Medical Imaging for Drug Abuse

Whether it’s drug addiction, drug abuse or even drug withdrawal, related medical problems are often behind a patient’s visit to a hospital emergency department (ED). And medical imaging frequently plays a major role in determining a differential diagnosis for these patients. Because radiologic technologists are an essential part of the health care team, they should be familiar with signs and symptoms, as well as radiological complications, of drug abuse.

Drug dependence, or addiction, is compulsive use of a substance despite the negative consequences, while drug abuse is the excessive use of a drug or use of a drug for purposes for which it was not medically intended. Drug abuse can lead to drug dependence or addiction.

Drug intoxication and drug overdose may be accidental or intentional. Drug withdrawal symptoms can occur when use of a substance is stopped or reduced, and symptoms vary depending on the abused substance. The onset of withdrawal symptoms depends on the length of time the drug normally stays within the body. Drug intoxication, overdose and withdrawal can be life-threatening in some situations.

In the ED, toxicology screens done on blood and urine specimens can reveal the presence of many chemicals and drugs in the body. Blood tests are more likely to detect the presence of an abused substance than urine tests, but urine drug screens are done more frequently.

Drug toxicity also has many radiologic indications. Effects are varied, but are primarily manifested in the brain and lungs. These include, but are not limited to: diffuse alveolar damage, non-specific interstitial pneumonia, obliterative bronchiolitis, pulmonary hemorrhage, edema, subarachnoid hemorrhage and stroke.

The lungs
According to Howard B. Kessler, MD, chair of the department of radiology at Holy Redeemer Hospital and Medical Center in Philadelphia, the chest radiograph is the most frequent radiologic study in the evaluation of drug overdose. The usual presentation is on an acute basis for individuals presenting to the ED with altered mental status ranging from restlessness and anxiety to deep coma. In many instances, Dr. Kessler said, the chest X-ray is normal. Occasionally the ingested/injected agent can produce pulmonary edema and this has a very typical appearance on X-ray.

Pulmonary drug toxicity is increasingly being diagnosed as a cause of acute and chronic lung disease. As far back as 1974, chronic users of heroin were found to have distinctive changes in their lungs, which were directly contributed to heroin. These lesions, previously called “narcotic lung,” are marked on chest X-ray by patchy pulmonary congestion, focal atelectasis and emphysema. The anatomic evidence that heroin produces striking and sometimes fatal changes in the lungs seems well established.

The primary pleural complication of illicit drug use is pneumothorax, or collapsed lung. Several large studies of cocaine users have documented repeated occurrences of acute respiratory symptoms. Upper respiratory and pulmonary complications are attributed to intravenous cocaine addicts, freebasers and crack smokers. Cocaine is very toxic, and frequent snorting results in non-specific manifestations, including shortness of breath, cough and wheezing, especially in combination with smoking marijuana. Crack is a potent form of cocaine that results in rapid and striking stimulant effects when smoked. Adverse reactions that are unique to crack are lung infiltrates and bronchospasm.

The incidence of abnormal chest radiographs in cocaine users admitted with pulmonary complaints has ranged from 12-55 percent. In a 1989 study of the value of chest radiography in relationship to chest pain and shortness of breath related to crack cocaine smoking on 71 patients, nine had abnormal findings on radiographs that included atelectasis, pneumothorax and pulmonary edema. Radiographic detection of these abnormalities was important in the clinical management of these patients.

Studies more than a decade ago concluded that marijuana smoke can injure the lungs, and habitual smoking has been linked to chronic respiratory tract symptoms and destruction of cells in the immune defense system of the lungs. In addition, the available evidence strongly suggests that regularly smoking marijuana may predispose to the development of cancer of the respiratory tract. Marijuana can produce injury to the lungs in subtle ways, according to Dr. Kessler, and the usual finding is a normal chest X-ray. However, for individuals with underlying lung disease such as asthma, the presence of marijuana can exacerbate the asthmatic condition and present with hyperinflation of the lungs. Idiosyncratic re-sponses to inhalants such as marijuana also can present with non-specific increased lung markings and, infrequently, pulmonary congestion.

The manifestations of pulmonary drug toxicity are extremely variable, Dr. Kessler said. They range from increased interstitial markings to pulmonary congestion to ARDS and pulmonary edema. The lung is both resistant to injury and sensitive to allergens or toxic compounds. Radiologists have long been aware of the range of pulmonary complications related to drug abuse.

The brain
Non-invasive imaging in humans and X-ray images of radioisotope tracers in animals have been used to better understand the mechanism of how drugs influence brain functions. As a rule, radiologists should be familiar with the radiologic manifestations of the effects of cocaine abuse, including the drug’s pathophysiology and complications.

Alberto M. Righi, board certified neuroradiologist at Charlotte Regional Medical Center in Punta Gorda, Fla., reported that computed tomography (CT) of the brain is ordered for patients presenting to the ED with altered mental status resulting from cocaine overdose. In 2002, a cerebral CT scan of an 18-year-old male with a history of illicit drug abuse and severe occipital headache revealed subarachnoid hemorrhage, which was corroborated with cerebral angiography.

Cocaine dependence is associated with vascular events, and is a common cause of clinically apparent stroke in young individuals, even in the absence of other risk factors. Pathological changes in the nervous system have been associated with chronic abuse of illicit drugs, and magnetic resonance (MR) imaging findings have shown increased incidence of demyelination in white matter in the brains of these patients. Region-specific abnormalities in the brains of cocaine-dependent patients have been found on T2-weighted MR imaging scans, and blood flow in the brain is substantially reduced in cocaine users. Ischemic stroke is detected in approximately 25-60 percent of patients who abuse cocaine. MR imaging is superior to CT for detecting small ischemic changes.

Cerebral blood flow in chronic cocaine users has been studied with positron emission tomography (PET), which shows patchy regions of decreased blood flow through the brain, Dr. Righi said. PET scans help in studying the patterns of brain metabolism related to long-term use of illicit drugs; deficits have been noted in the visual-association cortex area of the brain. Single photon emission computed tomography (SPECT) also has been used to detect cerebral abnormalities in these patients, demonstrating focal defects ranging in severity. SPECT imaging is considered to be one of medicine’s most sophisticated functional brain imaging studies.

“Brain imaging work has clearly taught us how harmful drug abuse is to brain function,” wrote Lisa C. Routh, MD, in her book, Healing Anxiety and Depression. “Cocaine, methamphetamines, alcohol, marijuana, nicotine and caffeine decrease brain activity over time, sometimes significantly.”

Rene Jackson is a special procedures nurse in the medical imaging department of Charlotte Regional Medical Center in Punta Gorda, Fla., and a freelance health care writer. The references for this article are available online by visiting www.advanceweb.com and following the links to the Web page for ADVANCE for Imaging and Radiation Therapy Professionals.

Drug Abuse Statistics
In 2002, an estimated 19.5 million Americans, or 8.3 percent of the population aged 12 or older, were current illicit drug users.

Marijuana is the most commonly used illicit drug, with a rate of 6.2 percent.

In 2002, an estimated 2 million people were current cocaine users, 567,000 of whom use crack.

Hallucinogens were used by 1.2 million people, including 676,000 users of Ecstasy. There were 166,000 current heroin users.

Among youths aged 12-17, 11.6 percent were current illicit drug users.

In 2002, an estimated 11 million people reported driving under the influence of an illicit drug.

Adapted from U.S. Dept. of Health and Human Services 2002 National Survey on Drug Use and Health

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