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PATIENT
Mr. Y is a 30-year-old man with low back pain that has lasted for 6 days.
What is the differential diagnosis of low back pain? How would you frame the differential?
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CONSTRUCTING A DIFFERENTIAL DIAGNOSIS
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Most low back pain is caused by conditions that are troublesome but not progressive or life-threatening. The primary task when evaluating patients with low back pain is to identify those who have a serious cause of back pain that requires specific, and sometimes rapid, diagnosis and treatment. In practice, this means distinguishing serious back pain (pain due to a systemic or visceral disease or pain with significant neurologic symptoms or signs) from nonspecific back pain related to the musculoskeletal structures of the back, called mechanical back pain. The framework for the differential diagnosis reflects this task.
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Back pain due to disorders of the musculoskeletal structures
Nonspecific (mechanical) back pain: no definite relationship between anatomic abnormalities seen on imaging and symptoms
Specific musculoskeletal back pain: clear relationship between anatomic abnormalities and symptoms
Lumbar radiculopathy due to herniated disk, osteophyte, facet hypertrophy, or neuroforaminal narrowing
Spinal stenosis
Cauda equina syndrome
Back pain due to systemic disease affecting the spine
Serious and emergent (requires specific and often rapid treatment)
Neoplasia
(1) Multiple myeloma, metastatic carcinoma, lymphoma, leukemia
(2) Spinal cord tumors, primary vertebral tumors
Infection
(1) Osteomyelitis
(2) Septic diskitis
(3) Paraspinal abscess
(4) Epidural abscess
Serious but nonemergent (requires specific treatment but not urgently)
Osteoporotic compression fracture
Inflammatory arthritis
Back pain due to visceral disease (serious, requires specific and rapid diagnosis and treatment)
Retroperitoneal
Aortic aneurysm
Retroperitoneal adenopathy or mass
Pelvic
Prostatitis
Endometriosis
Pelvic inflammatory disease
Renal
Nephrolithiasis
Pyelonephritis
Perinephric abscess
GI
Pancreatitis
Cholecystitis
Penetrating ulcer
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Figure 7-1 reorganizes the differential diagnosis using pivotalpoints and outlines the diagnostic approach to low back pain. In every patient with back pain, it is essential to systematically ask about and look for the clinical clues and pivotal points associated with serious causes of back pain (Table 7-1). In patients with positive findings, the initial patient-specific differential is quickly limited to serious systemic causes of back pain or specific musculoskeletal back pain. Likelihood ratios (LRs) for these findings, when available, will be discussed later in the chapter. It is also essential to understand the clinical neuroanatomy of the lower extremity to properly examine patients with low back pain (Figures 7-2 and 7-3).
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Mr. Y felt well until 1 week ago, when he helped his girlfriend move into her third floor apartment. Although he felt fine while helping her, the next day he woke up with diffuse pain across his lower back and buttocks. He spent that day lying on the floor, with some improvement. Ibuprofen has helped somewhat. He feels better when he is in ...