Green vomit often causes immediate concern because the color signals a deviation from a typical illness. The green hue is most frequently caused by the presence of bile, a digestive fluid that should ordinarily pass through the small intestine. While seeing bile in vomit can sometimes be a non-urgent sign that the stomach is empty, it also serves as a distinct warning sign for serious, potentially life-threatening conditions, especially in infants.
The Mechanism of Color Change
The distinct green color in vomit is directly linked to bile, a fluid continuously produced by the liver and stored in the gallbladder. Bile primarily breaks down fats so they can be absorbed in the small intestine. The color is due to bile pigments, specifically biliverdin and bilirubin, which are products of broken-down hemoglobin. Biliverdin is the pigment responsible for the green coloration.
Bile is normally released from the gallbladder into the duodenum, the first section of the small intestine, just past the stomach. Green vomit, often called bilious vomiting, occurs when this fluid travels backward into the stomach and is then expelled. This backward flow, known as bile reflux, can be triggered by forceful vomiting when the stomach is empty or by a physical obstruction in the digestive tract. The color may range from bright yellow-green to dark green, depending on the concentration of bile pigments.
Non-Urgent Causes of Green Vomit
In many instances, green or yellow-green vomit is not a sign of a serious medical emergency, particularly in adults. The most common cause is simple bile reflux following prolonged or repeated episodes of vomiting. This occurs after the stomach has emptied its contents, such as during gastroenteritis, food poisoning, or severe morning sickness.
When the stomach is empty, the retching reflex can force the pyloric valve open, allowing bile from the duodenum to reflux into the stomach and be expelled. This bile-stained vomit is generally self-limiting and resolves once the underlying illness passes. Another non-urgent cause can be the ingestion of highly pigmented green food, beverages, or medications, where the color is simply from undigested dye.
Serious Conditions Associated with Green Vomit
While green vomit can be non-urgent in adults, it is a significant warning sign for severe, time-sensitive problems. In adults, the most concerning cause is a bowel obstruction, where a physical blockage prevents the normal passage of intestinal contents.
Bowel Obstruction in Adults
A bowel obstruction can occur anywhere along the small or large intestine due to conditions like hernias, adhesions from prior surgery, tumors, or severe constipation. When the intestine is blocked, bile and other digestive fluids build up and are forced backward into the stomach, leading to bilious vomiting. Symptoms often include severe, cramping abdominal pain, abdominal distention, and an inability to pass gas or stool. This condition is a surgical emergency because the blockage can cut off blood flow to the intestine, leading to tissue death and perforation.
Bilious Vomiting in Infants
The presence of green vomit in a newborn or young infant is treated with heightened urgency and is considered a surgical emergency until proven otherwise. In this age group, bilious vomiting strongly suggests a gastrointestinal obstruction, often caused by congenital abnormalities. Conditions such as intestinal malrotation, where the intestine is positioned incorrectly, or volvulus, a twisting of the intestine, can present this way.
A volvulus can rapidly cut off the blood supply to the bowel, leading to tissue death (ischemia) and requiring immediate surgical intervention. Other causes include Hirschsprung disease, which affects nerve cells in the colon, or meconium ileus, a blockage caused by the baby’s first stool. Because infants can appear healthy even as damage occurs, green vomit is the most important clinical sign requiring immediate attention.
Triage: When to Seek Immediate Medical Attention
A single instance of green vomit should be monitored carefully, but certain accompanying symptoms necessitate an immediate trip to the emergency department. These urgent indicators include signs of severe dehydration, such as sunken eyes, profound lethargy, a rapid heartbeat, and passing little to no urine. Severe, unrelenting abdominal pain that is disproportionate to the vomiting is also a major warning sign.
Any instance of green vomit in a newborn or young infant must be treated as an emergency and requires immediate medical evaluation. For adults, other red-flag symptoms include high fever, vomiting lasting longer than 48 hours, or the inability to keep down any fluids.