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PATIENT 
Mr. F is a 65-year-old man with type 2 diabetes, hypertension, and osteoarthritis who comes into your office complaining of several months of low back pain. Sometimes the pain is limited to his back, but it sometimes radiates to his buttocks, hips, thighs, and calves when he walks. Although generally achy in character, he sometimes feels numbness in both thighs. The pain gets better when he sits down, although he finds it also goes away while he is grocery shopping if he bends a bit to push the cart. He does not have pain while in bed, and he has more pain standing than sitting. Over-the-counter ibuprofen helps somewhat, but he feels quite limited in his activity. He has no fever, history of instrumentation, or injection drug use.
At this point, what is the leading hypothesis, what are the active alternatives, and is there a must not miss diagnosis?
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RANKING THE DIFFERENTIAL DIAGNOSIS
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The differential for back pain in a man this age is broad. He does not have pivotal systemic symptoms suggesting that infection should be included in the initial differential diagnosis. Exploring his history, there are 2 historical findings strongly suggesting spinal stenosis: the sensation of numbness with exertion (neurogenic or “pseudoclaudication”), and the improvement in the pain when he bends forward to push a grocery cart. Although the absence of nocturnal pain reduces the probability of metastatic cancer, that is still a possibility because of his age. Another pivotal clue is that he has risk factors for vascular disease, and so peripheral arterial disease (PAD) must be considered as an explanation for the achy, exertional leg pain. Mechanical low back pain, although common, is very unlikely given the pivotal clue of neurologic symptoms (thigh numbness). Disk herniation is a final possibility, although it would have to be a central herniation to explain the bilateral symptoms. Table 7-8 lists the differential diagnosis.
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Mr. F’s past medical history is notable for hypertension, type 2 diabetes, and osteoarthritis of his knees. He quit smoking 10 years ago, having smoked 1 pack per day for 30 years. His medications include lisinopril, glipizide, atorvastatin, aspirin, and acetaminophen or ibuprofen. He has no history of cancer, and his prostate-specific ...