Definition and epidemiology
A hernia is the abnormal protrusion of a viscus or tissue through a defect in the wall of the cavity that normally contains it. Abdominal wall hernias are classified by location:
- Inguinal hernia (K40) - most common type overall, accounts for roughly 70-75% of abdominal wall hernias; lifetime risk in men is approximately 25-30%, far higher than in women
- Femoral hernia (K41) - less common, but more frequent in women relative to other hernia types; higher strangulation risk
- Umbilical hernia (K42) - common in infants (often resolves spontaneously) and in adults with obesity, ascites, or multiple pregnancies
- Ventral/incisional hernia (K43) - occurs at a prior surgical incision site
- Diaphragmatic hernia (K44) - includes hiatal hernia, discussed separately as its own high-yield topic
- Other abdominal hernias (K45) - e.g., lumbar, obturator, spigelian
- Unspecified abdominal hernia (K46)
Inguinal hernias are subdivided into indirect (through the deep inguinal ring, lateral to the inferior epigastric vessels, congenital patent processus vaginalis) and direct (through Hesselbach triangle, medial to the inferior epigastric vessels, due to acquired wall weakness).
- Indirect inguinal hernia: lateral to inferior epigastric vessels, through deep inguinal ring, congenital (patent processus vaginalis)
- Direct inguinal hernia: medial to inferior epigastric vessels, through Hesselbach triangle, acquired weakness
- Femoral hernia: below the inguinal ligament, through femoral canal, highest strangulation risk, more common in women
- Richter hernia: only antimesenteric bowel wall herniates, no obstruction but strangulation possible
- Strangulated hernia = surgical emergency: pain, erythema, fever, systemic toxicity
- Mesh repair reduces recurrence compared to primary tissue repair
- Watchful waiting is acceptable for minimally symptomatic inguinal hernias in men
- Sliding hernia contains a partially extraperitoneal organ as part of the sac wall (e.g., cecum, bladder)
Etiology and risk factors
Hernias result from a combination of a structural weakness and increased intra-abdominal pressure.
- Congenital defect: patent processus vaginalis (indirect inguinal hernia)
- Acquired weakness of the abdominal wall musculature and fascia, worsened by aging and connective tissue disorders (e.g., Ehlers-Danlos syndrome)
- Chronic increased intra-abdominal pressure: chronic cough (smoking, COPD), chronic constipation, straining with urination (BPH), heavy lifting, pregnancy, ascites
- Obesity and prior abdominal surgery (risk factor for incisional hernia)
- Male sex and older age (inguinal hernia)
- Collagen disorders and family history
- Prematurity and low birth weight (pediatric inguinal hernia)
Pathophysiology
A fascial or muscular defect allows peritoneum, with or without abdominal viscera (bowel, omentum), to herniate outward, forming a hernia sac. The hernia is initially reducible if contents can be pushed back into the abdominal cavity.
If the neck of the sac is narrow, contents can become trapped and unable to be reduced (incarcerated). Incarceration itself does not necessarily compromise blood supply, but if the vascular supply to the trapped tissue is compromised, the bowel or tissue becomes strangulated, leading to ischemia, necrosis, and potential perforation. This is a surgical emergency.
A Richter hernia involves only one antimesenteric wall of the bowel herniating (no obstruction, but strangulation risk remains). A sliding hernia contains a partially extraperitoneal organ (e.g., cecum, bladder) forming part of the sac wall, which is important to recognize surgically to avoid organ injury.
Clinical features
- Bulge or swelling that increases with standing, coughing, or straining (Valsalva) and decreases or disappears when lying down
- Positive cough impulse on palpation
- Vague discomfort, dragging sensation, or pain, often worse with activity
- Reducible hernia: bulge can be manually pushed back into the abdominal cavity
- Incarcerated hernia: bulge is firm, tender, cannot be reduced
- Strangulated hernia: severe pain, erythema or discoloration of overlying skin, fever, tachycardia, signs of bowel obstruction (nausea, vomiting, distension, obstipation), and systemic toxicity
Inguinal hernia exam
Indirect hernias classically appear above and medial to the pubic tubercle, may descend into the scrotum, and are more common in younger patients. Direct hernias bulge through Hesselbach triangle and are more common in older men. Clinical differentiation (via the ring occlusion test) is unreliable and not required for management, since treatment is the same.
Diagnosis
Diagnosis is primarily clinical, based on history and physical examination with the patient both standing and supine, with and without Valsalva maneuver.
- Physical exam: inspection and palpation of the groin, umbilicus, or incision site for a bulge with a cough impulse
- Ultrasound: useful when the diagnosis is unclear clinically, especially in obese patients or to distinguish hernia from other groin masses (e.g., lymphadenopathy, lipoma, hydrocele, varicocele)
- CT abdomen/pelvis: used when strangulation or bowel obstruction is suspected, or to characterize complex/occult hernias
- Laboratory tests (lactate, white blood cell count) are not diagnostic for the hernia itself but help identify strangulation or ischemia when clinical suspicion is high
No imaging is required for a straightforward, reducible hernia with a classic history and exam.
Differential diagnosis
| Condition | Distinguishing feature |
|---|---|
| Hydrocele | Transilluminates, confined to scrotum, no cough impulse |
| Varicocele | "Bag of worms" feel, disappears when supine, more common on left |
| Inguinal lymphadenopathy | Firm, non-reducible nodes, no cough impulse |
| Lipoma | Soft, mobile, non-reducible, no relation to straining |
| Testicular torsion | Acute severe scrotal pain, absent cremasteric reflex, surgical emergency |
| Femoral artery aneurysm | Pulsatile mass |
| Undescended/retractile testis | Absent testis in scrotum, mass in groin |
Management
General principles
Symptomatic or enlarging hernias are generally repaired surgically because of the risk of incarceration and strangulation. Asymptomatic, minimally symptomatic inguinal hernias in men may be managed with watchful waiting, as many guidelines (including those from major surgical societies) note that most will eventually become symptomatic and require repair, but immediate surgery is not mandatory.
Surgical repair
- Mesh-based herniorrhaphy (open or laparoscopic/robotic) is the standard of care for most adult abdominal wall hernias, as it significantly reduces recurrence compared to primary tissue repair
- Laparoscopic approaches (TEP, TAPP) offer faster recovery and less chronic pain in experienced hands, particularly favored for bilateral or recurrent hernias; open repair (e.g., Lichtenstein technique) remains widely used and preferred in certain settings
- Primary (non-mesh) repair may be used in contaminated fields, pediatric hernias, or small umbilical hernias
Emergency management
Incarcerated or strangulated hernias require urgent evaluation:
- Attempt gentle manual reduction only if there are no signs of strangulation or peritonitis
- Emergency surgical exploration and repair if reduction fails or strangulation is suspected, with resection of any non-viable bowel
- Supportive care: IV fluids, bowel rest, broad-spectrum antibiotics if bowel compromise is suspected
Pediatric and special populations
- Pediatric inguinal hernias should be repaired promptly after diagnosis given higher incarceration risk in infants
- Umbilical hernias in children often close spontaneously by age 2-4 years; repair is considered if persistent beyond this age or if large
- Pregnant patients: elective repair generally deferred until after delivery unless incarcerated/strangulated
Complications and prognosis
- Incarceration: irreducible hernia, risk of progression to strangulation
- Strangulation: bowel ischemia, necrosis, perforation, peritonitis, sepsis; a surgical emergency with significant morbidity and mortality if treatment is delayed
- Bowel obstruction: from incarcerated bowel within the hernia sac
- Postoperative complications: recurrence, chronic groin pain (especially with open mesh repair, related to nerve entrapment), surgical site infection, mesh-related complications (rare: mesh migration, erosion)
Overall prognosis after elective repair is excellent, with low recurrence rates in mesh-based repairs. Outcomes after emergency surgery for strangulated hernia are worse, with higher morbidity and mortality tied to delayed presentation and bowel resection.
Hesselbach triangle borders - "IRE": Inferior epigastric vessels (lateral), Rectus abdominis/lateral border of rectus sheath (medial), inguinal ligament (inferior/base) - direct hernias push through this triangle.
Practice questions
1. A 55-year-old man presents with a bulge in his right groin that appears when he stands and disappears when supine. On examination, the bulge is located superior and medial to the pubic tubercle, within Hesselbach triangle, and is reducible. Which of the following best describes this hernia?
2. A 68-year-old woman presents to the emergency department with a 12-hour history of severe pain and a tender, erythematous, non-reducible bulge below the inguinal ligament. She has associated nausea, vomiting, and abdominal distension. Vital signs show tachycardia and low-grade fever. What is the most appropriate next step in management?
3. A 3-year-old boy is noted by his pediatrician to have a soft, non-tender bulge at the umbilicus that protrudes with crying and reduces easily with gentle pressure. The child is otherwise healthy and asymptomatic. What is the most appropriate management?
Frequently asked questions
What causes a hernia?
A hernia is caused by a combination of a structural weakness in the abdominal wall and increased intra-abdominal pressure. Weakness may be congenital (patent processus vaginalis) or acquired through aging, prior surgery, or connective tissue disorders. Pressure increases from chronic cough, constipation, heavy lifting, obesity, or pregnancy push tissue through the weakened area, forming the hernia.
What are the first symptoms of a hernia?
The first symptom is usually a soft bulge or swelling, often in the groin or near the umbilicus, that appears or enlarges with standing, coughing, or straining and disappears when lying down. There may be a dragging or aching discomfort rather than severe pain. Severe, constant pain with a firm, tender, non-reducible bulge suggests incarceration or strangulation and needs urgent evaluation.
How is a hernia diagnosed?
A hernia is diagnosed mainly through physical examination, checking for a bulge with a palpable cough impulse while the patient stands and performs Valsalva. Ultrasound is used when the exam is inconclusive or body habitus limits palpation, and CT is reserved for suspected complications like strangulation or obstruction. Most straightforward hernias do not require imaging.
Is a hernia curable?
Yes, most abdominal wall hernias are effectively cured with surgical repair, typically using mesh to reinforce the defect and minimize recurrence. Hernias do not resolve on their own in adults and tend to enlarge over time, so surgery is the definitive treatment. Pediatric umbilical hernias are an exception, often closing spontaneously in early childhood.
Inguinal hernia vs femoral hernia — what is the difference?
An inguinal hernia occurs above the inguinal ligament through the inguinal canal and is far more common, especially in men, while a femoral hernia occurs below the inguinal ligament through the femoral canal and is more common in women. Femoral hernias have a narrower neck and therefore a higher risk of incarceration and strangulation, making prompt repair more strongly recommended even when asymptomatic.
Key drugs
Related conditions and differentials
Sources and further reading
StatPearls (NCBI Bookshelf)MedlinePlusWHO ICD-10: K41
Educational content for medical students, prepared by the WhiteCoat Pro editorial team with AI assistance; every page is reviewed by a second AI model for factual errors. It is not medical advice and does not replace the product label, local guidelines or a clinician.