title: Hemorrhagic Complications of Percutaneous Cryoablation for Renal Tumors: Results from a 7-year Prospective Study.
abstract: OBJECTIVE
  Cryoablation of renal tumors is assumed to have a higher risk of hemorrhagic complications compared to other ablative modalities. Our purpose was to establish the exact risk and to identify hemorrhagic risk factors.
  
  
  METHODS
  This IRB approved, 7-year prospective study included 261 renal cryoablations. Procedures were under conscious sedation and CT guidance. Pre- and postablation CT was obtained, and hemorrhagic complications were CTCAE tabulated. Age, gender, tumor size, histology, and probes number were tested based on averages or proportions using their exact permutation distribution. "High-risk" subgroups (those exceeding the thresholds of all variables) were tested for each variable alone, and for all combinations of variable threshold values. We compared the subgroup with the best PPV using one variable, with the subgroup with the best PPV using all variables (McNemmar test).
  
  
  RESULTS
  The hemorrhagic complication rate was 3.5 %. Four patients required transfusions, two required emergent angiograms, one required both a transfusion and angiogram, and two required bladder irrigation for outlet obstruction. Perirenal space hemorrhage was more clinically significant than elsewhere. Univariate risks were tumor size >2 cm, number of probes >2, and malignant histology (P = 0.005, 0.002, and 0.033, respectively). Multivariate analysis showed that patients >55 years with malignant tumors >2 cm requiring 2 or more probes yielded the highest PPV (7.5 %).
  
  
  CONCLUSIONS
  Although older patients (>55 years old) with larger (>2 cm), malignant tumors have an increased risk of hemorrhagic complications, the low PPV does not support the routine use of embolization. Percutaneous cryoablation has a 3.5 % risk of significant hemorrhage, similar to that reported for other types of renal ablative modalities.
authors.affiliation: Vascular and Interventional Radiology, Johns Hopkins University, Baltimore, MD, USA. bkakara1@jhmi.edu.
authors.forename: Bharat
authors.initials: B
authors.lastname: Kakarala
authors.affiliation: Biostatistics and Epidemiology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD, USA.
authors.forename: Constantine E
authors.initials: CE
authors.lastname: Frangakis
authors.affiliation: Urologic Surgery, University of Texas Health Science Center, San Antonio, TX, USA.
authors.forename: Ron
authors.initials: R
authors.lastname: Rodriguez
authors.affiliation: Johns Hopkins University, 1800 Orleans Street-Sheikh Zayed Tower-Suite 7203, Baltimore, MD, USA.
authors.forename: Christos S
authors.initials: CS
authors.lastname: Georgiades
mesh_terms: D055011:Ablation Techniques / Q000009:adverse effects* / Q000379:methods; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000792:Angiography; D016292:Procedural Sedation; D003452:Cryosurgery / Q000009:adverse effects* / Q000379:methods; D005260:Female; D006801:Humans; D007680:Kidney Neoplasms / Q000473:pathology / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D019106:Postoperative Hemorrhage / Q000209:etiology*; D011446:Prospective Studies; D012307:Risk Factors; D025321:Surgery, Computer-Assisted / Q000009:adverse effects* / Q000379:methods; D014057:Tomography, X-Ray Computed
keywords: Ablation; Cryoablation; Hemorrhage; Percutaneous; RCC; Renal cancer