Imaging of the Spleen

Introduction

Imaging modalities

The common radiologic modalities used to evaluate the spleen Spleen The spleen is the largest lymphoid organ in the body, located in the LUQ of the abdomen, superior to the left kidney and posterior to the stomach at the level of the 9th-11th ribs just below the diaphragm. The spleen is highly vascular and acts as an important blood filter, cleansing the blood of pathogens and damaged erythrocytes. Spleen: Anatomy are the following:

• Ultrasonography (US)
• CT
• MRI

Preparation and orientation Orientation Awareness of oneself in relation to time, place and person. Psychiatric Assessment

• Prior to the interpretation of any image, the physician should take certain preparatory steps. The same systematic approach should be followed every time.:
  • Confirm the name of the patient, the date, and the time on all images.
  • Obtain knowledge of the patient’s medical history and physical exam.
  • Confirm the appropriate exam and technique for the suspected or confirmed pathology at hand Hand The hand constitutes the distal part of the upper limb and provides the fine, precise movements needed in activities of daily living. It consists of 5 metacarpal bones and 14 phalanges, as well as numerous muscles innervated by the median and ulnar nerves. Hand: Anatomy. 
  • Compare any available images of the same area taken in the same modality.
• Determine the orientation Orientation Awareness of oneself in relation to time, place and person. Psychiatric Assessment of the image:
  • Right or left marker on X-ray X-ray Penetrating electromagnetic radiation emitted when the inner orbital electrons of an atom are excited and release radiant energy. X-ray wavelengths range from 1 pm to 10 nm. Hard x-rays are the higher energy, shorter wavelength x-rays. Soft x-rays or grenz rays are less energetic and longer in wavelength. The short wavelength end of the x-ray spectrum overlaps the gamma rays wavelength range. The distinction between gamma rays and x-rays is based on their radiation source. Pulmonary Function Tests
  • In the United States, standard exam views place a marker (dot) to the patient’s right.
  • For CT/MRI, on an axial Axial Computed Tomography (CT) view, the image is sliced and viewed from inferior to superior (as if you are looking from the patient’s feet up).

Ultrasonography

Overview

• Medical indications:
  • Emergency care: trauma with concern for splenic injury
  • Routine care:
    • Signs and symptoms of splenomegaly Splenomegaly Splenomegaly is pathologic enlargement of the spleen that is attributable to numerous causes, including infections, hemoglobinopathies, infiltrative processes, and outflow obstruction of the portal vein. Splenomegaly
    • Screening Screening Preoperative Care of patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship with cirrhosis Cirrhosis Cirrhosis is a late stage of hepatic parenchymal necrosis and scarring (fibrosis) most commonly due to hepatitis C infection and alcoholic liver disease. Patients may present with jaundice, ascites, and hepatosplenomegaly. Cirrhosis can also cause complications such as hepatic encephalopathy, portal hypertension, portal vein thrombosis, and hepatorenal syndrome. Cirrhosis
  • Monitoring: known splenomegaly Splenomegaly Splenomegaly is pathologic enlargement of the spleen that is attributable to numerous causes, including infections, hemoglobinopathies, infiltrative processes, and outflow obstruction of the portal vein. Splenomegaly 
• Advantages:
  • Low cost 
  • No radiation Radiation Emission or propagation of acoustic waves (sound), electromagnetic energy waves (such as light; radio waves; gamma rays; or x-rays), or a stream of subatomic particles (such as electrons; neutrons; protons; or alpha particles). Osteosarcoma dose 
  • Widespread availability
  • Fast
• Disadvantages:
  • Poor resolution 
  • Narrow field of view
  • The patient must hold still for the image.
  • Technician dependent

Exam technique

• Positioning:
  • Patient:
    • Access to the leftward abdomen
    • Maximize contact between the patient’s skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions and the ultrasound probe Probe A device placed on the patient’s body to visualize a target Ultrasound (Sonography).
    • Supine or right lateral positioning with the left arm Arm The arm, or “upper arm” in common usage, is the region of the upper limb that extends from the shoulder to the elbow joint and connects inferiorly to the forearm through the cubital fossa. It is divided into 2 fascial compartments (anterior and posterior). Arm: Anatomy raised
  • Visualization:
    • The spleen Spleen The spleen is the largest lymphoid organ in the body, located in the LUQ of the abdomen, superior to the left kidney and posterior to the stomach at the level of the 9th-11th ribs just below the diaphragm. The spleen is highly vascular and acts as an important blood filter, cleansing the blood of pathogens and damaged erythrocytes. Spleen: Anatomy should be most superficial to the probe Probe A device placed on the patient’s body to visualize a target Ultrasound (Sonography), without other organs/bowel between the spleen Spleen The spleen is the largest lymphoid organ in the body, located in the LUQ of the abdomen, superior to the left kidney and posterior to the stomach at the level of the 9th-11th ribs just below the diaphragm. The spleen is highly vascular and acts as an important blood filter, cleansing the blood of pathogens and damaged erythrocytes. Spleen: Anatomy and ultrasound probe Probe A device placed on the patient’s body to visualize a target Ultrasound (Sonography).
    • An intercostal approach (usually in the 9th/10th intercostal spaces Intercostal spaces Chest Wall: Anatomy) and inviting the patient to take a deep breath Deep breath Respiratory Alkalosis are useful for better visualization.
• Depth and gain: 
  • Determines the field of view and echogenicity characteristics of the tissue
    • Ideally, should be such that the entire spleen Spleen The spleen is the largest lymphoid organ in the body, located in the LUQ of the abdomen, superior to the left kidney and posterior to the stomach at the level of the 9th-11th ribs just below the diaphragm. The spleen is highly vascular and acts as an important blood filter, cleansing the blood of pathogens and damaged erythrocytes. Spleen: Anatomy is visualized on the image without excess abdominal signal deep to the spleen Spleen The spleen is the largest lymphoid organ in the body, located in the LUQ of the abdomen, superior to the left kidney and posterior to the stomach at the level of the 9th-11th ribs just below the diaphragm. The spleen is highly vascular and acts as an important blood filter, cleansing the blood of pathogens and damaged erythrocytes. Spleen: Anatomy
  • Gain should be placed such that the splenic parenchyma is visualized without saturating out too much signal.

Interpretation and evaluation

• Size
  • Normal is < 12 cm (< 14 cm can be considered normal for taller people).
  • Massive splenomegaly Splenomegaly Splenomegaly is pathologic enlargement of the spleen that is attributable to numerous causes, including infections, hemoglobinopathies, infiltrative processes, and outflow obstruction of the portal vein. Splenomegaly is considered when the spleen Spleen The spleen is the largest lymphoid organ in the body, located in the LUQ of the abdomen, superior to the left kidney and posterior to the stomach at the level of the 9th-11th ribs just below the diaphragm. The spleen is highly vascular and acts as an important blood filter, cleansing the blood of pathogens and damaged erythrocytes. Spleen: Anatomy is > 18 cm in length.
• Echogenicity
  • Homogeneous in echotexture
  • Usually iso- or slightly more hyperechoic Hyperechoic A structure that produces a high-amplitude echo (lighter grays and white) Ultrasound (Sonography) relative to the liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy
  • More echogenic than normal renal cortex
• Position
  • Inferior to the left hemidiaphragm
  • Positioned adjacent to the pancreatic tail, left kidney, and left adrenal gland

Normal findings

Normal ultrasound appearance: 

• Crescent Crescent Rapidly Progressive Glomerulonephritis shaped
  • Outer margin: convex and smooth
  • Inner margin: concave and indented
• Echogenicity: homogeneous
  • Spleen Spleen The spleen is the largest lymphoid organ in the body, located in the LUQ of the abdomen, superior to the left kidney and posterior to the stomach at the level of the 9th-11th ribs just below the diaphragm. The spleen is highly vascular and acts as an important blood filter, cleansing the blood of pathogens and damaged erythrocytes. Spleen: Anatomy > liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy
  • Spleen Spleen The spleen is the largest lymphoid organ in the body, located in the LUQ of the abdomen, superior to the left kidney and posterior to the stomach at the level of the 9th-11th ribs just below the diaphragm. The spleen is highly vascular and acts as an important blood filter, cleansing the blood of pathogens and damaged erythrocytes. Spleen: Anatomy >>> kidney
• Longitudinal dimension: < 12 cm

Computed Tomography

Indication

• Medical indications:
  • Follow-up of suspicious ultrasound imaging:
    • Hypo-/ hyperechoic Hyperechoic A structure that produces a high-amplitude echo (lighter grays and white) Ultrasound (Sonography) lesions
    • Concern for vascular pathology
    • Contour deformities
  • Malignancy Malignancy Hemothorax:
    • Evaluation of spleen Spleen The spleen is the largest lymphoid organ in the body, located in the LUQ of the abdomen, superior to the left kidney and posterior to the stomach at the level of the 9th-11th ribs just below the diaphragm. The spleen is highly vascular and acts as an important blood filter, cleansing the blood of pathogens and damaged erythrocytes. Spleen: Anatomy size in lymphoproliferative disorders Lymphoproliferative disorders Disorders characterized by proliferation of lymphoid tissue, general or unspecified. Lymphocytosis
    • Detection of metastases 
    • Evaluation of lymph Lymph The interstitial fluid that is in the lymphatic system. Secondary Lymphatic Organs nodes 
  • Major trauma:
    • Evaluation of splenic parenchyma
    • Evaluation for splenic hemorrhage with or without active extravasation on delayed images
    • Concern for subtle pathology not seen on ultrasound
• Advantages:
  • Excellent anatomical detail resolution 
  • Structures can be seen in 3 dimensions
• Disadvantages: 
  • Involves high radiation Radiation Emission or propagation of acoustic waves (sound), electromagnetic energy waves (such as light; radio waves; gamma rays; or x-rays), or a stream of subatomic particles (such as electrons; neutrons; protons; or alpha particles). Osteosarcoma dose
  • The patient must hold still for the exam.
  • Expensive to perform

Exam technique

Standard CT scanning Standard CT scanning Imaging of the Liver and Biliary Tract:

• The patient lies supine on the table. 
• The table is moved into the CT scanner, which rotates around the patient.
• The patient is instructed to hold their breath and remain still for the duration of the scan (seconds).
• The exam can be done with or without IV or oral contrast.
• The timing of IV contrast dye can help direct radiology inquiry of certain areas of pathology:
  • A CT with IV contrast is typically performed in the portal venous phase, initially with another set of images at a delayed time point, to evaluate for active extravasation.

Interpretation and evaluation

Interpretation should follow a systematic and reproducible pattern:

• Review the patient’s history and physical exam.
• Achieve the ideal evaluation with a soft-tissue window/level (W:400 L:50).
• Compare to any available recent imaging of the interested area.
• Orient the image:
  • Axial Axial Computed Tomography (CT) images are seen as if looking from the patient’s feet up.
  • Sagittal Sagittal Computed Tomography (CT) and coronal Coronal Computed Tomography (CT) images are used to supplement the diagnosis.
• Identify landmark anatomical structures.
• Observe for “continuity” of parenchyma while scrolling through image slices.

Normal findings

Normal CT appearance: 

• Crescent-shaped structure
• Smooth borders
• Homogeneous, with attenuation values ranging between 40 and 60 HU HU Computed Tomography (CT)
• Slightly less dense than the liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy (about 10 HU HU Computed Tomography (CT) less)
• Contrast
  • Arterial (angiographic) phase: heterogeneous enhancement
  • Portal venous phase: homogeneous enhancement

Magnetic Resonance Imaging

Indication

• Medical indications:
  • Detailed evaluation of splenic lesions
    • Hemangiomas
    • Cysts Cysts Any fluid-filled closed cavity or sac that is lined by an epithelium. Cysts can be of normal, abnormal, non-neoplastic, or neoplastic tissues. Fibrocystic Change
    • Lymphoma Lymphoma A general term for various neoplastic diseases of the lymphoid tissue. Imaging of the Mediastinum
  • Vascular disease:
    • MRA MRA Imaging of the Heart and Great Vessels for splenic artery aneurysms
  • Evaluation of suspected splenules:
    • Intrapancreatic
    • Intraabdominal
• Advantages:
  • Provides higher level of imaging and detail of fluid, enhancement, and soft tissue Soft Tissue Soft Tissue Abscess
  • Can be used for evaluation of pregnant patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship
  • Used as adjunct to previous test, including US and CT
• Disadvantages:
  • Very expensive
  • Takes much longer to perform than an X-ray X-ray Penetrating electromagnetic radiation emitted when the inner orbital electrons of an atom are excited and release radiant energy. X-ray wavelengths range from 1 pm to 10 nm. Hard x-rays are the higher energy, shorter wavelength x-rays. Soft x-rays or grenz rays are less energetic and longer in wavelength. The short wavelength end of the x-ray spectrum overlaps the gamma rays wavelength range. The distinction between gamma rays and x-rays is based on their radiation source. Pulmonary Function Tests, US, or CT
  • Not suitable for all patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship:
    • Implants (particularly metal) distort the image.
    • Requires the patient to be in a loud, enclosed space
    • The patient must stay still in order to obtain adequate images.

Exam technique

• Positioning:
  • Supine on table
  • The table is advanced into the MRI scanner.
  • The patient is instructed to remain still for the scan.
• MRA MRA Imaging of the Heart and Great Vessels:
  • Used to examine blood vessels
  • Exams can be done with or without IV contrast.
  • Advancements have allowed medicine to create both 2D and 3D image reconstructions.
• Views:
  • T1-weighted scans: 
    • Tissues with high fat content (e.g., white matter White Matter The region of central nervous system that appears lighter in color than the other type, gray matter. It mainly consists of myelinated nerve fibers and contains few neuronal cell bodies or dendrites. Brown-Séquard Syndrome) appear bright/white.
    • Compartments filled with water (e.g., CSF) appear dark/black.
    • Post-contrast images are typically T1 weighted due to the intrinsic properties of gadolinium Gadolinium An element of the rare earth family of metals. It has the atomic symbol gd, atomic number 64, and atomic weight 157. 25. Its oxide is used in the control rods of some nuclear reactors. Magnetic Resonance Imaging (MRI).
  • T2-weighted scans: 
    • Compartments filled with water (CSF) appear bright/white.
    • Tissues with high fat content (e.g., white matter White Matter The region of central nervous system that appears lighter in color than the other type, gray matter. It mainly consists of myelinated nerve fibers and contains few neuronal cell bodies or dendrites. Brown-Séquard Syndrome) appear dark/black.
  • Diffusion-weighted images (DWIs) are important for splenic evaluation
    • Intrinsic diffusion Diffusion The tendency of a gas or solute to pass from a point of higher pressure or concentration to a point of lower pressure or concentration and to distribute itself throughout the available space. Diffusion, especially facilitated diffusion, is a major mechanism of biological transport. Peritoneal Dialysis and Hemodialysis restriction is present in spleen Spleen The spleen is the largest lymphoid organ in the body, located in the LUQ of the abdomen, superior to the left kidney and posterior to the stomach at the level of the 9th-11th ribs just below the diaphragm. The spleen is highly vascular and acts as an important blood filter, cleansing the blood of pathogens and damaged erythrocytes. Spleen: Anatomy tissue (bright on DWI DWI Imaging of the Head and Brain sequences).
    • Useful for evaluating intrapancreatic splenules
  • Images are oriented in 3-dimensional “slices”: 
    • Coronal Coronal Computed Tomography (CT) 
    • Sagittal Sagittal Computed Tomography (CT)
    • Axial Axial Computed Tomography (CT)

Interpretation and evaluation

Interpretation should follow a systematic and reproducible pattern:

• Review the patient’s history and physical exam.
• Compare to any available recent imaging of the interested area.
• Orient the image.
• Identify landmark anatomical structures.
• Observe for “continuity” of parenchyma and neighboring structures while scrolling through image slices

Normal findings

Normal MRI appearance: 

• Crescent-shaped structure
• Smooth borders
• Homogeneous 
• Intensity: 
  • T1 weighted: slightly less intense than the liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy
  • T2 weighted: more intense than the liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy
  • DWI DWI Imaging of the Head and Brain: Increased intensity
• Contrast:
  • Arterial phase: heterogeneous enhancement
  • Portal venous phase: homogeneous enhancement
  • Similar to CT pattern

Abnormal Findings

Splenomegaly Splenomegaly Splenomegaly is pathologic enlargement of the spleen that is attributable to numerous causes, including infections, hemoglobinopathies, infiltrative processes, and outflow obstruction of the portal vein. Splenomegaly

• The enlargement of the spleen Spleen The spleen is the largest lymphoid organ in the body, located in the LUQ of the abdomen, superior to the left kidney and posterior to the stomach at the level of the 9th-11th ribs just below the diaphragm. The spleen is highly vascular and acts as an important blood filter, cleansing the blood of pathogens and damaged erythrocytes. Spleen: Anatomy, which is usually not palpable on abdominal examination Abdominal examination The abdominal examination is the portion of the physical exam evaluating the abdomen for signs of disease. The abdominal examination consists of inspection, auscultation, percussion, and palpation. Abdominal Examination
• The most common causes include hematological diseases (e.g., chronic myeloid leukemia Chronic myeloid leukemia Chronic myeloid leukemia is a malignant proliferation of the granulocytic cell line characterized by a fairly normal differentiation. The underlying genetic abnormality is the Philadelphia chromosome, an abbreviated chromosome 22, resulting from reciprocal (9;22)(q34;q11) translocation. Chronic Myeloid Leukemia and chronic lymphocytic leukemia Chronic Lymphocytic Leukemia Chronic lymphocytic leukemia (CLL) is a hematologic malignancy characterized by excess production of monoclonal B lymphocytes in the peripheral blood. When the involvement is primarily nodal, the condition is called small lymphocytic lymphoma (SLL). The disease usually presents in older adults, with a median age of 70 years. Chronic Lymphocytic Leukemia ( CLL CLL Chronic lymphocytic leukemia (CLL) is a hematologic malignancy characterized by excess production of monoclonal B lymphocytes in the peripheral blood. When the involvement is primarily nodal, the condition is called small lymphocytic lymphoma (SLL). The disease usually presents in older adults, with a median age of 70 years. Chronic Lymphocytic Leukemia)), liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy disease and portal hypertension Hypertension Hypertension, or high blood pressure, is a common disease that manifests as elevated systemic arterial pressures. Hypertension is most often asymptomatic and is found incidentally as part of a routine physical examination or during triage for an unrelated medical encounter. Hypertension, glycogen storage diseases Glycogen Storage Diseases A group of inherited metabolic disorders involving the enzymes responsible for the synthesis and degradation of glycogen. In some patients, prominent liver involvement is presented. In others, more generalized storage of glycogen occurs, sometimes with prominent cardiac involvement. Benign Liver Tumors (e.g., Gaucher disease Gaucher disease Gaucher Disease (GD) is an autosomal recessive lysosomal storage disorder caused by a deficiency of glucocerebrosidase enzyme activity, resulting in accumulation of glucocerebroside in cells and certain organs. The disease is categorized into 3 types with variable clinical presentation. Gaucher Disease ( GD GD Gaucher disease (GD) is an autosomal recessive lysosomal storage disorder caused by a deficiency of glucocerebrosidase enzyme activity, resulting in accumulation of glucocerebroside in cells and certain organs. The disease is categorized into 3 types with variable clinical presentation. Gaucher Disease)), systemic diseases (e.g., sarcoidosis Sarcoidosis Sarcoidosis is a multisystem inflammatory disease that causes noncaseating granulomas. The exact etiology is unknown. Sarcoidosis usually affects the lungs and thoracic lymph nodes, but it can also affect almost every system in the body, including the skin, heart, and eyes, most commonly. Sarcoidosis, amyloidosis Amyloidosis Amyloidosis is a disease caused by abnormal extracellular tissue deposition of fibrils composed of various misfolded low-molecular-weight protein subunits. These proteins are frequently byproducts of other pathological processes (e.g., multiple myeloma). Amyloidosis, and collagen Collagen A polypeptide substance comprising about one third of the total protein in mammalian organisms. It is the main constituent of skin; connective tissue; and the organic substance of bones (bone and bones) and teeth (tooth). Connective Tissue: Histology diseases), and infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease (e.g., malaria Malaria Malaria is an infectious parasitic disease affecting humans and other animals. Most commonly transmitted via the bite of a female Anopheles mosquito infected with microorganisms of the Plasmodium genus. Patients present with fever, chills, myalgia, headache, and diaphoresis. Plasmodium/Malaria, leishmaniasis Leishmaniasis Leishmania species are obligate intracellular parasites that are transmitted by an infected sandfly. The mildest form is cutaneous leishmaniasis (CL), characterized by painless skin ulcers. The mucocutaneous type involves more tissue destruction, causing deformities. Visceral leishmaniasis (VL), the most severe form, presents with hepatosplenomegaly, anemia, thrombocytopenia, and fever. Leishmania/Leishmaniasis, and infectious Infectious Febrile Infant mononucleosis Mononucleosis Infectious mononucleosis (IM), also known as “the kissing disease,” is a highly contagious viral infection caused by the Epstein-Barr virus. Its common name is derived from its main method of transmission: the spread of infected saliva via kissing. Clinical manifestations of IM include fever, tonsillar pharyngitis, and lymphadenopathy. Mononucleosis (IM)).
• Can be detected on all imaging modalities:
  • Diffuse enlargement
  • Longitudinal axis Axis The second cervical vertebra. Vertebral Column: Anatomy > 12 cm 
  • >18 cm denotes massive splenomegaly Splenomegaly Splenomegaly is pathologic enlargement of the spleen that is attributable to numerous causes, including infections, hemoglobinopathies, infiltrative processes, and outflow obstruction of the portal vein. Splenomegaly

Splenic hematoma Hematoma A collection of blood outside the blood vessels. Hematoma can be localized in an organ, space, or tissue. Intussusception

• Collections of blood in the perisplenic space, although hemorrhage from the spleen Spleen The spleen is the largest lymphoid organ in the body, located in the LUQ of the abdomen, superior to the left kidney and posterior to the stomach at the level of the 9th-11th ribs just below the diaphragm. The spleen is highly vascular and acts as an important blood filter, cleansing the blood of pathogens and damaged erythrocytes. Spleen: Anatomy can extend beyond the splenic capsule Capsule An envelope of loose gel surrounding a bacterial cell which is associated with the virulence of pathogenic bacteria. Some capsules have a well-defined border, whereas others form a slime layer that trails off into the medium. Most capsules consist of relatively simple polysaccharides but there are some bacteria whose capsules are made of polypeptides. Bacteroides 
• The most common causes are trauma, a ruptured cyst, or a ruptured hemangioma Hemangioma A vascular anomaly due to proliferation of blood vessels that forms a tumor-like mass. The common types involve capillaries and veins. It can occur anywhere in the body but is most frequently noticed in the skin and subcutaneous tissue. Imaging of the Liver and Biliary Tract.
• Patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship will present with left upper LUQ quadrant pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways with or without symptoms of hypovolemia Hypovolemia Sepsis in Children if the volume of hemorrhage is large enough. 
• US:
  • Hypoechoic Hypoechoic A structure that produces a low-amplitude echo (darker grays) Ultrasound (Sonography) irregular structure
  • Subcapsular: peripheral location of perisplenic fluid signal
  • Intraparenchymal: irregular fluid signal within the body of the spleen Spleen The spleen is the largest lymphoid organ in the body, located in the LUQ of the abdomen, superior to the left kidney and posterior to the stomach at the level of the 9th-11th ribs just below the diaphragm. The spleen is highly vascular and acts as an important blood filter, cleansing the blood of pathogens and damaged erythrocytes. Spleen: Anatomy
• CT: best evaluated with multiphase CT Multiphase CT Computed Tomography (CT) (portal venous and delayed, usually)
  • Hypodense subcapsular mass Mass Three-dimensional lesion that occupies a space within the breast Imaging of the Breast: hematoma Hematoma A collection of blood outside the blood vessels. Hematoma can be localized in an organ, space, or tissue. Intussusception
  • Linear branching hypodensities
    • Zebra spleen Spleen The spleen is the largest lymphoid organ in the body, located in the LUQ of the abdomen, superior to the left kidney and posterior to the stomach at the level of the 9th-11th ribs just below the diaphragm. The spleen is highly vascular and acts as an important blood filter, cleansing the blood of pathogens and damaged erythrocytes. Spleen: Anatomy
    • Arterial phase
  • Inhomogeneous enhancement
    • Portal venous phase
  • Pseudoaneurysms and arteriovenous fistula Fistula Abnormal communication most commonly seen between two internal organs, or between an internal organ and the surface of the body. Anal Fistula (AVF)
    • Vascular injury

Splenic rupture Splenic rupture Splenic rupture is a medical emergency that carries a significant risk of hypovolemic shock and death. Injury to the spleen accounts for nearly half of all injuries to intra-abdominal organs. The most common reason for a rupture of the spleen is blunt abdominal trauma, specifically, motor vehicle accidents. Rupture of the Spleen

• A medical emergency that carries a significant risk of hypovolemic shock Shock Shock is a life-threatening condition associated with impaired circulation that results in tissue hypoxia. The different types of shock are based on the underlying cause: distributive (↑ cardiac output (CO), ↓ systemic vascular resistance (SVR)), cardiogenic (↓ CO, ↑ SVR), hypovolemic (↓ CO, ↑ SVR), obstructive (↓ CO), and mixed. Types of Shock and death.
• The most common reason for a rupture of the spleen Spleen The spleen is the largest lymphoid organ in the body, located in the LUQ of the abdomen, superior to the left kidney and posterior to the stomach at the level of the 9th-11th ribs just below the diaphragm. The spleen is highly vascular and acts as an important blood filter, cleansing the blood of pathogens and damaged erythrocytes. Spleen: Anatomy is blunt abdominal trauma, specifically motor vehicle accidents Motor Vehicle Accidents Spinal Cord Injuries, but can be caused by even minimal trauma in the case of patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship with splenomegaly Splenomegaly Splenomegaly is pathologic enlargement of the spleen that is attributable to numerous causes, including infections, hemoglobinopathies, infiltrative processes, and outflow obstruction of the portal vein. Splenomegaly.
• US:
  • Hypo-/ hyperechoic Hyperechoic A structure that produces a high-amplitude echo (lighter grays and white) Ultrasound (Sonography) fissures
  • Free perisplenic fluid
  • Hemorrhage and pseudoaneurysms: Doppler Doppler Ultrasonography applying the doppler effect, with frequency-shifted ultrasound reflections produced by moving targets (usually red blood cells) in the bloodstream along the ultrasound axis in direct proportion to the velocity of movement of the targets, to determine both direction and velocity of blood flow. Ultrasound (Sonography) will be required for the evaluation of pseudoaneurysms. 
• CT: best evaluated with multiphase CT Multiphase CT Computed Tomography (CT) (portal venous and delayed, usually)
  • Active hemorrhage
    • Hyperdense material (contrast) extravasation, which will expand on delayed imaging
    • Intraparenchymal vs. peritoneal free fluid

Splenic cyst

• A cyst is a saclike pocket of membranous tissue that contains fluid, air, or other substances.
• Patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship with a splenic cyst can present with LUQ pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways, left shoulder pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways, abdominal enlargement, splenomegaly Splenomegaly Splenomegaly is pathologic enlargement of the spleen that is attributable to numerous causes, including infections, hemoglobinopathies, infiltrative processes, and outflow obstruction of the portal vein. Splenomegaly, or no symptoms at all.
• US:
  • Lesion with a round shape
  • Homogeneous, with or without internal echoes caused by debris due to hemorrhage
  • Anechoic Anechoic A structure that produces no echo at all (looks completely black) Ultrasound (Sonography) 
  • Posterior acoustic enhancement with or without increased echogenicity of the posterior wall
  • Thin/imperceptible wall
• CT: 
  • Smooth margins
  • Hypodense, homogeneous lesions within the spleen Spleen The spleen is the largest lymphoid organ in the body, located in the LUQ of the abdomen, superior to the left kidney and posterior to the stomach at the level of the 9th-11th ribs just below the diaphragm. The spleen is highly vascular and acts as an important blood filter, cleansing the blood of pathogens and damaged erythrocytes. Spleen: Anatomy
  • No enhancement
  • With or without calcification 
• MRI:
  • Smooth margins
  • Homogeneous 
    • Hypointense Hypointense Magnetic Resonance Imaging (MRI) on T1 lesion
    • Hyperintense Hyperintense Magnetic Resonance Imaging (MRI) on T2 lesion 
  • Usually with no enhancement

Splenules or accessory spleens

• Also known as supernumerary spleens, splenules are small nodules of spleen Spleen The spleen is the largest lymphoid organ in the body, located in the LUQ of the abdomen, superior to the left kidney and posterior to the stomach at the level of the 9th-11th ribs just below the diaphragm. The spleen is highly vascular and acts as an important blood filter, cleansing the blood of pathogens and damaged erythrocytes. Spleen: Anatomy that are separate from the rest of the organ. They are typically rounded but can also be oval or triangular, have well-defined margins, and measure less than 2 cm. 
• In all imaging modalities, they show the following features:
  • Well-circumscribed mass Mass Three-dimensional lesion that occupies a space within the breast Imaging of the Breast with defined margins
  • Close to the spleen Spleen The spleen is the largest lymphoid organ in the body, located in the LUQ of the abdomen, superior to the left kidney and posterior to the stomach at the level of the 9th-11th ribs just below the diaphragm. The spleen is highly vascular and acts as an important blood filter, cleansing the blood of pathogens and damaged erythrocytes. Spleen: Anatomy (although they can be located anywhere in the abdomen)
• US:
  • Same splenic echogenicity
  • Blood vessels to the accessory spleen Spleen The spleen is the largest lymphoid organ in the body, located in the LUQ of the abdomen, superior to the left kidney and posterior to the stomach at the level of the 9th-11th ribs just below the diaphragm. The spleen is highly vascular and acts as an important blood filter, cleansing the blood of pathogens and damaged erythrocytes. Spleen: Anatomy
    • Color Doppler mode Doppler Mode Scrotal Imaging
    • Splenule vs. enlarged lymph Lymph The interstitial fluid that is in the lymphatic system. Secondary Lymphatic Organs node
• CT: 
  • Same spleen Spleen The spleen is the largest lymphoid organ in the body, located in the LUQ of the abdomen, superior to the left kidney and posterior to the stomach at the level of the 9th-11th ribs just below the diaphragm. The spleen is highly vascular and acts as an important blood filter, cleansing the blood of pathogens and damaged erythrocytes. Spleen: Anatomy density and attenuation/enhancement characteristics
• MRI:
  • Synchronized enhancement patterns with the main spleen Spleen The spleen is the largest lymphoid organ in the body, located in the LUQ of the abdomen, superior to the left kidney and posterior to the stomach at the level of the 9th-11th ribs just below the diaphragm. The spleen is highly vascular and acts as an important blood filter, cleansing the blood of pathogens and damaged erythrocytes. Spleen: Anatomy
  • Equal intensity to the spleen Spleen The spleen is the largest lymphoid organ in the body, located in the LUQ of the abdomen, superior to the left kidney and posterior to the stomach at the level of the 9th-11th ribs just below the diaphragm. The spleen is highly vascular and acts as an important blood filter, cleansing the blood of pathogens and damaged erythrocytes. Spleen: Anatomy on T1- and T2-weighted images T2-Weighted Images Imaging of the Head and Brain, including DWI DWI Imaging of the Head and Brain

Splenic infarction

• Occurs when the blood supply to a segment or the whole spleen Spleen The spleen is the largest lymphoid organ in the body, located in the LUQ of the abdomen, superior to the left kidney and posterior to the stomach at the level of the 9th-11th ribs just below the diaphragm. The spleen is highly vascular and acts as an important blood filter, cleansing the blood of pathogens and damaged erythrocytes. Spleen: Anatomy is occluded, resulting in ischemia Ischemia A hypoperfusion of the blood through an organ or tissue caused by a pathologic constriction or obstruction of its blood vessels, or an absence of blood circulation. Ischemic Cell Damage and necrosis Necrosis The death of cells in an organ or tissue due to disease, injury or failure of the blood supply. Ischemic Cell Damage to that area
• The most common cause is an underlying disease (e.g., cardiogenic embolism). 
• Patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship present with sudden abdominal pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways localized in the LUQ. 
• In all imaging modalities, they show the following features:
  • Wedge-shaped lesion
  • Peripherally located
• US:
  • Hypoechoic Hypoechoic A structure that produces a low-amplitude echo (darker grays) Ultrasound (Sonography) 
  • Absent blood flow Blood flow Blood flow refers to the movement of a certain volume of blood through the vasculature over a given unit of time (e.g., mL per minute). Vascular Resistance, Flow, and Mean Arterial Pressure: color Doppler Doppler Ultrasonography applying the doppler effect, with frequency-shifted ultrasound reflections produced by moving targets (usually red blood cells) in the bloodstream along the ultrasound axis in direct proportion to the velocity of movement of the targets, to determine both direction and velocity of blood flow. Ultrasound (Sonography)
• CT:
  • Hypodense 
  • No enhancement
• MRI:
  • Hypointense Hypointense Magnetic Resonance Imaging (MRI) on T1- and T2-weighted images T2-Weighted Images Imaging of the Head and Brain 
  • No enhancement

Splenic abscess Abscess Accumulation of purulent material in tissues, organs, or circumscribed spaces, usually associated with signs of infection. Chronic Granulomatous Disease

• An abscess Abscess Accumulation of purulent material in tissues, organs, or circumscribed spaces, usually associated with signs of infection. Chronic Granulomatous Disease is a collection of pus, usually caused by a bacterial infection, which can develop anywhere in the body.
• In all imaging modalities, abscesses present with the following features:
  • Irregular margins
  • With or without splenomegaly Splenomegaly Splenomegaly is pathologic enlargement of the spleen that is attributable to numerous causes, including infections, hemoglobinopathies, infiltrative processes, and outflow obstruction of the portal vein. Splenomegaly 
  • With or without pleural effusion Pleural Effusion Pleural effusion refers to the accumulation of fluid between the layers of the parietal and visceral pleura. Common causes of this condition include infection, malignancy, autoimmune disorders, or volume overload. Clinical manifestations include chest pain, cough, and dyspnea. Pleural Effusion (PE)
• US:
  • Hypo-/ hyperechoic Hyperechoic A structure that produces a high-amplitude echo (lighter grays and white) Ultrasound (Sonography)
  • With or without internal echoes
• CT:
  • Hypodense
  • With or without peripheral enhancement
• MRI:
  • Intensity
    • T1: hypointense Hypointense Magnetic Resonance Imaging (MRI)
    • T2: hyperintense Hyperintense Magnetic Resonance Imaging (MRI)
    • DWI DWI Imaging of the Head and Brain: hyperintense Hyperintense Magnetic Resonance Imaging (MRI)
  • With or without peripheral enhancement