Crescent Sign

Crescent Sign

Imaging—bone A curved subcortical radiolucency corresponding to a fracture line and bony collapse, which is seen in early ischemic necrosis of the epiphysis of the femoral head, a finding that may also be seen in the humoral head, and accentuated by traction. Fractures that occur in subchondral bone may be recognised by a crescentic lucent zone that separates the fragment from the remainder of the femur
Imaging—kidneys A scalloped, curved radiolucency, seen in the kidneys 2º to chronic lower urinary tract obstruction—e.g., concrement-induced obstruction—in early phases of urography; the crescent is due to accumulation of radio-contrast material within flattened collecting tubules, and indicates residual renal function—in contrast to the rim sign, in which there is no renal function by angiography