The pain in your right loin could have been caused by the renal stones.As far as the urinalysis report is concerned i would like to give you the following info...
Epithelial cells found during urine microscopy are generally of little diagnostic importance. Cells lining the urinary tract may slough into the urine.
Renal tubular epithelial cells,normally slough into the urine in small numbers. About 0-1 cells/five high power fields is considered normal. An increase in this number is sometimes seen in nephrotic syndrome.
I do not think you should be excessively worried about the "kidney cells" in your urine.
MB BS, MS, FRCS(Edinburgh)