Spigelian Hernia: Why It’s Easy to Miss and How to Fix It

A spigelian hernia is a rare defect in the abdominal wall where tissue, fat, or an organ pushes through a weak spot in the transversus abdominis muscle’s aponeurosis, a band of tough fibrous tissue that runs along the side of the abdomen. It accounts for roughly one to two percent of all abdominal wall hernias, and its reputation as a diagnostic puzzle is well earned. Unlike a typical inguinal or umbilical hernia, a spigelian hernia often hides beneath intact muscle layers, making it invisible on the surface even when it causes real pain.

Where Exactly It Happens

The defect sits in what surgeons call the spigelian aponeurosis, the strip of tissue between the outer edge of the rectus abdominis muscle (your “six-pack” muscle) and the semilunar line, a curved boundary running from the lower ribs down to the pubic bone. The hernia pushes through a slit-like opening in this aponeurosis, usually where the muscle wall is naturally thinnest.¹ About ninety percent of these hernias appear below the belly button, concentrated in a zone roughly six centimeters wide just above the level of the hip bones. This strip is sometimes called the “spigelian hernia belt,” and it corresponds to the area where the back layer of the rectus sheath ends, leaving less structural support.² Hernias higher up or very close to the groin do occur but are uncommon enough that surgeons need to carefully distinguish them from direct inguinal or other groin hernias.³

Why It Is So Easy to Miss

Most hernias announce themselves with an obvious bulge. A spigelian hernia frequently doesn’t. The hernia sac often slips between the layers of the abdominal wall muscles and sits beneath the external oblique aponeurosis, the outermost muscular layer. That means the hernia can be completely hidden, with no visible lump at the skin surface.⁴ What patients do notice is localized pain on one side of the lower abdomen, often made worse by exercise, coughing, or straining. A doctor examining the area may find a tender spot that becomes more noticeable when the patient tenses the abdominal muscles, but in many cases the physical exam alone is inconclusive.

This can lead to years of misdiagnosis. One reported case involved a 55-year-old woman who endured intermittent right-sided abdominal pain for five years before imaging finally revealed a defect in the spigelian fascia with bowel pushing through it.⁵ In another case, a patient with focal tenderness in the right lower quadrant had both ultrasound and CT scans come back unremarkable, and the hernia was ultimately found during laparoscopy.⁶ That second case is a reminder that even imaging, while powerful, is not infallible for this particular hernia.

Adding to the diagnostic confusion, the palpable mass (when there is one) may migrate away from the actual defect in the aponeurosis. The hernia can dissect through muscle layers and present some distance from the semilunar line, which means a surgeon cutting directly over the lump might not find the real hole at first.⁷

The Role of Imaging

When a spigelian hernia is suspected, CT scanning is the most reliable tool. In one study comparing imaging and clinical assessment against what surgeons actually found during operations, CT had a sensitivity and positive predictive value of 100 percent. Ultrasound performed well too, with 90 percent sensitivity and 100 percent positive predictive value. Clinical examination alone, by contrast, had 100 percent sensitivity but only a 36 percent positive predictive value, meaning doctors could feel that something was wrong most of the time but frequently guessed the wrong diagnosis without imaging backup.⁸

Ultrasound has the advantage of being quick, inexpensive, and performed in real time, so the technician can ask you to cough or bear down and watch whether something pushes through the muscle. CT provides a more complete picture, especially when surgeons need to plan a repair or rule out complications like bowel getting trapped in the hernia. In practice, many patients end up getting a CT because initial ultrasound results can be equivocal, particularly if the hernia is small or intermittent.

Conditions that can look similar on imaging or during physical examination include rectus sheath hematomas, fluid collections, abscesses, and even tumor deposits along the abdominal wall.⁹ Getting the diagnosis right before surgery matters, because the surgical approach changes depending on what the problem actually is.

Why Surgeons Recommend Fixing It

Unlike some other hernias where a “watch and wait” approach is reasonable, spigelian hernias carry a significant risk of their contents getting trapped. The defect in the aponeurosis tends to have sharp, well-defined edges rather than a gradually thinning area, which means tissue that slides through can get pinched. The risk of strangulation, where blood supply to the trapped tissue is cut off, is estimated at somewhere between 17 and 24 percent.¹⁰ Other estimates put the incarceration risk at up to roughly 25 percent.¹¹ Strangulated bowel is a surgical emergency that can lead to tissue death and serious illness, so most surgeons advise elective repair once the diagnosis is confirmed rather than waiting for a crisis.

Surgical Repair Options

There are three broad approaches to fixing a spigelian hernia: open surgery, laparoscopic (keyhole) surgery, and robotic-assisted surgery. Current European Hernia Society guidelines do not declare a definitive winner between open and minimally invasive methods, leaving the choice to the surgeon’s judgment and the patient’s circumstances. What the guidelines do recommend is using mesh reinforcement regardless of the approach, except potentially in very small defects where suture repair alone may suffice.¹²

Open Repair

Open repair involves making an incision directly over the hernia, pushing the protruding tissue back into the abdomen, and reinforcing the defect with synthetic mesh. A common technique places the mesh between the external and internal oblique muscle layers, which avoids putting the mesh directly against the bowel while still providing strong reinforcement.¹³ In some cases the mesh is placed as an onlay, secured on top of the closed defect with non-absorbable stitches and enough overlap to distribute tension.¹⁴ Open repair is straightforward, can be done under spinal anesthesia rather than general anesthesia, and is particularly suitable for emergency cases where bowel may be compromised.

Laparoscopic Repair

Laparoscopic repair uses small incisions and a camera to work from inside the abdomen. A systematic review of the laparoscopic literature found that the intraperitoneal onlay mesh technique was the most widely used method, and all reported techniques showed minimal complications and low recurrence rates.¹⁵ A small randomized trial comparing conventional and laparoscopic repair found advantages for the laparoscopic approach in terms of fewer wound complications and shorter hospital stays.¹⁶ Laparoscopy also has a diagnostic advantage: if there is any doubt about the diagnosis beforehand, the camera lets the surgeon confirm the hernia and inspect the defect directly before proceeding with the repair.

Robotic-Assisted Repair

Robotic surgery adds articulated instruments and enhanced three-dimensional visualization to the laparoscopic approach. The experience reported so far is limited, but early results are promising. One group described successful robotic repair of bilateral spigelian hernias using a transabdominal preperitoneal technique, noting that the robotic platform allowed more precise tissue handling than standard laparoscopy.¹⁷ Another series reported three incarcerated spigelian hernias successfully repaired robotically with mesh, with the patients recovering without complications.¹⁸ Robotic repair is particularly appealing for complex scenarios like bilateral hernias or cases where a spigelian hernia exists alongside inguinal hernias, because the robot can address multiple defects through the same set of ports.¹⁹

Recovery and Recurrence

Most patients go home within a day or two after repair. In one robotic case, the patient was discharged on the first day after surgery and was pain-free with no recurrence at the one-month follow-up.²⁰ Longer-term data are encouraging. A twelve-year institutional series reported a recurrence rate of about four percent, with an overall complication rate under eight percent at a median follow-up of three years.²¹ Another study using an open preperitoneal flat mesh technique found a recurrence rate of about two and a half percent.²² A study with a particularly long follow-up of nearly nine years found that 87 percent of patients had no pain at all, 13 percent had mild symptoms, and there were two recurrences (four percent).²³ Taken together, these figures suggest recurrence sits in a low single-digit range, especially when mesh is used.

The Link to Inguinal Hernias

Something that has caught surgeons’ attention in recent years is how often spigelian hernias appear in people who have already had inguinal hernia repairs. In one case series of 24 spigelian hernias, 15 occurred on the same side as a previous inguinal hernia repair. In nearly half of those 15 cases, the spigelian hernia showed up within two years of the inguinal surgery.²⁴ Whether these spigelian hernias were already present but overlooked during the first operation or developed afterward because of tissue disruption during inguinal repair is still debated. Either way, it is worth knowing that if you have had inguinal hernia surgery and develop new lower abdominal pain on the same side, a spigelian hernia should be on the list of possibilities.

In rare cases, multiple types of hernia can coexist at once. One report described a patient found to have a midline umbilical hernia, a right-sided spigelian hernia, bilateral inguinal hernias, and bladder tissue herniating into the right inguinal canal, all in the same person.²⁵ Situations like this are extraordinary, but they underline why thorough imaging matters before planning any repair.

Spigelian Hernias in Children

While the typical spigelian hernia patient is a middle-aged or older adult, children can develop them too, and the pediatric version has a notable twist. In boys, spigelian hernias are strongly associated with an undescended testicle (cryptorchidism) on the same side. An integrative review of pediatric cases found that about a third of children with spigelian hernias also had an undescended testicle, and statistical analysis showed a very strong association between the side of the hernia and the side of the undescended testicle.²⁶

This pairing is now recognized as a distinct clinical syndrome. The leading theory is that during fetal development, the gubernaculum, the cord-like structure that guides the testicle’s descent into the scrotum, becomes mislocated along the abdominal wall in a way that overlaps with the spigelian fascia. The testicle follows this wayward path and ends up inside the hernia sac instead of reaching the scrotum.²⁷ Because of this association, a urologist evaluating a baby boy for an undescended testicle may be the first doctor to discover the hernia.²⁸ Repair in children typically involves returning the testicle to the scrotum and closing the hernia at the same time.

What Can End Up Inside the Hernia Sac

The most common contents of a spigelian hernia are preperitoneal fat, a loop of small intestine, or a piece of the omentum (the fatty apron that drapes over the bowel). Colon can also herniate through. But case reports over the years have documented a surprising variety of contents. In pediatric patients, the list includes Meckel’s diverticulum (a remnant of the umbilical cord connection to the gut), gallbladder, stomach, bladder, ovaries, and, as discussed above, testes.²⁹

In women, gynecologic organs are an uncommon but well-documented finding. One case involved a right ovary and fallopian tube protruding through a two-centimeter defect in the spigelian fascia, discovered during surgery.³⁰ Another report described the same combination of ovary and fallopian tube as the hernia contents in a patient with chronic pelvic and abdominal pain.³¹ These cases matter because they can mimic ovarian pathology or other gynecologic conditions, sending both patients and doctors down the wrong diagnostic path.

Complex and Traumatic Abdominal Wall Defects

Most spigelian hernias are spontaneous, developing gradually due to weakness in the aponeurosis combined with the pressures of aging, obesity, or chronic straining. Occasionally, though, defects in the same anatomical region result from blunt abdominal trauma, such as a seatbelt injury or a direct blow. These traumatic flank hernias along the spigelian aponeurosis can be larger and more destructive than the typical spontaneous hernia, and their repair may require more elaborate reconstruction. One approach for a traumatic defect in this area used a combination of biological mesh as an inlay and synthetic mesh secured to the pelvic bone for additional stability.³² These cases are unusual, but they highlight how the same anatomical vulnerability that allows a small spontaneous hernia can, under the right circumstances, give way to a much larger problem requiring creative surgical solutions.

When mesh is placed inside the abdominal cavity in direct contact with the bowel, surgeons opt for composite or coated mesh designed to reduce the risk of adhesions, where loops of intestine stick to the mesh surface and can cause obstruction or pain later on. For mesh placed between muscle layers or in the preperitoneal space (behind the abdominal wall muscles but in front of the peritoneum), standard polypropylene mesh is the most common choice. The guideline recommendation is that whatever mesh is used should overlap the edges of the defect by at least five centimeters in all directions to distribute tension and prevent recurrence.³³

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