Spigelian hernias

INTRODUCTION — First described in 1764 by Josef Klingosh, Spigelian hernias are an uncommon type of primary ventral hernia (figure 1). The hernia is named after Adriaan van den Spieghel, who is credited with describing the linea semilunaris, nearly 100 years prior to the first description of this hernia [1,2].

The clinical presentation, diagnosis, and management of Spigelian hernias are presented here. The diagnosis and management of other types of abdominal wall hernias can be found in other topics. (See "Overview of abdominal wall hernias in adults" and "Management of ventral hernias".)

EPIDEMIOLOGY — Spigelian hernias are rare and only account for 0.1 to 2 percent of all ventral hernias [3]. The incidence of Spigelian hernias is increasing, which may be related to widespread use of high-quality cross-sectional imaging, misdiagnosis of lateral incisional hernias (eg, port site hernia) as Spigelian hernias, or a true increase due to the obesity epidemic [4]. There is no clear sex predilection [5,6], and most patients are diagnosed in the fifth or sixth decade of life. These hernias are rarely described in children. When diagnosed in the pediatric population, they may be associated with other anomalies such as undescended testes [2,4].

ETIOLOGY AND RISK FACTORS — Spigelian hernias are primary ventral hernias secondary to a defect in the Spigelian aponeurosis (fascia) that is comprised of the transversus abdominis and internal oblique aponeuroses. The borders of the Spigelian aponeurosis are the rectus muscle medially and the linea semilunaris laterally (figure 2). Although Spigelian hernias can develop anywhere along the entire length of the Spigelian aponeurosis, they most commonly occur in the region from just below the level of the umbilicus to the interspinal plane (a horizontal line between the right and left anterior superior iliac spine). This region is often referred to as the Spigelian hernia belt [2,4]. An anatomic explanation for the Spigelian hernia belt may be that below the level of the umbilicus, the fibers of the internal oblique and transversus abdominis muscles run in parallel, as opposed to at angles at the level of the umbilicus and above [7]. Spigelian hernias do not disrupt the external oblique aponeurosis [2,4,5].

There are many risk factors associated with the development of Spigelian hernias, including increased intra-abdominal pressure (eg, obesity; multiple pregnancies; chronic cough, especially in smokers) and factors that weaken the tissue layers (eg, disorders of collagen, smoking, or chronic obstructive pulmonary disease) [2]. Blunt trauma is also a well-known cause of disruption of the Spigelian aponeurosis. Whether traumatic hernias at this site should be considered true Spigelian hernias or "incisional hernias" is under debate. Hernias through the Spigelian aponeurosis related to prior incisions (drain placement, laparoscopic ports, paramedian incisions, stoma sites, etc) should be classified as lateral ventral incisional hernias. (See 'Lateral incisional hernias' below.)

CLINICAL PRESENTATION — Patients with a Spigelian hernia may be asymptomatic (hernia detected on imaging performed for unrelated reasons) or present with a swelling in the mid to lower abdomen, just lateral to the rectus muscle. On physical examination, a mass may be palpated in the region of the Spigelian aponeurosis (lateral to the rectus muscle). The patient may also complain of a sharp pain or tenderness at this site. The hernia is usually reducible in the supine position, although up to 20 percent of Spigelian hernias will present incarcerated.

Examination in the supine and standing position and with Valsalva maneuvers can assist with diagnosis [4,8]. In addition, examination in lateral decubitus with the side of concern in the dependent position may be of value.

DIAGNOSIS — Spigelian hernia can be diagnosed clinically if a patient presents with a swelling in the mid to lower abdomen, just lateral to the rectus muscle. However, not all patients with a Spigelian hernia present with a palpable mass even with positioning and Valsalva. This is especially true in patients with obesity [5]. Physical examination alone may only accurately diagnose this rare hernia in about one-half of patients [4]. When Spigelian hernia is strongly suspected, such as in the patient with sharp pain or focal tenderness in the expected location of a Spigelian hernia, imaging should be obtained. Cross-sectional imaging can also help delineate the hernia anatomy.

Diagnostic evaluation — Although historically Spigelian hernias were difficult to diagnose, the widespread availability of high-quality cross-sectional imaging has improved the ability to identify these rare hernias [4,9,10].

Imaging — Abdominal ultrasound, computed tomography (CT), and magnetic resonance imaging (MRI) are valuable adjuncts for diagnosis (image 1 and image 2) [4]. The quality of ultrasound in the diagnosis of Spigelian hernias tends to be operator dependent [5]. CT imaging is advantageous due to its high sensitivity and positive predictive value, availability, speed, and ability to concurrently evaluate intra-abdominal contents/pathology [11,12].

Diagnostic laparoscopy — The use of diagnostic laparoscopy to diagnose Spigelian hernia is debated. A Spigelian hernia may not be easily identifiable during a transabdominal laparoscopic exploration, particularly if peritoneum is not protruding through the fascial defect. A pre- or extraperitoneal approach (either open or laparoscopic) may be necessary to diagnose Spigelian hernias containing interstitial fat (herniated preperitoneal fat) only. These approaches are associated with their own set of risks and complications (particularly in a patient who ends up with no Spigelian hernia) [5].

Classification — Consensus from both the American and European Hernia Societies (AHS and EHS, respectively) recommends that Spigelian hernias be classified as other primary ventral hernias [12]. Primary ventral hernias can be classified as small (<2 cm), medium (2 to 4 cm), or large (>4 cm) [13]. In most reported series, Spigelian hernia defects are small (<2 cm). Spigelian hernias can be either unilateral or bilateral [8,14,15]. Although some series report a significant percentage of patients presenting acutely with incarcerated (20 to 30 percent) or strangulated Spigelian hernias (nearly 15 percent) [2,4], the true risk of incarceration or strangulation is unknown. The increased rates of incarceration and strangulation reported may simply be due to publication bias, failure to diagnose these hernias until acute presentation, or underestimation of the true population prevalence. Because of this, elective repair in patients with Spigelian hernias should be based upon the same criteria as any other primary ventral hernia. (See 'Indications for surgery' below.)

Differential diagnoses

Lateral incisional hernias — A true Spigelian hernia is a primary ventral hernia. Lateral incisional hernias mimicking true Spigelian hernias have been described due to port or drain placement through the Spigelian aponeurosis after minimally invasive prostatectomy and appendectomy [16-18]. They have also been described following open abdominal surgeries such as anterior component separation, ostomy takedowns, paramedian incisions, and Pfannenstiel incisions [19]. Because the majority of the published literature on Spigelian hernias is based on case reports or small case series and many fail to differentiate between true Spigelian hernias and lateral abdominal wall incisional hernias, nearly one-half of patients in the reported literature have had previous abdominal surgery, making the accuracy of the diagnosis of a Spigelian hernia questionable [4,20].

Hernias that are located in or around the Spigelian aponeurosis but that are related to prior surgical incisions should be classified as lateral ventral incisional hernias rather than Spigelian hernias [2,13]. Although this distinction may seem academic, it has implications for case complexity, evidence-based treatment recommendations, and clinical outcomes [21,22]. In general, the management of true Spigelian hernias should follow the recommendations for primary ventral hernias, rather than those for incisional hernias. (See "Overview of abdominal wall hernias in adults", section on 'Specific hernia sites' and "Management of ventral hernias".)

Inguinal hernias — It may be difficult to differentiate between direct inguinal hernias and low Spigelian hernias. Spigelian hernias are classically located above Hesselbach's triangle (bordered by the lateral edge of rectus medially, inguinal ligament inferiorly, and inferior epigastric vessels laterally) (figure 3). Direct inguinal hernias are located within Hesselbach's triangle. However, low Spigelian hernias can occur near Hesselbach's triangle and be confused with direct inguinal hernias [2].

Abdominal wall masses — Abdominal wall masses (benign and malignant) may resemble ventral hernias in any location of the abdomen. Cross-sectional imaging can help differentiate abdominal wall masses from hernias. This is discussed in detail in another topic. (See "Overview of abdominal wall hernias in adults", section on 'Differential diagnosis'.)

TREATMENT — As with all hernias, the only effective treatment for Spigelian hernias is surgical, and the only nonsurgical option is expectant management (ie, watchful waiting). Historically, surgical repair was recommended for all patients with a known Spigelian hernia. However, as with other primary ventral hernias, contemporary management is more nuanced and individualized.

Indications for surgery — Strangulated and acutely incarcerated Spigelian hernias require urgent surgical repair. Decisions about elective repair of Spigelian hernias should be based upon the same criteria as for any other primary ventral hernia: symptoms, increased risk for acute presentation (eg, bowel containing or prior incarceration), and patient choice. Patients who choose to delay surgery should be counseled on the signs and symptoms of incarceration and strangulation and on when to seek acute or elective care.

Patients at high risk for developing complications and recurrences after surgery (eg, uncontrolled diabetes, active smoking, body mass index [BMI] >40 kg/m²) should undergo preoperative optimization before surgery if the hernia is not strangulated or acutely incarcerated [5]. (See "Laparoscopic ventral hernia repair", section on 'Preoperative preparation' and "Management of ventral hernias", section on 'Reducible or chronically incarcerated ventral hernias'.)

Selecting a surgical approach — Historically, only open repairs have been utilized; however, in the contemporary literature, open, laparoscopic, and robotic techniques are described. Single-incision laparoscopic techniques have also been reported [1,23].

Various surgical approaches have been compared. However, given the rarity of Spigelian hernias, the majority of the literature consists of single-center/single-surgeon case series, which need to be interpreted in the context of relatively low-quality data, lack of uniform reporting of outcomes, general lack of long-term follow-up, as well as the low prevalence of these hernias [1]. A very small randomized trial comparing open versus laparoscopic Spigelian hernias credited laparoscopy with fewer postoperative hematomas and a shorter length of hospital stay, but the power of the study was very low due to the small sample size (only 22 patients in total) [24].

For other primary ventral hernias, both randomized controlled trials and large database studies have associated laparoscopic repair with a lower risk of surgical site infection and a comparable recurrence rate to that of open repair [12,25,26]. (See "Management of ventral hernias", section on 'Surgical management of ventral hernias' and "Wound infection following repair of abdominal wall hernia", section on 'Open versus laparoscopic hernia repair'.)

Because Spigelian hernia is a subtype of primary ventral hernias, it would be reasonable to extrapolate such results. Thus, we suggest minimally invasive repair of Spigelian hernias in most elective settings whenever possible [12]. Additionally, transabdominal preperitoneal (TAPP), totally extraperitoneal (TEP), and extended TEP (eTEP) minimally invasive approaches can also diagnose and treat coexisting inguinal/femoral hernias. Any transabdominal techniques can also diagnose and treat a contralateral Spigelian hernia. (See 'Minimally invasive Spigelian hernia repair' below.)

Open techniques may be preferred in the setting of acute presentation, presentation with high-grade bowel obstruction and/or perforation, anticipation of bowel resection, surgeon lack of familiarity and/or experience with laparoscopic techniques, and/or surgeon preference. Open repair is also required when laparoscopic repair is contraindicated by the inability to tolerate pneumoperitoneum or safely access the peritoneal cavity. Open repair should be avoided when the hernia is present on imaging but not apparent on physical examination [12]. (See 'Open Spigelian hernia repair' below.)

PREOPERATIVE PREPARATION

Perioperative pain management — In our practice, we employ multimodal narcotic-sparing pain management strategies, including preoperative nonsteroidal anti-inflammatory medications, acetaminophen, as well as gabapentin or pregabalin. Regional anesthesia, including transversus abdominis, rectus sheath, and/or quadratus lumborum blocks, may be useful in decreasing postoperative narcotic utilization. (See "Laparoscopic ventral hernia repair", section on 'Premedication' and "Approach to the management of acute pain in adults", section on 'Preventive analgesia for postoperative pain'.)

In our practice, patients at high risk for urinary retention (older men, history of benign prostatic hypertrophy, as well as patients undergoing concurrent inguinal/femoral hernia repair) are given tamsulosin or a similar medication preoperatively. (See "Laparoscopic ventral hernia repair", section on 'Premedication'.)

Venous thromboembolism prophylaxis — Perioperative venous thromboembolism (VTE) prophylaxis is administered based on guidelines from the American College of Chest Physicians [27]. In the absence of contraindications, sequential compression devices and early postoperative ambulation are employed liberally. Patients at moderate-to-high risk for VTE events receive pharmacologic perioperative prophylaxis (unfractionated heparin or low-molecular-weight heparin) in addition to sequential compression devices. (See "Prevention of venous thromboembolic disease in adult nonorthopedic surgical patients".)

Preoperative antibiotics — Preoperative antibiotics are generally administered within one hour of incision time as per standard protocols. (See "Antimicrobial prophylaxis for prevention of surgical site infection in adults", section on 'General approach'.)

MINIMALLY INVASIVE SPIGELIAN HERNIA REPAIR

Indications for minimally invasive repair — Based on the best available evidence extrapolated from studies on primary ventral hernia repair, we suggest minimally invasive repair of Spigelian hernias in most elective settings whenever possible. Data on primary ventral hernia repair are discussed in another topic. (See "Management of ventral hernias".)

Absolute contraindications to minimally invasive Spigelian hernia repair are similar to those of other primary ventral hernias and include the inability to tolerate pneumoperitoneum or safely access the peritoneal cavity. Relative contraindications include lack of appropriate surgeon experience and/or resources, gastrointestinal tract perforation or acute high-grade obstruction, and anticipated bowel resection.

Minimally invasive techniques — Laparoscopic techniques for Spigelian hernia repair were first described in 1992 [28] and are increasingly reported. Multiple approaches have been described, including transabdominal (intraperitoneal onlay mesh [IPOM] and transabdominal preperitoneal [TAPP] approaches) as well as totally extraperitoneal (TEP) approaches. A series of 77 patients found laparoscopic TAPP and TEP repair of Spigelian hernias to be equally safe and effective [29]. Extended TEP (eTEP) approaches, which are increasingly described in the treatment of other ventral and incisional hernia repairs, have also been described for Spigelian hernias in small series [30]. Partial preperitoneal approaches have been reported and may have the advantage of minimizing fixation in high-risk areas of the abdominal wall [31]. Techniques have been reported with and without primary fascial closure.

Robotic surgical techniques for abdominal wall hernia repair are increasingly being utilized. Robotics can be utilized to facilitate transabdominal as well as preperitoneal minimally invasive Spigelian hernia repairs; most describe techniques of transabdominal preperitoneal repair [32,33]. However, there is a paucity of published data on the safety and efficacy of robotic repair of Spigelian hernias. One trial associated robotic primary ventral and incisional hernia repair utilizing the IPOM technique with increased cost and operative time but no clinical benefits compared with the laparoscopic IPOM approach [34]. There are currently no published randomized trials comparing the robotic with laparoscopic transabdominal preperitoneal repair of ventral or incisional hernias. (See "Robotic ventral hernia repair".)

Equipment/positioning — For laparoscopic repair, patients should be positioned supine, with arms tucked, and secured to the bed to allow for Trendelenburg and reverse Trendelenburg positioning. Care should be taken to pad all pressure points.

The following equipment should be available for laparoscopic Spigelian hernia repair. If performing a robotic assisted laparoscopic repair, the choice of laparoscope and trocars is dependent on the robotic platform being utilized:

●5 mm, 30 or 45 degree standard operating laparoscope.

●Two or three 5 mm laparoscopic trocars.

●One 8, 10, or 12 mm laparoscopic trocar (for insertion of mesh, depending on size of Spigelian hernia defect and size of mesh utilized).

●Energy device (hook dissector and/or shears with monopolar cautery, and/or ultrasonic or bipolar dissector as per surgeon's choice).

●Mesh (if intraperitoneal mesh positioning is utilized, a macroporous, medium-density polypropylene or polyester mesh with antiadhesive coating appropriate for intraperitoneal placement should be available; if preperitoneal mesh positioning is utilized, uncoated synthetic mesh can be utilized as long as the peritoneal flap created covers the mesh completely). (See "Hernia mesh".)

●Slowly absorbable sutures (eg, 0 polydioxanone) for primary fascial closure and transfascial suture placement. Permanent sutures may also be utilized per surgeon preference.

●Transfascial suture passer.

●Laparoscopic mesh tacking (fixation) device (optional depending on technique). (See "Laparoscopic ventral hernia repair", section on 'Mesh fixation'.)

Abdominal entry and port placement — Peritoneal entry should be accomplished by the technique most familiar to the operating surgeon. We generally enter with a 5 mm optical trocar in the upper quadrant, subcostal location, and lateral to the midclavicular line. There is no evidence that any specific entry technique is superior to others in preventing entry-related major visceral or vascular injuries, and surgeons should choose the approach they feel most comfortable performing [35]. In the reoperative abdomen, the initial entry should be performed away from any previous incisions. Care should be undertaken with peritoneal entry in patients presenting with acute obstruction and significantly dilated intestine, which is a relative contraindication for laparoscopic repair, especially for inexperienced surgeons. (See "Abdominal access techniques used in laparoscopic surgery", section on 'Initial port placement'.)

For a unilateral Spigelian hernia, all three working ports can be placed on the contralateral abdomen, centered around the defect. For bilateral hernias, all three working ports can be placed across the upper abdomen (left and right upper quadrant and central off midline). This port placement works well for robotic-assisted repairs as well.

Intraperitoneal onlay mesh technique — An IPOM or preperitoneal technique can be utilized based on surgeon experience/preference. The 2016 systematic review of laparoscopic repair of Spigelian hernias reported that 45 percent of reported repairs utilized the IPOM approach [1]. This technique tends to be technically easier and faster [28].

For IPOM repairs, we routinely excise the hernia sac and any incarcerated preperitoneal fat [36]. When feasible, we perform primary fascial closure. Randomized controlled trials have associated primary fascial closure during laparoscopic ventral/incisional hernia repair with improved quality of life at up to two years post-surgery [37,38] as well as reduced early seroma formation [39,40]. The fascial defect is most often closed with 0-polydioxanone sutures using stab incisions and a transcutaneous suture passing device. Intracorporeal primary fascial closure can also be performed using barbed sutures; this can be done laparoscopically or with robotic assistance. (See "Laparoscopic ventral hernia repair", section on 'Fascial defect closure'.)

A mid-density mesh with antiadhesion barrier is introduced through an 8+ mm port placed through the hernia defect prior to defect closure. Following primary fascial closure, the mesh is secured circumferentially. Mesh fixation techniques are discussed below. (See 'Mesh fixation' below.)

Preperitoneal techniques — Similar to inguinal hernias, preperitoneal repair of Spigelian hernias may be approached via TAPP or TEP approaches. TAPP approaches may be advantageous when examination of intra-abdominal contents is necessary [2]. TEP approaches are typically associated with the longest operative times and are thought to be the most technically difficult of the three laparoscopic approaches [28]. Familiarity with the techniques of laparoscopic inguinal hernia or preperitoneal ventral hernia repair facilitates laparoscopic preperitoneal Spigelian hernia repair.

For preperitoneal repairs, if a TAPP approach is used, the peritoneum is generally incised and preperitoneal dissection started several centimeters away from the fascial defect to allow for adequate mesh overlap (movie 1). For TEP approaches, the technique is similar to that of TEP inguinal hernia repair, which may use a dissecting balloon to develop the preperitoneal/retrorectus plane. (See "Laparoscopic inguinal and femoral hernia repair in adults", section on 'Techniques for primary hernia repair'.)

As the preperitoneal plane is being developed, the hernia sac and incarcerated contents are reduced, followed by primary fascial closure (per surgeon preference), mesh placement, and closure of the peritoneal flap (if a TAPP approach is utilized).

Contaminated fields — If there is active intra-abdominal infection, inadvertent enterotomy, and/or if bowel resection is required, options include open or laparoscopic suture repair; mesh repair with biologic, bioabsorbable, or permanent synthetic mesh; and staged (delayed) repair. Although historically the placement of intraperitoneal synthetic mesh was not recommended in contaminated fields, several randomized trials (on ventral, as opposed to Spigelian, hernias) have demonstrated the superiority of synthetic mesh over biologic mesh in contaminated fields, including in the intraperitoneal location [41-44]. Further supportive data and continued evaluation of long-term outcomes are likely required before this practice becomes the standard of care. (See "Management of ventral hernias", section on 'Contaminated field' and "Laparoscopic ventral hernia repair", section on 'Mesh material'.)

Mesh fixation — Mesh can be secured with transfascial sutures, tacks, or a combination of both. Controversies regarding mesh fixation techniques are discussed elsewhere. (See "Laparoscopic ventral hernia repair", section on 'Mesh fixation'.)

For the IPOM approach to laparoscopic Spigelian hernia repair, we utilize a combination of transfascial sutures and absorbable or permanent tacks. If tacks are utilized as the sole fixation method, the literature on laparoscopic ventral hernia repair suggests that permanent tacks be utilized. The mesh can also be fixated with running barbed sutures if robotic assistance or articulating laparoscopic needle drivers are available.

For patients with coexisting inguinal hernias, or if the mesh extends beyond the inguinal ligament, tacks, whether absorbable or permanent, should not be placed below the level of the inguinal ligament, to avoid chronic pain or injuring major vasculature. A preperitoneal or partial preperitoneal approach should be considered in these cases. Another potential advantage of preperitoneal mesh placement is the need for minimal or no fixation of mesh. (See "Laparoscopic inguinal and femoral hernia repair in adults", section on 'Mesh placement and fixation'.)

Skin closure — The operative field is carefully examined. Hemostasis is achieved. We will generally close fascial defects for trocars greater than 8 mm or trocars placed in the midline. The peritoneal cavity is desufflated, ports are removed, and the skin is closed per surgeon preference. We generally do not place drains.

OPEN SPIGELIAN HERNIA REPAIR

Indications for open repair — Open techniques may be preferred in the setting of acute presentation, presentation with high-grade bowel obstruction and/or perforation, anticipation of bowel resection, surgeon lack of familiarity and/or experience with laparoscopic techniques, and/or surgeon preference. Open repair is also required when laparoscopy is contraindicated due to inability to tolerate pneumoperitoneum or safely access the peritoneal cavity.

Open techniques — Suture and mesh (preperitoneal, intraperitoneal, or overlay positions) techniques have been described for open repair [6,45]. It is reasonable to extrapolate from the literature on primary ventral hernia repair that mesh placement leads to lower risk of recurrence and should be used in all clean cases [46,47]. Thus, we only perform suture repair of Spigelian hernias in the setting of contamination where mesh placement may potentially increase morbidity. (See "Management of ventral hernias", section on 'Surgical management of ventral hernias'.)

Open repair of Spigelian hernias generally employs the following key steps [2]:

●Skin incision is made over the hernia. Classically, a Gridiron's incision (McBurney's incision) is made at a right angle to a line joining the anterior superior iliac spine and umbilicus, centered on McBurney's point (1/3 of distance to the iliac spine, 2/3 to the umbilicus) (figure 4) [8]. If the hernia/incarcerated contents are not palpated, a paramedian or midline incision can also be utilized [2]. Dissection is carried through the subcutaneous tissues to the level of the external oblique aponeurosis.

●Division of the external oblique aponeurosis along the direction of its fibers.

●Examination and reduction of hernia sac contents.

●Dissection of the hernia sac with development of a preperitoneal plane if preperitoneal mesh placement will be performed.

●Closure of the fascial defect, including closure of the transversus abdominis as well as the internal oblique, with or without placement of mesh.

●Reapproximation of the external oblique aponeurosis. If the overlay technique for mesh placement is used, mesh is placed over the reapproximated external oblique aponeurosis. If mesh is placed under one of the muscle layers (ie, between the internal and external oblique), it would be more accurate to describe this as a sublay technique.

●Closure of subcutaneous tissue and skin.

POSTOPERATIVE CARE/FOLLOW-UP — After elective Spigelian repairs (laparoscopic and open), the majority of patients can be discharged the same day with the use of a narcotic-minimizing perioperative regimen (see 'Perioperative pain management' above). For patients who present acutely, hospital admission may be required depending on the clinical state of the patient. Patients with associated bowel obstruction often need to be observed until they have had return of bowel function and are tolerating an oral diet.

Patients should be seen postoperatively at approximately two to four weeks to evaluate for any postoperative complications. Signs of surgical site infection, including erythema and/or drainage at wound sites, inability to tolerate oral intake, lack of bowel function, or worsening pain, should prompt expeditious evaluation. Restrictions regarding activity, return to work, and driving should be individualized.

COMPLICATIONS — Complications of Spigelian hernia repairs can occur intraoperatively (eg, enterotomy) or postoperatively (eg, ileus, seromas, hematomas, wound infections, urinary retention, chronic pain, recurrence).

It is difficult to estimate the true incidence of complications after Spigelian hernia repair given the rarity of this type of hernia. Additionally, there is a profound lack of consistency and quality in outcomes reporting amongst the examined series, making these data difficult to interpret [1,5,6,48,49].

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Ventral hernia".)

SUMMARY AND RECOMMENDATIONS

●Description – Spigelian hernias are rare defects in the Spigelian aponeurosis located between the rectus muscle medially and the linea semilunaris laterally. They most commonly occur in the "Spigelian hernia belt" between the level of the umbilicus and the interspinal line (a horizontal line connecting the anterior superior iliac spines) (figure 2). (See 'Introduction' above and 'Etiology and risk factors' above.)

●Clinical presentation – Patients with a Spigelian hernia may be asymptomatic (hernia detected on imaging performed for unrelated reasons) or present with pain and/or swelling in the mid to lower abdomen, just lateral to the rectus muscle. On physical examination, a mass may be palpated in the region of the Spigelian aponeurosis (lateral to the rectus muscle). (See 'Clinical presentation' above.)

●Diagnosis – Spigelian hernias can be diagnosed clinically in patients who present with a swelling or mass in the area of the Spigelian aponeurosis. However, physical examination alone may only accurately diagnose this rare hernia in about one-half of patients. Patients who have pain or tenderness but no palpable mass should undergo imaging (abdominal ultrasound, computed tomography, or magnetic resonance imaging (image 1 and image 2)) to confirm the diagnosis. Transabdominal laparoscopy may not identify all Spigelian hernias. (See 'Diagnosis' above.)

●Differential diagnosis – Although true Spigelian hernias are a type of primary ventral hernia, lateral incisional hernias are commonly misdiagnosed as Spigelian hernias. Low Spigelian hernias can also be confused with direct inguinal hernias. Spigelian hernias can be distinguished from abdominal wall masses by imaging. (See 'Differential diagnoses' above.)

●Indications for surgical repair – Strangulated and acutely incarcerated Spigelian hernias require urgent surgical repair. Decisions about elective repair of Spigelian hernias should be individualized based upon the same criteria as for any other primary ventral hernia: symptoms, increased risk for acute presentation (eg, bowel containing or prior incarceration), or patient choice. Patients at high risk (eg, uncontrolled diabetes, active smoking, or body mass index [BMI] >40 kg/m²) should undergo preoperative optimization before elective hernia repair. (See 'Indications for surgery' above.)

●Laparoscopic repair – We suggest minimally invasive Spigelian hernia repair in most elective settings whenever possible (Grade 2C). Compared with open repair, minimally invasive primary ventral hernia repair decreases wound complication rate without increasing recurrence rate. Additionally, both transabdominal preperitoneal (TAPP) and totally or extended extraperitoneal (TEP, eTEP) laparoscopic approaches can diagnose and treat coexisting inguinal/femoral hernias, while any transabdominal laparoscopic approaches can also diagnose and treat a contralateral Spigelian hernia. (See 'Selecting a surgical approach' above and 'Indications for minimally invasive repair' above.)

•Laparoscopic Spigelian hernia repairs can be performed with transabdominal (intraperitoneal onlay mesh [IPOM]) or preperitoneal (TAPP (movie 1)) or TEP or eTEP techniques at the surgeon's discretion. The IPOM technique is fast and easy to learn; the TEP/eTEP technique is most technically challenging. Familiarity with the techniques of laparoscopic inguinal hernia or ventral hernia repair facilitates laparoscopic Spigelian hernia repair. (See 'Minimally invasive techniques' above.)

•For laparoscopic Spigelian hernia repair, we generally close the fascial defect primarily before fixing the mesh with a combination of transfascial slowly absorbable sutures and tacks (permanent or absorbable). Data supporting these practices are extrapolated from the studies on laparoscopic and open ventral hernia repair as studies exclusively on Spigelian hernias are generally of low quality. (See 'Minimally invasive techniques' above and "Laparoscopic ventral hernia repair", section on 'Controversial issues'.)

●Open repair – For patients who present acutely with a Spigelian hernia, especially when there is concern for high-grade obstruction, strangulation, intra-abdominal infection, and/or need for bowel resection, we suggest an open repair (Grade 2C). Additionally, open repair may also be required due to surgeon lack of familiarity and/or experience with laparoscopic techniques, or when laparoscopy is contraindicated due to inability to tolerate pneumoperitoneum or safely access the peritoneal cavity. (See 'Indications for open repair' above.)

•Open Spigelian hernia repair can be performed with sutures or mesh. Given the concern for a higher recurrence rate, we only perform suture repair in the setting of contamination where mesh placement is contraindicated and may potentially increase morbidity. (See 'Open techniques' above.)