Formation and causes
An inguinal hernia is protrusion of abdominal or pelvic contents through a dilated internal inguinal ring alongside the spermatic cord, with potential extension through the inguinal canal into the scrotum NICE CKS.
Indirect hernias usually result from a persistent processus vaginalis, whereas direct and indirect hernias are classified by the relationship of the hernia sac to the inferior epigastric artery NICE CKS.
Recognised risk factors are a positive family history, previous contralateral hernia, increasing age, and connective-tissue disorders such as Marfan syndrome or Ehlers–Danlos syndrome involving abnormal collagen metabolism NICE CKS.
Raised intra-abdominal pressure factors such as constipation, straining, chronic cough, heavy lifting, exercise, pregnancy, childbirth, ascites, and pelvic mass are described as contributors to haemorrhoid development, but are not listed as inguinal-hernia risk factors in the supplied inguinal-hernia guideline excerpt NICE CKS,NICE CKS.
Effects and clinical consequences
A hernia may produce a groin or scrotal swelling; extension into the scrotum is almost always indirect NICE CKS.
Reducible symptomatic hernias warrant routine surgical referral, while minimally symptomatic hernias may not require referral or surgery according to clinical judgement, and asymptomatic hernias can be managed conservatively but are likely to require surgery in future NICE CKS.
Potential acute complications include incarceration, in which the mass cannot be reduced and there is usually severe pain over a groin or scrotal swelling NICE CKS.
Strangulation occurs when blood supply to herniated tissue is compromised, causing ischaemia and an acutely painful, firm, tender, irreducible mass NICE CKS.
If small bowel within the hernia becomes obstructed, patients may develop vomiting, abdominal pain, and abdominal swelling NICE CKS.
After surgical repair, recurrence rates of up to 15% have been reported, and chronic pain lasting longer than 3 months has been reported in 10–12% of cases NICE CKS.
Clinically evident bilateral hernias, or a contralateral hernia during the lifetime, occur in up to 50% of people who develop an inguinal hernia NICE CKS.
The cited lifetime risk of inguinal-hernia repair is 27% in men NICE CKS.