Urgent message: Back pain in a pediatric patient requires a high index of suspicion. Ominous causes (e.g. cancer, infection), are far more common in the pediatric population. Conversely, mechanical low back pain is far less common, and is a diagnosis of exclusion.
Forrest Nguyen, DO
Introduction
As urgent care physicians, we are responsible for anything that comes through the door. Often, the diagnosis proves to be routine – a viral infection, a sore throat, or cough.
Other times, however, we discharge the patient wondering if we made the right diagnosis. In-house labs, CT scans and/or MRIs are a luxury not all centers enjoy. For those that do not, the history and physical exam become ever more important and are the foundation of correct diagnosis.
Case Study
A 12-year-old female presented with a one-week history of back pain described as gradual onset, sharp, and 10 out of 10 on the pain scale. She indicated a location in the lower back between the L4and L5. The pain did not radiate, was worse with movement, and was alleviated with ibuprofen.
The patient stated that the pain began right after getting her tetanus shot. She denies any recent history of trauma or injuries, but admits to falling off a trampoline two years age and hurting her ankle. Plain film of the ankle at the time was negative.
She also denies any headaches, acute visual changes, dyspnea, chest pain, recent infection, or acute neurological changes, as well as any urinary/bowel incontinence or saddle anesthesia.
Upon further questioning, the patient admitted to bilateral lower quadrant abdominal pain and bladder pressure. She stated she had minimal urination (“just dripping”) over the previous four days. Her last void was the night before. She denies any dysuria, vaginal discharge, or incontinence.
The patient reported that her last menstrual period was two months ago, but denies any sexual activity. She is awake, alert, and in no acute distress. Out findings are detailed in Table 1.
The patient was admitted into the hospital, where the following labs were drawn:
WBC – 12.0 Na – 140
Hgb – 12.7 K – 3.9
Hct – 36.9 Cl – 102
Plt – 252 Co2 – 28
Neut – 80.5 BUN – 9
Bands – 0 Creat – 0.41
Lymph – 12.6 Glucose – 107
Mono – 5.8 Alk Phos – 111
Eosin – 0.8 ALT – 12
Baso – 0.3 AST – 11
UA (clean catch) – unable to obtain
Foley Catheter – 240 ml
UA – negative
Urine drug screen – negative
Urine pregnancy – negative
Sedimentation rate – 94 mm/hr
CRP – 5.4
CT ABD with contrast
- No CT evidence for acute intra-abdominal process
- Approximately 11 mm low attenuation lesion in the midpole left kidney, likely representing a cyst
CT pelvis with contrast
- Bilateral ovarian follicles with a small amount of free fluid in the cul-de-sac
- Foley catheter and gas within bladder lumen
Over-read by pediatric radiologist: Findings are very suspicious for probable discitis at L5-S1 with possible osteomyelitis involving S1. MRI of the L-S spine is recommended
Table 1. Findings in Urgent Care |
|
| BP: 114/70 P: 80 T: 98.5 (tympanic) Wt: 138 lbs (62.2 kg) LMP: 2 months ago |
Abdomen: BS x 4, soft b/l lower quadrant tenderness, non-distended, no masses, no bruits, no hepatomegaly, no guarding, no rebound |
| HEENT, NCAT, PERRLA, EOMI, TMs clear bilaterally | Back: No deformity, no costovertebral angle tenderness, point tenderness L4-L5 with no radiculopathy |
| Nares patent | Extremities: No clubbing, cyanosis, or edema, 2+ dorsalis pulses bilaterally |
| Oropharynx pink and moist without erythema or exudate | Neurological: Cn 2-12 grossly intact, MS 5/5 extremity, absent patellar reflexes b/l |
| Tonsils not enlarged | Achilles reflex intact, negative Babinski |
| Neck: Supple, no lymphadenopathy, full range of motion, no deformity | Pt with antalgic gait |
| Lungs: Clear to auscultation bilaterally | Proprioception intact, sensation to sharp and dull stimuli intact, b/l quadricep “clonus,” negative Romberg, Mini mental exam nml |
| Heart: Regular, S1/S2 no rubs, murmurs, or gallops | Skin: No lesions, rashes, or deformities |
MRI results
Findings suspicious for osteomyelitis involving superior T12 body and at least S1. Prevertebral and epidural phlegmon from superior L5 to S1.
Discussion
Back pain is a rare complaint in the pediatric population. Approximately half of the episodes of back pain in all age groups are caused by musculoskeletal trauma. The remainder is from infection, idiopathic pain, sickle cell pain crisis, or miscellaneous causes.
In the ambulatory care setting, overloaded school backpacks (defined for our purposes as weighting > 15% to 20% of the child’s weight) are a common cause of back pain in children.
The following are red flags that the physician should consider in evaluating every pediatric patient with back pain:
- young age (particularly < 4 years)
- fever
- weight loss
- severe or constant pain
- nocturnal pain
- progression over the course of time
- history of acute or repetitive trauma
- history of malignancy or tuberculosis exposure
- evidence of neurologic dysfunction (bowel or bladder dysfunction or abnormal reflexes)
- interference with activity
Discitis
Discitis usually presents with the gradual onset of irritability and back pain. The patient will sometimes refuse to walk. The disease is usually without systemic toxicity and is only occasionally accompanied by fever.
In some patients, abdominal pain may be the only complaint.
The lower lumbar discs are affected most commonly, but any disc (occasionally more than one) may be involved.
Neurologic findings (e.g., decreased muscle strength or reflexes) may be present; blood cultures, typically, are sterile.
White blood cell count usually is normal, and the erythrocyte sedimentation rate is elevated in most patients.
The etiology of discitis is controversial. For our patient, the cause was never found.
Sixty percent of biopsied discs grow bacteria, usually Staphylococcus aureus.
Differential diagnosis should include consideration of the following:
- Spondylolysis is a unilateral or bilateral defect (separation) in the vertebral pars interarticularis, usually in the lower lumbar vertebrae, particularly L5. Spondylolisthesis occurs when bilateral defects permit anterior slippage of the vertebral body. These may be congenital, but more typically are acquired as the bone “fatigues” from recurrent microtrauma during excessive lumbar hyperextension, a common problem in gymnasts, dancers, divers, weightlifters, and football linemen.
- Degenerative disc disease. Herniation of the nucleus pulposus is less common in children than in adults. Some risk factors include acute trauma and Scheunemann kyphosis.
- Osteoid osteoma, the most common neoplasm that presents with back pain in children. This is a benign bone tumor characterized by nocturnal pain and prompt relief with NSAIDs.
Treatment
Children often recover from discitis without antibiotic therapy, and many cases probably go undiagnosed. The current consensus is that discitis in children is a low-grade infection. Host defense systems usually are capable of overcoming the infection without assistance because the disc is richly vascularized up to 7 years of age. Occasionally, host defenses are overwhelmed, and compilations such as abscess formation may result.
Treatment for discitis is not standardized. Aspiration of the affected disc for culture usually is not performed. Empiric antibiotic therapy should be directed against S aureus. Limited retrospective data suggest that initial treatment with IV antibiotics followed by oral antibiotics is associated with more rapid response and fewer relapses than is treatment with oral antibiotics or analgesia alone.