Case Presentation: A 21-year-old female with a past medical history significant for low-grade glioma suspicious for diffuse astrocytoma (WHO grade II) status-post partial resection and hemicraniectomy presented with left flank pain for two days. The day prior, she had been diagnosed with a urinary tract infection and prescribed cefuroxime at an outside hospital. Despite taking antibiotics, the patient had persistent left flank pain and subjective fever, prompting her to seek evaluation at our ED. Physical exam on presentation was notable for a temperature of 100.7°F, regular heart rate of 130, and left flank tenderness. Urinalysis was negative. CT abdomen/pelvis with IV contrast did not show pyelonephritis, but rather a filling defect in a subsegmental left lower lobe pulmonary artery. Follow-up CT angiogram showed bilateral pulmonary emboli. Additionally, there was a left posterior lower lobe consolidation and atelectasis, suspicious for infarction. On further questioning, the patient reported that she had been bed bound since undergoing neurosurgery 3 weeks prior. Ultrasound revealed no thrombus in her lower extremities. The patient had an inferior vena cava filter placed given the risk of intracranial hemorrhage after brain surgery with anticoagulation, with eventual resolution of her tachycardia and flank pain.

Discussion: Pulmonary embolism has been called “the great masquerader,” because it may present with nonspecific physical exam findings, such as abdominal pain, or as in these cases, flank pain. Pulmonary infarction may cause irritation of the parietal pleura and subsequent pleuritic pain. Irritation of parietal branches of intercostal nerves may also cause hyperesthesia of the cutaneous branches innervating the flank region. Fortunately for this case, PE was incidentally discovered after imaging ruled out pyelonephritis. In retrospect, her Well’s score for PE was 3.0 – 4.0, indicating moderate risk for the following criteria:  heart rate > 100, immobilization at least three days or surgery within the past four weeks, +/- malignancy with treatment (diffuse astrocytoma is not considered benign).

Conclusions: Pulmonary embolism is a potentially life-threatening event that should be considered in a physician’s differential diagnosis for patients with otherwise unknown cause of flank pain. Clinical prediction scores exist for suspected PE. However, high clinical suspicion for PE relies heavily on an accurate and thorough history and physical exam to uncover the potentially fatal disease.