Bilious vomiting syndrome

Overview

Bilious vomiting syndrome (BVS) refers to the recurrent vomiting of bile-stained fluid, typically green or yellow in color, often seen in both humans and animals (notably dogs). In humans, bilious vomiting may indicate a serious underlying condition such as an intestinal obstruction, especially in neonates and infants. In veterinary medicine, BVS is most commonly described in dogs, where it is considered a functional gastrointestinal disorder rather than a structural problem. Early recognition and appropriate evaluation are critical to determine the underlying cause and initiate suitable treatment.

Causes

The causes of bilious vomiting vary significantly between humans and animals, and based on age and context. In general, it results from the reflux of bile from the duodenum into the stomach, followed by vomiting. Common causes include:

• Duodenal obstruction – such as malrotation with volvulus or duodenal atresia in neonates

• Gastrointestinal motility disorders

• Prolonged fasting or empty stomach – particularly in dogs with BVS

• Gastroesophageal reflux or delayed gastric emptying

• Post-surgical complications involving the gastrointestinal tract

• Pancreatic or hepatobiliary disease

In veterinary cases, BVS is often diagnosed when a dog vomits bile, typically early in the morning or late at night, with no other significant abnormalities present.

Symptoms

Bilious vomiting syndrome is characterized by the appearance of bile in the vomit. Key symptoms include:

• Vomiting of green or yellow fluid, especially on an empty stomach

• Nausea or retching before vomiting

• Abdominal discomfort or signs of colic

• Loss of appetite or reduced food intake

• Lethargy in severe or prolonged cases

• Signs of dehydration if vomiting is persistent

In humans, bilious vomiting is a red flag in neonates and should prompt immediate evaluation for possible intestinal obstruction.

Diagnosis

Diagnosis involves identifying the underlying cause of bile reflux and vomiting. Diagnostic steps may include:

• Clinical history and physical examination

• Abdominal ultrasound or X-ray – to assess for obstruction or anatomical abnormalities

• Upper gastrointestinal series (barium studies) in neonates or infants

• Blood tests – to evaluate liver and pancreatic function

• Endoscopy – in chronic or unexplained cases

• Response to fasting or feeding patterns – especially in veterinary cases

In dogs, BVS is often a diagnosis of exclusion after ruling out other gastrointestinal diseases.

Treatment

Treatment of bilious vomiting syndrome depends on the underlying cause:

• Surgical intervention – required if an obstruction is present, especially in neonates

• Feeding management:

  • Small, frequent meals

  • Feeding late at night or early morning to prevent empty stomach episodes (in dogs)

• Medications:

  • Proton pump inhibitors or H2 blockers to reduce gastric acidity

  • Prokinetic agents like metoclopramide to enhance gastric motility

  • Anti-nausea medications such as ondansetron

• Dietary changes – easily digestible or prescription GI diets for pets

• Supportive care – fluids and electrolyte replacement if dehydration is present

Prognosis

The prognosis for bilious vomiting syndrome varies with the cause. In human infants with a surgical obstruction, prompt surgical correction can result in a good outcome. In adults and animals, BVS with no structural abnormality generally has a favorable prognosis when managed appropriately with dietary and medical strategies. However, failure to treat underlying conditions like intestinal blockage or pancreatic disease can lead to serious complications. Long-term monitoring and supportive care are essential for chronic cases.