Int J Clin Exp Med 2017;10(8):11710-11716www.ijcem.com /ISSN:1940-5901/IJCEM0053132

Original ArticleCT and MRI imaging characteristics of unexpected splenic autotransplantation after splenectomy

Zhihao Ren1, Qianjiang Ding1, Jianhua Wang1, Can Tu1, Siqi Wang1, Chao Cheng2, Changjing Zuo2

1Department of Radiology, The Affiliated Hospital of Medical College of Ningbo University, Ningbo, China; 2Depart-ment of Nuclear Medicine, Changhai Hospital, the Second Military Medical University, Shanghai, China

Received March 17, 2017; Accepted April 28, 2017; Epub August 15, 2017; Published August 30, 2017

Abstract: Objective: To discuss the imaging characteristics of splenosis for improving its diagnostic accuracy. Meth-ods: Twelve patients with splenic autotransplantation were diagnosed by surgical pathology or needle biopsy. Pa-tients underwent CT and MRI plan and enhanced scanning, 2 cases also underwent 99mTc-DRBC scanning, and the imaging data were collected. Results: Multiple nodules were found in 8 cases and single nodule was found in 4 cases. The nodules were detected in splenic recess (10 cases), in tail of the pancreas (5 cases), in right liver (3 cas-es), and in other parts of abdominal cavity (3 cases). The size of nodules was different, and the maximum diameter of 94.57% of the nodules were less than 3 cm. The nodules were all homogeneous and soft without cystic change, calcification or necrosis. Slightly short T1 and short T2 signal were shown in tail of the pancreas in 1 case. Long T1 and long T2 signal were shown in the rest cases. In CT arterial phase, blood supply from abdominal aorta was shown in nodule of right liver in 1 case. The nodules were surrounded by thin layer of low density ring, which showed long T1 and long T2 signal. Homogeneous or inhomogeneous enhancement was shown in the arterial phase, continu-ous homogeneous enhancement was shown in portal venous phase, and the decline degree of enhancement was significant in delayed phase. The findings of 99mTc-DRBC scanning were obviously strong radioactive concentrations in nodules. Conclusion: Multiple nodules were found in abdominal cavity with homogeneous density or signal and clear boundary. The enhanced features were consistent with spleen. The possibility of splenosis should be consid-ered by the history of splenic trauma or splenectomy.

Keywords: Splenosis, CT, MRI, 99mTc-DRBC, splenic trauma

Introduction

Splenosis is an autotransplantation of spleen, which is caused by splenic trauma or splenec-tomy [1]. The spleen tissue usually implants in the abdominal cavity or outside the abdominal cavity, and establishes blood supply for its development. Ectopic growth of spleen tissue debris form space-occupying lesions, so sple-nosis is also called ectopic spleen planting [2, 3]. Ectopic spleen can be divided into congeni-tal accessory spleen and acquired splenosis [3]. Splenosis has essential difference from accessory spleen and surgery autologous spl- enic planting [4].

Splenosis secondary to splenic trauma is com-mon, and the incidence rate is 26-67% [1, 5, 6]. The shortest interval time of spleen planting after trauma is 5 months, and the longest inter-

val time is 32 years (average time 10 years) [3]. When the tissue of spleen implantation and organ are closely related, it is easy to misdiag-nose as tumors and result in clinical misdiagno-sis [7]. On 99mTc-DRBC scanning, multiple radio-active lesions can be seen in abdominal cavity, and the locations of multiple masses are con-sistent with CT results. The theory [8] is that heat-denatured red blood cells (RBC) are first captured by spleen, then are the liver and mar-row. The red blood cells are damaged in spleen, and heme in red blood cells are digested and metabolized. Hence, radioactive concentration of the spleen is 2-4 times higher than liver. 99mTc-DRBC has a higher sensitivity and speci-ficity for the diagnosis of splenosis [9].

In this study, twelve patients with splenic auto-transplantation were diagnosed by surgical pathology or needle biopsy, and the imaging

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data were collected for improving its diagnostic accuracy and avoid unnecessary surgeries.

Materials and methods

General information

From April 2008 to May 2016, information of 12 patients confirmed by surgical pathology or needle biopsy were collected. There were 8 males and 4 females aged 18 to 69 years (median age of 43.7). There were no symptoms in 8 patients, who were detected by abdominal ultrasound or CT reexamination. The other 4 patients were detected by abdominal CT because of jaundice, hematuria, haemateme-sis and black stool. Six patients underwent splenectomy because of traumatic spleen rup-ture, and the other six because of cirrhosis and portal hypertension. The splenectomy time was 5 months to 7 years with an average time of 3.5 years. Six patients were confirmed by surgical pathology and the other six were by needle biopsy.

CT and MRI examinations

Eight patients underwent CT and MRI plain scanning and dynamic enhanced scanning. In addition, two of them underwent 99mTc-DRBC scanning, which had higher sensitivity and specificity for diagnosis of splenosis [8, 10]. Four patients only underwent CT plain scanning and dynamic enhanced scanning. 16-slice spi-

ral CT (SIEMENS, Sensation) was used in 5 cases, and 256-slice spiral CT (Philips iCT) was used in 7 cases. Tube voltage was 120 kV, tu- be current was 220-250 mAs, and the layer thickness was 5 mm. Non-ionic contrast agent (iohexol) was used in CT examinations. The injection dose was 80-100 ml with injection rate of 2.5-3.0 ml/s. Arterial phase, portal venous phase and delayed phase scanning were conducted at 25-30 s, 60 s, 180 s after drug injection, respectively. Siemens 1.0T Harmony MRI scanner was used in 5 cases, and GE SignaHDxt 1.5T double gradient mag-netic resonance scanner was used in 3 cases. T1WI and T2WI axial scanning were used, and the three-phase dynamic enhanced scanning of MRI was consistent with CT. The contrast agent was Gd-DTPA in MRI examination. The injection dose was 0.2 mmol/kg with injection

Figure 1. Splenosis of a 44-year-old man after sple-nectomy for trauma. On CT scanning, oval nodules in tail of the pancreas and round nodules in spleen fossa showed soft and compact tissue with clear boundary and homogeneous density.

Figure 2. Splenosis of a 55-year-old man after liver cirrhosis splenectomy. On MRI scanning, round nod-ules in tail of the pancreas showed slightly short T1 (A) and short T2 (B) signal with clear boundary and homogeneous signal.

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rate of 2.5 ml/s. Two patients underwent 99mTc-DRBC examination.

Results

CT and MRI characteristics

Thirty-eight nodules were found in the 12 patients. Twenty-one of 38 nodules were found in the left inferior phrenic splenic recess in 10 cases. The nodules were found in tail of the pancreas in 5 cases, and there was only a nod-ule in each case. The nodules were found in right liver in 3 cases, and there was a nodule in right posterior lobe of liver and 5 nodules in the surface of right liver. The nodules were found in other parts of abdominal cavity in 3 cases, there were 2 nodules in kidney, a nodule in iliac fossa and 3 nodules in posterior peritoneum. Multiple nodules were found in 8 cases, and each case had 2-8 nodules. Single nodule was found in 4 cases, and the 4 patients underwent

splenectomy because of liver cirrhosis and por-tal hypertension. The shape of nodules was round or oval with clear boundary (Figure 1). The size of nodules was different, and the maxi-mum diameter was 0.5-3.6 cm. 94.57% of the nodules were less than 3 cm. The nodules were all homogeneous and soft without cystic change, calcification or necrosis. CT values were 32.3-52.8 HU. In MRI scanning, slightly short T1 and short T2 signal were shown in tail of the pancreas in 1 case (Figure 2). Long T1 and long T2 signal were shown in the rest cases. In arterial phase of enhanced CT scan-ning, most nodules were significantly homoge-neous enhancement, and only 6 nodules were heterogeneous enhancement and showed plaque-like enhancement with CT values of 53.3-90.5 HU. Blood supply from abdominal aorta was shown in nodule of right posterior lobe of liver in 1 case. The nodule was sur-rounded by thin layer of low density ring, which showed long T1 and long T2 signal (Figure

Figure 3. Splenosis of a 41-year-old man after sple-nectomy for trauma. In arterial phase of CT scan-ning (A), low-density ring (arrow) and blood vessels (short arrow) from abdominal aortic were visible in flat round nodule in right posterior lobe of liver. There were long T1 (B) and long T2 (C) ring around the nodules (arrow).

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3A-C). Homogeneous enhancement was shown in portal venous phase with CT values of 92.2-115.6 HU, which were higher than arterial phase. The decline degree of enhancement was significant in delayed phase with CT values of 67.5-83.7 HU (Figure 4A-C). The enhanced features of MRI were similar to CT (Figure 5A-C).

Radionuclide imaging

Strong radioactive concentrations in nodules were detected in splenic recess, tail of the pan-creas and the surface of right liver with clear boundary and homogeneous nuclides (Figure 6).

Surgical pathology

There were capsules in nodules. The sections of nodules were dark red or beige, and the nod-ules were soft and friable. Thick fibrous tissue capsules were covered on the edge of lesions,

and there were no significant muscle tissue and elastic fibers. Organizational structure in nodules were similar to spleen, which was mainly consisted of red pulp with hemostasis. There was white pulp consisted of dense lym-phocytes, too. Lymphatic sheath and splenic nodules were formed by parts dense lympho-cytes around the small arteries. The structure of white pulp in part region was incomplete. So the structure of hilus of spleen was not seen.

Discussion

In 1910, Von Kuttner first proposed the con-cept of splenic implantation after splenic trau-ma. In 1912, Von StenbenRouc first proved the existence of traumatic heterotopic spleen by animal model. In animal experiment, free spleen tissue could be implanted and survive in any part of the abdominal cavity. Regenerated tissue didn’t mean all cells, which only means undifferentiated reticular cells, and ischemic

Figure 4. The same patient of Figure 2. In the ar-terial phase (A) of CT scanning, inhomogeneous enhancement was visible in tail of the pancreas, continuous homogeneous enhancement was vis-ible in portal venous phase (B), and the decline degree of enhancement was significant in de-layed phase (C).

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necrosis would happen to other kind of cells. Once the scaffolds consisted of reticulocytes

and fibrous tissues were formed, the cells would differentiate into endothelial sinus, capil-

Figure 5. The same patient of Figure 3. In MRI scanning, inhomogeneous enhancement was visible in the arterial phase (A), continu-ous homogeneous enhancement was visible in portal venous phase (B), and the decline degree of enhancement was significant in de-layed phase (C).

Figure 6. The same patient of Figure 1. Radioactive concentrations were visible in tail of the pancreas, spleen fossa and the surface of right liver with clear boundary and homogeneous nuclides.

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laries, and lymphocytes, and finally form spleen tissues. These spleen tissues had the ability of phagocytosis of spleen.

Most patients with spleen planting do not have symptoms, and they are found by autopsy, abdominal surgery or imaging examination for other reasons [11]. There are few reports about the implanted spleen located in special area. If splenosis occurs in gastrointestinal tract, it will cause stomachache, intestinal obstruction and gastrointestinal bleeding [12, 13]. If splenosis occurs in female pelvic cavity, it will cause chronic pelvic pain, dysmenorrheal and deep sexual intercourse pain [14, 15]. When the tis-sue of spleen implantation and organ are close-ly related, it is easy to misdiagnose as tumors and result in clinical misdiagnosis [7]. Splenosis is a compensatory behavior when the body is free from spleen and another form of ectopic spleen. Arroja [12] et al. reported that spleen implanted nodules had compensation function and proliferative function. The common fatal complication after splenectomy was over-whelming infection, and the longest interval time was 40 years, which indicated that patients without spleen might have a lifetime risk of overwhelming infection [2, 16]. For patients had no symptoms, they were suggest-ed not to receive treatment, which needed defi-nite preoperative diagnosis and differentiate from benign and malignant tumors and acces-sory spleen.

The number of splenic implanted nodules can range from one to hundreds. Even only single nodule was found by imaging examination, there were a large number of dark red inflam-matory nodules with a size of soybeans distrib-uted in the peritoneum [17, 18]. It is common in splenic recess, and it also can be seen in the tail of pancreas and the right liver. Because the splenic implanted nodules do not have sepa-rated blood supply, so the diameter of 94.57% of the nodules is less than 3 cm [3]. On CT and MRI scanning, the density and signal were simi-lar to normal spleen. The nodules were homo-geneous and soft. Homogeneous or inhomoge-neous enhancement was shown in the arterial phase, continuous homogeneous enhance-ment was shown in portal venous phase, and the decline degree of enhancement was signifi-cant in delayed phase. If the scanning time in arterial phase was appropriate, plaque-like enhancement could be seen, and the enhanced

characteristics was the same as normal spleen, which were consistent with previous reports [2, 3, 6, 14, 17, 18].

Accessory splenosis usually single, and the sit-uation of more than six is rare [19]. It has big size and locates in mesangium surrounding the spleen. The shape is oval with clear boundary. It has one hilus of spleen and thick capsule. Blood supply is supported by the splenic artery. Splenosis is usually multiple and small [20]. The diameter is usually less than 3 cm. It can locate in internal and external of the abdominal cavity, and the spleen tissue debris can distrib-ute to anywhere. When the growing space is limited by surrounding structures, the shape can be variable. There is no hilus of spleen. It has fibrous capsule separated from adjacent organs. A number of blood vessels through thin pseudocapsule can be seen. The difference between accessory spleen and splenosis is that splenosis is almost associated with spleen trauma.

In conclusion, for patients who has splenic trau-ma or splenectomy, the possibility of splenosis should be considered once the homogeneous soft mass with similar density, signal and enhanced characteristics to spleen is found in abdominal cavity. It is important to know the history and imaging characteristics to avoid unnecessary surgeries. 99mTc isotope scanning and percutaneous puncture of the mass will help to diagnose.

Disclosure of conflict of interest

None.

Address correspondence to: Dr. Jianhua Wang, De- partment of Radiology, The Affiliated Hospital of Medical College of Ningbo University, Ningbo 3150- 20, China. Tel: +86-13586582317; E-mail: wangji- anhua573@163.com

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