Purpose: To assess the depth of infiltration of rectal cancer with transrectal ultrasound (US) (TRUS) and analyze interpretation errors.
Materials and methods: Fifty-five consecutive patients with rectal cancer who underwent TRUS were prospectively studied. The effect of different patient inclusion criteria and US criteria was evaluated retrospectively.
Results: Extensive overstaging of T2 tumors, partially caused by inflammatory (desmoplastic) reaction or retraction of the muscularis propria, resulted in a specificity of only 24% for detection of perirectal infiltration. Sensitivity was 97%, and accuracy was 64%. Considerable variation in staging accuracy was observed when different patient selection criteria were used. Variation of US criteria improved differentiation between T2 and T3 tumors only slightly.
Conclusion: The effect of different US criteria on differentiation of T2 and T3 tumors is limited. Spontaneous or iatrogenic inflammation is a major limiting factor. The accuracy of TRUS in staging rectal cancer is affected by patient inclusion criteria.