Fluid Levels in Medical Imaging

Radiologists must be familiar with the appearances and significance of fluid levels. It is important to appreciate that only images in the vertical plane will show this phenomenon.On radiographs the common fluid levels : chest (achalasia, hiatus hernia, hydropneumothorax or cavitating lesion), abdomen (intestinal obstuction) and truama (lipohaemarthrosis in knee and paranasal sinuses in facial fractures).CT with its high inherent contrast between gas, fat and fluid is an excellent technique for the demonstration of fluid levels in abdomen, chest and in extremity truama. MRI adds greater inherent contrast for different types of liquids and is used to demonstrate layering in lipohaemarthrosis, staging bone and soft tissue tumours, aneurysmal bone cyst, giant cell tumour and synovial sarcoma. Although ultrasound is the most difficult imaging technique to reliably demonstrate fluid levels it can be used to show levels due to seperation of blood withing a false aneurysm.

To read more: Clinical Radiology December 2007