In female patients, preperitoneal fat protrusion through the deep inguinal ring along the round ligament is a rare but clinically significant entity. While spermatic cord lipomas in males are well recognized found in up to 20-70% of inguinal hernia repairs and often considered protrusions of preperitoneal fat rather than true neoplasms, equivalent lesions along the round ligament in females are much less frequent.

Lilly and Arregui’s retrospective review of 280 hernia repairs identified round ligament “lipomas” in approximately 36% of female cases, though only 1.4-12.5% in other studies, underscoring variability and diagnostic under-recognition. Although these lesions can present with groin pain or swelling, they frequently occur without an associated hernial sac or bowel contents, making preoperative differentiation from true hernias or soft-tissue tumors challenging [1].

Imaging modalities such as ultrasound, CT, or MRI may reveal fat-density masses within the inguinal canal but often cannot distinguish between encapsulated lipomas, preperitoneal fat hernias, or round ligament leiomyomas [3,4]. As a result, definitive diagnosis typically occurs during surgical exploration, where continuity with fat in the preperitoneal space is recognized and intraoperative reduction or excision is performed.

Understanding this anatomical variant is important, because failure to address extraperitoneal fat protrusion, even in the absence of a sac may lead to persistence of symptoms or perceived hernia recurrence. Current literature supports that surgical management with reduction or excision of fat plus posterior wall reinforcement, analogous to routine hernia repair, provides symptom resolution and prevents misdiagnosis [8].

17-year-old girl presented to outpatient department with complaints of swelling at left inguinal region for 1 year. Swelling was progressively increasing in size and was painless. There were no associated gastrointestinal complaints, urinary issues, weight loss, or fever. On physical examination, a soft, non-tender, irreducible mass approximately 6x4 cm was palpable at the left inguinal region. There was no cough impulse, and the swelling was slightly extended into the left labia majora. No evidence of lymphadenopathy or overlying skin changes.

Her routine blood investigations were within normal limits. On ultrasound examination revealed a hyperechoic, fat-density lesion adjacent to the round ligament within the inguinal canal. No peritoneal sac, bowel, lymph node enlargement, or vascular flow was visualized.

On basis of clinical and radiological findings patients was planned for surgery. Under general anaesthesia, an oblique inguinal incision was made over the swelling. Intraoperatively, preperitoneal fat was observed protruding through the deep inguinal ring and tracking along the round ligament in continuity with the extraperitoneal fat, with no encapsulated lipoma or hernia sac. Protruded fat was excised and repair of deep ring with posterior wall repair was done. Histopathology examination revealed mature adipose tissue continuous with preperitoneal fat. Postoperative course was uneventful. Patient was followed up after 7 days, at 1 month and at 3 moths, no recurrence was noted.

Figure 1: Inguinal mass mimicking as a lipoma.

Figure 2: Intraoperative image showing preperitoneal fat protrusion.

Preperitoneal fat protrusion along the round ligament is an uncommon clinical finding that can mimic more common groin masses, such as lipomas or inguinal hernias [1]. This rarity often poses a diagnostic challenge, particularly in adolescents, where differential diagnoses for groin masses include hernias, lipomas, lymphadenopathy, and rarely, benign or malignant tumours.

The round ligament of the uterus, a fibromuscular band containing vessels and nerves, traverses the inguinal canal and attaches to the labia majora [2]. Fat tissue along the round ligament can sometimes herniate or protrude through the inguinal canal, mimicking a lipomatous mass. In paediatric and adolescent populations, this presentation is particularly rare and may easily be mistaken for more common pathologies [4].

Imaging modalities such as ultrasound and MRI are critical for accurate diagnosis. Ultrasound may show a hyperechoic mass along the inguinal canal, but it often lacks specificity [4]. MRI can better characterize the fatty nature of the lesion, its exact anatomical location, and relationship to surrounding structures, helping to differentiate between a benign fat protrusion and other pathological masses such as lipomas, lymphadenopathy, or hernias containing omental fat [3].

In this case, the clinical and radiological findings initially suggested a lipomatous mass. However, intraoperative findings confirmed preperitoneal fat protrusion along the round ligament without an actual hernial sac. Awareness of this entity is essential to avoid unnecessary extensive surgical dissection or radical procedures.

The management approach typically involves excision of the protruding fat mass if symptomatic or if there is diagnostic uncertainty. Conservative management may be considered if the lesion is asymptomatic and clearly identified on imaging, but surgical exploration may be warranted in cases mimicking hernias or tumors [5,6].

This case highlights the importance of considering preperitoneal fat protrusion along the round ligament in the differential diagnosis of groin masses in adolescent females. It can closely mimic lipomatous tumors or inguinal hernias clinically and radiologically, leading to potential misdiagnosis. Awareness of this entity, combined with careful imaging and intraoperative assessment, can help avoid unnecessary extensive surgery. Surgical excision is curative and usually indicated when symptomatic or when diagnosis remains uncertain. Reporting such rare cases contributes to better understanding and management of unusual groin masses in paediatric and adolescent patients.

Conflicts of Interest

There are no conflicts of interest.

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