Question: Which is accurate regarding the rationale for performing a lung scan in a patient with syndrome of inappropriate antidiuretic hormone (SIADH)? Imaging the lungs reveals bleeding as a source of SIADH. SIADH is always associated with tumor growth in the lung. Benign lung disease needs to be ruled out as a cause for ADH secretion. Malignant tumor in the lungs is the most common source of ADH secretion.