Items in AFP with MESH term: Contrast Media
Acute Renal Failure - Clinical Evidence Handbook
Chronic Pancreatitis - Article
ABSTRACT: Chronic pancreatitis is the progressive and permanent destruction of the pancreas resulting in exocrine and endocrine insufficiency and, often, chronic disabling pain. The etiology is multifactorial. Alcoholism plays a significant role in adults, whereas genetic and structural defects predominate in children. The average age at diagnosis is 35 to 55 years. Morbidity and mortality are secondary to chronic pain and complications (e.g., diabetes, pancreatic cancer). Contrast-enhanced computed tomography is the radiographic test of choice for diagnosis, with ductal calcifications being pathognomonic. Newer modalities, such as endoscopic ultrasonography and magnetic resonance cholangiopancreatography, provide diagnostic results similar to those of endoscopic retrograde cholangiopancreatography. Management begins with lifestyle modifications (e.g., cessation of alcohol and tobacco use) and dietary changes followed by analgesics and pancreatic enzyme supplementation. Before proceeding with endoscopic or surgical interventions, physicians and patients should weigh the risks and benefits of each procedure. Therapeutic endoscopy is indicated for symptomatic or complicated pseudocyst, biliary obstruction, and decompression of pancreatic duct. Surgical procedures include decompression for large duct disease (pancreatic duct dilatation of 7 mm or more) and resection for small duct disease. Lateral pancreaticojejunostomy is the most commonly performed surgery in patients with large duct disease. Pancreatoduodenectomy is indicated for the treatment of chronic pancreatitis with pancreatic head enlargement. Patients with chronic pancreatitis are at increased risk of pancreatic neoplasm; regular surveillance is sometimes advocated, but formal guidelines and evidence of clinical benefit are lacking.
ABSTRACT: Colorectal cancer causes significant morbidity and mortality in the United States. The incidence of colorectal cancer can be reduced with increasing efforts directed at mass screening of average-risk adults 50 years and older. Currently, fecal occult blood test and flexible sigmoidoscopy have the highest levels of evidence to support their use for colorectal cancer screening. Colonoscopy does not have a proven colorectal cancer mortality benefit, but it does have the greatest single-test accuracy, and it is the final test in the pathway to evaluate and treat patients with other abnormal screening tests. Double-contrast barium enema has sparse data of effectiveness. Computed tomographic colonography, fecal DNA testing, and Pillcam Colon are promising tests that need further study before they can be recommended for widespread screening. Routine screening should continue until 75 years of age. There is good evidence that fiber and antioxidants are not effective for primary prevention of colorectal cancer; they should not be recommended for chemoprevention. There is good evidence that aspirin, nonsteroidal antiinflammatory drugs, and cyclooxygenase-2 inhibitors are effective for decreasing the risk of colorectal cancer and adenomatous polyps, but increased risks, such as gastrointestinal bleeding, limit their usefulness. There is fair evidence that obesity is associated with colorectal cancer. Additional studies are needed on decreased fat intake and red meat consumption, and the use of calcium, vitamin D, and statins before these can be recommended for primary prevention of colorectal cancer.
ABSTRACT: Adverse reactions to contrast agents range from a mild inconvenience, such as itching associated with hives, to a life-threatening emergency. Renal toxicity is a well known adverse reaction associated with the use of intravenous contrast material. Other forms of adverse reactions include delayed allergic reactions, anaphylactic reactions, and local tissue damage. Previous allergic reactions to contrast material, asthma, and allergies are factors associated with an increased risk of developing an adverse reaction. Pretreatment of patients who have such risk factors with a corticosteroid and diphenhydramine decreases the chance of allergic reactions, including anaphylaxis, renal failure, or a possible life-threatening emergency. Awareness of the different types of risk factors and prescreening for their presence allows for early recognition and prompt treatment. Prophylactic treatment before administration of contrast material can prevent potential adverse reactions. If such reactions do occur, prompt recognition allows them to be treated immediately. Using the smallest amount of contrast material possible and low-molecular, nonionic agents also decreases the relative risk of reactions. Renal insufficiency induced by contrast material may be prevented by ensuring adequate hydration and discontinuing other nephrotoxic medications before the procedure. Low-osmolar, nonionic agents are helpful in patients with known conditions associated with adverse reactions.
Progressive Skin Fibrosis - Photo Quiz
ABSTRACT: Nephrogenic systemic fibrosis is a progressive, potentially fatal multiorgan system fibrosing disease related to exposure of patients with renal failure to the gadolinium-based contrast agents used in magnetic resonance imaging. Because of this relationship between nephrogenic systemic fibrosis and gadolinium-based contrast agents, the U.S. Food and Drug Administration currently warns against using gadolinium-based contrast agents in patients with a glomerular filtration rate less than 30 mL per minute per 1.73 m2, or any acute renal insufficiency related to the hepatorenal syndrome or perioperative liver transplantation. There have been reports of nephrogenic systemic fibrosis developing in patients not exposed to gadolinium-based contrast agents, but most patients have the triad of gadolinium exposure through contrast-enhanced magnetic resonance imaging, renal failure, and a proinflammatory state, such as recent surgery, endovascular injury, or sepsis. Development of nephrogenic systemic fibrosis among patients with severe renal insufficiency following exposure to gadolinium-based contrast agents is approximately 4 percent, and mortality can approach 31 percent. The mechanism for nephrogenic systemic fibrosis is unclear, and current treatments are disappointing. Prevention with hemodialysis immediately following gadolinium-based contrast agents has been recommended, but no studies have shown this to be effective. Because of the large number of patients with clinically silent renal impairment and the serious consequences of nephrogenic systemic fibrosis related to gadolinium exposure, physicians should use alternative imaging modalities for patients who are at risk.
ABSTRACT: The differential diagnosis of left lower-quadrant pain includes gastrointestinal, gynecologic, and renal/ureteric pathology. Imaging is helpful in evaluating left lower-quadrant pain, and is generally guided by the clinical presentation. Acute sigmoid diverticulitis should be suspected when the clinical triad of left lower-quadrant pain, fever, and leukocytosis is present. The severity of disease varies from mild pericolonic and peridiverticular inflammation to severe inflammatory changes with complications such as perforation, peritonitis, or abscess or fistula formation. Computed tomography is the preferred test in evaluating clinically suspected diverticulitis. It is used to evaluate the severity and extent of disease and to identify complications, but it also may diagnose other causes of left lower-quadrant pain that can mimic diverticulitis. Magnetic resonance imaging can be used to assess left lower-quadrant pain. It has superior resolution of soft tissues and does not expose the patient to ionizing radiation, but it is expensive and requires more time to perform. Transabdominal ultrasonography with graded compression is another effective technique but is limited by its high operator dependency and technical difficulties in scanning patients who are obese. Pelvic ultrasonography is the preferred imaging modality in women of childbearing age. Radiography with contrast enema is less sensitive than computed tomography in diagnosing diverticulitis and is seldom used.
ABSTRACT: Spurred by mounting evidence that the detection and treatment of early-stage colorectal cancers and adenomatous polyps can reduce mortality, Medicare and some other payors recently authorized reimbursement for colorectal cancer screening in persons at average risk for this malignancy. A collaborative group of experts convened by the U.S. Agency for Health Care Policy and Research has recommended screening for average-risk persons over the age of 50 years using one of the following techniques: fecal occult blood testing each year, flexible sigmoidoscopy every five years, fecal occult blood testing every year combined with flexible sigmoidoscopy every five years, double-contrast barium enema every five to 10 years or colonoscopy every 10 years. Screening of persons with risk factors should begin at an earlier age, depending on the family history of colorectal cancer or polyps. These recommendations augment the colorectal cancer screening guidelines of the American Academy of Family physicians. Recent advances in genetic research have made it possible to identify persons at high risk for colorectal cancer because of an inherited predisposition to develop this malignancy. These patients require aggressive screening, usually by lower endoscopy performed at an early age. In some patients, genetic testing can guide screening and may be cost-effective.
When to Order Contrast-Enhanced CT - Article
ABSTRACT: Family physicians often must determine the most appropriate diagnostic tests to order for their patients. It is essential to know the types of contrast agents, their risks, contraindications, and common clinical scenarios in which contrast-enhanced computed tomography is appropriate. Many types of contrast agents can be used in computed tomography: oral, intravenous, rectal, and intrathecal. The choice of contrast agent depends on route of administration, desired tissue differentiation, and suspected diagnosis. Possible contraindications for using intravenous contrast agents during computed tomography include a history of reactions to contrast agents, pregnancy, radioactive iodine treatment for thyroid disease, metformin use, and chronic or acutely worsening renal disease. The American College of Radiology Appropriateness Criteria is a useful online resource. Clear communication between the physician and radiologist is essential for obtaining the most appropriate study at the lowest cost and risk to the patient.