Peritoneal inclusion cysts

Peritoneal inclusion cysts (PICs) are uncommon mesothelium-lined, multiloculated peritoneal cystic lesions that predominantly occur in female individuals of reproductive age. They are generally considered a reactive process related to peritoneal irritation and inflammation, commonly in the setting of prior pelvic surgery, pelvic inflammatory disease, or endometriosis. Patients may be asymptomatic or present with chronic pelvic pain, abdominal distention, or a palpable mass. Diagnosis is suggested by clinical history and imaging, with ultrasound characteristically showing multiseptated cystic lesions and, when pelvic, an entrapped ovary (spider-in-web sign). MRI provides optimal anatomic delineation. Management is symptom-directed; surveillance is recommended for asymptomatic cysts, while symptomatic cysts may require hormonal therapy, image-guided drainage, and/or surgical excision. Recurrence is common, but malignant transformation is rare.

A peritoneal inclusion cyst is a mesothelium-lined cystic lesion of the peritoneum. ^[1][2]

• Can occur in the pelvis, upper abdomen, and/or retroperitoneum
• Rarely occur on the surface of abdominal or pelvic organs (e.g., kidney, spleen, bladder)

• Predominantly affects female individuals of reproductive age
• Average age at diagnosis: ∼ 32 years ^[1]
• Rare in children and men

Epidemiological data refers to the US, unless otherwise specified.

• Thought to arise from reactive mesothelial proliferation in response to chronic pelvic irritation or adhesions.
• Associated predisposing conditions and risk factors include:
  • Previous abdominal or pelvic surgery
  • Pelvic inflammatory disease (PID)
  • Endometriosis
  • Inflammatory bowel disease ^[3]

• Often asymptomatic and found incidentally
• Symptoms may include:
  • Chronic, vague lower abdominal or pelvic pain
  • Abdominal distention or fullness
  • Palpable abdominal or pelvic mass
  • Gastrointestinal symptoms (e.g., nausea, vomiting, constipation)
  • Urinary symptoms (e.g., dysuria, retention, frequency, hesitancy)
  • Dyspareunia
  • Weight loss

PIC should be considered in premenopausal women with a history of pelvic adhesions from prior surgery, endometriosis, or PID.

Imaging ^[1][2]

Abdominal and/or transvaginal ultrasound

• First-line study for detecting pelvic masses
• Typical findings
  • Multiloculated anechoic cystic lesions with internal septations
  • No detectable vascular flow on color Doppler imaging
  • Spider-in-web appearance: A normal ovary may be visible entrapped within the cyst.

CT abdomen and pelvis

• Shows the full extent of the cysts
• Typical findings: multiloculated, thin-walled cystic lesion without calcification

MRI

• Best imaging modality to show the relationship of the mass to pelvic structures
• Typical findings
  • Cysts have high signal on T2-weighted images with low T1 signal.
  • Hemorrhagic content may produce high T1 signal.
  • Septations: commonly enhanced

Laboratory studies ^[1][2]

• CA 19-9 and CA 125 are typically obtained to evaluate for malignancy.
• Levels are usually normal but may be elevated (especially CA 125 in patients with associated endometriosis).

Biopsy ^[1][2]

• Required for definitive diagnosis
• Typically obtained via laparoscopy
• Histopathology
  • Cyst lining: single layer of flat to cuboidal mesothelial epithelium
  • Cyst wall: formed by a thin fibrovascular stromal layer

• Ovarian cystadenoma
• Ovarian cystadenocarcinoma
• Brenner tumor
• Cystic teratoma
• Endometriosis
• Lymphangioma
• Mesenteric cyst
• Cystic adenomatoid tumor
• Pseudomyxoma peritonei
• Malignant mesothelioma

The differential diagnoses listed here are not exhaustive.

General principles ^[1]

• Goal: symptomatic relief rather than complete eradication
• Recurrence is common (up to 50%). ^[1]
• Treatment is individualized.
• Conservative management (i.e., surveillance via serial imaging) is indicated for asymptomatic patients.

Pharmacological treatment ^[1]

• Hormonal treatments may be used to suppress ovarian fluid formation.
• Agents
  • Oral contraceptives
  • Gonadotropin-releasing hormone agonists
  • Antiestrogenic drugs (e.g., tamoxifen)

Interventional treatment ^[1]

• Image-guided drainage or aspiration for symptomatic relief
• Sclerotherapy after drainage may improve success rates and reduce recurrence.
• Surgical resection: treatment of choice for symptom relief and to prevent recurrence
  • Laparoscopy: preferred approach for investigation
  • Laparotomy: preferred approach if malignancy is suspected
  • Cytoreductive surgery with extended peritonecomy and hyperthermic intraperitoneal chemotherapy
    • Considered for recurrent disease or if there is suspicion of malignancy
    • A more aggressive surgical approach than surgical resection alone

• Infertility
• Malignant transformation (rare)

We list the most important complications. The selection is not exhaustive.