Emesis, the medical term for vomiting, is a forceful reflex that expels stomach contents. Nonbilious emesis is classified by the lack of a green or yellow-green color, which is caused by the presence of bile. Bile is a digestive fluid produced by the liver and stored in the gallbladder. Its absence in vomit suggests that the obstruction or irritation causing the vomiting is located high in the gastrointestinal tract, above where the common bile duct empties into the small intestine. While often caused by common, less severe issues, nonbilious vomiting can also signal serious conditions requiring immediate attention.
Common Underlying Mechanisms
Nonbilious emesis results from issues that prevent stomach contents from moving forward or from general irritation of the stomach lining. Causes are broadly categorized into mechanical obstructions and inflammatory or infectious processes.
Mechanical obstructions are concerning, especially in infants, because they prevent food from passing out of the stomach. The most common surgical cause is infantile hypertrophic pyloric stenosis (IHPS). This involves a progressive thickening of the muscle at the pylorus, the valve connecting the stomach to the small intestine, which narrows the opening and creates a gastric outlet obstruction.
The blockage forces the stomach to contract harder, resulting in classic projectile vomiting. This forceful, nonbilious expulsion typically begins in infants between three and six weeks of age. The nonbilious nature occurs because the obstruction is located before the small intestine, preventing bile from entering the stomach contents.
Non-obstructive causes include viral gastroenteritis, where vomiting results from irritation and inflammation of the stomach lining. Gastroesophageal reflux (GER) is also frequent, particularly in infants, where stomach contents flow back into the esophagus due to an immature lower esophageal sphincter. These causes are less likely to produce the forceful, projectile vomiting seen with a physical obstruction.
Identifying Warning Signs
While most episodes of nonbilious vomiting resolve on their own, certain signs indicate a medical emergency requiring immediate evaluation. The most serious concern is severe dehydration, which can be rapid in infants and young children.
Signs of dehydration include lethargy, a lack of tears when crying, dry mucous membranes, and decreased frequency of urination. In infants, a sunken fontanelle, the soft spot on the top of the head, is a physical sign of significant fluid loss.
The nature of the vomiting itself can be a warning sign, particularly if it is consistently projectile, meaning the vomit is forcefully ejected a distance from the mouth. Vomiting that is frequent and prevents the patient from keeping down fluids for more than a few hours also warrants prompt medical attention.
Systemic symptoms accompanying the emesis should be considered red flags. These include a high fever, which may suggest a serious infection like meningitis. Severe, unrelenting abdominal pain or a noticeable bulging of the abdomen can point to a serious underlying condition, such as a major intestinal issue.
Diagnosis and Clinical Management
A healthcare provider begins the diagnostic process with a thorough physical examination and a detailed history of the vomiting episodes. They assess for signs of dehydration and metabolic imbalance caused by the loss of stomach acid. In cases of pyloric stenosis, the physician may attempt to palpate an “olive-shaped” mass—the thickened pyloric muscle—in the upper right abdomen.
The standard diagnostic tool for confirming mechanical obstructions like pyloric stenosis is an abdominal ultrasound. This non-invasive imaging technique provides a detailed view of the pylorus, allowing for measurement of muscle thickness and channel length. Blood tests are also routinely performed to check for electrolyte imbalances, such as the hypochloremic, hypokalemic metabolic alkalosis that often occurs with prolonged vomiting.
Clinical management is determined by the underlying cause and the patient’s condition. For non-obstructive causes like gastroenteritis, the primary treatment is supportive care focused on correcting dehydration and electrolyte loss. This often involves administering intravenous fluids and closely monitoring the patient’s fluid intake and output.
When a mechanical obstruction like pyloric stenosis is confirmed, the treatment is surgical. Before the operation, 24 to 48 hours are often necessary to fully correct any dehydration and electrolyte abnormalities. The corrective procedure, called a pyloromyotomy, involves the surgeon cutting through the outer layer of the thickened pyloric muscle to loosen the muscle ring. This allows food to pass normally from the stomach into the small intestine.