<Tr> <Th> MeSH </Th> <Td> D006869 </Td> </Tr> <Tr> <Td_colspan="2"> (edit on Wikidata) </Td> </Tr> <P> Hydronephrosis--literally "water inside the kidney"--refers to distension and dilation of the renal pelvis and calyces, usually caused by urinary retention due to obstruction of the free flow of urine from the kidney . Untreated, it leads to progressive atrophy of the kidney . One or both kidneys may be affected . In cases of hydroureteronephrosis, there is distention of both the ureter and the renal pelvis and calices . </P> <P> The signs and symptoms of hydronephrosis depend upon whether the obstruction is acute or chronic, partial or complete, unilateral or bilateral . Hydronephrosis that occurs acutely with sudden onset (as caused by a kidney stone) can cause intense pain in the flank area (between the hips and ribs). Historically, this type of pain has been described as "Dietl's crisis". Conversely, hydronephrosis that develops gradually will generally cause either attacks of a dull discomfort or no pain . Nausea and vomiting may also occur . An obstruction that occurs at the urethra or bladder outlet can cause pain and pressure resulting from distension of the bladder . Blocking the flow of urine will commonly result in urinary tract infections which can lead to the development of additional stones, fever, and blood or pus in the urine . If complete obstruction occurs, kidney failure may follow . </P>

Hydonephrosis is caused by decreased blood flow to the kidney