000 Splenosis

Etymology
The term “splenosis” originates from the Greek word “splēn,” meaning spleen, and the suffix “-osis,” indicating a process, referring to the autotransplantation of splenic tissue.

AKA

  • Ectopic splenic implants
  • Splenic autotransplantation

What is it?
Splenosis is the process of autotransplantation and revascularization of splenic tissue fragments, typically occurring after splenic trauma or splenectomy. The tissue establishes ectopically in the peritoneal or extraperitoneal cavities and can partially restore splenic functions.

Caused by:

  • Most common:
    Traumatic rupture of the spleen or splenectomy leading to dissemination of splenic tissue (1, 3, 6).
  • Other causes (categorized):
    • Inflammation/Immune: Not applicable.
    • Infection: Rare association with secondary complications.
    • Neoplasm: Rarely associated with misdiagnosis as metastatic disease (4, 5).
    • Mechanical: Splenic tissue displaced via vascular or peritoneal pathways (2, 8).
    • Trauma: Leading cause, accounting for most cases (1, 3).
    • Metabolic: Not applicable.
    • Circulatory: Revascularization mediated by angiogenesis allows ectopic tissue survival (6).
    • Inherited Congenital: Not applicable.
    • Iatrogenic: Splenectomy or intraoperative dissemination of splenic fragments (3).
    • Idiopathic: Rare and unreported.

Resulting in:

  • Formation of vascularized ectopic splenic nodules.
  • Partial immune restoration.
  • Risk of misdiagnosis as malignant neoplasms or metastatic disease.

Structural changes:

  • Parts: Contains both red and white pulp, resembling normal splenic histology (5).
  • Size: Varies; nodules range from millimeters to several centimeters (6).
  • Shape: Nodular or oval.
  • Position: Frequently in the peritoneal cavity, but may also appear in the thoracic cavity, liver, or subcutaneous tissue (3, 7).
  • Character: Vascularized nodules resembling splenic tissue.
  • Time: Develops weeks to months post-trauma or surgery.

Pathophysiology
Splenic tissue fragments survive due to their ability to promote angiogenesis and adapt to ectopic environments. Angiogenic factors and extracellular matrix remodeling play a critical role (1, 5). Functional restoration is partial, and the immune function provided may not prevent overwhelming post-splenectomy infection (OPSI) (2, 6).

Other relevant basic science applications

  • Biochemistry: Tissue viability is supported by angiogenesis and extracellular matrix adaptation (1).
  • Immunology: Ectopic tissue provides limited immune function, including erythrocyte filtration (2).
  • Pathology: Histological findings include red and white pulp, similar to normal spleen (5).

Diagnosis:

  • Clinical: Often asymptomatic, discovered incidentally. May present with abdominal pain, obstruction, or gastrointestinal bleeding (9).
  • Radiology: Imaging is essential for identification and differentiation from neoplasms.
  • Labs: Howell-Jolly bodies may persist, indicating incomplete immune restoration (2).

Radiology and Imaging:

  • X-Ray:
    • Findings: Rarely diagnostic but may show calcified nodules.
    • Associated Findings: None specific.
  • X-ray/Fluoroscopy/Barium:
    • Findings: May reveal mass effects or displacement.
    • Associated Findings: Mimics gastrointestinal stromal tumors (7).
  • CT:
    • Findings: Hypoattenuating nodules with homogenous enhancement on post-contrast imaging (4, 6).
    • Associated Findings: Mimics metastatic lesions or abscesses.
  • MRI:
    • Findings: Nodules appear hypointense on T1-weighted images and hyperintense on T2-weighted images (6).
    • Associated Findings: Differentiation from other abdominal masses.
  • US:
    • Findings: Hypoechoic nodules with vascular flow on Doppler (7).
    • Associated Findings: Mimics lymphadenopathy.
  • Other relevant Imaging Modalities:
    • PET/CT: May show uptake mimicking neoplastic lesions.
    • NM (Scintigraphy): Gold standard using Tc-99m heat-damaged red blood cells for diagnosis (8).

Other Diagnostic Procedures:

  • Histopathology confirms splenic tissue with red and white pulp (5).

Differential Diagnosis:

  • Most common:
    • Metastatic disease (4, 6).
  • Other categories:
    • Inflammation/Immune: None specific.
    • Infection: None specific.
    • Neoplasm: Lymphoma, gastrointestinal stromal tumors.

Recommendations:

  • Use NM scintigraphy for definitive diagnosis (8).
  • Avoid invasive procedures without diagnostic confirmation.

Key Points and Pearls:

  • Splenosis arises from autotransplantation of splenic tissue post-trauma or surgery (1).
  • Scintigraphy using Tc-99m heat-damaged red blood cells is the diagnostic gold standard (8).

 

References

Basic Science

  1. Experimental Splenosis in the Liver and Lung Spread Through the Vasculature
    Seguchi S, Yue F, Asanuma K, Sasaki K
    Cell and Tissue Research. 2015;360(2):287-96.
  2. Splenosis and Sepsis: The Born-Again Spleen Provides Poor Protection
    Connell NT, Brunner AM, Kerr CA, Schiffman FJ
    Virulence. 2011;2(1):4-11.
  3. Splenosis: Autotransplantation of Splenic Tissue
    Fleming CR, Dickson ER, Harrison EG
    The American Journal of Medicine. 1976;61(3):414-9.
  4. Unusual Subcutaneous Splenosis Occurring in a Gunshot Wound Scar: Pathology and Immunohistochemical Identification
    Yeh CJ, Chuang WY, Kuo TT
    Pathology International. 2006;56(6):336-9.
  5. The Histological Features of Splenosis
    Carr NJ, Turk EP
    Histopathology. 1992;21(6):549-53.

Imaging and Radiology

General

  1. A Case of Intrahepatic Splenosis: Usefulness of Splenic Scintigraphy
    Kawada S, Ichikawa T, Ueda H, et al
    Abdominal Radiology (New York). 2020;45(7):2274-2278.
  2. Intrahepatic and Intra-Abdominal Splenosis: A Case Report and Review of Literature
    Ananthan K, Yusuf GT, Kumar M
    World Journal of Hepatology. 2019;11(12):773-779.
  3. Intra-Abdominal Splenosis Mimicking Metastatic Cancer
    Short NJ, Hayes TG, Bhargava P
    The American Journal of the Medical Sciences. 2011;341(3):246-9.
  4. Abdominal and Pelvic Splenosis: Atypical Findings, Pitfalls, and Mimics
    Smoot T, Revels J, Soliman M, et al
    Abdominal Radiology (New York). 2022;47(3):923-947.
  5. CT of Splenosis: Patterns and Pitfalls
    Lake ST, Johnson PT, Kawamoto S, Hruban RH, Fishman EK
    AJR. American Journal of Roentgenology. 2012;199(6):W686-93.

Other Imaging Modalities

  1. Hepatic Splenosis: Rare Yet Important – A Case Report and Literature Review
    Luo X, Zeng J, Wang Y, et al
    The Journal of International Medical Research. 2019;47(4):1793-1801.
  2. Contrast-Enhanced Ultrasonographic Imaging of Hepatic Splenosis: A Case Report
    Zhong X, Yang L, Huang J, et al
    Medicine. 2021;100(3):e24243.
  3. Improved Detection of Splenosis in Patients With Haematological Disorders: The Role of Combined Transmission-Emission Tomography
    Horger M, Eschmann SM, Lengerke C, et al
    European Journal of Nuclear Medicine and Molecular Imaging. 2003;30(2):316-9.

Clinical

  1. Splenosis With Lower Gastrointestinal Bleeding Mimicking Colonical Gastrointestinal Stromal Tumour
    Xiao SM, Xu R, Tang XL, et al
    World Journal of Surgical Oncology. 2017;15(1):78.
  2. Small Bowel Obstruction Due to Splenosis 30 Years After Splenectomy
    El-Helou E, Alimoradi M, Sabra H, et al
    Annals of the Royal College of Surgeons of England. 2020;102(9):e1-e3.
  3. Splenosis Presenting as Occult Gastrointestinal Bleeding
    Sikov WM, Schiffman FJ, Weaver M, et al
    American Journal of Hematology. 2000;65(1):56-61.
  4. Thoracic Splenosis Mimicking a Pleuropneumonia: A Case Report
    Baldolli A, Coeuret S, Le Pennec V, Agostini D, Verdon R
    Medicine. 2017;96(29):e7552.
  5. A Case of Splenosis After Laparoscopic Splenectomy
    Sato M, Motohiro T, Seto S, et al
    Pediatric Surgery International. 2007;23(10):1019-21