Peritoneal carcinomatosis is the intraperitoneal dissemination of any cancer that does not originate from the peritoneum itself.
It is the most common diffuse peritoneal disease however other entities may be responsible for peritoneal invasion.
In order to treat the patients adequately it is crucial that the radiologist can be able not only to diagnose peritoneal carcinomatosis but also to exclude its mimics.
Inflammatory and malignant diseases of the peritoneum may present with overlapping features both clinically and at imaging.
Awareness of the patient’s clinical history is essential for an accurate imaging interpretation and differential diagnosis.
On imaging normal peritoneum appears as a fine,
thin structure,
and therefore it is hardly detectable.
The pathologic involvement produces a thickening of the peritoneal layers.
According to the type of peritoneal involvement,
it is possible to identify three different patterns 1 :
1- Smooth uniform pattern:
Regular peritoneal thickening
Smooth interface with the omental fat
Fig. 2: 68-year-old patient with fibrinous peritonitis. Abdominal and Pelvic MRI T2WI show smooth peritoneal thickening associated with ascites.
References: Department of Radiology, Champalimaud Foundation, Lisbon
Fig. 3: 68-year-old patient with fibrinous peritonitis. Abdominal MRI T1WI with fat saturation after contrast shows smooth and enhancing peritoneal thickening associated with ascites.
References: Department of Radiology, Champalimaud Foundation, Lisbon
2- Irregular pattern: Fig. 4
Nonuniform peritoneal thickening
Irregular interface between the thickened peritoneum and the omental fat.
Focal thicker segments show an obtuse angle with the peritoneum
Fig. 4: Nonuniform peritoneal thickening in a 56-year-old female patient with peritoneal tuberculosis. Abdominal CT shows irregular thickening of the peritoneum (arrow). Focal thicker segments show obtuse angle with the peritoneum.
References: Department of Radiology, Champalimaud Foundation, Lisbon
3- Nodular pattern: Fig. 5
Absent peritoneal thickening
Well-defined nodules of soft tissue attenuation along the peritoneum
- More common in: Peritoneal carcinomatosis; Peritoneal lymphomatosis; Mesothelioma
Fig. 5: 63-year-old female patient with ovarian cancer and peritoneal carcinomatosis. Abdominal CT demonstrates the presence of enhancing nodules along the peritoneum(arrows) and absent peritoneal thickening.
References: Department of Radiology, Champalimaud Foundation, Lisbon
Although less frequently,
the irregular and nodular patterns can be present in benign peritoneal diseases.
Some imaging features may help to avoid misdiagnosis of malignancy:
- Omental ( Fig. 6 ) and small bowel mesentery ( Fig. 7C ) involvement by nodules is more common in malignancy
- Lower small bowel mesentery near the terminal ileum ( Fig. 7E ) is one of the sites of initial involvement by tumors.
Other sites include: paracolic gutters,
the sigmoid mesocolon,
the pouch of Douglas and the anterior parietal peritoneum ( Fig. 8 E)
- Omental involvement is uncommon in acute peritonitis.
Fig. 6: 63-year-old female patient with ovarian cancer. Abdominal and pelvic MRI show the peritoneal involvement with formation of omental cake (A) and a complex multiloculated cystic lesion at the right ovary (B).
References: Department of Radiology, Champalimaud Foundation, Lisbon
Fig. 7: A- Involvement of small bowel mesentery in a 70-year-old female patient with endometrial cancer and peritoneal carcinomatosis. B- 41-year-old female patient presenting with ovarian serous carcinoma and a large peritoneal implant located in the lower small bowel mesentery.
References: Department of Radiology, Champalimaud Foundation, Lisbon
Fig. 8: E- Presence of implant located at the anterior parietal peritoneum in a female patient with ovarian cancer and peritoneal carcinomatosis; F- Nodular thickening of the pelvic peritoneum in a 70-year-old female patient with ovarian cancer and peritoneal carcinomatosis.
References: Department of Radiology, Champalimaud Foundation, Lisbon