<prompt> Answer this question truthfullyWhat is the recommended imaging test for diagnosing pulmonary embolism PE in patients with renal failure GFR 30?  <response>: <reason> The recommended imaging test for diagnosing pulmonary embolism PE in patients with renal failure GFR 30 is a ventilationperfusion VQ scan. This test involves injecting a radioactive substance into the bloodstream and then using a special camera to take images of the lungs as the patient breathes in and out. In patients with renal failure, a VQ scan is preferred over a CT pulmonary angiogram CTPA, which can be harmful to the kidneys due to the use of contrast dye. The VQ scan can show a normal ventilation V and low perfusion Q pattern in areas of the lung where there is a blood clot, indicating the presence of a pulmonary embolism. 