Year : 2014 | Volume
: 3 | Issue : 2 | Page : 57--59
Nutritional considerations in modern radiology
Vikas Chaudhary1, Shahina Bano2,
1 Department of Radiodiagnosis, Employees' State Insurance Corporation Model Hospital, Gurgaon, Haryana, India
2 Lady Hardinge Medical College and Associated Smt. Sucheta Kriplani and Kalawati Hospitals, New Delhi, India
Department of Radiodiagnosis, Employees«SQ» State Insurance Corporation Model Hospital, Gurgaon 122 001, Haryana
There have been many nutritional aspects in diagnostic radiology, which have always been of interest to the clinicians as well as to the patients. Some of the important nutrition-related aspects in radiological investigations are discussed here.
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Chaudhary V, Bano S. Nutritional considerations in modern radiology.J Med Nutr Nutraceut 2014;3:57-59
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Chaudhary V, Bano S. Nutritional considerations in modern radiology. J Med Nutr Nutraceut [serial online] 2014 [cited 2022 May 17 ];3:57-59
Available from: https://www.jmnn.org/text.asp?2014/3/2/57/131953
Radiology is a branch of medicine that uses imaging technology to diagnose and treat the diseases. Various imaging modalities used in radiology include X-ray radiography, ultrasound, computed tomography (CT), magnetic resonance imaging (MRI), and nuclear medicine. In this article, we shall discuss some important nutritional considerations relevant in modern radiology.
Adequate Hydration Before and After Intravenous Contrast
Although iodinated contrast agents used in modern radiology are considered safe, adverse events may occur with them. The nephrotoxic potential of iodinated contrast media is widely accepted in the medical literature. Contrast agent-induced nephropathy (CIN) is the third most common cause of all hospital-acquired acute renal failure and is associated with high morbidity and mortality. The risk of CIN increases in patients with pre-existing renal failure, diabetes, or dehydration.  For those at high risk (eGFR <30 mL/min/1.73 m 2 ) of developing CIN, contrast administration should be avoided and alternative diagnostic examination should be considered. For patients with intermediate (eGFR 30-60 mL/min/1.73 m 2 ) and low (eGFR >60 mL/min/1.73 m 2 ) risk, various prophylactic measures can be taken to minimize the risk of CIN. The most effective and the simplest measure to protect renal function is adequate hydration.  All patients should be encouraged to have adequate hydration. Outpatients should be advised to start hydration on the day prior to the imaging study. Inpatients should receive intravenous 0.9% normal saline infused at rate of 1 mL/kg for 12 hours before and after the contrast exposure.  Recently, the use of sodium bicarbonate for hydration, as compared with sodium chloride (normal saline), has been suggested as being an effective (and probably more superior) and safe alternative in decreasing the incidence of CIN.  This approach is also appealing because of its low cost and relative ease of use. 
Need for Nil Per Oral (NPO) Before Radiologic Procedures
For radiographic studies like X-ray abdomen/KUB/barium procedures, patient should be NPO (nothing by mouth) after midnight or 4 to 6 hours prior to the procedure to ensure an empty stomach and intestine.
For abdominal sonography, patients should be NPO after midnight or 4 to 6 hours prior to the procedure, and should have no fatty foods for 12 hours prior to the gallbladder sonogram. If possible, gas-producing foods such as beans and carbonated beverages should better be avoided for 24 hours before the examination. Further, there will be less bowel gas if patients refrain from smoking and chewing gum for 12 hours. Patients on medication may take it with a small amount of water. Insulin-dependent diabetics should take their insulin with dry toast and juice in the morning of the scheduled day of ultrasound examination. Children (≤12 years of age) should avoid eating or drinking for 4 hours prior to the abdominal ultrasound. In case of infants, feeding should be stopped 2 hours prior to the examination time.
However, if only dedicated pelvic or obstetric ultrasound is needed, patients may be allowed to eat.
Generally, there is no fasting requirement prior to a non-contrast CT scan. However, the patient should be NPO after midnight or 4 to 6 hours prior to the procedure, and may only drink water prior to the procedure if intravenous contrast is to be used. This is usually done to avoid contrast-induced nausea and vomiting. All patients should be encouraged to drink lots of fluids for several hours after receiving contrast material.
For MRI, generally patient does not need to be NPO. Only patients who receive sedation or anesthesia during the procedure need to be NPO.
For nuclear medicine procedures, patients should be NPO after midnight or 4 to 6 hours prior to the procedure.
Drinking Water Before Abdominal/Pelvic Ultrasound
Drinking water before ultrasound examination of the abdomen/pelvis allows adequate distension of the stomach and urinary bladder and provides a transonic window for scanning the structures in the stomach bed (such as pancreas) and pelvis (such as uterus/ovaries and prostate/seminal vesicles).
For pancreatic ultrasound, the patient is asked to drink ˜300 ml (i.e., ˜10 ounces) water bolus so that water distension of stomach and duodenum can be achieved. A straw can be used for drinking water to minimize the swallowed air. 
For general abdominal/retroperitoneal (viz. for kidneys) ultrasound, patients are asked to drink ˜600 ml (i.e., ˜20 ounces) of water one hour prior to the examination time.
For pediatric/male pelvic sonography, patients should drink at least ˜600 ml (i.e., ˜20 ounces) of water one hour before the scheduled time.
For female pelvic ultrasound, the patient should slowly drink ˜1 liter (i.e., ˜32 ounces) of water and should finish the drinking at least one hour before the examination. The patient should particularly be advised to drink the water slowly to prevent abdominal discomfort and to keep the swallowed air to a minimum.
In case of exclusively breast-fed infants suspected of having hypertrophic pyloric stenosis, the stomach can be filled with gas (particularly in the crying babies), thereby making the ultrasound examination of the pylorus very difficult. In these cases, the mother can be asked to feed her infant. This will help to calm the infant (thereby decreasing air swallowing) and will replace the stomach gas, consequently providing good acoustic window.
Fruit Juice/Glucose Water Mixed with Oral Contrast for Opacification of Gastrointestinal Tract During Ct Scanning of the Abdomen
CT scanning using oral contrast allows excellent visualization of both small and large bowels, and also helps to differentiate the bowel from lymph nodes.
Mixing of the flavoring agents like fruit juice or glucose water with oral contrast (e.g., Gastrografin) makes the contrast more palatable (pleasant to taste).
Iron Syrup/Pineapple (Or Blueberry) Juice for Mrcp
Magnetic resonance cholangiopancreatography (MRCP) is a non-invasive imaging technique that allows evaluation of the pancreaticobiliary system. It uses heavily T 2 -weighted (T2W) sequences to take advantage of the inherent contrast effect of bile. Overlap between high signals from the pancreaticobiliary system and from the gastrointestinal tract (stomach, duodenum, and proximal intestine) is a recognized limitation of MRCP and may mimic pathology. Elimination of the high signal from the bowel is, therefore, important. This problem may in part be overcome by multiple acquisitions of the same sequence in multiple planes, or alternatively by using a negative oral contrast agent to shorten the T 2 relaxation time, and hence reducing the T 2 signal of the fluid in the bowel. Several studies have shown that the administration of a negative oral contrast material, before performing MRCP, will improve image quality and provide good visualization of the biliary and pancreatic ducts without superimposed high signal from the GIT. Examples of negative oral contrast agents available are gadopentate dimeglumine, ferric ammonium citrate, antacid, barium sulfate, and ferric particles. Many of these are relatively unpalatable, become too diluted in the GIT, or are expensive.  Pineapple and blueberry juices are naturally occurring relatively inexpensive drinks that at appropriate concentrations have been shown to be effective, well tolerated negative oral contrast agents for suppressing the signal from stomach and duodenum on T2W imaging in MRCP. These juices reduce the intraluminal signal of the GIT on T2W imaging due to the paramagnetic properties of its relatively high manganese content reducing the T 2 recovery times. Therefore, pineapple (or blueberry) juice may act as an effective negative contrast agent for MRCP. ,
Conventional Defecography Using Barium with Mashed Potato
Evacuation disorders, frequently found in elderly patients, are often caused by morphologic and functional abnormalities of the anorectal region and the pelvic floor. Defecography (also called evacuation proctography) evaluates in real time the morphology of rectum and anal canal in correlation with pelvic bony components both statically and dynamically by injection of a thick barium paste (about 300 ml of barium paste obtained by mixing equal proportion of potato starch and barium suspension with water) into the rectum and its subsequent evacuation. The most common indications include constipation, incomplete evacuation or incontinence, rectal prolapse, solitary rectal ulcer, rectocele, sigmoidocele, enterocele, intussusception, descending pelvic floor syndrome, puborectalis muscle syndrome, and perineal pain or discomfort. The technique is also important for follow-up of patients who have undergone surgery of the pelvic region. Conventional video defecography is the gold standard examination for the identification and staging of morphological and functional disorders of the recto-anal region and pelvic floor in evacuation dysfunctions. Recently, MR defecography has been of increasing interest because of its accuracy in morphologic and functional assessment, with additional benefit of avoiding radiation exposure to the patient. For MR defecography, ˜240 ml of aqueous ultrasound gel is instilled into the rectum through a small rectal catheter with the patient in right decubitus position. Open configuration MR systems are required to perform the study with the patient in sitting position. Unfortunately, open configuration MR systems are expensive and less available. ,
Fatty Meal for Gb Function
Usefulness of fatty meal-stimulated oral cholecystography for the evaluation of gallbladder function is well documented in radiology. A high-fat liquid (e.g., a glass of full fat milk) given just prior to the examination causes the gallbladder to contract and release some bile. Gall bladder contraction is evaluated under fluoroscope and X-ray images (coned-low kV films) taken at timed intervals. Non-visualization of gall bladder suggests cystic duct obstruction and a non-functioning gall bladder. The test was used to diagnose disorders of the liver and gallbladder. Now, ultrasonography has largely replaced the fatty meal-stimulated oral cholecystography for assessment of gall bladder anatomy and function. Gallbladder radionuclide scan [hepatobiliary iminodiacetic acid (HIDA) scan] may also be used to evaluate gallbladder function. 
All medical practitioners, radiologists, and radiographers must be aware of these facts.
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