A Low Psoas Muscle Index Was Associated With a Poorer Overall Survival in Patients Who Underwent Percutaneous Nephrostomy

ABSTRACT Introduction Malignant ureteral obstruction (MUO) caused by urological, gynecological, and gastrointestinal cancer requires a nephrostomy or ureteral stenting to preserve the renal function and prevent pain and urinary tract infections. Recent investigations have revealed the importance of low skeletal muscle mass as a poor prognostic factor in various solid malignancies. This study investigated the importance of a low psoas muscle index (PMI) as a prognostic factor for MUO patients who have undergone nephrostomy. Materials and Methods A total of 89 percutaneous nephrostomies were created from July 2008 to March 2016 in our institutions. Fifty‐seven of these patients had MUO. The psoas muscle volume was calculated at the L3 level using axial computed tomography images obtained prior to nephrostomy. The PMI was calculated using the following formula: (left psoas muscle area at the level of L3 [mm 2 ]) / (body height [m]) 2 . Results In these 57 patients, 41 cases (71.9%) were male, and 16 (28.1%) were female. The median (mean ± SD) age was 70 (69.0 ± 9.6) years old in males and 68 (66 ± 13.5) years old in females. A low PMI was associated with a significantly poorer overall survival in male MUO patients (log‐rank p = 0.018), whereas no significant difference was observed in female patients ( p = 0.861). In the multivariate Cox proportional hazards regression analysis, a low PMI was identified as an independent predictor of poor overall survival (HR: 2.29, 95% CI: 1.05–5.03, p = 0.038). Conclusion Among male patients who underwent percutaneous nephrostomy, a low PMI was associated with poor overall survival, suggesting its utility as a prognostic indicator in this population.