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Sex & Gender in Acute Care Medicine

Sex & Gender in Acute Care Medicine. Chapter 12: Gender and Diagnostic Imaging. Christopher L. Moore. Case. A 28-year-old woman who is otherwise healthy and taking no medications presents to the Emergency Department with right-sided chest pain

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Sex & Gender in Acute Care Medicine

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  1. Sex & Gender in Acute Care Medicine Chapter 12: Imaging

  2. Chapter 12: Gender and Diagnostic Imaging Christopher L. Moore

  3. Case • A 28-year-old woman who is otherwise healthy and taking no medications presents to the Emergency Department with right-sided chest pain • The pain is worse when she moves or takes a deep breath • The pain started this morning and is sharp • She feels it is making her short of breath

  4. Case, continued • Review of systems otherwise negative • On exam, her rate is 74, blood pressure 125/70, respiratory rate 12, O2 saturation 100% on room air • Clear breath sounds bilaterally and some reproducible tenderness over the right rib cage • No lower extremity pain or swelling

  5. Case, continued • Urine hCG is negative for pregnancy • EKG shows normal sinus rhythm • The resident caring for the patient is concerned about pulmonary embolism and suggests that a d-dimer be obtained to determine whether the CT pulmonary angiogram should be obtained

  6. Introduction • Diagnostic imaging is an integral part of evaluation of the Emergency Department (ED) patient • Numerous imaging modalities are now routinely available in the ED setting: • Plain radiography (X-ray) • Ultrasound • Computed tomography (CT) • Often MRI and nuclear studies

  7. Introduction • Overall, nearly half (46.6% in 2008) of ED visits in the US involve an imaging study • Plain X-rays are the most common imaging test obtain in the ED setting • CT is the second most common • Challenges are to determine what (if any) imaging is appropriate and what the value of imaging is in a given situation

  8. Introduction • Women account for more than half of all ED visits and sex should have a role in determining appropriate imaging • Much attention has been focused on advanced medical imaging (CT, MRI, and nuclear studies), which now results in nearly $100 billion in annual expenditures in the US • This growth may be justifiable if advanced imaging improves patient outcomes

  9. Introduction • However, imaging does not always change rates of diagnosis, intervention, or hospitalization • It adds time to the ED visit, which may contribute to ED crowding • Imaging may also lead to incidental findings, which are occasionally helpful but much more commonly lead to further imaging, anxiety, and unnecessary intervention

  10. Introduction • CT is second only to X-ray in frequency of use in the ED • Yet it is more expensive and exposes patients to substantially more ionizing radiation • It is estimated that radiation from medical sources – primarily CT – has doubled the average yearly radiation dose received by individuals in the US over the past several decades

  11. Introduction • CT use in the US peaked in 2011 • CT use has declined about 5% per year since then • Some of this may be due to efforts to curb overutilization • As well as broader understanding of the risks of radiation from CT scans • However, this still represents nearly one CT performed per year for every 4 US residents • A rate nearly twice that of Canada

  12. Introduction • An estimated 20% to 40% of CT scans may be “medically unnecessary” • Women face a greater risk of malignancy from CT scanning • In addition to radiation risks, contrast-induced nephropathy and anaphylactoid reactions to contrast media are also more prevalent in women

  13. Introduction • Prevalence and type of disease will vary by sex as will diagnostic yield and risk from radiation • Cost, time, and radiation should not be an impediment to an appropriate imaging study • However, sex differences can help guide the appropriate use of diagnostic imaging

  14. “Appropriate” Imaging • Diagnostic imaging saves lives every day • What constitutes “appropriate” imaging, however, is elusive and depends on the imaging procedures, the patient, and the setting • Appropriateness criteria have been published by organizations such as the American College of Radiology and the American Society of Echocardiography

  15. “Appropriate” Imaging • While there are some differences in suggested appropriate imaging based on patient characteristics, in general the guidelines do not factor in patient sex • Despite increased imaging, it is debatable whether patient-centered outcomes have improved

  16. “Appropriate” Imaging • A study of ED visits for abdominal pain found in increase in CT use from 10.1% of visits in 2001 to 22.5% of visits in 2005 • No difference was found in detection of surgical disease and no decrease in hospital admissions • Understanding the role of patient sex may help clinicians make more informed decisions about appropriate imaging

  17. Risks of Radiation from CT • A 2004 study suggested that physicians largely misunderstood and misestimated the risk of radiation from CT • Quantifying the risk has remained difficult because of debates about the evidence as well as confusion about units of measurement • Ionizing radiation is the type used by CT scans, plain radiographs (X-rays), and nuclear studies

  18. Measuring Radiation from CT • Generally acknowledged that there is a small increased risk of cancer when ionizing radiation is applied to radiosensitive organs • The magnitude of this risk for an individual and a population is incompletely understood • May be quite variable based on age, size, and sex • Remains controversial

  19. Measuring Radiation from CT • The best way to get a working understanding of how radiation is measured to is to look at the metrics displayed with each scan • Most modern CT scanners include an image at the end of a CT series that includes to measures: • CT dose index (CTDI or CDTIvol, in mGy) • Dose-length-product (CLP, in mGy-cm)

  20. Measuring Radiation from CT • The CTDIvol can be considered the output of the scanner • DLP is related more to overall absorbed radiation and is equal to the CTDIvol x the length of the body scanned • While DLP is the more frequently reported dose metric, it is important to understand that DLP is calculated based on a simulated patient

  21. Measuring Radiation from CT • DLP does not take patient size into account in terms of actual effective organ dose • For a given CTDIvol or DLP, a larger patient will have relatively lower actual dose delivered to radiosensitive organs due to absorption by non-radiosensitive tissue • Regarding actual radiation dose delivered to a patient, several metrics are in use

  22. Measuring Radiation from CT • Ongoing controversy about the best reporting methods can make comparison and estimation of risk confusing • Both rad and gray refer to the amount of radiation absorbed • Rem and sievert refer to the effective organ dose that should be most directly related to risk of malignancy

  23. Measuring Radiation from CT • For CT, the most commonly used units will be milligray (mGy) and millisieverts(mSv) • Converting to effective dose can be estimated based on the body part is being scanned • For example, the conversion factor for a CT abdomen and pelvis is ~15-17 microsieverts per milligray-centimenters • So a CT scan with a DLP of 622mGy-cm would be estimated to deliver an effective dose of approximately 10.6 mSv

  24. Measuring Radiation from CT • To put this in perspective, the average yearly background radiation in the US approximately 2-3 mSv • ~6 mSv per year including medical radiation • A 2009 paper estimated that there could be as many as 29,000 future malignancies resulting from CT performed in the US in 2007 alone

  25. Risk of Radiation from CT • Population-based risks of malignancy from CT depend on age, sex, and type of scan • Estimates range from approx. 1 in 150 for a 20-year-old female undergoing a CT angiogram to about 1 in 15,000 for a 60-year-old man undergoing a routine head CT • These estimates of risk were derived by extrapolating the rates of malignancy in survivors of the atomic bomb attacks on Japan during World War II

  26. Risk of Radiation from CT • The current generally accepted model is called the “no threshold linear model” • Each increased radiation dose is directly related to increased risk of malignancy; there no single threshold amount that becomes more dangerous • However, the number of people in these cohorts developing cancer after receiving smaller doses of radiation is small • A recent study has called this model into question

  27. Dose Variability from CT • Given the potential harms of ionizing radiation, radiological societies have endorsed the use of a dose that is “as low as reasonably achievable” (ALARA) • While this is good in theory, in practice dosing may vary considerably for similar protocols between centers • The American College of Radiology founded the Dose Imaging Registry (DIR) in 2011

  28. Risk of Radiation from CT • However, there is no actual requirement to lower dosing for a given protocol • These protocols are typically set by manufacturers but may be modified by radiologists and CT technicians • A recent report form the DIR found that dosing for CTs looking for kidney stones could vary by a factor of 10, with less than 2% done using the low-dose protocols (<3 mSv)

  29. Sex Considerations: Chest Pain • Chest pain is the most common presenting ED chief complaint in adult males • The second leading complaint in adult females • It is estimated that 40% of all medical radiation is related to cardiovascular imaging and intervention • Almost all chest pain evaluated in the ED will receive a plain chest X-ray

  30. Imaging in Chest Pain • While the utility of this as a routine test has been questioned for more than 30 years, it is inexpensive and without much radiation • It typically functions as a screen for pneumonia, heart failure, pneumothorax, and aortic pathology • Whether imaging beyond chest X-ray is obtained depends on the suspicion for serious pathology

  31. Imaging in Chest Pain • Echocardiography offers an attractive modality with no ionizing radiation that can be helpful in evaluation of the ED patient with chest pain and/or dyspnea • While access to formal echocardiography is often restricted in the ED setting, point-of-care ultrasound of the heart and lungs involves no radiation and is easily performed at the bedside

  32. Imaging in Chest Pain • Bedside echocardiography can exclude pericardial effusion, provide information about left ventricular function, right ventricular strain, and aortic root size • Accuracy for these conditions will vary based on the experience of clinician performing it

  33. Imaging in Chest Pain • Definitive diagnosis in coronary disease, PE, or thoracic aortic dissection (TAD) is typically obtained using modalities with ionizing radiation • For PE and TAD, the test of choice is contrast-enhanced CT of the chest • For coronary disease, cardiac catheterization with coronary angiography is the reference standard

  34. Imaging in Chest Pain • However, in both PE and ACS evidence-based approaches allow effective exclusion of disease in many patients without using ionizing radiation • Data suggest that testing occurs more than is warranted by the evidence • When ionizing radiation of the chest is overused, women are disproportionately at risk due to the exposure of breast tissue to potentially carcinogenic radiation

  35. Chest Pain Concerning for CAD • Heart disease is the leading cause of death in the US for both men and women • Efforts to minimize missed diagnoses have led to extensive diagnostic testing • The majority of chest pain seen in the ED can be considered “low-risk chest pain,” with a normal or nonspecific EKG and negative cardiac biomarkers

  36. Chest Pain Concerning for CAD • About 2-4% of people presenting with low-risk chest pain will ultimately be found to have significant coronary disease • If the history is concerning, it is often standard care in the US to evaluate the coronary arteries with a CT angiogram or stress test • Nuclear stress tests account for about 20% of the medical radiation received by the population

  37. Chest Pain Concerning for CAD • While nuclear stress tests are an effective tool for risk stratification, other options such as exercise echocardiography may be as effective and do not involve radiation • A recent survey of practitioners using nuclear stress tests found that only 7% were using a stress-first approach (i.e., only moving to a nuclear study if stress EKG or stress echo were inconclusive)

  38. Chest Pain Concerning for CAD • Increasingly, coronary CT angiogram (CCTA) is an option for detecting coronary disease • However, the radiation involved is higher than that of a typical CT abdomen and pelvis and includes irradiation of the breasts in female patients • Our recommendation is that in younger, lower risk patients, stress EKG, stress echo, or CT/nuclear strategies be considered first

  39. Chest Pain Concerning for PE • Pulmonary embolism (PE) is estimated to occur in 600,000 patients annually in the US • CT pulmonary angiogram is now considered the diagnostic gold standard • Since its introduction, the diagnosis of PE has nearly doubled in the US • However, with increased diagnosis, mortality from PE has only been minimally affected

  40. Chest Pain Concerning for PE • Complications from anticoagulation have risen, suggesting that we are treatment more and potentially less clinically significant PEs • Several clinical decision rules can stratify patients with symptoms of PE below the testing threshold for CT • The Wells score indicates whether patients have a low enough pretest probability that if a d-dimer is negative, further imaging is not needed

  41. Chest Pain Concerning for CAD • Women are more likely to have a positive d-dimer, which is more likely to be falsely elevated • This may contribute to the higher rate of imaging even if decision rules are followed • However, it is estimated that as many as 1/3 of CTPAs (in both sexes) could be avoided by using evidence-based rules

  42. Imaging in Abdominal Pain • Abdominal pain is the leading reason that adult females visit the ED • A substantial number of patients with abdominal pain will not have a definitive diagnosis established during their ED visit • Like chest pain, evaluation of abdominal pain in the ED setting has seen a marked rise in advanced medical imaging

  43. Imaging in Abdominal Pain • Despite the rise in CT imaging, there has been no change in the diagnosis of appendicitis, diverticulitis, or gallbladder disease • Admission rates for patients with abdominal pain have not changed • This suggests that utilization of CT may not be adding value to patient-centered outcomes

  44. Imaging in Abdominal Pain • Ultrasound is a safe and effective alternative to CT for most common diagnosable causes of abdominal pain • The benefit:risk ratio may be higher for women • Biliary disease represents a disorder that is more common in women and is most effectively diagnosed with ultrasound

  45. Imaging in Abdominal Pain • Biliary disease accounts for as many as 9% of admissions for abdominal pain • Ultrasound is the initial test of choice if biliary disease is suspected • May be performed at the bedside by experienced practitioners

  46. Imaging in Abdominal Pain • While appendicitis occurs more commonly in males, the diagnosis may be more challenging in women due to other etiologies of right lower quadrant pain • CT is often considered the test of choice and is highly accurate • Ultrasound is typically the first-line approach for pediatric and pregnant patients

  47. Imaging in Abdominal Pain • A recent analysis of an ultrasound-first approach for appendicitis estimated that such an approach could avoid ~180 excess cancer deaths per year • As well as substantial cost savings • Such an approach would again be most effective in younger female patients

  48. Imaging in Abdominal Pain • The elderly with abdominal pain represent a special population as they are more likely to harbor a serious diagnosis, particular a vascular etiology • Abdominal aortic aneurysm (AAA) causes about 15,000 deaths annually in the US with twice as many deaths occurring in men • While AAA is more common in men, women face increased risk of rupture at smaller sizes

  49. Imaging in Abdominal Pain • Ultrasound screening for AAA is currently recommended by the USPSTF for asymptomatic men between age 65 and 75 who have never smoked • Routine screening is not recommended for women • Identification of AAA may be accomplished at the bedside in the ED • A non-diagnostic ultrasound should generally be followed by a CT

  50. Imaging in Abdominal Pain • Sex-specific causes of lower abdominal pain must also be considered • In men with lower abdominal pain, a testicular etiology should be considered and a testicular exam should be performed • If there are concerning findings on exam, scrotal ultrasound is typically the test of choice

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