Abstract
Glomerular filtration rate (GFR) is a direct measurement of renal function. While clearance tests using 24-hour urine collection or blood sample series are gold standards for measuring GFR, serum-based prediction of GFR based upon the Modification of Diet in Renal Disease (MDRD) Study equation is acceptable for routine use in human adults.1,2 The purpose of our study was to assess the ability for a dolphin-adjusted MDRD Study equation (GFR (mL/min/2.78m2) = 186 x serum creatinine-1.154 x 1.61) to predict expected changes in GFR by age, sex, and fasting status in bottlenose dolphins (Tursiops truncatus) using a healthy dolphin population represented by 1,103 routine serum samples collected from 50 dolphins of all age groups, years 1998-2005. Additionally, we applied the dolphin-modified MDRD Study equation to estimate GFR from serum collected from a 32 year old male dolphin with end-stage renal disease and among adult cases and controls with or without renal calculi, respectively. The dolphin-adjusted MDRD equation estimated GFR changes in our population that paralleled what has previously been reported in other mammals, including decreasing estimated GFR with age (P < 0.01)3,4; higher estimated GFR in dolphins that had recently eaten (P < 0.01)4; and rapidly decreasing estimated GFR in the animal with end-stage renal disease2. Animals with greater than 15 renal calculi were significantly more likely to have lower estimated GFR compared to animals without renal calculi (P < 0.01), indicating that a high number of renal calculi can impair renal function. We conclude that a serum-based GFR prediction equation may be an easy and feasible means of detecting and tracking renal function in adult bottlenose dolphins. Future studies need to assess the accuracy of this equation in young, growing dolphins.
Acknowledgements
We thank our colleagues at the Navy Marine Mammal Program for their assistance in entering and managing medical data and samples at the Navy Marine Mammal Program. This project was partially funded by the Office of Naval Research.
References
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