Histol Histopath (1 992) 7: 625-628 Histology and Histopathology Radiohistology and histochemistry of barium granuloma of the colon and rectum M. Mayorga, F. Castro, F. Fernández, F. Val-Bernal and V. Arribas Department of Pathology and Radiology, National Hospital .Marqués de Valdecillaw, School of Medicine, Cantabria University, Santander, Spain Summary. Barium granuloma of the colon and rectum is a rare complication of X-ray examination of the digestive tract using barium. The authors report 5 new cases occurring in the last 3 years. Histological examination revealed a granulorhatous reaction with greyish finely granular refractile PAS-negative material located in the cytoplasm of histiocytes and in the interstitial space. The radiographic study of the paraffin blocks confmed the nature of this material, which was X-ray opaque, and this was corroborated histochemically with the rhodizonate technique. Key words: Barium granuloma, Radiohistology, Histochemistry lntroduction The complications or side-effects resulting from X- ray examination of the gastrointestinal tract using a contrast medium containing barium sulphate are rare (Swartz, 1955; Gordon and Clyman, 1957; Carter, 1963; De Mascarel et al., 1988; Subramanyam et al., 1988). One of these side-effects in the colon or rectum is what is temed a ~barium granuloma», first described by Beddoe in 1954 (Beddoe et al., 1954). The importante of recognising this entity lies in the fact that, endoscopically, it can mimic other lesions including a neoplastic process (Gordon and Clyman, 1957; Hariri et al., 1983; De Mascarel et al., 1988). Moreover, histological findings observed with routine techniques, though they may be characteristic, often go unnoticed (De Mascarel et al., 1988). The aim of this paper is to report 5 new cases of barium granuloma occurring in the last 3 years and to confirm their nature, and therefore their diagnosis, through radiohistological and histochemical techniques, from paraffin blocks. Offprint requests to: Dr. D. Fernando Val-Bernal, M.D., Ph.D., Departamento de Patologia, Hospital Nacional -Marqu6s de Valdecillan, 39008 Santander, Spain Materials and methods Patients The five cases correspond to patients of both sexes, two males and three females, whose ages ranged from 58 to 76 (average age 64). At endoscopy, three of them showed yellowish macular lesions with a smooth, regular surface or scab-like lesions in the colon or rectum. The fourth and fifth cases were a chance finding in two surgical specimens from colectomy (Table 1). Sample processing The samples obtained were fixed in 10% neutral- buffered formalin for 24 hours, routinely processed and then embedded in paraffin. Tissue sections 5 pm thick were stained with haematoxylin and eosin and Periodic Acid Schiff. Radiohistological technique X-rays were taken of the paraffin blocks with a Senographe 500 T, Senix H-F (F 0.1 mm). Barium sulphate and normal intestinal mucosa, both embedded in paraffin, were used as positive and negative controls respectively. Histochemical technique Further histological sections were stained with the rhodizonate technique at a temperature of 60" C for 2 hours (Culling et al., 1985). Results The five patients had had x-ray exarnination with a barium contrast medium (opaque enema) at least 1 year prior to the discovery of the lesion (Table 1). Histologically, particularly at the leve1 of the mucosa andlor submucosa of the colon or rectum, an organised mass of mononucleate cells, identified as histiocytes or