Hydronephrosis with back pain is mainly caused by urinary tract obstruction, and common causes include urinary tract stones, genitourinary tumors, prostate hyperplasia, congenital developmental anomalies and so on. When urine refluxes or accumulates in the kidneys because of the above pathologic conditions, it leads to increased intrarenal pressure, renal parenchyma atrophy, and reduced function triggering kidney stones with back pain. Urinary stones can be found in genitourinary structures such as renal calyces, renal pelvis, ureters, bladder, and urethra. Genitourinary tumors include kidney cancer, renal pelvis cancer, ureter cancer, bladder cancer urethra cancer, and penile cancer. An enlarged prostate can also press on the urethra causing obstruction, and is classified as physiological (enlargement with age) and pathological (tumors, etc.). If the stenosis of renal pelvic ureteral junction, ectopic opening of ureter and other developmental abnormalities are easy to cause urinary tract obstruction, which will lead to kidney stones. In conclusion, patients with hydronephrosis with back pain should go to regular hospitals for further examination to clarify the cause of the disease, and follow the doctor’s instructions to treat the cause of the disease.