Hernias are protrusions of internal tissue or organs through a weakness or opening in the structures that normally contain them. They most commonly involve the abdominal wall or groin, although the term also includes internal hernias and hiatus hernias in which abdominal structures pass through an anatomical opening in the diaphragm. A hernia can contain bowel, fatty tissue or other structures, and its clinical appearance depends on the location and contents.
Some hernias produce a visible or palpable lump that becomes more prominent with coughing, lifting or standing and reduces when lying down, whereas internal hernias may have no external bulge. The fundamental anatomical feature is displacement of tissue through a defect or weakened area rather than simply swelling of the tissue itself.
Major types include inguinal, femoral, umbilical, incisional, epigastric, lumbar, stoma-associated and hiatus hernias. Inguinal hernias occur in the groin and are especially common in men, while femoral hernias occur lower in the upper thigh and can have a relatively narrow neck. Umbilical hernias occur at or near the navel, whereas incisional hernias develop through a previous surgical incision. Hiatus hernias involve movement of part of the stomach through the diaphragm and are associated particularly with reflux-related symptoms rather than an external abdominal lump. Different types have different anatomical mechanisms and complication risks, so the generic word hernia does not provide enough information to determine prognosis or treatment.
Hernia formation can reflect congenital anatomical weakness, acquired tissue weakness or increased mechanical pressure. Ageing, obesity, pregnancy, chronic coughing, repeated straining and previous abdominal surgery can contribute to particular forms. Activities involving heavy lifting do not necessarily create a hernia in otherwise healthy tissue by themselves, but repeated increases in intra-abdominal pressure can reveal or enlarge a pre-existing weakness. A persistent cough or chronic constipation can therefore contribute indirectly through repeated pressure. Some hernias remain small and relatively asymptomatic, while others enlarge progressively and cause discomfort, heaviness or functional complications.
The principal serious complications are incarceration and strangulation. An incarcerated hernia is trapped outside the abdominal cavity and cannot be reduced normally. If the blood supply to the trapped contents becomes compromised, the hernia is strangulated, creating ischaemia and eventual tissue death. When bowel is trapped, obstruction can develop because intestinal contents cannot pass through the constricted segment. Sudden enlargement of a hernia, severe or rapidly increasing pain, tenderness, redness, vomiting, abdominal distension, constipation or symptoms of intestinal obstruction can therefore indicate an emergency. Strangulated hernias can become life-threatening because bowel necrosis and perforation may lead to peritonitis and systemic infection.
Diagnosis commonly involves clinical examination, particularly for external hernias. The examiner may assess the lump while the patient is standing, coughing or straining and determine whether it reduces when lying down or with gentle pressure. Ultrasound, computed tomography or magnetic resonance imaging may be used when the diagnosis is uncertain, when the hernia is small or occult, or when complications or unusual anatomy need evaluation. Hiatus hernias are investigated differently because they are internal and often present through reflux or upper gastrointestinal symptoms. Imaging and endoscopy may therefore be used according to the suspected anatomical problem rather than according to a universal hernia test.
Management depends on hernia type, size, symptoms, reducibility and risk of complications. Some asymptomatic or minimally symptomatic hernias can be monitored in appropriately selected patients, whereas symptomatic or enlarging hernias may be repaired surgically. Repair generally involves returning protruding tissue to its appropriate position and reinforcing the weakened area, often with a synthetic or biological mesh depending on circumstances. Emergency surgery may be necessary for strangulation, obstruction or other evidence of compromised bowel. Lifestyle measures such as maintaining a healthy weight, treating persistent cough and avoiding unnecessary straining can reduce pressure on vulnerable abdominal tissues, although they cannot reliably eliminate an established structural defect.
Hiatus hernias illustrate why hernia symptoms are not limited to visible lumps. When part of the stomach moves through the diaphragm, it can facilitate gastro-oesophageal reflux and produce heartburn, regurgitation or swallowing-related symptoms. Most hiatus hernias are not managed in the same way as abdominal-wall hernias; symptom control may involve dietary measures and medicines for reflux, while surgery is reserved for selected patients with persistent severe symptoms or complications. A hernia also differs from an abscess, tumour or swollen lymph node because its defining feature is protrusion through an anatomical defect. Similarly, not every groin lump is a hernia, making examination important when the diagnosis is uncertain.
Hernias have practical significance because a seemingly harmless lump can occasionally progress to obstruction or strangulation, yet many remain stable and cause few symptoms. A common misconception is that every hernia inevitably requires immediate surgery; management is individualised according to anatomy and clinical circumstances. Another misconception is that successful reduction permanently cures the defect; tissue can protrude again unless the underlying opening is adequately repaired. The relationship between hernias and intestinal obstruction is particularly important because bowel trapped within a hernia can become obstructed and then strangulated. Prompt assessment of a new, painful, irreducible or rapidly changing lump is therefore essential.
