What could cause a long stringy thing in my poop?

Changes in the shape or texture of stool can be concerning, but they are not always a sign of something serious. According to the available references, 'low caliber stool' or 'pencil thin stool' does not always indicate a specific medical issue.

Here are some potential causes:

1. Dietary Changes: Eating different foods can affect stool consistency and shape.
2. Constipation: This can lead to changes in stool appearance, sometimes making it look stringy or thin.
3. Other Gastrointestinal Changes: Conditions affecting the digestive tract might alter stool form, but not all changes are harmful.

If you experience persistent changes in stool shape or other symptoms like pain or bleeding, it might be helpful to talk to a healthcare provider for further evaluation.