What would cause urine to appear grey on ultrasound? need to go back for more testing.

Medicines: Only cause of urine turning grey is if you are taking some medicines.

Blood or debris: Normal urine is black on ultrasound when black background setting chosen. Grey happens when blood, infectious or other debris present. If related to infection, should clear when infection treated. Blood can be caused by infection, trauma, cancer or bleeding disorder along with more rare causes.