Giant peritoneal mouse: A rare case presenting with lower urinary tract symptoms.

Peritoneal loose bodies called 'peritoneal mice' are rare entities that can grow to large sizes and produce lower urinary tract symptoms due to a mass effect. We describe a case that was managed with laparoscopic removal of the mass with complete resolution of symptoms.

INTRODUCTION

Peritoneal loose bodies or peritoneal mice are usually asymptomatic and detected incidentally on imaging or dring surgery.[1] These masses vary in size ranging from 0.5 to 2.5 cm in diameter. Giant peritoneal mice (>5 cm) may be associated with symptoms due to a mass effect. A peritoneal mouse is supposed to be formed due to detached epiploic appendages that gradually become fibrosed and take a form of mass. Another theory suggests that large loose bodies can be formed by the accumulation of peritoneal serum in the appendices epiploicae.[2] We describe a giant peritoneal mouse which presented with overactive bladder symptoms.

CASE REPORT

A 50-year-old male presented with dull-aching pain in the lower abdomen with increased frequency and urgency of urine. He had normal prostate on digital rectal examination and ultrasound. Ultrasound KUB showed a mass measuring 5 cm × 4 cm behind the bladder. Magnetic resonance imaging (MRI) abdomen revealed a mass of 5 cm × 4 cm in the rectovesical pouch [Figure 1]. The mass was well circumscribed and nonenhancing. It showed low intensity on both T1- and T2-weighted (T1W and T2W) images. MRI signal was similar to that of the muscle with central high-intensity area on T1W images. Laparoscopy revealed a free-floating egg-shaped, glisxtening white mass in the rectovesical pouch [Figure 2]. The mass was not attached to any pelvic structure and it was removed in an endocatch bag. On sectioning, it had a classic ‘boiled-egg’ appearance. The white part was smooth and soft in consistency, while the central yellow part was slightly firm. The surfaces were smooth. Histopathology revealed laminated strands of a fibrinoid substance with a large amount of proteinaceous material in the peripheral white part and saponified fat with calcification in the central yellow part. His urinary symptoms and pain subsided after removal of the mass.

Figure 1

Magnetic resonance imaging pelvis (sagittal view, T1-weighted image) showing a mass (5 cm × 4 cm) in the rectovesical pouch

Figure 2

Laparoscopy revealing a glistening white, rubbery, free-floating mass in the pelvis

DISCUSSION

Peritoneal mouse presenting with symptoms of overactive bladder is very rare. Only a few cases have been reported of peritoneal mice presenting with lower urinary tract symptoms. One case has been reported of urinary retention caused by a giant peritoneal mouse.[3] Mechanical compression of the bladder neck area by the mass produced irritative and obstructive urinary symptoms. The patient fully recovered after removal of the peritoneal mouse. Peritoneal mice should be distinguished from other lesions such as leiomyomas, fibromata, desmoid tumors, teratomas, metastatic lesions of ovarian cancer, calcification of lymph nodes, and mesenteric cysts. Mesenteric cyst, calcified lymph nodes, and peritoneal mice do not enhance on computed tomographic scan.[4]

CONCLUSION

Giant peritoneal mice presenting with lower urinary tract symptoms are very rare entities. Imaging is often inconclusive. Laparoscopic removal of the mass is recommended to alleviate the symptoms and to rule out any malignancy.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.