Abdominal Wall Pain

Anterior Cutaneous Nerve Entrapment Syndrome (ANES)

General Characteristics

  1. Terminal branches of thoracic intercostal nerves are entrapped in abdominal muscles that causes severe neuropathic pain

Clinical Manifestations

  1. The site of abdominal wall tenderness is < 2cm2
    that is situated within the lateral boundaries of the rectus abdominis muscle
  2. A positive Carnett’s sign in which there is an  exacerbation of pain during palpation with contraction of the abdominal musculature. The patient lies flat and flexes the head against resistance
  3. Rarely there is hyperalgesia and allodynia to mechanical stimuli of the painful area

Neuropathology

  1. Entrapment of the anterior cutaneous branches of intercostal nerves from structures of the abdominal wall that include the parietal peritoneum, subcutaneous tissue, aponeurosis and
    the abdominal muscles

Laboratory Evaluation

  1. Normal laboratory analysis

Neuroimaging

  1. MRI and / or CT to rule out other abdominal pathology

Iliohypogastric Nerve

General Characteristics

  1. The iliohypogastric nerve is mixed and arises from the anterior rami of T12 and L1 nerve roots
  2. It courses across the psoas muscle, behind the kidney, crosses the quadratus lumborum muscle to reach the iliac crest. It pierces the internal oblique and transversus abdominis muscles
    which it innervates
  3. Its lateral cutaneous branch innervates the skin over the outer buttock and hip; its anterior cutaneous branch supplies the anterior abdominal wall above the pubis

Clinical Manifestations

  1. There is little motor deficit
  2. Hypoesthesia or mechanical hyperalgesia in the distribution of the anterior or lateral cutaneous branches of the nerve

Neuropathology

  1. The nerve may be crushed or undergo neuropractic injury from severe pelvic trauma
  2. The lateral branch is often injured during iliac crest bone marrow harvesting
  3. The nerve is most commonly injured in the lumbar plexus, at the posterior or anterior abdominal wall or distally near the inguinal ring
  4. The nerve may be injured during hernia repair

Neuroimaging

  1. Ultrasonography of the nerve

Ilioinguinal Nerve

General Characteristics

  1. The ilioinguinal nerve is mixed and takes origin from the anterior ramus of the first lumbar root. It courses laterally and downwards in parallel with the iliohypogastric nerve to the iliac crest. It supplies the internal oblique and transversus abdominis muscles
  2. After innervating these two muscles it enters the inguinal canal, courses to the superficial inguinal ring from which its sensory fibers emerge
  3. The sensory innervation is to the medial thigh below the inguinal ligament and the skin of the symphysis pubis and external genitalia

Clinical Manifestations

  1. Hyper or hypoesthesia of the skin along the inguinal ligament with radiation to the lower abdomen
  2. Pain may be localized to the medial groin, the labia majora or the scrotum
  3. In approximately 75% of patients there is pain and tenderness with mechanical stimuli applied to the areas where the nerve exits the inguinal canal
  4. Symptoms are exacerbated by hip extension
  5. Patients may walk with the trunk forward flexed
  6. Pain may be elicited by palpation medial to the anterior superior iliac spine

Neuropathology

  1. Neuropractic or direct injury to the nerve occurs in the lumbar plexus, at the posterior or anterior abdominal wall or within the inguinal canal.
  2. The nerve may be injured with herniorrhaphy or appendectomy
  3. The nerve is usually entrapped as it passes through the muscles of the abdominal wall medial to the anterior superior iliac spine
  4. The nerve may be stretched during pregnancy
  5. Trauma to the external oblique muscle and aponeurosis has been described in professional athletes which entraps the nerve in the injured muscle (one form of “sports” hernia)

Laboratory Evaluation

  1. EMG to evaluate denervation in the external oblique muscle

Neuroimaging

  1. Ultrasonography of the nerve

Genitofemoral Nerve (GFN)

General Characteristics

  1. The genitofemoral nerve is primarily sensory
  2. It arises from the first and second lumbar segments within the psoas muscle. It courses through the psoas muscle and divides near the inguinal ligament into the genital branch and femoral branch (lumboinguinal branch)
  3. The external spermatic or genital branch (composed of fibers from L1) enters the deep inguinal ring courses through the inguinal canal and terminates in the cremaster muscle and skin of the scrotum or labia majoris and medial thigh
  4. The lumboinguinal or femoral branch arises primarily from L2, courses behind the femoral artery to innervate the skin of the upper thigh and the femoral triangle

Clinical Manifestations

  1. Pathology of the femoral branch of the nerve causes hypoesthesia over the anterior thigh below the inguinal ligament which distinguishes the nerve from the iliohypogastric or ilioinguinal nerves
  2. Groin pain, paresthesias and burning sensation may be perceived from the lower abdomen to the medial thigh
  3. There is overlapping sensory innervation with the ilioinguinal and ilio hypogastric nerves
  4. Pain can be exacerbated by internal or external rotation of the hip, prolonged walking and mechanical stimuli (if hyperalgesia or allodynia has developed)
  5. Loss of the cremasteric reflex

Neuropathology

  1. The nerve can be injured during inguinal and femoral herniorrhaphy using both open and laparoscopic techniques
  2. The nerve may be injured in the lumbar plexus, within the abdomen or in the femoral or inguinal region

Laboratory Evaluation

  1. Nerve conduction velocity

Neuroimaging

  1. Ultrasonography of the nerve

Postherniorrhaphy Inguinal Pain (CPIP)

General Characteristics
  1. Inguinal hernia repair is one of the most common operations worldwide. Chronic postherniorrhaphy inguinal pain is its most feared complication.
  2. Approximately 800,000 inguinal repairs are performed annually in the USA; the lifetime risk for men is 27% and 3% for women.
  3. The usual definition of chronic postherniorrhaphy inguinal pain (CPIP) is 3-6 months. The estimate of moderate to severe pain following surgery is 10-12%
  4. The possible etiologies of this inguinal pain are:
    a. Hernia recurrence
    b. Tissue inflammation
    c. Meshoma
    d. Inguinal nerve injury or entrapment
  5. The risk factors are:
    a. Female sex
    b. Young age
    c. High pre and postoperative pain levels
    d. CPIP (chronic postsurgical inguinal pain) is independent of technique
    e. Preoperative experimental stimuli (response to pain tests) have been shown to predict 4%  to 54% of the postoperative pain experience
    f. Genetic susceptibilit

Clinical Manifestations

  1. Clinical symptomatology of CPIP has been categorized into:
    a. Neuropathic pain
    b. Somatic pain
    c. Visceral pain
  2. Neuropathic pain:
    a. Spontaneous pain
    b. Hypoesthesia
    c. Hyperesthesia and allodynia to mechanical stimuli
    d. Burning paresthesia
    e. Stabbing, burning, pulling, throbbing, lancinating, sharp and prickling are the most  common descriptors
    f. The most common sites of pain radiation are the scrotum, labium, and upper thigh
    g. Rarely a trigger point can be elicited that produces the pain radiations
    h. The pain is exacerbated by walking, twisting or stretching the torso, stooping or sitting,
    hyperextension of the hip and sexual intercourse
    i. A few male patients describe painful ejaculation
    j. Relieving factors are recumbency with flexion of the hip and thigh
  3. Non-neuropathic pain (inflammatory pain):
    a. Dull ache, that is constant and perceived over the entire groin area
    b. No trigger points and no pain radiation
    c. Descriptors of the pain are: gnawing, tender, pounding or pulling
  4. Nociceptive pain:
    a. Usually localized to the pubic tubercle
  5. Visceral pain:
    a. Generally related to sexual dysfunction or ejaculatory pain (usually burning) which is perceived in the region of the superficial ring of the inguinal canal or the testicular or labial region
    b. Patients that have had their surgery from an anterior approach may have a tender spermatic cord
    c. Abdominal wall laxity from partial denervation of the oblique musculature

Neuropathology

  1. Entrapment or injury of the iliohypogastric, ilioinguinal, and genital femoral nerves are common causes of CPIP. Operative neurectomy of the three nerves is a common mode of surgical therapy. The entrapment is frequently caused by sutures or fixating devices
  2. There is significant anatomical variation of the IHN, IIN and GFN with cross innervation in the retroperitoneum and inguinal canal
  3. Meshoma:
    a. The mesh is implanted in front of or behind the transversalus fascia; in the latter approach this is done through an open or laparoscopic technique
    b. The mesh is implanted without fixation or is fixed by sutures, metallic staples and tacks or various tissue glues
    c. Non or insufficient fixation or inadequate dissection for the prosthesis leads to folding and wrinkling of the mesh that continues until the mesh forms a ball, the meshoma
    d. Meshomas cause neuropathic pain from nerve entrapment, direct contact with mesh or compression of contiguous tissue which may cause both nociceptive pain or a foreign body feeling

Neuroimaging

  1. Ultrasonography is the best initial modality to detect hernia recurrence or meshoma
  2. Cross-sectional computed tomography (CT) and MRI of the abdominal wall are useful to exclude other pathologies and to validate meshoma and recurrent hernia as causative

Differential Diagnosis of Abdominal Referred Pain by Location

Right Upper Quadrant
  1. Cholecystitis:
    a. Radiation to T6 (tip of the scapula)
  2. Cholangitis
  3. Pancreatitis:
    a. Radiation straight through to the back
  4. Hepatitis
  5. Budd-Chiari syndrome
  6. Subdiaphragmatic abscess

Epigastric Referred Pain

  1. Peptic ulcer
  2. Gastritis
  3. GERD-radiations into the chest and pharynx
  4. Pancreatitis
  5. Esophagitis-radiation as well into the chest

Left Upper Quadrant Referred Pain

  1. Splenic infarct and rupture:
    a. Radiation to the ipsilesional side shoulder
  2. Gastritis and gastric ulcer:
    a. Diffuse
  3. Pancreatitis
  4. Subdiaphragmatic abscess

Right Lower Quadrant

  1. Appendicitis
  2. Inguinal hernia
  3. Nephrolithiasis
  4. Inflammatory bowel disease
  5. Mesenteric lymphadenitis
  6. Typhlitis (recurrent appendiceal infection)

Periumbilical Referred Abdominal Pain

  1. Early appendicitis
  2. Gastroenteritis
  3. Bowel obstruction

Left Lower Quadrant Referred Abdominal Pain

  1. Diverticulitis
  2. Inguinal hernia
  3. Nephrolithiasis
  4. Irritable bowel syndrome
  5. Inflammatory bowel disease