Spigelian hernia is a rare form of ventral hernia that occurs along the semilunar line, a curved line of fibrous tissue that lies between the lateral edge of the rectus abdominis muscle and the external oblique muscle. Despite accounting for less than 2% of all abdominal wall hernias, Spigelian hernias are clinically significant due to their subtle and often deceptive presentation. [1,2]

The borders of Spigelian fascia are the eighth or ninth rib superiorly, the pubis inferiorly, the lateral border of the rectus sheath medially and the muscle fibbers of the transversus abdominis (semilunar line) laterally. Spigelian hernia can occur anywhere in this fascia.Most Spigelian hernias penetrate the transversus and internal oblique aponeurosis, leaving the external oblique aponeurosis intact, and then dissect between the internal and external oblique muscle layers^.[3]

We present a case series of spigelian hernia done at a medical college in Southern Rajasthan.

Understanding the surgical anatomy of Spigelian hernia is critical for both diagnosis and surgical intervention. The hernia arises through a defect in the Spigelian fascia, which is a fibrous structure formed by the aponeuroses of the transversus abdominis and internal oblique muscles.^[2]

Key Anatomical Features:

• Spigelian Fascia: Located between the rectus abdominis medially and the semilunar line laterally, it represents a weak point in the abdominal wall where herniation is likely to occur.
• Hernia Belt: Spigelian hernias typically develop in a region known as the "Spigelian hernia belt," situated 6 cm to 8 cm above the inguinal ligament and just below the umbilicus.
• Interparietal Nature: The hernia sac often lies between the layers of the abdominal wall muscles (interparietal), which contributes to the difficulty in palpation and clinical detection.^[6]

Spigelian hernia results from a combination of congenital predisposition and acquired factors, leading to the weakening of the Spigelian fascia and subsequent herniation.

Congenital Factors:

• Anatomical Weakness: Some individuals are born with a naturally weak Spigelian fascia, making them more susceptible to herniation. This congenital predisposition is often unnoticed until adulthood when other contributing factors come into play.^[4]

Acquired Factors:

• Increased Intra-abdominal Pressure: Conditions that raise intra-abdominal pressure, such as chronic cough, obesity, pregnancy, and heavy lifting, can exacerbate the weakness in the Spigelian fascia, leading to hernia formation.^[4]
• Surgical Trauma: Previous abdominal surgeries can compromise the integrity of the abdominal wall, creating a weak spot in the Spigelian fascia.
• Aging and Degenerative Changes: As individuals age, the connective tissue may lose its elasticity and strength, further increasing the risk of hernia formation. ^[3,4]

Pathophysiology:

• The pathophysiology of Spigelian hernia involves the protrusion of intra-abdominal contents through a defect in the Spigelian fascia.
• The hernia sac is often small and may remain concealed within the muscle layers, which is why it does not always produce a visible bulge.
• If left untreated, the hernia can progress to incarceration or strangulation, leading to ischemia of the involved bowel segment and requiring emergency surgical intervention.^[4,6]

Preoperative image of a lady with left sided obstructed spigelian hernia

Inclusion Criteria

1. Inclusion criteria composed of adult patients (18 years and older) who had documented operative management, a documented post-operative follow-up visit and gave consent for inclusion in this article.

Exclusion criteria

1.Pregnant patients

2.Patients not willing to give consent

3.Young adults less than 18 years of age

Materials and methods

All patients were admitted in the department of General Surgery. Patients were enrolled in the study after informed consent. All patients were posted for open mesh repair after pre-operative CT scan and followed up for one year.

Due to the small sample size, no in-depth statistical analysis was devised. However,these are the results are as follows and presented in descriptive statistics. Total number of patients in our study is 12.

Sex ratio

MALE: FEMALE–3:9 (25:75%)

Slight gender predominance seen in women for spigelian hernia. But even in our small number of cases/data, the gender ratio was three times more for women compared to men.

Content of hernial sac

The hernial sac contained omentum in 9 cases. Even in our case series with small number of patients, we found 3 cases where hernial sac contained intestine.

Mesh placement

Sublay mesh placement was done in seven cases whereas onlay mesh hernioplasty was done in remaining five cases in our series. Identical lightweight polypropylene mesh used in all cases only varying in size depending on the size of the defect.

Age

In our study, the mean age of the patients was 56.1 years with the age range being 46 to 66 years.

Site

LEFT SIDED: - 7 (58%)

RIGHT SIDED: - 5 (42%)

Seven patients in our study had left sided spigelian hernia and five had right sided spigelian hernia.

Urgency

EMERGENCY: ELECTIVE SURGERY – 2:10

In this study, 10 patients were posted for elective surgery. Two patients presented with obstructive symptoms and posted for emergency surgery. Among the two obstructed spigelian hernia cases, one had omentum and one had small intestine as the content. None of them had any strangulation. We did onlay mesh hernioplasty in both the emergency cases.

Association with menopause

POST MENOPAUSAL WOMEN:- 5 (55% of women)

In our study, five out of the nine female patients had menopause.

Comorbidity

PRESENCE OF COMORBIDITIES: - HYPERTENSION (6) , DM(1)

In our series, six patients were hypertensive and one was diabetic. All of them was on oral medication and controlled.

Size of the defect [mm]

In our study, the mean size of hernial defect was 26.3 mm with the range being 12-45 mm. This measurement is based on NCCT [ non-contrast CT] scan done in each patient preoperatively.

We carried out a retrospective case review of patients having undergone a spigelian hernia repair in our hospital in southern Rajasthan, between January 2020 and February 2024. 12 Individuals (3 males , 9 females) were identified to have been diagnosed with Spigelian hernia. The charts mentioned above have outlined the demographical characteristics of the dataset. Data collected included patient demographics, site of the hernia, comorbidities, relevant surgical and medical history, whether surgery was elective or emergent, the surgical technique used, the radiological findings and the incidence of postoperative complications and hernia recurrence.

Operation notes were reviewed and follow-up determined by the last review in a general surgical clinic or by abdominal imaging like ultrasound or computed tomography (CT).

A literature search was carried out for the terms ‘Spigelian hernia' ‘onlay mesh hernioplasty' and ‘sublay mesh hernioplasty’ was done and searched results were inculcated in our discussion to achieve protocols and further methodology lessons for ideal treatment and early diagnosis of spigelian hernia.^[1] All the review articles have been added in reference of this article giving due credit to the latest approaches of laparoscopic management for this diagnosis while concluding this article.^[8]

The clinical presentation of Spigelian hernia is often unclear, making diagnosis challenging. Patients typically report intermittent pain and a sensation of swelling in the lower abdomen. However, many individuals experience symptoms without clear clinical findings. Spigelian hernia may develop in two stages: an initial stage, often in younger patients, where the hernia is small and lacks a peritoneal component, causing intermittent pain without a palpable mass; and a later stage, where the hernia enlarges and becomes palpable.^[5,7]

Patients may sometimes have symptoms without a detectable lump, leading to a diagnosis of occult SpH. Commonly incarcerated contents include the small bowel, greater omentum, and sigmoid colon, although unusual cases have involved structures such as Meckel's diverticulum, the stomach, ovary, or urinary bladder.^[7]

In our series of spigelian hernia comprising of 12 patients over the course of four years at our instituition, we have seen female predominance [ 9 case out of 12 ]. There is increased incidence of spigelian hernia with advancing age. Mean age of patients in our series is 56.1 years with the youngest patient was of 46 years and oldest was 66. We have observed more left sided spigelian hernia than right sided one which doesnot have any statistical significance. Out of 12, two patients presented in the emergency with obstructive features and posted for emergency surgery. Spigelian hernia has increased incidence of obstruction or strangulation, and in our small series also, we have seen two cases with obstructed spigelian hernia. One of them had small intestine as the content & the other one had omentum. Neither had any features of strangulation. Majority of female patients in our series belonged to the postmenopausal group [ 5 out of 9 ]. We have observed 6 patients was hypertensive and one was diabetic but no correlation could be achieved because of small sample size. 

Role of CT in Spigelian Hernia

CT scanning is considered the gold standard for diagnosing Spigelian hernia preoperatively. It provides detailed cross-sectional images of the abdominal wall, allowing clinicians to clearly visualize the hernia defect. CT is highly effective in pinpointing the hernia’s exact location, determining the contents of the hernia sac, and identifying any associated complications, such as bowel obstruction or strangulation. With its high spatial resolution and ability to view the hernia in multiple planes, CT is reliable for diagnosing even small or hidden Spigelian hernias that might not be detectable through physical examination or other imaging methods. Preoperative non-contrast CT scan done in all patients undergoing elective surgery. Contrast CT scan done in two cases posted for emergency surgery to rule out intestinal obstruction or strangulation.

Sometimes intraoperative ultrasound (USG) is valuable during the surgical repair of Spigelian hernia, especially when the hernia defect is hard to see or feel. Intraoperative USG provides real-time imaging, assisting surgeons in locating the hernia defect accurately, assessing its size, and determining the contents of the hernia sac during surgery. This tool is particularly helpful for interparietal hernias that may be hidden between layers of the abdominal wall.

Left sided spigelian hernia

Above is the preoperative image of a female patient with left sided spigelian hernia.

Below, CT scan of the same patient showing spigelian hernia with small bowel content (white arrow).  

MANAGEMENT-

Mesh repair is the preferred treatment modality for Spigelian hernias due to its efficacy in preventing recurrence. The approach to repair can be open or laparoscopic.

Open and Laparoscopicrepair:

• Open Repair: Direct incision with mesh reinforcement; suitable for larger hernias or cases where laparoscopy is challenging.
• Laparoscopic Repair: Minimally invasive, offers reduced pain, faster recovery, better aesthetics, and thorough abdominal wall examination. (10)

Mesh Selection:

• Type: Lightweight, macroporous meshes are preferred for flexibility, lower infection risk, and better tissue integration.
• Placement Options:
• Onlay (over fascia)
• Inlay (within defect)
• Sublay ( in retromuscular plane)^[9]

• Complications of Mesh repair: Risks include infection, mesh migration, and rare cases of erosion into adjacent organs. Higher risk in contaminated fields (e.g., bowel strangulation).^[8,10]

Sublay Mesh Hernioplasty:

• Technique: Mesh is placed in preperitoneal space, reinforcing the abdominal wall from behind the defect.
• Advantages: Lower infection risk, better tissue integration, lower recurrence rates.^[10]
• Disadvantages: Technically challenging, longer recovery due to dissection.

Onlay Mesh Hernioplasty:

• Technique: Mesh is placed over the defect and secured with sutures or staples.
• Advantages: Simpler, faster, shorter operating time, lower risk of hematoma.
• Disadvantages: Higher infection and recurrence risk, as mesh is in contact with the skin.^[10]

Comparative Analysis:

• Infection: Sublay has a lower infection risk than onlay, important for elderly patients.
• Pain: Onlay may have less initial pain but risks long-term issues like mesh exposure.
• Recurrence: Sublay generally has lower recurrence, essential for long-term outcomes in elderly patients.^[10]

Patient Considerations:

• Age and Frailty: Elderly patients may benefit from sublay’s durability despite complexity.
• Previous Surgeries: Patients with multiple surgeries may benefit from sublay for better support and lower recurrence, though it is more complex.^[8]

The choice between sublay and onlay mesh hernioplasty in post-surgical elderly women depends on several factors, including the patient’s overall health, the complexity of the hernia, and the surgeon's experience. While sublay hernioplasty generally offers better long-term outcomes with lower recurrence and infection rates, onlay hernioplasty can be simpler and faster. Tailoring the approach to the individual patient’s needs and circumstances is crucial for optimizing surgical outcomes and recovery.^[9,10]

All cases in our series underwent open mesh hernioplasty though laparoscopic approach is also acceptable alternative. Sublay mesh hernioplasty done in seven cases and onlay was done in five. The decision on mesh placement [ sublay/onlay ] taken during surgery depending on location of hernia, size of defect, patients body habitus , surgeon’s choice etc. Identical lightweight polypropylene mesh was used in all cases. We have not observed major complications in our series with only one patient underwent emergency surgery developed seroma postoperatively. All were followed up for 1 year and none of them presented with recurrence.

Our experience shows that open mesh hernioplasty is an effective surgical management option in spigelian hernia.

Spigelian hernia lacks specific and consistent physical findings, thus making a delayed diagnosis a frequent occurrence. As such, a high index of clinical suspicion is required due to the potential for life-threatening complications. Our case series highlights the need for diagnosis in a certain group of post-menopausal women that present with abdominal swelling or pain abdomen and even other rare presentations which are life threatening like bowel obstruction.^[9] Early diagnosis provides enormous assistance in decided treatment plans in elective surgeries and enough time for radiological evidences like CT imaging and when imaging is inconclusive, diagnostic laparoscopy may provide almost one-hundred percent accuracy. Despite the rarity of spigelian hernia, it must be considered in the differential diagnosis of abdominal hernia due to its high risk for acute complications.^[10]

Conflict of interests – None

Author Contributions: All authors contributed substantially so that the article came into fruition. Individual contributions are as follows.

1. Parthasarathi Hota : Conceptualization, Methodology, Validation, Formal Analysis, Investigation, Resources, Writing – Review & Editing, Visualization, Supervision
2. Harleen Bawa : Software, Validation, Formal Analysis, Investigation, Resources, Data Curation, Writing – Original Draft Preparation
3. Apurva Damaraju : Conceptualization, Methodology, Validation, Formal Analysis, Investigation, Resources, Data Curation
4. Abhishek Harlalka : Investigation, Resources, Data Curation, Writing – Original Draft Preparation

Funding : None

Ethical clearance : Not required

Informed consent : Taken for each patient

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