Nausea

Nausea (Latin nausea, from Greek, nausiē, "motion sickness", feeling sick," queasy or "wamble" ), is a sensation of unease and discomfort in the upper stomach with an involuntary urge to vomit. It usually, but not always, leads to vomiting.

A common cause is motion sickness (see definition, above) and gastroenteritis (a stomach infection) or food poisoning but nausea also frequently occurs as a medication side effect and in pregnancy. There are some medications, called antiemetics, that improve symptoms of nausea, including diphenhydramine, metoclopramide and ondansetron. Nausea may also be caused by stress and depression.

Differential diagnosis
The causes of nausea are many. One organization listed 700 in 2009. Gastrointestinal infections (37%) and food poisoning are the two most common causes. While side effects from medications (3%) and pregnancy are also relatively frequent. In 10% of people the cause remains unknown.

Food poisoning
Food poisoning usually causes an abrupt onset of nausea and vomiting one to six hours after ingestion of contaminated food and lasts for one to two days. It is due to toxins produced by bacteria in the food.

Medications
Most medications can potentially cause nausea. Some of the most frequently associated include chemotherapy regimens and general anaesthetic agents.

Pregnancy
Nausea or "morning sickness" is a common during pregnancy. In the first trimester nearly 80% of women have some degree of nausea. Pregnancy should therefore be considered as a possible cause of nausea in any women of child bearing age. While usually it is mild and self limiting severe cases known as hyperemesis gravidarum may require treatment.

Disequilibrium
A number of conditions involving balance such as motion sickness and vertigo can lead to nausea and vomiting.

Stress and depression
Nausea may be caused by stress and depression.

Potentially serious
While most causes of nausea are not serious, some serious causes do occur. These include: diabetic ketoacidosis, surgical problems (pancreatitis, small bowel obstruction, meningitis, appendicitis, cholecystitis), Addisonian crisis, Choledocholithiasis (from gallstones) and hepatitis, signs of carbon monoxide poison among others.

Diagnostic approach
Often no investigations are needed, however basic lab tests may be appropriate. If a bowel obstruction is considered, abdominal x-rays may be useful.

Treatment
If dehydration is present, rehydration with oral electrolyte solutions is preferred. If this is not effective, intravenous rehydration may be required.

Medications
Dimenhydrinate (Gravol) is an inexpensive and effective medication for preventing postoperative nausea and vomiting. Meclozine is another antihistamine antiemetic. In certain people, cannabinoids may be effective in reducing chemotherapy associated nausea and vomiting. Ondansetron (Zofran) is effective for nausea and vomiting but is expensive. Pyridoxine or metoclopramide are the first line treatments for pregnancy related nausea and vomiting. Medical marijuana may be prescribed where allowed for certain indications.

Prognosis
While short-term nausea and vomiting are generally harmless, they may sometimes indicate a more serious condition. When associated with prolonged vomiting, it may lead to dehydration and/or dangerous electrolyte imbalances.

Epidemiology
Nausea and or vomiting is the main complaint in 1.6% of visits to family physicians in Australia. However only 25% of people with nausea visit their family physician. It is most common in those 15–24 years old and less common in other ages.