Clinical Cases - Abdominal Wall and Inguinal Region

A 28-year-old woman in her 36th week of pregnancy arrived in the emergency room following an automobile accident. Immediately following the accident she went into labor. The accident had broken her pelvis such that the emergency room physician deemed a vaginal delivery would be hazardous. An obstetrician was called, and she agreed with the ER physician's initial assessment. A Cesarian section was performed, resulting in the delivery of a healthy baby girl. During the operation, the obstetrician used a Pfannenstiel incision to open the abdomen. This incision involves making a transverse, slightly convex cut large enough to deliver a child at approximately the pubic hairline.

Questions to consider:

1. What abdominal wall layers must be incised at the pubic hairline (near the midline) in order to access the abdominal cavity?

   The Pfannenstiel incision is made below the arcuate line, so the layers incised are as follows: skin, superficial fascia (fatty and membranous), deep fascia, anterior rectus sheath, rectus abdominis muscle, transversalis fascia, extraperitoneal connective tissue, and peritoneum.

2. Why is the incision made in a convex manner instead of straight across?

   The segmental nerves of the anterior abdominal wall follow a superior to inferior course as they progress medially, so by making an incision that approximately parallels the course of the nerves, the surgeon can minimize the number of nerves that are damaged, thus reducing post-operative muscle paralysis and skin paresthesia. In addition, a convex incision parallels the lines of cleavage in the skin of the inferior abdominal wall, resulting in less scarring. A truly horizontal linear incision may cut more than one segmental nerve, depending on the size and location of the incision.

3. What vascular structures might be cut during a Pfannenstiel incision?

   The vascular structures that may be at risk include the inferior epigastric artery and vein, as well as their branches (especially the pubic artery and vein), and the superficial epigastric vessels.

4. Where in the abdomen could a surgeon make a large vertical incision with minimal detrimental effect?

   Vertical abdominal incisions may be made at the midline, through the linea alba, as well as within about 2.5 cm on either side of the midline (paramedian). If a paramedian incision is chosen, the rectus abdominis muscle can be retracted laterally after incision of the anterior rectus sheath. This exposes the posterior rectus sheath and prevents damage to the rectus abdominis muscle and its innervation.

A twenty-five year-old female medical student presents to the emergency room with a complaint of "colicky" periumbilical pain which has intensified over the last 6-8 hours and now has started to migrate to the right lower quadrant. The patient reports some initial nausea, and as the pain has increased she has had increasing emesis and anorexia. Physical exam demonstrates the patient has no distension, auscultation reveals hyperactive bowel sounds, and on palpation the patient demonstrates abdominal guarding and rebound tenderness, and the muscles of the anterior wall in the right lower quadrant are rigid. In addition, the patient has a low-grade fever, and laboratory tests reveal a rising white blood cell count. The attending determines that the patient has acute appendicitis and prepares to take the student to the O.R. for an appendectomy. The surgeon asks you the following questions regarding the surgery.

Questions to consider:

1. What signs and symptoms revealed to the physician that the patient had an acute abdominal problem - potentially appendicitis?
   

   Abdominal pain (periumbilical shifting to the right lower quadrant) followed by anorexia, nausea, and vomiting.

2. How would you distinguish between gastroenteritis and appendicitis?
   

   Gastroenteritis usually causes vomiting before pain and is associated with diarrhea. The patient will also present with a less acute history of abdominal discomfort.

3. What is McBurney's point?
   

   It is the point within the right lower quadrant which can be defined as: one-third the distance from the anterior iliac spine to the umbilicus on a line connecting the two.

4. What is McBurney's sign?
   

   Tenderness at McBurney's point in patients with appendicitis.

5. What types of incisions can be made in the abdominal wall?
   

   Surgeons choose each of the following based on their ability to provide access to the desired organ:
   
   Median or midline: Cut through the linea alba, superior or inferior to the umbilicus. Benefit: minimal blood loss, avoids major nerves, and easy access for exploration.
   
   Paramedian incisions: Cut to the right or left of the midline. Benefit: Avoid nerves, frees the rectus abdominal muscle which decreases tension to the muscle. Gives access to the peritoneal cavity.
   
   Gridiron (muscle splitting)/McBurney incisions: Incision of the external oblique aponeurosis in the direction of its fibers. The internal oblique and transversus abdominis are then incised and split in the direction of their fibers which are then retracted. Benefit: Provides good access with almost no muscle damage and it avoids damage to local nerves.
   
   Pfannenstiel (suprapubic incision): This transverse, slightly convex cut transects the linea alba and anterior layer of the rectus sheath at the pubic hairline. Separate the underlying rectus muscles via the tendons (to allow better reattachment) and identify the surrounding nerves. Benefits: Use for most gynecologic surgeries.
   
   Transverse incision: Cuts through the anterior rectus sheath and the rectus abdominis. Benefits: Causes the least amount of nerve damage, the muscular segments can be rejoined, they are incredibly useful for dissection above the level of the umbilicus.

6. Which of these incisions would be the most ideal for an appendectomy?
   

   Transverse incisions have become increasingly more popular replacing the traditional McBurney's incision. Transverse incisions are less likely to cause nerve injury.

7. When placing an incision in the abdominal wall, what nerves have to be identified? What would be a consequence of damage to the nerves?
   

   The inferior thoracic spinal nerves (T11 and T12), the iliohypogastric nerve and the ilioinguinal nerve innervate abdominal muscles and skin inferior to the umbilicus. The iliohypogastric nerve perforates the posterior part of the transversus muscle; it further divides between the transversus muscle and the internal oblique via cutaneous branches both anteriorly and laterally. In addition these branches provide muscular branches to both the transversus abdominis and internal oblique muscles. Therefore, damage to these nerves can lead to muscle weakness with a potential for herniation and pain/altered sensation due to both these muscular and cutaneous branches.

8. Suppose that the surgeon, in the process of the appendectomy, is unable to locate the appendix through the small incision he made in the right lower quadrant, so he decides to extend his incision several inches superiorly toward the rib cage. What is likely to result from such a procedure?
   

   A vertical incision at approximately the right mid-clavicular line, as would occur if McBurney's incision was extended superiorly, would cut several segmental nerves, resulting in loss of sensation and paralysis of the muscles on the right side, which would in turn cause bulging of the abdominal wall and might necessitate the use of a support belt.

9. Why were the muscles of the anterior abdominal wall rigid?
   

   The ruptured appendix caused peritonitis. Inflammation of the parietal peritoneum causes pain and reflex spasm of the abdominal wall over that area--the peritoneum, abdominal muscles, and overlying skin are all supplied by the same segmental nerves (T11, T12, L1). Spasm apparently occurs to immobilize that region of the abdomen in order to minimize spread of the infection.

10. What nerve is at risk when an incision is made at McBurney's point? What would be the long-term effects of damage to this nerve?
    

    Ilioinguinal and iliohypogastric nerves. Damage to the nerve could cause partial paralysis of the internal oblique and transversus abdominis muscles resulting in laxity of the conjoint tendon and possibly inguinal hernia. Sensation in the anterior scrotal and lateral part of the penis might also be affected.

11. If the appendix is not immediately visible, what features of the cecum could the surgeon use to locate it?
    

    The teniae coli muscles can be traced along the cecum to locate the base of the appendix.

12. Fortunately for the patient, she was treated before her infection became life-threatening; however, if she had waited to seek treatment or if the physicians had not acted quickly on their suspicions, her infection may have continued to spread in the peritoneal cavity and the blood stream. Which organ is particularly at risk for secondary infection in appendicitis and why?
    

    The liver. The vast majority of blood from the GI tract drains into the portal vein and then filters through the liver before entering the inferior vena cava and passing into the general circulation. As a result, the liver is particularly susceptible to secondary infection in appendicitis.

References:

Advanced Surgical Recall
Surgery Scientific Principles and Practices (Greenfield's) pp. 1246-1261.
Moore's Clinical Anatomy pp. 175-191.
Woodburne & Burkel, p. 421-31

S.T., a 35-year-old man, was carrying furniture out to a moving van in preparation for his family's move to a new home. When S.T. strained to pick up a particularly heavy coffee table, he suddenly felt a sharp pain in his right groin. Later, he noticed that a painful bulge had developed in his groin which disappeared when he laid on his back. He did not like going to the doctor, so he ignored the condition. After several months, the pain and the bulge in his groin increased and he finally consented to see a physician. On examination, the physician observed a swelling which began about midway between the anterior superior iliac spine and the midline, progressed medially for about 4 cm, and then turned toward the scrotum . Taking the history and physical findings into account, the physician made a diagnosis of indirect inguinal hernia and scheduled S.T. for surgery . The hernia was successfully repaired, and S.T. was released from the hospital a few days later.

Questions to consider:

1. What abdominal wall layers must be incised with a small midline incision in order to access the abdominal cavity?

   A midline incision would pass through skin, superficial fascia (outer fatty and inner membranous layers), linea alba, transversalis fascia, extraperitoneal connective tissue, median umbilical ligament, and parietal peritoneum.

2. What defines this hernia as an indirect inguinal hernia rather than a direct inguinal hernia? List the key features of each.

   This hernia is an indirect inguinal hernia because it traverses the inguinal canal. Indirect inguinal hernial sacs enter the inguinal canal at the deep inguinal ring lateral to the inferior epigastric vessels. Depending on the severity, the hernial sac may or may not extend through the superficial inguinal ring and into the scrotum or labium majus. Indirect inguinal hernias are more common in males than in females, and may be congenital or the result of an injury, as in the case above. Direct inguinal hernias bulge through the weak fascia of the abdominal wall directly behind the superficial inguinal ring and medial to the inferior epigastric vessels. Direct inguinal hernias are common in elderly men with weak abdominal muscles. Direct inguinal hernias rarely enter the scrotum.

3. What caused the bulge? What body layers would surround it as it proceeded into the scrotum and what abdominal layers are they derived from?

   The bulge was most likely caused by a loop of small intestine that traversed the inguinal canal. The body layers surrounding the intestinal bulge in the scrotum are as follows: skin, dartos muscle, membranous layer of the superficial fascia, external spermatic fascia (from the external oblique aponeurosis), the cremasteric fascia (from the internal oblique aponeurosis), and the internal spermatic fascia (from the transversalis fascia).

4. Why would it be necessary to repair a hernia like the one described above as quickly as possible?

   An indirect inguinal hernia in which the bowel becomes entrapped can rapidly lead to an intestinal obstruction and to strangulation of the loop of bowel projecting into the inguinal canal. If not treated immediately, gangrene of the intestine may set in within 12 hours.

5. How is the inguinal canal formed, and which structures are associated with the inguinal canal in the male? in the female?

   The inguinal canal forms as the gubernaculum draws the testis down into the scrotum during fetal development in the male, or during the analogous development in the female (animation). The deep inguinal ring persists as a defect in the transversalis fascia formed as the gonadal structures descended and the superficial inguinal ring is formed by the lateral one-half of the pubic crest and the lateral and medial crura of the external abdominal oblique aponeurosis. The spermatic cord passes through the inguinal canal in the male and the round ligament of the uterus traverses the canal in the female. The ilioinguinal nerve also passes through the inguinal canal in both sexes.

6. What other abdominal or pelvic regions, aside from the inguinal canal, are susceptible to herniation ?

   Umbilical hernia--Herniation of abdominal contents through a weakness in the abdominal wall behind the umbilicus. This is common in infants.
   
   Femoral hernia--Abdominal contents pass deep to the inguinal ligament into the femoral triangle of the thigh. These herniae should not be confused with inguinal herniae because they present below and lateral to the pubic tubercle, whereas inguinal herniae are found above and medial to the pubic tubercle.
   
   Obturator herniae--These herniae pass into the medial thigh via the obturator foramen in the pelvis.
   
   Lumbar herniae--These emerge through a muscular weakness in the region of the lumbar triangle, which has the following borders: Posterior margin of the external abdominal oblique (anterior border of the triangle), anterior margin of the latissimus dorsi (posterior border of the triangle), iliac crest (inferior border of the triangle), and the internal abdominal oblique and the transversus abdominis muscles (floor of the triangle).
   
   Incisional herniae--These may occur anywhere a weakness in the abdominal wall occurs as a result of an incisional wound, surgical or otherwise.
   
   

   What is the definition of an inguinal hernia? What is the male to female ratio of incidence of direct inguinal hernias?
   

   An abdominal viscus that pushes through a congenital or acquired defect in the lower abdominal wall. The male:female ratio is 9:1.

   What are common causes of direct inguinal hernias?
   

   Increased intraabdominal pressure caused by straining, heavy lifting, heavy exercise, obesity, chronic cough.

   What are the boundaries of Hesselbach's (inguinal) triangle?
   

   Laterally: Deep (inferior) epigastric artery
   Medially: Lateral rectus abdominis muscle border
   Inferiorly: Inguinal ligament

   Do you know your eponyms? What are the following structures? (NOTE: FYI only - we will not exam on these)
   

1. Poupart's ligament - Inguinal ligament
   
2. Cooper's ligament - Pectineal ligament
   
3. Gimbernat's ligament - Lacunar ligament
   
4. Colles' ligament - Reflected inguinal ligament
   
5. Henle's ligament - Falx inguinalis
   
6. Hesselbach's ligament - Interfoveolar ligament (thickened transversalis fascia anterior to the epigastric vessels).
   

References:

Woodburne & Burkel, p.431-435