Spigelian Hernia: Clinical Features and Management

Abstract

The Spigelian hernia is a rare variety of ventral hernia and has an incidence ranging from 0.1–2% of all abdominal wall hernias. It occurs through a well-defined defect in the Spiegel’s fascia adjacent to the semilunar line. It can be congenital or acquired. The acquired variety is predisposed by stretching and weakening of the abdominal wall by factors that increase the intraabdominal pressure. These hernias are most commonly located in the interparietal plane with no visible or palpable mass, and only 50% of cases could be diagnosed clinically before any surgical intervention. Radiological investigations like USG and CT scans confirm the clinical diagnosis or pick up the subclinical varieties that present with non-specific pain in the anterior abdominal wall. Surgery is the mainstay of management. These hernias are prone to early incarceration and strangulation and therefore should be operated at the earliest. It is stressed that a prosthetic mesh should be used for a better outcome as it decreases recurrence. Conventional open hernioplasty has been largely replaced by a laparoscopic approach such as TAPP, TEP, IPOM and robotic-assisted surgery. Early diagnosis and surgery prevent morbidity and dreaded complications.

1. Introduction

Hernias penetrating the anterior abdominal wall are considered the ventral hernias, and the majority of these are formed by the inguinal, femoral and umbilical hernia. Rare varieties include the lumbar and Spigelian hernias. The Spigelian hernias, principally acquired, has an incidence ranging from 0.1–2% of all abdominal wall hernias [1, 2]. These hernias occur through a well-defined defect in the Spiegel’s fascia of the anterior abdominal wall adjacent to the semilunar line, which corresponds anatomically to the lateral edge of the rectus abdominis muscle. These hernias, therefore, are also known as the “spontaneous lateral ventral hernia” or “hernia of the semilunar line”. Commonly it occurs at the lower part of the abdomen, below the umbilicus where the posterior rectus sheath is deficient.

2. History

The semilunar line, originally named the “linea semilunaris spigelii” (the line of Spiegel), is named after the Flemish anatomist and surgeon, Adrian van der Spiegel (1578–1625) who first described the anatomical and surgical significance of well-known linea semilunaris [1]. He defined it as the line of transition between the muscle and aponeurosis of transversus abdominis muscle, extending from the ninth costal cartilage to the pubic tubercle with a lateral convexity sometimes easily described as the lateral border of the rectus sheath. Although, Spiegel first described the linea semilunaris, it was not until more than hundred years later the Spigelian hernia was first described clinically by another Flemish anatomist and surgeon Josef Thaddaei Klinkosh in the year 1764, setting forth the surgical significance of this line [3]. He described it as a ventral hernia developing at the site of linea spigelii, and distinctively coined the name Spigelian hernia.

3. Surgical anatomy

The Spigelian line marks the transition from transverse abdominis muscle to aponeurosis. The part of this aponeurosis that lies lateral to the rectus abdominis muscle is called Spigelian fascia/aponeurosis. Hence Spigelian aponeurosis is limited medially by the lateral edge of the rectus muscle and laterally by the semilunar line. Thus, anatomically the Spigelian fascia is the medial part of the transversus aponeurosis between the lateral border of the rectus sheath and semilunar line and stretches from the tip of the 9th costal cartilage until the pubic tubercle. The Spigelian hernia can occur at any point through this fascia.

The crescentic shape and wide variability in the width of Spigelian aponeurosis craniocaudally predispose to the specific site of these hernia formations (Figure 1). The Spigelian line in the cranial part of the abdominal wall lies close to the rectus abdominis muscle, and hence the Spigelian aponeurosis is very narrow in this zone, due to the presence of more muscular three flat muscles of the abdominal wall attaching to the lateral border of the rectus sheath. Thereby the muscular fibres and aponeurosis of the external and internal oblique muscles overlap the narrow Spigelian aponeurosis. This is probably the main reason why these hernias are uncommonly found above the umbilicus. It is also seen that the fibres of the internal oblique and transverse abdominis muscle run at an angle to each other above the umbilicus thereby providing additional strength and preventing hernia formation. More commonly these hernias are located in an approximately 6 cm transverse imaginary zone extending from the interspinal line to 6 cm superior to it. The Spigelian fascia is widest here with the greatest abdominal circumference and highest intra-abdominal pressure. Due to its etiological significance, this belt is aptly known as the Spigelian hernia belt [4].

Figure 1.

Schematic diagram showing the Spigelian fascia and Spigelian hernia belt.

The size of the hernia orifices usually ranges from 0.5 to 2 cm in diameter. It has a well-defined, firm edge and is round to oval in shape (Figure 2). This well-defined, fibrous, inelastic edge is believed to increase the risk of incarceration and leads to a condition akin to Richter’s hernia formation [5, 6, 7, 8, 9]. In the beginning, these hernias are usually limited to the Spigelian aponeurosis on the axial plane, but when their size increases, these can dissect the fibres of transverse abdominis muscles laterally as its medial extension is limited by the rectus muscle and sheath, and create a bigger defect in the anterior abdominal wall. Another probable reason for its lateral position is because that the external oblique aponeurosis covers the Spigelian aponeurosis in its whole length and creates a potential space between the muscle layers. This provides enough space for the herniated sac to expand and take the route of least resistance laterally and is thus palpable more lateral than the actual location of the hernia orifice. This usually conforms to a mushroom-shaped appearance of these hernias on palpation.

Figure 2.

Schematic diagram showing herniation through the Spigelian hernia. Note the hernial sac is obscured under the external oblique aponeurosis.

In most patients, due to the presence of the tough external oblique aponeurosis, a small Spigelian hernia may go unnoticed. For the Spigelian hernia to be palpable clinically, it needs to penetrate both the transverse abdominis, internal oblique muscles and further glide in between the two oblique muscles. Further, the dissection of the internal oblique is determined by the fact whether the internal oblique muscle ventral to Spigelian aponeurosis is aponeurotic or muscular. In the event the hernial sac encounters an aponeurotic layer in its way, the hernia sac will tend to lie between the transversus abdominis and the internal oblique muscles. Although, the aponeurosis of the internal oblique muscle strengthens the Spigelian fascia, more often than not it is the internal oblique muscle belly rather than the aponeurosis that covers the Spigelian fascia, thereby reducing the reinforcement. In cases when the hernial sac grows and dissects the two innermost muscle layers, the hernia may become palpable clinically. Most commonly these are palpable below the level of the umbilicus as the fibres of the transversus abdominis and internal oblique muscles run parallel to each other in this area, thus reducing the resistance further. Above the umbilicus, these muscle fibres form a criss-cross configuration providing additional support and resistance and thereby decreasing the chance of a Spigelian hernia to be palpable but at the same time increasing the chance for incarceration.

It was usually believed that Spigelian hernias tend to occur through small defects in the transversus abdominis aponeurosis where it was penetrated by the perforating vessels and nerves [10, 11]. These were also thought to occur at the junction of the semilunar line and semicircular line of Douglas as the majority of cases were described below the umbilicus in the region of the line of Douglas. This observation was attributed to the fact that not only Spigelian fascia is broadest here but also the lack of posterior rectus sheath represents the inherent weakness of this zone, and also due to fibres of transversus aponeurosis that runs parallel to the internal oblique. This concept was first challenged by Webber et al., who demonstrated that approximately 45% of Spigelian hernias occurred above the arcuate line [12]. Interestingly, although most of these hernias can occur in the Spigelian hernia belt below the umbilicus for the aforementioned reasons [13, 14], the defect may still lie above the arcuate line. The hernia sac usually consists of the peritoneum, preperitoneal fat and occasionally transversalis fascia. The hernial content can be small bowel or omentum but can include any organ depending on its location. The size of the neck has been reported to vary from as small as 0.5 cm to as large as 6 cm [15].

4. Pathophysiology

These hernias can be congenital or acquired. Congenital cases develop through the weak areas in the aponeurosis of the abdominal muscles formed during their development in the mesenchyme of the somatopleure originating from the invading and fusing myotomes of the anterior abdominal wall and are usually associated with cryptorchidism [14, 16]. The congenital variety presents in the younger age, is usually small and mostly remains subclinical. Adult hernias are usually acquired. The perforating vessels were believed to create the area of weakness in the Spigelian fascia which was enhanced by herniation of preperitoneal fat, although this is now considered of minor importance [17]. Spigelian fascia is widest below the umbilicus and potentially weakest. Besides, the abdominal girth is wider below the umbilicus and in accordance with the Laplace’s law, wall tension will be greater. Furthermore, transversus abdominis and internal oblique muscles in the upper part of the abdomen extent medially into the posterior rectus sheath and strengths the Spigelian fascia. The natural progression of the disease ranges from younger patients usually presenting with a smaller fascial defect with preperitoneal tissue being the most common content. However, with increasing age, elderlies are vulnerable to the development of larger defects with peritoneal contents constituting the main sac content [18].

Besides the anatomical factors, hernia formation can be predisposed by stretching of the abdominal wall by factors that increase the intraabdominal pressure such as chronic cough, chronic obstructive pulmonary disease, obesity, ascites, pregnancy. It has also been described as a complication of chronic ambulatory peritoneal dialysis [19, 20].

Besides these, scarring from previous abdominal surgeries, paralysis of the anterior abdominal wall may weaken the Spigelian aponeurosis and create an area of weakness [21].

It has also been reported that the creation of pneumoperitoneum during laparoscopic surgeries can predispose to herniation through a pre-existing weakness in the Spigelian fascia [22].

5. Epidemiology

The true prevalence of Spigelian hernia remains elusive as the majority of these cases are asymptomatic. A recent study showed that on ultrasonographic examination of 785 anterior abdominal wall hernias, only 1.4% of patients had Spigelian hernias indicating the rarity of the condition [23]. In another study, 2% of incidental Spigelian defect was identified during laparoscopic procedure further affirming the uniqueness of this hernia [24]. Spigelian hernias are slightly more common in females, occur mostly on the right side and usually affect people in their fourth to the seventh decades of life [25, 26, 27]. However, the laterality of these hernias is a contentious issue and as in other studies, left side location has shown predominance [28, 29]. Nevertheless, the underlying reasons are unknown and laterality remains inconsequential to its management.

6. Clinical features

The majority of these hernias are asymptomatic and accordingly the diagnosis is difficult, especially when these are of smaller size. The intraparietal location with overlying tough external oblique aponeurosis and thick subcutaneous fat mask their detection during a clinical examination. However, in patients who present with symptoms, these may range from nonspecific abdominal pain to a palpable lump or a visible mass in the abdominal wall to dangerous features of incarceration with or without features of strangulation. The characteristic of pain depends on the size and contents of the hernia. This may be a dull, sharp, or even burning type. However, one symptom is usually constant, and the pain is aggravated with increased intraabdominal pressure and often after a heavy meal, exercise, walking and running, and is relieved with rest and lying down. Nonetheless, the occult nature of these hernias predisposes them to incarceration and the risk of strangulation requiring emergency laparotomy is up to 24% [30, 31, 32] which is way above the 5-year strangulation risk of umbilical hernia (4%) and inguinal hernia (2.5%) [33, 34].

In cases of a visible lump, it is delineated when the anterior abdominal wall is made taut and the patient is in the upright position, but disappears when the patient lies down. With the increase in size, the lump tends to expand laterally and caudally between the layers of two oblique muscles. Therefore, at times, the patient may present with a non-specific bulge without a definite well-demarcated palpable lump which may be due to a typical T-shaped hernial sac causing elevation of the intact external oblique aponeurosis. The diagnosis of hernia can be affirmed if the swelling can be reduced, but reappears in the upright position and especially with the manoeuvres that increase intraabdominal pressure such as coughing, straining or a Valsalva manoeuvre, and disappears on lying down.

Palpation of the hernia defect in most cases is difficult as these defects are small and are masked by the tough external oblique aponeurosis and subcutaneous fat. However, an attempt should be made to palpate the abdominal wall after making the musculature taut to identify any local tenderness indicating the point of the hernial orifice, which may be the only sign in case of occult or a subclinical Spigelian hernia. This may be attributed to the fact that reinforcing manoeuvres that increase intraabdominal pressure pushes out the preperitoneal fat or a hernial sac through the defect. Palpation of these structures against the inelastic margin of the hernial orifice and stimulation of stretch receptors located in the parietal peritoneum produce distinct point tenderness which is more of somatic pain in nature and hence is easily localised [35]. Although, not pathognomonic, this examination has high sensitivity and can help in screening patients with occult herniation. Sometimes, patients report extreme tactile hyperesthesia which is located just medial to the hernia defect. This is generally believed to be caused by mechanical irritation of the perforating branch of the corresponding intercostal nerve (Valleix phenomena) and this sign can aid in clinical diagnosis of a subclinical herniation [36]. For patients presenting with abdominal pain but no visible lump, radiological investigations like ultrasonogram and/or CT-scan of the abdomen can be of foremost importance. Furthermore, in cases where the diagnosis remains elusive even after radiological investigations, a diagnostic laparoscopy may be of help [28].

7. Diagnosis

These hernias are most commonly located in the interparietal plane with no visible or palpable mass as discussed above, and only 50% of cases could be diagnosed clinically before any surgical intervention [17]. Their tendency to masquerade other clinical conditions presenting with abdominal pain requires a high index of clinical suspicion.

The most common symptoms are mild pain aggravated by coughing, straining, exercising and being relieved by lying down. Although, occasionally a lump may be noted, the diagnosis is often missed unless the patient presents with partial bowel obstruction. The clinical examination alone is believed to be 100% sensitive with a PPV of 36% when compared with operative findings [35].

The diagnostic imaging mainly aims at identifying the hernia defect, sac and its content.

7.1 X-rays

It is a poor modality for diagnosing these hernias. It can neither aid in demonstrating the defect nor the content, especially the omentum or preperitoneal fat. However, in cases in which the sac contains a portion of the small or large bowel, barium studies can be of help. Besides, for diagnosing the complications of these hernias such as intestinal obstruction, a conventional x-ray can be used.

7.2 Ultrasonography (USG)

It is considered the investigation of choice and is usually the first-line imaging modality often used. It should be performed in patients presenting with obscure pain in the abdomen with or without a lump and is helpful both in clinical and subclinical hernias. It helps in the identification of a hernia defect, sac, and its content. It has the additional advantage of providing real-time scanning images by changing the patient’s position and performing manoeuvres that increase the intraabdominal pressure and precipitates any fascial defects or herniation of fat or viscus.

Using a 3.5 MHz transducer, the examination is first performed with the patient in the supine position and the abdominal wall relaxed. A screening USG is performed for intraabdominal viscera to rule out any potential intraabdominal pathology as a cause of pain. Next a higher denomination transducer, typically 5 MHz is used for the parietal wall structures. Scanning is begun at the lateral end of the rectus muscle with parasagittal sweeps. This helps in visualising the rectus muscle. In longitudinal scans, echogenic strips can be visualised, the deepest of which is the parietal layer, more superficial are the layers of the ventral wall. The hernia defect is seen as a disruption of these echogenic strips (Figure 3). The visualisation of the defect and the interparietal location of the sac represent the typical Spigelian hernia with omentum as its content. In difficult cases, the patient may be instructed to increase intraabdominal pressure through Valsalva manoeuvre, which may demonstrate the fascial disruption, and herniation of preperitoneal fat or abdominal viscus. In correlation with the operative findings, a real-time USG scan is believed to have a sensitivity of 90% and PPV of 100% [35].

Figure 3.

Dynamic USG of the abdominal wall showing a Spigelian hernial sac (1.6 cm) penetrating through the Spigelian fascia, seen here as a broken line in the muscle-fascial plane. The right rectus muscle is marked as “R” in yellow.

7.3 Computed Tomography (CT) scan

It is considered as effective as the USG for demonstration of the hernial orifice. Additionally, it provides better information of abdominal wall resistance. Overall, the CT scan has a sensitivity and PPV of 100% each when compared with operative findings [35]. But, the USG is easier to perform, is a clinic procedure, is less expensive and can help in the dynamic analysis of the patient for which it is an excellent screening tool for the lesion. In cases where USG gives inadequate or equivocal information, a CT scan should be added.

7.4 Surgical exploration

On many occasions, the preoperative diagnosis may remain obscure until surgical exploration is performed. In a study by Weiss et al., approximately 50 percent of cases are diagnosed on exploration [37].

Therefore, for diagnosing Spigelian hernias, a dynamic USG and CT scan are useful when used in tandem with the clinical examination. In cases of uncertainty, diagnostic laparoscopy can be used in a symptomatic patient.

8. Differential diagnosis

Depending on its location, a Spigelian hernia may mimic intra-abdominal pathologies which can present with pain such as acute appendicitis, twisted ovarian cyst, tubo-ovarian pathologies, mesenteric lymphadenitis, biliary colic, peptic ulcer pain, pancreatic pain or mesenteric ischemia [35]. Many times one may confuse it with any other disease entity of the abdominal parietal wall too. If the hernia is palpable at the location of pain and if it is reducible, the diagnosis is easy. In instances when the lump is palpable in a typical location but not reducible, the differential diagnoses include hematoma of rectus abdominis muscle, lipoma, chronic abscess, lymphadenopathy, other ventral hernias, solid tumours of the abdominal wall such as a desmoid tumour [35]. In cases where it is not palpable and the patient presents with non-specific pain or if a mass is present in the ventral wall, which is irreducible, the first step is directed towards identifying the nature of the swelling by a dynamic USG. If a Spigelian hernia is suspected, the attempt should be made to localise the hernial orifice. USG can help in differentiating hematoma, abscess, lipoma or seroma. Myotendinitis of rectus abdominis or external oblique muscle can mimic the tenderness present in subclinical cases. In cases where the defect is not found, and diagnosis is obscured, patients should be worked up and investigated for gastrointestinal and genitourinary disorders. An abdominal CT scan reinforces the diagnosis or helps in excluding the differential diagnoses, particularly whether the pain arises from the intra-abdominal pathologies or from the parietal abdominal wall. It is important to keep in mind that in a difficult clinical situation where the diagnosis is elusive or when a subclinical Spigelian hernia is suspected, every effort should be made to rule out an intra-abdominal pathology first. In the pursuit of diagnosing a suspected Spigelian hernia, an important intra-abdominal pathology should not be missed.

9. Classification

Spigelian hernias are the subgroup of primary ventral hernias and the European Hernia Society (EHS) classification system is most commonly used for their classification [38]. However, Webber et al. (2017) have described three clinical stages which reflect the natural history of the condition and provide universality for their management (Table 1) [12].

Stages	Anatomy	Clinical Feature	Treatment
I	Defect: <2 cm; Content: interstitial fat only with no peritoneal component	Intermittent, well-localised pain but no palpable swelling	Open surgery: they are not visible laparoscopically
II	Defect: 2–5 cm; Content: peritoneal component present	Palpable swelling	Laparoscopy/Open repair
III	Defect: >5 cm	Large hernia with distortion the of abdominal wall	Open repair

Table 1.

Clinical stages of Spigelian hernia.

10. Treatment

Operative management of these hernias is advisable as the risk of strangulation or incarceration has been reported up to 25% [39]. Initially open anterior approach with primary closure of the defect or mesh placement in cases where primary closure was not possible was advised. With the technical progress of laparoscopy, its use in the diagnosis and repair of Spigelian hernias has made it the method of choice [40]. It provides the benefits of minimally invasive surgery like reduced post-operative pain, less chance of infection, shorter hospital stays, reduction in morbidity and better cosmesis. However, according to the recent EHS guidelines, it is suggested that Spigelian hernia should be repaired with mesh. The approach, either open or laparoscopic may depend on the surgeon’s expertise, because the strength of recommendation is weak as limited comparative data is available [41]. A randomised trial comparing 11 conventional and 11 laparoscopic repairs in elective Spigelian hernia surgery revealed significant advantages for laparoscopic repair in terms of morbidity (wound complications) and hospital stay [42].

The most popular laparoscopic repairs are the Intraperitoneal Onlay Mesh (IPOM) technique (35%), Total Extraperitoneal Patch (TEP) approach (30%), Transabdominal Preperitoneal (TAPP) approach (22%), and laparoscopic suturing techniques [43, 44]. The TEP repair of Spigelian hernia offers the advantage of avoiding breach in the peritoneal layer as it accesses only through the preperitoneal space. Although, studies have failed to demonstrate the superiority of the extraperitoneal approach over intraperitoneal repair, the intraperitoneal laparoscopic Spigelian hernia repair is considered the gold standard because of its technical advantages [45].

11. Operative techniques

11.1 Conventional open approach

A transverse incision is placed over the lump and the external oblique is incised in its direction to expose the peritoneal sac which can simply be inverted (Figure 4). The hernia defect can be closed with sutures but in cases of larger defect, a mesh should be used which is placed either in preperitoneal space or above the fascia.

Figure 4.

Open surgical repair of a subclinical Spigelian hernia containing protrusion of preperitoneal fat only (sacless).

11.2 Laparoscopic transabdominal preperitoneal repair (TAPP)

Once the hernial sac contents are reduced, the preperitoneal flap is raised and dissected for 5 cm around the hernial defect. The mesh is placed in the extraperitoneal space and the peritoneal flap is closed. The TAPP provides the opportunity to explore the abdominal cavity, although a potential drawback may be the possibility of intraperitoneal adhesions after the surgery, the chances of which, however, are almost similar to that of other laparoscopic surgery. At times, difficulty in the closure of the peritoneal flap may be encountered because of the thin and fragile peritoneum in this location [45].

11.3 Laparoscopic total extraperitoneal repair (TEP)

The extraperitoneal space is created by open access and a balloon is used to create and enlarge the working space. The hernial sac is identified and closed. A large mesh is used to cover the hernia defect and is fixed to the abdominal wall. Although, this approach prevents access to the intraperitoneal cavity for inspection of any concomitant pathology, it reduces the risk of adhesions [46] besides possible benefit to explore and treat the concomitant direct inguinal hernia [47]. TEP repair is expensive due to the price of balloon dissector, technically challenging with a longer learning curve [48] and can be used only if the hernia is located below the arcuate line [49].

11.4 Intraperitoneal onlay mesh repair (IPOM)

Intraperitoneal access is gained using either closed or open techniques. The hernial site is identified and port placement is done in the form of an arc or a circle with the centre at the defect site which should be at least 10 cm away. The contents are reduced and a coated mesh is fixed to obtain an overlap of at least 5 cm around the defect. It provides the opportunity to explore the abdominal cavity and therefore is helpful in emergency conditions with the incarcerated hernia [50, 51]. It is also believed to be the easiest to learn and safe to perform [52]. Nonetheless, the main limitation to this technique is the risk of hematoma formation and nerve entrapment after tack or stapler application. The use of fibrin sealant in place of tacks provides the solution [53].

11.5 Robotic-assisted technique

The use of robotics on ventral wall hernias are easier due to a 360-degree rotation, camera use, surgical forceps and excellent visualisation of the defect. The placement of sutures also makes the procedure easier. The postoperative pain score reported is also lower [54]. Although, robotic-assisted Spigelian hernia surgery provides technical advantage and reliability, further studies with longer follow-ups are required for conclusive analysis [55].

Postoperative complications include seroma and hematoma formation, surgical site infection, abdominal viscera injury, mesh infection, and recurrence. Nerve entrapment during mesh-tacker placement can lead to abdominal pain syndromes [55].

12. Low Spigelian hernias

Spigelian aponeurosis extends caudally up to the pubic tubercle and is found medial to the inferior epigastric artery within the Hasselbach’s triangle. Hernias penetrating the fascia transversalis here are conveniently called the low Spigelian hernias. These hernias usually contain preperitoneal fat but occasionally the bladder may also be involved.

Direct inguinal hernias are located at a similar triangle and may therefore cause diagnostic confusion. Differentiating these hernias from the direct inguinal hernia is important because the risk of incarceration is higher. Due to a small but well-defined hernia orifice, hernioplasty is easier to perform with a lesser chance of recurrence. Digital palpation with the little finger in the inguinal canal in standing position and Valsalva manoeuvre touches the first phalanx in case of low Spigelian hernia and the middle one in direct inguinal hernia. This technique has been proposed to distinguish between these two hernias, but can be uncomfortable and even painful for the patient. The diagnosis can be confirmed by radiological investigation and final assessment is best done intraoperatively [56]. Although, very rare, if both the hernias are found it is most likely due to weakness of Spigelian fascia around the insertion of rectus abdominis [45].

13. Subclinical Spigelian hernia: the great masquerader

The diagnosis of a small Spigelian hernia is extremely challenging, given its rarity combined with nonspecific pain symptoms. Secondly, often due to its intramural location, its detection by palpation can be extremely difficult. Therefore, a great deal of clinical intelligence is invested in its preoperative diagnosis and the ignorance of its existence can cumulate to catastrophic complications of strangulation. Often only a point tenderness corresponding to the site of the defect is the only finding on palpation of the abdominal wall after making the muscles taut [57]. These hernias are small and often may contain only the preperitoneal fat protrusion through the fascial defect (Figure 4), which is something similar to the sacless epigastric hernia. As mentioned previously, only less than half of the cases are detected preoperatively. Therefore, patients presenting with non-specific pain in the abdomen should alert the astute clinician for the possibility of a Spigelian hernia. Once the diagnosis is established, treatment is elementary with surgery being the treatment of choice in symptomatic cases.

14. Conclusion

Spigelian hernias are notoriously difficult to diagnose. If these are visible and palpable, diagnosis is straight forward. But if the hernia is subclinical, it is difficult to diagnose, and only radiological investigations such as a dynamic USG or CT-scan of the abdomen wall can pick up the lesion. A strong clinical suspicion helps to diagnose the occult variety, which presents as non-specific abdominal pain, otherwise about 50% remain undiagnosed until surgery. Due to the high risk of incarceration and strangulation, these hernias should be operated early. Open conventional surgery has been largely replaced by laparoscopic mesh hernioplasty.

Conflict of interest

Authors declare no conflict of interest.

Funding

Nil.