Mullin, Daniel K. MD
Learning Objectives: After reading this article, the physician should be able to:
1. List a broad differential for low back pain and know how to rule in or rule out certain diagnoses based on a thorough history and physical examination.
2. Describe the indications for ordering radiographic studies for patients complaining of low back pain.
3. Discuss the differential diagnosis for returning travelers complaining of fever or diarrhea and understand the clinical significance of each disease.
Low Back Pain Deyo RA, Weinstein JN N Engl J Med 2001;344:363
More than two-thirds of adults will suffer at lease one episode of low back pain during their lifetimes. It affects men and women equally, with onset most often between the ages of 30 and 50. In the United States, it is one of the leading reasons given for seeking medical attention, is a major contributor to our nation's total health care expenditure, and is the leading cause of work-related disability.
What makes the complaint of low back pain so frustrating for physicians is that an estimated 85 percent of patients with isolated low back pain cannot be given a precise pathoanatomical diagnosis. What makes low back pain so frustrating for patients is that primary care and emergency physicians appear perplexed in the face of it. Discouraged patients seek guidance from surgeons and pain specialists or seek alternative treatments such as spinal manipulation and acupuncture when time is often all that is needed. Indeed, recovery is generally inevitable regardless of what is done. One study demonstrated that 90 percent of patients recover within two weeks of presentation. (Brit Med J 1994;308:577.)
A broad differential should be maintained when seeing a patient with low back pain, and the physician should consider three distinct categories of pathology: mechanical, nonmechanical, and visceral disease. Mechanical causes of low back pain include lumbar strain or sprain (idiopathic), degenerative processes of discs and facets, herniated discs, spinal stenosis, osteoporotic compression fractures, traumatic fractures, and spondylolisthesis (defined as anterior displacement of a vertebra on the one beneath it). Nonmechanical causes include neoplastic diseases, Paget's disease of the bone, inflammatory arthritis (often associated with HLA-B27), and infections such as shingles, osteomyelitis, epidural abscess, and septic discitis. The visceral diseases presenting as low back pain include aortic aneurysm, pancreatitis, perforated ulcer, nephrolithiasis, pyelonephritis, perinephric abscess, retroperitoneal hematoma, and prostatitis.
When encountering a patient with low back pain, Deyo and Weinstein propose that three questions be asked: Is a systemic disease causing the pain? Is there a social or psychological distress that may amplify or prolong the pain? Is there a neurological compromise that may require surgical evaluation? For most patients, these questions can be answered from a thorough history and physical examination. Imaging is rarely needed.
Neurologic involvement is usually suggested by the presence of sciatica or pseudoclaudication (leg pain with walking). The leg pain of sciatica is often associated with numbness or paresthesia in a dermatomal distribution, and is usually caused by disc herniation impinging on a specific nerve root. The straight-leg-raise test and crossed straight-leg-raise test should be performed on patients with low back pain. A positive straight-leg-raise test is a reproduction of the symptoms of sciatica with pain radiating below the knee (not just back or hamstring pain) after elevation of a straight leg to 60 degrees. The crossed straight-leg-raise test is reproduction of the same symptoms when the contralateral leg is elevated to 60 degrees. The straight-leg-raise test is sensitive but not specific and the crossed straight-leg-raise test is specific but not sensitive for herniated disc. The natural history of herniated discs is favorable; improvement is the norm. Sequential MRI studies revealed that the herniated portion of the disc actually regresses with time, with partial or complete resolution in two-thirds of cases after six months. Because of this, a patient with a suspected herniated disc should be treated nonsurgically for at least one month. If severe pain or neurologic deficits persist, MRI and surgical consideration are appropriate.
Cauda equina syndrome is a commonly feared but rare condition usually caused by a tumor or massive midline disk herniation that compresses the cauda equina nerve roots. Patients with this syndrome typically complain of low back pain, urinary retention with overflow incontinence, saddle (perineal) anesthesia, and bilateral lower extremity motor and/or sensory abnormalities. The exam classically shows muscle weakness with decreased reflexes, decreased sensation in the perineal region, and poor anal sphincter tone. Plain radiography is unlikely to be helpful, and MRI is superior to CT scan in assisting with the diagnosis. This is one case where an early neurosurgical consult is of utmost importance.
Deyo and Weinstein cite the AHCPR clinical practice guidelines they helped develop (AHCPR publication no. 95–0642) in recommending plain x-rays for patients with fever, unexplained weight loss, a history of cancer, neurologic deficits, alcohol or injection drug abuse, age over 50, trauma, or failure of pain to improve after four to six weeks with conservative treatment. CT and MRI are much more sensitive than plain x-rays, but early or frequent use of these tests is discouraged because disc and other abnormalities are common among asymptomatic adults. CT and MRI should be reserved for patients for whom there is a strong clinical suspicion of underlying infection, cancer, or persistent neurologic deficit. MRI is more sensitive for infection and metastatic cancer.
Treatment for nonspecific low back pain, Deyo and Weinstein recommend, is nonsteroidal anti-inflammatory drugs prescribed on a regular schedule rather than on an as-needed basis. For most patients, the best recommendation is a rapid return to normal activities without overdoing exercise or lifting. Bed rest does not increase the speed of recovery from acute low back pain and may inhibit healing, and should not be recommended. For patients with chronic low back pain, aerobic exercise with strengthening exercises of the back and legs appear to be beneficial.
Comment: As emergency physicians, we must maintain a high clinical suspicion for the dangerous causes of low back pain, but also must realize that most patients we see will have run-of-the-mill low back pain that doesn't need an extensive workup or referral to multiple specialists. Reassure patients about a likely favorable prognosis, advise them to stay active, discourage bed rest, and prescribe pain medications as deemed necessary (NSAIDs, acetaminophen, and/or opioids).
There are several evidence-based, well-written guidelines on low back pain. The one that most U.S. physicians should be aware of, even though it was written in 1994, is the Agency for Health Care Policy and Research's “Acute Low Back Problems in Adults: Clinical Practice Guideline No. 14.” (AHCPR publication no. 95–0642.) A recent article (J Gen Intern Med 2005;20:1132) unfortunately demonstrated that the majority of physicians do not follow these guidelines. In this study, a questionnaire asked physicians for diagnostic and treatment recommendations regarding two case scenarios: a patient with low back pain without sciatica and one with sciatica. Neither case presented any “red flags.” Only 26.9 percent of physicians fully complied with the guideline when the patient had nonspecific low back pain, and a paltry 4.3 percent complied with the guideline in the case of the patient with sciatica. Statistics such as these explain in part a yearly health care expenditure attributable to back pain in the United States that is approaching $26.3 billion. (Spine 2004;29:79.)
Illness after International Travel Ryan ET, et al N Engl J Med 2002;347:505
An estimated 50 million people travel from the industrialized world to the developing world each year. One percent to five percent of travelers become ill enough to seek medical attention either during or after travel, and one in 100,000 dies. The most common travel-associated complaints include fever, diarrhea, and rash. It is of utmost importance to assess travel history, likely incubation period, exposure history, associated signs and symptoms, duration of illness, immunization status, and use of chemoprophylaxis.
Approximately three percent of international travelers report fever, the presence of which requires prompt evaluation. Malaria, transmitted by infected mosquitos, is the most important cause of fever among patients who have recently traveled. It is caused by P. falciparum (the most rapidly fatal), P. vivax, P. ovale, and P. malariae. Ninety percent of P. falciparum infections are acquired in Sub-Saharan Africa, and 90 percent of infected travelers have symptoms within one month of their return. This course is different from other plasmodium species, which can present with symptoms more than a year after infection. Because resistance to antimalarial drugs is widespread, chemoprophylaxis does not guarantee protection against malaria.
Fever, the most common complaint, may be associated with headache, cough, and gastrointestinal problems. Fevers occurring at regular intervals of 48 to 72 hours are virtually pathognomonic of malaria. The diagnosis is usually made via light microscopy of a Giemsa-stained thick and/or thin blood smear. Because of the cyclical nature of the parasitemia, negative blood films should be repeated at least once within 12 to 24 hours after the first evaluation. Antimalarial drugs should be administered parenterally if there is evidence of septic shock, renal failure, altered mental status, respiratory distress, seizures, severe anemia, or if the level of P. falciparum in the blood exceeds four percent of visible erythrocytes.
Dengue is another major infectious disease threat in tropical and subtropical areas worldwide, also spread by the bite of the infected mosquito. It manifests as an influenza-like illness with fever, headache, and myalgias. Leukopenia and thrombocytopenia are characteristic findings. The most serious forms of infection, dengue hemorrhagic fever and dengue shock syndrome, are rare among travelers because these usually occur in those previously infected with a different serotype. There is no definitive treatment, and therapy is aimed at supportive measures such as intravenous fluids and antipyretics.
Other infections that cause fever include rickettsial infections such as scrub typhus (O. tsutsugamushi) from the bite of an infected mite. These infections cause fever, headache, myalgias, painless eschar at the inoculation site, and regional lymphadenopathy. Leptospirosis also manifests as fever, myalgias, headache, and rash, and is transmitted via percutaneous or permucosal contact with animal urine or contaminated water or soil. A history of recent exposure to fresh water and symptoms suggests the diagnosis of acute leptospirosis. Fever with associated peripheral eosinophilia in a traveler should prompt consideration of a helminthic infection. These include acute hookworm (A. duodenale or N. americanus), ascariasis, strongyloides, schistosomiasis, toxocariasis, lymphatic filariasis, and acute trichinosis.
Traveler's diarrhea is very common and usually resolves during or shortly after travel, often in response to antimicrobial and antimotility agents. Invasive or inflammatory enteropathy (dysentery) should be suspected in patients with bloody diarrhea, fever, and/or fecal leukocytes. The most commonly identified cause of acute traveler's diarrhea is bacterial and includes Campylobacter jejuni (associated with Guillain Barré syndrome), salmonella, shigella, and E. coli. Treatment is usually empiric with either a quinolone or macrolide, except when enterohemorrhagic E. coli (O157:H7) is suspected because of a possible increased risk of hemolytic-uremic syndrome. Amebic dysentery, which is caused by E. histolytica, usually presents insidiously and may be complicated by hepatic abscess formation. Finally, in cases of prolonged traveler's diarrhea with malabsorption, protozoal infection should be considered, most specifically G. lamblia, which is found worldwide and is especially prevalent in areas with poor sanitation and insufficient water treatment facilities. When giardiasis is suspected, metronidazole is the first-line treatment and is very effective.
About the LLSA
As part of its continuous certification program, the American Board of Emergency Medicine has developed the Lifelong Learning and Self-Assessment (LLSA) program to promote continuous education of diplomates. Each year, beginning in 2004, 16 to 20 articles are chosen based on the Emergency Medicine Model. A list of these articles can be found on the ABEM web site, www.abem.org.
After reading the articles, ABEM diplomates are required to take a web-based examination of 32 to 40 multiple-choice questions. Each test remains online for three years, based on the date of publication. (The deadline for the 2004 articles, for instance, is March 31, 2007). Once registered for an LLSA test, diplomates may access the test as often as needed with no time limit. A passing score is achieved by answering 90 percent of the items correctly. Each physician has three opportunities to pass.
Diplomates are required to take and pass a specific number of LLSA tests to take the Continuous Certification (ConCert) examination. This number depends on what year the ConCert exam will be taken. (Physicians whose certificates expire after 2012 are required to complete eight LLSA tests to be eligible to take the ConCert examination.) Up to 40 percent of the ConCert exam will be based on content from the preceding nine LLSA reading lists.
ABEM is not authorized to confer CME credit for the successful completion of the LLSA test, but it has no objection to physicians participating in such activities. EMN's CME activity, Learning to Live with the LLSA, is not affiliated with ABEM's LLSA program, and reading this article and completing the quiz does not count toward ABEM certification. Rather, participants may earn 1 CME credit from the Lippincott Continuing Medical Education Institute, Inc., for each completed EMN quiz.
CME Participation Instructions
To earn CME credit, you must read the article in Emergency Medicine News, and complete the quiz, answering at least 80 percent of the questions correctly. Mail the completed quiz with your check for $10 payable to the Lippincott Continuing Medical Education Institute, Inc., 770 Township Line Road, Suite 300, Yardley, PA 19067. Only the first entry will be considered for credit, and must be received by Lippincott Continuing Medical Education Institute, Inc., by November 30, 2007. Acknowledgement will be sent to you within six to eight weeks of participation.
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Lippincott Continuing Medical Education Institute, Inc., designates this educational activity for a maximum of 1 AMA PRA Category 1 Credit.™ Physicians should only claim credit commensurate with the extent of their participation in the activities.
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