Nucleation and Growth of Kidney Stones
The passage of a kidney stone is one of the most painful experiences that humans commonly endure. Roughly 1 in 10 of us will produce a kidney stone in our lifetimes. Stones smaller than about 6 mm usually pass without medical intervention long term effects. However, larger stones can obstruct the ureter, leading to kidney failure, infection, and ultimately, death. In the United States, with one urologist for every 27,000 people, failing to obtain the necessary medical treatment is a relatively rare circumstance. However, in the third world, the dearth of urologists manifests as a lack of treatment. For example, in Nigeria, there is a staggering 1 urologist for every 3.8 million people, suggesting that for many, urinary tract stones are life threatening.
Ultimately, kidney stones arise for the aberrant nucleation and growth of biominerals within the kidney. Kidney stones can be classified into five general categories: Ca-oxalate, hydroxyapatite (brushite), struvite, uric acid and cystine based stones. Our work is focused on the formation of cystine stones.
Cystinuria is a genetic disease that leads to an unusually high concentration of cystine (a dimer of the amino acid cysteine formed through a sulfur-sulfur bond) within the urine. Under conditions commonly encountered within urine, the cystine can crystallize. The crystals, typically about 50 microns in diameter, agglomerate to form cystine based stones. Cystinuria is a disease that afflicts roughly 1 in 7,000 people in the US alone. These people can suffer immeasurably – some pass as much as 1 kidney stone per day.
We are beginning a research effort in collaboration with Dr. Marshall Stoller’s group at the University of California, San Francisco, aimed at developing a multiscale model for the nucleation and growth cystine based kidney stones within urine. Our ultimate goal is to develop an understanding sufficiently detailed that we can explore how urine bound metabolites might interfere with their growth.