Name: Low back pain — bulletproof documentation — ER Toolkit
Creator: Kim Trinh, MD

About 85% of low back pain is benign and self-limited — and imaging it changes nothing. The job is to find and document the few dangerous exceptions, and to chart a neurologic exam specific enough that the next clinician can monitor against it.

01What's at stake

The liability in back pain is the missed can't-miss: cauda equina syndrome, spinal epidural abscess, malignant cord compression, a leaking abdominal aortic aneurysm read as "muscular," or an epidural hematoma in an anticoagulated patient. These are uncommon — until the patient has cancer, injects drugs, is anticoagulated, is post-procedure, or is over 50 — and then they are very real. The defensible chart shows you screened for red flags and that your exam matched your disposition.

02Can't-miss differential

Cauda equina syndrome — urinary retention is the most sensitive finding (~90%); the chance of CES without retention is ~1:10,000.
Spinal epidural abscess — fever + back pain ± neuro deficit; fever is absent in over half of cases, and ~20% have no classic risk factor. MRI with contrast; ESR/CRP support.
Malignant cord compression / metastasis — known cancer, weight loss, night pain, age >50.
Vertebral osteomyelitis / discitis — IV drug use, bacteremia, fever; no single test rules it out.
Spinal epidural hematoma — anticoagulation, post-LP/epidural/surgery; indistinguishable on exam alone.
Abdominal aortic aneurysm — older patient, back/flank/groin pain, syncope, transient hypotension.

03History — the red flags (ask & chart the negatives)

Saddle anesthesia, urinary retention/overflow, bowel incontinence? → cauda equina
Fever, IV drug use, immunosuppression, recent bacteremia or spinal procedure? → epidural abscess / discitis
History of cancer, unexplained weight loss, night pain? → metastasis / cord compression
Anticoagulation, post-LP/epidural/surgery, new deficit? → epidural hematoma
Age >50 (or <20), known aneurysm, syncope, diaphoresis? → AAA
Progressive motor deficit, bilateral leg weakness? → cord / cauda compression
No single red flag rules serious pathology in or out — weigh them in combination; more than one together should raise suspicion. Most cauda equina patients have chronic back pain (~70%) with an acute worsening (~89%) before presentation.

Skip the typing

Work the case in the Low Back Pain Workup — it records the red-flag screen, the documented neuro exam, the post-void residual, and inflammatory markers, and assembles a copy-paste MDM that shows the dangerous causes were considered and excluded.

04Exam — and the test that matters most

Document each neuro component individually — never "WNL." Strength, sensation, reflexes, gait, and (when relevant) perineal sensation and rectal tone. This baseline is what subsequent providers monitor against.
Post-void residual (PVR) by catheter or bladder scan — the single best ED test for cauda equina. PVR >100 cc can be abnormal; >300 cc is always abnormal. Urinary retention is ~90% sensitive for CES. "Able to urinate" does not exclude retention — patients with cord compression can pass some urine and still retain; measure anyway.
Abdomen & vascular — palpate the aorta, check for a pulsatile mass and symmetric distal pulses; bedside ultrasound for AAA is highly accurate in EP hands.
Straight-leg raise — sensitive (~91%) but not specific (~26%) for radiculopathy; crossed SLR is the reverse (specific ~88%).

05Testing & evidence

No routine imaging. For nonspecific back pain, imaging does not improve outcomes (Chou meta-analysis, Lancet 2009). Reserve emergency MRI (with contrast if infection/cancer suspected) for suspected CES, cord compression, or spinal infection.
ESR/CRP when spinal infection is a consideration — sensitive though nonspecific; pair with MRI and blood cultures. A normal WBC and absence of fever do not exclude spinal infection; ESR is the most sensitive lab.
Know what each study can't exclude. A negative x-ray does not rule out fracture (CT is the test for bone), and a negative CT does not rule out cord compression or abscess (MRI is the test for soft tissue). A lumbar series delivers ~75 chest x-rays of radiation for little answer.
Image the whole spine when epidural abscess or cord compression is suspected — noncontiguous skip lesions are common, and a lumbar-only MRI can miss the lesion.
NSAIDs are first-line for nonspecific back pain; opioids add no meaningful relief and increase length of stay and return visits. Advise resuming normal activity — bed rest does not improve outcomes.
PVR / bladder scan for any CES concern — the cheap, decisive test.
Bedside ultrasound for AAA in the older patient with new back pain.

06What to document

▼ weak

"Back pain, neuro WNL. Ambulatory. Discharged with ibuprofen."

▲ defensible

"No saddle anesthesia, urinary retention, or bowel/bladder dysfunction; no fever, IV drug use, immunosuppression, cancer history, weight loss, or anticoagulation. Strength 5/5 and symmetric L2–S1, sensation intact including perineum, reflexes symmetric, normal gait, normal rectal tone; PVR 40 cc. Aorta non-tender, no pulsatile mass, symmetric distal pulses. Cauda equina, epidural abscess, malignancy, and AAA considered and felt unlikely. Return for fever, leg weakness, loss of bladder/bowel control, or abdominal pain."

07Where charts fail

Documenting the neuro exam as "WNL" instead of each component — there's no baseline to monitor against.
Attributing "couldn't urinate" to pain without measuring a post-void residual.
Assuming a drug-seeking patient has no real pathology — they still get epidural abscess and discitis.
Calling an older patient's back pain "muscular" without considering AAA or metastasis.
Missing the post-procedure or anticoagulated patient with a new deficit (epidural hematoma).
Calling pain "musculoskeletal" because it's reproducible or the back is non-tender — neither finding rules out serious pathology.
Charting "x-ray negative" or "CT negative" as if it excluded fracture or cord compression — each study rules out only what it can see.

08Sources

Molyneux K, Vaswani S. Emergency department management of patients with low back pain: a review of current evidence. Emergency Medicine Practice (EB Medicine). 2024;26(11).
Chou R, Qaseem A, Snow V, et al. Diagnosis and treatment of low back pain: joint clinical practice guideline, ACP/American Pain Society. Ann Intern Med. 2007;147(7):478-491.
Chou R, Fu R, Carrino JA, et al. Imaging strategies for low-back pain: systematic review and meta-analysis. Lancet. 2009;373(9662):463-472.
Todd NV. Cauda equina syndrome: the timing of surgery probably does influence outcome. Br J Neurosurg. 2005;19(4):301-306.
Tayal VS, Graf CD, Gibbs MA. Prospective study of accuracy and outcome of emergency ultrasound for AAA. Acad Emerg Med. 2003;10:867-871.
Sokoloff WC, Kusulas MP. Emergency department management of dangerous back pain in children. Pediatric Emergency Medicine Practice (EB Medicine). 2023;20(4).

Low back pain: documentation that holds up