Strangulation of a hernia is a true surgical emergency with a narrow time window — ischaemia of the trapped segment of bowel begins within 4-6 hours of arterial occlusion at the hernia neck. The progression: venous occlusion first (oedema, swelling of hernia increases) → arterial occlusion → ischaemia → necrosis → perforation → faecal peritonitis. The clinical distinction between obstruction and strangulation: in obstruction, the pain is colicky (comes and goes) and the hernia may still be reducible; in strangulation, the pain is constant, severe, and unremitting, the hernia is tense and tender, the overlying skin becomes erythematous (cellulitis of overlying skin indicates necrotic bowel within), and systemic features (tachycardia, fever, hypotension) indicate sepsis from transmural bowel necrosis. The femoral hernia demands special mention — it carries the highest strangulation rate of all hernias (approximately 22% at first presentation, compared to approximately 3% for inguinal hernias) because the femoral ring is narrow, rigid, and bound by the inguinal ligament, Cooper's ligament, and the femoral vein. Any femoral hernia should be referred for urgent surgical assessment even when asymptomatic.

The distinction between inguinal and femoral hernia is clinically important but can be challenging — the anatomical landmark is the pubic tubercle: inguinal hernias pass above and medial to the pubic tubercle; femoral hernias pass below and lateral to the pubic tubercle (because the femoral canal lies medial to the femoral vein, below the inguinal ligament). In practice, palpating the pubic tubercle is achieved by placing the examining finger at the medial attachment of the inguinal ligament (at the symphysis pubis) and tracing it laterally — the pubic tubercle is approximately 1 cm lateral to the midline. The clinical significance: a swelling above and medial to the pubic tubercle is an inguinal hernia; a swelling below and lateral is femoral. This distinction is not merely academic — femoral hernias require urgent referral (high strangulation risk), whereas asymptomatic or minimally symptomatic inguinal hernias in elderly or frail patients may be managed conservatively with watchful waiting and a truss.

Ultrasound is the first-line imaging investigation for groin hernias in primary care — it is safe, widely available, and has a sensitivity of approximately 85-90% and specificity of approximately 82-88% for inguinal hernias when performed dynamically (patient straining). USS also differentiates hernias from: inguinal lymphadenopathy (soft tissue masses without bowel content or impulse), hydrocele (anechoic fluid, transilluminates, no cough impulse), lipoma of the cord (common mimic), spermatocele, femoral artery aneurysm (pulsatile, no cough impulse), and psoas abscess (fluctuant, extending from retroperitoneum). The limitation of USS: operator-dependent; misses some occult hernias; poor sensitivity for femoral hernias in obese patients. CT provides definitive anatomy for complex or recurrent hernias and for preoperative planning. MRI is the most sensitive investigation for occult inguinal hernias and is the investigation of choice when USS is negative but clinical suspicion remains high.

The testicular torsion mimicry of inguinal hernia is a crucial diagnostic trap in primary care — testicular torsion can present with scrotal swelling and pain that is occasionally referred to the inguinal region, mimicking an incarcerated inguinoscrotal hernia. The distinguishing features of torsion: acute onset severe pain (often waking from sleep in adolescents), nausea and vomiting, the testis rides high in the scrotum (the twisting shortens the spermatic cord), the cremasteric reflex is absent on the affected side, and the pain is not relieved by elevation or support. The testicular torsion time window: viability falls from approximately 100% at <6 hours to approximately 10% at 24 hours. Any adolescent or young adult with acute scrotal pain must be treated as torsion until proved otherwise — examination under general anaesthesia for surgical exploration is the standard, not watchful waiting with USS (USS misses torsion in approximately 15% of cases and causes dangerous time delays).

The watchful waiting versus immediate repair debate for asymptomatic inguinal hernia has been resolved by two landmark RCTs — the Fitzgibbons trial (JAMA 2006) and the O'Dwyer trial (UK, 2006) both randomised men with minimally symptomatic inguinal hernias to watchful waiting vs immediate repair. Key findings: at 2 years, approximately 72% of watchful waiting patients remained pain-free without acute hernia complications; acute hernia emergencies (strangulation/obstruction) occurred in approximately 1.8 per 1000 patient-years in the watchful waiting group (very low but not zero); most patients in watchful waiting eventually crossed over to surgery due to increasing symptoms; quality of life at 2 years was equivalent between groups for asymptomatic patients. NICE NG134 reflects this evidence: watchful waiting is appropriate for asymptomatic or minimally symptomatic inguinal hernias in men who are informed of the risks and have access to emergency services. However, femoral hernias should always be repaired urgently due to the disproportionately high strangulation risk.

The chronic pain after inguinal hernia repair is the most significant long-term complication of inguinal hernia surgery — it affects approximately 10-15% of patients with mild chronic pain and approximately 1-3% with severe chronic pain (pain that impairs daily function or quality of life significantly). The mechanism: injury to the ilioinguinal nerve, iliohypogastric nerve, or genital branch of the genitofemoral nerve during dissection or from mesh entrapment. Risk factors: open Lichtenstein repair (higher than laparoscopic), younger patients (higher pain sensitivity), pre-operative pain (most significant predictor), and anxiety/depression. Treatment: simple analgesia → neuropathic pain agents (amitriptyline, pregabalin, gabapentin) → targeted nerve block (ilioinguinal nerve block with local anaesthetic + corticosteroid) → neurectomy (surgical division of the entrapped nerve at specialist hernia centre). GPs should be aware that patients presenting post-hernia repair with persistent groin pain may have neuropathic mesh pain — this is a genuine complication, not psychosomatic, and warrants specialist hernia clinic review.

The 'can't reduce a strangulated hernia' principle is the most critical safety instruction for any GP managing an acutely symptomatic hernia — the theoretical concern about reducing a strangulated hernia is the Maydl's hernia variant (a double-loop hernia where the segment of bowel that has strangulated is actually inside the abdominal cavity, not in the hernia sac). If such a hernia is reduced manually into the abdomen, the necrotic bowel segment disappears inside the peritoneal cavity, giving false reassurance that the hernia is 'fine' — while the patient develops faecal peritonitis from the perforated bowel inside. Any hernia with: constant pain (not colicky), overlying skin erythema, fever, toxicity, or the hernia feels hard and tense (rather than soft and compressible) must be treated as strangulated and referred to 999 immediately without any attempt at manual reduction.

The distinction between paediatric and adult hernia management is fundamental — in adults, watchful waiting for asymptomatic inguinal hernias is a NICE-recommended evidence-based option. In children (particularly infants under 1 year and premature infants), the incarceration risk is substantially higher (approximately 12-17%) because the hernia neck is proportionally tighter relative to the contents, and infants cannot describe pain or recognise early incarceration symptoms themselves. The BAPS (British Association of Paediatric Surgeons) guideline recommends surgical repair of all paediatric inguinal hernias promptly after diagnosis (typically within 2-4 weeks for infants under 1 year; less urgently for older children). Premature infants: repair before discharge from the neonatal unit (NICU) if clinically stable, as the incarceration risk is highest in the early weeks after birth. GPs diagnosing a groin swelling in a child under 1 year should refer to paediatric surgery within 24-48 hours — not routine outpatient waiting.

The MHRA mesh safety alert (2018) specifically applies to pelvic floor mesh used vaginally for prolapse and stress urinary incontinence — it does NOT apply to polypropylene inguinal hernia mesh. GPs should be clear when counselling patients about hernia surgery: the widely reported media stories about 'dangerous mesh' relate to pelvic mesh implanted trans-vaginally, which was associated with mesh erosion into the vagina, bladder, and bowel. Inguinal hernia mesh is placed in an extraperitoneal plane far from any visceral or mucosal surface, and its safety and efficacy profile is well-established over 30 years of use. The recurrence rate with mesh (1-3%) compared to non-mesh repair (10-15%) represents a very significant benefit, and the risk of serious mesh complications is low. Patients with concerns about mesh should have this distinction explained clearly and should be offered the opportunity to speak with the surgeon before consenting to repair.