Clinical Pancreatology for Practising Gastroenterologists and Surgeons. Группа авторов
the use of early CT imaging [1,5,44]. Despite this, early imaging is performed in 40–70% of cases [45–47]. A predictive model for the diagnosis of AP aimed to decrease the use of imaging was developed using the following predictors: number of prior AP episodes; history of cholelithiasis; no abdominal surgery (prior two months); time elapsed from symptom onset; pain localized to epigastrium; progressively worsening severity; severity level at presentation; and lipase levels five or more times the upper limit of normal [48]. Those with all eight predictors were identified to have AP with a sensitivity of 45%, and a specificity and a positive predictive value of 100% [46]. Studies have shown that early CT imaging does not predict development of pancreatic necrosis, improve clinical outcomes or reduce length of hospital stay [27,45,46,49–52]. Patients with severe AP who do not improve with conservative therapy or have worsening disease, including the development of organ failure, will benefit from CT imaging. Evidence shows that the optimal time to obtain CT imaging is 48–72 hours after presentation [1,53].
Limitations of CT Imaging
CT imaging is associated with multiple risks. While the use of intravenous contrast in assessing the complications and severity of AP is of great value, it is also associated with side effects. Acute reactions associated with the injection of contrast may be minor, intermediate, or severe. Minor reactions include flushing, mild urticaria, nausea, headache, and vomiting. These reactions are self‐limited. Intermediate reactions may involve bronchospasm and hypotension which will respond to therapy. Severe reactions may include laryngeal edema, convulsions, loss of consciousness, cardiac dysrhythmia and/or arrest, and pulmonary edema [54].
Another risk is contrast‐induced induced nephrotoxicity (CIN). CIN is defined by an absolute rise of more than 0.5 mg/dl or 25% in serum creatinine within 48–72 hours of iodinated contrast [55]. However, recent studies have shown that the risk of CIN following contrast is far lower than previously reported, particularly in patients with normal renal function [56]. Nonetheless, patients with a glomerular filtration rate below 30 ml/min, preexisting renal insufficiency (creatinine >1.5 mg/dl), diabetes mellitus, sepsis, and diuretic use have as high as 25% risk of developing CIN [57] and established preventive measures such as fluid hydration may still be recommended [55].
A commonly overlooked risk of CT imaging is ionizing radiation exposure. which can damage cellular DNA and increase the risk of cancer. Approximately 2% of all cancer diagnoses in the United States are a result of ionizing radiation exposure during CT scans imaging, which is likely attributable to the 600‐fold increase in radiation exposure from CT imaging over the past 20 years [58]. Abdominopelvic CT delivers 100 times as much ionizing radiation as conventional radiographic imaging. The mean radiation dose in patients with ANP and severe AP is 31–40 mSv [59,60]. The mean number of abdominal CT scans per patient with AP was reported to be 1.9 (range 1–12) per hospitalization [59]. Those with severe AP undergo a higher number of CT imaging studies during hospitalization and, therefore, receive higher doses of radiation [61].
CT imaging should only be pursued when the results will impact patient management as this will also help reduce unnecessary exposure to ionizing radiation.
Conclusion
The widespread availability and reproducibility of CT have reduced diagnostic error in AP. Early CT imaging is useful only when the clinical diagnosis is in doubt. It can also be used to determine prognosis, although it is not superior to clinical scoring systems. CT imaging is most beneficial in those who fail to improve with conservative therapy after 48–72 hours, and in those who may have persistent fever, nausea, oral feeding intolerance, persistent systemic inflammatory response syndrome, or organ failure to confirm the presence of local complications. CT should be utilized to determine the degree and extent of pancreatic necrosis, as well as the detection of other suspected complications such as venous thrombosis and pseudoaneurysms. Appropriate use of CT and conveying the imaging findings to internists, pancreatologists, gastroenterologists, and surgeons are essential for the multidisciplinary management of patients with AP.
Disclosures
Vikesh Singh is consultant to Orgenesis, Abbvie, Ariel Precision medicine and Akcea Therapeutics.
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