination of stool in three samples or immunoassay by ELISA for Giardia lamblia antigen | Upper digestive endoscopy with duodenal aspirate for quantitative culture of aerobic and anaerobic bacteria | Gastric emptying scan if there is clinical suspicion of gastroparesis.

Standard management

• Antibiotic therapy for SIBO with suspected sulfate-reducing bacteria — rifaximin 550 mg three times a day for 14 days alone or combined with neomycin 500 mg twice a day; or metronidazole 250 mg three times a day
• Specific antiparasitics in case of giardiasis — metronidazole 250 mg three times a day for 5-7 days, or tinidazole 2 g in a single oral dose
• Digestive enzymes with betaine hydrochloride — to acidify the gastric environment in patients with confirmed hypochlorhydria
• Prokinetics (domperidone 10 mg three times a day before meals to accelerate gastric emptying of protein remains).