Presented by Bao Dang, MD
A 34-yo-female with PMH of DM and symptomatic L5-S1 disc herniation, presents to the ED with a chief complaint of fever and back pain. Pt states she was involved in a MVC 7 months prior that left her with a L5-S1 disc herniation with L foot drop and tingling and numbness on dorsum of L foot. Pt states she received a “back steroid injection” from a pain specialist 7 days ago. Since the injection, the pain has not subsided but instead she is experiencing worsening pain. The back pain is described as being midline of lower back. Pain is 8/10, constant even when pt is lying still, which is different from pt’s prior back pain. Pt has trouble sleeping over last few days because of pain. Pt also notes she’s been febrile with a max temperature of 102.1 taken at home. Pt has no c/o of urinary or fecal incontinence, N/V, HA, neck stiffness, photophobia, weight loss, dysurea, BM changes, weightloss, history of cancer.
Social Hx: No tobaco, Occasional Drinker, No Illicit drug use
Vitals:BP134/75, HR105, RR19, T38.9.
Generally the pt appeared uncomfortable lying in her stretcher. Pt was unable to ambulate from triage to Module.
Cardiovascular: S1 S2, no murmur, rubs or gallops
Neuro exam: Strength is 5/5 proximal and distally and FROM in bilateral upper extremities and right lower extremity. Left lower extremity showed decreased strength of dorsiflexion of L ankle, other wise strength is normal. Normal finger to nose examination. Decreased pin prick and light touch sensation was also noted over dorsum of left foot relative to right foot. Left leg raise produces sharp pain radiating down to lower leg. Palpation of lower back revealed slight tenderness of midline of lower back.
Abdominal examination: soft, nondistended, no tenderness, BS present.
Rectal: good rectal tone, guaiac negative, intact touch sensation perianally.
Lab Results: CBC:WBC(16),Hgb(13),Hct(34), Platelets(155), ESR:50(high), UA: Negative for UTI and hematuria
1. Considering the above presentation, what is the most likely diagnosis?
b. Primary or Secondary Carcinoma
c. Renal Colic
d. Spinal Epidural Abcess
e. Vertebral fracture
2. What is the diagnostic test of choice for this patient in the ED?
a. CT scan
b. Emergent MRI
c. Lumbar Puncture
e. X-ray spine
3. Which organism is the most likely cause of the above diagnosis?
b. Gram-negative bacilli
d. Staphylococcus aureus
e. The diagnosis is not due to an infection
1. d. Spinal Epidural Abcess (SEA)
The history and physical examination along with laboratory studies make the diagnosis of SEA more likely in this patient. The pt’s back pain changed from getting better with lying still to unrelenting and nocturnal pain after an epidural steroid injection, suggests a source for an infectious process. Unrelenting pain is one of the hallmark characteristic of spinal infection. The elevated ESR, WBC, and temperature all further points to an infectious process.
Most spinal infections include osteomyelitis and SEA. The above pt can have either type of infection. The way to distinguish the two types of infections would be to perform imaging of the area. Because of local extension of infections can occur, osteomyelitis can lead to SEA and vice versa.
Spinal epidural abscess is an infection of the space between the dura and vertebral body. In this pt’s case, the infection is most likely due to direct introduction of bacteria to the epidural space. Most spinal infections are due to hematogenous spread of bacteria from distant foci, however. Sources of seeding can range from endocarditis, infected indwelling catheters, urinary tract infections, and abdominal infections. A meta-analysis done on 915 pts with SEA by Reihsaus, et al found that skin abscesses and furuncle accounts for the most sources of seeding.
Back pain can certainly be a result of an expanding AAA or ruptured AAA. Pt with AAA issues are usually those of 55 years and older and there is a 2 times predilection for men. The ED physician must have a high suspicion and rule out this diagnosis in a pt belonging to the above demographic presenting with lower back pain and abdominal pain. Rupture AAA would most like be associated with not only abdominal/back pain but with hemodynamic instability as well.
Cancer around or involving the lumbar spine can cause back pain as well. It can also present with persistent fever and elevated ESR. The age of presentation, however, is usually in those younger than 20 or older than 50. There can also be a history of previous cancer and unexplained weight loss.
Renal colic can cause back pain. Renal colic pain usually has an acute onset with the pain waxing and waning in intensity. The pain usually follows the distribution of the dermatones from T10 to S4. So the pain usually would start out around the back and migrate to the flank and finally into the groin. Renal colic is usually associated with nausea and vomiting and patients often is restless and moves about, unlike peritonitis where patients tend to find relief lying still.
Vertebral fracture is unlikely in this patient because her clinical picture looks more like an infection. Red flags for fractures include: history of recent trauma, age over 50, and history of osteoporosis.
2. b. Emergent MRI
For patients with back pain as a complaint, there are red flags that one should illicit from the history and physical exam because it will help guide the ED physician in determining whether further diagnostic testing is needed. These clues are used to rule out the possibility of fracture, infection, epidural compression, and cancer.
The red flags to look for in the history are:
- Age younger than 18
- Spondylolysis, spondylolisthesis, tumor
- Age older than 50
- Malignancy, AAA, fracture
- Trauma and chronic steroid use
- History of cancer
- Fever, chills, night sweats
- Infection, malignancy
- IVDA and immune-compromised state
- Nocturnal pain
- Malignancy, infection, ankylosing spondylitis
- Unrelenting pain
- Malignancy, infection
- Incontinence, saddle anesthesia, bilateral neurological deficits
- Epidural compression syndrome
- Unilateral neurologic deficit
- Herniated disc
The red flags to be elicited from the physical exam are:
- Infection, malignancy
- Anal sphincter laxity, saddle anesthesia
- Epidural compression syndrome
- Absent or diminished reflex
- Epidural compression syndrome, herniated disc
- Positive straight leg raise (SLR) and cross SLR exam
- Herniated disc
- Bone tenderness
- Fracture, infection
It is worth it to note the proper way to perform the SLR test. While the pt is in the supine position, place one hand above the knee and the other cupping the heel and slowly raise the straight limb. Pain should be elicited before there is any movement of the pelvis and the sharp shooting pain should extend below the knee. The same maneuvers is used for the cross SLR but on the opposite limb. The SLR test is more sensitive, while the cross SLR is more specific for a herniated disc.
For this particular patient, the red flags include: pain becoming unrelenting and nocturnal, fever, history of recent epidural injection. One should obtain a CBC, erythrocyte sedimentation rate (ESR), UA with culture and sensitivity, and blood culture X2. The ESR is a very sensitive test for spinal infection however it is not specific. It is elevated in cancer, rheumatologic diseases, as well as infections in other body areas. CBC does not have the sensitivity as the ESR, WBC can be normal in many cases of significant spinal infection.
For imaging, because of a high suspicion on infection in this patient, an emergent MRI is the best test. MRI will be able to define clearly the spinal cord, canal, and disc anatomy. MRI has the added advantage of using non-ionizing radiation which suits best for pregnant women. MRI, however, has its limitations. Availability, time, costs, contra-indications, and claustrophobia can all play a factor. As an alternative, a CT scan with myelography is just as effective as an MRI. CT however, does expose the patient to radiation and myelography is an invasive procedure that has its own inherent risk. Lumbar puncture is a relative contraindication in patients with cellulitis or possible abscess over the area the procedure would be performed. This procedure exposes the patient to increased risk of introducing the organism into the cerebral spinal fluid causing meningitis.
There is no indication for ultrasound in suspected spinal infection. Plain X-ray of spine should only performed when there is a suspicion of fracture from the history and physical. Late infection can sometimes be seen on the plain x-ray as discitis but usually early infection will not be radiographically apparent. Plain films in elderly patients can also be useful to diagnose multiple myeloma and other metastatic cancers.
3. d. Staphylococcus aureus
In a patient with suspected spinal infection, an attempt should be made to identify the causative organism. Urine and two sets of blood culture should be drawn before antibiotics are given. It is recommended for ED physician to discuss antibiotics administration with consultant services before giving the first dose. Some consultants may prefer to surgically obtain culture of tissue or pus from infective sites. Antibiotic administration before sample is obtained may yield false negative results, thus prolonging empiric antibiotic treatment. However, in the case of delayed ability to obtain radiological studies or tissue samples it may be necessary to start broad spectrum antibiotics after cultures are drawn.
The organism found to be the culprit in most SEA is Staphylococcus aureus. However, all of the listed organisms have been shown to cause SEA. In IVDU, the empiric therapy should cover MRSA. The use of vancomycin should be included in the initial treatment. If there is no suspicion of MRSA, then nafcillin and oxacillin can be used against S. aureus. Empiric antibiotics should also be aimed at Streptococci, gram-negative bacilli, and anaerobic as well. A good regiment to start out in the ED is vancomycin (or nafcillin and oxacillin if no MRSA suspected), metronidazole, and ceftriaxone (or ceftazidime or cefotaxime).
- Patients with low back pain and no red flags in the history and physical usually require no further workup as 90 percent of these patients will improve with conservative treatments in 4-6 weeks.
- In pts with a history of IVDU and back pain an infectious cause of their back pain should be considered (osteomyelitis, epidural abscess, or endocarditis) until proven otherwise.
- An effort should be made to discuss antibiotic administration in the ED with consultants first. However, the ED physician should use his/her clinical judgement in deciding whether the patient is stable enough to wait for treatment.
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This case discussion presented by Dr Bao Dang