Transanorectal ultrasonography in anal carcinoma. A prospective study of 21 patients

Twenty-one consecutive patients with anal carcinoma of squamous cell type were evaluated by transanorectal ultrasonography (Brüel & Kjaeer) prior to radiation therapy. The normal anal anatomy, with three distinct layers, was easily demonstrated both in vitro and in vivo. The middle, low echogenic layer corresponded above the dentate line to the muscularis propria and more distally to the internal and external sphincters. A hypoechoic area, representing tumour, was detected in all patients. Using the ultrasound findings, it appeared possible to classify the depth of tumour invasion into four levels with respect to whether or not invasion had reached or penetrated beyond the muscular wall or into adjacent organs. Eighteen of 21 tumours had penetrated the muscular wall. In 3 cases low echogenic, rounded structures, interpreted as enlarged lymph nodes, were identified. The ultrasonographic findings were compared with digital staging. Tumour invasion had penetrated the muscular wall in 2 out of 3 stage T1 patients and in 10 out of 11 stage T2 patients. Prospective studies will show whether estimates of tumour size and depth of invasion in relation to various normal structures, as judged by ultrasonography, are of value prognostically and for the choice of therapy.