Retching, commonly referred to as dry heaving, is an involuntary physiological process involving the forceful, rhythmic contraction of the abdominal muscles and the diaphragm. This action is the body’s attempt to expel stomach contents, but it fails to do so, resulting in the characteristic heaving motion without the release of material. The sensation of retching is often closely linked to nausea, the unpleasant feeling of an urge to vomit, and it serves as a preparatory reflex in the digestive tract.
The Muscular Mechanics of Retching
The physical mechanism of retching involves a complex, coordinated effort between several muscle groups controlled by a brainstem neural network. During a retch, the body executes a deep inspiration against a closed glottis, which prevents air from entering the lungs.
The inspiratory action of the diaphragm is immediately opposed by the expiratory contraction of the abdominal wall muscles. This conflicting muscular action creates a significant negative pressure within the chest cavity and a high positive pressure in the abdominal cavity, effectively squeezing the stomach. The rhythmic abdomino-thoracic contractions pull the stomach and its contents upwards toward the chest and esophagus.
Retching vs. Vomiting: A Key Difference
The distinction between retching and full vomiting lies primarily in the status of the upper esophageal sphincter (UES) and the resulting outcome. Retching represents the preparatory phase where stomach contents are moved upward, but the UES, the ring of muscle at the top of the esophagus, remains constricted between the rhythmic contractions. This constriction acts as a barrier, preventing the material from passing through and being expelled from the mouth.
Vomiting, or emesis, is the final stage that leads to the forceful ejection of gastric material. This occurs when the UES relaxes to allow the contents to pass and the musculature generates sufficient pressure to overcome the resistance. During retching, the airway is protected by the closing of the glottis, and the lack of UES relaxation prevents the expulsion of stomach material.
Common Triggers and Root Causes
A wide array of stimuli can activate the central pattern generator in the brainstem that controls the retching reflex. One of the most common causes is a post-vomiting reflex, where the stomach is already empty after a bout of illness like food poisoning or gastroenteritis, and the body continues the motion out of reflex. High levels of alcohol consumption can also trigger retching, as the body attempts to remove the toxic substance from the stomach.
Conditions affecting the gastrointestinal tract, such as gastroesophageal reflux disease (GERD) or gastritis, can frequently lead to dry heaving due to chronic irritation of the esophageal lining. Hormonal changes are another significant cause, most notably the severe nausea and retching experienced during the first trimester of pregnancy, commonly called morning sickness.
Intense physical activity, especially high-intensity exercise performed on a full stomach, can cause the diaphragm to contract and initiate retching. Psychological distress, such as high anxiety or sudden, intense stress, can also trigger the reflex. Common environmental triggers include exposure to strong, unpleasant odors or certain medications known to cause nausea.
Identifying Warning Signs
While retching is often a temporary and self-limiting symptom, certain accompanying signs suggest the need for professional medical evaluation. If retching persists for more than 24 to 48 hours without relief, or if it is accompanied by the inability to keep down any fluids, this may indicate a risk of dehydration. Signs of severe dehydration include a dry mouth, reduced frequency of urination, or dizziness when standing.
Immediate medical attention is warranted if dry heaving is accompanied by serious warning signs:
- Severe abdominal pain, a high fever, or a stiff neck.
- The presence of blood in expelled material, which may appear as bright red streaks or dark, granular “coffee grounds.”
- Experiencing confusion or a severe, unusual headache requires prompt medical assessment.