In less than 1% of patients who present to primary care with a chief complaint of back pain, the cause is a malignant neoplasm (primary or metastatic), spinal cord compression, cauda equina syndrome, or infection. To decide which patients require further evaluation with advanced imaging, look for "red flag" signs and symptoms in conjunction with risk factors and select the imaging modality that is best suited to the specific clinical concern.
Pain that begins abruptly and is associated with point tenderness is suggestive of spinal fracture, and plain radiography (less radiation but less sensitive) or CT (more radiation but also more sensitive) should be considered to evaluate for bone abnormalities. Weakness that correlates with a spinal sensory level raises concern for spinal cord injury. Bladder or bowel incontinence or retention suggests spinal cord compression. The spinal cord is best imaged with MRI; thus, this modality is preferred for evaluating pathology of the spinal cord.
A history of cancer raises suspicion for metastatic disease, which can cause vertebral compression, fractures, and/or spinal cord compression. A history of intravenous drug use places a patient at risk for vertebral osteomyelitis or an epidural abscess. If vertebral fractures are suspected, CT is adequate in most cases. If cord compression from metastatic disease or an abscess is suspected, MRI is generally preferred.
The patient in this case had urinary retention and signs of cord compression (arm weakness) on physical examination. Although vertebral injury was suspected, the most urgent concern was for cord compression. In addition, avoiding ionizing radiation when feasible is desirable in children because they have more active cell division than adults do and are thus at higher risk for the mutagenic effects of ionizing radiation (as involved in CT). For all these reasons, MRI was used in this case.
Last, this case is an interesting example of spinal cord injury without radiographic abnormality (SCIWORA), defined as objective signs of neurologic deficits or reported paresthesia, numbness, or paralysis, without findings on plain radiographs or CT. With the advent of MRI, a reported two thirds of cases that were historically considered to be SCIWORA exhibited evident pathology on MRI. This case reinforces the importance of considering the possibility of spinal cord injury in the presence of new or progressing neurologic findings and the absence of initial radiographic evidence.
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Cite this: Liana Meffert, Daniel Miller. A 12-Year-Old With Urinary Retention Who Can't Grasp Objects - Medscape - Apr 18, 2022.