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<< Sickle Cell Disease And Other Hemoglobinopathies: Approaches To Emergency Diagnosis And Treatment

Differential Diagnosis

Patients who present with complication of SCD may have more problems than meet the eye. An underlying precipitant such as infection may lead to a painful crisis, or another pathological condition may mimic a painful crisis. For instance, sickle cell patients are at increased risk of osteomyelitis, most often caused by Salmonella species and S.aureus.24 Patients with chest pain or cough may have pneumonia, ACS, or pulmonary embolism. The patient with abdominal pain may simply be suffering from a vaso-occlusive crisis or may harbor dangerous surgical pathology.

Painful Crisis, Bone Infarction, Or Osteomyelitis?

In all of these conditions, physical exam may reveal pain and tenderness over the affected area. Patients with a painful crisis generally have a normal body temperature and minimal to no soft-tissue swelling. In both bone infarction and osteomyelitis, patients may have fever and soft-tissue swelling. In general, the temperature in osteomyelitis is usually higher than in infarction.25 While patients with either bone infarction or osteomyelitis may demonstrate elevated WBC counts and elevated sedimentation rates,25,26 infarction is statistically about 50 times more common than infection.27 Consider osteomyelitis when the patient has a high or persistent fever, leukocytosis over baseline, or unusual sites of pain.6

Imaging Approaches

The emergency physician has limited tools to distinguish bone infarction from osteomyelitis. Early in the course of illness, plain radiographs usually are not helpful in the patient with a painful extremity. This is because the destructive changes of osteomyelitis do not appear until 10-14 days after symptom onset.25 MRI and CT have limited usefulness as well, as these studies are only positive when an abscess can be identified.25

The results of nuclear imaging can be confusing, as a hot or cold spot on a bone scan may be due to either osteomyelitis or infarction. One useful approach is to combine bone marrow scanning (99mTe-sulfur colloid) and 99mTc-MDP bone scan. An acute infarct will always show decreased marrow uptake. A normal marrow scan adjacent to a suspicious bone lesion is likely due to infection.25,28 Most emergency physicians do not order bone or marrow scans on ED patients, leaving such decisions to the consultant.

The only definitive diagnostic test for osteomyelitis is a positive culture from blood or bone marrow aspirate. When in doubt, assume osteomyelitis until proven otherwise.

Joint Pain: Osteonecrosis, Painful Crisis, Or Septic Arthritis?

Osteonecrosis is a painful and often disabling complication of repeated bony infarctions. By age 35, half of all sickle cell patients have evidence of hip and shoulder osteonecrosis.6 Patients complain of pain and/or limited range of motion of the affected joint. In the early stages of disease, radiographs will often appear normal,29 although MRI may be diagnostic.6

The most important entity to rule out in a sickle cell patient with joint pain is septic arthritis. Suspect septic arthritis when joint pain is accompanied by fever, significant pain on range of motion, or erythema/edema involving the joint. Joint aspiration is the most vital (and the only definitive test) in such cases.

Abdominal Pain: Vaso-occlusive Crisis Or Intra-abdominal Pathology?

Abdominal pain in a patient with SCD can occur with a vaso-occlusive crisis, but a host of more serious intraabdominal problems can mimic this condition. (See Table 1.) One study retrospectively examined findings in 53 patients with SCA who presented with abdominal pain.30 A vaso-occlusive crisis was responsible for the pain in 57%, while 23% had a surgical entity and 20% had a nonsurgical genitourinary disorder. Overall, 77% of the patients with painful sickle crisesóbut no patient with an acute surgical processócomplained of coexistent abdominal and remote (usually extremity) pain. In this series, all patients with a surgical condition complained of localized rather than diffuse pain. Of note, laboratory parameters, including the leukocyte count, did not distinguish sickle crisis from a surgical condition.30

Biliary tract and parenchymal liver disease are the most prevalent and serious complications that affect the digestive system.6 Five hepatobiliary syndromes that are especially common include viral hepatitis, hepatic crisis, cirrhosis, cholelithiasis with or without cholecystitis, and intrahepatic cholestasis.31 Of these, the most concerning diagnosis is intrahepatic cholestasis. It is characterized by sudden onset of severe right upper quadrant pain, progressive hepatomegaly, coagulopathy, and extreme hyperbilirubinemia.28,31 Treatment is supportive, with transfusion and correction of coagulopathy. The mortality is very high.28,32,33

Cholelithiasis is frequent in sickle cell patients. Pigmented gallstones are the natural consequence of accelerated bilirubin turnover.34 Gallstones, which may develop before 4 years of age,35,36 occur in up to one-third of patients 2-18 years old37 and in over 50% of the adults with SCD. Patients with gallstones tend to have biliary colic,37,38 but true cholecystitis is rare.6,36

An enlarging liver, decreasing hemoglobin levels, and mildly elevated liver enzymes characterize acute hepatic sequestration (also known as hepatic crisis).1 Treatment is supportive. Infectious hepatitis B or C can be contracted via transfusions, while cirrhosis may develop from either scarring or hemosiderosis.

There is more to the belly than the right upper quadrant, and patients with SCD may have other acute conditions that masquerade as a painful crisis. Even lead toxicity may be the culprit.39 As an interesting aside, it appears that acute appendicitis is very unusual in patients with SCD. A recent review suggests that the likelihood of developing appendicitis in SCD patients is less than one-third of that for the population at large.40 The authors suggest that surgical exploration "be limited to those with clear evidence of potential surgical pathology or progressive findings."40

Acute Chest Syndrome, Pneumonia, Or Pulmonary Embolism?

It is not possible to distinguish between infectious and non-infectious causes of ACS in the ED. For this reason, it is prudent to treat such patients with antibiotics while awaiting culture results.

The issue of pulmonary embolism is more of a "sticky wicket." Distinction between pulmonary thrombosis and embolism is difficult on clinical grounds, and V/Q scans rarely aid clinical evaluation because most sickle cell patients have chronic pulmonary abnormalities.6,41

Pulmonary angiography is problematic during an acute crisis due to its tendency to induce sickling,42 but it may be necessary if the diagnosis is in doubt. While CT angiography is being used more frequently in an attempt to diagnose pulmonary emboli, there are few published studies of its use in patients with ACS.43

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Last Modified: 07/23/2017
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