Ultrasound-based assessment of muscle mass is associated with early recovery after kidney transplant: a prospective single-center study.

Background: Low muscle mass and frailty are associated with worse perioperative outcomes. However, traditional modalities for quantifying muscle mass are limited, costly, may require radiation exposure, and can be unreliable with kidney failure. We hypothesize that ultrasound-measured muscle mass is associated with early recovery metrics after kidney transplant.

Methods: In a prospective single center cohort study, we investigated the association between muscle mass and short-term outcomes after kidney transplant. Patients undergoing kidney transplant between November 2019 and October 2020 were enrolled. We quantified muscle mass by ultrasound measurement of the rectus femoris cross-sectional area. The primary outcome was the number of days alive and out of hospital within 30 days of surgery. Incidence of surgical complications by the Clavien-Dindo system was also evaluated.

Results: Thirty-eight patients were enrolled with 36 completing kidney transplant. Median cross-sectional area was 4.82cm² [IQR 4.18 to 6.05] and median days alive and out of hospital was 26 [IQR 24 to 27]. Lower muscle mass was associated fewer days alive and out of hospital postoperatively. Cross-sectional area was 4.35cm² [IQR 4.11 to 5.79] versus 5.49cm² [IQR 4.94 to 6.55] for those at or below versus above the median days alive and out of hospital respectively (p = 0.046). Lower muscle mass was associated with occurrence of at least one surgical complication. Cross-sectional area was 4.30cm² [IQR 4.11 to 4.91] versus 5.46cm² [IQR 4.35 to 6.84] for those who did and did not experience a complication respectively (p = 0.024).

Conclusions: Lower muscle mass as measured by point-of-care ultrasound was associated with fewer days alive and out of hospital and more surgical complications after kidney transplant. Further studies should explore the role that ultrasound-measured muscle mass can play in guiding the pre-surgical care of patients prior to kidney transplant.