Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
groin hernias: mechanical anatomy and ultrasound evaluation BY FRANK RYAN, MIR, DMU, MMS, AMS Frank Ryan continues with a second article following on from ‘Embryology and Anatomy of the Inguinal Canal’ published in soundeffects, issue 2, 2003. The University of South Australia ASA Student Award was presented to Frank for this work towards his Masters in Medical Sonography. Hernia is defined by Anderson [1998, p.755] as a ‘protrusion of an organ through an abnormal opening in the muscle wall of the cavity that surrounds it’. The emphasis of this review will be the variable anatomy, mechanics and distribution of groin hernias with an explanation of the subsequent ultrasound techniques. The main hernia types within the inguinal and femoral canal regions which are assessable sonographically are: a. Inguinal , both direct and indirect; b. Femoral; Figure 1. Common sites of inguinal and groin hernias. (Adapted from Agur, 1991, p. 84). c. Sports, a form of direct inguinal hernia (although not a true hernia) and sometimes referred to as Gilmore’s groin; d. Spigelian; e. Obturator; and f. Iatrogenic/Incisional Figure 2. A posterior view of the anterior abdominal wall. (Adapted from Pick, 1977, p. 1048). Of these the inguinal, femoral, Spigelian and incisional hernias are routinely assessed whereas the sports and obturator hernia evaluation by ultrasound techniques are “studies in progress”. Figure 1, demonstrates diagrammatically the potential sites for groin hernias and their relationship with the bony and ligamentous anatomy of the region. The more common hernia sites, the inguinal and femoral, are closely related, as shown in figure 1, and their related anatomical structures, namely the inguinal canal and the saphenous opening in the superficial fascial layers determine the course of the herniating material. 24 issue 3, 2003 Inguinal Hernias Inguinal hernias are those exiting the abdomen through the abdominal wall at the inguinal region. There are two main types, classified by the point of exit from the abdomen: • Indirect - alternatively known as oblique, external or congenital inguinal hernia. soundeffects groin hernias: mechanical anatomy and ultrasound evaluation • Direct - alternatively known as an internal inguinal hernia. Of particular interest when reviewing inguinal hernias are the fossae formed by the urachal, hypogastric and epigastric folds; the internal (or supravesical), the middle and the lateral (external) inguinal fossae, the lateral fossa being lateral to the epigastric vessels with the internal/deep inguinal ring at its most medial aspect. The folds and fossae are well demonstrated in figure 2. The deep inguinal ring is clearly visible lying lateral to the epigastric vessels with the vas deferens passing medial to the femoral vessels, over the inguinal (Poupart’s ligament) and the epigastric vessels. Figure 3. A view of the inner anterior abdominal wall in the region of Hesselbach’s triangle. (Adapted from Warwick, 1973, p.672). Indirect Inguinal Hernia The indirect inguinal hernia, commonly known as an oblique, external, (Pick, 1977, p.1049) or congenital inguinal hernia (Moore, 1992, p.147) involves the passage of bowel or fatty material through the inguinal canal. The material enters at the deep ring pushing a pouch of peritoneum before it and passes through the superficial ring. The degree of herniation varies and an indirect hernia may be either complete, that is passing completely through the canal, or incomplete, being retained within the canal where it is referred to as a bubonocele (Pick, 1977, p. 1051). An indirect inguinal hernia occurs where the stalk of the processus vaginalis, which normally obliterates in both sexes, remains as a potential passageway, hence the term congenital. Generally the hernia does not appear until adulthood and may not occur at all unless circumstances are right, hence if the processus is present the potential for a hernia is there also. An indirect hernia may also be acquired, projecting through this area of potential weakness in the abdominal wall when it is overstressed (Moore, 1992, p. 147). Under normal circumstances the processus vaginalis closes at birth, or soon after. This closure is thought to progress from two points, namely the internal abdominal ring and the top of the epididymis. The portion below the epididymis remains, enveloping the testis as the tunica vaginalis (Pick, 1977, p.1051). A similar situation may occur in females where the gubernaculum passes through the inguinal canal and terminates in the labia majora. Persistence of the processus vaginalis appears as the canal of Nuck (Moore, 1992, p.147). A defect in soundeffects Figure 4. Hesselbach’s triangle as viewed from the front. The limits of the triangle are clearly shown. (Adapted from Warwick, 1973, p. 525). closure may occur at any point and this determines the type of indirect hernia that may form. The mechanics of the indirect or oblique hernia and the tissue planes involved is varied and, generally the differences not appreciated by ultrasound examination. Of note is the point of passage through the abdominal wall, that is, through the deep ring. Direct Inguinal Hernia A direct inguinal hernia is a protrusion of bowel or omentum (or viscera) through a weakness in the lower abdominal wall medial to the epigastric vessels in an area defined as the inguinal or Hesselbach’s triangle. This triangle is formed by the lower lateral margin of the rectus muscle, the medial half of the inguinal ligament and conjoint tendon and the epigastric vessels. Hesselbach’s triangle is clearly outlined in figure 3 - the anterior abdominal wall as seen from behind. The arching transversus abdominis is seen lying lateral to the deep inguinal opening where it blends with the internal oblique to form the inguinal ligament. Figure 4, below, demonstrates the same area from the anterior aspect and gives an appreciation of the limited size of the area involved. The triangle lies posterolateral to the superficial inguinal ring and includes the area of the canal wall that is formed only by the transversalis fascia, hence it is a weak area in the anterior abdominal wall (Moore, 1992, p.148). Direct inguinal hernias are always acquired (Warwick, 1973, p. 1298) and differ from the indirect type in that they do not pass through the inguinal canal but medial to its external (superficial) opening. There are two types, the appearances depending on issue 3, 2003 25 groin hernias: mechanical anatomy and ultrasound evaluation the point of exit through the abdominal wall. opening (Pick, 1977, p. 1062). From figure 2, above, it can be seen that the obliterated hypogastric vessels form a cord which separates Hesselbach’s triangle into two fossae, the medial (or supravesical) and the middle inguinal fossae (Pick, 1977, p.1052). A third fossa, the lateral (or external) inguinal fossa lies lateral to the epigastric vessels. A portion of the lumen of the gut may protrude into the femoral canal and become trapped and strangulated. In this instance the bowel is not obstructed but the entrapped portion may become gangrenous. This type of hernia is known as a Richter’s hernia (Bailley, 1948, p.476). The first type of direct inguinal hernia is one where the herniating material passes through the abdominal wall in the area of the middle inguinal fossa, lateral to the conjoint tendon and medial to the epigastric vessels. It pushes both peritoneum and transversalis fascia before it and enters the inguinal canal, exiting at the superficial. It differs from an indirect hernia in that it does not enter the deep ring and is invested by all layers of the cord except the internal spermatic fascia ring (Warwick, 1973, p.1298). Sonographically this hernia appears very similar to an indirect inguinal hernia and must be distinguished from this. The relationship to the epigastric vessels and the lack of activity lateral to them will provide the clue. In the second form of direct inguinal hernia, the most frequent herniation (Warwick, 1977, p.1298) is through the conjoint tendon itself. Here the contents push a sac of peritoneum before them as they exit the abdomen. Alternatively the conjoint tendon may bulge forming a sac to accommodate the herniation (Pick, 1977, p. 1053). This form of direct hernia does not enter the inguinal canal or the spermatic cord, hence the layers of tissue covering it are distinct to the other forms of inguinal hernia. Femoral Hernia A femoral hernia occurs when the abdominal viscera is forced under pressure into the femoral canal. The herniating material is invested with a layer of peritoneum which forms the hernial sac (Pick, 1977, p. 1061). The extent of a femoral hernia may be quite dramatic. The passage of the hernia is downwards, through the femoral ring to the saphenous opening, forward through this opening to the boundaries formed by the fascia lata and then upwards into the loose areolar tissue of the groin anterior to the inguinal ligament (Pick, 1977, p.1061). Femoral hernias may be classified as complete or incomplete. An incomplete hernia extends to the level of the saphenous opening but not beyond and a complete hernia extends beyond the bounds of the saphenous 26 issue 3, 2003 Table 1 demonstrates the relative incidence of the three main groin hernia types in men, women and children. Table 1. Relative Incidence of Groin Hernias (Adapted from Friedland,2002, internet search) Direct Indirect Femoral Men 40% 50% 10% Women Rare 70% 30% Children Rare 100% Rare Sportsman’s Hernia The syndrome where chronic groin pain persists, particularly in athletes, has been described by Gilmore, and subsequently labelled “Gilmore’s Groin” (Brukner, 2002, p. 392; Brannigan, 2000, p.329) or simply “Sportsman’s/Sports hernia” (Kemp, 1998, p. 2). The term hernia is a misnomer as the condition rarely exists with a true hernia present (Brannigan, 2000, p.329). Kemp [1998, p.1] describes the surgical features of the condition as: the rectus. They are rare (Bailley, 1948, p.482) and from my own experience in ultrasound usually present not as a hernia but as a divarication of the linea semilunaris with the abdominal contents projecting forward on straining. True herniations do occur and are often better demonstrated by CT scanning where the overall perspective is better addressed. Fatty protrusion may occur under stress near the neurovascular bundle containing the inferior epigastric vessels and the branches of the intercostal nerves (Warwick, 1973, p. 1049) causing pain. Obturator Hernia Obturator hernias occur through the obturator canal which lies in a plane similar to the femoral canal but deep to it (figures 1 and 3). The obturator canal courses deep to the pubic ramus whereas the femoral canal lie anterior to the ramus. An obturator hernia may be appreciated sonographically by increasing the field of view when scanning the femoral canal. Movement deep to the femoral canal may indicate an obturator herniation. Iatrogenic/Incisional Hernias • A torn external oblique aponeurosis causing dilatation of the superficial inguinal ring; • • A torn conjoint tendon; and As the name suggests, these hernias occur at the site of previous surgery, which could include appendicectomy or caesarean section. The intervention may leave an area of potential weakness in the abdominal wall, which may lead to a hernia or divarication. Synonyms for this condition include abdominal or ventral hernias (Anderson, 1998, pp.3 and 1702). Dehiscence between the conjoint tendon and the inguinal ligament. Ultrasound Examination The pain is localised to an area adjacent and lateral to the pubic tubercle in the area of the conjoint tendon and may be confused with osteitis pubis. Scanning of this region in a longitudinal plane across the short axis of the spermatic cord often shows a straightening of the posterior canal wall (compared to the normally curved, concave arrangement) and a reduction in the diameter of the spermatic cord (Orchard, 1998, p.134). As stated above, the condition is not true hernia and static images do not demonstrate the condition well. It is best assessed dynamically (Orchard, 1998, p. 137). Spigelian Hernia This is a hernia through the linea semilunaris (linea Spigelii), the aponeurosis between the muscles of the lateral abdominal wall and Patient Preparation • • Dietary preparation is not required. • • Informed consent should be obtained. • Appropriate cover should be provided to preserve modesty and dignity. • A comfortable examination room and warm gel are recommended. The procedure technique and the degree of the patients’ participation should be explained. The patient should undress to the degree required to provide adequate access to the groin, lower abdomen and upper thigh. Imaging Technique Imaging of the groin encompasses soundeffects groin hernias: mechanical anatomy and ultrasound evaluation examination of both sides as bilateral hernias are common (Bailley, 1948, p.465; Bax, 2002, [internet search]) and occur in up to 30% of cases. Examination should include the following areas: • • Conjoint tendon area and pubic tubercle. • • • • Superficial inguinal ring. Femoral canal - include a deeper field of view to assess the obturator canal. Deep inguinal ring. Lower linea alba and rectus muscles. Lower linea semilunaris. All areas should be examined in two planes, both transverse/oblique and longitudinal both at rest and with the patient using some technique to increase intraabdominal pressure. This may include: • • Method Valsalva technique. Blowing into the back of the hand, blowing out the cheeks. • Raising the head and/or feet from the examination couch. • Coughing. Here the violence of the action may preclude satisfactory viewing of the areas. In a normal study each area is imaged in the transverse/oblique plane only, however an abnormal study should include both transverse images and the longitudinal or oblique planes which best demonstrate the abnormality. A routine examination of the inguinal/groin region encompasses: • • • • • • • Figure 5A (left) and 5B (above). The Femoral Canal Conjoint tendon area, including straining. Femoral canal - at rest. Femoral canal - straining. Superficial ring - at rest. Superficial ring - straining. Deep ring - at rest. Deep ring - straining. Further images of each area are taken as determined by the condition at hand The transverse/oblique plane parallels the inguinal ligament, which runs obliquely from the ASIS to pubic tubercle, and the inguinal canal giving a longitudinal image of the canal. Scanning in the longitudinal plane using the epigastric vessels as a reference point will give a cross sectional view of the cord at a slightly oblique angle. Angulation of the transducer to best visualise in two planes is necessary and will vary from patient to patient. soundeffects Conjoint tendon area The transducer should be placed at the lateral aspect of the pubic tubercle and angled upwards and obliquely towards the ASIS. The inguinal ligament will appear as an echogenic band. The posterior wall of the canal and conjoint tendon will lie below the ligament. Scan at rest and with the patient straining in both long and short axis planes along the ligament. Note any excessive movement or herniation. A herniation or bulging of the wall will be toward the transducer. Femoral canal Scan transversely at the level of the pubic tubercle with the transducer aligned vertically. The femoral vessels and canal will lie with the pubic ramus arcing medially. Scan both at rest and with straining and observe any abnormal movement within the canal medial to the dilating femoral vein. Scan longitudinally just medial to the femoral vein at rest and straining, as above. Adjust the depth of the field of view to assess for a possible obturator hernia. This may appear as movement deep to the femoral vessels. Superficial ring Scan the femoral vessels transversely and find the level of the epigastric vessels. The inguinal canal lies anterior and medial to these vessels. To obtain a view in the long axis of the canal, angle cranially and align the transducer with the inguinal ligament. The canal and spermatic cord may be seen behind the ligament and may measure up to 1cm in diameter. Assess both at rest and straining and look for excessive dilatation of the canal and movement of tissues through it. Be aware of a dilated fat or bowel filled canal which exceeds 1cm at rest. Herniation may appear as a bulging of the canal wall medially or a lateral to medial movement arising from the medial aspect of the epigastric vessels Deep ring As with the superficial ring locate the epigastric vessels and align the transducer as above. The deep ring lies lateral to these vessels. Again scan with the patient at rest and straining and look for movement of tissues lateral to medial crossing the vessels. A herniation in the region will appear to originate deep to the transducer and course towards the superficial ring, possibly entering the scrotum or labia majora. Rectus and Symphysis Pubis Scan the distal rectus muscles and symphysis area in two planes. Inflammatory processes or haematoma may appear as a hypoechoic focus or organising clot. Linea Alba and Semilunaris Scan transversely along the line of the linea alba and linea semilunaris with the patient both at rest and straining. Assess for herniation through or between the layers of the aponeurosis or divarication of the muscle junction. Figures 5A and B show the femoral canal at rest and with the patient straining. In B the femoral vein is clearly seen dilated to the right, or medial to the femoral artery. A femoral hernia will appear in the canal medial to the vein. The pubic ramus and pectineus muscle lie deep to the vessels. issue 3, 2003 27 groin hernias: mechanical anatomy and ultrasound evaluation Medical, Nursing and Allied Health Dictionary. 5th edition. St.Louis:Mosby 3. Bailley, Hamilton and Love, R.J. McNeill, 7th Ed, (1948). “A Short Practice of Surgery”. H.K. Lewis & Co:London 4. Bax, Tim, Sheppard, Brett C. and Crass, Richard A., (1999). “Surgical Options in the Management of Groin Hernias”. Viewed October 2002, <http:// www.aafp.org/afp/990101ap/143.html> 5. Brannigan, A.E., Kerin, M.J. and McEntee G.P. (200). “Gilmore’s Groin Repair In Athletes”. Journal of Orthopaedic & Sports Physical Therapy. Vol. 30, No 6. Figure 6A (left). The Superficial Inguinal Ring. Figure 6B (above). The Deep Inguinal Ring. Figures 6A and B clearly show the landmarks of the superficial and deep rings. The femoral artery and vein as well as the epigastric vessels are well seen. In A the long arrow points to the superficial ring. A direct hernia may appear to move from left to right mimicking an indirect hernia passing through the canal. Generally a direct hernia will be seen to move towards the transducer, passing through the transversalis fascia. Figure 6B shows the vessels indicating the site of the deep ring. An indirect or congenital hernia will arise deep to the transducer and move across and in front of the femoral vessels. The epigastric vessels indicate the site of the deep ring. It is important that both sides are examined concurrently and the information provided used to determine the type of hernia present. Be aware that a direct hernia originating in the middle inguinal fossa may enter the inguinal canal and simulate an indirect hernia and it is important to distinguish between the two. A complete examination of the area should include the lower rectus muscles, linea alba and linea semilunaris. They should be examined both at rest and when straining. It is also important to assess scrotal involvement with a direct or indirect hernia in males. Hopefully this article will be of some assistance to Sonographers who are struggling with this area as I have in the past. Conclusion It is important in an ultrasound examination for hernia of the groin and inguinal area, to understand the anatomy of the area and the physiology and mechanics of hernia formation. An understanding of the embryology of the inguinal canal is helpful. 28 issue 3, 2003 References 1. Agur, Anne, Editor, 9th Ed (1991). “Grants Atlas of Anatomy”. Williams & Wilkins: Baltimore. 2. Anderson, K.N.; Anderson, L.E. and Glanze, W.D., Editors (1998) Mosby’s 6. Clemente, Carmine D, 1997, 4th Ed. “A Regional Atlas of The Human Body”. Williams & Wilkins: Baltimore. 7. Friedland, Tom, (date unknown). “XVI. ICMC-Abdominal Wall, including Hernias”. Viewed August 2002, <http:// www.medicine.mcgill.ca/mss/NTCs/ Med> 8. Hamilton, W.J. and Mossman. H.W. 4th Ed (1972). “Human Embryology”. W. Heffer & Sons Ltd:Cambridge. 9. Kemp, Simon & Batt, Mark E. (1998). “The Sports Hernia: A Common Cause of Groin Pain”. The Physician And Sports medicine. Vol.26 No1. 10. Orchard, J.W, Read, J.W.,Neophyton, J. and Garlick, D. (1998). “Groin pain associated with ultrasound finding of inguinal canal posterior wall deficiency in Australian Rules Footballers”. British Journal of Sports Medicine. Vol 32. 11. Pick, T. Pickering and Howden, Robert, Editors, (1977). “The Classic Collectors Edition- Gray’s Anatomy”. Bounty Books:New York. 12. Warwick, Roger and Williams, Peter, Editors 35th ED(1973). “Gray’s Anatomy”. Longman:Norwich. soundeffects