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Everything you need to know about Computed Tomography (CT) & CT Scanning

Imaging Pearls ❯ Spleen ❯ Accessory Spleen and Splenules

  
  • Background: Identification of incidental pancreatic lesions is increasing because of advancements in imaging. Diagnosis remains a challenge for clinicians, with intrapancreatic accessory spleens (IPAS) posing a unique dilemma. IPAS are frequently resected because of inability to exclude alternate diagnoses, subjecting patients to unnecessary risk. The purpose of this study was to examine our institutional experience with IPAS and develop a multidisciplinary algorithm to improve preoperative diagnosis.
    Conclusions: Incidental pancreatic lesions like IPAS remain a diagnostic challenge for clinicians. Employing a diagnostic algorithm as proposed may aid in the distinction of malignant and premalignant pathology and prevent unwarranted pancreatic resections.
    Pancreatic Incidentalomas: A Management Algorithm for Identifying Ectopic Spleens
    Baugh KA et al.
    J Surg Res. 2019 Apr;236:144-152
  • “Ten patients of 303 patients who underwent a distal pancreatectomy were identified with a final pathology of IPAS. The average age was 54 y, 80% were white, and 60% were male. Lesions ranged in size from 7 mm to 5.1 cm in largest diameter (mean 2.2 cm). Lesions were described as round, well-marginated, and enhancing masses within the pancreatic tail. Preoperative workup was variable in terms of imaging and laboratory testing. Diagnostic workups were examined and combined with multidisciplinary input to create a diagnostic algorithm.”
    Pancreatic Incidentalomas: A Management Algorithm for Identifying Ectopic Spleens
    Baugh KA et al.
    J Surg Res. 2019 Apr;236:144-152
  • “IPAS are the result of splenic tissue buds failing to fuse during embryologic development and are quite common, found in 10%-20% of individuals. Accessory splenic tissue is usually asymptomatic and found incidentally with the most common location in the splenic hilum. However, 10%-15% are found in the pancreatic tail where they pose a diagnostic predicament.”
    Pancreatic Incidentalomas: A Management Algorithm for Identifying Ectopic Spleens
    Baugh KA et al.
    J Surg Res. 2019 Apr;236:144-152
  • Pancreatic Incidentalomas: A Management Algorithm for Identifying Ectopic Spleens Baugh KA et al. J Surg Res. 2019 Apr;236:144-152
  • On CT, IPAS appears as solid heteroge- neously enhancing masses, size averages 1-3 cm, and most commonly within 3 cm of the tail of the pancreas. Similarly, 90% of our patients had an enhancing distal mass with a mean maximum diameter less than 3 cm. The attenuation of accessory splenic tissue is similar to the spleen on arterial and venous phases, which was commented on in only two of the initial CT reports.
    Pancreatic Incidentalomas: A Management Algorithm for Identifying Ectopic Spleens
    Baugh KA et al.
    J Surg Res. 2019 Apr;236:144-152
  • “The heterogeneous enhancement on arterial phase is secondary to the differences in rate of blood flow between the red pulp and the white pulp of the spleen. Nonfunctioning PNETs are also hyperenhancing lesions on CT but with uniform or ring-like enhancement and greater enhancement on the venous phase.”
    Pancreatic Incidentalomas: A Management Algorithm for Identifying Ectopic Spleens
    Baugh KA et al.
    J Surg Res. 2019 Apr;236:144-152
  • “Metastatic disease represents 2%-5% of all malignant pancreatic tumors and usually arises from renal cell carcinoma, non-small cell lung cancer, and gastrointestinal carcinoma. Renal cell carcinoma usually presents as an enhancing lesion, whereas the other two are usually hypoattenuating but all typically correlate with the discovery of a primary tumor on CT.”
    Pancreatic Incidentalomas: A Management Algorithm for Identifying Ectopic Spleens
    Baugh KA et al.
    J Surg Res. 2019 Apr;236:144-152
  • ”The octreoscan is 70%-95% sensitive for detecting PNETs with somatostatin receptors. However, not all PNETs have somatostatin receptors; therefore, a negative octreotide scan does not rule out PNETs. In addition, lymphocytes can also display somatostatin receptors on their surface and cause uptake of the radiolabeled analog creating a false positive. One of the two IPAS patients in our series had a false positive octreotide scan; this displays the challenges that persist in diagnosing incidental pancreatic lesions.”
    Pancreatic Incidentalomas: A Management Algorithm for Identifying Ectopic Spleens
    Baugh KA et al.
    J Surg Res. 2019 Apr;236:144-152
  • “Diagnosis of incidental distal pancreatic solid lesions like IPAS creates significant difficulty for pancreas surgeons. Our algorithm provides needed structure to the work up. Although this is designed to rule out IPAS, this algorithm can be used as a starting point for the work up of any incidentally found pancreatic mass. In the past, the work up of incidentally found lesions led to the development of useful guidelines in the adrenal gland. Therefore, establishment of protocols like the one proposed for pancreatic lesions may aid in the development of future guidelines for the pancreas.”
    Pancreatic Incidentalomas: A Management Algorithm for Identifying Ectopic Spleens
    Baugh KA et al.
    J Surg Res. 2019 Apr;236:144-152
  • “Work up of an incidental pancreatic solid lesion remains a challenge, especially for the diagnosis of IPAS. Successful diagnosis will require a strong index of suspicion, a multi- disciplinary approach, and the use of the proposed algorithm. In time, this may aid clinicians in the distinction between benign IPAS, which requires no further action and a lesion requiring resection.”
    Pancreatic Incidentalomas: A Management Algorithm for Identifying Ectopic Spleens
    Baugh KA et al.
    J Surg Res. 2019 Apr;236:144-152
  • "Splenosis is the benign acquired condition of heterotopic autotransplantation of splenic tissue in another anatomic compartment of the body after splenic rupture, usually either traumatic or iatrogenic. It is often found incidentally, but rarely it can present symptomatically. Splenosis most frequently occurs in the abdominal and pelvic cavities, but it has also been described in numerous other locations throughout the body. Radiographically, splenosis can mimic various pathologic entities, including primary malignancy or metastatic disease."
    CT of Splenosis: Patterns and Pitfalls
    Spencer T. Lake, Pamela T. Johnson, Satomi Kawamoto, Ralph H. Hruban, Elliot K. Fishman
     AJR 2012; 199:W686-W693
  • "The splenic tissue present in splenosis is active, as evidenced by the absence of Howell-Jolly bodies, Heinz bodies, and other erythrocyte abnormalities in the peripheral smears of many asplenic patients with splenosis. Therefore, nuclear scintigraphy using heat- damaged RBCs tagged with technetium-99 is currently the diagnostic tool of choice because of the high uptake of damaged erythrocytes by this ectopic splenic tissue."
    CT of Splenosis: Patterns and Pitfalls
    Spencer T. Lake, Pamela T. Johnson, Satomi Kawamoto, Ralph H. Hruban, Elliot K. Fishman
     AJR 2012; 199:W686-W693
  • "In 25% of thoracic splenosis cases, chest CT shows a solitary pleura-based nodule, and multiple nodules are seen in the remaining 75% of cases. Nodule attenuation reflects that of normal splenic tissue. The splenic implants can easily be confused with other processes including primary or metastatic tumor or infection particularly if the abdomen is not imaged to disclose the absence of the spleen."
    CT of Splenosis: Patterns and Pitfalls
    Spencer T. Lake, Pamela T. Johnson, Satomi Kawamoto, Ralph H. Hruban, Elliot K. Fishman
     AJR 2012; 199:W686-W693
  • "Splenosis in the abdominal or pelvic cavity is thought to occur in as many as 65% of cases of splenic rupture. The most frequent locations include the greater omentum , small-bowel serosa, parietal peritoneum, and undersurface of the diaphragm .Once splenosis implants have been identified, careful evaluation may disclose additional implants throughout the peritoneum; the implants can be widespread."
    CT of Splenosis: Patterns and Pitfalls
    Spencer T. Lake, Pamela T. Johnson, Satomi Kawamoto, Ralph H. Hruban, Elliot K. Fishman
     AJR 2012; 199:W686-W693
  • " The average time between the inciting trauma and abdominal or pelvic splenosis is 10 years, although splenosis has been found to occur in as few as 5 months after trauma. Although abdominal splenosis is frequently asymptomatic, it can present with hemorrhage, pain secondary to infarction or torsion, or obstruction of the intestinal or urinary tract."
    CT of Splenosis: Patterns and Pitfalls
    Spencer T. Lake, Pamela T. Johnson, Satomi Kawamoto, Ralph H. Hruban, Elliot K. Fishman
     AJR 2012; 199:W686-W693
  • "Splenic nodules in the pancreas can represent either intrapancreatic accessory spleen or splenosis, the latter of which is rare. These entities must be differentiated from pancreatic malignancy-specifically, pancreatic neuroendocrine (islet) tumor or metastatic disease if the patient has a primary malignancy elsewhere. On CT, the diagnosis of intrapancreatic splenic tissues should be considered when a well-defined nodule with enhancement paralleling that of the spleen is identified in the pancreatic tail region, particularly along the dorsal surface."
    CT of Splenosis: Patterns and Pitfalls
    Spencer T. Lake, Pamela T. Johnson, Satomi Kawamoto, Ralph H. Hruban, Elliot K. Fishman
     AJR 2012; 199:W686-W693
  • "Splenosis can present with pelvic nodules, which may mimic metastases as well as other entities in women including endometriosis, ovarian masses, and uterine and cervical masses. These nodules may present with pelvic pain, but they are most frequently asymptomatic . Reports of pelvic involvement have included retrovesical and pararectal masses ."
    CT of Splenosis: Patterns and Pitfalls
    Spencer T. Lake, Pamela T. Johnson, Satomi Kawamoto, Ralph H. Hruban, Elliot K. Fishman
     AJR 2012; 199:W686-W693
  • "In patients with a history of splenic trauma or splenectomy, splenosis can arise through- out the abdominal or pelvic cavity in addition to the chest, subcutaneous tissues, and other less common locations. This pictorial essay illustrates many of the possible locations and CT appearances of splenosis to prompt con- sideration of this diagnosis in the appropriate clinical setting"
    CT of Splenosis: Patterns and Pitfalls
    Spencer T. Lake, Pamela T. Johnson, Satomi Kawamoto, Ralph H. Hruban, Elliot K. Fishman
     AJR 2012; 199:W686-W693
  • “CT can be used to differentiate between IPAS and PanNETwith good specificity and sensitivity. The IPAS mirrors the spleen’s enhancement and is usually located along the dorsal surface of the pancreas.”
    Intrapancreatic Accessory Spleen: Possibilities of Computed Tomography in Differentiation From Nonfunctioning Pancreatic Neuroendocrine Tumor
    Coquia SF,Kawamoto S, Hruban RH, Fishman EK
    J Comput Assist Tomogr 2014 (in press)
  • “Although not statistically significant, several other findings are also helpful to differentiate IPAS and neuroendocrine tumors. All IPASs in this study were located at the tip or within 3 cm of the tip of the tail of the pancreas. Therefore, if an enhancing mass is een more than several centimeters from the tip of the tail of the pancreas, it is less likely to represent IPAS and more likely a neuroendocrine tumor.”
    Intrapancreatic Accessory Spleen: Possibilities of Computed Tomography in Differentiation From Nonfunctioning Pancreatic Neuroendocrine Tumor
    Coquia SF,Kawamoto S, Hruban RH, Fishman EK
    J Comput Assist Tomogr 2014 (in press)
  • “ In conclusion, CT can be used to differentiate between IPASs and PanNETs with a high degree of sensitivity and specificity. Specific findings on CT are more prevalent with IPASs and can help increase diagnostic conf idence. These f indings include a lesion that is not completely embedded in the pancreatic parenchyma, a lesion that is located along the dorsal surface of the pancreas, a lesion that shows heterogeneous enhancement at the arterial phase, and a lesion that has the same degree of en- hancement of the spleen at the venous phase.”
    Intrapancreatic Accessory Spleen: Possibilities of Computed Tomography in Differentiation From Nonfunctioning Pancreatic Neuroendocrine Tumor
    Coquia SF,Kawamoto S, Hruban RH, Fishman EK
    J Comput Assist Tomogr 2014 (in press)
  • “The reader should look for enhancement of the IPAS matching the enhancement pat- tern of the spleen on multiphase CT examination. Furthermore, routine evaluation of the splenic vein should be performed with each lesion as occlusion of the vein has been associated with non- functioning PanNETs.”
    Intrapancreatic Accessory Spleen: Possibilities of Computed Tomography in Differentiation From Nonfunctioning Pancreatic Neuroendocrine Tumor
    Coquia SF,Kawamoto S, Hruban RH, Fishman EK
    J Comput Assist Tomogr 2014 (in press)
  • “In cases where the reader finds the lesion as indeterminate, although most were ultimately PanNETs in our study, given the associated decline in overall reader specificity seen in our study, the CT reader should recommend confirmatory testing such as 99mTc-labeled heat-damaged red blood cell scintigraphy or MRI rather than an observation with fine needle aspiration as needed for confirmatio.”
    Intrapancreatic Accessory Spleen: Possibilities of Computed Tomography in Differentiation From Nonfunctioning Pancreatic Neuroendocrine Tumor
    Coquia SF,Kawamoto S, Hruban RH, Fishman EK
    J Comput Assist Tomogr 2014 (in press)
  • “After traumatic splenic injury or splenectomy, small isolated spleens may develop. These implants are not limited to the left upper quadrant, and splenosis in other locations can mimic other pathologic entities. This pictorial essay presents the range of appearances of intraabdominal and pelvic splenosis.”
    CT of splenosis: patterns and pitfalls.
    Lake ST, Johnson PT, Kawamoto S, Hruban RH, Fishman EK.
    AJR 2012 Dec;199(6)W686-93
  • “ In addition to conventional morphologic MR imaging, DW (diffusion weighted) imaging can be used as a tool for differentiating intrapancreatic accessory spleen (IPAS) from solid pancreatic tumors.”
    Differentiation of an Intrapancreatic Accessory Spleen from a Small (<3-cm) Solid Pancreatic Tumor: Value of Diffusion-weighted MR Imaging
    Jang KM et al
    Radiology 2013; 268:159-167
  • “The diagnosis and differentiation of intrapancreatic accessory spleen from a solid pancreatic tumor by using visual assessment of similarity between pancreatic lesions and spleen on diffusion weighted images yields high diagnostic accuracy (90-95%), sensitivity (95-100%), specificity (86-91%), positive predictive value (86-91%) and negative predictive value (95-100%).”
    Differentiation of an Intrapancreatic Accessory Spleen from a Small (<3-cm) Solid Pancreatic Tumor: Value of Diffusion-weighted MR Imaging
    Jang KM et al
    Radiology 2013; 268:159-167
  • Intrapancreatic Accessory Spleen: CT Findings
    CT attenuation and enhancement pattern
    - Similar enhancement on noncontrast and postcontrast scans
    - Arterial phase enhancement is similar to the spleen including the serpiginous pattern of enhancement
  • Intrapancreatic Accessory Spleen: Differential Dx
    - Neuroendocrine tumor (NETs)
    - Metastatic renal cell carcinoma to the pancreas
    - Splenic artery aneurysm
  • “ However, when it remains difficult to exclude the other diagnosis, 99m-Tc labeled HDRBC scintigraphy or SPIO-enhanced MR imaging can be used to confirm the diagnosis of IPAS, with the caveats described above.”
    Intrapancreatic accessory spleen: CT appearance and differential diagnosis
    Kawamoto S, Johnson PT, Hull H, Cameron JL, Hruban RH, Fishman EK
    Abdom Imaging (2012)37:812-827
  • "Typically, accessory spleens appear on CT scans as well marginated, round masses that are smaller than 2 cm and enhance homogeneously on contrast-enhanced images. When accessory spleens are smaller than 1 cm, their attenuation may be lower than that of the spleen because of partial volume effects."

    CT Features of the Accessory Spleen
    Mortele KJ et al.

  • "Typically, accessory spleens appear on CT scans as well marginated, round masses that are smaller than 2 cm and enhance homogeneously on contrast-enhanced images."

    CT Features of the Accessory Spleen
    Mortele KJ et al.
    AJR 2004; 183:1653-1657
  • Accessory Spleen: Facts

    "Differentiation from a hypervascular pancreatic neoplasm (e.g. islet cell tumor) is, therefore sometimes challenging."

    CT Features of the Accessory Spleen
    Mortele KJ et al.
  • Accessory Spleen: Facts
    - Present in 16% of patients undergoing contrast enhanced CT
    - Usually 2 cm or less in size
    - Usually enhance equal to the normal spleen but lesions under 1 cm may not
    - May simulate pancreatic, renal or adrenal pathology
© 1999-2019 Elliot K. Fishman, MD, FACR. All rights reserved.