Inguinal Canal and Hernias

The inguinal region, or the groin, is located in the RLQ and LLQ of the anterior abdominal wall Anterior abdominal wall The anterior abdominal wall is anatomically delineated as a hexagonal area defined superiorly by the xiphoid process, laterally by the midaxillary lines, and inferiorly by the pubic symphysis. Anterior Abdominal Wall, bordered by the thigh Thigh The thigh is the region of the lower limb found between the hip and the knee joint. There is a single bone in the thigh called the femur, which is surrounded by large muscles grouped into 3 fascial compartments. Thigh inferiorly, the pubis medially, and the iliac crest superolaterally. The inguinal canal is a tubular structure that runs in a straight line from the anterior superior iliac spine to the pubic tubercle. The canal contains the spermatic cord in men and the round ligament in women. This region is clinically relevant, as it is the site for the most common type of hernias, such as indirect and direct inguinal hernias. Patients with hernias will present with a unilateral bulge in the groin that may be associated with pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain. In symptomatic or high-risk cases, hernias can be repaired surgically.

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Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

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Overview

  • The inguinal region, or the groin, is located in the RLQ and LLQ of the anterior abdominal wall Anterior abdominal wall The anterior abdominal wall is anatomically delineated as a hexagonal area defined superiorly by the xiphoid process, laterally by the midaxillary lines, and inferiorly by the pubic symphysis. Anterior Abdominal Wall.
  • Boundaries:
    • Thigh inferiorly
    • Pubic tubercle medially
    • Anterior superior iliac spine laterally
  • The inguinal canal runs in a straight line from the anterior superior iliac spine to the pubic tubercle.
  • Contents of inguinal canal:
    • Men:
      • Spermatic cord (with genitofemoral nerve)
      • Ilioinguinal nerve
    • Women:
      • Round ligament
      • Genitofemoral nerve
      • Ilioinguinal nerve
  • Hesselbach triangle:
    • A triangle of the abdominal wall
    • Located medial to the epigastric vessels
    • Site of direct inguinal hernias

Embryologic Development

Formation of the inguinal canal

  • Independent of testicular descent, in the 12th week of gestation, the anterior abdominal wall Anterior abdominal wall The anterior abdominal wall is anatomically delineated as a hexagonal area defined superiorly by the xiphoid process, laterally by the midaxillary lines, and inferiorly by the pubic symphysis. Anterior Abdominal Wall musculature and fascia form an evagination on each side of the midline known as the processus vaginalis.
  • The processus vaginalis, in combination with the muscle and fascia of the anterior abdominal wall Anterior abdominal wall The anterior abdominal wall is anatomically delineated as a hexagonal area defined superiorly by the xiphoid process, laterally by the midaxillary lines, and inferiorly by the pubic symphysis. Anterior Abdominal Wall, forms the inguinal canal.
  • In women, the ovum descends into the pelvis Pelvis The pelvis consists of the bony pelvic girdle, the muscular and ligamentous pelvic floor, and the pelvic cavity, which contains viscera, vessels, and multiple nerves and muscles. The pelvic girdle, composed of 2 "hip" bones and the sacrum, is a ring-like bony structure of the axial skeleton that links the vertebral column with the lower extremities. Pelvis, and the round ligament of the uterus travels through the inguinal canal to the labia majora.

Male inguinal canal development

  • The testes originally reside in the posterior aspect of the abdominal cavity.
  • Between 28 and 33 weeks’ gestation, the testes pass through the inguinal region and into the scrotum.
    • The gubernaculum, a band of mesenchymal tissue that terminates in the inguinal region on the caudal pole of the testes, assists the testes in their migration.
    • Failed testicular descent results in cryptorchidism Cryptorchidism Cryptorchidism is one of the most common congenital anomalies in young boys. Typically, this asymptomatic condition presents during a routine well-child examination where 1 or both testicles are not palpable in the scrotum. Cryptorchidism.
  • Descent of the testes creates a weakness in the abdominal wall in the region of the inguinal canal, making men particularly susceptible to hernia formation.
  • The connection between the processus vaginalis and the peritoneum Peritoneum The peritoneum is a serous membrane lining the abdominopelvic cavity. This lining is formed by connective tissue and originates from the mesoderm. The membrane lines both the abdominal walls (as parietal peritoneum) and all of the visceral organs (as visceral peritoneum). Peritoneum and Retroperitoneum will obliterate at birth, but a serous sac will remain around the testes, known as the tunica vaginalis testis.
  • Abdominal wall contributions:
    • Transversalis fascia forms the internal spermatic fascia.
    • Internal oblique muscle forms the cremasteric fascia and muscle.
    • External oblique muscle forms the external spermatic fascia.
Pathway of testicular descent

Pathway of testicular descent from the posterior abdominal wall into the scrotum: The testicles Testicles The testicles, also known as the testes or the male gonads, are a pair of egg-shaped glands suspended within the scrotum. The testicles have multiple layers: an outer tunica vaginalis, an intermediate tunica albuginea, and an innermost tunica vasculosa. The testicles are composed of testicular lobules and seminiferous tubules. Testicles pass through the inguinal canal.

Image by Lecturio.

Inguinal Canal Anatomy

Anterior abdominal wall

  • The anterior abdominal wall Anterior abdominal wall The anterior abdominal wall is anatomically delineated as a hexagonal area defined superiorly by the xiphoid process, laterally by the midaxillary lines, and inferiorly by the pubic symphysis. Anterior Abdominal Wall is composed of several muscles:
    • Rectus abdominis
    • External oblique
    • Internal oblique
    • Transversus abdominis
  • The inner transversalis fascia continues into the inguinal canal, forming the internal spermatic fascia.

Course of the inguinal canal

  • Approximately 4 cm long from anterior superior iliac spine to pubic tubercle (superolaterally to inferomedially)
  • Deep inguinal ring: an evagination of the transversalis fascia (surrounding the spermatic cord as the internal spermatic fascia)
  • Superficial inguinal ring: a fissure in the aponeurosis of the external oblique muscle
The layers of the anterior abdominal wall

The layers of the anterior abdominal wall Anterior abdominal wall The anterior abdominal wall is anatomically delineated as a hexagonal area defined superiorly by the xiphoid process, laterally by the midaxillary lines, and inferiorly by the pubic symphysis. Anterior Abdominal Wall, depicting the course of the inguinal canal and the composition of the deep and superficial inguinal rings

Image by Lecturio. License: CC BY-NC-SA 4.0

Boundaries of the inguinal canal

The boundaries of the inguinal canal vary throughout its course.

  • At the level of the deep ring:
    • Anterior wall: 
      • Internal oblique muscle
      • External oblique muscle
    • Posterior wall: transversalis fascia
    • Roof: transversalis fascia
    • Floor: inguinal ligament
  • At the middle of the inguinal canal:
    • Anterior well: external oblique aponeurosis
    • Posterior wall: transversalis fascia
    • Roof: arching fibers of the internal oblique muscle and transversus abdominis
    • Floor: inguinal ligament
  • At the level of the superficial ring:
    • Anterior wall: external oblique aponeurosis
    • Posterior wall: conjoint tendon
    • Roof: medial crus of external oblique muscle
    • Floor: lacunar ligament
Boundaries and contents of the male inguinal canal

Boundaries and contents of the male inguinal canal:
Note that the ilioinguinal nerve runs along the inguinal canal externally from the spermatic cord.

Image by Lecturio. License: CC BY-NC-SA 4.0

Borders of the Hesselbach triangle

  • Refers to a triangle of the anterior abdominal wall Anterior abdominal wall The anterior abdominal wall is anatomically delineated as a hexagonal area defined superiorly by the xiphoid process, laterally by the midaxillary lines, and inferiorly by the pubic symphysis. Anterior Abdominal Wall
  • Boundaries:
    • Medial: lateral margin of the rectus abdominis (linea semilunaris)
    • Superolateral: inferior epigastric vessels
    • Inferior: inguinal and pectineal ligament
  • Direct hernias occur within the triangle, and indirect hernias occur lateral to the triangle.

Femoral canal

  • Located posterolaterally to the inguinal canal
  • Contents:
    • Femoral vein
    • Femoral artery
    • Femoral nerve
    • Iliacus muscle
    • Pectineus muscle
    • Femoral ring: site of femoral hernias
Boundaries of the femoral ring and canal

From medial to lateral, the femoral canal contains the femoral vein, artery, and nerve.

Image by Lecturio.

Epidemiology and Etiology of Inguinal Hernias

Epidemiology

  • Most common type of hernia (> 75% of cases)
  • Indirect inguinal hernias > direct inguinal hernias
  • Usually presents in the extremes of life (< 1 and > 50 years of age)
  • Lifetime risk of approximately 25% for men and < 5% for women

Risk factors

  • History of hernia or previous hernia repair
  • Male sex
  • Older age
  • Chronic obstructive pulmonary disease Chronic obstructive pulmonary disease Chronic obstructive pulmonary disease (COPD) is a lung disease characterized by progressive, largely irreversible airflow obstruction. The condition usually presents in middle-aged or elderly persons with a history of cigarette smoking. Signs and symptoms include prolonged expiration, wheezing, diminished breath sounds, progressive dyspnea, and chronic cough. Chronic Obstructive Pulmonary Disease (COPD) ( COPD COPD Chronic obstructive pulmonary disease (COPD) is a lung disease characterized by progressive, largely irreversible airflow obstruction. The condition usually presents in middle-aged or elderly persons with a history of cigarette smoking. Signs and symptoms include prolonged expiration, wheezing, diminished breath sounds, progressive dyspnea, and chronic cough. Chronic Obstructive Pulmonary Disease (COPD))
  • Chronic constipation Constipation Constipation is common and may be due to a variety of causes. Constipation is generally defined as bowel movement frequency < 3 times per week. Patients who are constipated often strain to pass hard stools. The condition is classified as primary (also known as idiopathic or functional constipation) or secondary, and as acute or chronic. Constipation
  • Weight lifting 
  • Obesity Obesity Obesity is a condition associated with excess body weight, specifically with the deposition of excessive adipose tissue. Obesity is considered a global epidemic. Major influences come from the western diet and sedentary lifestyles, but the exact mechanisms likely include a mixture of genetic and environmental factors. Obesity
  • Smoking

Etiology

  • Congenital: 
    • Due to abnormal development
    • Failed closure of the processus vaginalis
  • Acquired:
    • Develop later in life due to progressive weakness of previously normal tissues
    • Conditions with increased intraabdominal pressure, such as strenuous physical activity, coughing, or obesity
    • Sometimes iatrogenic due to injury or abdominal surgery
  • All direct hernias are acquired, while indirect ones may be congenital or acquired.

Classification and Clinical Presentation

Classification

  • Indirect hernias: 
    • Lateral to the inferior epigastric blood vessels and the Hesselbach triangle 
    • Contents pass through the deep inguinal ring, traverse the entire trajectory of the inguinal canal, and exit the canal through the superficial inguinal ring.
    • Contents are encased by the coverings of the spermatic cord.
  • Direct hernias:
    • Medial to the inferior epigastric blood vessels and within the Hesselbach triangle
    • Contents protrude directly through the posterior wall of the inguinal canal and through the superficial inguinal ring, encased only by the external spermatic fascia.
  • Pantaloon hernia: inguinal hernia with both direct and indirect components
  • Femoral hernia Femoral hernia A femoral hernia is an uncommon type of groin hernia in which intra-abdominal contents herniate under the inguinal ligament and through the femoral ring into the femoral canal. More common in adults than in children, femoral hernias usually present with swelling that protrudes into the femoral triangle. Femoral Region and Hernias: hernia through the femoral canal with a bulge below the inguinal ligament
  • Amyand hernia: The appendix is found within the hernia sac.
Anatomy of the inguinal region and hernia

View of the left inguinal canal: Indirect inguinal hernias arise lateral to the epigastric vessels, while direct inguinal hernias arise medial to the epigastric vessels.

Image by Lecturio.

Clinical presentation

  • Mild inguinal pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain or discomfort
  • Visible bulge in the groin area, which increases upon standing or during physical activities that increase intraabdominal pressure (coughing, sneezing, weight lifting) and reduces upon lying down.
  • May be associated with a communicating hydrocele
  • Erythema may be noted over the hernia if there is strangulation and tissue death.

Complications

  • Incarceration:
    • Inability of the contents of the hernia to return to their original cavity
    • Presents with severe pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain and a non-reducible bulge
    • If the intestines are incarcerated, symptoms of intestinal obstruction develop.
  • Strangulation:
    • Contents of the hernia must first become incarcerated.
    • Blood supply to the incarcerated organs is compromised, which causes ischemia and resultant tissue death.

Diagnosis and Management

Diagnosis

  • Medical history and physical exam
  • Palpation of the inguinal canal:
    • With the patient standing, palpate from the scrotal skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin toward the superficial inguinal ring.
    • Ask the patient to cough (Valsalva maneuver).
    • Bulging can be felt at the fingertip.
  • Imaging:
    • Used for confirmation in uncertain cases and occasionally surgical planning
    • Ultrasound :
      • Best initial imaging study in patients without physical evidence of a hernia 
      • The diagnostic finding is an increased diameter of the inguinal canal (normally < 13 mm at the deep inguinal ring).
    • CT scans: particularly useful to distinguish between different subtypes of inguinal hernias
    • MRI:
      • Best imaging modality to differentiate between inguinal and femoral hernias with a sensitivity and specificity greater than 95%
      • Due to the cost and limited availability of MRIs, CT scans are still more frequently used.

Management

  • Surgical hernia repair:
    • Complicated hernias
    • Uncomplicated hernias with moderate symptoms 
    • Selectively for uncomplicated hernias with mild symptomatology or high risk of incarceration
    • Specifics of surgical repair techniques can be found in abdominal hernias.
  • Surgical techniques:
    • Reinforcing the posterior wall of the inguinal canal with synthetic mesh
    • Reduction in the diameters of the inguinal rings

References

  1. Sadler, T. W. (2012). Chapter 16: Urogenital system. In Langman’s Medical Embryology. 12th ed., pp. 232–259. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins.
  2. Malangoni, M. A., & Rosen, M. J. (2012). Hernias. In Mattox, K. L., et al. (Eds.), Sabiston Textbook of Surgery: The Biological Basis of Modern Surgical Practice, 19th ed., pp. 1114‒1140. Elsevier.
  3. Brooks, D. V., & Hawn, M. (2019). Classification, clinical features, and diagnosis of inguinal and femoral hernias in adults. In Chen, W. (Ed.). UpToDate. Retrieved June 19, 2021, from https://www.uptodate.com/contents/classification-clinical-features-and-diagnosis-of-inguinal-and-femoral-hernias-in-adults

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