It’s summer, and that is officially the season of the weekend warrior. You know who I’m talking about because you see them every week in your clinic. They decided to take on a new gardening project, a strenuous workout or tried water-skiing for the first time in decades, and now, a few days later they come to you with pain in their lower back.
Add the summer olympics where many think, “I could totally do the steeple chase.” And you have a recipe for disaster.
Acute low back pain is among the most common chief complaints in the outpatient setting. Most patients with acute back pain in the outpatient setting have a benign, musculoskeletal etiology of their pain. It’s the small percentage of patients who have serious, “can’t miss” etiologies that make any clinician anxious.
Considering a broad differential diagnosis for your patient with acute low back pain will help you to not miss serious etiologies. One of the easiest ways to remember the differential diagnosis for acute low back pain is SOS: Spinal, Outside, Serious.
| Spinal Causes | Lumbar sprain/strain, compression fracture ( traumatic mechanism), herniated disc/radiculopathy, spinal stenosis, spondylosis (degenerative disk or facet joint arthropathy), spondylolysis, spondylolisthesis, ankylosing spondylitis, scoliosis |
| Outside Causes | Referred pain from abdominal pathology (AAA, pancreatitis, PUD, cholecystitis, PID, prostatitis, pyelo, kidney stone), zoster |
| Serious Causes | Cauda equina syndrome, malignancy, spinal epidural abscess (SEA), vertebral osteomyelitis, AAA |
Once you have a thorough list of differentials, you can use your good history and physical exam skills to narrow down that list and identify the appropriate diagnosis for your patient or at least rule out the really bad stuff. We’ve created a chart for key history clues for all of the low back pain differentials for you to screenshot and reference on your next clinical shift:
| Category | Differential Diagnosis | Key History Clues and Symptoms |
| Spinal | Lumbar sprain/strain | Diffuse pain that may radiate to the buttock but not the legs, worse with movement, better with rest, commonly known triggering event |
| Compression fx | H/o osteoporosis, trauma, h/o steroid use, pain worse with flexion and when moving from laying to sitting and sitting to standing | |
| Herniated disc/ radiculopathy | Leg pain > back pain, radiation of pain to the hip/thigh (L1-L3) or below the knee (L4-S1), worse when sitting, typically unilateral | |
| Spinal stenosis | Leg pain > back pain, worse with standing/walking, improves with rest and flexed spine (“shopping cart sign”) | |
| Spondylosis | Degenerative disk → worse with sitting, flexing Facet arthropathy → worse with extension, standing, walking |
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| Spondylolysis | Repeated hyperextension activities, pain worse with extension | |
| Spondylolisthesis | Leg pain > back pain, worse with standing/walking, improves with rest and flexed spine | |
| Ankylosing spondylitis | Pain at night, morning pain and stiffness, improved with activity, associated red eye (uveitis) | |
| Scoliosis | Fatigue in lower back with prolonged sitting/standing | |
| Outside | AAA | Tearing back pain, unstable vitals |
| Pancreatitis | H/o ETOH or gallstones, pain better sitting and leaning forward, pain is “boring” | |
| PUD | H/o NSAID use, pain associated with meals | |
| Cholecystitis | Severe, steady pain, possible R shoulder radiation, +/- fever, +/- N/V | |
| PID | H/o or risk for STI | |
| Endometriosis | H/o dysmenorrhea, dyspareunia, infertility | |
| Prostatitis | Urinary symptoms | |
| Pyelonephritis | Urinary symptoms, fever | |
| Kidney Stone | Hematuria, colicky pain | |
| Zoster | Burning pain | |
| Serious | Cauda Equina Syndrome | Bowel/bladder dysfunction (incontinence, urinary retention), saddle anesthesia, motor weakness, progressive sensory loss |
| Malignancy | Unintentional weight loss, fever, night sweats, nighttime pain, history of cancer (esp. breast, lung, prostate) | |
| Spinal epidural abscess | Fever, constant pain, PWID, recent surgery/spinal injection, recent bacteremia | |
| Vertebral osteomyelitis | Gradual onset of pain |
Armed with your SOS tool, we hope you feel more confident on your next shift when you see “low back pain” come up on your schedule. For more practical clinical pearls, check out our NP Clinical Resource Guide, available for free to all practitioners.