Principles of Diagnostic Imaging




INTRODUCTION



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Diagnostic imaging plays a significant role in the management of many patients with toxicologic emergencies. Radiography can confirm a diagnosis (eg, by visualizing the xenobiotic), assist in therapeutic interventions such as monitoring gastrointestinal (GI) decontamination, and detect complications of the xenobiotic exposure (Table 8–1).219




TABLE 8–1Xenobiotics with Diagnostic Imaging Findings



Conventional radiography is readily available in the emergency department (ED) and is the imaging modality most frequently used in acute patient management. Other imaging modalities are used in certain toxicologic emergencies, including computed tomography (CT); enteric and intravascular contrast studies; ultrasonography; transesophageal echocardiography (TEE); magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA); and nuclear scintigraphy, including positron emission tomography (PET) and single-photon emission tomography (SPECT).




VISUALIZING THE XENOBIOTIC



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A number of xenobiotics are radiopaque and can potentially be detected by conventional radiography. Radiography is most useful when a substance that is known to be radiopaque is ingested or injected. When the identity of the xenobiotic is unknown, the usefulness of radiography is very limited. When ingested, a radiopaque xenobiotic is often seen on an abdominal radiograph as described in detail in this chapter. Injected radiopaque xenobiotics are also visualized by radiography. If the toxic material itself is available for examination, it can be radiographed outside of the body to detect its radiopacity or any radiopaque contents (Fig. 102–2).92




RADIOPACITY



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The radiopacity of a xenobiotic is determined by several factors. First, the intrinsic radiopacity of a substance depends on its physical density (g/cm3) and the atomic numbers of its constituent atoms. Biologic tissues are composed mostly of carbon, hydrogen, and oxygen and have an average atomic number of approximately 6. Substances that are more radiopaque than soft tissues include bone, which contains calcium (atomic number 20), radiocontrast agents containing iodine (atomic number 53) and barium (atomic number 56), iron (atomic number 26), and lead (atomic number 82). Some xenobiotics have constituent atoms of high atomic number, such as chlorine (atomic number 17), potassium (atomic number 19), and sulfur (atomic number 16) that contribute to their radiopacity.



The thickness of an object also affects its radiopacity. Small particles of a moderately radiopaque xenobiotic are often not visible on a radiograph. Finally, the radiographic appearance of the surrounding area also affects the detectability of an object. A moderately radiopaque tablet is easily seen against a uniform background, but in a patient, overlying bone or bowel gas often obscures the tablet.




ULTRASONOGRAPHY



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Compared with conventional radiography, ultrasonography theoretically is a useful tool for detecting ingested xenobiotics because it depends on echogenicity rather than radiopacity for visualization.40 Solid pills within the fluid-filled stomach infrequently have an appearance similar to gallstones within the gallbladder. In one in vitro study using a water-bath model, virtually all intact pills could be visualized.8 The authors were also successful at detecting pills within the stomachs of human volunteers who ingested pills. Nonetheless, reliably finding pills scattered throughout the GI tract, which often contains air and feces that block the ultrasound beam, is a formidable task. In a well-controlled trial comparing participants who ingested 50 enteric-coated placebo tablets with control participants, ultrasonography of the stomach had a sensitivity of only 62.5% at the time of ingestion and 20.8% after 1 hour and a specificity of 58.3% and 79%, respectively.234 Ultrasonography, therefore, has limited clinical practicality and is therefore not routinely recommended.




INGESTION OF AN UNKNOWN XENOBIOTIC



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Although a clinical policy issued by the American College of Emergency Physicians in 1995 suggested that an abdominal radiograph should be obtained in unresponsive overdosed patients in an attempt to identify the involved xenobiotic, the role of abdominal radiography in screening a patient who has ingested an unknown xenobiotic is questionable.7 The number of potentially ingested xenobiotics that are radiopaque is limited. In addition, the radiographic appearance of an ingested xenobiotic is not sufficiently distinctive to determine its identity (Fig. 8–1).1,248,266 However, when ingestion of a radiopaque xenobiotic such as ferrous sulfate tablets or another metal with a high atomic number is suspected, abdominal radiographs are helpful.6 In addition, knowledge of potentially radiopaque xenobiotics is useful in suggesting diagnostic possibilities when a radiopaque xenobiotic is discovered on an abdominal radiograph that was obtained for reasons other than suspected xenobiotic ingestion, such as in a patient with abdominal pain (Fig. 8–2).214,225




FIGURE 8–1.


Ingestion of an unknown substance. A 46-year-old man presented to the emergency department with a depressed level of consciousness. Because he also complained of abdominal pain and mild diffuse abdominal tenderness, a computed tomography (CT) scan of the abdomen was obtained. The CT scan revealed innumerable tablet-shaped densities within the stomach (arrows). The CT finding was suspicious for an overdose of an unknown xenobiotic. Orogastric lavage was attempted, and the patient vomited a large amount of whole navy beans. Computed tomography is able to detect small, nearly isodense structures such as these that cannot be seen using conventional radiography. (Used with permission from Dr. Earl J. Reisdorff, MD, Michigan State University, Lansing, MI.)






FIGURE 8–2.


Detection of a radiopaque xenobiotic on an abdominal radiograph. An abdominal radiograph obtained on a patient with upper abdominal pain revealed radiopaque material throughout the intestinal tract (arrows). Further questioning of the patient revealed that he consumed bismuth subsalicylate (Pepto-Bismol) tablets to treat his peptic ulcer (bismuth; atomic number 83). The identification of radiopaque material does not allow determination of the nature of the substance.





Several investigators evaluated the radiopacity of various medications.61,70,97,103,114,173,211,228,238 These investigators used an in vitro water-bath model to simulate the radiopacity of abdominal soft tissues.211 The studies found that only a small number of medications exhibit some degree of radiopacity. A short list of the more consistently radiopaque xenobiotics is summarized in the mnemonic CHIPES—chloral hydrate, “heavy metals,” iron, phenothiazines, and enteric-coated and sustained-release preparations.



The CHIPES mnemonic has several limitations.211 It does not include all of the pills that are radiopaque in vitro such as acetazolamide and busulfan. Most radiopaque medications are only moderately radiopaque, and when ingested, they dissolve rapidly, becoming difficult or impossible to detect. “Psychotropic medications” include a wide variety of compounds of varying radiopacity.173,211 For example, whereas trifluoperazine (containing fluorine; atomic number 9) is radiopaque in vitro, chlorpromazine (containing chlorine; atomic number 17) is not.211 Sustained-release preparations and those with enteric coatings have variable composition and radiopacity. Pill formulations of fillers, binders, and coatings vary among manufacturers, and even a specific product can change depending on the date of manufacture. Furthermore, the insoluble matrix of some sustained-release preparations is radiopaque and when seen on a radiograph, these tablets once opened no longer contain active medication. Some sustained-release cardiac medications such as verapamil and nifedipine have inconsistent radiopacity.140,227,240 Finally, this was a very old study, and many pills currently on the market have never been tested.




EXPOSURE TO A KNOWN XENOBIOTIC



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When a xenobiotic that is known to be radiopaque is involved in an exposure, radiography plays an important role in patient care.6 Radiography can confirm the diagnosis of a radiopaque xenobiotic exposure, quantify the approximate amount of xenobiotic involved, and monitor its removal from the body. Examples include ferrous sulfate, sustained-release potassium chloride,123,232 and heavy metals.



Iron Tablet Ingestion



Adult-strength ferrous sulfate tablets are readily detected radiographically because they are highly radiopaque and disintegrate slowly when ingested. Aside from confirming an iron tablet ingestion and quantifying the amount ingested, radiographs repeated after whole-bowel irrigation help to determine whether further GI decontamination is needed (Fig. 8–3).60,74,118,123,172,178,181 Nonetheless, caution must be exercised in using radiography to exclude an iron ingestion. Some iron preparations are not radiographically detectable. Liquid, chewable, or encapsulated (Chap. 45) (“Spansule”) iron preparations rapidly fragment and disperse after ingestion. Even when intact, these preparations are less radiopaque than ferrous sulfate tablets.61




FIGURE 8–3.


Iron tablet overdose. (A) Identification of the large amount of radiopaque tablets confirms the diagnosis in a patient with a suspected iron overdose and permits rough quantification of the amount ingested. (B) After emesis and whole-bowel irrigation, a second radiograph revealed some remaining tablets and indicated the need for further intestinal decontamination. (Used with permission from the Fellowship in Medical Toxicology, NYU School of Medicine, New York City Poison Control Center.)






Metals



Metals, such as arsenic, cesium, lead, manganese, mercury, potassium, and thallium, are often detected radiographically. Examples of metal exposure include leaded ceramic glaze (Fig. 8–4),199 paint chips containing lead (Fig. 93–7),131,158 mercuric oxide and elemental mercury (Fig. 95–1),143 thallium salts (atomic number 81),53,159 and zinc (atomic number 30).28 Arsenic (Fig. 8–5) with a lower atomic number (atomic number 33) is also radiopaque.93,136,246




FIGURE 8–4.


An abdominal radiograph of a patient who intentionally ingested ceramic glaze containing 40% lead. (Used with permission from the Fellowship in Medical Toxicology, NYU School of Medicine, New York City Poison Control Center.)






FIGURE 8–5.


An abdominal radiograph in an elderly woman incidentally revealed radiopaque material in the pelvic region (arrowhead). This was residual from gluteal injection of antisyphilis therapy she had received 35 to 40 years earlier. The injections may have contained an arsenical. (Used with permission from Dr. Emil J. Balthazar, Department of Radiology, Bellevue Hospital Center.)





Mercury



Unintentional ingestion of elemental mercury used to occur when a glass thermometer or a long intestinal tube with a mercury-containing balloon broke. Liquid elemental mercury is injected subcutaneously or intravenously. Radiographic studies assist débridement by detecting mercury that remains after the initial excision. Elemental mercury that is injected intravenously produces a dramatic radiographic picture of pulmonary embolization (Fig. 8–6).32,47,148,169




FIGURE 8–6.


Elemental mercury exposures. (A) Unintentional rupture of a Cantor intestinal tube distributed mercury throughout the bowel. (B) The chest radiograph in a patient after intravenous injection of elemental mercury showing a metallic pulmonary embolism. The patient developed respiratory failure, pleural effusions, and uremia and died despite aggressive therapeutic interventions. (C) Subcutaneous injection of elemental mercury is readily detected radiographically. Because mercury is systemically absorbed from subcutaneous tissues, it must be removed by surgical excision. (D) A radiograph after surgical débridement reveals nearly complete removal of the mercury deposit. Surgical staples and a radiopaque drain are visible. (Image A used with permission from Dr. Richard Lefleur, Department of Radiology, Bellevue Hospital Center; image B used with permission from Dr. N. John Stewart, Department of Emergency Medicine, Palmetto Health, University of South Carolina School of Medicine; and images C and D used with permission from the Fellowship in Medical Toxicology, NYU School of Medicine, New York City Poison Control Center.)





Lead



Ingested lead is detected only by abdominal radiography, such as in a child with lead poisoning who has ingested paint chips (Fig. 93–7). Metallic lead (eg, a bullet) that is embedded in soft tissues is not usually systemically absorbed. However, when the bullet is in contact with an acidic environment such as synovial fluid or cerebrospinal fluid (CSF), there significant absorption often occurs. Over many years, mechanical and chemical action within the joint causes the bullet to fragment and gradually dissolve.52,54,62,231,236 Radiography confirms the source of lead poisoning by revealing metallic material in the joint or CSF (Fig. 8–7).




FIGURE 8–7.


A “lead arthrogram” discovered many years after a bullet wound to the shoulder. At the time of the initial injury, the bullet was embedded in the articular surface of the humeral head (arrow). The portion of the bullet that protruded into the joint space was surgically removed, leaving a portion of the bullet exposed to the synovial space. A second bullet was embedded in the muscles of the scapula. Eight years after the injury, the patient presented with weakness and anemia. Extensive lead deposition throughout the synovium is seen. The blood lead concentration was 91 mcg/dL. (Used with permission from the Fellowship in Medical Toxicology, NYU School of Medicine, New York City Poison Control Center.)





Xenobiotics in Containers



In some circumstances, ingested xenobiotics are seen even though they are of similar radiopacity to surrounding soft tissues. If a xenobiotic is ingested in a container, the container itself will be visible (Special Considerations: SC5).



Body Packers



“Body packers” are individuals who smuggle large quantities of illicit drugs across international borders in securely sealed packets.4,18,20,31,43,65,69,111,129,146,157,184,220,223,243 The uniformly shaped, oblong packets are seen on abdominal radiographs either because there is a thin layer of air or metallic foil within the container wall or because the packets are outlined by bowel gas (Fig. 8–8). In some cases, a “rosette” representing the knot at the end of the packet is seen. Intraabdominal calcifications (pancreatic calcifications and bladder stones) have occasionally been misinterpreted as drug-containing packets.244,261




FIGURE 8–8.


Three “body packers” showing the various appearances of drug packets. Drug smuggling is accomplished by packing the gastrointestinal tract with large numbers of manufactured, well-sealed containers. (A) Multiple oblong packages of uniform size and shape are seen throughout the bowel. (B) The packets are visible in this patient because they are surrounded by a thin layer of air within the wall of the packet. (C and D) Small bowel obstruction caused by drug packets in a man who developed abdominal pain and vomiting 1 day after arriving on a plane flight from Colombia. Computed tomography confirmed bowel obstruction, and the patient underwent laparotomy and removal of 15 packets through an enterotomy. (Images A and B used with permission from Dr. Emil J. Balthazar, Department of Radiology, Bellevue Hospital Center. Images C and D used with permission from the Fellowship in Medical Toxicology, New York University School of Medicine, New York City Poison Center.)





The sensitivity of abdominal radiography for such packets is high, in the range of 85% to 90%. The major role of radiography is as a rapid screening test to confirm the diagnosis in individuals suspected of smuggling drugs, such as persons being held by airport customs agents. However, because packets are occasionally not visualized and the rupture of even a single packet can be fatal, abdominal radiography should not be relied on to exclude the diagnosis of body packing.204 Ultrasonography is used to rapidly detect packets, although it also should not be relied on to exclude such a life-threatening ingestion.39,94,161 Computed tomography without oral contrast is more sensitive than radiography and ultrasonography (Figs. SC5-1 and SC5-2).15,16,27,33,69,147,185,218,220 After intestinal decontamination, an upper GI series with oral contrast or CT without enteric contrast usually reveals any remaining packets (Fig. SC5–1).96,107,152,174



Body Stuffers



A “body stuffer” is an individual who, in an attempt to avoid imminent arrest, hurriedly ingests contraband in insecure packaging.201 The risk of leakage from such haphazardly constructed containers is high. Unfortunately, radiographic studies cannot reliably confirm or exclude such ingestions.226



Occasionally, a radiograph will demonstrate the ingested container (Fig. 8–9). If the drug is in a glass or in a hard-plastic crack vial, the container is frequently seen.106 If the body stuffer swallows soft plastic bags containing the drug, the containers are not usually visible. However, in three reported cases, “baggies” were visualized by abdominal CT.44,57,99,101,125,186




FIGURE 8–9.


Two “body stuffers.” Radiography infrequently helps with the diagnosis. (A) An ingested glass crack vial is seen in the distal bowel (arrow). The patient had ingested his contraband several hours earlier at the time of a police raid. Only the tubular-shaped container, and not the xenobiotic, is visible radiographically. The patient did not develop signs of cocaine toxicity during 24 hours of observation. (B) Another patient in police custody was brought to the emergency department for allegedly ingesting his drugs. The patient repeatedly denied this. The radiographs revealed “nonsurgical” staples in his abdomen (arrows). When questioned again, the patient admitted that he had swallowed several plastic bags that were stapled closed. (Used with permission from the Fellowship in Medical Toxicology, NYU School of Medicine, New York City Poison Control Center.)





Halogenated Hydrocarbons



Some halogenated hydrocarbons are visualized radiographically.38,45 Radiopacity is proportionate to the number of chlorine atoms. Both carbon tetrachloride (CCl4) and chloroform (CHCl3) are radiopaque. Because these liquids are immiscible in water, a triple layer is seen within the stomach on an upright abdominal radiograph—an uppermost air bubble, a middle radiopaque chlorinated hydrocarbon layer, and a lower gastric fluid layer. However, these ingestions are rare, and the quantity ingested is usually too small to show this effect. Other halogenated hydrocarbons such as methylene iodide are highly radiopaque.259



Moth Repellants



Some types of moth repellants (mothballs) can be visualized by radiography. Whereas relatively common and nontoxic paradichlorobenzene moth repellants (containing chlorine; atomic number 17) are moderately radiopaque, more toxic naphthalene moth repellants are faintly radiopaque.233 If the patient is known to have ingested a moth repellant but the nature of the moth repellant is unknown, the difference in radiopacity helps determine the type. Radiographs of the moth repellant outside of the patient can distinguish these two types (Fig. 102–2).



Radiolucent Xenobiotics



A radiolucent xenobiotic is often visible because it is less radiopaque than surrounding soft tissues. Hydrocarbons such as gasoline are relatively radiolucent when embedded in soft tissues. The radiographic appearance resembles subcutaneous gas as seen in a necrotizing soft tissue infection (Fig. 8–10).176




FIGURE 8–10.


Subcutaneous injection of gasoline into the antecubital fossa. The radiolucent hydrocarbon mimics gas in the soft tissues that is seen with a necrotizing soft tissue infection such as necrotizing fasciitis or gas gangrene (arrows). (Used with permission from the Fellowship in Medical Toxicology, NYU School of Medicine, New York City Poison Control Center.)






EXTRAVASATION OF INTRAVENOUS CONTRAST MATERIAL



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Extravasation of intravenous (IV) radiographic contrast material is a common occurrence. In most cases, the volume extravasated is small, and there are no clinical sequelae.21,42,63,200 Rarely, a patient has an extravasation large enough to cause cutaneous necrosis and ulceration.



Recently, the incidence of sizable extravasations has increased because of the use of rapid-bolus automated power injectors for CT studies.251 Fortunately, nonionic low-osmolality contrast solutions are currently nearly always used for these studies. These solutions are far less toxic to soft tissues than older ionic high-osmolality contrast materials.



The treatment of contrast extravasation has not been studied in a large series of human participants and is therefore controversial. Various strategies are proposed. The affected extremity should be elevated to promote drainage. Although topical application of heat causes vasodilation and could theoretically promote absorption of extravasated contrast material, the intermittent application of ice packs is recommended to lower the incidence of ulceration. Rarely, an extremely large volume of liquid is injected into the soft tissues, which requires surgical decompression when there are signs of a compartment syndrome. A radiograph of the extremity will demonstrate the extent of extravasation (Fig. 8–11).42




FIGURE 8–11.


Extravasation of intravenous contrast into the soft tissues of the upper extremity that occurred during a computed tomography contrast bolus administered by a power injector. Despite the extensive extravasation, the patient was successfully managed with limb elevation and cool compresses. (Used with permission from Mark Bernstein, MD, Department of Radiology, New York University School of Medicine.)





Precautions should be taken to prevent extravasation. A recently placed, well-running IV catheter should be used. The distal portions of the extremities (hands, wrist, and feet) should not be used as IV sites for injecting contrast. Patients who are more vulnerable to complications and those whose veins are more fragile, such as infants, debilitated patients, and those with an impaired ability to communicate, must be closely monitored to prevent or determine if extravasation occurs.



Summary



Obtaining an abdominal radiograph in an attempt to identify pills or other xenobiotics in a patient with an unknown ingestion is unlikely to be helpful and is, in general, not warranted. Radiography is most useful when the suspected xenobiotic is known to be radiopaque, as is the case with iron tablets and heavy metals. Radiography will demonstrate xenobiotic within the patient’s abdomen; elsewhere in the patient’s body; or, if the material is available, outside of the patient.




VISUALIZING THE EFFECTS OF A XENOBIOTIC ON THE BODY



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The lungs, central nervous system (CNS), GI tract, and skeleton are the organ systems that are most amenable to diagnostic imaging. Disorders of the lungs and skeletal system are seen by plain radiography. For abdominal pathology, contrast studies and CT are more useful, although plain radiographs can diagnose intestinal obstruction, perforation, and radiopaque foreign bodies. Imaging of the CNS uses CT, MRI, and nuclear scintigraphy (PET and SPECT).95



Skeletal Changes Caused by Xenobiotics



A number of xenobiotics affect bone mineralization. Toxicologic effects on bone result in either increased or decreased density (Table 8–2). Some xenobiotics produce characteristic radiographic images, although exact diagnoses usually depend on correlation with the clinical scenario.11,171 Furthermore, alterations in skeletal structure develop gradually and are usually not visible unless the exposure continues for at least 2 weeks.




TABLE 8–2Xenobiotic Causes of Skeletal Abnormalities



Increase in Bone Density



Lead Poisoning


Skeletal radiography suggests the diagnosis of chronic lead poisoning in children even before the blood lead concentration is obtained. With lead poisoning, the metaphyseal regions of rapidly growing long bones develop transverse bands of increased density along the growth plate (Fig. 8–12).25,189,191,209 Characteristic locations are the distal femur and proximal tibia. Flaring of the distal metaphysis also occurs. Such lead lines are also seen in the vertebral bodies and iliac crest. Detected in approximately 80% of children with a mean lead concentration of 49 ± 17 mcg/dL, lead lines usually occur in children between the ages of 2 and 9 years.25 In most children, it takes several weeks for lead lines to appear, although in very young infants (2–4 months old), lead lines develop within days of exposure.265 After exposure ceases, lead lines diminish and eventually disappear in some children.




FIGURE 8–12.


(A) A radiograph of the knees of a child with lead poisoning. The metaphyseal regions of the distal femur and proximal tibia have developed transverse bands representing bone growth abnormalities caused by lead toxicity. The multiplicity of lines implies repeated exposures to lead. (B) The abdominal radiograph of the child shows many radiopaque flakes of ingested leaded paint chips. Lead poisoning also caused abnormally increased cortical mineralization of the vertebral bodies, which gives them a boxlike appearance. (Used with permission from Dr. Nancy Genieser, Department of Radiology, Bellevue Hospital Center.)





Lead lines are caused by the toxic effect of lead on bone growth and do not represent deposition of lead in bone. Lead impedes resorption of calcified cartilage in the zone of provisional calcification adjacent to the growth plate. This is termed chondrosclerosis.25,56 Other xenobiotics that cause metaphyseal bands are yellow phosphorus (Chap. 112), bismuth (Chap. 87), and vitamin D (Chap. 44).



Fluorosis


Fluoride poisoning causes a diffuse increase in bone mineralization. Endemic fluorosis occurs where drinking water contains very high concentrations of fluoride (≥2 or more parts per million), as an occupational exposure among aluminum workers handling cryolite (sodium–aluminum fluoride), or with excessive tea drinking. The skeletal changes associated with fluorosis are osteosclerosis (hyperostosis deformans), osteophytosis, and ligament calcification (Fig. 8–13). Fluorosis primarily affects the axial skeleton, especially the vertebral column and pelvis. Thickening of the vertebral column causes compression of the spinal cord and nerve roots. Without a history of fluoride exposure, the clinical and radiographic findings are mistaken for osteoblastic skeletal metastases. The diagnosis of fluorosis is confirmed by histologic examination of the bone and measurement of fluoride concentrations in the bone and urine (Figs. 81–1 and 81–2).26,120,253




FIGURE 8–13.


Skeletal fluorosis. A 28-year-old man developed progressive muscle and joint pain over 3 to 4 weeks particularly involving his hands with thickening of his fingers. The results of an evaluation for inflammatory rheumatologic disorders were negative. Radiographs of his hands showed exuberant periosteal new bone formation known as “periostitis deformans,” which is characteristic of skeletal fluorosis. Further questioning revealed that the patient had been “huffing” the propellant of “Dust Off”; 225 cans were found at his residence. The propellant is difluoroethane (Freon 152a). The hydrocarbon is dehalogenated in the liver, and chronic exposure results in fluoride toxicity. (Used with permission from Dr. Eric Lavonas, Rocky Mountain Poison and Drug Center, Denver Health and Hospital Authority, Denver, CO, and Dr. Shawn M. Varney, Department of Emergency Medicine, San Antonio Military Medical Center, TX.)





Bisphosphonates


Bisphosphonates such as alendronate are commonly used to treat osteoporosis. They increase bone density by inhibiting osteoclast activity and decreasing bone resorption. However, by suppressing bone turnover and fracture healing, bisphosphonates are associated with accumulated microdamage to bone and skeletal weakening, which makes the bone vulnerable to fractures. Radiographically, there is thickening of the cortex of diaphyseal bone, typically the proximal femoral shaft. Such bone is associated with atypical proximal femoral shaft and subtrochanteric fractures after low-energy injuries such as a fall from standing. The fractures are transverse and have a characteristic “beaked” appearance caused by the cortical thickening (Fig. 8–14).89,137,215-217,260




FIGURE 8–14.


Bisphosphonate- (alendronate-) associated proximal femoral shaft fracture. A 61-year-old woman tripped on the sidewalk, falling on to her right side. She had been taking alendronate for 3 years for osteoporosis. There are diffuse cortical thickening of the femoral shaft and a transverse fracture in the subtrochanteric region with “beaking” of the fractured cortex on the medial side of the fracture. (Used with permission from the Fellowship in Medical Toxicology, NYU School of Medicine, New York City Poison Control Center.)





Focal Loss of Bone Density



Skeletal disorders associated with focal diminished bone density (or mixed rarefaction and sclerosis) include osteonecrosis, osteomyelitis, and osteolysis. Osteonecrosis, also known as avascular necrosis, most often affects the femoral head, humeral head, and proximal tibia.149 There are many causes of osteonecrosis. Xenobiotic causes include long-term corticosteroid use and alcoholism. Radiographically, focal skeletal lucencies and sclerosis are seen, ultimately with loss of bone volume and collapse (Fig. 8–15A).




FIGURE 8–15.


Focal loss of bone density and collapse: (A) Avascular necrosis causing collapse of the femoral head in a patient with long-standing steroid-dependent asthma (arrow). (B and C) Vertebral osteomyelitis in an injection drug user who presented with posterior thoracic pain for 2 weeks and then lower extremity weakness. As seen on computed tomography (CT), the infection begins in the intervertebral disk and then spreads to the adjacent vertebral bodies. Magnetic resonance image shows extension into the spinal canal causing spinal cord compression. (D) An injection drug user with thoracic back pain, leg weakness, and low-grade fever. Radiographic and CT findings of the spine were negative. Magnetic resonance image showing an epidural abscess (arrow) compressing the spinal cord. The cerebrospinal fluid in the compressed thecal sac is bright on this T2-weighted image. (Reproduced with permission from Schwartz DT, Reisdorff EJ: Emergency Radiology. New York, NY: McGraw-Hill; 2000.)





Acroosteolysis


Acroosteolysis is bone resorption of the distal phalanges and is associated with occupational exposure to vinyl chloride monomer. Protective measures have reduced its incidence since it was first described in the early 1960s.192



Osteomyelitis


Osteomyelitis is a serious complication of injection drug use. It usually affects the axial skeleton, especially the vertebral bodies, as well as the sternomanubrial and sternoclavicular joints (Figs. 8–15B and C).90,95 Back pain or neck pain in injection drug users warrants careful consideration. Spinal epidural abscesses causing spinal cord compression accompany vertebral osteomyelitis. Radiographic findings are negative early in the disease course before skeletal changes are visible, and the diagnosis is confirmed by MRI or CT (Fig. 8–15D).



Soft Tissue Changes



Certain abnormalities in soft tissues, that occur predominantly as a consequence of infectious complications of injection drug use, are amenable to radiographic diagnosis.90,95,116,239 In an injection drug user who presents with signs of local soft tissue infections, radiography is indicated to detect a retained metallic foreign body, such as a needle fragment, or subcutaneous gas, as is recognized in a necrotizing soft tissue infection such as necrotizing fasciitis. Computed tomography is more sensitive at detecting soft tissue gas than is conventional radiography. Computed tomography and ultrasonography also detect subcutaneous or deeper abscesses that require surgical or percutaneous drainage.



Pulmonary and Other Thoracic Problems



Many xenobiotics that affect intrathoracic organs produce pathologic changes that will be detected on chest radiographs.10,30,58,76,105,144,165,195,203,230,262,263 The lungs are most often affected, resulting in dyspnea or cough, but the pleura, hila, heart, and great vessels are also involved. Patients with chest pain need to be evaluated for pneumothorax, pneumomediastinum, or aortic dissection. Patients with fever, with or without respiratory symptoms, can have focal infiltrates, pleural effusions, or hilar lymphadenopathy.



Chest radiographic findings suggest certain diseases, although the diagnosis ultimately depends on a thorough clinical history. When a specific xenobiotic exposure is known or suspected, the chest radiograph can confirm the diagnosis and help in assessment. If a history of xenobiotic exposure is not obtained, a patient with an abnormal chest radiograph can initially be misdiagnosed as having pneumonia or another disorder that is more common than xenobiotic-mediated lung disease. Therefore, patients with chest radiographic abnormalities should be carefully questioned regarding possible xenobiotic exposures at work or at home, as well as the use of medications or other drugs.



Many pulmonary disorders are radiographically detectable because they result in fluid accumulation within the normally air-filled lung. Fluid accumulates within the alveolar spaces or interstitial tissues of the lung, producing the two major radiographic patterns of pulmonary disease, airspace filling and interstitial lung disease (Table 8–3). Most xenobiotics are widely distributed throughout the lungs and produce diffuse rather than focal radiographic abnormalities.

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