Background: Splanchnic venous thrombosis (SVT) is a well-known complication in pts with Philadelphia-negative myeloproliferative neoplasms (MPN), including polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). We evaluated epidemiologic and clinical characteristics associated with SVT in hospitalized MPN pts and their impact on in-hospital outcomes.

Method: We queried the National Inpatient Sample (NIS) database from 2016 to 2022 to identify hospitalizations involving adults (age ≥18 years) with PV, ET, and PMF using ICD-10-CM codes. SVT was defined as portal or hepatic vein thrombosis and included if listed among the top three discharge diagnoses. The primary outcome was in-hospital mortality; secondary outcomes included length of stay (LOS) and major complications. We compared demographics between SVT and non-SVT cohorts using t-tests and chi-square tests and performed multivariate logistic regression adjusting for age, sex, race, primary payer, income quartile, hospital characteristics, and Charlson Comorbidity Index (CCI). We further analyzed clinical characteristics among the following 4 groups: MPN with cirrhosis, MPN without cirrhosis, no MPN or cirrhosis, cirrhosis only. p<0.05 was deemed statistically significant.

Results: We identified 181,818 MPN hospitalizations. In the overall MPN cohort, ET accounted for 139,641 (78.6%) pts, PV 26,803 (15.1%) pts, and PMF 11,176 (6.3%) pts. 1,212 (0.67%) pts had portal or hepatic vein thrombosis. ET was the most common subtype in SVT with 677 (60.3%) pts, PV 344 (30.6%) pts, and PMF 102 (9.1%) pts. SVT pts were younger (median age 57 vs. 64 years, p<0.001), with fewer aged ≥60 (44.1% vs. 55.9%, p<0.001). Females comprised 54% in both. The SVT cohort had a slightly higher proportion of White (68.3% vs. 67.4% p<0.001) and Hispanic pts (11.5% vs. 9.8% p<0.001), while African American pts were more represented in the non-SVT group (12.1% vs. 16.7%, p<0.001). The mean CCI was significantly higher among SVT pts (3.02 vs. 2.67, p<0.001).

Mortality was 2.4% in MPN pts with SVT and 3.3% in pts without SVT (p=0.065). In multivariate analysis, SVT was not an independent predictor of in-hospital mortality. Age≥60 years was strongly associated with higher odds of mortality (aOR 2.05, p <0.001). Female sex was associated with lower odds compared to males (aOR 0.88, p <0.001). African American pts had lower odds (aOR 0.87, p =0.001) than Whites. Compared to Medicare, Medicaid was associated with slightly reduced mortality (aOR 0.88; p =0.012). Income was not associated with mortality. Urban teaching hospital was associated with higher mortality compared to rural hospital (aOR 1.14, p=0.018). Pts with higher CCI had increased mortality: CCI of 1–2 (aOR 2.16, p <0.001) and CCI≥3 (aOR 4.40, p <0.001). There was no statistically significant difference in LOS (7.78 vs 7.77 days).

Non-cirrhotic MPN pts with SVT had a significantly higher prevalence (p<0.001) of hepatic conditions compared to those without SVT, for portal hypertension (20.0% vs. 0.3%), and esophageal varices (12.6% vs. 0.1%). Rates of complications differed (p<0.001) for liver failure (4.3% vs. 0.7%), GI hemorrhage (3.4% vs. 1.7%), SBP (1.5% vs. 0.1%), bowel infarction (4.6% vs. 0.2%) and DIC (0.7% vs. 0.2%) but not in rates of shock (1.7% vs. 1.2%, p=0.304). Sepsis incidence was increased in the non-SVT group (12.8% vs. 18.6%, p <0.001). In direct comparison with the other three cohorts, non-cirrhotic MPN pts with SVT were the youngest, with 396 (43.8%) pts aged ≥60 (p<0.001). CCI≥3 (41.3%, p<0.001) and mortality (2.2%, p<0.001) were lowest in this cohort, while LOS was the longest (7.83 days, p<0.001).

Conclusion: In this large national cohort of hospitalized MPN pts, SVT was an uncommon but clinically distinct disease associated with younger age, higher comorbidity burden, and a significantly elevated risk of liver-related complications, even in the absence of cirrhosis. Non-cirrhotic MPN pts with SVT had the lowest mortality and highest LOS among the four subgroups analyzed. Independent predictors of higher mortality included age≥60, male sex, higher CCI, White race, and urban teaching hospital location. Limitations include the retrospective design, potential coding inaccuracies, and that we did not capture all SVT types (e.g., mesenteric or splenic vein thrombosis). Our findings provide new data on the epidemiology of SVT in MPN pts and the potential for tailored management strategies.

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2025
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