Computed tomography (CT) gives unique information about the margins of the intra-abdominal organs and the intervening fat and fascial planes. Not infrequently, these planes appear abnormal without any visible underlying cause. We present 85 patients in whom such an abnormality was shown. Although the appearances are non-specific, tumour infiltration was the most common cause (57 (70%) out of 82 where the cause is known). Infection, secondary effects of pancreatitis, granulomatous disease, haemorrhage, early ascites or oedema and the effects of radiotherapy should all be considered in the differential diagnosis.