spigelian hernia

World J. Surg. 13, 573-580, 1989

World Journal of Surgery �9 1989 by the Soci~t~

lnternationale de Chirurgie

Spigelian Hernia

L e i f S p a n g e n , M . D .

Department of Surgery, Central Hospital, Karlstad, Sweden

The diagnosis of spigelian hernia presents greater difficulties than its treatment. The clinical presentation varies, depending on the contents of the hernial sac and the degree and type of herniation. The pain, which is the most common symptom, varies and there is no typical pain of spigelian hernia. Findings to facilitate diagnosis are palpable hernia and a palpable hernial orifice. Large, easily palpable spigelian hernias are not a diagnostic problem. It is small hernias and hernial orifices that are overlooked because they are masked by the subcutaneous fat and an intact external aponeurosis. In the absence of a palpable orifice or sac, persistent point tenderness in the spigelian aponeurosis with a tensed abdominal wall most strongly suggests the diagnosis. Spigelian hernia can be ruled out in patients without palpable tenderness. Ultrasonic scanning can be recommended for verification of the diagnosis in both palpable and nonpalpable spigelian hernia. The hernial orifice and sac can also be demonstrated by computed tomography, which gives more detailed information on the contents of the sac than does ultrasonic scanning.

The treatment of spigelian hernia is surgical, and the risk of recurrence is small. A gridiron incision is excellent for operations for palpable hernias. If the hernia cannot be palpated preoperatively, preperitoneal dissection through a vertical incision is recommended. This gives good exposure, facilitates hernioplasty, and permits preperitoneal exploration and treatment of other abdominal wall hernias. The incision is also suitable for exploratory laparotomy, which should be performed on patients with abnormal uitrasonographic or computed tomographic findings in whom no palpable hernia can be detected preoperatively.

Spigelian hernia has a well-defined anatomic location lateral to the rectus muscle in the anterior abdominal wall. Its diagnosis can be difficult because there are no characteristic and constant symptoms or clinical findings and because of the interparietal nature of the hernia. Many physicians are also unaware of its occurrence. This leads to underdiagnosis of this rare hernia.

The purpose of this article is to call attention to this hernia and describe how it may most easily be diagnosed. A proper understanding of both the clinical features and the diagnosis requires a good knowledge of the topographic anatomy of the anterior abdominal wall. A relatively large part of this article will, therefore, be devoted to definitions and anatomy. The surgical treatment is usually simple and will, therefore, only be briefly described.

Reprint requests: Left Spangen, M.D., Department of Surgery, Central Hospital, 651 85 Karlstad, Sweden.

Inc idence

In 1764, Klinkosch [1] was the first to definitely describe a spigelian hernia. A review of the literature in October, 1988 revealed that 876 patients had been operated on for spigelian hernia. The mean age of the patients in the compiled material was 50.5 years, and the female-to-male ratio was 1.4:1. The right-to-left-side ratio was 1.18:1. Twenty-nine instances of bilateral hernias were reported. In 6 patients, there was more than 1 hernia on the same side. Only 29 of the hernias were located above the umbilicus. Most spigelian hernias have been diagnosed in patients between 40 and 70 years of age. Twenty- eight children, 17 boys and 11 girls, younger than 16 years of age were operated on for spigelian hernia. Incarceration at the time of operation was seen in t01 of 419 reported hernias (24.1%). More than 280 articles on spigelian hernias have been published. Some of the largest series are listed in Table 1 [2-15]. There are 5 medical theses on Spigelian hernia, by the following authors: Ferrand, 1881 (Paris) [16]; Baudoin, 1912 (Paris) [17]; Pabst, 1925 (Halle) [18]; Nachtwey, 1932 (K61n) [19]; and Spangen, 1976 (Stockholm) [20].

Definit ions and Topograph ic A n a t o m y

Adriaan van den Spieghel (1578-1625) did not diagnose spigelian hernia, but he did describe the important anatomic structure, the linea semilunaris (Spigelii). This is the line forming and marking the transition from muscle to aponeurosis in the transversus abdominis muscle [21].

The part of the aponeurosis that lies lateral to the rectus abdominis muscle is usually called the spigelian fascia. To avoid misunderstanding and to use correct anatomic nomenclature, I will henceforth call this part of the transversus aponeurosis the spigelian aponeurosis. The spigelian aponeurosis is, thus, limited laterally by the semilunar line and medially by the lateral edge of the rectus muscle (Fig. 1). As is seen in Fig. 1, the semilunar line, which is a lateral convex line, lies within the cranial part of the abdominal wall dorsal to the rectus muscle, thus there is no spigelian aponeurosis in this area. This is one reason why the number of reports of spigelian hernia above the umbilicus is so small. Another reason is that above the umbilicus the fibers of the transversus abdominis and internal oblique muscles cross one another at angles, making herniation more

574 World J. Surg. Vol. 13, No. 5, Sept./Oct. 1989

| Fig. 1. A ventral view of the abdominal wall showing the topographic anatomy. The external and internal oblique and rectus abdominis muscles are cut away. 1: Transversus abdominis muscle, 2: Dorsal lamella of the rectus sheath, 3: The semicircular line (of Douglas), 4: The semilunar line (Spigelii), 5: Spigelian aponeurosis, 6: Spigelian hernia belt, 7: Hes- selbach triangle, 8: Inferior epigastric vessels, 9: Anterior superior iliac spine, 10: Interspinal plane.

Table 1. Large series of spigelian hernias.

Author Year No. of hernias

Spangen [2] 1984 45 ~ Stuckej et al. [3] 1973 43 b Houlihan [4] 1976 31 c Persson et al. [5] 1975 19 Ponka [6] 1980 19 a Gullmo [7, 8] 1980, 1984 13 Lindholm and Hulin [9] 1969 12 Kienzle and Staemmler [10] 1978 12 Stirnemann [11] 1982 12 Holder and Schneider [12] 1974 10 Weiss et al. [13] 1974 10 Lamphier [14] 1982 10 Bonini et al. [15] 1987 9

Includes 12 low spigelian hernias. b CompiLation of all spigelian hernias from a single

from 1951 to 1971. c Compilation of all spigelian hernias from a single

from 1963 to 1971. a Includes 2 low spigelian hernias.

department

department

unlikely than if the fibers were to run parallel, as they do below the umbil icus.

A hernia may occur throughout the length of the spigelian aponeurosis . The term spigelian hernia usually refers to hernias

located above the inferior epigastric vessels. About 9 of 10 of these hernias occur within a t ransverse belt lying 0-6 cm cranial to the interspinal plane (Fig. 1). This is called the spigelian hernia belt [20]. The spigelian aponeurosis is widest here (on average, about 2 cm), and this feature has been accorded etiologic importance [22, 23].

The hernial orifice is 0.5-2.0 cm in diameter. It is oval to round with well-defined and firm edges. In hernias of this size, the orifice is usually limited to the spigelian aponeurosis . An increase in size of the hernial orifice, if it occurs, is in the lateral direction through dissection of the fibers of the muscle belly in the t ransversus abdominis. In the medial direction, extension of the hernial orifice, as well as the sac, is stopped by the rectus sheath and the rectus muscle.

Spigelian aponeurosis is also to be found caudal and medial to the inferior epigastric artery, i.e., within the Hesselbach triangle (Fig. 1). Hernias that penetrate the aponeurosis here are called low spigelian hernias and will be described at the end of this article. The external oblique muscle is aponeurot ic ventral to the spigelian aponeurosis throughout its length. The layer between the 2 oblique muscles is loose and acts normally as a glide layer. A hernial sac can easily expand in this space and, therefore, adopts a typical T- or mushroom-shaped appearance. The space is largest laterally (Fig. 2), so large spigelian hernias

L. Spangen: Spigelian Hernia 575

Fig. 2. Schematic cross-section of ventral abdominal wall cranial to the semicircular line, indicating the possible location of the hernial sac in spigelian hernias. 1: External oblique muscle, 2: Internal oblique muscle, 3: Transversus abdominis muscle, 4: Rectus abdominis muscle, 5: Peritoneum, 6: Spigelian aponeurosis, 7: Dorsal lamella of the rectus sheath, 8: Intravaginal hernia, 9: Semilunar line (Spigelii), 10: External oblique aponeurosis, 11 : Subcutaneous tissue.

can be palpated laterally to the spigelian aponeurosis. That the hernia is palpated more laterally than the location of the hernial orifice often makes it more difficult to diagnose. The external aponeurosis is so thick that it is rarely penetrated by the hernia. This explains why only 15 of 876 patients have been reported to have a subcutaneously located hernial sac.

A hernia usually penetrates both the transversus abdominis and internal oblique muscles (Fig. 2). The internal oblique

muscle ventral to the spigelian aponeurosis may consist either of muscle belly or of aponeurosis. Its fibers are strongly adherent to the underlying spigelian aponeurosis. A hernia, therefore, usually penetrates both these musculoaponeurotic layers. When the internal oblique muscle is aponeurotic, its fibers subsequently strengthen the spigelian aponeurosis. If the internal oblique muscle consists of muscle fibers, the spigeiian aponeurosis is not as strongly reinforced. My own observations have also shown that the internal oblique muscle in this region usually consists of muscle in patients with spigelian hernias [20]. In some instances, the hernial sac lies between the transversus abdominis and internal oblique muscles (Fig. 2). This is possible if the internal oblique muscle consists of muscle fibers that are elevated by a small hernia. When the hernia grows, it probably dissects the muscle fibers so that the sac penetrates the glide layer between the 2 oblique muscles. Below the umbilicus, the fibers of the 2 muscles run almost parallel. In such situations, the fibers can be more easily separated than if the fibers cross one another at an angle as they do above the umbilicus. The risk of herniation is, therefore, greatest below the umbilicus. In most instances, the hernia is located between the musculoaponeurotic layers of the anterior abdominal wall and is, therefore, called interparietal, intramuscular, or intramural. Because it is difficult to palpate, the hernia has often been called occult or masked. Beneath the spigelian aponeurosis are preperitoneal fat and peritoneum.

Most spigelian hernias are reported to lie in the vicinity of the semicircular line (Fig. 1). AboVe the semicircular line, the spigelian aponeurosis divides into 2 layers, which blend with the anterior and posterior lamellae of the rectus sheath. The dorsal lamella becomes thinner and weaker as one approaches the semicircular line. This is one of the most important reasons why most spigelian hernias are located here. Caudal to this line, the spigelian aponeurosis is a single layer and, therefore, stronger again. The location and appearance of the semicircular line vary highly. During my anatomic studies in 1976, I could show that the most lateral point of the semicircular line was located an average of 2 cm cranial to the interspinal plane, i.e., within the spigelian hernia belt.

The hernial orifice, which is within the spigelian ap0neurosis, is well-defined and has fibrous and inelastic edges. This largely explains why the risk of incarceration is high in spigelian hernia and why a Richter hernia may develop [24-28].

Etiology

Congenital spigelian hernia has been reported, but the condition is normally acquired. The structure of the spigelian aponeurosis and bordering aponeuroses and muscles in the anterior abdominal wall is the most important etiologic factor. It is possible that the preperitoneal fat can contribute to the development of hernia by infiltrating the spigelian aponeurosis [16, 17, 29]. That a spigelian hernia may consist of preperitoneal fat alone and that the hernial sac is always surrounded by prolapsing preperitoneal fat, being thickest at the top, support this theory. Other predisposing factors are the same as for other types of hernias-- for example, those resulting in increased intra-abdominal pressure. In the upright position, the intraabdominal pressure is highest below the umbilicus, which means that the pressure on


Table 2. Uncommon contents found in the sacs of spigelian hernias.

Content No. of Author Year of sac hernias

Beluzzi [35] 1957 Stomach 1 Kirchberger [36] 1867 Gallbladder l Durst et al. [37] 1977 Gallbladder 1 Massabuau et al. [38] 1933 Meckel 1

diverticulum Chalier [39] 1948 Strangulated 1

appendix Ferrand et al. [40] 1956 Strangulated 1

appendix Blikra [41] 1959 Strangulated 1

appendix Hibbard and Schumann [42] 1962 Strangulated 1

appendix Spangen [20] 1976 Strangulated 1

appendix Jain et al. [43] 1977 Strangulated 1

appendix Nauta et al. [44] 1986 Crohn 1

appendicitis Nadjafl and Maurer [45] 1967 Appendix 1

epiploica Biaggi et al. [46] 1977 Appendix 1

epiploica Benjamin and Webber [47] 1966 Taenia coli 1 Cullen [48] 1911 Ovary 1 Mathews [49] 1923 Ovary 1 Lamb [50] 1962 Endometriosis 1

in the sac Louw and Lauritzen [51] 1981 Leiomyoma 1

of the uterus

Schools [52] 1895 Testicle 1 Gravier et al. [53] 1978 Testicle 1

the abdominal wall is greatest here. This could be another reason why spigelian hernias occur most often in this region.

It was previously believed that neurovascular openings in the spigelian aponeurosis may become enlarged, permitting herniation [30, 31]. This is now considered to be of minor importance [2, 32]. It has also been suggested that constriction by scarring from previous abdominal operations may weaken the spigelian aponeurosis [33]. Paralysis may also be a predisposing factor

[341.

Diagnosis

Symptoms

The symptoms that cause a patient to consult a physician are usually pain, a palpable mass in the anterior abdominal wall, and signs of incarceration with or without intestinal obstruction. The most frequent symptom is pain. A spigelian hernia in its earliest form is often simply a protrusion of preperitoneal fat through the spigelian aponeurosis, a condition similar to fatty hernia of the linea alba. The hernia can also be part of an extraperitoneal organ, but a peritoneal sac is found in most instances. If there is content in the peritoneal sac, it is usually greater omentum, small intestine, or part of the colon. Other organs are found in the sac less often (Table 2) [35-53].

A patient 's symptoms vary depending on what the hernia contains. A decisive factor is also whether the hernia is repositioned and whether there is incarceration (with or without intestinal obstruction). The pain, therefore, varies in type, severity, and location, and there is no typical or characteristic pain of spigelian hernia. The pain may be dull, burning, or "dragging" in nature and is usually aggravated by straining and relieved by rest. In patients with nonrepositioned hernias, the hernia can often be palpated as a resistance in the anterior abdominal wall. As already mentioned, the diagnosis of large hernias may be complicated by the fact that the hernia is mainly located lateral to the hernial orifice. It may be difficult, often impossible, to detect a smaller hernia if it is located between the muscle coats of the abdominal wall (interparietally). The patient, and often also the physician, then thinks there is a diffuse local increase in consistency without a palpable hernia. The swelling is probably caused by elevation of the intact external aponeurosis by the hernial sac, which has adopted the typical T shape. If a hernia is palpable and can be repositioned, the diagnosis should be easy to make, provided the possibility of a spigelian hernia is considered. The same applies if the hernia appears when the patient is upright and repositions spontane- ously when the patient lies down or if it appears when the patient strains or lifts heavy loads. This illustrates the importance of examining a patient in both the upright and supine positions and with the abdominal musculature both relaxed and tensed.

The hernial orifice, which is usually small, can seldom be detected because it is masked by the subcutaneous fat and the usually intact external aponeurosis. If the orifice is so large that a fingertip can be inserted, it can often be palpated when the abdominal wall is tensed. If there is no palpable resistance in the abdominal wall, the hernia may be repositioned but, as mentioned earlier, a small hernia lying under the external oblique aponeurosis may, unfortunately, not be evident (occult or masked spigelian hernia). Even if the hernia and the orifice are not palpable, it is important to palpate with the abdominal musculature tensed because a distinct tender point can always be palpated in the spigelian aponeurosis over the hernial orifice. Local tenderness may be the only sign of the hernia.

During Valsalva maneuvers, preperitoneal fat and the hernia are forced through the hernial orifice. The palpating finger presses these structures against the inelastic, well-defined edge of the hernial orifice. This brings about an afferent flow from pain and stretch receptors present in abundance in the parietal layer of peritoneum and in the preperitoneal fat. In small, nonrepositioned but nonpalpable hernias, the explanation for the distinct tenderness on palpation is similar. In the absence of a palpable ring or sac, persistent point tenderness of a tensed abdominal wall is the clue most strongly suggesting the proper diagnosis. The test is not pathognomonic for spigelian hernia but can be used for screening. Patients without distinct tenderness in the spigelian aponeurosis with the abdominal wall tensed do not have spigelian hernias, whereas those with such tenderness may have.

Sometimes pinprick and tactile hyperesthesia of the abdominal wall just medial to the hernial orifice can be demonstrated. This is caused by mechanical irritation of the medial sensory branch of the corresponding intercostal nerve.


Fig. 3. Ultrasonic examination of a patient with a nonpalpable spigelian hernia. A longitudinal section of the abdominal wall reveals a defect in the preperitoneal fat line and in the line from the internal oblique and transversus abdominis aponeuroses. 1: Subcutaneous tissue, 2: External oblique aponeurosis, 3: Inter- nal oblique and transversus abdominis aponeuroses, 4: Preperitoneal fat, 5: Parietal peritoneum, 6: Hernial orifice (diameter, 14.7 ram), 7: Spigelian hernia containing intestine, 8: Prolapsing preperitoneal fat.

Diagnostic Procedures

If a history and physical examination suggest that a patient has a spigelian hernia, the diagnosis must be verified before the decision is made to operate. The diagnostic procedures are mainly aimed at demonstrating a hernial orifice or sac and at obtaining information on any sac contents. This should be possible if there is a palpable hernia.

Roentgenography. If there is palpable resistance in the abdominal wall, roentgenography may be considered to obtain a correct diagnosis. A prerequisite for the diagnosis of a spigelian hernia is that the hernial sac has an intramural or subcutaneous location and that it contains intestine filled with gas or, after a barium meal, intestine filled with contrast medium. If the sac contains a portion of large intestine, such can be demonstrated after a barium enema. A sac containing omentum cannot be demonstrated by a conventional roentgenographic examination. If the sac is empty, plain abdominal roentgenograms and contrast studies are usually not conclusive. It should be possible to demonstrate an empty sac by herniography with positive contrast medium. It has proved difficult to demonstrate small or even medium-sized hernial sacs by herniography. Herniogra- phy can usually detect large hernias, but the diagnosis of such hernias is usually clear after a physical examination. The diagnostic accuracy of this invasive procedure is, therefore, rather low [7, 8, 54].

The hernial orifice cannot be demonstrated by a roentgenographic examination. If the hernia is repositioned, there is no roentgenographic examination apart from herniography to facilitate the diagnosis of spigelian hernia.

Ultrasonic Scanning. Ultrasonic scanning is a valuable diagnostic tool in both palpable and nonpalpable spigelian hernias [20, 55-58]. The diagnosis is based on demonstration of a hernial orifice in the spigelian aponeurosis, on an intramurally located hernial sac, and on sac content in the form of intestine or omentum.

Ultrasonography with a 5.0- or 3.5-MHz transducer is used. The examination is performed with the patient in the supine position with the abdominal muscles well relaxed. Scanning is begun with parasagittal sweeps starting at the lateral aspect of the rectus muscle and continuing laterally. The examination is completed with transverse scans and, if necessary, scans in several other different planes. In longitudinal scans (Fig. 3), echogenic stripes can be seen below the subcutaneous fat, running almost parallel to the outline of the skin. The deepest stripe represents preperitoneal fat and parietal peritoneum. The other stripes represent muscle or aponeurotic layers of the ventral abdominal wall. In a transverse scan one can easily see the rectus abdominis muscle. More lateral, depending on the level, are, again, the previously mentioned stripes. Interruption in the deepest line may represent an early herniation.

For a hernial orifice to be demonstrated with ultrasound, it must lie within a well-defined aponeurosis, which the spigelian aponeurosis is. The hernial orifice is visualized as a defect in the echo line from the aponeurosis. Usually, there is also an interruption in the stripe representing the preperitoneal fat and peritoneum. The defect also causes a stronger than normal echo from underlying intestine in contact with the hernial orifice. The visualization of a hernial orifice and the interparietal location of the herniation establish the diagnosis even in the absence of herniated loops of intestine. If the sac content is omentum, this has a typical appearance. Many patients complain only of nonspecific abdominal discomfort and do not have a palpable mass or defect. As previously stated, patients with spigelian hernia always have a distinct tenderness over the hernial orifice on palpation. Ultrasonography shows whether there is a hernial orifice, and the accuracy of this procedure is high [20, 56].

Computed Tomography. Computed tomography (CT) has been tested in the diagnosis of palpable spigelian hernia and gives information about the hernial orifice, the sac and the sac contents [5%62]. For demonstration of a hernial orifice in the spigelian aponeurosis, ultrasonography (US) and CT are prob-


ably equally effective. Computed tomography, however, may provide more information than US in the examination of abdominal wall resistance. Ultrasonography is easier to perform and is also considerably less expensive. It seems reason- able to perform US first and supplement it with CT if it does not give sufficient information.

Surgical Exploration. Many spigelian hernias remain undiag- nosed until an exploratory laparotomy. The operation is usually done because of acute or chronic pain or because of incarceration with or without intestinal obstruction. In the series of Weiss and associates [13] the correct preoperative diagnosis was made in only 92 of 178 instances.

Differential Diagnosis

Because a spigelian hernia can cause so many different symptoms, the condition may be mistaken for both intraabdominal diseases and other lesions in the anterior abdominal wall. Resistance in the abdominal wall, tenderness on palpation of the spigelian aponeurosis, and pain must, therefore, all be considered in the differential diagnosis.

If a hernia can be repositioned, the diagnosis is usually easy. If there is a large hernia that cannot be repositioned, a palpable mass is present in the anterior abdominal wall. If there is clinical suspicion of a spigelian hernia, the first step is to search for a hernial orifice in the spigelian aponeurosis. If a defect or local tenderness in the spigelian aponeurosis is found, the next step is US or CT.

Although the list of possibilities in the differential diagnosis of superficial masses in the abdomen is long, it is the discontinuity of the spigelian aponeurosis demonstrated by US or CT that is important in making the diagnosis of a hernia. Ultrasonography may give falsely normal results, but this is rare. An intrapari- etally located lipoma tender on palpation is not uncommon, but US gives the correct diagnosis. Ultrasonography gives different findings for intraparieteal lipoma and for hernial sacs containing omentum. If there is acute resistance with concomitant pain, the possibility o fa hematoma or an abscess must be considered, apart from an incarcerated spigelian hernia. A hematoma or a seroma can be diagnosed by US [63, 64]. If gas can be demonstrated in the mass, it is difficult to distinguish between an abscess and an incarcerated hernia containing intestinal gas. A correct diagnosis can be obtained by CT or surgical exploration. As already mentioned, it is unusual that a hernial orifice in the spigelian aponeurosis cannot be visualized with US, but falsely abnormal results are occasionally obtained. If the semicircular line is distinct, the point where it crosses the spigelian aponeurosis may be mistaken for a hernial orifice on US. If there is adhesion of intestine or an organ to the spigelian aponeurosis, the criteria for a hernial orifice may be present. The reason is that an aponeurosis and connective tissue in an adhesion have approximately the same acoustic impedance [20, 64]. Myotendinitis in the external oblique muscle or in the tendinous intersections in the rectus abdominis muscle can be diagnosed by electromyography.

The medial branch of an intercostal nerve passes through the spigelian aponeurosis and the anterior lamella of the rectus sheath about a fingerwidth more medially. If the nerve branch is irritated, there is a distinct palpable tenderness over the neu-

rovascular hiatus in the rectus sheath. If a spigelian hernia is present, there is also a tender point over the hernial orifice in the spigelian aponeurosis. In both situations, a well-defined pinprick hyperesthesia is found in the skin innervated by the nerve. In spigelian hernia, this nerve irritation may be caused by direct pressure on the nerve or neuropraxia caused by a reflex increase in local muscle tone. Patients with symptomatic indirect inguinal hernias may exhibit tenderness in the spigelian aponeurosis several centimeters above the internal inguinal ring [65]. It is this condition that most often simulates a spigelian hernia between the interspinal plane and the inferior epigastric vessels. In patients without a palpable hernia or hernial orifice who seek treatment because of uncharacteristic abdominal pain, gastrointestinal disorders must be differentiated from spigelian hernias. It must be remembered that a spigelian hernia detected during investigation for pain in this group of patients may be asymptomatic. In obscure situations, it is, therefore, important to obtain complete gastrointestinal studies and to investigate the genitourinary system.

Surgical Treatment

A spigelian hernia should be treated surgically. The operation is usually simple to perform and gives good results. Only 6 recurrences have been reported [3, 9, 32, 45, 66, 67].

In palpable hernias, a gridiron incision is excellent. One can usually easily locate the hernia after splitting the external oblique aponeurosis. The simplest form of hernioplasty is usually quite sufficient. A short incision should also be made in the anterior lamella of the rectus sheath, thereby reducing the risk of not detecting an intrafascial hernial offshoot (Fig. 2) [8].

If there is no palpable hernia or hernial orifice, a preperitoneal dissection through a paramedian incision gives good exposure. This approach enables one to inspect a large part of the spigelian aponeurosis without cutting muscles and aponeuroses ventral to it. Additional hernias and defects in the aponeurosis can be identified and closed, and it is also easy to strip the preperitoneal fat around the hernial orifice. A paramedian approach also permits preperitoneal exploration and treatment of other abdominal wall hernias. The incision is highly suitable for exploratory laparotomy, which is recommended in patients with no palpable hernia or hernial orifice but with preoperative ultrasonographic or CT findings consistent with a spigelian hernia. These patients may have an asymptomatic spigelian hernia detected in the course of the investigation. A laparotomy should, therefore, always be performed to rule out any other or additional causes of the patient's symptoms. In patients with no palpable hernia or hernial orifice, a gridiron incision may be used in selected patients if US or CT has shown that the hernial sac lies between the 2 oblique muscles. The hernia is then visible when the external aponeurosis is split, ff the internal oblique muscle is intact over the hernia, it is difficult to locate through a gridiron incision. In these circumstances, preperito- heal dissection through a longitudinal incision is recommended.

Low Spigelian Hernia

As previously mentioned, spigelian aponeurosis is also present caudal and medial to the inferior epigastric vessels and extends down to the pubic tubercle. The aponeurosis is part of the


posterior wall of the Hesselbach triangle. Both direct inguinal hernias and low spigelian hernias may, therefore, occur within the triangle. As in other spigelian hernias, the hernial orifice is small and localized to a well-defined aponeurotic plate. Hernio- plasty is, therefore, much simpler to perform than in direct inguinal hernias, and the risk of recurrence is much smaller. The risk of incarceration is higher than in direct inguinal hernia. A distinction should, therefore, be made between these 2 hernias.

A low spigelian hernia usually consists of preperitoneal fat alone but may also involve the bladder. Therefore, it is sometimes included among the supravesical hernias [6]. If there is a hernial sac, it may contain omentum or intestine.

It is not possible to distinguish a low spigelian hernia from a direct inguinal hernia preoperatively. The diagnosis is, therefore, established peroperat ively in connection with operations for inguinal hernias.

R~sum~

Le diagnostic d 'une hernie de Spiegel est plus difficile que son traitement. Les signes de dEcouverte varient, dependant du contenu du sac herniaire, d l ' importance, et du type de la hernie. La douleur, symptEme le plus frequent, n 'est pas typique. Les signes qui aident au diagnostic sont la palpation de la hernie et de l 'orifice herniaire. Lorsque l 'orifice est large et palpable, le diagnostic de hernie de spiegel ne pose pas de problEme. Ce sont les hernies de petite taille, g or i fce rEduit, qui sont souvent masqu~es par la graisse sous-cutanEe et l 'aponEvrose oblique externe. En l 'absence d'orifice ou de hernie palpable, la persistance de la douleur ~t la palpation au niveau de l 'aponEvrose, alors que la paroi abdominale est sous tension, est significative. En l 'absence de cette douleur provo- quEe, on peut pratiquement 61iminer ce diagnostic. On conseille de verifier le diagnostic par une 6chographie, que cette douleur existe ou pas. L'orifice et le sac herniaire se voient bien 6galement par la tomodensitomdtrie plus performante que l '~chographie en ce qui concerne le contenu herniaire.

Le traitement de la hernie est chirurgical; le risque de rEcidive est rEduit. Une incision centrEe sur la bernie, sans section musculaire, est excellente. Si la hernie ne peut ~tre palpEe, on conseille une incision verticale avec un abord extrap~riton~al. L 'exposi t ion est excellente, la cure est aisEe et l 'explorat ion prEpEritonEale ainsi facilitEe, permet en outre la cure d 'autres hernies pariEtales associEes. La m~me incision convient 6galement pour une laparotomie exploratrice, au cas oa l '~chographie ou la tomodensitomEtrie ne montrent rien de sp~cifique et o~ il n 'existe pas de hernie d~tectEe prEopErati- vement.

Resumen

E1 diagndstico de la hernia spigeliana presenta mayores dificul- tades que su tratamiento. La presentaci6n clinica varia segt~n el contenido del saco herniario y el grado y tipo de herniaci6n. E1 dolor, que es el sfntoma mils comt~n, es variable y no existe un dolor que sea tfpico de la hernia spigeliana. Los signos ffsicos que facilitan el diagnEstico son la hernia palpable y un orificio herniano palpable. Las hernias spigelianas grandes y fficilmente palpables no constituyen un problema diagn6stico. Son mils

bien las hernias pequefias y los orificios mfnimos los que pueden pasar desapercibidos al ser enmascarados por la grasa subcu- t~nea y por una aponeurosis intacta. En ausencia de un orificio o de un saco palpable, el dolor a la presi6n sobre la aponeurosis spigeliana, manteniendo tensa la pared abdominal, sugiere fuertemente este diagn6stico; la hernia spigeliana puede ser exclufda como posibilidad diagn6stica en pacientes que no exhiban tal dolor a la palpaci6n. La ultrasonograffa puede ser recomendada para verificaci6n del diagn6stico, tanto en las hernias spigelianas palpables como en las no palpables. E1 orificio y el saco herniarios tambiEn pueden ser demostrados mediante tomograffa computadorizada, estudio que provee informaci6n m~is detallada que la ultrasonograffa sobre el contenido del saco.

E1 tratamiento es qui~rgico y el riesgo de recurrencia es bajo. Una incisi6n oblicua o transversa resulta excelente para la operaci6n en hernias palpables; si la hernia no es palpable en el examen preoperatorio, se recomienda realizar disecci6n preperitoneal a trav~s de una incisi6n vertical. Esto da buena exposici6n, facilita la hernioplastia, y permite la exploraci6n preperitoneal y el tratamiento de otras hernias de la pared abdominal. La incisi6n tambiEn es adecuada para la laparot- omfa exploratoria, la cual debe ser realizada en pacientes con hallazgos anormales en la ultrasonograffa o en la tomograffa computadorizada y en quienes no haya sido posible detectar una hernia palpable preoperatoriamente.

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