Incidence and Predictors of Symptomatic Retroperitoneal Fluid Collection Following Anterior Lumbar Interbody Fusion

Study Design Retrospective Cohort Study. Objectives To determine the incidence of symptomatic retroperitoneal fluid collections (RFCs) following anterior lumbar interbody fusion (ALIF), characterize clinical presentation, and identify independent predictors and associated complications. Methods Between 2014 and 2023, adult patients who underwent 1- to 4-level primary or revision ALIF at a single academic university-affiliated hospital were retrospectively reviewed for postoperative RFCs. Asymptomatic RFCs, <1 year follow-up, and surgical indications for trauma, malignancy, or infection were excluded. Symptomatic RFCs, including lymphoceles, hematomas/seromas, abscesses, and urinomas, were identified on postoperative MRI with final classification based on fluid aspiration when available. Multivariable logistic regression was performed to identify independent predictors of RFCs and associations with postoperative complications. Results Among 553 included patients, 44 (7.97%) developed symptomatic postoperative RFCs, most commonly seromas, presenting with abdominal pain and distension. Multi-level surgeries (aOR: 4.472), estimated blood loss ≥725 mL (aOR: 4.213), intraoperative transfusion (aOR: 3.347), L4-5 fusion (aOR: 3.186), higher ASA class (aOR: 2.291), and venous injury (aOR: 2.051) (all P < 0.05) were independent predictors of RFCs. L3-4 fusion provided a protective effect (aOR: 0.163). RFCs were associated with increased risk of subsequent deep vein thrombosis (DVT; aOR: 4.087, P = 0.007) and incision and drainage (aOR: 9.593, P = 0.005). Conclusions Symptomatic RFCs occurred postoperatively in 7.97% of ALIF cases. Multi-level fusion, blood loss ≥725 mL, intraoperative transfusion, L4-5 fusion, higher ASA class, and venous injury were independently associated with RFC development. Notably, RFCs increased risk of postoperative DVT by 4 times, underscoring the benefit of early recognition in high-risk patients.