Hydronephrosis means the kidney's drainage system is swollen because urine is not flowing out normally.
Symptoms can include pain in the side, back, or lower abdomen, difficulty passing urine, blood in the urine, fever, or needing to pass urine more often.
Imaging helps confirm the swelling, show whether one or both kidneys are affected, and look for the cause such as a stone, stricture, mass, or enlarged prostate.
Ultrasound, CT, or urogram-type imaging can help show the swelling and look for the reason, such as a stone, mass, or narrowing.
Treatment focuses on relieving the blockage and protecting kidney function, sometimes with stents or nephrostomy tubes.
This entry explains the finding. The next step is having a radiologist interpret your specific scan, not a general definition.