Normal Colour of Bile
Bile is normally green to yellow-green in colour, though the exact shade varies depending on the concentration of bile pigments and the clinical context being observed.
Bile Pigment Composition and Colour
The colour of bile is determined primarily by its pigment content, which consists of bilirubin and biliverdin:
- Biliverdin (green pigment) and bilirubin (yellow-orange pigment) are the two main bile pigments present in gallbladder and hepatic duct bile 1
- Fresh hepatic bile typically appears yellow-green due to the mixture of these pigments 1
- The concentration and ratio of these pigments can vary, affecting the overall colour appearance 1
Clinical Context Matters
The perceived "normal" colour of bile depends significantly on where and how it is being observed:
In Vomiting (Bilious Emesis)
- There is considerable disagreement among healthcare providers about what colour represents bile in vomit 2
- In a study of healthcare professionals and parents, 49% of general practitioners and 71% of parents thought yellow was the best colour match for bile, while many did not recognize green as appropriate 2
- However, green vomiting in a newborn is considered a surgical emergency requiring expeditious referral, as it may indicate intestinal obstruction 2
- Yellow vomit does not exclude intestinal obstruction, but the presence of green vomiting requires urgent evaluation 2
In Gallbladder Bile
- Gallbladder bile in most vertebrates contains appreciable amounts of both biliverdin and bilirubin conjugates 1
- The bile can appear yellow to green depending on the relative concentrations of these pigments 1
In Small Bowel Content
- Bile pigments darken the small-bowel lumen, with the colour varying based on concentration and bowel transit time 3
- Patients with constipation tend to have brighter (lighter) bile-stained small bowel water content, while those with diarrhea have darker content, reflecting differences in bile pigment concentration 3
Common Pitfall
Do not assume bile must be a single specific colour. The colour ranges from yellow to green depending on the concentration of bilirubin (yellow-orange) versus biliverdin (green), the clinical setting, and individual variation 1, 2. In clinical practice, particularly when evaluating newborns for intestinal obstruction, green vomiting should always be treated as a surgical emergency regardless of whether observers agree it represents "bile" 2.