Pseudomyxoma peritonei (PMP) is a rare clinical condition characterized by dissemination of mucin from appendiceal mucinous neoplasms (usually LAMN) into the peritoneal cavity. Mucinous implants accumulate on peritoneal surfaces, omentum, and organ surfaces. Also known as 'jelly belly.' In advanced stages, gelatinous mucinous material fills the abdominal cavity. Treatment is a combination of cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC).
Age Range
40-75
Peak Age
55
Gender
Equal
Prevalence
Rare
PMP begins with dissemination of mucin from appendiceal mucinous neoplasm (usually LAMN) through the appendiceal wall into the peritoneal cavity. Mucin follows peritoneal fluid circulation and accumulates in specific anatomical areas through redistribution phenomenon — particularly the right subdiaphragmatic space, pouch of Douglas, greater omentum, and splenic hilum (redistribution phenomenon). Due to gravity and peritoneal fluid movement, mucin forms implants on peritoneal surfaces and organ capsules. These implants do not invade organ parenchyma (in low-grade form) but cause extrinsic compression creating scalloped (garland) appearance — particularly prominent on the liver capsule and splenic surface. Omental caking results from infiltration and solidification of the omentum by mucinous implants. In advanced stages, mucinous material can fill the entire abdominal cavity and lead to bowel obstruction.
Garland-shaped scalloped indentations on liver and spleen capsules from extrinsic compression by mucinous implants. Extrinsic compression without organ parenchymal invasion is specific to PMP and a critical finding in differentiating from peritoneal carcinomatosis.
Widespread, low-density (0-20 HU) mucinous collections in the peritoneal cavity. Should not be confused with simple ascites — mucinous implants are localized, septated, and associated with scalloped organ surfaces. Densities are near-water but may not be homogeneous.
Report Sentence
Widespread, low-density mucinous collections are observed in the peritoneal cavity, compatible with pseudomyxoma peritonei.
Scalloped (garland) appearance of the liver capsule due to extrinsic compression by mucinous implants. Liver parenchyma is not invaded — compression is only at the capsular level. This finding is characteristic of PMP and important in differentiating from peritoneal carcinomatosis.
Report Sentence
Scalloped (garland) appearance of the liver capsule due to mucinous implant compression is observed, compatible with pseudomyxoma peritonei.
Greater omentum is infiltrated by mucinous implants, becoming thickened and mass-like (omental caking). Thin septations and peripheral enhancement may be seen within low-density mucinous material.
Report Sentence
The greater omentum is thickened with mucinous infiltration demonstrating omental caking.
Primary mucinous neoplasm/mucocele of the appendix — the source of PMP. Appears as dilated, cystic appendix or mass at the cecal base. Mural calcification may accompany.
Report Sentence
A cystic lesion compatible with primary mucinous neoplasm is observed in the appendix, considered the source of peritoneal mucinous dissemination.
Widespread high signal intensity mucinous collections in the peritoneal cavity on T2-weighted sequences. MRI is superior to CT for detailed characterization of mucinous implants — particularly better at showing solid component, septation, and organ surface relationship.
Report Sentence
Widespread high signal intensity mucinous collections are observed in the peritoneal cavity on T2-weighted sequences, compatible with pseudomyxoma peritonei.
Scalloped appearance of the spleen capsule due to extrinsic compression by mucinous implants. Splenic hilum and lower pole are commonly affected areas. Splenic parenchyma is not invaded.
Report Sentence
Scalloped appearance of the spleen capsule is observed due to mucinous implant compression.
Criteria
Acellular or minimally cellular mucinous implants. Cellular atypia is low-grade. Usually originates from LAMN.
Distinct Features
Low-density collections on CT, no solid component, scalloped organ surfaces. 10-year survival with CRS+HIPEC >80%. Slow progression.
Criteria
Cell-rich mucinous implants. High-grade cytologic atypia and/or signet-ring cells. May originate from mucinous adenocarcinoma.
Distinct Features
Enhancing solid components, nodular peritoneal thickening, lymphadenopathy may accompany on CT. 10-year survival with CRS+HIPEC ~20%. Aggressive course.
Distinguishing Feature
LAMN is confined to the appendix — no peritoneal mucinous implants. PMP is accompanied by widespread peritoneal dissemination, scalloped organ surfaces, and omental caking.
Distinguishing Feature
Simple mucocele is confined to the appendix without peritoneal dissemination. PMP shows peritoneal mucinous implants in addition to the appendiceal lesion.
Distinguishing Feature
Peritoneal carcinomatosis shows solid enhancing nodular implants, organ parenchymal invasion, and lymphadenopathy. In PMP, implants are low-density (mucinous) without organ invasion, with scalloping compression.
Urgency
urgentManagement
surgicalBiopsy
Not NeededFollow-up
specialist-referralCytoreductive surgery (CRS) + hyperthermic intraperitoneal chemotherapy (HIPEC) is performed at specialized centers for PMP diagnosis. Peritoneal Cancer Index (PCI) should be calculated preoperatively to assess peritoneal disease burden. In low-grade PMP (DPAM), 10-year survival with CRS+HIPEC is >80%, while in high-grade form (PMCA) it is ~20%. Percutaneous biopsy is contraindicated due to mucin dissemination risk. Resection of the appendiceal primary lesion is an integral part of treatment. Postoperative CT follow-up should be continued at 6-12 month intervals for 10 years. Tumor markers (CEA, CA19-9, CA-125) are helpful in follow-up.
The standard treatment for PMP is cytoreductive surgery (CRS) + HIPEC (hyperthermic intraperitoneal chemotherapy). Disease extent is assessed using the Peritoneal Cancer Index (PCI). Low-grade PMP (DPAM) has a relatively good prognosis, while high-grade (PMCA) follows an aggressive course. Identification of the appendix as the primary source affects treatment planning.