Presented by: Hal Kominsky
UT Southwestern Medical Center

Introduction

Nephrolithiasis represents a significant societal burden with respect to overall healthcare cost and decreased work productivity. Pilots are particularly vulnerable as they are prohibited from flying by the Federal Aviation Association until they can demonstrate documented stone clearance. The goal of our study was to examine the clinical characteristics, in addition to metabolic and surgical outcomes in a cohort of aviation pilots with nephrolithiasis.

Materials

We performed a retrospective chart review of a cohort of aviation pilots with a radiographically confirmed diagnosis of nephrolithiasis who received care at our institution between 2006 and 2022. Demographic information, prior history of stone disease at the time of presentation, baseline metabolic parameters, stone size and location, as well as surgical and metabolic interventions were obtained from the electronic medical record.  The clinical outcomes of interest included initial stone burden, type and rate of intervention, stone composition, serum chemistry and 24-hour urine parameters.

Results

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In total, we identified 39 pilots (median age of 44, one female) who met study criteria. Twelve patients (31%) were referred from an Emergency Department encounter for a symptomatic stone episode. We found that 72% of patients reported a history of at least one previous stone episode, and 51% had previously undergone some form of stone surgery. Average symptomatic stone size at presentation was 5.0mm while mean cumulative stone burden was 10.2mm. The rate of bilateral stones was 51%. Ureteroscopy was performed at least once in 72% of patients, and two patients required a secondary procedure to clear remaining fragments. One patient underwent percutaneous nephrolithotomy, and one patient underwent shock wave lithotripsy. All patients were initially deemed to be stone free at their first follow up after surgery, determined by CT, KUB and/or renal ultrasound. Stone composition was primarily calcium oxalate in 82% of patients who underwent surgical treatment while 11% had calcium phosphate stones. Metabolic management or dietary modification was initiated in 28 patients (72%).  Medical management included initiation of indapamide, potassium citrate, and allopurinol prescribing in 28%, 44%, and 5% of patients, respectively.  Baseline 24-hour urine analysis revealed mean urine volume 2.42L, pH 6.2, sodium 219.7mg/TV, calcium 287.5mg/TV, citrate 660.2mg/TV, uric acid 738.2mg/TV, and oxalate 44.6mg/TV. At median follow up of 13.5 months, mean urine volume was 2.62 (p=0.028), pH 6.7 (p=0.148), sodium 175mg/TV (p=0.199), calcium 256.8mg/TV (p=0.807), citrate 353mg/TV (p=0.116), sodium 741.8mg/TV (p=0.976), and oxalate 41.5mg/TV (p=0.352). Four patients (10%) had a recurrent stone event. Three patients (8%) were treated with ureteroscopy, all of whom had previously been on medical management.

Conclusion

We observed a high rate of surgical intervention from outpatient referrals for aviation pilots with nephrolithiasis. These patients did not appear to have any baseline serum metabolic abnormalities and commonly had bilateral stones. Most of these patients were advised on dietary modification and or initiated on drug therapy, emphasizing that aggressive stone prevention is paramount for pilots with nephrolithiasis.

Funding

None.

Co-Authors

Mohannad Awad,
UT Southwestern Medical Center

Isaac Palma Zamora,
UT Southwestern Medical Center

Alaina Garbens,
UT Southwestern Medical Center

Vineeth Komiddi,
UT Southwestern Medical Center

Brett Johnson,
UT Southwestern Medical Center

Margaret Pearle,
UT Southwestern Medical Center