POS1272 SAFETY AND EFFICACY OF CT-GUIDED PERCUTANEOUS INFRA-RENAL PERIAORTIC BIOPSIES IN SUSPECTED RETROPERITONEAL FIBROSIS
Authors: C. Anderson, M. Guarda, U. Ghaffar, T. Atwell, K. J. Warrington, M. Moynagh, M. Koster
Journal: Annals of the Rheumatic Diseases (2024)

<h3>Background:</h3> Retroperitoneal fibrosis (RPF) commonly affects the infrarenal abdominal aorta (irAA) and manifests with periaortic soft tissue thickening (pASTT). RPF can be either idiopathic (primary) or secondary. Secondary causes include malignancy and infection and thus biopsy aids in differentiating etiologies. Data describing the safety and efficacy of pASTT biopsy sampling using computed tomography (CT)-guidance is limited. <h3>Objectives:</h3> To assess the safety and efficacy of periaortic biopsies using computed tomography (CT)-guidance among a large single institution cohort of patients with RPF. <h3>Methods:</h3> Patients undergoing CT-guided percutaneous pASTT biopsy from June 1, 1999 through September 30, 2022 were identified retrospectively. All patients were required to have radiographic evidence of soft tissue thickening/mass in direct contact with the irAA and have had CT-guided biopsy performed. Patients with biopsies of periaortic lymph nodes or the perivascular space of the iliac vessels or inferior vena cava were excluded. Routine laboratory screening thresholds prior to biopsy included INR &lt;1.6 and platelet count &gt;50 x10^9/L. Anticoagulation/antiplatelet agents were held prior to biopsy. Charts were reviewed by a physician abstractor. Demographics, biopsy features, and outcomes were collected. Complications were graded based on common terminology criteria for adverse events (CTCAE): categories 1 and 2 being minor, and categories 3-5 considered major. <h3>Results:</h3> 83 patients (28 females, 55 males) with 84 biopsies of the pASTT at the level of the irAA were identified. Mean age at biopsy was 58 (range 31-83) years. Biopsy approach was paraspinal in 73 (87%) and anterior abdominal in 11 (13%). Mean number of passes was 5 (range 1-12). A 17/18 gauge needle size was most commonly used (67/84), followed by 19/20 gauge (15/84). One biopsy used a 15/16 gauge device and one report did not specify needle size. Local anesthesia only was used in 18 (21%) biopsies, moderate anesthesia in 61 (73%) and anesthesia type was not specified in 5 (6%). Three of 84 (3.6%) biopsy events had minor bleeding at entry site. A single (1.2%) patient had a major bleeding complication with left rectus sheath hematoma from anterior abdominal approach requiring embolization of left inferior epigastric pseudoaneurysm. No post procedural infections were observed. Biopsy of the irAA soft tissue confirmed diagnosis following 73/84 (87%) biopsies (Table 1) with mean thickness at biopsy site 14.4 mm (range 3.4-27.9). In the 11 procedures where the diagnosis was not achieved by initial biopsy, 6 were due to insufficient tissue for histologic characterization [mean thickness 15.1 mm (range 5.2-25.4)] and 5 were due to concern for alternative etiology despite sufficient tissue. Among these 11 cases, 5 had subsequent open surgical biopsy, 2 had repeat CT-guided irAA soft tissue biopsy, 1 had alternative site biopsied and 3 were clinically followed (Table 2). <h3>Conclusion:</h3> In this study, percutaneous CT-guided infra-renal pASTT biopsy was considered safe and confirmed diagnosis in 87% of cases. Final diagnosis differed from pre-biopsy suspicion in 34%, highlighting benefit of this procedure. <h3>REFERENCES:</h3> <b>NIL.</b> <h3>Acknowledgements:</h3> <b>NIL.</b> <h3>Disclosure of Interests:</h3> <b>None declared.</b>