The renal ultrasound and kub x-ray shows no stones in kidneys or gall bladder but a urinal stone. what might be the reason?

Urinal in bathroom: I assume you mean a urethral stone or maybe something else but a urinal is not an anatomic structure. Stones come in all sizes and may spontaneously pass. Stones may originate anywhere along the urinary system but many start in he kidneys and pass through te ureters to the bladder and then the urethra on their way out of the body. Youse have caught one in transit or it may be stuck. If latter it.

? bladder stone: I am not quite sure but here is a possibility. Us and kub are not as sensitive as a ct study for small kidney stones, stones in the ureters or in the urinary bladder. The urinal stone might have been in the urinary bladder.