References. 1  Shmerling RH. Approach to the patient with myalgia. http://www.uptodate.com/home. 2  LeBlond RF, et al., eds. The spine, pelvis and extremities. 3  Muscle cramps. Merck Manual Professional Version. 4  Sprains, strains and other soft tissue injuries. American Academy of Orthopaedic Surgeons.
Freebase(0.00 / 0 votes)Rate this definition: Hydronephrosis â literally water inside the kidney â refers to distension and dilation of the renal pelvis and calyces, usually caused by obstruction of the free flow of urine from the kidney. Untreated, it leads to progressive atrophy of the kidney.
In some children, the root cause of the hydronephrosis may never be known. While there can be many conditions that lead to hydronephrosis, the most common causes are obstructions (blockages) that reduce the ability of urine to flow out of the kidney and into the bladder. UPJ obstruction is a blockage at the point where the kidney meets the ureter (the tube that carries urine to the bladder).