A 36-year-old man was referred for contrast-enhanced CT. A catheter was placed into a vein in the antecubital fossa, and approximately 100 mL of nonionic low-osmolar contrast medium was injected using a power injector. The patient complained of pain after the injection, and the site of the injection was noted to be swollen and tender. There was contrast enhancement on the diagnostic images. A radiograph of the injection site was obtained (Fig. 1). Where is the contrast material? What explains the physical examination findings? What is the risk of extravasation injury?

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Fig. 1 —36-year-old man with contrast extravasation that occurred during contrast-enhanced CT. Lateral radiograph of elbow shows collection of contrast medium in superficial soft tissues of antecubital fossa.

The contrast medium has been extravasated into the skin and subcutaneous tissues around the injection site. The volume of extravasated contrast material is relatively small, an observation supported by the presence of enhancement on the diagnostic scan. Because the extravasation is superficial, the collection should be palpable on physical examination. As the contrast diffuses and begins to resorb, the palpable collection will dissipate. In a large study of contrast extravasation, Wang et al. [1] reported that 79% of patients had localized swelling after extravasation, 24% had pain, and 8% were asymptomatic. Extravasation injury is relatively rare; Wang et al. found that more than 97% of patients with contrast extravasation had minimal or no injury. The incidence of extravasation during contrast-enhanced CT with power injection can be estimated to be approximately 0.45% on the basis of six series published between 1991 and 2007 [1–6] that report an aggregate of 867 extravasations in 190,656 scans (Table 1).

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TABLE 1: Rate of Contrast Extravasation During Contrast-Enhanced CT With Power Injection in Six Published Series

A 54-year-old woman was referred for a contrast-enhanced CT examination, which was performed uneventfully. The patient complained of discomfort over the antecubital fossa where the injection catheter had been placed, but there was no apparent infiltration on physical examination when the catheter was removed. A few minutes later, the radiologist monitoring the examination noticed that there was no enhancement. Radiographs of the arm were subsequently obtained (Fig. 2A and 2B). Where is the contrast material? Why was the physical examination negative? What is the risk of extravasation injury?

The contrast material has been extravasated into the subcutaneous space. Radiographic features of subcutaneous extravasation include wide diffusion of contrast in the superficial soft tissues that is not restricted by compartmental anatomy, outlining of the muscle compartments by contrast around their periphery and infiltrating margins as contrast spreads through the interstitial tissues [7, 8]. In the arm and forearm, there is no risk of compartment syndrome when the extravasated contrast medium is extracompartmental. In this case, although the volume of extravasated contrast medium appears to be large, the obese habitus of the patient would have made it challenging to palpate the collection.

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Fig. 2A —54-year-old obese woman with contrast extravasation that occurred during contrast-enhanced CT. Anteroposterior radiographs of forearm (A) and arm (B) show contrast medium extending from forearm proximally to axilla in subcutaneous space. Margins of contrast material are infiltrative. Contrast medium outlines periphery of muscle compartments of forearm.

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Fig. 2B —54-year-old obese woman with contrast extravasation that occurred during contrast-enhanced CT. Anteroposterior radiographs of forearm (A) and arm (B) show contrast medium extending from forearm proximally to axilla in subcutaneous space. Margins of contrast material are infiltrative. Contrast medium outlines periphery of muscle compartments of forearm.

A 66-year-old man was referred for CT angiography of the neck, which was performed uneventfully. Subsequently, the radiologist reviewing the scans noticed that the expected contrast enhancement was not present. The patient had not complained of pain during or after the injection, and the injection site did not appear swollen when the needle was removed. Radiographs of the arm were obtained (Figs. 3A and 3B). Where is the contrast material? Why was the initial physical examination negative? What is the risk of extravasation injury?

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Fig. 3A —66-year-old man with contrast extravasation that occurred during CT angiography. (Reprinted with permission from [8]) External and internal rotation radiographs of arm approximately 1 hour after contrast injection show soft-tissue collection of contrast material in expected location of biceps compartment. Contrast collection is completely contained, with sharp margins.

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Fig. 3B —66-year-old man with contrast extravasation that occurred during CT angiography. (Reprinted with permission from [8]) External and internal rotation radiographs of arm approximately 1 hour after contrast injection show soft-tissue collection of contrast material in expected location of biceps compartment. Contrast collection is completely contained, with sharp margins.

The contrast medium is located within the biceps brachii muscle compartment. Radiographic features of subfascial (intracompartmental) extravasation include distribution of contrast material restricted by compartmental anatomy, very sharp margins where the contrast collection is contained by the fascia, and feathery margins where contrast medium is spreading through muscle fibers [7, 8]. The tip of a badly placed needle in the antecubital fossa may enter the biceps brachii or the mobile wad (lateral) muscle compartments. In this case, the entire volume of extravasated contrast was forced into the biceps brachii compartment, so there was no pain or swelling at the injection site. When extravasated contrast medium is intracompartmental, there is a risk of compartment syndrome developing. Intracompartmental extravasation of contrast with compartment syndrome is a rare event that may sometimes require expedient treatment by fasciotomy [8–11].

Extravasation of contrast medium during a CT examination performed using power injection is not rare. A review of the literature finds six series with different sample sizes reporting rates of between 0.14% and 0.94% (Table 1). Combining the data of those six published series yields an extravasation rate of 0.45%. Therefore, if a radiology department performs 12,000 contrast-enhanced CT examinations per year using power injectors and if the rate of extravasation is similar to that reported in the literature, the expected number of extravasations would be approximately 54, or about one per week. Option C is the best response. Options A and B are over-estimations, and option D is an underestimation.

In a retrospective study of 459 patients who had extravasation of nonionic iodinated contrast medium during CT examinations, 447 (97.4%) had no or minimal adverse effects, 10 (2.2%) had moderate adverse effects, and two (0.4%) had severe adverse effects [1]. Thus, moderate or severe adverse effects after extravasation of nonionic iodinated contrast medium are relatively rare. Option E is the best response. Options A, B, C, and D are not the best responses.

Reported complications of iodinated contrast medium extravasation include skin ulceration, soft-tissue necrosis, and compartment syndrome. Mechanisms of injury are related to osmolality, cytotoxicity, volume, and mechanical compression [12]. Options A, B, and C, are not the best responses. Nephrogenic sclerosing fibrosis is a condition that is related to the use of gadolinium-based contrast medium in patients with renal failure who undergo MRI [13]; it is not known to occur with extravasation of iodinated contrast medium. Option D is the best response.

In a study of 40 patients with contrast extravasation during CT performed with a mechanical power injector, Jacobs et al. [5] found no significant correlations between the rate of extravasation and catheter location, catheter size, or injection rate [5]. Options A, B, and D are not the best responses. Sistrom et al. [2] found that 16 (57%) of 28 cases of contrast extravasation during CT occurred in patients who had been injected through indwelling IV lines, whereas the remaining 12 had been injected through cannulas or needles inserted while the patient was in the CT suite. Although they did not report the types of venous access used in their 20,922 patients who did not have contrast extravasation, others [12] have suggested that the use of indwelling IV lines is associated with an increased risk of contrast extravasation. Option C is the best response.

Subfascial (intracompartmental) extravasation refers to extravasation into a fascial compartment. The radiographic features of this include confinement of the contrast medium to a compartment, very sharp margins around the extravasated contrast where it is confined by the compartment, and a feathered appearance at the margins where contrast material is infiltrating muscle fibers [7, 8]. Option C is the best response. Contrast material that has been extravasated into the subcutaneous space will have infiltrating margins and subcutaneous location. Options A and D are not the best responses. The distribution of contrast medium will not be confined by compartments and may extend above and below the elbow. Option B is not the best response.

Contrast medium extravasated into the subcutaneous tissues (extracompartmental) will diffuse in the subcutaneous space, distributing itself widely up and down the extremity [7, 8]. Therefore, subcutaneous extravasation into the forearm will not be confined below the elbow. Option B is not the best response. An infiltrating margin will be present where contrast diffuses in the interstitial tissues; a sharp margin will occur if the contrast medium is contained inside a muscle compartment. Options A and D are not the best responses. Extravasated contrast material in the subcutaneous tissues may surround and outline muscle compartments. Option C is the best response.

Symptoms of contrast extravasation include localized swelling (79% of patients reported by Wang et al. [1]) and pain (24% [1]). A few patients (8%) may be asymptomatic [1]. Options A and C are not the best responses. Signs of contrast extravasation include edema, erythema, and tenderness. Option D is not the best response. Pallor has not been described as a sign of contrast extravasation; therefore, option B is the best response.

The rationale for the application of ice packs or cold compresses after extravasation of contrast medium is that it causes vasoconstriction and limits the development of inflammation [12, 13]. Option A is the best response. The use of cold compresses or ice packs is based on anecdotal evidence, with scant experimental support from a study of high-osmolar contrast medium [14]. The opposite view has also been proposed, with the rationale that the application of warm compresses increases blood flow and improves absorption of the extravasated contrast medium. Options B and D are not the best responses. Elevation of the affected limb is recommended because it reduces capillary hydrostatic pressure [10, 11]. Option C is not the best response.

The volume of extravasation per se does not appear to be correlated with the likelihood or severity of the extravasation injury. In their study, Wang et al. [1] encountered moderate and severe extravasation injuries with extravasated volumes in the 10- to 150-mL range. However, 57 of 61 (93%) patients with extravasated volumes in the 100- to 150-mL range had minimal or no extravasation injury [1]. Option E is the best response. Options A, B, C, and D are not the best responses.

Once extravasation of contrast medium has occurred, arterial insufficiency, venous insufficiency, lymphatic insufficiency, connective tissue disease, and diabetes mellitus increase the risk that a more severe extravasation injury will occur because patients with these conditions are less able to tolerate the extravasation [10]. Options B, C, and D, are not the best responses. Hypertension has not been suggested as a possible risk factor for extravasation injury. Option A is the best response.