Nothing is more challenging to diagnose than a case of low back pain. That is why it is so important to have an extensive list of causes in mind before approaching the patient. Anatomy forms the basis for developing such a list (Table 45).
Moving posteriorly from the skin inward, one encounters the muscle and fascial planes, the lumbosacral spine and its ligaments, the spinal cord and cauda equina, the abdominal aorta and its branches, the rectum, and prostate in the male, the uterus and pelvic organs in the female, and finally the bladder.
TABLE 45. Low Back Pain |
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The skin may be involved by a pilonidal cyst, contusions and lacerations, or herpes zoster. The muscle and fascia are involved by fibromyositis, trichinosis, contusions, lacerations, strains, sprains, and herniation of fat through the subfascial plain. (The latter has been espoused as a common cause of lumbago.) A more important cause of muscle spasms and irritation is faulty posture. Slumping over a typewriter or computer, wearing the wrong shoes (e.g., very high heels), or having one leg shorter than the other may cause this.
The next layer is the lumbosacral spine. Vascular lesions are infrequent here, but inflammation caused by osteomyelitis and tuberculosis (Pott disease) is still seen in some countries. More common lesions of the spine inducing low back pain are metastatic carcinoma, herniated discs, rheumatoid spondylitis, or lumbar spondylosis (often erroneously labeled osteoarthritis). Osteoarthritis and other arthridites may involve the facets of the zygapophyseal joints, and produce back pain (“facet syndrome”). Advanced osteoarthritis leads to spinal stenosis, especially in elderly persons. Multiple myeloma is not an uncommon cause and should be looked for in each case. Fractures are particularly frequent in association with this disease. Fractures are also seen with osteoporosis, osteitis fibrosa cystica, and osteomalacia. Paget disease, gout, and sprung back (in which the interspinous ligament is torn) are less common causes of low back pain originating in the spine. Congenital anomalies such as spondylolisthesis and scoliosis are important causes. In the spinal cord arteriovenous anomalies, myelitis, epidural abscesses, and primary tumors are important causes.
Moving deeper one encounters the aorta, and arteriosclerotic and dissecting aneurysms come to mind. Disease of the rectum may refer pain to the low back, particularly hemorrhoids, fissures, perirectal abscesses, and carcinomas. In the prostate, prostatitis and prostate carcinoma are frequent causes. Prostate carcinoma, however, produces low back pain most frequently by metastasis. The bladder and urethra are infrequent causes of low back pain, but a urinalysis and culture may be necessary to rule out infections.
To diagnose low back pain in women, the uterus and other pelvic organs must be examined. Dysmenorrhea (functional) is often the cause, but tubo-ovarian abscess, ovarian cysts, endometriosis, fibroids, retroversion or flexion of the uterus, and uterine carcinomas must be looked for.
Approach to the Diagnosis
Our first priority in a patient who presents with low back pain is to rule out anything serious such as a herniated disc or cauda equina tumor. A pelvic and rectal examination must be performed to exclude a pelvic tumor or prostate carcinoma. A careful neurologic examination must be done. If one is too busy to do that, referral to an orthopedic surgeon or neurologist is indicated. The neurologic examination should include an SLR test, femoral stretch test, careful sensory examination, and an assessment for asymmetric reflexes. It is wise to carefully measure the thighs and calves to reveal muscular atrophy. Any findings to support a diagnosis of radiculopathy are a reasonable indication for a CT scan or MRI of the lumbar spine. However, it may be wise to have a neurologist or neurosurgeon examine the patient first because these tests are expensive.
If the patient has normal neurologic, pelvic, and rectal examinations, it is perfectly legitimate to manage the patient conservatively for a while without any testing other than clinical. Close follow-up is important in these cases, however. Should the pain persist despite rest and conservative treatment, a more thorough diagnostic workup is indicated regardless of the lack of objective findings. This will include plain films or CT scan and an arthritis panel.
Low back pain |
Other Useful Tests
1. CBC
2. Urinalysis (pyelonephritis)
3. Urine for Bence–Jones protein (multiple myeloma)
4. Protein electrophoresis (multiple myeloma)
5. Chemistry panel (metastatic carcinoma)
6. Prostate-specific antigen (PSA) (prostatic carcinoma)
7. Urine culture and colony count (pyelonephritis)
8. Intravenous pyelogram (IVP) (renal calculus, carcinoma)
9. Aortogram (abdominal aneurysm)
10. Nerve blocks (radiculopathy)
11. Lidocaine infiltration of trigger points
12. Bone scan (rheumatoid spondylitis)
13. Human leukocyte antigen (HLA)-B27 antigen (rheumatoid spondylitis)
14. EMG and NCV (radiculopathy)
15. Myelogram (herniated disc, neoplasm)
16. Plain films of the lumbar spine
17. Sedimentation rate (polymyalgia rheumatica)
18. Bone densiometry (osteoporosis)
Case Presentation #63
A 34-year-old oil refinery worker complained of increasing low back pain radiating into both lower extremities. He denies paresthesias or increase of the pain on coughing or sneezing, but the pain is relieved by lying down. The pain is aggravated by lifting, bending, and stooping. His grandfather had similar back pain beginning in his thirties.
Question #1. Utilizing anatomy, what is your differential diagnosis at this point?
Neurologic examination revealed good sensation, power, and symmetrical reflexes in the lower extremities. The SLR and femoral stretch tests were negative bilaterally. Rectal examination was normal. X-rays of the lumbar spine revealed calcification of the intervertebral discs and degenerative changes.
Question #2. What is your diagnosis now?
Low back pain |