A phantom calyx is a solitary calyx which fails to opacify with contrast amidst an otherwise well-opacified pelvicalyceal system. It is due to an intrarenal process which has infiltrated and caused obliteration of the involved collecting system element.
It may be seen in:
- tumor: especially transitional cell carcinoma of the renal pelvis
- renal tuberculosis
- acute pyelonephritis
- renal calculus
- renal ischemia
- renal trauma
- congenital anomaly
- renal contusion
- technical underfilling
If the calyx is dilated and filled with tumor (but still visible) then it is referred to as an oncocalyx.
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