What is it?

• Hiccups are a common condition that affects nearly everyone. Hiccups involve the involuntary contraction of the diaphragm — the muscle that separates your chest from your abdomen and plays an important role in breathing. Each contraction is followed by a sudden closure of your vocal cords, which produces the characteristic "hic" sound.
• Many people have home remedies for hiccups that they swear by, ranging from breathing into a paper bag to swallowing a teaspoon of granulated sugar.
• Hiccups may result from a large meal, alcoholic beverages or sudden excitement. Rarely, hiccups may be a sign of an underlying medical condition. A bout of hiccups usually lasts only a few minutes. But in some people, about one in 100,000, hiccups may persist for months. This can result in malnutrition and exhaustion.

Symptoms

The characteristic sound of a hiccup, sometimes preceded by a slight tightening sensation in your chest, abdomen or throat, are the only signs and symptoms associated with hiccups. The number of hiccups a minute typically ranges between four and 60.

Causes

The most common triggers for short-term hiccups include:

• Eating too much
• Drinking carbonated beverages
• Excessive consumption of alcohol
• Sudden temperature changes
• Excitement or emotional stress

Hiccups that last more than 48 hours may be caused by a variety of factors, which are generally grouped into the following categories:

Nerve damage or irritation

The most common cause of long-term hiccups is damage or irritation of the vagus nerves or phrenic nerves, which serve the diaphragm muscle. Factors that may cause damage or irritation to these nerves include:

• A hair or something else in your ear touching your eardrum
• Sore throat or laryngitis
• A tumor, cyst or goiter in your neck
• Gastroesophageal reflux

Central nervous system disorders

A tumor or infection in your central nervous system or damage to your central nervous system as a result of trauma can disrupt your body's normal control of the hiccup reflex. Examples include:

• Stroke
• Multiple sclerosis
• Tumors
• Meningitis
• Encephalitis
• Traumatic brain injury

Metabolic disorders and drugs

• Alcoholism
• Anesthesia
• Barbiturates
• Diabetes
• Electrolyte imbalance
• Kidney failure
• Steroids
• Tranquilizers 

Risk factors

Sex

Men are much more likely to develop long-term hiccups than are women.

Surgery

Several factors related to surgical procedures appear to increase your risk of developing long-term hiccups. They include:

• General anesthesia
• Intubation, in which a tube is placed down your throat to help you breathe
• Neck extension, which is necessary during intubation
• Abdominal distension, which is common after endoscopic procedures performed through small incisions
• Organ manipulation

Mental or emotional issues

Anxiety, stress and excitement have been associated with some cases of short-term and long-term hiccups. 

Complications

Prolonged hiccups may interfere with:

• Speech
• Eating
• Sleeping
• Post-surgical wound healing

Diagnosis

If your doctor suspects an underlying medical condition may be causing your hiccups, he or she may recommend one or more of the following tests:

Laboratory tests

Samples of your blood may be checked for signs of:

• Infection
• Diabetes
• Kidney disease

Imaging tests

These types of tests may be able to detect anatomical abnormalities that may be affecting the vagus nerve, phrenic nerve or diaphragm. Imaging tests may include:

• Chest X-ray
• Computerized tomography (CT) scan
• Magnetic resonance imaging (MRI)

Endoscopic tests

These procedures utilize a thin, flexible tube containing a tiny camera, which is passed down your throat to check for problems in your esophagus or windpipe. 

References:

http://www.nhs.uk/Conditions/Hiccup/Pages/Treatment.aspx

http://www.medicinenet.com/hiccups/article.htm

http://www.emedicinehealth.com/hiccups/article_em.htm

https://en.wikipedia.org/wiki/Hiccup