Introduction:

Ileal conduit (IC) is the most common type of urinary diversion in patients undergoing cystectomy, and parastomal hernia (PSH) is a frequent complication following IC. Various risk factors have been proposed for PSH, yet limited data is available on the role of musculoskeletal metrics. This study aims to assess the effect of sarcopenia and body fat metrics on the incidence of radiologic PSH following cystectomy.

Methods:

We retrospectively reviewed clinical data and preoperative abdominopelvic CT scans of patients enrolled in the Prophylactic Use of Biologic Mesh in Ileal Conduit (PUBMIC) trial (#NCT02439060). Patients with old scans (>3 months) and those with severe body deformity in whom appropriate calculation of musculoskeletal metrics was not possible were excluded. Using Synapse 3D (Fujifilm, Stamford, CT) software in a semiautomated fashion, the following metrics were calculated under the supervision of an experienced abdominal radiologist, blinded to the clinical data: visceral fat area (VFA), subcutaneous fat area (SFA), and waist circumference (WC) at the levels of upper-L3 and umbilicus (Figure-1). Additionally, psoas muscle area (PMA), measured at the level of L3, was used to assess sarcopenia, which was defined as the lowest sex-specific quartile of psoas muscle index (PMI: PMA/Ht²). Cox regression analysis was applied to examine the associations between muscle/fat metrics and the risk of radiologic PSH.

Results:

Among 146 patients enrolled in the PUBMIC trial, 137 were eligible for this study. The median (IQR) age of patients was 75 (71-80) years and 102 (74%) were male. The distribution of preoperative musculoskeletal metrics is shown in Figure-1. In a median follow-up of 22 months, 34 patients (25%) developed radiologic PSH. Using PMI cutoffs of 4.7 cm²/m² for males and 3.2 cm²/m² for females, no association between preoperative sarcopenia and PSH development was detected (HR 0.6, 95% CI 0.3-1.5, P=0.3). Univariate Cox regression analysis of radiologic factors affecting PSH are shown in Figure-2-A. Among all clinical variables, only prior abdominal radiation was associated with PSH development (HR 3.2, 95% CI 1.1-9.1; P=0.03). On multivariable analysis (Figure-2-B), SFA at the level of L3 > 220 cm² (Q3), was significantly associated with an increased risk of PSH (HR: 2.5, 95% CI 1.2-5.2; P=0.01).

Conclusion:

A higher subcutaneous fat area is associated with the development of radiologic PSH in patients undergoing cystectomy and IC. Nevertheless, no associations were found between other clinical and radiologic features, including preoperative sarcopenia and waist circumference, and risk of PSH.

Funding: Musculoskeletal Transplant Foundation