Michael P. D'Alessandro, M.D.
Peer Review Status: Internally Peer Reviewed
Intrinsic narrowing of the ureteropelvic junction. The etiology of this narrowing is due to abnormalities in longitudinal muscle development or an aberrant crossing vessel. Twenty to thirty percent of cases are bilateral.
On IVP a rim of dense parenchyma around lucent dilated calyces during the nephrogram phase (rim sign) is seen. As contrast is slowly excreted into the collecting system it is diluted by urine retained in the obstructed system. Later the accumulation of contrast in collecting tubules can produce curvilinear calyceal densities (calyceal crescents).
Ultrasound shows a dilated anechoic renal pelvis surrounded by communicating dilated calyces in the kidney.
See References Chapter.
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