Imaging the peritoneum for malignant processes

•. A clear understanding of peritoneal anatomy is necessary for the identification of peritoneal metastatic disease and primary tumours.•. Peritoneal metastases disseminate through the peritoneum in four ways: (1) direct spread along the peritoneal reflections; (2) intraperitoneal seeding; (3) lymphatic extension; and (4) embolic haematogenous spread.•. Metastatic peritoneal involvement is far more common than peritoneal primary malignancy. •. Primary peritoneal neoplasms are rare and are most often malignant. They arise from mesenchymal elements, and include mesothelioma and sarcoma.•. CT is relatively specific at identifying peritoneal malignancy but has relatively low sensitivity.•. CT remains the imaging modality of choice for the diagnosis, staging and follow‐up of peritoneal malignancy. MRI is gaining importance and has the advantages of multiplanar imaging and lack of ionizing radiation.