Detection of peritoneal metastases

Abstract

The peritoneum is the largest and most complexly arranged serious membrane in the body. The potential peritoneal spaces, the peritoneal reflections forming peritoneal ligaments, mesenteries, omenta, and the natural flow of peritoneal fluid determine the route of spread of intraperitoneal fluid and consequently disease spread within the abdominal cavity. The peritoneal ligaments, mesenteries, and omenta also serve as boundaries and conduits for disease spread. Peritoneal metastases spread in four ways: (1) Direct spread along peritoneal ligaments, mesenteries and omenta to non-contiguous organs; (2) Intraperitoneal seeding via ascitic fluid; (3) Lymphatic extension; (4) Embolic haematogenous spread. Before the introduction of cross-sectional imaging, the peritoneum and its reflections could only be imaged with difficulty, often requiring invasive techniques. Computed tomography and to a lesser extent sonography and MR imaging allow us to examine the complex anatomy of the peritoneal cavity accurately, which is the key to understanding the spread of peritoneal disease. This article reviews the detection of peritoneal metastases.

Figure 1

Diagrammatic representation of the peritoneal anatomy. (a) Coronal view of the posterior peritoneal spaces. (b) Coronal view of the peritoneal attachments to the abdominal wall.

Figure 2

Direct spread of metastatic deposits in the lesser omentum/transverse mesolocolon. (a) Axial post contrast CT scan in a 59-year-old male with gastric cancer showing extension of gastric cancer into the lesser omental fat. (b) Axial post contrast CT scan in a 45-year-old female with carcinoma of the pancreatic body with metastatic extension in the transverse mesocolon causing bowel obstruction.

Figure 3

Metastatic deposits in the greater omentum. (a) Post contrast axial CT scan in a 49-year-old female with carcinoma of the ovary showing several nodular, ill defined masses in the greater omentum anteriorto the colon. Note also the ascites. (b) Axial post contrast CT scan in a 66-year-old female with adenocarcinoma of the bowel showing a bulky, ‘cake-like’, enhancing omental deposit. (c) Axial post contrast CT scan in a 65-year-old male patient with renal carcinoma showing markedly enhancing deposits within the greater omentum surrounded by ascites. Note also enhancing serosal deposits on the surface of the bowel.

Figure 4

Small bowel mesenteric deposits. Post contrast axial CT scan in a 28-year-old female with carcinoid tumour of the terminal ileum. Note the mesenteric mass at the root of the small bowel mesentery and linear soft tissue stranding and tethering in the small bowel mesenteric fat.

Figure 5

Intraperitoneal seeding of peritoneal metastases. (a) Axial post contrast CT scan in a 49-year-old female with carcinoma of the ovary demonstrating nodular parietal peritoneal thickening, in association with a deposit in Morison’s pouch, and ascites. (b) Axial CT scan in a 66-year-old female with carcinoma of the ovary showing calcified peritoneal metastases. (c) Axial post contrast CT scan in the same patient as in Fig. 3A. Note the clips from previous renal surgery. Multiple enhancing peritoneal metastases are outlined by ascites. Note also enhancing deposits in the greater omental fat.

Figure 6

Pseudomyxoma peritonei in mucinous cystadenocarcinoma of the appendix in a 44-year-old female. (a) Axial post contrast CT scans showing low density deposits producing scalloping of the liver margin. (b) The pressure of the gelatinous material prevents bowel loops floating up towards the anterior abdominal wall.

Figure 7

Lymphatic metastases. 45-year-old male patient with Non-Hodgkins Lymphoma showing the characteristic ‘Sandwich’ sign of mesenteric and retroperitoneal lymph node involvement.

Figure 8

Embolic metastases. (a)Post contrast axial CT scan in a 60-year-old male with malignant melanoma showing a well defined embolic serosal deposits causing small bowel obstruction. (b) Axial CT scan in a 40-year-old male with leiomyosarcoma of the retroperitoneum showing multiple well defined soft tissue masses adjacent to the bowel in the mesenteric fat.