Association of Clinical and Radiographic Features with Perinephric “Sticky” Fat

Abstract

Background and Purpose: The discovery of thick, adherent, perinephric sticky fat (PSF) is relatively common during open or laparoscopic retroperitoneal surgery. To our knowledge, however, there has been no previous analysis of clinical or radiographic features associated with the development of PSF or of perioperative outcomes for those patients in whom it is found. Our objective is to analyze potential predictive features and determine whether there is any effect on clinical or pathologic outcomes for patients with perinephric sticky fat. Patients and Methods: Patients undergoing partial nephrectomy or laparoscopic cryoablation with available preoperative imaging were identified from 2005 to 2011. Operative records were reviewed to identify patients with and without PSF. Preoperative images and medical records were examined to obtain patient data regarding potential predictors as well as clinical and pathologic outcomes. Results: A total of 29 patients were identified-16 with PSF and 13 controls. Statistically significant factors associated with PSF included sex, tumor size, presence of perinephric stranding, tumor > 50% exophytic, and thickness of perinephric fat (P < 0.05). Median total operative time for patients with sticky fat was nearly 40 minutes longer than the control group (228 min vs 190 min, P < 0.05). All four (17%) patients with Fuhrman grade 3 or 4 renal-cell carcinoma were from the sticky fat group (P = 0.09). Conclusions: Despite the small sample size, multiple possible factors associated with perinephric sticky fat were identified and may provide guidance for future investigation of this phenomenon.

Adherent Perinephric Fat in Asian Patients: Predictors and Impact on Perioperative Outcomes of Partial Nephrectomy

“…Our study is the first to evaluate the incidence of APF in Asian individuals with renal malignancy. The incidence of APF in our study was 17%, which was lower than the incidence rates in previous studies of Western cohorts (30-55%) [3,4,6,13]. BMI was associated with APF in this Asian cohort as it was in the Western cohorts, although the mean BMI (24 kg/m 2 ) in our study was smaller than those in Western studies (29-33 kg/m 2 ) [5,6,12].…”

“…In other studies, radiographic features have been said to be independent predictors of APF [12,13]. The MAP score has broad utility because it can be calculated based on both computed tomography and T1-weighted magnetic resonance imaging [6].…”

Mayo Adhesive Probability Score: An Accurate Image-based Scoring System to Predict Adherent Perinephric Fat in Partial Nephrectomy

“…These findings have been mirrored in the urology literature as well. IAF, as measured by perirenal fat thickness, was a better predictor than outer abdominal fat or BMI in predicting longer operative times, postoperative complications, and estimated blood loss for patients undergoing PN [7,18,19]. These studies fail to elucidate the reason why surgery in patients with increased IAF is so fraught with complications.…”

“…Bylund et al first sought to elucidate certain characteristics that may be associated with APF encountered intraoperatively during PN [19]. Male sex, stranding, and increased thickness of perinephric fat were all associated with the finding of APF in a cohort of 29 patients.…”

“…Therefore, we did not include an analysis of the impact of APF on the outcomes of RAPN. In the only studies thus far examining APF along with operating room variables, APF was shown to predict longer operating room times for PN [14,19]. APF alone may be a surrogate for surgical complexity and may push less experienced partial nephrectomists to select an alternative approach, such as an open PN or an ablation, for treating small renal masses in these particular patients.…”