A phantom renal calyx refers to a calyx that does not opacify after administration of contrast due to obstruction or stricture at the infundibulum. The differential diagnosis for this finding includes:
- neoplasm - most likely transitional cell carcinoma
- infection - tuberculosis, acute pyelonephritis
- stricture - due to trauma or passage of stone
- renal contusion
- ischemia/renal infarct
- congenital anomaly
Dyer RB, Chen MY, Zagoria RJ. Classic signs in uroradiology. Radiographics 2004;24:S247-80.