A Peritoneal inclusion cyst is a benign cyst lined by peritoneal mesothelium. They can occur at any location of the peritoneum, in continuity with the surface of either parietal or visceral peritoneum. Higher incidence is found in females in reproductive age group with a history of multiple abdominal surgeries. Most are asymptomatic and are incidentally found on cross-sectional imaging for other indications3. If symptomatic, it may be drained under imaging control, debulked or excised. They have low potential for malignant transformation but high recurrence rates.

CASE PRESENTATION: A 40-year-old female with a history of multiple surgeries presented with complaints of lower abdominal pain and distension, straining while defecation and difficulty in micturition for six months. She gave past surgical history of appendicectomy and two lower segment caesarean section respectively. She also underwent total abdominal hysterectomy with right salpingo-oophorectomy for abnormal uterine bleeding due to sub serosal uterine fibroid two years prior to presentation. She had no history of discharge per vaginum and dyspareunia. On examination two transverse and one vertical surgical scars were seen over the abdomen. Abdomen was mildly distended and tenderness was present in right Iliac fossa, left Iliac fossa and suprapubic region. On per rectal examination, a tender boggy mass was felt through the anterior wall of rectum. Magnetic resonance imaging of (MRI) Pelvis showed a large well defined thin walled abdominopelvic cystic lesion measuring about 9.1 x 20 x 18.5 cm with a volume of 1600cc with few internal septations, extending superiorly till L2 vertebral level, inferiorly compressing the urinary bladder with maintained fat plane and displacing bowel loops peripherally. Left ovary appearerd compressed measuring 2.7 x 1.5 cm and seen at the periphery of the cystic lesion.( Fig-1 ) FIG:1 MRI pelvis showing the intraperitoneal cystic lesion Exploratory laparotomy revealed a 15 x 12 cm thin walled cyst extending from the pelvis into the retroperitoneum with sigmoid mesentery splayed over the cyst. Left ovary was noted within the cyst. Excision of cyst along with the ovary was carried out. Cystic fluid was sent for cytology which was negative for malignant cells. Cut surface of the ovary showed dense stroma with peripheral cystic areas and histopathological examination of excised cyst wall with left ovary was consistent with peritoneal inclusion cyst. ( Fig-5 and 6 ) FIG-2: Axial section CT image showing the intraperitoneal cystic lesion ( white arrow) FIG-3: Sagittal section CT image showing the intraperitoneal cystic lesion in abdomen and pelvis FIG-4: Coronal section CT image showing the intraperitoneal cystic lesion in abdomen and pelvis FIG-5: The above figure showing the excised specimen of cyst wall with ovary FIG-6: Histopathological picture showing flattened mesothelial cells with bland nuclei

Peritoneal fluid is constantly secreted and absorbed and when there is excess production or reduced absorption fluid accumulates resulting in ascites1.Peritoneal inclusion cysts [PIC] are reactive, fluid filled lesions of peritoneal lining, with a higher incidence in female population, especially in third to fourth decade of life and with previous multiple abdominal surgeries. The pathology predominantly involves peritoneal surfaces and pelvic visceral organs such as uterus, fallopian tubes and ovaries. During the reproductive years, fluid produced by the ovaries is normally absorbed by the peritoneum. When the integrity of the peritoneum is disrupted as a result of surgery, trauma, inflammation or endometriosis the peritoneum has decreased ability to absorb fluid. In addition, postsurgical adhesions can trap ovarian fluid that is no longer being absorbed by a disrupted peritoneum, producing a complex cystic pelvic mass. Peritoneal inclusion cysts are thus simple or complex cystic adnexal collections consisting with a normal ovary entrapped in fluid filled adhesions as seen in this patient. Pathologically, peritoneal inclusion cysts are pseudocysts and are typically lined by hyperplastic mesothelial cells proliferating within inflamed fibrous granulation tissue walls. Often the ovary is connected to peritoneum by a pedicle and the trapped ovary which produces fluid physiologically, is mostly responsible for the fluid within these cysts; the surrounding inflammation may cause an exudate, resulting in persistence and growth of PIC.3 Differential diagnoses include paraovarian cysts, non-pancreatic pseudocyst, hydrosalpinx and low-grade cystic mesothelioma, gastrointestinal inflammation or pelvic inflammation2. But in regard to the above case history, the most likely hypothesis behind her PIC development is peritoneal disruption due to multiple previous surgeries leading to impaired fluid absorption and the presence of functioning ovary together causing formation of a cyst. Various treatment options are offered to treat peritoneal inclusion cysts such as hormonal management, image-guided aspiration, image-guided sclerotherapy, potassium-titanyl-phosphate laser ablation and surgical excision. Hormonal treatment has been shown to decrease or atleast stabilize the size of the cysts and to control symptoms. Oral contraceptives, gonadotropin releasing hormone agonists, Tamoxifen and megestrol have been used as hormonal therapy.4 Ablative procedures fail to recognize the depth of invasion, resulting in significant risk of thermal damage to underlying structures and a greater amount of necrotic tissue left behind. There is also a greater inflammatory reaction and increased risk of adhesions and pain.5 Thus elective excisional surgery such as in our case is usually the most common treatment option which can confirm histopathology and rule out atypia or malignancy.

In conclusion, peritoneal inclusion cyst is a rare entity with only less than 150 cases reported in literature.6 They are reactive cysts with a low rate of malignant transformation but with a high risk of recurrence. Currently, mainstay of management is surgical resection as it is curative and confirms the pathology.

1. O'Connell, P.R., McCaskie, A.W., & Williams, N.S. (Eds.). (2018). Bailey & Love's Short Practice of Surgery, 27th Edition (27th ed.). CRC Press. https://doi.org/10.1201/9781315111087 2. AlTamimi JO, Alzahrani EA, Fallatah A, Alhakami LA, Bokhari BE. Peritoneal Inclusion Cyst in a Young Patient With a Long History of Abdominal Surgeries: A Case Report. Cureus. 2023 Feb 20;15(2):e35230. doi: 10.7759/cureus.35230. PMID: 36968891; PMCID: PMC10032648. 3. Goldfisher, Rachelle, Awal, Divya, Amodio, John, Peritoneal Inclusion Cysts in Female Children: Pathogenesis, Treatment, and Multimodality Imaging Review, Case Reports in Radiology, 2014, 427427,5pages, 2014. https://doi.org/10.1155/2014/427427 4. Peritoneal inclusion cysts treated with a levonorgestrel-releasing intrauterine system: A case report Hanako Tamai, Masato Kinugasa, Miho Nishio, Mayu Miyake Department of Obstetrics and Gynecology, Amagasaki Co-op 5. Hospital, 12-16-1 Minamimukonoso, Amagasaki 661-0033, Japan. 6. Excisional versus ablative surgery for peritoneal endometriosis Tommaso Bignardi Su‐Yen Khong Alan Lam 7. https://doi.org/10.1002/14651858.CD008979 8. Imaging appearance of benign multicystic peritoneal mesothelioma: a case report and review of the literature 9. Varun Mehta, Varun Chowdhary, Richa Sharma, Jennifer 10. S. Golia Pernicka, Department of Radiology, Staten Island University Hospital, Northwell Health, New York City, NY 10305