Читать книгу Veterinary Surgical Oncology - Группа авторов - Страница 61

Contrast agents are required components of most intravascular (IV) procedures and many stenting procedures. The predominant contrast agents used for angiography include iodinated agents (fluoroscopy, CT), gadolinium‐based agents (MRI), and carbon dioxide (CT) (Ehrmann et al. 1994; Moresco et al. 2000; Spinosa et al. 2000, 2001; Brown et al. 2003; Namasivayam et al. 2006; Bui et al. 2007). Iodinated contrast agents are available in both ionic and nonionic forms; nonionic agents are less osmolar than their ionic counterparts (Singh and Daftary 2008). Severe reactions are reported to occur with similar incidence among all iodinated contrast agents, but mild and moderate contrast reactions occur more commonly with the use of higher osmolality iodinated contrast agents (Singh and Daftary 2008). Nephrotoxicity is a major potential complication associated with the use of iodinated contrast agents and has become the third most common cause of acute renal failure in humans (Akgun et al. 2006). The most commonly used iodinated contrast agents are the nonionic monomers such as iohexol, iopromide, iopamidol, and ioversol (Dickinson and Kam 2008).

Gadolinium‐based contrast agents and CO₂ are used most commonly in patients who have had a previous adverse reaction to an iodinated contrast agent and in those patients with an increased risk for development of nephrotoxicity (Moresco et al. 2000; Spinosa et al. 2000, 2001; Dickinson and Kam 2008), although some studies have reported nephrotoxicity in association with gadolinium contrast usage (Akgun et al. 2006; Ergün et al. 2006). Agents such as gadopentetate dimeglumine, gadodiamide, gadoteridol, and gadoversetamide are the most readily available gadolinium‐based contrast agents (Akgun et al. 2006) and are used when previous CO₂ usage has resulted in a suboptimal study due to bowel gas artifacts or as a supplement to CO₂ angiography (Spinosa et al. 2000, 2001). Gadolinium‐based contrast agents produce less detailed contrast studies as compared with iodinated agents and are therefore less useful for angiography during IR procedures (Spinosa et al. 2000). When using gadolinium‐based contrast agents, digital subtraction angiography is recommended to compensate for the less detailed study that is otherwise obtained (Spinosa et al. 2000).

To outline a hollow viscus such as the esophagus, urethra, and colon, substances such as barium and iodinated contrast agents have been used in veterinary patients (Hume et al. 2006; Weisse et al. 2006; Farese et al. 2008). In a recent study of esophageal tumors in dogs, barium sulfate was found to be useful in identifying mass location (Farese et al. 2008). In dogs, iodinated contrast agents have been used to evaluate urethral obstructions prior to urethral stenting (Weisse et al. 2006). Additionally, iodinated contrast agents have been used prior to colonic and esophageal stenting to delineate obstructions (Hume et al. 2006; Hansen et al. 2012).