Iatrogenic semilunar line hernias: challenging cases and varying treatment options

Abstract

Introduction

The semilunar line (linea semilunaris or Spigelian line) is formed by the fusion of the internal oblique aponeurosis with the rectus abdominis aponeuroses. Neurovascular bundles supplying motor innervation to the rectus abdominis travel between the internal oblique and transversus abdominis and penetrate the posterior rectus sheath just medial to the semilunar line. Surgical incisions through or across this line may result in rectus abdominis denervation.

Semilunar line incisional hernias should not be confused with Spigelian hernias, which are primary hernias occurring at the confluence of the semilunar and arcuate lines [1–4]. In contrast, semilunar line hernias arise after trauma, either blunt or penetrating (including surgical incisions). The management of these hernias can be challenging and should be tailored to each unique situation. We describe three case reports of semilunar line hernias managed using three different surgical techniques.

This study was approved by the UTHealth Houston Committee for the Protection of Human Subjects under HSC-MS-24-0936.

Case 1

A 68-year-old man [body mass index (BMI) 29] with a history of invasive bladder cancer treated with pelvic radiation and radical cystectomy with ileal conduit 3 years earlier presented with a ureteral stricture at the urostomy and a parastomal hernia. The hernia was asymptomatic and reducible, but the ureteral stricture required surgery. Computed tomography (CT) showed a right-sided urostomy at the semilunar line with a 4 cm parastomal hernia containing small bowel (Fig. 1a). The bowel herniated under the external oblique without retraction of deeper muscle layers or rectus denervation.

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A combined case was planned with urology for ureter reimplantation and hernia repair. Because the hernia was asymptomatic and ureteral length limited urostomy relocation, herniorrhaphy was performed without re-siting the stoma. After open uretero-enteric revision, we performed open parastomal hernia repair with right transversus abdominis release, re-approximation of the internal and external obliques to the anterior rectus sheath, and placement of 15 × 20 cm GORE® SYNECOR mesh in the retrorectus space. A 3 cm keyhole accommodated the ostomy, and the mesh extended well past the ostomy laterally. The patient was discharged on postoperative day 7 and had no recurrence at 3 weeks.

Case 2

A 77-year-old woman (BMI 22) with prior hysterectomy, pelvic prolapse, diverticulitis, and partial colectomy with ileostomy (4 years earlier) and reversal (3 years earlier) presented with a reducible hernia at the former ileostomy site. CT showed disruption of the right semilunar line with 4 cm muscle separation and rectus denervation medial to the defect (Fig. 1b). Given her age and possible future abdominal surgery for pelvic organ prolapse, we chose open primary repair without mesh.

After preoperative quadratus lumborum blocks, we performed myofascial release of the right posterior rectus fascia and transversus abdominis fascia/muscle to recreate the semilunar line. The posterior layer (peritoneum and posterior rectus sheath medially; peritoneum and transversalis fascia laterally) was closed with running 2–0 PDS. The anterior layer (anterior rectus sheath medially; internal and external oblique fascia laterally) was closed with #2 Duramesh®. She was discharged the same day and had no recurrence at 2 months.

Case 3

A 55-year-old woman (BMI 54) with gastroesophageal reflux disease, gastroparesis, non-alcoholic fatty liver disease, prior laparoscopic gastric band and subsequent sleeve gastrectomy presented with a large ventral incisional hernia. CT showed disruption of the right semilunar line, loss of domain with duodenum, small bowel, and colon in the hernia sac, and rectus denervation (Fig. 1c). After multidisciplinary planning, we staged her repair with a duodenal switch. Sixteen days before surgery, we placed an intraperitoneal drain for progressive pneumoperitoneum and injected botulinum toxin A into the right abdominal wall muscles.

At surgery, robotic adhesiolysis was converted to laparotomy due to inability to safely reduce contents. After over an hour of lysis, we used a transverse incision over the hernia to reduce the contents. Bariatric surgery completed the biliopancreatic diversion with duodenal switch. We denervated the right rectus muscle below the umbilicus; therefore, we bridged the defect with Ovitex 2S® mesh (37 × 23 cm), securing it medially to the left anterior rectus fascia and laterally to healthy fascia. The cranial midline was closed with #2 Duramesh®. She was discharged on postoperative day 7 without complications and remained recurrence-free at 3 months.

These cases highlight iatrogenic semilunar line hernias, an under-reported entity. Their rarity may reflect lack of recognition in addition to infrequency, and literature on the subject is sparse.

Disruption of the semilunar line can occur during surgery with lateral incisions and may denervate the rectus abdominis [1, 2, 5]. Inadvertent injury can also occur during transversus abdominis release [6]. Repair is challenging because fascia overlying denervated muscle has less tensile strength than fascia over healthy muscle [7, 8]. This series describes three closure techniques tailored to presentation:

1. Fascial closure with sublay mesh reinforcement – Used in Case 1, this approach reapproximates native fascia and reinforces with sublay mesh. Larger defects may require transversus abdominis release. Recurrence rates for parastomal hernia repair (without semilunar involvement) range from 27% to 50% [9], but outcomes for semilunar line involvement are unknown. These repairs require mesh to extend lateral to the semilunar line, often necessitating a transversus abdominis or preperitoneal approach.

2. Layer-by-layer closure – Used in Case 2, this closes each fascial layer to recreate the semilunar line. Although durability may be less than with mesh, it can minimize physiologic stress and avoid extensive adhesiolysis, which is beneficial in frail patients or those likely to need future abdominal surgery.

3. Bridging repair for staged approach – Used in Case 3 for a giant hernia with significant denervation. Botox and progressive pneumoperitoneum improved domain preoperatively, consistent with van Rooijen et al.’s findings on their utility in giant ventral hernias [10]. Bridging mesh served as temporary support with plans for formal repair after weight loss and optimization.

These cases underscore the need for individualized approaches to semilunar line hernias. Larger studies and long-term follow-up are needed to define optimal management and outcomes.

Conflicts of interest

None declared.

Funding

None declared.

References