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Article 1
Overwhelming Postsplenectomy Infection: A Prospective Multicenter Cohort Study. Theilacker C, Ludewig K, Serr A, Schimpf J, Held J, Bögelein M, Bahr V, Rusch S, Pohl A, Kogelmann K, Frieseke S, Bogdanski R, Brunkhorst FM, Kern WV. Clin Infect Dis. 2016 Apr 1;62(7):871-878.
Although splenectomy is much less common after traumatic injury than in the past the consequences of splenectomy remain incompletely studied. Approximately 25,000 splenectomies are performed in the United States. Although overwhelming post-splenectomy infection (OPSI) remains the most common problem the incidence of this complication and the preventability through vaccination remain relatively unknown. It is also unclear how prior splenectomy impacts the outcome of severe sepsis once infection and sepsis has occurred. Most epidemiological studies of OPSI have used hospital administrative data that lacks information on disease severity as well as vaccination status.
Theilacker and colleagues performed a prospective observational case-control study involving all patients admitted to one of 173 German ICUs with community acquired severe sepsis or septic shock. Splenectomized patients were matched to controls based on age decade, gender, and ICU type. The indication for splenectomy was malignancy in 21% and trauma in 17% with the remainder of the patients for other benign conditions. In splenectomized patients 42% of infections were caused by streptococcus pneumoniae and none by H. Influenzae or Neisseria meningitidis. Only 12% of patients without asplenia had a pneumococcal source. Pneumococcal vaccination was present in less than half of asplenic patients. OPSI occurred more than 2 years after splenectomy in more than 70% of asplenic patients. Outcomes between the groups were similar with respect to mortality and other outcomes.
This study highlights the fact pneumococcal infection remains the most significant risk in asplenic patients. The other interesting finding was the delayed presentation of asplenic patients indicating a potential for a benefit for booster vaccinations.
Article 2
Splenectomy and the risk of sepsis: a population-based cohort study. Edgren G, Almqvist R, Hartman M, Utter GH. Ann Surg. 2014 Dec;260(6):1081-7.
Edgren and colleagues performed a large population based study in Sweden where national patient identifiers can be used to follow patients over long periods of time. The authors analyzed all patients who underwent splenectomy during the years 1970 through 2009. Standardized incidence ratios (SIR) and standardized mortality ratios (SMR) were calculated to compare the rates of sepsis in asplenic patients compared to the general population. Patients were separated based on the indication for splenectomy and age. The patients were also categorized based on time period based on probability of having received a pneumococcal vaccine. The three time periods were prior to use of vaccination after splenectomy, a period of introduction and a period when vaccination was highly probable.
There were 20, 132 splenectomized patients analyzed. The SIR for sepsis after trauma splenectomy was 3.4 which was the lowest of all splenectomized groups. The SIR for patients less than 12 years of age was somewhat higher at 6.1. The SMR was 3.1 for splenectomized trauma patients. The time period during which the splenectomy was performed did not impact the incidence of sepsis. Though the authors proposed several possible explanations for this lack of effect the fact that performance was worse with later time periods, additionally strengthens the conclusion that there may not be a benefit to post splenectomy vaccination. The authors findings were also counter to the suggestions of the above study. In this study time from splenectomy decreased the incidence of sepsis. Taken together, these studies highlight the ongoing danger of OPSI faced by these patients and suggest mortality is no better but no worse than sepsis of other causes. Additionally, the benefit of vaccination may be minimal and more study is needed to confirm or refute this finding as well as establish the role of booster immunization.
Article 3
Splenectomy and increased subsequent cancer risk: a nationwide population-based cohort study. Sun LM, Chen HJ, Jeng LB, Li TC, Wu SC, Kao CH. Am J Surg. 2015 Aug;210(2):243-51.
These next two papers highlight potential additional and under-reported dangers faced by asplenic patients. Both papers are from studies of the national health records of Taiwan. Taiwan maintains a national health record encompassing 99% of its citizens allowing for long term follow up in this group. Splenectomy patients were matched 1:4 based on age, gender and multiple medical comorbidities. Patients that had been asplenic for at least one year, were more than 20 and had a cancer diagnosis at baseline were excluded. Kaplan-Meier methods and the log-rank test were used to compare the overall cancer incidence rate within the cohort. Cox proportional hazard models were used to calculate hazard ratios for patients undergoing splenectomy for trauma and other cancers separately.
The asplenic patients were well matched to the non-splenectomy cohort. There was a large effect of splenectomy with respect to cancer development in the entire cohort. The effect varied between the trauma and non-trauma cohorts of splenectomy patients with respect to the types of cancers that occurred. For trauma and non-trauma patients, the incidence of cancers of the esophagus, stomach, liver and leukemia were elevated. Non-trauma splenectomies were additionally associated with head and neck cancers, breast cancers and non-Hodgkin’s lymphoma. The hazard ratios for trauma patients were generally smaller than those for non-trauma patients.
This study is an important first step in assessing this previously unrecognized potential risk of splenectomy for trauma. Although the risk of OPSI continues to be the most important consequence of splenectomy this new potential benefit to splenic salvage deserves further investigation. Future studies designed to examine this potential effect of splenectomy will need to eliminate potential confounders such as smoking or alcohol use. Confirmation of the association may also lead to recommendations for additional cancer screening in asplenic patients.
Article 4
Splenectomy in trauma patients is associated with an increased risk of postoperative type II diabetes: a nationwide population-based study. Wu SC, Fu CY, Muo CH, Chang YJ. Am J Surg. 2014 Nov;208(5):811-6.
This paper is from the same group in Taiwan as the above. In this study the same national healthcare database was used to create matched cohorts of trauma patients. Trauma patients with an ISS of 16 or greater were matched on age, gender, hypertension and hyperlipidemia. The first two matched cohorts compared three thousand patients who underwent splenectomy for trauma to three thousand that had a laparotomy for trauma that did not have a splenectomy. Also compared were six thousand patients who had a splenic injury but no splenectomy to six thousand patients who were severely injured but had no spleen injury. Kaplan-Meier analysis and Cox proportional hazards modeling was again utilized to determine the risk of developing diabetes.
In patients who underwent splenectomy the hazard ratio for the development of diabetes was 2.0 (95% CI 1.20 – 3.34) over the first three years while the overall incidence rate for diabetes was 6.68 per 1000 person years compared to non-splenectomy patients where it was 5.36. This was a statistically significant difference. When splenic injury patients were compared to those without injury there was no difference in incident diabetes. Both of the above studies represent potentially important findings however both need further confirmation. If additional evidence confirms these findings, additional emphasis should likely be placed on splenic salvage and previously abandoned ideas such as re-implantation of splenic tissue might be revisited.
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