BACKGROUND:As the bone and marrow tissue have very special structure, it is difficult to simultaneously display the bone with tough hard tissue and bone marrow tissues containing various immature hematopoietic cel s in the conventional process of pathological section preparation. OBJECTIVE:To choose the best decalcifying solution that cannot only completely remove the calcium in the bone tissue but also protect the structure of bone marrow tissues and cel s from damage. METHODS:Bone marrow tissues from the long bone of dogs were randomly divided into four groups. Under the same conditions, the bone marrow tissues were decalcified with 14%formaldehyde saline solution of nitric acid (group A), 14%nitric acid solution (group B), 20%A saline solution of hydrochloric acid formaldehyde (group C) and 20%A hydrochloric acid aqueous solution (group D). Decalcified time was recorded, fol owed by routine dehydration, section, hematoxylin-eosin staining and microscopic observation. Pathological section quality and hematoxylin-eosin staining were compared among the four groups. RESULTS AND CONCLUSION:Group A had the best sections and hematoxylin-eosin staining, strongest decalcified ability, shortest decalcified time and minimum damage to the bone marrow. Group B had the worst results of section and hematoxylin-eosin staining, in which, the bone tissues were loose and became yel ow and the bone marrow tissue were damaged greatly, and the decalcified effect was worse. Group C was worse than group A in decalcified ability, damage degree, section quality and hematoxylin-eosin staining results. Group D also had a better result of section and hematoxylin-eosin staining as wel as exhibited uniform decalcification effect and less damage to the bone marrow, which was ranked between group B and group C. Al the four kinds of decalcifying solutions have a good decalcification ability, but the section quality and hematoxylin-eosin staining results rank as fol ows:Group A>Group C>Group D>Group B. Taken together, 14%formaldehyde saline solution of nitric acid is ideal for the clinical preparation of pathological sections.

Objective To investigate the CT manifestations of recto-endometriosis. Methods Three pathologically proved cases of recto-endometriosis were reported, the CT features and clinical manifestations were investigated retrospectively with review of literatures. Results The patients were all menstruating females (28, 34, and 45 years old, respectively), and anal pain emerged during menses in one case. Rectal examination revealed stiff immobile mass along the rectal wall in all three cases. All the cases showed solid masses on CT scan with moderate enhancement after contrast administration. Two of them confined to the rectal walls, another involved the rectum and peri-rectal aspect. One case was misdiagnosed as well-differentiated adenocarcinoma of rectum in frozen section by biopsy specimen.Conclusion A solid mass was always found in recto-endometriosis. No characteristic CT feature was manifested. Attention should be paid to the differentiation from rectal tumors when making the diagnosis.