What is an inguinal hernia?

Inguinal Hernia: Comprehensive Overview

Definition and Pathophysiology

An inguinal hernia is a protrusion of abdominal contents (typically intestine or omentum) through a defect in the abdominal wall in the groin region, occurring through either the inguinal canal (indirect hernia) or directly through a weakness in the posterior wall (direct hernia). 1

Anatomical Classification

• Indirect hernias: Protrusion through the internal inguinal ring, following the path of the spermatic cord, resulting from incomplete involution of the processus vaginalis 2
• Direct hernias: Protrusion through a weakness in Hesselbach's triangle in the posterior inguinal wall 3
• Femoral hernias: Occur below the inguinal ligament through the femoral canal, with higher strangulation risk 4

Epidemiology and Risk Factors

Incidence Patterns

• Term infants: 3-5% incidence 2, 5
• Premature infants (born <33 weeks): 13% incidence 2, 5
• Gender distribution: Over 90% occur in males, with 60% on the right side 2
• Prevalence of patent processus vaginalis: Up to 80% in term male infants, declining with age 2

Key Risk Factors

• Family history of inguinal hernia 4
• Previous contralateral hernia 4
• Male gender 4
• Advanced age 4
• Abnormal collagen metabolism 4
• Prior prostatectomy 4
• Low body mass index 4
• Previous abdominal or groin surgeries 2

Clinical Presentation

Typical Symptoms

• Groin bulge that increases with crying, coughing, or straining and may disappear when supine 1
• Burning, gurgling, or aching sensation in the groin 1
• Heavy or dragging sensation that worsens toward end of day and after prolonged activity 1
• Pain that can sometimes be severe 1
• In males, the bulge may extend into the scrotum; in females, into the labia 2

Signs of Complications (Incarceration/Strangulation)

• Irreducibility of the hernia 2
• Tenderness and erythema over the hernia 2
• Systemic inflammatory response syndrome (SIRS) indicators 6, 2
• Elevated lactate, CPK, and D-dimer levels are predictive of bowel strangulation 6
• Systemic symptoms including fever, tachycardia 2

Diagnosis

Physical Examination

History and physical examination are sufficient to make the diagnosis in the vast majority of patients. 1

• Palpate for a bulge or impulse while the patient coughs or strains 1
• Examine both groins bilaterally, as contralateral patent processus vaginalis occurs in 64% of infants younger than 2 months 2
• In males, palpate the testis to ensure it is present in the scrotum and not involved in the hernia 2
• Assess for femoral hernias, which have higher strangulation risk and are often missed 2

Imaging Studies

• Ultrasonography: Useful when diagnosis is uncertain, for recurrent hernias, suspected hydrocele, surgical complications, or in athletes without palpable findings 1
• CT scanning: May be useful in emergency settings to assess for bowel obstruction or strangulation 2
• Dynamic MRI or herniography: Rarely needed, reserved for complex diagnostic scenarios 4

Management Approach

Timing of Intervention

Patients with suspected intestinal strangulation should undergo emergency hernia repair immediately. 6, 2

• Delayed treatment (>24 hours) is associated with significantly higher mortality rates 2, 5
• Symptomatic periods >8 hours, presence of comorbid disease, high ASA scores, and strangulation significantly affect morbidity 2, 5

Surgical Indications

All symptomatic inguinal hernias should be treated surgically. 4

For Adults

• Asymptomatic or minimally symptomatic male patients may be managed with "watchful waiting" since their risk of hernia-related emergencies is low, though the majority will eventually require surgery 4
• Mesh repair is recommended as first choice, either by open or laparoscopic approach 4

For Infants and Children

All inguinal hernias in infants require surgical repair to prevent bowel incarceration and gonadal infarction/atrophy. 2

• Urgent surgical referral for repair within 1-2 weeks of diagnosis 2
• Preterm infants should undergo repair soon after diagnosis despite higher surgical complication rates, as they face higher incarceration risk 2

Surgical Techniques

Open Repair

• Lichtenstein technique is well-evaluated and recommended 4
• Shouldice technique is the first choice for tissue repair if mesh is not used 4
• Local anesthesia can be used effectively in emergency inguinal hernia repair without bowel gangrene, with less cardiac and respiratory complications, shorter ICU and hospital stays, lower cost, and faster recovery compared to general anesthesia 6
• Perioperative field blocks and/or subfascial/subcutaneous infiltrations are recommended in all open repairs 4

Laparoscopic Repair

Laparoscopic approaches (TEP or TAPP) have faster recovery times, lower chronic pain risk, and are cost-effective when expertise and resources are available. 4

• Lower wound infection rates compared to open repair in emergency settings (P<0.018) without higher recurrence rates 6
• Laparoscopic repair is feasible for incarcerated hernias in the absence of strangulation 6
• Hernioscopy (mixed laparoscopic-open technique) is effective for evaluating bowel viability, preventing unnecessary laparotomy and decreasing morbidity in high-risk patients 6
• During TAPP, inspect the contralateral side after patient consent; this is not suggested during unilateral TEP repair 4

Mesh Considerations

For clean surgical fields (CDC wound class I - intestinal incarceration without strangulation or bowel resection), prosthetic repair with synthetic mesh is recommended. 6

• Mesh repair has lower recurrence rates compared to tissue repair without increased wound infection 6
• Mesh fixation in TEP is unnecessary in almost all cases 4
• In both TEP and TAPP, fix mesh in M3 hernias (large medial) to reduce recurrence risk 4
• Low-weight mesh may have slight short-term benefits but no better long-term outcomes; selection on weight alone is not recommended 4
• Avoid plug repair techniques due to higher erosion incidence 4

Special Populations

Women

Women with groin hernias should undergo laparoscopic repair when expertise is available to decrease chronic pain risk and avoid missing a femoral hernia 4

Pregnant Women

Watchful waiting is suggested in pregnant women as groin swelling most often consists of self-limited round ligament varicosities 4

Femoral Hernias

Timely mesh repair by laparoscopic approach is suggested for femoral hernias when expertise is available 4

Patients with Cirrhosis and Ascites

• Patients who are candidates for liver transplantation in the near future should defer hernia repair until during or after transplantation 6
• For patients with low MELD scores, elective herniorrhaphy may be offered after careful risk-benefit assessment 6
• Clinically apparent ascites should be controlled before elective herniorrhaphy, with laparoscopic approaches preferred 6

Antimicrobial Prophylaxis

Antibiotic prophylaxis in average-risk patients in low-risk environments is not recommended in open surgery and never recommended in laparoscopic repair. 4

• CDC wound class I (no ischemia, no bowel resection): Short-term prophylaxis recommended 6
• CDC wound classes II and III (strangulation and/or bowel resection): 48-hour antimicrobial prophylaxis recommended 6
• CDC wound class IV (peritonitis): Antimicrobial therapy recommended 6

Postoperative Management

Activity Restrictions

Patients are recommended to resume normal activities without restrictions as soon as they feel comfortable. 4

• Avoid activities that increase intra-abdominal pressure to prevent incarceration and strangulation 2, 5

Monitoring for Complications

Postoperative Apnea Risk

• Preterm infants, particularly those under 46 weeks corrected gestational age, require 12-hour postoperative monitoring due to elevated apnea risk 2

Day Surgery

Day surgery is recommended for the majority of groin hernia repairs provided aftercare is organized 4

Complications

Chronic Postoperative Inguinal Pain (CPIP)

The overall incidence of clinically significant chronic pain is 10-12%, decreasing over time, with debilitating pain affecting daily activities ranging from 0.5-6%. 4

Definition

• Bothersome moderate pain impacting daily activities lasting at least 3 months postoperatively and decreasing over time 4

Risk Factors

• Young age 4
• Female gender 4
• High preoperative pain 4
• Early high postoperative pain 4
• Recurrent hernia 4
• Open repair 4

Prevention and Management

• Focus on nerve recognition in open surgery with prophylactic pragmatic nerve resection in selected cases (planned resection not suggested) 4
• Multi-disciplinary team management is suggested 4
• Combination of pharmacological and interventional measures, followed by (triple) neurectomy and mesh removal in selected cases if unsuccessful 4

Recurrence

Recurrence rates are low with proper technique, but anatomical changes after suture repair (reduced surface area of Hesselbach's and Hessert's triangles) may contribute to recurrence. 7

Management of Recurrent Hernias

• After anterior repair recurrence: Posterior repair is recommended 4
• After posterior repair recurrence: Anterior repair is recommended 4
• After failed anterior and posterior approaches: Management by specialist hernia surgeon is recommended 4

Other Complications

• Infection is a potential complication 2
• Testicular complications in males including gonadal infarction/atrophy 2
• Laparoscopic-specific complications: Pneumomediastinum, pneumothorax, gas extravasation, trocar injuries, intraabdominal adhesions, bowel obstruction 3

Common Pitfalls to Avoid

• Failing to examine both sides for hernias, missing the 64% rate of contralateral patent processus vaginalis in infants under 2 months 2
• Missing femoral hernias, which have higher strangulation risk 2
• Not assessing for complications (incarceration/strangulation) that require urgent intervention 2
• Delaying surgery in infants due to concerns about surgical risk, when incarceration risk is actually higher 2
• Using general anesthesia in elderly patients when local anesthesia may have fewer complications 6
• Performing bilateral exploration during unilateral TEP repair 4