Pseudomyxoma Peritonei

R. Brooke Jeffrey, MD

Key Facts

Terminology

Diffuse intraperitoneal accumulation of gelatinous ascites due to rupture of well-differentiated mucinous adenocarcinoma of appendix

Imaging

Best imaging tool: CECT
Protocol advice
- Oral and IV contrast CECT
- 150 mL IV contrast injected at 2.5 mL/sec
- 5 mm collimation with reconstruction at 5 mm intervals

Top Differential Diagnoses

Carcinomatosis without mucinous ascites
Peritoneal sarcomatosis
Bacterial peritonitis
TB peritonitis

Pathology

Controversial etiology: Prior theory held that PMP due to rupture of mucinous tumors of appendix or ovary
More recent theory holds that PMP always appendiceal in origin; ovarian lesions were metastatic

Clinical Issues

Ultimately all patients die from this disease

Diagnostic Checklist

Consider ovarian carcinomatosis
Image interpretation pearls
- Scalloping of liver and spleen contour by low-attenuation masses
- Cystic implants on ligaments, such as falciform and gastrohepatic ligament

(Left) Axial CECT in a 62-year-old man with a history of appendiceal carcinoma, now presenting with progressive abdominal distension and partial bowel obstruction, demonstrates massive, loculated ascites. Note the scalloped surface of the liver and spleen

due to peritoneal tumor implants. (Right) Axial CECT in the same patient reveals that the cystic or gelatinous metastases are also evident as omental masses

(Left) Axial CECT in a 61-year-old man with recent resection of an appendiceal carcinoma, now presenting with abdominal distension, shows a classic scalloped surface of the liver and spleen due to loculated mucinous collections of malignant ascites

. (Right) Axial CECT in the same patient reveals the presence of an ileostomy

, which was required because the loculated mucinous peritoneal metastases resulted in compression, distortion, and partial obstruction of the bowel.

TERMINOLOGY

Abbreviations

Pseudomyxoma peritonei (PMP)

Definitions

Diffuse intraperitoneal accumulation of gelatinous ascites due to rupture of well-differentiated mucinous adenocarcinoma of appendix
- Rarely due to rupture of other mucinous tumors of colon, stomach, pancreas, gallbladder, fallopian tube
- Ovary was previously thought to be primary site, but ovarian lesions are now thought to be metastatic from appendiceal primary

IMAGING

General Features

Best diagnostic clue
- Scalloping of liver and spleen contour by low-attenuation masses
Location
- Often diffuse throughout peritoneal cavity
- Along mesenteries and ligaments
- Extensive peritoneal involvement common
- Subphrenic spaces
  - Perihepatic and perisplenic locations most common
Size
- Cystic implants vary in size
Morphology
- Gelatinous low-attenuation masses

Radiographic Findings

Radiography
- Evidence of ascites
- Lateral displacement of liver margin
- Lateral displacement of cecum
- Pelvic “dog’s ears”
  - Lobulated fluid collections in pelvis on either side of urinary bladder
- Displacement of bowel loops centrally within abdomen