In-Hospital Outcomes of Hemolytic Uremic Syndrome: A Perspective from the Last Decade

Introduction: Hemolytic Uremic Syndrome (HUS) is a condition characterized by progressive renal failure that is associated with microangiopathic hemolytic anemia and thrombocytopenia. It is a clinical syndrome which occurs as an immune reaction, most commonly after a gastrointestinal infection. Several studies have reported the prevalence of HUS among children but it is not well studied among adults. Studies have shown mortality rates ranging up to 20% and may go up to to 50% if HUS is complicated by end stage renal failure. There is limited data regarding HUS, especially among the adult population in regards to hospitalization trends and outcomes. In this study we aimed to describe the hospitalization trend, patient characteristics and in-hospital outcomes of HUS using a nationally representative database.

Methods:

Study cohort was from the Nationwide Inpatient Sample (NIS) for the years 2008-2017 for hospitalizations due to HUS by using International Classification of Diseases (9th/10th Editions) Clinical Modification diagnosis codes ICD-9-CM/ICD-10-CM). Other diagnosis and comorbidities were also identified by ICD-9/10-CM codes and Elixhauser comorbidity software. Our primary outcome was a discharge disposition following HUS hospitalization. We utilized multivariable survey logistic regression models to analyze and identify predictors of poor outcomes.

Results:

Between 2007-2018, a total of 8,043 hospitalizations occurred due to HUS. Hospitalization trend due to HUS increased from 528 (6.57%) in 2007 to 800 (9.95%) in 2013 and then reduced to 620 (7.7%) in 2018. Study cohort consisted of children <10 years of age (56.2%) followed by 18-65 years of age (24.7%). Out of total HUS patients, 74.4% were Caucasians and 59.3% were females. Overall in-hospital mortality of hospitalization due to HUS was 3.0%, and discharge to the facility was 15.7%. In trend analysis, the proportion of discharge to facility decreased from 23.1% in 2007 to 14.5% in 2018 but in-house mortality increased from 1% in 2007 to 3.2% in 2018. Median Length of hospital stay was 8-days (interquartile range 3-day to 15-days). Furthermore, in multivariable logistic regression analysis, age above 65 years (OR 2.5; 95%CI 1.4-5.8; p=0.0023), rural hospital (OR 17.9; 95%CI 8.9-36.1; p<0.001) and urban-non teaching hospital (OR 5.2; 95%CI 3.4-8.1; p<0.0001) and small-medium size hospitals were also associated with higher odds of discharge to facility among HUS patients.

Conclusion:

Our study estimates the epidemiology of hospitalizations due to HUS in the United States from a nationally representative database. In this study we observe that the burden of hospitalizations due to HUS has been increased over the study period. We also identified factors associated with poor discharge outcomes and some of which are modifiable. Further studies are warranted for developing strategies for better risk stratification of HUS patients to improve the overall outcomes.