Accurate staging of rectal carcinoma is crucial for planning surgery and the indication for adjuvant therapy. Although computed tomography and magnetic resonance imaging are very sensitive in the detection metastastic disease, local staging of rectal cancer with these techniques has been disappointing.
Endorectal ultrasound (EUS) remains the most accurate method for staging of rectal cancer. High accuracy rates in the assessment of the depth of infiltration (T stage) (80–90%) and in the determination of the lymph node status (70–80%) have been confirmed in several studies. Continued research and development has made the instrumentation for EUS more accurate and user-friendly. New techniques that have contributed significantly to the evolution of EUS include three-dimensional EUS, high-frequency miniprobes and transrectal ultrasound-guided biopsy techniques. Further improvement can be expected by contrast enhancement with microbubbles and colour Doppler imaging.