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Implantable Cardiac Devices

Background The most common implantable cardiac devices are permanent pacemakers (PPMs) and implantable cardioverter defibrillators (ICD). PPM is placed in a patient with complete heart block or sinus node dysfunction leading to bradycardia. It takes over the “timekeeping” function of the sinoatrial node (located in the right atrium) and provides the necessary electrical impulses to maintain a normal heart rate. ICD is placed in a patient…

Hepatobiliary Scintigraphy

Background Hepatobiliary scintigraphy (hepatobiliary iminodiacetic acid or HIDA) is a noninvasive nuclear imaging test used to assess the patency of the extrahepatic biliary tree and gallbladder and the functionality of the liver and gallbladder. Radioactive tracer is injected into the bloodstream and transported to the liver where it is taken up and excreted into the biliary tree. The tracer is then taken up by the gallbladder…

Hemodialysis Access

Background There are several means of vascular access through which hemodialysis (HD) can be performed, including catheters, arteriovenous fistulas (AVFs), and arteriovenous grafts (AVGs). These accesses provide the means for large-bore cannulas to be placed, usually in both an artery and a vein, thus facilitating a large volume of blood to exit and return to the patient after passing through a dialysis machine. HD access catheters…

Hemodialysis

Background Hemodialysis (HD) is the process by which the solute composition of a solution (blood) is altered by exposing the solution to a second solution (dialysate) through a semipermeable membrane. Low-molecular-weight solutes easily interchange between the two solutions down a concentration gradient, but high-molecular-weight solutes will remain on either side of the membrane unchanged. Solutes pass through the membrane via two different mechanisms: diffusion and convection…

Gastrointestinal Endoscopy – Upper

Background Esophagogastroduodenoscopy (EGD) is a procedure that enables visualization and interaction with the upper gastrointestinal (GI) tract. It is called EGD because it uses a “scope” (an instrument for viewing; e.g., microscope, telescope) to access the esophagus (the “E”), stomach (gastric – the “G”), and duodenum (the “D”). It is also referred to as an upper endoscopy. EGD is one of the most common procedures performed…

Gastrointestinal Endoscopy – Lower

Background Colonoscopy is an endoscopic technique used to visualize the colon for screening, diagnostic, and therapeutic purposes. A sigmoidoscopy allows for visualization of the distal part of the large intestine between the descending colon and rectum. The suffix “-scopy” is derived from “skopía” meaning “to view.” Phillip Bozzini, an early 19th-century German physician, was the first to introduce a primitive scope (“Lichtleiter” or light conductor) to…

Gastrointestinal Endoscopy – Capsule

Background Capsule endoscopy (CE) is a noninvasive test that was originally developed to visualize abnormalities of the small intestine but may now be used to diagnose and monitor various disease processes throughout the entire gastrointestinal (GI) tract. The word “endoscopy” is derived from the Greek by combining the prefix “endo” meaning “within” and the verb “skopía” meaning “to view.” The discovery of CE technology dates to…

Gastric Emptying Study

Background Gastric emptying study (GES) is a noninvasive nuclear medicine test used to evaluate patients with suspected gastric motility disorders. As its name suggests, it is used to determine the amount of time required for the stomach to empty after a meal. The first GES to evaluate gastric motility was described in 1966 by Dr. G.H. Griffith and colleagues and consisted of “a standard breakfast of…

Endoscopic Retrograde Cholangiopancreatography

Background Endoscopic retrograde cholangiopancreatography (ERCP) is an invasive test used to visualize the common bile duct (CBD) and pancreatic duct for diagnostic and therapeutic purposes in a variety of biliary and pancreatic disorders. The term endoscopic is derived from Greek by combining the prefix “endo” (within) and “scope” (to view). The term cholangiopancreatography is also derived from Greek by combining “chole” (bile), “angio” (vessel), “pancreato” (pancreas),…

Electroencephalography

Background An electroencephalography is a test to measure the electrical activities of the brain, allowing for the detection of abnormal brain activity. It is often abbreviated as EEG. The suffix “-graphy” (“G”) refers to the presentation of the results found from the electrical (“E”) impulses measured in the brain (encephalo – “E”). You’re Reading a Preview Become a Clinical Tree membership for Full access and enjoy…

Electrocardiography

Background An electrocardiogram (EKG) is a noninvasive test that provides a visual representation of the electrical conduction of the heart. It is called EKG because the test produces a “-gram” (something written or drawn—e.g., telegram, diagram—the “G”) of the electrical (the “E”) conduction through the heart (cardio—the “K” or “C”). The abbreviation ECG can be used interchangeably with the more common EKG, a reflection of the…

Dexamethasone Suppression Test

Background The dexamethasone suppression test (DST), low-dose DST, overnight DST, or 1-mg DST is a dynamic endocrine test in which hormone levels are evaluated based on the principles of biofeedback regulation. , A suppression test, in general, involves giving the patient a substance that would normally cause the inhibition of the release of the hormone. However, due to the excessive amounts of hormone or hyperfunction of…

Culture – Urine

Background Urinary tract infections (UTIs) have been around for as long as humans have had urinary tracts. Hippocrates believed that symptoms were caused by an imbalance of four humors. Ancient treatment regimens in the pre-antibiotic era ranged from bed rest to narcotics, and also included various herbs, enemas, and, in the heroic era of medical treatments, “judicious bleeding.” While medicine has advanced a great deal since…

Culture – Sputum

Background A sputum culture is often a noninvasive and most useful test in the assessment of lower respiratory tract infections. Sputum samples can be useful in other disease states such as certain cancers; however, sampling is predominately useful for infectious diseases. Obtained sputum can be tested and evaluated via Gram stain, microbiologic culture, and sensitivity testing. These procedures are most frequently performed simultaneously and interpreted together…

Culture – Blood

Background Blood culture is the most efficient way of identifying organisms in the blood. For someone who does not have an infection, blood should always be sterile. The most common organisms identified in the blood are bacteria and fungi, and their presence is called bacteremia and fungemia, respectively. Despite their possible presence in the blood, viruses are not typically identified through traditional blood culture technique because…

Coronary Artery Bypass Grafting

Background Cardiovascular disease is the leading cause of death in the United States. An American suffers from a myocardial infarction approximately every 40 seconds. On average, men are 65 years old and women are 72 years old at the time of the first myocardial infarction. The death rate for coronary artery disease (CAD) has decreased by 31.8% over the 10-year period from 2006 to 2016. This…

Continuous Renal Replacement Therapy

Background Continuous renal replacement therapy (CRRT) is commonly used in the intensive care unit (ICU) setting and can consist of continuous venovenous hemodialysis (CVVHD), continuous venovenous hemofiltration (CVVH), or continuous venovenous hemodiafiltration (CVVHDF). Each of these procedures involves the slow passage of blood, continuously (24 hours a day), through a filter to remove various waste products and/or fluid. You’re Reading a Preview Become a Clinical Tree…

Continuous Glucose Monitoring

Background Continuous glucose monitoring devices provide a way for patients to approximate their blood glucose by testing the interstitial fluid via the chemical reaction of fluorescence, every 1 to 5 minutes, with minimal “fingerstick” point-of-care glucose testing. These devices are frequently referred to by the abbreviation “CGMs.” There are two major types of CGMs called “real-time CGMs” or “intermittently scanning CGMs.” The major difference between the…

Computed Tomography Scan

Background A computed tomography (CT) scan is a noninvasive imaging modality that uses rotating X-ray beams and detectors to produce high-quality cross-sectional imaging of anatomic structures. The word “tomography” comes from the words “tomos” meaning “slice” and “graph” meaning “recording,” referring to the cross-sectional image slices recorded with CT imaging. A CT scan may also be referred to as a computerized axial tomography (CAT) scan. You’re…

Chest X-Ray

Background A chest X-ray (CXR) is a noninvasive imaging procedure that uses ionizing radiation to produce a shadow image of the anatomic structures in the thoracic cavity. The term “X-ray” refers to the type of high-energy electromagnetic radiation used in the imaging procedure, which was discovered by the German physicist, Dr. Wilhelm Roentgen. A CXR is also known as a plain chest roentgenogram, a plain (chest)…