CASE REPORT Annals of Nuclear Medicine Vol. 6, No. 2, 99-102, 1992 SPECT demonstration of splenosis Shoji YOSHIDA,* Tohru SUEMATSU,* Tomofumi MOTOHARA,* Kanji OGAWA,* Tadashi KOIZUMI,* Masahiro MIZUTANI,* Masakazu YANASE,* Hirofumi FUJIHARA,* Hiroshi HARANOMURA** and Yoshio ISHIKAWA** *Department of Radiology, Hyogo Medical Center for Adults **Department of Surgery, Hyogo Medical Center for Adults Splenosis is defined as the heterotopic autotransplantation of splenic tissue. The main cause of splenosis is splenic rupture following abdominal trauma, in which fragments of splenic tissue are seeded throughout the peritoneal cavity. Demonstration of splenosis by scintigraphy or CT imaging has been reported, but there is no previous report of simultaneous demonstration by SPECT and CT imaging. Autotransplantation of splenic tissue in the abdominal cavity forms a solid tumor-like image on CT and is difficult to differentiate from other abdominal masses. In such cases, SPECT demonstration of splenosis is very important for identification of its exact site. A case report of splenosis is presented, in which simultaneous demonstration by SPECT and CT was performed. This was confirmed at laparotomy for gastrectomy. Key words: splenosis, SPECT, Tc-99m-Sn colloid, CT, laparotomy for gastrectomy INTRODUCTION IN 1939, Buchbinder and Lipkoff1 defined splenosis as autoimplantation of splenic tissue following splenic rupture. They reported a case of multiple splenosis throughout the abdomen, involving the peritoneal surface, abdominal wall and omentum. Once splenic fragments are implanted, they are fed by a new blood supply. About 80 cases of splenosis have been reported since 1939. In these cases, the imaging methods used were ultrasound, CT and scintigraphy.2-10 The solid masses formed by the spread of splenic fragments mimic intraabdominal masses such as accessory spleen, hemangioma, endometriosis and metastatic peritoneal tumors.11-13 There are several reports of splenosis mimicking tumors not only in the peritoneal space but also in the intrathoracic and perirenal space.5,14 The phagocytic Kupffer's cells of the reticulo- Received October 7, 1991, revision accepted December 11, 1991. For reprints contact: Shoji Yoshida, M.D., Department of Radiology, Hyogo Medical Center for Adults, 13-70 Kitaooji-cho, Akashi-shi, Hyogo 673, JAPAN. endothelial system (RES) allow the evaluation of the splenic tissue by means of colloidal substances. In addition, scintigraphic study by SPECT makes possible a comparative study with CT, and can identify the precise location of implanted splenic fragments. CASE REPORT A 59-year-old man was admitted to our medical center to undergo surgery for early gastric cancer. The patient had a previous history of left abdominal trauma followed by splenectomy and left nephrectomy. Prior to surgery, a routine CT scan was performed to evaluate metastasis. CT images did not show liver metastasis but several nodules were present in the abdomen (Figs. 1 and 2). Anterior planar and SPECT data for the abdomen were obtained about 20 min after intravenous injection of 111 MBq (3 mCi) of Tc-99m Sn colloid. A paired large field of view gamma camera (Toshiba GCA-90A) with a high resolution collimator and a dedicated computer (Toshiba GMS-550U) were used. The anterior whole body image was obtained at a scanning speed of 20 cm/min. The SPECT data were acquired continuously for 15 min through 180 degrees at 6 degree intervals with 20 sec. for each projection acquisition. Projection data were pretreated by the 9 point smoothing method and reconstructed with a Chesler filter. Photon attenuation was not corrected. Anterior whole body scintigraphy revealed abnormal hot spots in the upper and lower abdomen. As the display mode was used in a low window setting to delineate the small nodules, normal hepatic and bone marrow uptake was very high (Fig. 3). SPECT images, but not the planar images, could detect the precise location of hot spots (Figs. 4, 5). The SPECT images showed hot spots in the following sites: 1) the middle part of the left upper abdomen 2) the posterior part of the left upper abdomen 3) the left upper portion of the pelvis contiguous to the left crista iliaca. 4) the lower pelvis adjacent to the right sacroiliac joint, and 5) the lower pelvis near the rectum. These hot spots corresponded to the abnormal nodules on CT. The laparotomy performed for gastrectomy revealed multiple reddish brown nodules, with diameters ranging from 5 to 30 mm, attached to the peritoneum in the pouch of Douglas, on the serosal surface of the duodenum and near foramen of Winslow (Fig. 6). A frozen section of one of the nodules showed splenic tissue microscopically. The blood specimen did not demonstrate Howell-Jolly bodies, indicating the presence of splenic function. DISCUSSION Since the first reported case of splenosis by Buchbinder and Lipkoff in 1939.1 the number of reported cases of splenosis is now over 80. In most cases, diagnosis of splenosis depends on a past history of left flank injury with splenic rupture. CT and US provide useful information for the differentiation of splenosis from other abdominal tumors. Splenosis has been found in various sites in the peritoneal cavity, including the intestinal serosal surface, the parietal peritoneum, and the diaphragmatic surface.1,15 In addition, unusual cases of retroperitoneal and intrathoracic splenosis have been reported.5,14 The peripheral blood supply of splenulus is derived from small perforating vessels that arise at the implanted site. Splenosis mimics solid masses, such as endometriosis, hemangioma and metastatic tumor.12,14 An accessory spleen can be differentiated from splenosis, based on its location at the splenic hilus. The implants are described as dark reddish-brown, sessile or pedunculated nodules. They vary in number, with as many as 400 having been reported. The size varies from millimeters to several centimeters. The CT appearance of these masses is nonspecific. However, CT has high sensitivity for masses smaller than 1 cm in diameter. Although the resolution of the scintigram is rather poor, the method of radionuclide study with Tc-99m Sn colloid or Tc-99m- heat damaged RBC4-9 allows presise specific confirmation. The present study utilized Tc-99m-Sn colloid uptake by the RES of the liver, spleen, and bone marrow. With Tc-99m-labelled heat-denatured autologous erythrocyte splenic imaging in 90 splenectomized patients, splenosis was detected in 32%. The incidence was 50% in those patients with traumatic rupture, and was only 16% in those who underwent splenectomy for hematologic disorders.4 Radiolabelled heat-damaged red cell scanning and Indium 111 (In-111-labelled autologous platelet) scanning have also been used to image residual splenic tissue. SPECT imaging was able to demonstrate the precise location of splenosis and its results were compatible with those of CT imaging. REFERENCES 1. Buchbinder JH, Lipkoff CJ: Multiple peritoneal splenic implants following abdominal injury. Surgery 6: 927-934, 1939 2. Lindell RG, Brown JM, Lindgren RD: Splenosis: CT demonstration of heterotopic autotransplantation of splenic tissue. J Comput Assist Tomogr 6: 1184-1187, 1982 3. Mandelson DS, Cohen BA, Armas RD: CT appearance of splenosis. J Comput Assist Tomogr 6: 1188-1190, 1982 4. Stewart CA, Sakimura IT, Siegel ME: Scintigraphic demonstration of splenosis. Clin Nucl Med 11: 161-164, 1986 5. Schiff RG, Leonidas J, Shende A, et al: The noninvasive diagnosis of intrathoracic splenosis using Technetium-99m Heat-Damaged Red Blood cells. Clin Nucl Med 12: 785-787, 1987 6. Atkins HL, Eckelman WC, Hauser W, et al: Splenic sequestration of Tc-99m-labelled red blood cells. J Nucl Med 21: 579-583, 1972 7. Jacobson SJ, De Naldo GL: Splenosis demonstrated by splenic scan. J Nucl Med 12: 570-572, 1971 8. Abu-Nema T, Nawaz K, Sadek S, et al: Splenic implants evaluation with radionuclide methods. Radiology 163: 641-643, 1986 9. Bidet AC, Schmidt GD, Mas J, et al: Diagnosis of splenosis: The advantage of splenic scintiscanning with Tc-99m-heat damaged red blood cells. Eur J Nucl Med 12: 357-358, 1986 10. Davis HH, Varki A, Heaton WA, et al: Detection of accessory spleens with Indium-111-labeled autologous platelets. Am J Hematol 8: 81-86, 1980 11. Beahrs Jr, Stephans DH: Enlarged accessory spleens: CT appearance in postsplenectomy patients. Am J Radiol 135: 483-486, 1980 12. Stovall TG, Ling FW: Splenosis: Report of a case and review of the literature. Obstetrical and Gynecological Survey 43: 69-72, 1988 13. White JD, West AN, Priebat DA: Splenosis mimicking an intra-abdominal malignancy. The American Journal of Medicine 87: 687-690, 1989 14. Roucos S, Tabet G, Jebara VA, et al: Thoracic splenosis. J Thoracic Cadiovasc Surg 99: 361-363, 1990 15. Fleming CR, Dickson ER, Harrison EG Jr: Splenosis, Autotransplantation of splenic tissue. Am J Radiol 61: 414-419, 1976