Parainguinal or Spigelian hernia: a clinically important distinction

Parainguinal hernias (PHs) are an uncommon but under-recognised subtype of lateral abdominal wall hernia, located near the ASIS, distinct from the deep inguinal ring and at or just below the interspinous plane. They are frequently misclassified as Spigelian hernias (SHs) or inguinal hernias due to overlapping features. This study aimed to define the clinical characteristics, diagnostic accuracy, operative management, and long-term outcomes of patients with PHs compared with SHs.

A retrospective cohort study of all adult patients undergoing mesh repair for PHs or SHs under the care of a single surgeon between 2002 and 2025 was undertaken. Clinical, radiological, and operative findings were analysed alongside complications and long-term outcomes. Pain outcomes were assessed using Cunningham's criteria.

Forty-five patients underwent surgical repair: 40 with PHs and five with SHs (41 PH and 5 SH repairs). PH patients were older than SH patients (median 72 vs. 58 years, p = 0.036). PHs were more often left-sided (63%) and commonly misdiagnosed preoperatively as SHs (51%). Clinical diagnosis of PHs showed moderate sensitivity (56%) but high positive predictive value (96%), while CT and ultrasound performed poorly (sensitivities 6-15%). SHs were more reliably identified clinically (80%) but had low predictive values. PHs were repaired predominantly with open or laparoscopy-assisted mesh repair (95%), while SHs were repaired laparoscopically in most cases (80%). Complications were rare (seroma 4%, TIA 2%). At a median follow-up of 8.8 years (IQR 2.4-12.5), 87% of patients reported no pain, 13% had mild symptoms, and there were two recurrences (4%).

PHs are more common than SHs, and recognition as a separate subtype is warranted to improve diagnostic accuracy and guide tailored management. In this series, open extraperitoneal mesh repair of PHs was associated with low complication rates, and excellent long-term patient outcomes.