Low density foci in the right kidney can be seen in nephrology or urology, because the most common low density foci in the right kidney are cysts or hydronephrosis in the right kidney, which will be shown as low density foci on the ultrasound, but the possibility of renal occupancy should also be excluded. Therefore, it is recommended that patients with hypodense foci in the right kidney should have CT or enhanced CT of the urinary tract to further clarify the diagnosis. The most likely hypodense foci in the right kidney are renal cysts, which are divided into congenital and acquired renal cysts; congenital renal cysts are commonly found in polycystic kidneys, and acquired cysts are mostly single or multiple, but do not destroy the function of the kidney. Small kidney cysts usually do not require treatment, but if they are more than five centimeters, cyst puncture and aspiration can be considered.