Abstract: A majority of kidney stones are calcium stones, with calcium oxalate (CaOx) and calcium phosphate (CaP) accounting for approximately 80% of all of these stones. Especially, alkalic urine predisposes calcium phosphate to form crystals. Renal tubular acidosis (RTA) patients easily lead to alkaline urine (pH>6.5) meanwhile are prone to free calcium from bone due to acidosis in vivo, and then cause osteoporosis and hypercalciuria. It is easy to form tiny calcium phosphate stones in urine since alkali status. Thus tiny crystals may clog pipes inside of the instrument during analysis for urine sample and it cannot provide the correct data to distinguish the types of renal tubular acidosis. In this paper, we use Minisart 0.20 um filter to filtrate the urine samples, to remove the crystals and then protect the machine. It can also avoid centrifugal heat which may cause evaporation of the volatile components and leads to errors of gas analysis. Results: We make an effective differential diagnosis of a recurrent renal stone patient. We also performed the sodium bicarbonate loading test kidney stone patients and finally diagnosed as Sjögren's syndrome induced secondary distal renal tubular acidosis.Abstract: A majority of kidney stones are calcium stones, with calcium oxalate (CaOx) and calcium phosphate (CaP) accounting for approximately 80% of all of these stones. Especially, alkalic urine predisposes calcium phosphate to form crystals. Renal tubular acidosis (RTA) patients easily lead to alkaline urine (pH>6.5) meanwhile are prone to free calcium fr...Show More