The Spleen

Anatomy of Spleen

White Pulp

Spleen Structure

The white pulp is circular in

structure and is made up mainly

of lymphocytes. It functions in a

manner similar to the nodules of the

lymph node.

The red pulp surrounds the white

pulp and contains mainly red blood

cells and macrophages. The main

function of the red pulp is to

phagocytize old red blood cells.

Red Pulp

Function

The spleen is a sophisticated filter that monitors and manages blood cells and immune functions

During fetal development the spleen produces red and white blood cells

By the fifth month of gestation the spleen no longer has hematopoietic function but retains the capacity throughout life

Red cells that pass through the spleen undergo a “cleaning” or repair

Abnormal and old cells are destroyed

Function Reticulocytes loose their nuclear remnants and

excess membrane before entering the circulation RBC’s coated with IgG and IgM are removed

and destroyed The spleen is the site of destruction in autoimmune

disease states (ITTP and hemolytic anemia) Parasites such as malaria can be removed as well

The spleen is involved in specific and nonspecific immune responses (promotes phagocytosis and destruction of bacteria)

Sites of Haemopoiesis Yolk sac

Liver and spleen

Bone marrow Gradual replacement of

active (red) marrow by tissue inactive (fatty)

Expansion can occur during increased need for cell production

Splenic Trauma Diagnosis

Injury should be suspected in blunt upper abdominal injuries ( MVA and Bike)

Injuries are often associated with fractured ribs of the left chest

Splenic injuries can cause extensive and continued hemorrhage, others can cause subcapsular hematomas that are subject to rupture at any time

If splenic injury is suspected, admission to the hospital for monitoring is mandatory

The signs and symptoms of splenic trauma are those of hemoperitoneum (generalized LUQ pain)

Treatment of Ruptured SpleenSplenic preservation operationsPartial splenectomyCapsular repairNon operative treatment

Delayed Rupture of the Spleen Injury to the pulp sometimes cannot be

contained indefinitely by the splenic capsule The usual interval between injury and

hemorrhage is within two weeks (longer intervals have been reported)

The incidence is between 15-30% It is hoped that as imaging techniques

improve the incidence will decrease

Splenosis Is the auto transplantation of splenic tissue

after splenic trauma They vary from a few millimeters to several

centimeters in diameter May occur anywhere in the peritoneal cavity Seldom causes symptoms and is usually

discovered as an incidental finding at reoperation

Post splenectomy sepsis has renewed interest in splenosis

Causes of splenomegaly Infection

Bacterial: Typhoid fever, endocarditis, septicemia, abscess Viral:E-B virus, CMV, and others Protozoal: Malaria, toxoplasmosis

Hematologic processes Hemolytic anemia: Congenital, acquired Extramedullary hematopoiesis: thalassemia, osteopetrosis, myelofibrosis

Neoplasms Malignant: Leukemia, lymphoma, histiocytoses, metastatic tumors Benign: Hemagioma, hamartoma

Metabolic diseases Lipidosis: Niemann-Pick, Gaucher disease Mucopolysaccharidosis infiltration: Histiocytosis

Congestion Cirrhosis Cysts Miscellaneous

Hypersplenism Refers to a variety of ill effects resulting from

increased splenic function that may be improved by splenectomy

The criteria for diagnosis included: Anemia, leukopenia, thrombocytopenia or a

combination of the three Compensatory bone marrow hyperplasia Splenomegaly

Hypersplenism can be categorized as primary or secondary

Splenic Involvement in Hodgkin’s lymphoma The probability of splenic involvement

increases with increasing spleen size The absence of splenomegaly does not

exclude splenic involvement Upon gross examination of the spleen a

grayish white nodule ranging from several millimeters to several centimeters is apparent with Hodgkin’s disease

Liver involvement with Hodgkin’s disease rarely occurs in the absence of splenic disease

Felty’s Syndrome Is a syndrome consisting of severe

rheumatoid arthritis, granulocytopenia and splenomegaly

It usually occurs in patients with a long history of rheumatoid arthritis

Severe, persistent and recurrent infections are characteristic

Moderate splenomegaly is common Splenectomy is effective in most patients

Gaucher’s Disease Is a disorder of lipid metabolism that may result

in massive splenomegaly and hypersplenism Commonly found in the Jewish population Diagnosis is made by finding the typical

Gaucher’s cells in biopsy tissue Massive splenomegaly is usually the most

common form of presentation The adult form is the most common form Splenomegaly (subtotal) shows great benefits

Cysts and Tumors of the Spleen The differential diagnosis of splenomegaly should

include splenic masses and primary tumors (these conditions are rare however they must be considered) Cystic lesions comprise parasitic and nonparasitic cysts

Parasitic cysts are due almost exclusively to echinococcal disease (rare in the United States)

Nonparasitic cysts are classified as primary (true) which have an epithelial lining or pseudocysts (more common

Symptoms of splenic cysts are vague and are caused primarily by mass effect (compression of adjacent viscera)

Cysts and Tumors of the Spleen

Selected nonparasitic cyst may be managed by aspiration

Splenectomy should be performed for all large cyst and those with an uncertain diagnosis

Malignant and benign primary tumors of the spleen are rare

Most primary malignant tumors are angiosarcomas

Infectious Mononucleosis A disease characterized by fever, sore throat,

lymphadenopathy and atypical lymphocytes Most patients are young Clinical symptoms are similar to those of a

severe upper respiratory tract infection The spleen is enlarged and palpable in over

50% of patients Splenic rupture may occur

Incidental SplenectomyThe spleen is vulnerable to injury during

operative procedures in the upper abdomen When the splenic capsule is torn,

splenectomy is frequently performed Morbidity and mortality is higher with

iatrogenic injury requiring splenectomy

SplenectomyPrior to removing the spleen specific

preoperative preparation is necessary All patients should receive polyvalent

pneumococcal vaccine, polyvalent meningococcal vaccine and Haemophilus influenzae type b conjugant vaccine

Blood and blood products should be available well in advance of surgery

Blood Compositional Changes in the Asplenic or Hyposplenic Patient The absence of functional splenic tissue results

in characteristic changes in the circulating blood Some of these are predictable and desirable results These changes are considered a measure of its

success when splenectomy is performed for a hematologic disease

Howell-Jolly bodies (nuclear remnants) and thrombocytosis (desired result)

Other findings include: target cells, acanthocytes (spur cells), Heinz bodies (denatured hemoglobin) and stippled red cells

Postsplenectomy Sepsis Asplenic patients have an increased susceptibility

to the development of overwhelming infection The risk of sepsis is approximately 60 times

greater than normal after splenectomy The risk is greatest in children younger than four

years of age The risk of sepsis is higher among patients

requiring splenectomy for inherited diseases The risk of sepsis after splenectomy is lowest

after trauma

Postsplenectomy Sepsis Postsplenectomy sepsis syndrome typically

occurs in a previously healthy individual after a mild upper respiratory tract infection associated with fever

Within hours, nausea, vomiting, headache, confusion, shock and coma can occur; death follows within 24 hours

The nature of the syndrome makes it difficult to diagnose early enough for therapy to be effective

Postsplenectomy Sepsis The most common bacteria isolated our

streptococcus pneumoniae, Neisseria meningitidis, E. coli or Haemophilus influenzae

Because half of the patients develop sepsis from strep pneumoniae, penicillin can be administered immediately with onset of a febrile URI

Patients are instructed to obtain and wear a Medic alert tag

Hyposplenism Is a potentially lethal syndrome characterized by

diminished splenic function The patient peripheral blood smears appear as if they

are asplenic Hyposplenism can occur in the presence of abnormal

sized or enlarged spleen The danger of hyposplenism is the risk of developing

potentially lethal sepsis Sickle cell anemia is the most common disease

associated with hyposplenism The most common surgical disease associated with

hyposplenism is chronic UC

Hyposplenism

OverviewDefinition of HyposplenismMedical HistoryThe function of the spleenCongenital asplenia vs. splenectomy Immunological consequences of

HyposplenismDiagnosis and complications

What is Hyposplenism?Hyposplenism is the lack of a spleen or

its functionThe rare genetic disorder- Congenital

AspleniaThe surgical removal of the spleen-

splenectomyResults in severe immunological

consequences.

History Immunological importance of the spleen

Morris and Bullock-1919First post-splenectomy infection

O’Donnell-1929Effects of Hyposplenism

King and Shumacker-1952

The Spleen Largest lymphoid tissue of the body Serves two main functions

Filters blood to remove damaged/old RBC- red pulp Serves as secondary lymphoid tissue by removing infectious

agents and using them to activate lymphocytes- white pulp A significant reservoir for T lymphocytes Plays an active role in the production of IgM

antibodies and complement Has significant role in the functional maturation of

antibodies

Congenital AspleniaAutosomal recessive genetic disorderBelieved to be caused by absence of

the Hox 11 gene in the embryoCauses decreased adaptive immune

responseAssociated with structural abnormalities

in other organs of the body- cause death in infancy

SplenectomyRemoval of spleen tissue (partial or

complete)Usually needed because of traumaResidual splenic function in ¼ to ⅔ of

patients IgM levels decreases, IgG levels remain

constant or increase, IgA and IgE levels increase

Immunological Consequences Causes slower and incomplete adaptive immune

response against bacteria Low levels of tuftsin, which stimulates phagocytosis

by neutrophils, macrophages, and monocytes Decreased neutrophil and macrophage activity Increased NK cell activity Limited capacity of circulating B-cells to differentiate

into antibody-secreting cells Decreased level of T-cells

Diagnosis Determined by anatomic presence or

absence of the organ, its size, and any lesions.

Function can be assessed by Radiologic Techniques

X-ray, ultrasound, tomography, MRI, radionucleotide scanning

Morphologically Peripheral blood smear- presence of Howell-Jolly bodies

Howell Jolly bodies

Howell-Jolly

bodies are round,

purple staining nuclear

fragments of DNA in the red

blood cell

Complications Lifelong risk for Overwhelming Postsplenectomy

infection (OPSI) Caused by Streptococcus pneumoniae and gram negative

bacteria Initial Symptoms: fever, chills, muscle aches, headache,

vomiting, diarrhea, and abdominal pain Progressive symptoms: bacteremic septic shock, extremity

gangrene, convulsions, and coma Mortality rate of 50-80%

from onset of initial symptoms, 68% of those deaths occur within 24 hours and 80% occur within 48 hours

Prevention: routine vaccinations and prophylactic antibiotics

Summary Hyposplenism is the lack of a spleen or its

function Can be either genetic or surgically induced It has detrimental effects on the immune

system by decreasing the body’s ability to fight bacterial infections and reducing the adaptive immune response

Infections in Asplenic Patients

Causes of AspleniaCongenital

Often associated with serious organ malformations

Acquired Post surgical removal Functional hyposplenism

Function of the Spleen Immunological functions

Main site of opsonic antibody production Especially efficient in removal of encapsulated

bacteria Remaining RES may compensate but not in

case of encapsulated bacteria

Filtration Removal of abnormal erythrocytes and

intraerythrocytic inclusions eg nuclear inclusions and parasitised RBC

Overwhelming Infection Overall incidence of sepsis is low

3,2% in adults 3,3% in children Risk stratified according to cause, being highest in

patients with thalassaemia major and sickle-cell anaemia (J Infect 2001 Oct;43: 182-6)

Lifetime risk for OPSI of 5% Mortality

Death rates 600 times greater than general population Higher in children (1,7% vs 1,3%), but other reports say

higher in > 16 years Mandel say doesn’t correspond to indication but Bisharat

et al suggest higher in haematological disorders

Duration of riskMost occur within 2 years post

splenectomyRisk is lifelong as cases have been

reported up to 20 years post surgeryEarly complications may be

underreported as surgical complication

MicrobiologyS. pneumonia

50 – 90% of cases Common in all age groups Distribution of serotypes seems to be same as

other forms of pneumococcal infection 75% belonged to serotypes covered in 23

valent vaccine (ibid)

Micro cont…H. influenza

Regarded as 2nd most common cause Incidence reduced with vaccination Non-typable strains do not seem to

predominate in PSS

N. meningitidis Reported by some studies as associated but

others as well as animal experiments seem to support a lack of association

Other Micro-organisms Listeria monocytogenes E. coli Klebsiella sp Salmonella typhimurium S. aureus Cytocapnophagia canimorsus Plesiomonas shigelloides Recently occupational exposures have been

highlighted

Management Immunisations

Pneumococcal – 2 weeks prior to elective surgery otherwise when patient is recovered prior to discharge. Boosters every 5-10 years

H. influenza – recommended but evidence for immunogenicity and boosters lacking

Meningococcal – not routinely recommended Influenza – may be of value especially in

reducing risk of secondary bacterial infection

Mx continued…Antibiotic prophylaxis

Controversial Penicillin In all cases, esp in first 2 years post surgery All up to 16 and if underlying immune

dysfunction May not prevent sepsis Local resistence patterns need to accounted for Home antibiotic supply

Cont………Travellers

MALARIA PROPHYLAXIS Meningococcal vaccine Antibiotic prophylaxis

EducationMedic alert bracelet etc.