Causes of Hiccups
Hiccups are primarily caused by irritation of the phrenic and vagal nerves or their central connections, with gastroesophageal reflux disease (GERD) being the most common underlying cause in persistent cases. 1
Pathophysiology of Hiccups
Hiccups result from a complex reflex arc involving:
- Afferent limb: Primarily vagal and phrenic nerves, with sympathetic chain involvement (T6-T12)
- Central processor: Hiccup center in the brainstem (midbrain)
- Efferent limb: Phrenic nerve to diaphragm and intercostal muscles, followed by glottic closure
The characteristic "hic" sound occurs when inspired air is suddenly stopped by glottic closure following the involuntary contraction of the diaphragm and intercostal muscles 2.
Common Causes of Hiccups
Gastrointestinal Causes
- Gastroesophageal reflux disease (GERD) - most common cause of persistent hiccups 1, 3
- Gastritis or peptic ulcer disease
- Gastric distention (from overeating or carbonated beverages)
- Esophagitis
- Pancreatitis
Central Nervous System Causes
- Stroke
- Brain tumors
- Head trauma
- Multiple sclerosis
- Central nervous system infections
Thoracic Causes
- Myocardial infarction
- Pericarditis
- Pneumonia
- Pleuritis
- Thoracic surgery
Metabolic/Toxic Causes
- Alcohol consumption
- Uremia (kidney failure)
- Electrolyte imbalances
- Diabetes
Medication-Induced Hiccups
- Steroids
- Benzodiazepines
- Chemotherapy agents
- Anesthetic agents
- Anti-Parkinson medications 2
Psychogenic Causes
- Stress
- Anxiety
- Excitement
Other Causes
- Supragastric belching (air suction or injection methods) 4
- Foreign body irritation of the ear (Arnold's ear-cough reflex can sometimes trigger hiccups) 4
- High altitude exposure 4
- Surgical sutures irritating bronchial mucosa 4
- Mediastinal lesions 4
Classification by Duration
- Acute hiccups: Episodes lasting less than 48 hours
- Persistent hiccups: Episodes lasting more than 48 hours but less than 2 months
- Intractable hiccups: Episodes lasting more than 2 months 2
Diagnostic Approach for Persistent Hiccups
For hiccups persisting beyond 48 hours, a systematic evaluation should be conducted:
- Detailed history: Focus on medication use, recent procedures, and gastrointestinal symptoms
- Physical examination: Evaluate for abdominal, neurological, or cardiopulmonary abnormalities
- Laboratory tests: Complete blood count, electrolytes, renal function, liver function
- Upper GI evaluation: Endoscopy, pH monitoring, and manometry (should be performed systematically in chronic hiccup patients) 5
- Imaging: Chest X-ray, abdominal ultrasound, CT of chest/abdomen/brain as indicated by clinical suspicion
Clinical Pearls and Pitfalls
- Persistent hiccups should never be dismissed as benign; they may indicate serious underlying pathology 2
- GERD is frequently underdiagnosed as a cause of persistent hiccups 3
- Hiccups that stop during sleep suggest a psychogenic component
- Hiccups can cause significant morbidity through sleep deprivation, weight loss, and psychological distress 5
- Unlike normal belching, supragastric belching (which can trigger hiccups) stops during sleep, distraction, or when the patient speaks 4
By understanding the diverse causes of hiccups and following a systematic diagnostic approach, clinicians can effectively identify and treat the underlying cause, particularly in cases of persistent or intractable hiccups.