A healthy 72-year-old man was referred to the urology clinic for findings of a pelvic mass seen on a CT scan. He had a 2-year history of right-sided back and pelvic pain described as constant, nonradiating, worse with activity, and better when leaning forward. Consultations with neurosurgery and orthopedic surgery, as well as multiple back injections, were unable to help his pain. Notably, the patient underwent a removal and replacement of a penile prosthesis in 2017 due to device malfunction. A pelvic MRI revealed a hypointense ovoid mass on T1- and T2-weighted imaging just to the right of the rectum and posterior to the urinary bladder, measuring 2.9 × 3.2 × 4.8 cm in size (Figure 1, A and B). CT scans of the abdomen and pelvis demonstrated the mass was further characterized as peripherally dense with an ovoid central calcification measuring 8 × 10 × 15 mm. A second calcified structure adjacent to this mass was also identified (Figure 1, C-E). Radiology noted the mass suggested a foreign body possibly related to his penile prosthesis. Following discussion with our radiology and surgery colleagues, it was decided that urology should proceed with robotic exploration and extirpation given the symptomatology and concern for a retained inflatable penile prosthesis reservoir or other component.

The patient was taken to the operating room and positioned supine with port placement schemata similar to robotic prostatectomy. Once inside the abdomen, his active reservoir appeared to be in appropriate positioning in the left hemipelvis. He did have notable colonic diverticulosis and associated attachments that were released. Following colon mobilization, a large egg-like mass and a similar but smaller calcified stone were visualized in the right posterior cul-de-sac between the bladder and rectum. They were easily mobilized with few attachments and placed into an endo catch bag. No other foreign bodies or abnormalities were noted, the robot was undocked, and the specimens were retrieved. Total operative time was 25 minutes. The patient was discharged home from the postanesthesia care unit.

On gross examination (Figure 2, A and B), the larger 4.7 × 3.5 × 3.0–cm specimen did appear “egg-like” with a white-tan smooth gelatinous-feeling outer coating, yellow-tan inner component, and a calcified core measuring 2.3 × 1.3 × 1.0 cm. The second specimen was a 1.2 × 0.7 × 0.6–cm mass of calcified tissue. Final pathologic diagnosis was consistent with an acellular hyalinized nodule and focal microcalcification. Upon review of the literature, this was most consistent with a peritoneal loose body (PLB) or peritoneal “egg.”

The incidence of PLBs or peritoneal “eggs” is not well known,¹ most often being detected incidentally on imaging or intraoperatively or at the time of autopsy.² These were first described in the early 1700s by Littre and, consistent with our patient’s observed diverticulosis, are most frequently believed to be related to detached appendiceal epiploicae that undergo subsequent calcification and saponification with protein absorption over years. They were even described in a case series of appendiceal epiploicae torsion/inflammation in 1917.^1-4 Alternatively, infarction of other tissue such as adnexa, omentum, or pancreatic fat has been reported as an etiology.⁴ Most often, PLBs are identified in men 50 to 70 years old and can be > 5 cm in size (“giant” PLB).^1,4 PLBs are typically mobile, and serial imaging can demonstrate this.⁵ Similar to our case, PLBs will usually look like a boiled egg or a large white pearl and are usually hypointense on T1- and T2-weighted images without blood flow.^2,5 On a CT scan, they will often demonstrate central calcification.^2,5 PLBs are usually asymptomatic and do not necessarily need to be treated; however, they may be associated with pain or discomfort and warrant removal, such as in our patient.⁴ In addition to pain, patients can present with symptoms of mass effect such as intestinal obstruction or urinary symptoms (eg, retention, frequency, dysuria).^2,4,6

Following surgical removal, our patient immediately felt much better and had complete alleviation of his pelvic and back pain. No further workup or surveillance is indicated in these cases.⁴