Pyeloplasty is the surgical reconstruction or revision of the renal pelvis to drain and decompress the kidney. Most commonly it is performed to treat an uretero-pelvic junction obstruction if residual renal function is adequate. Drawing of a swollen kidney that results from ureteropelvic junction obstruction. This revision of the renal pelvis treats the obstruction by excising the stenotic area of the renal pelvis or uretero-pelvic junction and creating a more capacious conduit using the tissue of the remaining ureter and renal pelvis.