Nausea and vomiting are two symptoms that are usually considered to be an indication of a disruption in the alimentary tract (gut). In most cases it is associated with alimentary pathology and accompanied by other symptoms like changes in bowel movements, heartburn, loud stomach noises (borborygmi), abdominal pains or cramps, excessive belching or flatulence. It is also often related to eating and aggravated after meals. Most alimentary causes of vomiting are due to infections, food poisoning, overdistension or irritation of the upper gastrointestinal tract. However, there are times when vomiting may not be related to any pathology within the alimentary tract and usually these conditions present without any of the associated gastrointestinal signs and symptoms.
Nervous Control of Vomiting
The vomiting center in the brain stem are multiple nuclei which receives impulses from other areas of the body, primarily the digestive tract, and other areas of the brain. Following stimulation of the vomiting center, impulses travel to the gastrointestinal tract, abdominal muscles and diaphragm. These impulses reach these sites via cranial nerves V, VII, IX, X, XII and the spinal nerves. The vomiting process then commences.
One of the other significant areas in the brain associated with the vomiting center is the chemoreceptor trigger zone (CTZ) in the medulla. If this zone is stimulated, it can send impulses to the vomiting centers and lead to vomiting. The chemoreceptor trigger zone may be stimulated by various substances in the bloodstream including abnormally high levels of certain metabolites, hormones, toxins and drugs.
Another important associated system is the vestibular system of the inner ear which can send impulses to the vomiting center. This system is responsible for the sense of balance and orientation and these factors may sometimes contribute to nausea and vomiting as is seen in motion sickness. However, non-alimentary causes of vomiting are not restricted to abnormal stimulation from these areas. There may be several other stimuli and trigger factors that may cause vomiting through less common or even unknown pathways.
Non-Alimentary Causes of Vomiting
Vomiting that is due to causes other than gastrointestinal disturbances will most likely not present with very severe or prominent signs and symptoms such as diarrhea or constipation, abdominal pain or excessive gas. However, other clinical features may be present depending on the cause as discussed below. In women, pregnancy is one of the common physiological causes of vomiting that is not associated with alimentary pathology.
Drugs and Substances
Nausea and vomiting are common adverse effects of many drugs and should be considered if there is recent use of medication. The more likely causative drugs may include :
- Chemotherapeutic agents (cancer drugs)
- Opioid analgesics
- Cardiac glycosides like digoxin
Alcohol, particularly when consumed in excess, and most illicit substances may cause nausea and vomiting. Oral medication and any other ingested substance may also cause nausea and vomiting due to irritation of the alimentary tract. This arises a short while after consumption and is more likely to occur in a person with gastritis, peptic ulcer disease and acid reflux. However, when these substances stimulate the chemoreceptor trigger zone, nausea and vomiting are more likely to arise between 30 minutes and 2 hours or sometimes longer after oral ingestion. With illicit substances that are inhaled, injected or smoked, the effects are more likely to arise within minutes.
Disorders of the central and peripheral nervous systems may also contribute to vomiting without any involvement of the gastrointestinal tract. It usually presents with other signs and symptoms which varies depending on the cause.
- Migraine – head pain, sensitivity to light, visual disturbances and/or dizziness.
- Raised intracranial pressure – headache, confusion, lethargy, drowsiness and/or seizures.
- Labyrinthitis – vertigo, hearing loss, ear pain, loss of balance and/or fatigue.
- Meniere’s disease – vertigo, pressure in the ears, hearing loss and/or tinnitus.
- Vasovagal response (fear, severe pain, shock) – paleness, dim vision, sweating or cold and clammy skin.
Various metabolic disorders can cause both nausea and vomiting and is primarily associated with circulating metabolites and hormones stimulating the chemoreceptor trigger zone (CTZ).
- Addison’s disease – hypotension, hypoglycemia, weight loss, fatigue, depression, muscle aches, joint pains, hyperpigmentation and/or muscle weakness.
- Diabetic ketoacidosis – excessive thirst, frequent urination, abdominal pain, weakness, confusion, shortness of breath and fruity odor of breath.
- Hypercalcemia – excessive thirst, frequent urination, abdominal pain, muscle weakness and pain, joint pains, confusion, fatigue and loss of appetite.
- Kidney failure (more prominent with chronic failure) – decreased urination, edema (swelling), shortness of breath, fatigue, loss of appetite, itchy skin and muscle cramps.
- Liver failure – jaundice, right upper abdominal pain (liver pain), disorientation and/or drowsiness.
Psychiatric or Psychogenic
Vomiting may be seen with several psychiatric conditions but is largely associated with the ingestion of inedible substances, adverse effects of medication used to treat these disorders and voluntarily stimulating pharyngeal reflex. Vomiting may also occur with certain emotions like fear (vasovagal response), traumatic experiences and seeing or thinking of disturbing events. With regards to memory, other stimuli like sound or even smells may elicit vomiting if there are very traumatic and unpleasant memories associated with it. Eating disorders like anorexia nervosa or bulimia must always be considered as a possible cause of vomiting.