A scrotal egg – Peritoneal loose body in the inguinal hernia

A 54-year-old man presented with complaints of gradually increasing swelling in the right inguinal region for one year. There was no pain. The swelling was non-reducible with no signs of bowel obstruction on clinical examination. A routine preoperative ultrasound was performed.

Ultrasound of the inguinoscrotal region shows herniation of bowel loops and omentum into the right scrotal sac with normal bowel vascularity. There was a well-defined round lamellated hypoechoic lesion with central calcification in the tunica vaginalis sac adjacent to the bowel loops measuring approximately 2.8 x 2.4 cm (Figure 1a). There was no vascularity on colour Doppler (Figure 1b). Both the testes were separate from the lesion. A radiograph of the pelvis (Figure 2) showed a soft tissue swelling in the scrotal region with lucencies suggestive of a hernia with bowel loops as the content. There was a well-defined abnormal round calcification within the soft tissue on the left side. An unenhanced computed tomography of the pelvis confirmed the findings on ultrasound and the radiograph. The lesion was isodense to the bowel with central calcification (Figures 3a and 3b). The lesion was removed surgically with a reduction of the hernia followed by hernioplasty (Figure 4).

Peritoneal loose bodies or peritoneal mice are necrotic tissue with central calcification found within the peritoneal cavity [1]. They occur secondary to torsion of the epiploic appendage with necrosis of its pedicle and detachment. There is sequential saponification and calcification. They grow in size due to continuous protein deposition derived from the peritoneal serum [2]. They range in size from tiny lesions (0.5 to 2.5 cm) to large masses (5–10 cm) [1]. They may even occur in patients with pancreatitis (mesenteric fat necrosis). They are more common in men (ratio of 18:4) and seen in the age group of 50–70 years [2]. They are usually solitary; however, they may be multiple in a few cases [3].

Due to the insidious nature of its pathogenesis, they are usually asymptomatic and detected incidentally on imaging or during laparoscopy/laparotomy. When symptomatic, the usual presentation is chronic vague abdominal pain, and when large enough, they produce symptoms due to extrinsic compression over the bladder (increased frequency of micturition) and bowel (obstruction).

They are mobile and frequently seen in the dependent region of the abdomen, such as the pelvis, pouch of Douglas, and rectovesical pouch [4]. Rarely, they may herniate along the abdominal contents forming a content of hernial sac in the inguinal region [1].

Due to the central calcification, they can be detected on radiographs. On ultrasound, these lesions are homogeneously hypoechoic with a lamellated appearance and a central calcification. There is no vascularity on colour Doppler. On computed tomography (CT) there is soft tissue attenuation (isodense to the muscle) with a central calcification. On magnetic resonance imaging (MRI), it is hypointense on both T1 and T2-weighted sequences [5]. The central area might be hyperintense on T1-weighted sequences due to the proteinaceous content [4]. There is no enhancement that helps in ruling out other differentials, such as leiomyoma and teratoma [6]. A change in position can be demonstrated on dynamic ultrasound with a change in patient decubitus. Similarly, on CT and MRI, the location of the lesion varies on imaging in the prone position [4].

The common differentials include benign pathologies such as leiomyoma, teratoma, adnexal pathologies, a foreign body with adjacent granulation tissue, and a calcified fibrous pseudotumour.

At surgery, they are free-floating with a smooth egg-shaped white hard glistening appearance [3].

They are usually managed conservatively when detected incidentally; however, they are removed surgically when detected incidentally during surgery or when they cause symptoms.