Contrast media procedures

Extravasation of barium sulfate iato the peritoneal cavity through a perforated GI tract can produce serious adverse reactions. When a perforation is suspected, the use of a water-soluble iodinated contrast medium is iadicated. In this case, oral or rectal administration of sodium or meglumine-sodium salts of diatrizoic acid (6) and oral use ofiohexol (11) are the preferred procedures. 

Percutaneous splenoportography has lost its importance. Should a direct procedure be indicated, laparoscopic splenoportography is a possible alternative. Recently, a new technique has been described. (134) The percutaneous splenic puncture is performed using a thin needle under screen control, with the needle directed at the splenic hilus. The pressure of the splenic pulp can be measured directly in order to estimate the portal vein pressure. Contrast medium is injected manually or by a special device. From this depot in the red pulp, the splenic vein, the portal vein and the intrahepatic branches of the portal vein are contrasted within a few seconds, (s. fig. 8.12) Complications resulting from percutaneous splenoportography include afterbleeding from the spleen, bilateral rupture of the spleen, arterial aneurysms and a.v. shunts — these complications are serious in nature, but rare. Contraindications for the procedure should be carefully observed, (s. tab. 8.6)... 

Direct splenoportography is the most informative procedure for visualizing the portal vein system and its collaterals, (s. p. 181) Yet this technique is costly, time-consuming and high-risk. The injection of contrast medium into the spleen is carried out either percu-taneously (sonography-gmded) or, preferably, by laparoscopy. It is also possible to measure the pressure in the portal vein system. In addition, this method ensures access to the collaterals if radiological obliteration is planned, (s. p. 181)... 

The radiographic detection or monitoring of oesophageal varices using contrast medium is only carried out in rare cases (after immobilizing the oesophagus by medication). When this procedure is applied, the areas of the cardiac and fornix fundus should be carefully examined, (s. fig. 14.9)... 

The frequency of cryptogenic liver abscesses (at one time 30-40%) has now been reduced to 10-15% as a result of modern contrast-medium imaging procedures and improved or more advanced serological, bacteriological and parasitological methods. Improved diagnostic clarification of the clinical picture in terms of respective pathogens and other causes has contributed to better treatment results and a clear drop in mortality. (91, 113)... 

The protective effects of intravenous hydration alone (0.45% isotonic saline, 1 ml/kg/hour for 12 hours before and 12 hours after contrast administration), fenoldopam (0.1 microgram/kg/minute for 4 hours before and 4 hours after the procedure), and acetylcysteine (600 mg bd 24 for hours before and 24 hours after the procedure) have been compared in preventing contrast nephrotoxicity after intravascular administration of low-osmolar non-ionic contrast medium (199). The incidence of nephrotoxicity was 15% in the hydration group, 16% in the fenoldopam group, and 18% in the acetylcysteine group. AU the groups were comparable and basehne creatinine clearance was about 60 ml/minute in aU the patients who received a similar dose of the contrast medium (1.5 ml/ kg). The authors concluded that fenoldopam and acetylcysteine do not offer extra protection against contrast nephrotoxicity over hydration alone. 

Ultrasound has superseded amniofetography, a procedure in which contrast media are injected into the amniotic sac during pregnancy to delineate fetal abnormalities. Diatrizoate, iotalamate, and, earher, iodized oil were used. There is a theoretical risk of premature labor. Accidental injection of contrast medium into the fetal subcutaneous tissues could cause sloughing of the skin or subcutaneous necrosis. Cases of thyroid hjrperplasia or hypothyroidism were also commonly described. 

Greater use of nonionic contrast media for routine X-ray procedures is clearly the trend of the future. It was estimated that in 1991, approximately 69% of the procedures performed in the United States used nonionic contrast media compared to about 66% in Europe and more than 80%in Japan. In 1994 the percentage increased to about 80% in the United States, 75% in Europe, and 92%in Japan (540). In the United States, in 1994 as many as 18 million patients received intravascular contrast media, and an estimated 170 million contrast medium-enhanced radiologic studies were performed from 1978 to 1994 (541). 

The Ts resin uptake and related procedures are theoretically unaffected by iodine contamination of the specimen or the glassware, as the final measurement is a radioactivity count. This is confirmed in practice with one minor exception, in which the contrast medium, Oragrafin, was found to increase T3 resin uptake and a resin sponge technique (BIO). 

A pouchogram of the atretic proximal esophagus is not usually necessary because of the low incidence a fistula from the proximal pouch (Fig. 2.9). In addition, this is a dangerous procedure if improperly performed. Air or non-ionic isotonic contrast medium can be injected to distend the pouch (Fig. 2.10). Over distention of the pouch with contrast medium will invariably result in aspiration so only a small volume of contrast medium, not exceeding 1-2 ml, is injected into the blind-ending pouch with the child in the true lateral position. Contrast medium must be removed at the end of the procedure. 

A contrast enema with a water-soluble (diluted gastrographin) 1 3 contrast medium will show fecal impaction in the terminal ileum and proximal colon. This procedure may also have a therapeutic effect (Devos and Meradji 2003). 

The retrograde or push technique is the most widely used technique for both the adult and paediatric populations. One should start by performing an upper abdominal ultrasound scan to assess and mark the position of the liver and transverse colon. The colon can be opacified using contrast medium to better delineate its position and thereby decreasing the risk of inadvertently puncturing it during the procedure. 

The tube for intravenous contrast medium administration must be connected from behind the CT scanner after being inserted, the venous access must first be closed and the reopened and connected to the contrast medium tube once the arms have been repositioned. Unfortunately, blood quite often drips onto the gantry during this procedure. 

The above-mentioned procedures to contrast urethra and bladder are not consistent within the literature, where most authors do not administer any contrast medium at all but instead instruct the patient to empty the bladder prior to the examination [1,38,46]. The latter is necessary to prevent masking of a rectocele or enterocele by the combination of a full bladder and a cystocele that blocks the entire genital hiatus. 

A transient encephalopathy has been reported after the use of an iodinated contrast medium in a neurointerventional procedure with development of psychomotor agitation, disorientation, and progressive left faciobrachial hemiparesis 30 minutes after successful treatment of a right carotid-ophthalmic fusiform aneurysm [6 ]. A CT scan showed marked cortical enhancement and edema in the right cerebral hemisphere, thought to be due to contrast extravasation after disruption of the blood-brain barrier. Treatment with dexa-methasone and maimitol produced complete recovery. 

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