Hiccups (or hiccoughs), medical term singultus (rare plural: singultūs), are an unpleasant phenomenon, experienced by everyone on occasion, and usually self-limiting. However the much rarer intractable chronic form can be extremely debilitating.

Epidemiology

Hiccups are a symptom that has probably been experienced by everyone at some point in their lives. Chronic intractable hiccups are rare.

Clinical presentation

Acute hiccups are those lasting less than 48 hours, and are usually self-limiting.

Chronic, persistent hiccups refers to any episode with a duration greater than 48 hours. Intractable hiccups, sometimes defined as those lasting more than two months, can be very disabling, causing inability to sleep, depression, and chronic exhaustion, with secondary deleterious effects on an individual's health.

Pathology

Curiously for such a common, everyday phenomenon, the direct cause and pathogenesis of this symptom remains unknown.

The accepted hypothesis is that hiccups occur secondary to dysfunction of the swallowing reflex arc, of which there are three main components ¹:

1. afferent 

   • nerves within the phrenic and vagus nerves, and also the thoracic sympathetic chain

2. central processor

   • least understood portion

   • likely involvement of the brainstem and hypothalamus

3. efferent limb

   • nerve supply to the responsible musculature including the diaphragm, anterior scalenes, intercostals, and glottis

Neurotransmitters implicated include GABA and dopamine.

Etiology

Acute hiccups 

• sudden/marked gastric distension e.g. large meal, carbonated beverages

• alcohol

• smoking

• psychogenic factors

Chronic hiccups

More than 100 causes have been identified ^1,3:

• idiopathic

• psychogenic

  • anxiety

  • stress

  • phobias

• gastrointestinal

  • abdominal abscess

  • abdominal neoplasm

  • diaphragmatic pathology

    • hernia

    • neoplasm

  • gastric distension

  • gastroesophageal reflux disease

  • hiatus hernia

  • esophagitis

  • esophageal carcinoma ³

  • pancreatic carcinoma ³

  • pancreatitis ³

  • peptic ulcer disease

• infection

  • syphilis

  • pneumonia

  • pleurisy, empyema

  • COVID-19 ⁵

• iatrogenic

  • anesthesia-related

• neurological

  • epilepsy

  • head injury

  • malignancy

  • meningoencephalitis

  • multiple sclerosis

  • neuromyelitis optica

  • Parkinson disease

  • stroke e.g. lateral medullary syndrome

  • area postrema syndrome

• metabolic/endocrine

  • diabetes mellitus

  • electrolyte disturbances e.g. hyponatremia, hypokalemia, hypocalcemia, hypocapnia

  • ethanol excess

• thoracic

  • lung cancer

  • myocardial infarction

• pharmacological

  • barbiturates

  • benzodiazepines e.g. diazepam

  • methyldopa

  • steroids e.g. dexamethasone

Radiographic features

The features of the underlying causes are described in their respective articles.

Treatment and prognosis

Folk remedies abound for the treatment of acute hiccups.

Initially therapy is directed to the specific cause.

In addition for the more serious chronic intractable form there are pharmacological and non-pharmacological interventions.

History and etymology

Singultus is the Latin for sobbing, gasping. As a fourth declension noun, its plural form is singultūs. The line above the 'u' is called a macron and its use in phonetics denotes a long vowel sound ⁴.