Differential Diagnosis for Green Mushy Stool

• Single most likely diagnosis
  • Giardiasis: This is a common cause of green, mushy stools, especially if the patient has not consumed green leafy vegetables. Giardia lamblia infection can lead to malabsorption and altered stool color.
• Other Likely diagnoses
  • Bile salt malabsorption: Conditions like bile duct obstruction or liver disease can lead to an excess of bile salts in the stool, causing a greenish color.
  • Small intestine bacterial overgrowth (SIBO): An overgrowth of bacteria in the small intestine can lead to malabsorption and production of green, mushy stools.
  • Viral gastroenteritis: Certain viral infections can cause changes in stool color and consistency, including a green, mushy appearance.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Intussusception: Although rare in adults, intussusception can cause green, bloody stools and is a medical emergency.
  • Gastrointestinal malignancy: Certain types of cancer, such as gastric or small intestine cancer, can cause changes in stool color and consistency.
  • Inflammatory bowel disease (IBD): Conditions like Crohn's disease or ulcerative colitis can cause green, bloody stools and require prompt medical attention.
• Rare diagnoses
  • Pseudomembranous colitis: A rare condition caused by Clostridioides difficile infection, which can lead to green, watery stools.
  • Congenital disorders of bile acid synthesis: Rare genetic disorders that affect bile acid production, leading to green, mushy stools.
  • Whipple's disease: A rare, systemic bacterial infection that can cause malabsorption and changes in stool color and consistency.