Mrs. P is a 75-year-old woman who was well until 2 days ago when pain developed in the center of her lower back. The pain is constant and becoming more severe. There is no position or movement that changes the pain, and it is not relieved with acetaminophen or ibuprofen. It sometimes radiates in a belt like fashion across her lower back, extending around to the abdomen. She has no fever or weight loss. Her past medical history is notable for a radial fracture after falling off her bicycle 15 years ago, and breast cancer 2 years ago, treated with lumpectomy and radiation therapy. She currently takes only 1 medication, letrozole. Her last mammogram was normal 6 months ago.
At this point, what is the leading hypothesis, what are the active alternatives, and is there a must not miss diagnosis? Given this differential diagnosis, what tests should be ordered?
RANKING THE DIFFERENTIAL DIAGNOSIS
Mrs. P has several pivotal clinical findings that suggest her back pain could be due to a more serious, systemic disease rather than being nonspecific, mechanical back pain. First, she is older and has a history of cancer; both findings are associated with malignancy as a cause of back pain. Second, her age and history of a previous fracture are established risk factors for osteoporosis. In addition, aromatase inhibitors such as letrozole increase bone loss and are associated with an increased risk of fractures (OR = 1.47). Metastatic breast cancer is more emergent than vertebral compression fracture and is therefore both the leading and must not miss hypothesis. Table 7-6 lists the differential diagnosis.
Table 7-6.Diagnostic hypotheses for Mrs. P. ||Download (.pdf) Table 7-6. Diagnostic hypotheses for Mrs. P.
|Diagnostic Hypotheses ||Demographics, Risk Factors, Symptoms and Signs ||Important Tests |
|Leading Hypothesis |
|Metastatic breast cancer || |
Duration of pain > 1 month
Age > 50
Previous cancer history
Unexplained weight loss (> 10 lbs over 6 months)
|Active Alternative |
|Osteoporotic compression fracture || |
Age > 70
History of osteoporosis
Aromatase inhibitor use
On physical exam, she is in obvious pain. She is 5 ft 2 in and weighs 115 lbs. There is diffuse tenderness across her lower back, with no point tenderness of the vertebrae. There is no rash as would be seen in herpes zoster, and abdominal exam is normal. Her reflexes, strength, and sensation are all normal, and straight leg raise is negative.
Is the clinical information sufficient to make a diagnosis? If not, what other information do you need?
Since Mrs. P has no neurologic abnormalities, and plain radiographs are relatively quick to perform, it is reasonable to start with lumbar spine films. However, because of the suboptimal LR− of about ...