677 Plasma proteins Serum protein electrophoresis (SPEP) distinguishes a number of bands (see F igure 17.6, p. 680 ). Albumin is synthesized in the liver; t \211\210 20 d. It binds bi lirubin , free fatty acids , calcium , and some drugs (penicillin and acetylsalicylic acid) . It typically requires a fall in albumin of 30% before it shows up on a electrophoresis. Low albumin may result in edema from low oncotic pressure. Causes: Liver disease, nephrotic syndrome, burns, protein-losing enteropathy, malabsorp- tion, malnutrition, late pregnancy , artifact (e.g., from arm with IVF), posture (5 g/L higher if upright), genetic variations , malignancy. Causes of high albu- min: Acute dehydration; artifact (e.g., stasis). 1 Zo ne 1 -Antitrypsin, thyroid-binding globulin, 1 glycoprotein (oroso- mucoid), and high -density lipoprotein (HDL). A decreased band may be seen: Cirrhosis and nephrotic syndrome. 2 Zone 2 -Macroglobulin, ceruloplasmin, and haptoglobin (predominant component). The 2 zone is typically decreased in hemolytic anemia. Zone Transferrin (major band), low -density lipoprotein (LDL), fibrino- gen, and C3 complement (C4 may be visible if increased or high-normal). Reduced in active glomerulonephritis and systemic lupus erythematosus (SL E). Zone Immunoglobulins and C-reactive protein (CRP). Diffusely raised in chronic infec tions, liver cirrhosis, sarcoidosis, SLE, rheumatoid arthritis (RA), Crohn \200\231s diseas e, TB, bronchiectasis, primary biliary cirrhosis (PBC), hepatitis, and parasitemia. It is l ow in nephrotic syndrome, malabsorption, malnutrition, immune deficiency (severe illness, d iabetes mellitus, renal fail- ure, malignancy, or congenital). Paraproteinemia See p. 635. Acute-phase response The body responds to a variety of insults with, among other things, th e synthesis by the liver of a number of proteins (normally present in serum in small quanti ties) \200\224e.g., 1 -antitrypsin, fibrino- gen, complement, haptoglobin, and CRP. An in creased density of the 1 - and 2 -fractions, often with a reduced albumin level, is c haracteristic of conditions such as infection, malignancy (especially if the 2 -fraction is elevated), trauma, surgery, and inflammatory disease. CRP Levels help monitor inflammati on/infection. Normal <0.5 mg/ d L, but can be elevated age, race, BMI, and smoking . Like t he ESR, it is raised in many inflammatory conditions, but changes more rapidly; increases i n hours and falls within 2 \200\2233 d of recovery. Therefore, it can be used to follow the response to therapy (e.g., antibiotics in osteomyelitis) or disease activ- ity (e.g., Croh n \200\231s disease). CRP values in mild inflammation are 10 \200\22350 mg/L; active bacter ial infection, 50 \200\223200 mg/L; severe infection or trauma >200 mg/L; see Table 17.12. Elevated CRP levels may suggest an increased risk in patients with cardiovascular disease i f measured using a highly sensitive assay. Low risk <1 mg/dL; moderate risk 1 \200\2233; an d high risk >3 mg/L. Urinary proteins If urinary protein loss is >0.15 g/24 h (24 h urine), then this is considered pathological. Albuminuria Caused by kidney disease. Microalbuminur ia (albumin excretion between 30 \200\223300 mg/d) is an important screening test for diabe tic nephropathy. >300 mg/d of albuminuria is considered macroalbuminuria or clinical protei nuria. Microalbuminuria by spot urinary albumin to creatinine ratio is 30 \200\223300 mg/g creatinine. Bence Jones proteinuria consists of light chains excreted in excess by some pat ients with myeloma. They are not detected by dipsticks and may 678 occur with normal serum electrophoresis. Typically diagnosed with urinary electrophoresis ( UPEP). Serum free light chains Recently, a highly sensitive assay has been developed to mea sure and light chains (Freelite \204 ) as an indicator of monoclonality. Serum free light chains have a greater sensitivity than SPEP, UPEP, and immunofixation electrophoresi s (IFE) alone in the detection of myeloma, light chain myeloma, and nonsecretory myeloma an d are impor- tant in both treatment response and prognosis. y r t s i m e h c o B i Plasma enzymes Reference intervals vary between laboratories. Raised levels of specific enz ymes can be a useful indicator of a disease. However, remember that most can be raised for other reasons, too. The major causes of raised enzymes are given below. Alkaline phosphatase \212 \212 Liver disease (suggests cholestasis) Bone disease (isoenzyme distinguishable, reflects oste oblast activity) espe- cially Paget \200\231s, growing children, healing fractures, osteoma lacia, metasta- ses, primary hyperparathyroidism, and renal failure Pregnancy (placenta mak es its own isoenzyme) \212 Alanine-amino transferase (ALT; serum glutamic-pyruvic transaminase [ SGPT ]) \212 Liver disease (suggests hepatocyte damage); also raised in shock Amylase \212 \212 Acute pancreatitis (not chronic pancreatitis as little tissue remaining) Severe uremia, dia betic ketoacidosis serum glutamic-oxaloacetic Aspartate-amino transferase (AST; transaminase [ SGOT ]) \212 \212 \212 CK \212 Liver disease (suggesting hepatocyte damage) MI Skeletal muscle damage and hemolysis MI (isoenzyme \200\234CK-MB. \200\235 MI diagnosed if CK-MB >6% total CK, or CK-MB mass >9 9 percentile of normal) Table 17.12 CRP Marked elevation Bacterial infection Normal to slight elevation Viral infection 679 Abscess Crohn \200\231s disease Connective tissue diseases ( SLE) Steroids/estrogens Ulcerative colitis Atherosclerosis Neoplasia Trauma Necrosis (e.g., MI) Figure 17.6 LDL \212 Muscle damage (rhabdomyolysis, prolonged running, hematoma, seizures, IM injection, defibri llation, bowel ischemia, myxedema, dermatomyositis) and drugs (e.g., statins). A raised CK does not necessarily mean an MI. GGT \212 Liver disease (particularly alcohol-induced damage, cholestasis, drugs) LDH \212 \212 \212 MI(nonspecific) Liver disease (suggests hepatocyte damage) Hemolysis, pulmonary embolism, a nd tumor necrosis Tumor markers Tumor markers are rarely sufficiently specific to be of diagnostic value. The ir main value is in monitoring the course of an illness and the effectiveness of treatment. Reference ranges vary between laboratories. -Fetoprotein Elevated in hepatocellular CA, germ cell tumors (not pure seminoma), hepatitis, cirrhosis, pregnancy, open neural tube de fects. CA 125 Elevated in carcinoma of the ovary, uterus, breast, and hepatocel- lular carc inoma. Also raised in pregnancy, cirrhosis, and peritonitis. CA 15 \200\2233 Elevated in ca rcinoma of the breast and benign breast disease CA 19 \200\2239 Elevated in colorectal and pancreatic carcinoma, and in cholestasis Carcino-embryonic antigen (CEA) Elevated in gastro intestinal neo- plasms, especially colorectal CA. Also cirrhosis, pancreatitis, and smoking . Human chorionic gonadotrophin Elevated in pregnancy and germ cell tumors. Neuron specific enolase (NSE) Elevated in small-cell carcinoma of lung and neuroblastoma. Placental alkali ne phosphatase (PLAP) Elevated in pregnancy, carci- noma of ovary, seminoma, and smoking. P rostate-specific antigen (PSA) See Table 17.13. 680 y r t s i Table 17.13 Prostate specific antigen (PSA) As well as being a marker of prostate cancer, PSA is (unfortunately) Elevated in benign pro static hypertrophy. 25% of large benign prostates emit PSA up to 10 mcg/L; levels may be hi gher if recent ejaculation; therefore, avoid ejaculation for 24 h prior to measurement. Oth er factors causing raised PSA include recent rectal examination, prostatitis, and UTI (PSA levels may not return to baseline for some months after the latter). * Plasma reference int erval is age-specific; an example of the top end of the reference interval for total PSA is : m e h c o B i Healthy males of age (yrs) 40 \200\22350 50 \200\22359 60 \200\22369 70 \200\22379 80 \200 \22389 PSA mcg/L 2.5 3.5 5.0 6.5 7.5 \212 This is a rough guide only; different labs have different reference ranges and populations vary. More specific assays, such as free PSA/total PSA index, and PSA density, are also bec oming available, which may partly solve these problems. It is shown to illustrate the commo n problem of interpreting a PSA of 8 \200\224and as a warning against casual requests for PSAs in the (vain) hope of simple answers. The following indicates the proportion of patien ts with a raised PSA and benign hypertrophy or carcinoma. PSA mcg/L <4 in 91% 4 \200\22310 in 8% >10 in 1% <4 in 15% 4 \200\22310 in 20% >10 in 65% Benign prostatic hypertrophy PSA will be 50% lower after 6 months on 5 \227 reductase inhibitors Prostate carcinoma Up to 6 months in one study (Aus G. Urology. 2003;62:278). 681 The porphyrias The acute porphyrias are rare genetic diseases caused by errors in the pathw ay of heme biosynthesis resulting in the toxic accumulation of porpho- bilinogen and -am inolevulinic acid (porphyrin precursors). Characterized by acute neurovisceral crises, due to the increased production of porphyrin precursors and their appearance in the urine. Some forms have cutaneous manifestations. Prevalence: 1 \200\2232/100,000. Acute intermittent p orphyria A low-penetrant autosomal dominant condi- tion (porphobilinogen deaminase gene); 2 8% have no family history ( de novo mutations ). 10% of those with the defective gene have neurovisceral symptoms. Attacks are intermittent, more common in women, and may be precipi tated by many drugs (see below). Urine porphobilinogens are raised during attacks and often (50%) between them (the urine may go deep red on standing). Fecal porphyrin levels are nor mal. There are no skin manifestations. Variegate porphyria and hereditary coproporphyria: A utosomal dominant, characterized by photosensitive blistering skin lesions, and/or acute at tacks. The former is prevalent in Afrikaners in South Africa. Porphobilinogen is high only in an attack, and other metabolites may be detected in feces. Features of an acute attack C olic vomiting fever WBC \206\221 \200\224so mimicking an acute abdomen (anesthes ia can be disastrous here). Also: Hypotension Hyponatremia Hypokalemia Hypotonia \212 \212 \212 \212 \212 \212 \212 \212 Proteinuria Psychosis/odd behavior Peripheral neuritis Paralysis \212 \212 \212 \212 Seizures Sensory impairment Sight may be affected Shock ( collapse). Drugs to avoid in acute intermittent porphyria are legion (they may precipitate above sympt oms quadriplegia); they include: Alcohol, several anesthetic agents (barbiturates, halot hane), antibiotics (chloramphenicol, sulfonamides, tetracyclines), painkillers (pentazocine ), oral hypoglycemics, contraceptive pill. Treatment of an acute attack \212 \212 \212 \212 Remove precipitants, then: Give IV fluids to correct electrolyte imbalance. Institute high carbohydrate intake (e.g., Hycal ) by NG tube if necessary. IV hematin to replenish heme s tores is the treatment of choice when available. Nausea is controlled with prochlorperazine 12.5 mg IM. Sedation, if necessary, is with chlorpromazine 50 \200\223100 mg PO/IM. Pain c ontrol is usually with opioids. Seizures can be controlled with benzodiazepines. Treat tach ycardia and hypertension with propranolol. \212 \212 \212 \212 \212 Nonacute porphyrias Porphyria cutanea tarda, erythropoietic p rotoporphyria, and congenital erythro- poietic porphyria are characterized by cutaneous pho tosensitivity alone, as there is no overproduction of porphyrin precursors, only porphyrins . Alcohol, lead, and iron deficiency cause abnormal porphyrin metabolism. Offer genetic cou nseling to all patients and their families. 682 This page intentionally left blank Radiology Sumera Ali , M.D. and Clifford R. Weiss , M.D. y g o o d a R l Contents General principles 684 Help the radiologist help you! 684 Radiation exposure 686 Contrast a gents 686 The basics of radiography 689 General concepts 689 The chest movie 691 The abdomi nal movie 696 Modalities 702 Ultrasonography 702 Computed tomography 704 Magnetic resonance imaging 705 Nuclear medicine (radionuclide scanning) 706 Positron emission tomography 707 Organ systems 708 Gastrointestinal radiology 708 Genitourinary radiology 710 Thoracic radio logy 711 Neuroradiology 712 Musculoskeletal radiology 716 i 8 1 General principles Help the radiologist help you! Radiology is a powerful diagnostic and th erapeutic tool that has become indispensable to modern-day medical practice. Not only have new, cutting-edge diagnostic techniques been introduced, but almost all existing modalities have been revolutionized. This has made available a wide array of imaging studies from whi ch to choose. When faced with a diagnostic inquiry, one must choose the most appropriate im aging study. In choosing, there are many aspects to consider, including invasiveness, cost, radiation exposure, sensitivity and specificity, and local expertise. The challenge of ord ering imaging tests deepens because most imaging tests can be tailored to maximize sensitiv ity and specificity depending on the patient \200\231s underlying disease process and suspe cted diagnosis (e.g., obtaining multiphasic liver computed tomography [CT] scan [unenhanced , arterial, and portal venous phases] of a patient with suspected liver lesions can help di fferentiate cysts, hemangiomas, and hypervascular or avascular tumors). These consider- ati ons fall well within the scope of a radiologist, and involving them at an early stage in de cision making can greatly speed up the diagnostic process, saving clinician and patient tim e and money. When communicating with a radiologist, it is important to realize that many im aging findings are nonspecific and can be interpreted differently depending on the clinical history. Hence, it is of utmost importance to pro- vide relevant and specific clinical inf ormation to the radiologist when order- ing the imaging study. This information may mean th e difference between a broad differential diagnosis and a single definitive diagnosis, or m ay even allow the radiologist to detect subtle findings. For example, describing the mechan ism of injury in a trauma patient can improve the detection and location of fractures or so ft-tissue damage. 684 For any radiologic study ask yourself: How can I help the radiologist help me? Before order ing a test Before ordering a test, ask yourself relevant questions: \212 y g o o d a R l What do I need to know? How will this imaging test alter the manage- ment or change the out come of the patient? What conditions will I be able to rule in or rule out with this invest igation? Is the patient fit to have the examination? What is the urgency of the study? i \212 \212 \212 This last question is essential to nighttime/off-hours radiology, in order to h elp the radiologist triage studies. Nonessential studies performed when a radiology departm ent is understaffed can make it very difficult to provide essential care to critically ill patients. At the time of ordering the investigation After you have decided that a patient w ill benefit from a certain exam, it is time to request the investigation: Provide the radio logist with relevant clinical history : Clear and concise clinical information allows the r adiologist to perform the appropriate test, modify the imaging procedure to increase specif icity in the characterization of pathology, advise an alternative test that may be more app ropriate, and interpret the findings properly in the context of the clinical information at hand. The first portion of a clinical history is what is normally put in the first line of a good internal medicine presentation: The patient \200\231s age, sex, significant underly ing diseases, relevant past surgical his- tory, current symptoms prompting the examination (with as much spatial/ anatomic localization as possible), and the suspected diagnosis or d ifferen- tial diagnosis. For example: \200\23465-year-old woman with a past medical histor y of pancreatic cancer, now with calf pain followed by acute onset shortness of breath and tachycardia, suspect pulmonary embolus. \200\235 Prepare the patient before the procedure : The following questions should be considered: \212 Is the patient aware that she is going to have the study, and is she willing? Is the patien t able to undergo the procedure? Can the patient be moved? One key question is: Is the pati ent too heavy to fit on the imaging table? Is the study contraindicated for any reason? Con traindications will vary based on imaging modality and organ system under consideration. Is the patient properly prepared for the procedure? Does he need to be NPO? Does he need to h ave a full bladder or a Foley catheter in place? Does he need to receive oral contrast befo re coming down for his pro- cedure (and if so, how much and for how long beforehand)? Is he going to receive IV contrast, and, if so, does he have appropriate IV access? Does the pat ient need consent for the procedure (always for interven- tional radiology procedures)? If so, can the patient give consent? Does the patient need to be well hydrated for the procedu re? Do any medications need to be given before the procedure, either as premedication or as part of procedure, or do any medications need to be stopped? \212 \212 After the investigation has been performed Does patient need observation? Many investigatio ns may require observ- ing the patient for a certain time. For example, creatinine needs to be monitored in patients with poor renal function who have undergone contrast-enhanced stu dies. Interpreting the image : The interpretation can be very modality-, system-, and patho logy-specific, but general rules are to have a systematic approach, compare it to previous examinations, and keep the patient \200\231s clinical condi- tion in mind. 685 Ask the radiologist for advice : Radiologists are imaging specialists and should always be consulted for image findings post study. Radiation exposure Justifying the exposure Although medical imaging is an invaluable diagno stic tool, it is crucial to know that it accounts for almost half of the radiation exposure experienced by the population in the United States. Exposure from a single procedure is li kely to be very small and clinically irrelevant. However, cumulative doses in a patient pop ulation undergoing frequent and repeated imaging significantly increases the risk of radiat ion-induced malignancies and has become a public health concern. 1 Effective dose is the ca lculated measure most commonly used to compare the detrimental effects such as cancer and h ereditary effects due to ionizing radiation. It is the weighted average of doses to the org ans that have been exposed, taking into account the radiosensitivity of the organs. It is m easured in sieverts (Sv) or rems (100 rem = 1 Sv). The average effective doses for the most common radiologic and nuclear medicine procedures in the United States for the adult popul ation have been determined and are shown in Table 18.1. 2 What can you do? There are guidin g principles that one should keep in mind when ordering an investigation. 3 Justification: Make sure that there is an appropriate indication for the procedure, and it is not being re peated for no reason. Optimization: Following the protocols designed to obtain images at as low as reasonably achievable dose (ALARA principle) while still achieving a diagnostic stu dy. Limitation : Setting a maximum aggregate dose a patient can receive in a specified time period. Restriction: Limit the region scanned to the smallest area necessary. Furthermore, the American College of Radiology (ACR) has developed appropriateness criteria of imaging for specific clinical conditions to reduce the number of unnecessary scans for inappropriat e indications. These can be found at http://www.acr.org/ac Contrast agents Intravenous contrast for imaging procedures involving ionizing radiation is iodine-based, whereas almost all magnetic resonance imaging (MRI) and magnetic resonance a ngiography (MRA) procedures that are contrast-based use gadolinium compounds. Iodinated rad iocontrast agents can either be ionic or nonionic and are available in various concentratio ns as com- pared to plasma. These are high-osmolal (HO), low-osmolal (LO), and iso-osmolal (IO) contract material in descending order of osmolality. Low and iso-osmolal and nonionic agents are associated with decreased inci- dence of immediate hypersensitivity reactions an d contrast-induced neph- ropathy. Low osmolal nonionic agents have replaced HO contrast in clinical practice. If a contrast is required, specific indications should be present, and t he patient should be assessed for potential risk factors for adverse reactions. 686 1 Brenner DJ, EJ Hall. Computed tomography: An increasing source of radiation exposure. N E ngl J Med . 2007;357(22):2277 \200\2232284. 2 Mettler FA Jr., et al. Effective doses in rad iology and diagnostic nuclear medicine: A catalog. Radiology . 2008;248(1):254 \200\223263. 3 McCollough CH, et al. Strategies for reducing radiation dose in CT. Radiol Clin North Am . 2009;47(1):27 \200\22340. y g o o d a R Examination Average effective dose (mSv) Values reported in literature (mSv) Equivalent chest x-ray* l i Various diagnostic radiology procedures Skull Cervical spine Thoracic spine Lumbar spine Posteroanterior and 0.1 0.2 1.0 1.5 0.1 0.03 \200\2230.22 0.07 \200\2230.3 0.6 \200\2231.4 0.5 \200\2231.8 0.05 \200\2230.24 1 2 10 15 1 lateral study of chest Posteroanterior study of 0.02 0.007 \200\2230.050 0.2 chest Mammography Abdomen Pelvis Hip Shoulder Knee Other extremities Dual x-ray absorptiom- etry (without CT) Dual x-ray absorptiom- 0.4 0.7 0.6 0.7 0.01 0.005 0.001 0.001 0.10 \200\2230.60 0.04 \200\2231.1 0.2 \200\2231.2 0.18 \200\2232.71 \200\223 \200\223 0. 0002 \200\2230.1 0.001 \200\2230.035 4 7 6 7 0.1 0.05 0.01 0.01 0.04 0.003 \200\2230.06 0.4 etry (with CT) Intravenous urography Upper gastrointestinal 3 6 0.7 \200\2233.7 1.5 \200\22312 30 60 series Small-bowel series Barium enema Various CT Procedures Head Neck Chest Chest for pulmonary 5 8 3.0 \200\2237.8 2.0 \200\22318.0 50 80 2 3 7 15 0.9 \200\2234.0 \200\223 4.0 \200\22318.0 13 \200\22340 20 30 70 150 embolism Abdomen Pelvis Three-phase liver study Spine Coronary angiography Calcium scoring Virtual c olonoscopy 8 6 15 6 16 3 10 3.5 \200\22325 3.3 \200\22310 \200\223 1.5 \200\22310 5.0 \200\22332 1.0 \200\22312 4.0 \200\22313.2 80 60 150 60 160 30 100 687 (Continued) Examination Values reported in literature (mSv) Various Interventional Radiology Procedures 0.8 \200 \22319.6 Head and/or neck angiography Average effective dose (mSv) Equivalent chest x-ray* 5 50 Coronary angiography 7 2.0 \200\22315.8 70 (diagnostic) Coronary percutaneous 15 6.9 \200\22357 150 transluminal angioplasty stent placement or radiofrequency ablation Thoracic angiography of pulmonary artery or aorta 5 4.1 \200\2239.0 50 Abdominal angiography or 12 4.0 \200\22348.0 120 aortography Transjugular intrahepatic portosystemic shunt placement 70 20 \200\223180 700 Pelvic vein embolization 60 44 \200\22378 600 One chest x-ray: 0.1 mSv Adapted from Mettler FA, et al. Effective doses in radiology and d iagnostic nuclear medicine: A catalog. Radiology . 2008; 248(1):254 \200\223263. Immediate hypersensitivity reactions (IHR) Any contrast agent administered intravenously ca n cause adverse reactions. These reactions are idiosyncratic and are not related to the dos e. IHR can be classified based on its severity and may range from mild flushing, pruritus, and urticaria to more severe angioedema, laryngospasm, bronchospasm, and hypotension. Adver se reactions occur in 1/1,000 patients and death by anaphylaxis in 1/40,000. The osmolali ty of the agent is strongly associated with IHR. 4 Risk factors for contrast reaction shoul d always be reviewed prior to imaging. The most significant risk factor for IHR is a previo us IHR. Other risk factors include asthma, atopic diseases, and possibly the use of -blo ckers or NSAIDs. With a previous history of IHR, the patient may require premedication with steroids. A common regimen includes prednisone 40 mg PO, 24 h, 12 h, and 1 h before and 12 h after the procedure, with or without a dose of diphenhydramine (50 mg PO or IV 1 h) befo re the procedure. When the patient has a history of severe anaphylactic reaction to IV cont rast, iodine-based contrast is absolutely contraindicated. It is important to note that the re is no proven link between seafood and contrast allergies. Contrast-mediated nephrotoxici ty Risk factors include congestive heart failure, diabetes, preexisting renal insufficiency , age >70, concurrent nephrotoxic medications, high-dose hyperosmolar IV contrast, diuretic 688 4 Greenberger PA, Patterson R. The prevention of immediate generalized reactions to radioco ntrast media in high-risk patients. J Allergy Clin Immunol . 1991;87(4):867 \200\223872. medications, or dehydration. IV 0.9% saline 1 mL/kg/h, 4 \200\2236 h before contrast admini stration and 12 \200\22324 h after exposure, significantly reduces the risk of contrast nep hrotoxicity in patients with mild renal insufficiency. The use of sodium bicarbonate drip i nstead of NS is shown to be superior in some studies, but other studies have shown conflict ing results. The efficacy of N-acetylcysteine, an antioxidant, to reduce the occurrence of contrast-induced nephrotoxicity (CIN) is also undetermined but is often used. It is dosed a t 600 mg PO bid for 24 h before contrast administration and on the day of contrast, along w ith hydration. When possible, it is beneficial to discontinue nephrotoxic medications (e.g. , metformin and diuretics) for at least 24 h after contrast administration. Low-osmolar con trast media are less nephrotoxic than high-osmolar contrasts in patients with renal insuffi ciency. Alternative imaging modalities such as magnetic resonance, ultrasound (US), and nuc lear scintigraphy should be considered in patients at high risk of developing contrast neph ropathy. Gadolinium contrast Gadolinium is a very safe contrast agent used in MR imaging in patients with normal renal function. It is completely unrelated to CT/angiographic iodinat ed contrast, and gadolinium allergies are extremely rare. Gadolinium should be avoided in p regnant patients and in patients with renal insufficiency / failure. Nephrogenic systemic f ibrosis/Nephrogenic fibrosing dermopathy (NSF/NFD) was first described in 2000 and is a rel atively newer described complication of gadolinium in patients with renal failure. NSF/NFD is seen in patients who have noticeably advanced chronic renal failure corresponding to est imated glomerular filtration rate (eGFR) values of <29 mL/min/1.73 m 2 and acute kidney inj ury. The reported incidence of developing NSF ranges from 1% to 7% after exposure to gadoli nium in patients with chronic renal disease. The disease causes fibrosis of the skin and co nnective tissues throughout the body. Patients develop skin thicken- ing that may prevent b ending and extending joints, resulting in decreased mobility of joints. In addition, patien ts may experience fibrosis that spreads to other parts of the body such as the diaphragm, m uscles in the thigh and lower abdomen, and the interior areas of lung vessels. The clinical course of NSF/NFD is progressive and may be fatal. In general, due to NSF/NFD, the adminis tration of gadolinium-based con- trast agents in patients with renal failure or renal insuf ficiency is contrain- dicated. However, your institution \200\231s policy regarding NSF/NFD should be consulted. y g o o d a R l i The basics of radiography General concepts Images are obtained by transmitting x-rays (ioni zing radiation) through the body to a detector (movie or a photosensitive plate in digital image systems). The image obtained represents a \200\234shadowgram \200\235 as the body ab sorbs different amounts of radiation depending on the density of the tissue. Denser tissues , such as bone, absorb more radiation and appear white, and less dense tissues, such as lun g, absorb less radiation and appear dark as more x-rays reach the movie and expose the phot osensitive cells. Although this modality does use ionizing radiation, doses are fairly low, and, other than early pregnancy, there is essentially no contraindication to obtaining a r adiograph. Radiographs also have the advantage of being portable and have no weight limitat ions, although heavier patients require more radiation and create noisier films. 689 Basic considerations \212 Because these are two-dimensional images of \200\234One view is no view. \200\235 three-di mensional structures, two orthogonal views should always be obtained, if possible Radiog raphs done on fixed equipment Not all radiographs are equal within a radiology department a re generally of higher quality than are radiographs acquired portably. This is due to the p resence of a better grid system and the ability to better position the patient on the stati onary system. Thus, if the patient can be safely moved to radiology department, he or she s hould be Radiographs are most diagnostic Order coned (region-specific) radiographs in th e center of the x-ray beam, where the photons are parallel. Thus, if the area of interest i s the wrist, order a wrist series and not a forearm series. This will place the wrist in th e center of the field of view Radiographs are excellent screening tools, Do not skip the radiograph are often diagnostic, and usually should be obtained before other more expensiv e and time-consuming imaging modalities. (One glaring excep- tion to this rule is skull rad iographs \200\224which are obsolete and have been replaced by CT.) \212 \212 \212 Basic steps in interpreting any radiograph 1 Check the technical accuracy of the movie: Is the movie named, dated, right/left orientated, and marked as to whether AP (anteroposterior ), PA (poster- oanterior), erect, or supine. X-ray beam penetration is important; ideally, vertebral bodies are visible through heart on a chest x-ray (CXR). If the movie is underpen etrated, diffuse \200\234whitening \200\235 effect and poor anatomical detail is present. Check for rotation (e.g., check for asymmetry of clavicles on a CXR) as this may affect the appearances of normal structures, such as the hila. 2 Describe the abnormalities seen: This may be a change in the appear- ance of normally vis ualized structures or an area of increased opacity or translucency. Plain radiographs identify the interfaces between different densities. These interfaces occ ur, and are visible on the movie, only when two different tissue densities are immediately adjacent to each other. These densities are: \212 \212 \212 Gas Fat (normal adipose tissue, lipomas, oily deposits, etc.) Soft tissue (like muscle, ten don, ligament, water, visceral organs, blood vessels, nerves, etc.) Calcified structures (b one, calcified granulomas, tumoral calcinosis, etc.) Metallic structures (surgical clips, r adiodense markers in central lines, bullet fragments) \212 \212 A border is seen at an interface of two densities; e.g., heart (water) and lung (air). This \200\234silhouette \200\235 is lost if air in the lung is replaced by consolida- tion (wa ter). This is called the silhouette sign and can be used to localize pathology (e.g., right middle lobe pneumonia or collapse causing loss of distinction of the right heart border). See p. 153 (pulmonary medicine), which describes the methods for localizing collapse/consol idation in the lungs; see Figure 6.1. 3 Translate the abnormalities into gross pathology (e .g., pleural fluid, lung 690 consolidation, free air in the abdomen). 4 Suggest a differential diagnosis: Develop a structured approach so as not to miss any maj or abnormality. Try not to jump immediately to one diag- nosis, and develop your differenti al based both on radiologic findings and patient history/physical findings. 5 Treat the patient, not the movie. The chest movie See Figures 18.1 \200\22318.7, and PLATES 1 \200\2238 Before you start Orde r the best possible exam : Upright PA and lateral views are the standard initial imaging of choice for almost all cardiopulmonary disease. These com- plementary views are particularl y important when localization of a lesion/ pathology is required. An ideal PA view is taken with the patient in an upright position with full inspiration, and it demonstrates no rota tion or motion and minimal overly- ing osseous structures. However, this ideal is rarely se en in chest x-rays taken in ICU and emergency settings. y g o o d a R l i The interpretation \212 \212 Double-check the name on the movie . Comment on the quality of the movie ( \200\234RIPE \200\235): Rotation : The spinous process of T3 should be midway between the clavicles. Inspiration : 5 \200\2237 ribs anteriorly or 9 \200\22310 ribs posteriorly are visible in f ull inspiration. Position of the patient : Entire thorax from larynx to costophrenic angles should be visible. Exposure : Pulmonary vessels and thoracic vertebra should be visible through the heart. \212Look thoroughly and systematically . Examine all the structures, including visible por tions of the abdomen, bones, mediastinum, lungs together (to judge symmetry), and lungs sep arately Age and progression of find- Compare to old examinations when possible ings can be crucial to diagnosis and treatment. For example, a calcified nodule that has remained un changed over years may merely be a calcified granuloma. \212 Lines and hardware: All lines and hardware need to be identified and exam- ined for correct location and potential complications. Remember, all the hardware visible on CXR may not be inside the patient (e.g., electrocardio- gram [ECG] leads, oxygen lines, etc.). Examples o f common hardware in- clude central venous catheters (check for tip location and for pneumo tho- rax), endotracheal tubes (typically, the tip should be above the carina to avoid endob ronchial intubation), chest tubes, feeding tubes (nasogastric or naso-duodenal \200\224tip locations are key), sternal wires (are these intact?), prosthetic valves, implantable cardi oversion devices (ICDs/pacers), vagus nerve stimulators, Swan \200\223Ganz catheters, etc. The diaphragm: The right hemidiaphragm is higher than the left by up to 3 cm in 95% of case s. The lateral costophrenic angles should be sharp and acute. They may be ill-defined in hy perinflation or with effusion. On a lat- eral view, the right hemidiaphragm passes through the heart to the anterior chest wall, whereas the left ends at the posterior heart border. Causes of raised hemidiaphragm include eventration of diaphragm, enlarged liver or spleen, phrenic nerve paralysis, or lobar collapse. Trachea: The trachea is central or maybe slight ly to the right. Trachea may be deviated toward the lesion (collapse), away from the lesion (tension pneumothorax) or deviated from patient rotation. Paratracheal line is com- monly <5 mm; its thickening and nodularity suggest paratracheal lymph- adenopathy/mass. Heart: Lo ok for the landmarks. The cardiothoracic ratio is the ratio of the heart width to the chest width. It should be <50% (essential to have a PA 691 movie as the heart is magnified on AP or supine films). Ratios larger than this suggest car diomegaly due to any number of causes. Mediastinum: Mediastinal widening may be due to aort ic aneurysm or dis- section, mediastinal fluid, enlarged lymph nodes, thymus, thyroid, or t u- mor. The hila: Composed of pulmonary arteries, pulmonary veins, lymph nodes, and airways . Left is higher than right ( 1 cm) 95% of the time. Look for change in density and/or roun ded configuration. This could be due to tu- mor, enlarged lymph nodes, hypoinflation, or ju st a rotated movie. The lungs \200\234Too black \200\235: \212 Pneumothorax: Absent vascular markings and visceral pleura/lung edge visible Bullous change : I.e., emphysema Chronic pulmonary embolus: Localized oligemia (regional lack of visual- i zation of pulmonary blood vessels) Hyperinflation in chronic obstructive pulmonary disease (COPD) Absent anterior chest wall structures: I.e., mastectomy or Poland \200\231s syndrome \200\234Too White \200\235: \212 \212 \212 \212 \212 Consolidation: Lobar or segmental opacity, plus air bronchogram if air- ways remain air-fil led but little volume change (unlike collapse) Collapse/atelectasis: Volume loss causes shi ft of the normal landmarks (hila, fissures, diaphragm, etc.) Pulmonary nodules ( \200\234co in \200\235 lesions <3 cm in diameter): These are often \200\234incidentalomas \200\235 an d need to be differentiated into either benign or malignant lesions based on their characte ristics \200\224but most importantly in comparison to older films. \200\234Ring \200\235 s hadows: Either airways with peribronchial \200\234cuffing \200\235 (pulmonary edema, bronc hiectasis), or cavitating lesions (e.g., abscess [bacterial, fun- gal]) or tumor Interstiti al pattern: Pulmonary interstitium is normally not seen on CXR. Abnormal interstitial patte rns maybe seen as linear opacities ( Kerley \200\231s B lines , interlobular lymphatics see n in low-pressure pulmonary edema or lymphangitic spread of tumor); discoid atelectasis, li near band of atelecta- sis; reticulonodular pattern , multiple intersecting irregular lines interspersed with small 1 \200\2232 mm nodules, seen in pulmonary fibrosis or interstitial pneumonitis. \212 \212 \212 \212 Acute conditions not to miss \212Pneumothorax is commonly associated with trauma or can be iatrogenic. It may occur spontaneously in emphysema. In tension pneumothorax, the lung may be severely collapsed with mediastinal shift to the opposite side, with scooping of the ip silateral hemidiaphragm. There may also be subcutaneous air/subcutaneous emphysema. This is a medical emergency and requires immediate decompression followed by placement of a chest tube. in a patient with chest pain and/or history of trauma Widened mediastinum may represe nt aortic aneurysm or dissection, traumatic transection, or mediastinal hematoma. Free air in the abdomen sents free intraperitoneal air and may suggest a bowel perforation. \212 692 \212 seen under the right hemidiaphragm; this repre- Don \200\231t \212 After identifying one example of Succumb to \200\234satisfaction of search \200\235: patho logy on the image, don \200\231t give up your search until you have thor- oughly examined t he whole movie, including all the corners; there may be two or more important findings! y g o o d a R Figure 18.1 Posteroanterior chest radiograph of a female showing basic anatomical structure s l i Figure 18.2 Lateral chest radiograph of a female showing basic anatomical structures 693 Figure 18.3 3D coronal CT of the chest demonstrating heart and vascular structures Figure 18.4 3D coronal CT of the chest demonstrating heart and vascular structures 694 y g o o d a R Figure 18.5 3D sagittal CT of the chest demonstrating midline structures of the chest and v ertebral column l i Figure 18.6 3D sagittal CT of the chest demonstrating structures on the left side of the ch est 695 Figure 18.7 3D coronal CT of the chest demonstrating bronchial and pulmonary vascular tree \212 : Apices, aortopulmonary (AP) angle, retro-