title: Outcomes of living kidney donors with medullary sponge kidney.
abstract: BACKGROUND
  Patients with medullary sponge kidney (MSK) commonly encounter recurrent nephrolithiasis. The existing knowledge on safety of donors with MSK has not been studied.
  
  
  METHODS
  We conducted a retrospective cohort study at a tertiary referral hospital to assess the outcomes of living kidney donors with MSK. All adults with MSK (N= 26) who underwent nephrectomy as living kidney donors between January 2000 and September 2014 were included. Non-donors with MSK (N= 78) were randomly selected by matching the year of birth and the comorbidity score with a ratio of 1:3 for comparison.
  
  
  RESULTS
  The incident rates of symptomatic stone were 0.7, 0.4 and 4.9 events/100 patient-years in donors, recipients and non-donors, respectively. After adjusting for history of kidney stones and baseline estimated glomerular filtration rate (eGFR), the kidney stone-related event was significantly lower in donors than in non-donors (hazard ratio 0.14; 95% confidence interval 0.01-0.66). One recipient of MSK living donor had symptomatic stone at median follow-up time of 8.4 years (interquartile range 5.6-12.4 years). None of MSK donors had hypercalciuria, hypocitraturia or hyperoxaluria prior to kidney donation. At 5 years after the index surgery date, there was no significant difference in eGFR between donors and non-donors (76.1 versus 70.9 mL/min/1.73 m2, P = 0.12).
  
  
  CONCLUSIONS
  These findings are reassuring for the safety of MSK kidney donors with normal kidney function, low kidney stone risk and no significant comorbidity.
authors.affiliation: Division of Nephrology and Hypertension, Department of Medicine, Mayo Clinic College of Medicine, Rochester, MN, USA.
authors.forename: Wisit
authors.initials: W
authors.lastname: Cheungpasitporn
authors.affiliation: Division of Nephrology and Hypertension, Department of Medicine, Mayo Clinic College of Medicine, Rochester, MN, USA.
authors.forename: Charat
authors.initials: C
authors.lastname: Thongprayoon
authors.affiliation: Division of Nephrology and Hypertension, Department of Medicine, Mayo Clinic College of Medicine, Rochester, MN, USA.
authors.forename: Brady A
authors.initials: BA
authors.lastname: Brabec
authors.affiliation: Division of Nephrology and Hypertension, Department of Medicine, Mayo Clinic College of Medicine, Rochester, MN, USA.
authors.forename: Wonngarm
authors.initials: W
authors.lastname: Kittanamongkolchai
authors.affiliation: Division of Nephrology and Hypertension, Department of Medicine, Mayo Clinic College of Medicine, Rochester, MN, USA.
authors.forename: Stephen B
authors.initials: SB
authors.lastname: Erickson
keywords: end-stage renal disease; kidney stones; living kidney donor; medullary sponge kidney; outcomes