Cholangiopancreatography, Endoscopic Retrograde: Fiberoptic endoscopy designed for duodenal observation and cannulation of VATER'S AMPULLA, in order to visualize the pancreatic and biliary duct system by retrograde injection of contrast media. Endoscopic (Vater) papillotomy (SPHINCTEROTOMY, ENDOSCOPIC) may be performed during this procedure.Cholangiopancreatography, Magnetic Resonance: Non-invasive diagnostic technique for visualizing the PANCREATIC DUCTS and BILE DUCTS without the use of injected CONTRAST MEDIA or x-ray. MRI scans provide excellent sensitivity for duct dilatation, biliary stricture, and intraductal abnormalities.Choledocholithiasis: Presence or formation of GALLSTONES in the COMMON BILE DUCT.Sphincterotomy, Endoscopic: Incision of Oddi's sphincter or Vater's ampulla performed by inserting a sphincterotome through an endoscope (DUODENOSCOPE) often following retrograde cholangiography (CHOLANGIOPANCREATOGRAPHY, ENDOSCOPIC RETROGRADE). Endoscopic treatment by sphincterotomy is the preferred method of treatment for patients with retained or recurrent bile duct stones post-cholecystectomy, and for poor-surgical-risk patients that have the gallbladder still present.Pancreatitis: INFLAMMATION of the PANCREAS. Pancreatitis is classified as acute unless there are computed tomographic or endoscopic retrograde cholangiopancreatographic findings of CHRONIC PANCREATITIS (International Symposium on Acute Pancreatitis, Atlanta, 1992). The two most common forms of acute pancreatitis are ALCOHOLIC PANCREATITIS and gallstone pancreatitis.Biliary Tract Diseases: Diseases in any part of the BILIARY TRACT including the BILE DUCTS and the GALLBLADDER.Pancreatic Ducts: Ducts that collect PANCREATIC JUICE from the PANCREAS and supply it to the DUODENUM.Hyperamylasemia: A condition with abnormally elevated level of AMYLASES in the serum. Hyperamylasemia due to PANCREATITIS or other causes may be differentiated by identifying the amylase isoenzymes.Common Bile Duct: The largest bile duct. It is formed by the junction of the CYSTIC DUCT and the COMMON HEPATIC DUCT.Common Bile Duct Diseases: Diseases of the COMMON BILE DUCT including the AMPULLA OF VATER and the SPHINCTER OF ODDI.Gallstones: Solid crystalline precipitates in the BILIARY TRACT, usually formed in the GALLBLADDER, resulting in the condition of CHOLELITHIASIS. Gallstones, derived from the BILE, consist mainly of calcium, cholesterol, or bilirubin.Cholangitis: Inflammation of the biliary ductal system (BILE DUCTS); intrahepatic, extrahepatic, or both.Pancreatic Diseases: Pathological processes of the PANCREAS.Bile Duct Diseases: Diseases in any part of the ductal system of the BILIARY TRACT from the smallest BILE CANALICULI to the largest COMMON BILE DUCT.Cholangiography: An imaging test of the BILIARY TRACT in which a contrast dye (RADIOPAQUE MEDIA) is injected into the BILE DUCT and x-ray pictures are taken.Jaundice, Obstructive: Jaundice, the condition with yellowish staining of the skin and mucous membranes, that is due to impaired BILE flow in the BILIARY TRACT, such as INTRAHEPATIC CHOLESTASIS, or EXTRAHEPATIC CHOLESTASIS.Cholecystectomy, Laparoscopic: Excision of the gallbladder through an abdominal incision using a laparoscope.Biliary Fistula: Abnormal passage in any organ of the biliary tract or between biliary organs and other organs.Sphincter of Oddi Dysfunction: Organic or functional motility disorder involving the SPHINCTER OF ODDI and associated with biliary COLIC. Pathological changes are most often seen in the COMMON BILE DUCT sphincter, and less commonly the PANCREATIC DUCT sphincter.Ampulla of Vater: A dilation of the duodenal papilla that is the opening of the juncture of the COMMON BILE DUCT and the MAIN PANCREATIC DUCT, also known as the hepatopancreatic ampulla.Cholestasis: Impairment of bile flow due to obstruction in small bile ducts (INTRAHEPATIC CHOLESTASIS) or obstruction in large bile ducts (EXTRAHEPATIC CHOLESTASIS).Cholestasis, Extrahepatic: Impairment of bile flow in the large BILE DUCTS by mechanical obstruction or stricture due to benign or malignant processes.Sphincter of Oddi: The sphincter of the hepatopancreatic ampulla within the duodenal papilla. The COMMON BILE DUCT and main pancreatic duct pass through this sphincter.Choledochal Cyst: A congenital anatomic malformation of a bile duct, including cystic dilatation of the extrahepatic bile duct or the large intrahepatic bile duct. Classification is based on the site and type of dilatation. Type I is most common.Choledochostomy: Surgical formation of an opening (stoma) into the COMMON BILE DUCT for drainage or for direct communication with a site in the small intestine, primarily the DUODENUM or JEJUNUM.Cholelithiasis: Presence or formation of GALLSTONES in the BILIARY TRACT, usually in the gallbladder (CHOLECYSTOLITHIASIS) or the common bile duct (CHOLEDOCHOLITHIASIS).Bile Ducts: The channels that collect and transport the bile secretion from the BILE CANALICULI, the smallest branch of the BILIARY TRACT in the LIVER, through the bile ductules, the bile ducts out the liver, and to the GALLBLADDER for storage.Endosonography: Ultrasonography of internal organs using an ultrasound transducer sometimes mounted on a fiberoptic endoscope. In endosonography the transducer converts electronic signals into acoustic pulses or continuous waves and acts also as a receiver to detect reflected pulses from within the organ. An audiovisual-electronic interface converts the detected or processed echo signals, which pass through the electronics of the instrument, into a form that the technologist can evaluate. The procedure should not be confused with ENDOSCOPY which employs a special instrument called an endoscope. The "endo-" of endosonography refers to the examination of tissue within hollow organs, with reference to the usual ultrasonography procedure which is performed externally or transcutaneously.Cholecystectomy: Surgical removal of the GALLBLADDER.Gabexate: A serine proteinase inhibitor used therapeutically in the treatment of pancreatitis, disseminated intravascular coagulation (DIC), and as a regional anticoagulant for hemodialysis. The drug inhibits the hydrolytic effects of thrombin, plasmin, and kallikrein, but not of chymotrypsin and aprotinin.Postcholecystectomy Syndrome: Abdominal symptoms after removal of the GALLBLADDER. The common postoperative symptoms are often the same as those present before the operation, such as COLIC, bloating, NAUSEA, and VOMITING. There is pain on palpation of the right upper quadrant and sometimes JAUNDICE. The term is often used, inaccurately, to describe such postoperative symptoms not due to gallbladder removal.Drainage: The removal of fluids or discharges from the body, such as from a wound, sore, or cavity.Cystic Duct: The duct that is connected to the GALLBLADDER and allows the emptying of bile into the COMMON BILE DUCT.Endoscopes, Gastrointestinal: Instruments for the visual examination of the interior of the gastrointestinal tract.Common Bile Duct Neoplasms: Tumor or cancer of the COMMON BILE DUCT including the AMPULLA OF VATER and the SPHINCTER OF ODDI.Double-Balloon Enteroscopy: Endoscopy of the small intestines accomplished while advancing the endoscope into the intestines from the stomach by alternating the inflation of two balloons, one on an innertube of the endoscope and the other on an overtube.Gallbladder Diseases: Diseases of the GALLBLADDER. They generally involve the impairment of BILE flow, GALLSTONES in the BILIARY TRACT, infections, neoplasms, or other diseases.Biliary Tract: The BILE DUCTS and the GALLBLADDER.Bile Duct Neoplasms: Tumors or cancer of the BILE DUCTS.Mirizzi Syndrome: Complication of CHOLELITHIASIS characterized by OBSTRUCTIVE JAUNDICE; abdominal pain, and fever.Pancreatitis, Chronic: INFLAMMATION of the PANCREAS that is characterized by recurring or persistent ABDOMINAL PAIN with or without STEATORRHEA or DIABETES MELLITUS. It is characterized by the irregular destruction of the pancreatic parenchyma which may be focal, segmental, or diffuse.Hepatic Duct, Common: Predominantly extrahepatic bile duct which is formed by the junction of the right and left hepatic ducts, which are predominantly intrahepatic, and, in turn, joins the cystic duct to form the common bile duct.Endoscopy: Procedures of applying ENDOSCOPES for disease diagnosis and treatment. Endoscopy involves passing an optical instrument through a small incision in the skin i.e., percutaneous; or through a natural orifice and along natural body pathways such as the digestive tract; and/or through an incision in the wall of a tubular structure or organ, i.e. transluminal, to examine or perform surgery on the interior parts of the body.Pancreatic Neoplasms: Tumors or cancer of the PANCREAS. Depending on the types of ISLET CELLS present in the tumors, various hormones can be secreted: GLUCAGON from PANCREATIC ALPHA CELLS; INSULIN from PANCREATIC BETA CELLS; and SOMATOSTATIN from the SOMATOSTATIN-SECRETING CELLS. Most are malignant except the insulin-producing tumors (INSULINOMA).Gastroenterology: A subspecialty of internal medicine concerned with the study of the physiology and diseases of the digestive system and related structures (esophagus, liver, gallbladder, and pancreas).Constriction, Pathologic: The condition of an anatomical structure's being constricted beyond normal dimensions.Pancreatic Pseudocyst: Cyst-like space not lined by EPITHELIUM and contained within the PANCREAS. Pancreatic pseudocysts account for most of the cystic collections in the pancreas and are often associated with chronic PANCREATITIS.Amylases: A group of amylolytic enzymes that cleave starch, glycogen, and related alpha-1,4-glucans. (Stedman, 25th ed) EC 3.2.1.-.Pancreas: A nodular organ in the ABDOMEN that contains a mixture of ENDOCRINE GLANDS and EXOCRINE GLANDS. The small endocrine portion consists of the ISLETS OF LANGERHANS secreting a number of hormones into the blood stream. The large exocrine portion (EXOCRINE PANCREAS) is a compound acinar gland that secretes several digestive enzymes into the pancreatic ductal system that empties into the DUODENUM.Jaundice: A clinical manifestation of HYPERBILIRUBINEMIA, characterized by the yellowish staining of the SKIN; MUCOUS MEMBRANE; and SCLERA. Clinical jaundice usually is a sign of LIVER dysfunction.Anastomosis, Roux-en-Y: A Y-shaped surgical anastomosis of any part of the digestive system which includes the small intestine as the eventual drainage site.Catheterization: Use or insertion of a tubular device into a duct, blood vessel, hollow organ, or body cavity for injecting or withdrawing fluids for diagnostic or therapeutic purposes. It differs from INTUBATION in that the tube here is used to restore or maintain patency in obstructions.Lithiasis: A condition characterized by the formation of CALCULI and concretions in the hollow organs or ducts of the body. They occur most often in the gallbladder, kidney, and lower urinary tract.Biliary Tract Surgical Procedures: Any surgical procedure performed on the biliary tract.Endoscopy, Digestive System: Endoscopic examination, therapy or surgery of the digestive tract.Retrospective Studies: Studies used to test etiologic hypotheses in which inferences about an exposure to putative causal factors are derived from data relating to characteristics of persons under study or to events or experiences in their past. The essential feature is that some of the persons under study have the disease or outcome of interest and their characteristics are compared with those of unaffected persons.Biliary Tract Neoplasms: Tumors or cancer in the BILIARY TRACT including the BILE DUCTS and the GALLBLADDER.Bile Ducts, Intrahepatic: Passages within the liver for the conveyance of bile. Includes right and left hepatic ducts even though these may join outside the liver to form the common hepatic duct.Gallbladder Neoplasms: Tumors or cancer of the gallbladder.Technetium Tc 99m Lidofenin: A nontoxic radiopharmaceutical that is used in RADIONUCLIDE IMAGING for the clinical evaluation of hepatobiliary disorders in humans.Duodenal Diseases: Pathological conditions in the DUODENUM region of the small intestine (INTESTINE, SMALL).Jejunostomy: Surgical formation of an opening through the ABDOMINAL WALL into the JEJUNUM, usually for enteral hyperalimentation.Adenomyoma: A benign neoplasm of muscle (usually smooth muscle) with glandular elements. It occurs most frequently in the uterus and uterine ligaments. (Stedman, 25th ed)Biliary Dyskinesia: A motility disorder characterized by biliary COLIC, absence of GALLSTONES, and an abnormal GALLBLADDER ejection fraction. It is caused by gallbladder dyskinesia and/or SPHINCTER OF ODDI DYSFUNCTION.Cholangiocarcinoma: A malignant tumor arising from the epithelium of the BILE DUCTS.Calculi: An abnormal concretion occurring mostly in the urinary and biliary tracts, usually composed of mineral salts. Also called stones.Endoscopes: Instruments for the visual examination of interior structures of the body. There are rigid endoscopes and flexible fiberoptic endoscopes for various types of viewing in ENDOSCOPY.Duodenoscopy: Endoscopic examination, therapy or surgery of the luminal surface of the duodenum.Treatment Outcome: Evaluation undertaken to assess the results or consequences of management and procedures used in combating disease in order to determine the efficacy, effectiveness, safety, and practicability of these interventions in individual cases or series.Insufflation: The act of blowing a powder, vapor, or gas into any body cavity for experimental, diagnostic, or therapeutic purposes.Digestive System Diseases: Diseases in any part of the GASTROINTESTINAL TRACT or the accessory organs (LIVER; BILIARY TRACT; PANCREAS).Abdominal Pain: Sensation of discomfort, distress, or agony in the abdominal region.Pancreatic Fistula: Abnormal passage communicating with the PANCREAS.Breath Holding: An involuntary or voluntary pause in breathing, sometimes accompanied by loss of consciousness.Tomography, X-Ray Computed: Tomography using x-ray transmission and a computer algorithm to reconstruct the image.Deep Sedation: Drug-induced depression of consciousness during which patients cannot be easily aroused but respond purposely following repeated painful stimulation. The ability to independently maintain ventilatory function may be impaired. (From: American Society of Anesthesiologists Practice Guidelines)Acute Disease: Disease having a short and relatively severe course.Butylscopolammonium Bromide: Antimuscarinic quaternary ammonium derivative of scopolamine used to treat cramps in gastrointestinal, urinary, uterine, and biliary tracts, and to facilitate radiologic visualization of the gastrointestinal tract.Stents: Devices that provide support for tubular structures that are being anastomosed or for body cavities during skin grafting.Neoplasms, Cystic, Mucinous, and Serous: Neoplasms containing cyst-like formations or producing mucin or serum.Cholangitis, Sclerosing: Chronic inflammatory disease of the BILIARY TRACT. It is characterized by fibrosis and hardening of the intrahepatic and extrahepatic biliary ductal systems leading to bile duct strictures, CHOLESTASIS, and eventual BILIARY CIRRHOSIS.Pancreatic Function Tests: Tests based on the biochemistry and physiology of the exocrine pancreas and involving analysis of blood, duodenal contents, feces, or urine for products of pancreatic secretion.Adenocarcinoma, Papillary: An adenocarcinoma containing finger-like processes of vascular connective tissue covered by neoplastic epithelium, projecting into cysts or the cavity of glands or follicles. It occurs most frequently in the ovary and thyroid gland. (Stedman, 25th ed)Cholecystolithiasis: Presence or formation of GALLSTONES in the GALLBLADDER.Postoperative Complications: Pathologic processes that affect patients after a surgical procedure. They may or may not be related to the disease for which the surgery was done, and they may or may not be direct results of the surgery.Colic: A clinical syndrome with intermittent abdominal pain characterized by sudden onset and cessation that is commonly seen in infants. It is usually associated with obstruction of the INTESTINES; of the CYSTIC DUCT; or of the URINARY TRACT.Cholecystitis: Inflammation of the GALLBLADDER; generally caused by impairment of BILE flow, GALLSTONES in the BILIARY TRACT, infections, or other diseases.Cystadenoma, Papillary: A benign neoplasm of the ovary.Hemobilia: Hemorrhage in or through the BILIARY TRACT due to trauma, inflammation, CHOLELITHIASIS, vascular disease, or neoplasms.Pancreaticoduodenectomy: The excision of the head of the pancreas and the encircling loop of the duodenum to which it is connected.Biliary Atresia: Progressive destruction or the absence of all or part of the extrahepatic BILE DUCTS, resulting in the complete obstruction of BILE flow. Usually, biliary atresia is found in infants and accounts for one third of the neonatal cholestatic JAUNDICE.Cholecystitis, Acute: Acute inflammation of the GALLBLADDER wall. It is characterized by the presence of ABDOMINAL PAIN; FEVER; and LEUKOCYTOSIS. Gallstone obstruction of the CYSTIC DUCT is present in approximately 90% of the cases.Duodenum: The shortest and widest portion of the SMALL INTESTINE adjacent to the PYLORUS of the STOMACH. It is named for having the length equal to about the width of 12 fingers.Bile Ducts, Extrahepatic: Passages external to the liver for the conveyance of bile. These include the COMMON BILE DUCT and the common hepatic duct (HEPATIC DUCT, COMMON).Pancreatic Cyst: A true cyst of the PANCREAS, distinguished from the much more common PANCREATIC PSEUDOCYST by possessing a lining of mucous EPITHELIUM. Pancreatic cysts are categorized as congenital, retention, neoplastic, parasitic, enterogenous, or dermoid. Congenital cysts occur more frequently as solitary cysts but may be multiple. Retention cysts are gross enlargements of PANCREATIC DUCTS secondary to ductal obstruction. (From Bockus Gastroenterology, 4th ed, p4145)Mesocolon: The fold of peritoneum by which the COLON is attached to the posterior ABDOMINAL WALL.Lithotripsy: The destruction of a calculus of the kidney, ureter, bladder, or gallbladder by physical forces, including crushing with a lithotriptor through a catheter. Focused percutaneous ultrasound and focused hydraulic shock waves may be used without surgery. Lithotripsy does not include the dissolving of stones by acids or litholysis. Lithotripsy by laser is LITHOTRIPSY, LASER.Administration, Rectal: The insertion of drugs into the rectum, usually for confused or incompetent patients, like children, infants, and the very old or comatose.Pleural DiseasesPreoperative Care: Care given during the period prior to undergoing surgery when psychological and physical preparations are made according to the special needs of the individual patient. This period spans the time between admission to the hospital to the time the surgery begins. (From Dictionary of Health Services Management, 2d ed)Radiation Monitoring: The observation, either continuously or at intervals, of the levels of radiation in a given area, generally for the purpose of assuring that they have not exceeded prescribed amounts or, in case of radiation already present in the area, assuring that the levels have returned to those meeting acceptable safety standards.Dilatation, Pathologic: The condition of an anatomical structure's being dilated beyond normal dimensions.Diverticulum: A pouch or sac developed from a tubular or saccular organ, such as the GASTROINTESTINAL TRACT.Ultrasonography: The visualization of deep structures of the body by recording the reflections or echoes of ultrasonic pulses directed into the tissues. Use of ultrasound for imaging or diagnostic purposes employs frequencies ranging from 1.6 to 10 megahertz.Conscious Sedation: A drug-induced depression of consciousness during which patients respond purposefully to verbal commands, either alone or accompanied by light tactile stimulation. No interventions are required to maintain a patent airway. (From: American Society of Anesthesiologists Practice Guidelines)Bile: An emulsifying agent produced in the LIVER and secreted into the DUODENUM. Its composition includes BILE ACIDS AND SALTS; CHOLESTEROL; and ELECTROLYTES. It aids DIGESTION of fats in the duodenum.Prospective Studies: Observation of a population for a sufficient number of persons over a sufficient number of years to generate incidence or mortality rates subsequent to the selection of the study group.Carcinoma, Pancreatic Ductal: Carcinoma that arises from the PANCREATIC DUCTS. It accounts for the majority of cancers derived from the PANCREAS.Gallbladder: A storage reservoir for BILE secretion. Gallbladder allows the delivery of bile acids at a high concentration and in a controlled manner, via the CYSTIC DUCT to the DUODENUM, for degradation of dietary lipid.Bile Reflux: Retrograde bile flow. Reflux of bile can be from the duodenum to the stomach (DUODENOGASTRIC REFLUX); to the esophagus (GASTROESOPHAGEAL REFLUX); or to the PANCREAS.Intraoperative Period: The period during a surgical operation.Trypsinogen: The inactive proenzyme of trypsin secreted by the pancreas, activated in the duodenum via cleavage by enteropeptidase. (Stedman, 25th ed)Pancreatectomy: Surgical removal of the pancreas. (Dorland, 28th ed)Adenocarcinoma, Mucinous: An adenocarcinoma producing mucin in significant amounts. (From Dorland, 27th ed)Intraoperative Complications: Complications that affect patients during surgery. They may or may not be associated with the disease for which the surgery is done, or within the same surgical procedure.Liver Function Tests: Blood tests that are used to evaluate how well a patient's liver is working and also to help diagnose liver conditions.Magnetic Resonance Imaging: Non-invasive method of demonstrating internal anatomy based on the principle that atomic nuclei in a strong magnetic field absorb pulses of radiofrequency energy and emit them as radiowaves which can be reconstructed into computerized images. The concept includes proton spin tomographic techniques.Secretin: A peptide hormone of about 27 amino acids from the duodenal mucosa that activates pancreatic secretion and lowers the blood sugar level. (USAN and the USP Dictionary of Drug Names, 1994, p597)Liver Transplantation: The transference of a part of or an entire liver from one human or animal to another.Sensitivity and Specificity: Binary classification measures to assess test results. Sensitivity or recall rate is the proportion of true positives. Specificity is the probability of correctly determining the absence of a condition. (From Last, Dictionary of Epidemiology, 2d ed)Contrast Media: Substances used to allow enhanced visualization of tissues.Endoscopy, Gastrointestinal: Endoscopic examination, therapy or surgery of the gastrointestinal tract.Pancreatitis, Acute Necrotizing: A severe form of acute INFLAMMATION of the PANCREAS characterized by one or more areas of NECROSIS in the pancreas with varying degree of involvement of the surrounding tissues or organ systems. Massive pancreatic necrosis may lead to DIABETES MELLITUS, and malabsorption.Diagnostic Imaging: Any visual display of structural or functional patterns of organs or tissues for diagnostic evaluation. It includes measuring physiologic and metabolic responses to physical and chemical stimuli, as well as ultramicroscopy.Predictive Value of Tests: In screening and diagnostic tests, the probability that a person with a positive test is a true positive (i.e., has the disease), is referred to as the predictive value of a positive test; whereas, the predictive value of a negative test is the probability that the person with a negative test does not have the disease. Predictive value is related to the sensitivity and specificity of the test.Intraoperative Care: Patient care procedures performed during the operation that are ancillary to the actual surgery. It includes monitoring, fluid therapy, medication, transfusion, anesthesia, radiography, and laboratory tests.Chronic Disease: Diseases which have one or more of the following characteristics: they are permanent, leave residual disability, are caused by nonreversible pathological alteration, require special training of the patient for rehabilitation, or may be expected to require a long period of supervision, observation, or care. (Dictionary of Health Services Management, 2d ed)Length of Stay: The period of confinement of a patient to a hospital or other health facility.Liver Diseases: Pathological processes of the LIVER.Patient Selection: Criteria and standards used for the determination of the appropriateness of the inclusion of patients with specific conditions in proposed treatment plans and the criteria used for the inclusion of subjects in various clinical trials and other research protocols.Chi-Square Distribution: A distribution in which a variable is distributed like the sum of the squares of any given independent random variable, each of which has a normal distribution with mean of zero and variance of one. The chi-square test is a statistical test based on comparison of a test statistic to a chi-square distribution. The oldest of these tests are used to detect whether two or more population distributions differ from one another.Follow-Up Studies: Studies in which individuals or populations are followed to assess the outcome of exposures, procedures, or effects of a characteristic, e.g., occurrence of disease.Time Factors: Elements of limited time intervals, contributing to particular results or situations.Palliative Care: Care alleviating symptoms without curing the underlying disease. (Stedman, 25th ed)Laparoscopy: A procedure in which a laparoscope (LAPAROSCOPES) is inserted through a small incision near the navel to examine the abdominal and pelvic organs in the PERITONEAL CAVITY. If appropriate, biopsy or surgery can be performed during laparoscopy.Anastomosis, Surgical: Surgical union or shunt between ducts, tubes or vessels. It may be end-to-end, end-to-side, side-to-end, or side-to-side.Portal Vein: A short thick vein formed by union of the superior mesenteric vein and the splenic vein.Recurrence: The return of a sign, symptom, or disease after a remission.Lipase: An enzyme of the hydrolase class that catalyzes the reaction of triacylglycerol and water to yield diacylglycerol and a fatty acid anion. It is produced by glands on the tongue and by the pancreas and initiates the digestion of dietary fats. (From Dorland, 27th ed) EC Factors: An aspect of personal behavior or lifestyle, environmental exposure, or inborn or inherited characteristic, which, on the basis of epidemiologic evidence, is known to be associated with a health-related condition considered important to prevent.