This document discusses abdominal wall and hernia repair for fourth year medical students. It covers inguinal herniorrhaphy, which is one of the most commonly performed operations in the United States, with over 965,000 procedures performed annually. Approximately 75% of abdominal wall hernias occur in the groin, with 90% occurring in men. Risk increases with age, peaking after age 40. It also discusses the history and examination for hernias, as well as treatments including different types of hernia repairs.
35. INTRODUCTION Inguinal herniorrhaphy is one of the most commonly
performed operations in the United States.1 Based on estimates made by the
National Center for Health Statistics, in 2010 nearly 515,000 inguinal hernia
operations were performed in hospitals, and an additional 450,000 were
performed in ambulatory surgery centers. Approximately 75% of abdominal
wall hernias occur in the groin. Of inguinal hernia repairs, 90% are performed in
men, and 10% are performed in women. This is thought to be because the
lifetime risk of inguinal hernia is 27% in men and 3% in women. The incidence
of inguinal hernia in men has a bimodal distribution, with peaks before the first
year of age and after age 40. Abramson demonstrated the age-dependence of
inguinal hernias in 1978. Those age 25 to 34 years had a lifetime prevalence
rate of 15%, whereas those age 75 years and over had a rate of 47% .
Approximately 70% of femoral hernia repairs are performed in women;
however, the most common subtype of groin hernia in men and women is still
the indirect inguinal hernia. Inguinal hernias are five times more common than
femoral hernias.
The arcuate line, also known as the semicircular line of Douglas, is a curved line found posterior to the rectus abdominis muscle bilaterally, between the umbilicus and the pubic symphysis. This anatomical finding may not always be present, and its exact position may vary.
Superior to the arcuate line, the external oblique aponeurosis (i.e., a thin layer of connective tissue that covers and supports the muscle) passes anterior to the rectus abdominis muscle. The aponeurosis of the internal oblique splits to surround the rectus abdominis muscle. Additionally, posterior to the rectus abdominis muscle is the aponeurosis of the transversus abdominis muscle, as well as the transversalis fascia. All of the aforementioned aponeuroses wrap around the rectus abdominis muscle, forming the rectus sheath. At the level of and posteriorly to the arcuate line, the aponeuroses of the internal oblique and transversus abdominis pass anteriorly to the rectus abdominis muscle, instead of surrounding the muscle. Therefore, the transversalis fascia is the only structure located posteriorly.
The inguinal ligament (also ligamentum inguinale, arcus inguinalis or Pouparts’s ligament) is a band of connective tissue that extends from the anterior superior iliac spine of the ilium to the pubic tubercle on the pubic bone.
It is formed by the free inferior border of the aponeurosis of the external oblique muscle which attaches to these two points. The inguinal ligament is closely related to a number of structures and forms the superior boundary of the femoral triangle and contributes to the floor of the inguinal canal in the pelvic region.
Rings
The two openings to the inguinal canal are known as rings. There are two rings – deep (internal) and superficial (external):
Deep (internal) ring:
Marks the internal opening of the inguinal canal
Found above the midpoint of the inguinal ligament (lateral to the epigastric vessels).
The ring is created by the transversalis fascia, which invaginates to form a covering of the contents of the inguinal canal.
Superficial (external) ring:
Marks the external end of the inguinal canal
Lies just superior to the pubic tubercle.
It is a triangle shaped opening, formed by the invagination of the external oblique, which forms another covering of the inguinal canal contents.
It contains intercrural fibres, which run perpendicular to the aponeurosis of the external oblique and prevent the ring from widening.
Contents
The contents of the inguinal canal include:
Spermatic cord (biological males only) – contains neurovascular and reproductive structures that supply and drain the testes. See here for more information.
Round ligament (biological females only) – originates from the uterine horn and travels through the inguinal canal to attach at the labia majora.
Ilioinguinal nerve – contributes towards the sensory innervation of the genitalia
Note: only travels through part of the inguinal canal, exiting via the superficial inguinal ring (it does not pass through the deep inguinal ring)
This is the nerve most at risk of damage during an inguinal hernia repair.
Genital branch of the genitofemoral nerve – supplies the cremaster muscle and anterior scrotal skin in males, and the skin of the mons pubis and labia majora in females.
A hernia is the abnormal exit of tissue or an organ, such as the bowel, through the wall of the cavity in which it normally resides
Schwartz 1600
Development of the Inguinal Canal
During development, the tissue that will become gonads (either testes or ovaries) establish in the posterior abdominal wall, and descend through the abdominal cavity. A fibrous cord of tissue called the gubernaculum attaches the inferior portion of the gonad to the future scrotum or labia, and guides them during their descent.
The inguinal canal is the pathway by which the testes (in an individual with an XY karyotype) leave the abdominal cavity and enter the scrotum. In the embryological stage, the canal is flanked by an out-pocketing of the peritoneum (processus vaginalis) and the abdominal musculature.
The processus vaginalis normally degenerates, but a failure to do so can cause an indirect inguinal hernia, a hydrocele, or interfere with the descent of the testes. The gubernaculum (once it has shortened in the process of the descent of the testes) becomes a small scrotal ligament, tethering the testes to the scrotum and limiting their movement.
History:
Workup for inguinal hernia begins with a detailed history. The most common symptom of inguinal hernia is a groin mass that protrudes while standing, coughing, or straining. It is sometimes described as reducible while lying down. Symptoms that are extrainguinal such as a change in bowel habits or urinary symptoms are far less common but should be recognized as having the potential to be ominous. The pain is thought to be due to compression of the nerves by the sac, causing generalized pressure, localized sharp pain, or referred pain. Referred pain may involve the scrotum, testicle, or inner thigh. Important considerations of the patient’s history include the duration and timing of symptoms. Sudden onset symptoms are more concerning. Questions should also be directed to characterize whether the hernia is reducible. Patients will often reduce the hernia by pushing the contents back into the abdomen, thereby providing temporary relief. As the defect size increases and more intra-abdominal contents fill the hernia sac, the hernia may become harder to reduce and incarcerate, prompting urgent surgical intervention. Certain elements of the review of systems such as chronic constipation, cough, or urinary retention should prompt the surgeon to perform a thorough workup to rule out any underlying malignancy.
Examination:
mnPhysical examination is essential to the diagnosis of inguinal hernia. The patient should be examined in a standing position to increase intra-abdominal pressure, with the groin and scrotum fully exposed. Inspection is performed first, with the goal of identifying an abnormal bulge along the groin or within the scrotum. If an obvious bulge is not detected, palpation is performed to confirm the presence of the hernia. Palpation is performed by advancing the index finger through the scrotum towards the external inguinal ring (Fig. 37-11). This allows the inguinal canal to be explored. The patient is then asked to perform a Valsalva maneuver to increase intraabdominal pressure. These maneuvers will reveal an abnormal bulge and allow the clinician to determine whether the hernia is reducible or not. Examination of the contralateral side affords the clinician the opportunity to compare the presence and extent of herniation between sides. This is especially useful in the case of a small hernia. In addition to inguinal hernia, a number of other diagnoses may be considered in the differential of a groin bulge (Table 37-5). While very difficult to ascertain, there are certain physical examination maneuvers that can be performed to help distinguish direct vs. indirect inguinal hernias. The inguinal occlusion test entails the examiner blocking the internal inguinal ring with a finger as the patient is instructed to cough. A controlled impulse suggests an indirect hernia, while persistent herniation suggests a direct hernia. Transmission of the cough impulse to the tip of the finger implies an indirect hernia, while an impulse palpated on the dorsum of the finger implies a direct hernia. When results of physical examination are compared against operative findings, there is a probability somewhat higher than chance (i.e., 50%) of correctly diagnosing the type of hernia.21,22 External groin anatomy is difficult to assess in obese patients, making the physical diagnosis of inguinal hernia challenging. A further challenge to the physical examination is the identification of a femoral hernia. Femoral hernias should be palpable below the inguinal ligament, lateral to the pubic tubercle. In obese patients, a femoral hernia may be missed or misdiagnosed as a hernia of the inguinal canal. In contrast, a prominent inguinal fat pad in a thin patient, otherwise known as a femoral pseudohernia, may prompt an erroneous diagnosis of femoral hernia.
In the case of an ambiguous diagnosis, radiologic investigations may be used as an adjunct to history and physical examination. Imaging in obvious cases is unnecessary. The most common radiologic modalities include ultrasonography (US), computed tomography (CT), and magnetic resonance imaging (MRI). Each technique has certain advantages over physical examination alone; however, each modality is associated with potential limitations. US is the least invasive technique and does not impart any radiation to the patient. Anatomic structures can be more easily identified by the presence of bony landmarks; however, because there are few bones in the inguinal canal, other structures such as the inferior epigastric vessels are used to define groin anatomy. Positive intra-abdominal pressure is used to elicit the herniation of abdominal contents. Movement of these contents through the canal is essential to making the diagnosis with US, and lack of this movement may lead to a false negative. A recent meta-analysis demonstrated that ultrasound detects inguinal hernia with a sensitivity of 86%, specificity of 77%.23 In thin patients, normal movement of the spermatic cord and posterior abdominal wall against the anterior abdominal wall may lead to false-positive diagnoses of hernia.24 CT and MRI provide static images that are able to delineate groin anatomy, to detect groin hernias, and to exclude potentially confounding diagnoses (Fig. 37-12). Meta-analysis determined standard CT detects inguinal hernia with a sensitivity of 80%, specificity of 65%. Although direct herniography has a higher sensitivity and specificity than CT, its invasiveness and limited availability restrict its routine use.23 As CT imaging increases in resolution, its sensitivity in detecting inguinal hernia is expected to expand; however, this has yet to be clinically confirmed by surgical correlation.25 MRI is most commonly utilized in cases where physical examination detects a groin bulge, but where ultrasonography is inconclusive. In a 1999 study of 41 patients with clinical findings of inguinal hernia, laparoscopy revealed that MRI was an effective diagnostic test with a sensitivity of 95%, specificity of 96%.26 The expense of MRI precludes its routine use to diagnose inguinal hernias.
Surgical repair of hernias can be performed open, laparoscopic, or with robotic assistance. Surgical repair is the definitive treatment of inguinal hernias. The most common reason for elective repair is pain. Incarceration and strangulation are the primary indications for urgent repair. Symptomatic hernias should be operated on electively, and minimally symptomatic or asymptomatic hernias should undergo watchful waiting.
Repair of minimally symptomatic inguinal hernia in patients with significant medical comorbidities surgery should be deferred and the patient medically optimized. If despite optimal management of comorbidities, the patient remains high-risk, open repair under local anesthesia can be safely performed.
Although the natural history of untreated inguinal hernias is poorly defined, the rates of incarceration and strangulation are low in the asymptomatic population. As a result, nonoperative management is an appropriate consideration in minimally symptomatic patients
Femoral and symptomatic inguinal hernias carry higher complication risks, and so surgical repair is performed earlier for these patients.
Shouldice Repair The Shouldice repair recapitulates principles of the Bassini repair, and its distribution of tension over several tissue layers results in lower recurrence rates (Fig. 37-16). During dissection of the cord, the genital branch of the genitofemoral nerve is routinely divided, resulting in ipsilateral loss of sensation to the scrotum in men or the mons pubis and labium majus in women. With the posterior inguinal floor exposed, an incision in the transversalis fascia is made between the pubic tubercle and internal ring. Care is taken to avoid injury to preperitoneal structures, which are bluntly dissected to mobilize the upper and lower fascial flaps. At the pubic tubercle, the iliopubic tract is sutured to the lateral edge of the rectus sheath using a synthetic, nonabsorbable, monofilament suture. This continuous suture progresses laterally, approximating the edge of the inferior transversalis flap to the posterior aspect of the superior flap. At the internal inguinal ring, the suture continues back in the medial direction, approximating the edge of the superior transversalis fascia flap to the shelving edge of the inguinal ligament. At the pubic tubercle, this suture is tied to the tail of the original stitch. The next suture begins at the internal inguinal ring, and it continues medially, apposing the aponeuroses of the internal oblique and transversus abdominis to the external oblique aponeurotic fibers. At the pubic tubercle, the suture doubles back through the same structures laterally towards the tightened internal ring.
