Abdominal wall

• Abdominal wall


  Complex structure composed primarily of muscle, bone and fascia

  
• Abdominal wall


  • Major function is to protect the enclosed organs of the gastrointestinal and urogenital tracts
  • Secondary role is mobility, being able to flex, extend, rotate and vary its capacity
• Flexibility of the abdominal wall requires elasticity and stretch which compromise abdominal wall strength
• Diaphragm


  Forms the roof of the abdomen, separating the thoracic cavity above with negative pressure from the abdomen below with positive pressure
• Weakness of the diaphragm


  Can lead to much of the bowel being drawn into the chest down this pressure gradient
• Pelvis


  Forms the floor of the abdominal cavity, but a muscular central portion, the perineum, may also weaken and allow rectum, bladder and gynaecological organs to bulge downwards, a condition called prolapse
• Hernia


  The bulging of part of the contents of the abdominal cavity through a weakness in the abdominal wall
• A normal abdominal wall has sufficient strength to resist high abdominal pressure and prevent herniation of content
• Factors attributed to hernia formation


  • Constipation
  • Prostatic symptoms
  • Excessive coughing in respiratory disease
  • Obesity

  
• Hernia is no more common in Olympic weight lifters than the general population, suggesting that high pressure is not a major factor in causing a hernia
• Hernia


  A 'collagen disease' and due to an inherited imbalance in the types of collagen
• Hernia development


  More common in pregnancy due to hormonally induced laxity of pelvic ligaments

  
• Hernia development


  More common in the elderly due to degenerative weakness of muscles and fibrous tissue

  
• Hernia


  Patients are usually aware of a lump on the abdominal wall under the skin, often painless but may complain of an aching or heavy feeling

  
• Sharp, intermittent pains suggest pinching of tissue, and severe pain should alert the surgeon to a high risk of strangulation

  
• Hernia


  It is important to know if this is a primary hernia or a recurrence after previous surgery, as recurrent hernia is more difficult to treat and may require a different surgical approach

  
• Factors to assess in a hernia patient


  • Cardiac and respiratory systems to assess anaesthetic risk
  • Prostatic symptoms in a male with a groin hernia indicating high risk of postoperative urinary retention
  • Intake of anticoagulants such as warfarin

  
• Operative approaches to hernia

  1. Reduction of the hernia content into the abdominal cavity with removal of any non-viable tissue and bowel repair if necessary

  2. Excision and closure of a peritoneal sac if present or replacing it deep to the muscles

  3. Reapproximation of the walls of the neck of the hernia if possible

  4. Permanent reinforcement of the abdominal wall defect with sutures or mesh

  
• Mesh


  Prosthetic material, either a net or a flat sheet, used to strengthen a hernia repair

  
• Ways mesh can be used in hernia repair


  • To bridge a defect: the mesh is simply fixed over the defect as a tension-free patch
  • To plug a defect: a plug of mesh is pushed into the defect
  • To augment a repair: the defect is closed with sutures and the mesh added for reinforcement
• Classification of mesh types


  • Synthetic mesh
  • Biological mesh
  • Absorbable meshes
  • Tissue-separating meshes

  
• Inguinal hernia


  The most common hernia in men and women, but much more common in men

  
• Inguinal canal


  As the testis descends from the abdominal cavity to the scrotum in the male, it first passes through a defect called the deep inguinal ring in the transversalis fascia, just deep to the abdominal muscles
• Inguinal canal


  • The inferior epigastric vessels lie just medial to the deep inguinal ring passing from the iliac vessels to the rectus abdominus muscle
  • Muscle fibres of the transversus muscle and the internal oblique muscle arch over the deep inguinal ring from lateral to medial before descending to become attached to the pubic tubercle, forming the conjoint tendon
  • Below this arch there is no muscle but only transversalis fascia and external oblique aponeurosis resulting in weakness

  
• Sliding hernia


  An acquired hernia due to weakening of the abdominal wall at the deep inguinal ring lateral to the inferior epigastric vessels, where retroperitoneal fatty tissue is pushed downwards along the inguinal canal

  
• Occasionally, both lateral and medial hernias are present in the same patient (pantaloon hernia)

  
• Diagnosis of an inguinal hernia

  Usually these hernias are reducible presenting as intermittent swellings, lying above and lateral to the pubic tubercle with an associated cough impulse

  
• Diagnosing an inguinal hernia


  1. With the patient lying down, the patient is asked to reduce the hernia if it has not spontaneously reduced

  2. If the patient cannot, the surgeon gently attempts to reduce the hernia

  3. Once reduced, the surgeon identifies the bony landmarks of the anterior superior iliac spine and pubic tubercle to landmark the deep inguinal ring at the mid-inguinal point

  4. Gentle pressure is applied at this point and the patient asked to cough - if the hernia is controlled with pressure on the deep inguinal ring then it is likely to be indirect/lateral, and if the hernia appears medial to this point then it is direct/medial

  
• Investigations for inguinal hernia


  • Ultrasound scanning
  • CT scan
  • MRI scan
  • Herniogram (injection of contrast into the peritoneal cavity followed by screening)

  
• Femoral hernia


  The iliac artery and vein pass below the inguinal ligament to become the femoral vessels in the leg, with the vein lying medially and the artery just lateral to the artery with the femoral nerve lateral to the artery, enclosed in a fibrous sheath. Just medial to the vein is a small space containing fat and some lymphatic tissue (node of Cloquet), which is exploited by a femoral hernia.

  
• Femoral hernia


  • The walls of a femoral hernia are the femoral vein laterally, the inguinal ligament anteriorly, the pelvic bone covered by the ileopectineal ligament (Astley Cooper's) posteriorly and the lacunar ligament (Gimbernat's) medially, which is a strong curved ligament with a sharp unyielding edge which impedes reduction of a femoral hernia

  
• Female pelvis


  Has a different shape to the male, increasing the size of the femoral canal and the risk of femoral hernia
• Femoral hernia


  More commonly seen in low-weight, elderly females due to the increased femoral defect in old age
• Investigations for femoral hernia


  • Ultrasound
  • CT scan
  • Plain x-ray to show small bowel obstruction in emergency cases

  
• Surgical approaches for femoral hernia


  1. Low approach (Lockwood)

  2. Inguinal approach (Lotheissen)

  3. High approach (McEvedy)

  4. Laparoscopic approach

  
• Epigastric hernia


  Arises through the midline raphe (linea alba) anywhere between the xiphoid process and the umbilicus, usually midway. When close to the umbilicus they are called supraumbilical hernias.

  
• Epigastric hernias begin with a transverse split in the midline raphe, in contrast to umbilical hernias where the defect is elliptical

  
• Epigastric hernia


  Commonly contain only extraperitoneal fat which gradually enlarges, spreading in the subcutaneous plane to resemble the shape of a mushroom. When very large they may contain a peritoneal sac but rarely any bowel.
• Epigastric hernia patients


  Often fit, healthy males between 25 and 40 years of age. These hernias can be very painful even when the swelling is the size of a pea due to the fatty contents becoming nipped sufficiently to produce partial strangulation.
• Treatment of epigastric hernia


  Very small epigastric hernias have been known to disappear spontaneously, probably due to infarction of the fat. Small to moderate-sized hernias without a peritoneal sac are not inherently dangerous and surgery should only be offered if the hernia is sufficiently symptomatic.