Can daily passing of sand-like kidney stones be a cause of chronic lower abdominal pain? if so, how? they are calcium oxalate and phosphate stones.

Yes: The stones irritate the urinary passages causing spasm, sometimes blockage, and thus pain.

Gravel in urine: Yes - irritates bladder; To DO: Avoid dehydration; Follow this Diet: avoid spinach, rhubarb, strawberries, nuts, chocolate, tea, wheat bran, and all dry beans; increase Citrate: orange juice 8 oz twice daily; ReaLemon extract: 5 tblspns per day; increase fluid 4 liters/day; only 4 oz meat/day; 4-5 fruits/day; maintain low salt; egg white 2 per day as protein; 25 mg HCTZ (hydrochlorothiazide) daily to reduce Ca in urine