Renal cystic dark area generally refers to the presence of cysts in the kidneys, which contain fluid and are shown as dark fluid area by ultrasound, and need to be treated correspondingly. Renal cystic dark area is mainly related to polycystic kidney, which is mainly due to the abnormalities in the cortex and medulla of the kidney, resulting in cysts containing urine with diffuse distribution. Usually the lesions are round, with clear boundaries and relatively neat edges. The cystic dark area of the kidney may compress the renal parenchyma when it enlarges, resulting in a condition of obstruction. If the patient’s cyst is relatively small, it can be observed first to protect the basic function of the kidney. If the cyst is large, the cyst can be punctured or removed. Patients with renal cystic dark area should pay attention to rest in daily life, avoid overwork, try not to eat spicy and stimulating food, and seek medical treatment when abnormalities occur.