Infection and the spleen: association between hyposplenism, pneumococcal sepsis and disseminated intravascular coagulation

Caudal DMN neurons innervate the spleen and release CART peptide to regulate neuroimmune function

BACKGROUND

Inflammation is a fundamental biological response to injury and infection, which if unregulated can contribute to the pathophysiology of many diseases. The vagus nerve, which primarily originates from the dorsal motor nucleus (DMN), plays an important role in rapidly dampening inflammation by regulating splenic function. However, direct vagal innervation of the spleen, which houses the majority of immune and inflammatory cells, has not been established. As an alternative to direct innervation, an anti-inflammatory reflex pathway has been proposed which involves the vagus nerve, the sympathetic celiac ganglion, and the neurotransmitter norepinephrine. Although sympathetic regulation of inflammation has been shown, the interaction of the vagus nerve and the celiac ganglia requires a unique interaction of parasympathetic and sympathetic inputs, making this putative mechanism of brain-spleen interaction controversial. BODY: As neuropeptides can be expressed at relatively high levels in neurons, we reasoned that DMN neuropeptide immunoreactivity could be used to determine their target innervation. Employing immunohistochemistry, subdiaphragmatic vagotomy, viral tract tracing, CRISPR-mediated knock-down, and functional assays, we show that cocaine and amphetamine-regulated transcript (CART) peptide-expressing projection neurons in the caudal DMN directly innervate the spleen. In response to lipopolysaccharide (LPS) stimulation, CART acts to reduce inflammation, an effect that can be augmented by intrasplenic administration of a synthetic CART peptide. These in vivo effects could be recapitulated in cultured splenocytes, suggesting that these cells express the as yet unidentified CART receptor(s).

CONCLUSION

Our results provide evidence for direct connections between the caudal DMN and spleen. In addition to acetylcholine, these neurons express the neuropeptide CART that, once released, acts to suppress inflammation by acting directly upon splenocytes.

Blunt splenic injuries: have we watched long enough?

BACKGROUND

Nonoperative management (NOM) of blunt splenic injuries (BSIs) has been used with increasing frequency in adult patients. There are currently no definitive guidelines established for how long BSI patients should be monitored for failure of NOM after injury.

METHODS

This study was performed to ascertain the length of inpatient observation needed to capture most failures, and to identify factors associated with failure of NOM. We utilized the National Trauma Data Bank to determine time to failure after BSI.

RESULTS

During the 5-year study period, 23,532 patients were identified with BSI, of which 2,366 (10% overall) were taken directly to surgery (within 2 hours of arrival). Of 21,166 patients initially managed nonoperatively, 18,506 were successful (79% of all-comers). Patients with isolated BSI are currently monitored approximately 5 days as inpatients. Of patients failing NOM, 95% failed during the first 72 hours, and monitoring 2 additional days saw only 1.5% more failures. Factors influencing success of NOM included computed tomographic injury grade, severity of patient injury, and American College of Surgeons designation of trauma center. Importantly, patients who failed NOM did not seem to have detrimental outcomes when compared with patients with successful NOM. No statistically significant predictive variables could be identified that would help predict patients who would go on to fail NOM.

CONCLUSIONS

We conclude that at least 80% of BSI can be managed successfully with NOM, and that patients should be monitored as inpatients for failure after BSI for 3 to 5 days.

Splenic arterial interventions: anatomy, indications, technical considerations, and potential complications

Splenic arterial interventions are increasingly performed to treat various clinical conditions, including abdominal trauma, hypersplenism, splenic arterial aneurysm, portal hypertension, and splenic neoplasm. When clinically appropriate, these procedures may provide an alternative to open surgery. They may help to salvage splenic function in patients with posttraumatic injuries or hypersplenism and to improve hematologic parameters in those who otherwise would be unable to undergo high-dose chemotherapy or immunosuppressive therapy. Splenic arterial interventions also may be performed to exclude splenic artery aneurysms from the parent vessel lumen and prevent aneurysm rupture; to reduce portal pressure and prevent sequelae in patients with portal hypertension; to treat splenic artery steal syndrome and improve liver perfusion in liver transplant recipients; and to administer targeted treatment to areas of neoplastic disease in the splenic parenchyma. As the use of splenic arterial interventions increases in interventional radiology practice, clinicians must be familiar with the splenic vascular anatomy, the indications and contraindications for performing interventional procedures, the technical considerations involved, and the potential use of other interventional procedures, such as radiofrequency ablation, in combination with splenic arterial interventions. Familiarity with the complications that can result from these interventional procedures, including abscess formation and pancreatitis, also is important.

Unusual manifestations of invasive pneumococcal infection

Unusual pneumococcal infections occurred frequently in the preantibiotic age but rapidly declined with the advent of the antibiotic era. Unfortunately, the morbidity and mortality associated with invasive pneumococcal disease remain high despite antibiotic therapy and monumental advances in medical technology. The incidence of invasive pneumococcal disease has increased recently because of the onset of the human immunodeficiency virus (HIV) epidemic and the emergence of antibiotic-resistant pneumococcus. Robert Austrian described the clinical triad of pneumococcal pneumonia, meningitis, and endocarditis, a syndrome that now bears his name. Although seen infrequently today, unusual manifestations of pneumococcal infection such as those Austrian reported still occur. A review of these cases is warranted because, as drug-resistant organisms continue to emerge worldwide, more unusual pneumococcal infections will be seen. Streptococcus pneumoniae is responsible for a remarkable array of disease processes; our literature review uncovered 95 different types of unusual pneumococcal infections representing 2,064 cases. Examples of these infections included pancreatic and liver abscesses, aortitis, gingival lesions, phlegmonous gastritis, inguinal adenitis, testicular and tubo-ovarian abscesses, and necrotizing fasciitis. We also reviewed predisposing underlying illnesses and conditions. Alcoholism, HIV infection, splenectomy, connective tissue disease, steroid use, diabetes mellitus, and intravenous drug use remain common risk factors for invasive pneumococcal infections. Currently, multidrug-resistant S. pneumoniae remains susceptible to vancomycin and several new third-generation fluoroquinolones. As what some fear will be a possible postantibiotic era approaches, clinicians must be able to recognize and manage unusual pneumococcal infections.

Purpura fulminans in pneumococcal sepsis: case report and review

Purpura fulminans is classically defined by ecchymotic skin lesions, fever, and hypotension. The majority of cases occur in association with bacterial sepsis, and disseminated intravascular coagulation (DIC) is usually present. Prompted by our experience with a patient with pneumococcal sepsis and purpura fulminans in whom hypotension was never observed, we evaluated the important parameters of sepsis in reports of this syndrome. 42 additional cases of pneumococcal bacteremia and purpura fulminans were identified. Hypotension was present in only 51%. Although DIC was present in 85% of patients, hypofibrinogenemia was documented in only 26%. By contrast, both hypotension and hypofibrinogenemia are present in the vast majority of patients described with purpura fulminans in association with meningococcal sepsis. These data confirm that hypotension is not a necessary feature of the syndrome of purpura fulminans associated with pneumococcal sepsis and suggest further that qualitative or quantitative differences exist in the DIC cascade of pneumococcal vs meningococcal sepsis.

Fatal pneumococcal septicemia in a patient with a connective tissue disease

Fulminant pneumococcal sepsis is a rare but life-threatening illness usually occurring in patients with known splenic absence (postsplenectomy) or dysfunction (sickle cell anemia). Several medical illnesses, not typically recognized as being associated with abnormal spleen function, may be complicated by fulminant pneumococcal sepsis. We report a case of fatal pneumococcal sepsis in a patient diagnosed with mixed connective tissue disease who likely had systemic lupus erythematosus and unsuspected splenic fibrosis. Medical illnesses associated with functional asplenia, hematological findings suggesting splenic dysfunction, and confirmatory tests of hyposplenism are discussed.

Rapid and definitive diagnosis of infectious diseases using peripheral blood smears

A timely diagnosis is essential in the management of septicemia and septic shock. Three patients are described, all of whom presented with fever and one of whom was hypotensive at the time of admission. In each patient, rapid diagnosis of the cause of fever was possible because microorganisms were identified on a peripheral blood smear obtained at the time of admission. This identification permitted prompt initiation of appropriate antimicrobial therapy. In addition, a literature review of use of peripheral blood smears in the diagnosis of bacterial, fungal, and parasitic infections is provided.

Postsplenectomy sepsis and its mortality rate: actual versus perceived risks

A collective critical review of the literature on postsplenectomy sepsis from 1952 to 1987 has been undertaken. The reports cover a cohort of 12,514 patients undergoing splenectomy but of these only 5902 reports were sufficiently detailed to allow a useful analysis. The incidence of infection after splenectomy in children under 16 years old was 4.4 per cent with a mortality rate of 2.2 per cent. The corresponding figures for adults were 0.9 per cent and 0.8 per cent respectively. The present analysis of well documented patients has shown that severe infection after splenectomy for benign disease is very uncommon except in infants (infection rate 15.7 per cent) and children below the age of 5 years (infection rate 10.4 per cent). Many of these reported postsplenectomy infections may have been coincidental. It is also apparent that children contract a different type of infection after splenectomy than adults, predominantly a meningitis which is less frequently fatal. Adults, in contrast, appear to develop a septicaemic type of illness associated with a higher mortality rate. This survey has also shown that children are reported to be more susceptible to pneumococcal sepsis than to infection caused by any other organism. Although the removal of the spleen in otherwise normal people does not appear to be associated with an increased frequency of infection, the presence of a coexistent disorder, notably hepatic disease, can increase the risk substantially.

Severe late postsplenectomy infection

In all, 1490 patients underwent splenectomy in Western Australia between 1971 and 1983, giving 7825 person years exposure. Thirty-three patients developed severe late postsplenectomy infection (septicaemia, meningitis or pneumococcal pneumonia requiring hospitalization) and three developed overwhelming postsplenectomy infection. The incidence and mortality rates of severe late postsplenectomy infection were 0.42 and 0.08 per 100 person years exposure respectively and for overwhelming postsplenectomy infection the incidence and mortality rates were 0.04 per 100 person years exposure. There were 628 splenectomies after trauma, giving 3922 person years exposure. Eight patients developed severe late postsplenectomy infection of whom one had overwhelming postsplenectomy infection. Following trauma, the incidence of severe late postsplenectomy infection was 0.21 per 100 person years exposure, with the incidence and mortality rates of overwhelming postsplenectomy infection being 0.03 per 100 person years exposure. Patients undergoing splenectomy have a 12.6-fold increased risk of developing late septicaemia compared with the general population. Splenectomy following trauma gives an 8.6-fold increased risk of late septicaemia. The majority of severe late postsplenectomy infections did not occur within the first 2 years and 42 per cent of severe late postsplenectomy infections occurred greater than 5 years after splenectomy. The low incidence of severe late postsplenectomy infection and overwhelming postsplenectomy infection makes statistical evaluation of the effectiveness of prophylactic antibiotics, vaccination and splenic repair most difficult.

Does splenectomy predispose to meningococcal sepsis? An experimental study and clinical review

Splenectomy is a recognized factor predisposing to the late complication of serious sepsis. The meningococcus has been listed as an important organism in postsplenectomy infection. A survey of the literature, however, revealed a total of only 13 documented case reports over a 31-year period, including ten pediatric cases. No documented cases of meningococcal sepsis in children following splenectomy for trauma were found. In an experimental mouse meningococcal infection model, the intraperitoneal LD50 was similar between normal and splenectomized mice (4 X 10(8) v 4 X 10(7) cfu, respectively; P = not significant). Bacteremic patterns were similar in both groups. Uniform survival was seen in normal and splenectomized mice after various intravenous challenge doses of meningococci up to 10(6) cfu. This was associated with efficient bacterial clearance in both groups. It appears unlikely that the defect resulting from splenectomy alone is an important predisposing factor in meningococcal sepsis.

Comparison and definition of spleen and lymph node: a phylogenetic analysis

The hitherto largely unsolved problem with a biological definition of spleen versus lymph node seems possible to solve from a phylogenetic point of view. Thus, it is suggested that the spleen be defined as a hemopoietic organ which is able to filter blood with sinusoids. In contradistinction, a lymph node is defined as a hemopoietic organ which is able to filter lymph with sinusoids. Comparative anatomical studies show that the spleen appears as a condensation of the lymphomyeloid complex in the spiral fold of the gut in cyclostomes. The spiral fold spleen vanishes with the bony fishes, while in cartilaginous fishes a similar spleen appears in the dorsal mesentery. The dorsal spleen remains in a retroperitoneal position in higher vertebrates and is regarded as a specialized blood vessel compartment closely connected with the blood stream. In "higher" vertebrates the spleen is a stagnated organ because splenic functions are gradually transferred to other sites. The bone marrow takes over the erythro-, thrombo- and granulocytopoiesis while the lymph nodes take over the lymphocytopoiesis. This transfer of the splenic functions is first seen in anurans and seems to be a marvelous adaptation to life on land where the need for local defence against a large number of antigens is necessary before spread of the antigens to central parts of the body. In higher vertebrates, the great number of lymph nodes at peripheral positions, derived from the lymphatic vessels, are able to do so. It is demonstrated that the definitions of spleen and lymph nodes as hemopoietic organs which by their sinusoids are able to filter blood and lymph, respectively, are not only of semantic interest but also useful in regard the immunohematological system as an entity.

Postsplenectomy sepsis 10 years or more after operation

Three new cases (two fatal) of postsplenectomy sepsis occurring 14, 25, and 26 years after operation for hereditary spherocytosis are described. There are now 25 cases in the published work in which this complication occurred 10 or more years after operation, 14 of which were fatal. The mean age of onset is 37 years. The features of the disease are similar to those seen in other postsplenectomy infections, and pneumococcal infection was responsible in 19 cases (76%). The major predisposing illnesses were trauma, hereditary spherocytosis, and idiopathic thrombocytopenia.

Immune dysfunction in the presence of residual splenic tissue

Immunological function was examined in children who had undergone splenectomy, in 8 for trauma, and in 11 for haematologic/oncologic reasons. Particular emphasis was placed on the effects of residual splenic tissue on immune function. Children in the elective group had no evidence of splenosis but 6 of the 8 trauma patients showed residual splenic activity. A general trend indicated that immunological dysfunction was associated with the presence of residual splenic tissue. Three patients with significant post-traumatic splenosis showed low IgM levels, one also had a low IgG level and another a low IgA and impaired lymphocyte response to mitogens. The trauma patients with little or no splenic tissue had normal immune functions. Immunological abnormalities were found in 8 of the 11 haematologic/oncologic patients with no splenosis suggesting the abnormalities were possibly due to the primary disease. In contrast to the popular belief that splenosis confers protection against overwhelming sepsis, the present findings suggest that patients with residual splenic tissue are at a greater risk of infection because of a lower level of immune response.

Hemisplenectomy using a hand-held CO2 laser. An experimental study

Hemisplenectomy was performed in mongrel dogs using a hand held CO2 laser. Cutting and hemostasis were performed by a laser beam with a high concentration power--about 6kW/mm2--at the focal spot, and residual bleeding was controlled by using a defocused beam. The cutting action was improved by temporary closing of the arterial vessels and by injecting adrenaline into the splenic artery to produce a relatively dry surface. The surgical procedure was free of mortality or morbidity. Histological studies revealed a brand of fibrous tissue at the cut surface, without apparent abnormalities in the splenic parenchyma beneath the section. Activity of the residual half spleen was shown by postoperative technetium scan and by the fact that Howell-Jolly bodies appeared in peripheral blood only after resection of the remaining half spleen.

Complement in pneumococcal infections with varying degrees of severity

Complement component levels (Clq, Cls, C4, C3, factor B and properdin) and C1 subcomponent complexes (C1r-C1s, C1-r-C1-, C1-r-C1-s-C1 inactivator, 1A) were studied in 16 adults with pneumococcal infections varying severity. Patients with fulminant disease and signs of septic shock showed pronounced hypocomplementemia. In patients with pneumococcal pneumonia or meningitis elevated levels of C1-r-C1-s-C1- IA complexes indicated activation of C1, despite normal levels of C1q, C1s, C4 and C3. Moderately decreased properdin values suggested involvement of the alternative pathway. In adults with pneumococcal otitis no changes in the complement profile was found. In contrast, pronounced aberrations of the C1 subcomponents were earlier demonstrated in children with otitis.

Splenic size and function in adult coeliac disease

Splenic scintigraphy was performed after measurement of 99Tcm-labelled heat-damaged red cell clearance in 29 patients with treated coeliac disease. Good correlation was found between splenic size and function using these techniques. 99Tcm-labelled sulphur colloid scintiscans were also performed in 24 coeliacs. Splenic volumes computed from colloid scans correlated well with those computed from red cell scans. Almost 50% of adult patients with treated coeliac disease have impaired splenic function, the incidence rising with increasing age of starting treatment. Sulphur colloid scintigraphgy provides a simple quantitative method of assessing splenic function in treated coeliac disease which can be used in exploring the possibilities of avoidance of the adverse effects of hyposplenism.

Serum immunoglobulin changes after accidental splenectomy in adults

Serum immunoglobulin levels were examined in a group of twelve healthy adults who underwent accidental splenectomy. Depressed mean IgM levels and elevated mean IgA levels were found in these patients as compared with the control group consisting of forty-five healthy, untraumatized volunteers. Immunoglobulin changes may have some relevance for the increased tendency to severe infections which has been noted after splenectomy.

Hyposplenism in inflammatory bowel disease

Splenic function was assessed in 35 patients with ulcerative colitis and 20 patients with Crohn's disease. Hyposplenism was diagnosed if there were Howell-Jolly bodies in the peripheral blood film or if there was prolongation of clearance from the peripheral blood of injected 51-Cr-labelled heat-damaged red blood cells. Thirteen of the patients with ulcerative colitis had hyposplenism as compared with only one patient with Crohn's disease. Conversely, heat-damaged red cell clearance values faster than the normal range were found in six out of the 20 patients with Crohn's disease. Four patients with hyposplenism and ulcerative colitis developed life-threatening septicaemia in the early postcolectomy period, two of these being further complicated by disseminated intravascular coagulation.

The non-operative management of splenic trauma

Non-operative management of splenic trauma is not a widely accepted method of treatment. During the period 1964 to 1976, 39 children were treated in the Adelaide Children's Hospital for splenic trauma. Twenty-four were managed without operation, while 15 were treated by splenectomy. Recently, splenic scan has helped in the diagnosis and management of splenic injuries. From our observations, it appears that non-operative treatment of a proven splenic injury is safe and the ideal initial treatment in the paediatric age group, when the spleen is the only intraabdominal organ injured, and the vital signs are stable with the application of adequate resuscitative measures.

Overwhelming postsplenectomy infection

One of the more intriguing aspects of the spleen is the protection against certain bacterial infections afforded by its unique vascular and immune function. There have been extensive clinical surveys which indicate an incidence of overwhelming postsplenectomy infection (OPSI) above that of the disease for which the splenectomy was done. In the absence of the spleen, either congenital or subsequent to surgical removal, this overwhelming sepsis has a 50% case fatality rate. The most common infective organism has been Diplococcus (tstreptococcus) pneumoniae (D. pneumoniae). Intensive investigations indicated loss of phagocytic function of the spleen, depression of serum IgM levels, a possible suppression of the lymphocyte responsiveness, and changes in opsonin-alternative complement system as potential causes of OPSI. Preventive measures against OPSI include trials of prophylactic Phenoxymethyl Penicillin (penicillin) and pneumococcal vaccine.

The use of technetium-99m labelled heat-damaged red cells for the quantitative measurement of splenic function

A comparison of the rates of clearance of 51Cr labelled and 99mTc labelled heat-damaged red cells in 25 patients and 4 control subjects is reported. Very little correlation was found between the clearance half-times of the two types of labelled cells when the cells were labelled with 99mTc prior to heat damaging. The correlation was improved when the labelling step occurred after the cells had been damaged. Urinary excretion measurements revealed that the rate of excretion of 99mTc could be as much as nine times that of the 51Cr label. 99mTc labelled heat-damaged red cells were found not to be sufficiently stable a preparation for use in quantitative clearance studies.

Splenectomy in childhood: a review in England and Wales, 1960-4

An investigation was carried out of 821 children under the age of 16 years who were subjected to splenectomy in England and Wales during the 5 years 1960-4. A postal follow-up study provided satisfactory information concerning 96 per cent of these. Excluding early postoperative deaths, practically all the cases were followed up for 2 years or more and 70 per cent for more than 5 years. Forty-nine children had died since operation, 32 from underlying disease and 17 from infection. Fifty children (6 per cent of the survivors) had major infections considered to be due to the primary condition aggravated by splenectomy. Seven died, all from the primary disease. Sixteen children (2 per cent) developed septicaemic illnesses and 10 died. In these the effect of splenectomy was considered to be the primary factor. Fourteen of the 16 had been operated on in the first 4 years of life. Practically all the serious infections occurred within 3 years of operation and pneumococcus was the organism most frequently implicated. Ninety per cent of the splenectomies in childhood were performed for accidental injury, congenital haemolytic anaemia or idiopathic thrombocytopenic purpura. Accidental injury to the spleen rarely occurs in very young children, and in the other two conditions splenectomy can usually be safely delayed untile over the age of 3 years. If this is achieved it is estimated that the unavoidable risk of dangerous infection is less than 1 per cent. One in 10 splenectomies will be carried out for severe and potentially fatal illnesses and in this situation the risk from operation is of secondary importance. Many such conditions carry increased susceptibility to infection per se or because corticosteroids or other immune suppressants are used in their management. It is recommended that splenectomy be avoided if at all possible during the early years of life. It is further recommended that prophylactic penicillin be administered for 3 years following operation whatever its indication and whatever the age of the patient. If the underlying condition itself carries risk of infection more active and more prolonged prophylaxis may be indicated.

Infections in 92 splenectomized patients with Hodgkin's disease. A clinical review

Infections that occurrred in 92 previously untreated patients with Hodgkin's disease were reviewed from the time of laprotomy and splenectomy. Pneumonias occurred in nine patients with urinary tract infections in twelve during the immediate postoperative period. Severe bacterial infections did not occur in any patients during initial radiation therapy, adjuvant chemotherapy (stages I through IIIA), initial intensive chemotherapy (stages IIIB and IV) or during remission. Severe infections occurred in eight profoundly granulocytopenic patients with recurrent Hodgkin's disease. Streptococcus (Diplococcus) pneumoniae and Hemophilus spp infections were distinctly uncommon during the remission period. Herpes zoster, however, was very common developing in 22 of 92 (24 per cent) patients. Predisposing factors to herpes zoster included sex (female more than male), therapy (radiation plus chemotherapy more than chemotherapy alone), and age (less than 30 years of age more often than 30 to 50 years of age). Severe infection was uncommon in these patients except in ascociation with specific predisposing factors such as the immediate postoperative state of prolonged granulocytopenia associated with recurrent Hodgkin's disease or its therapy. Splenectomy per se did not affect either the incidence or the severity of infection during this period of 12+ months of observations per patient.

Patho-physiological changes following ischemia of the spleen

Images