Vasovagal reactions in CT colonography

Abstract

We describe the occurrence of vasovagal reaction in two patients who underwent CT colonography (CTC). The patients, asymptomatic, were submitted to CTC in one case after right colectomy and in one case for screening purposes. The vasovagal symptoms occurred after pneumocolon and acquisition in the prone decubitus, and included headache, hypotension, bradycardia, cold sweat and pallor, nausea, and diaphoresis. Abdominal pain was also referred. All symptoms resolved within 30 min to 3 h from their onset. In all cases the vasovagal reaction occurred after prone decubitus. CTC images showed a significant distension of the small bowel. Vasovagal reactions are potential complications of CTC. [PUBLICATION ABSTRACT]

Abdominal

Imaging

Springer Science+Business Media, LLC 2007 Published online: 1 June 2007

Abdom Imaging (2007) 32:552555 DOI: 10.1007/s00261-006-9055-6

Vasovagal reactions in CT colonography

Emanuele Neri, Davide Caramella, Francesca Vannozzi, Francesca Turini,

Francesca Cerri, Carlo Bartolozzi

Diagnostic and Interventional Radiology, Department of Oncology, Transplants and Advanced, Technologies in Medicine, University of Pisa, Via Roma 67, 56100, Pisa, Italy

Abstract

We describe the occurrence of vasovagal reaction in two patients who underwent CT colonography (CTC). The patients, asymptomatic, were submitted to CTC in one case after right colectomy and in one case for screening purposes. The vasovagal symptoms occurred after pneumocolon and acquisition in the prone decubitus, and included headache, hypotension, brady-cardia, cold sweat and pallor, nausea, and diaphoresis. Abdominal pain was also referred. All symptoms resolved within 30 min to 3 h from their onset. In all cases the vasovagal reaction occurred after prone decubitus. CTC images showed a signicant distension of the small bowel. Vasovagal reactions are potential complications of CTC.

Key words: CT colonographyVasovagal reaction

Vasovagal reactions are an abnormal reex stimulation of the vagus nerve; as a consequence the parasympathetic (vagal) outow to the sinus node of the heart increases, producing bradycardia; in parallel, vasodilatation in the skeletal muscles and in the splanchnic vascular bed oc-curs, with consequent hypotension; bradycardia and hypotension can lead to loss of consciousness for insufcient cerebral perfusion. Impending loss of consciousness may be heralded by blurred vision, cold sweat and pallor, nausea, diaphoresis, and abdominal discomfort [13].

Vasovagal reactions are rare complications of colonoscopic studies, caused by the bowel distention during the endoscope progression. It is believed that pain, distention of the colon, and stretching of the mesentery may stimulate the vagi sufciently to produce the reaction [46].

CT colonography (CTC) is emerging as a potential alternative to colonoscopy in some clinical settings car-

rying the advantage of being noninvasive and safe with high diagnostic accuracy in detecting large colorectal lesions [7]. However, the concept of safe examination has been recently debated after the report of two cases of perforation during pneumocolon [8, 9].

At the University of Pisa, 1500 CTC examinations have been performed. We describe the occurrence of vasovagal reaction in 2 (0.1%) patients who underwent CTC; in each case, no previous vasovagal attack, nor cardiac, renal or hepatic dysfunction was referred.

CT colonography study

To undergo CTC a dietary restriction was adopted starting 3 days before examination with low ber diet. The day before CTC, at 4 pm, each patient underwent bowel cleansing with ingestion of 3 L of osmotically balanced solution (SELG; Promefarm, Milan, Italy) containing polyethylene glycol; dietary restrictions were applied also for the dinner in the same day and for the breakfast the day of examination. The patients did not report any side effect after bowel cleansing.

The CTC was performed in the early afternoon without muscle relaxant. Pneumocolon was obtained after insufation of 1.5 mL of room air through a rectal tube. In all patients the air was inated by a radiologist, respecting patients tolerance. The time for insufation was 2 min in each case.

The CT study included rst a scout view, to check the bowel distention, followed by an acquisition in the supine decubitus. CT scan was performed with a four-row scanner (LightSpeed Plus; GE/Medical Systems, Milwaukee, WI, USA), by using 1.25 mm row thickness and pitch 6, at 0.5 s per tube rotation and low dose (120 kVp, 50 mA s). The time for CT acquisition (including scout view, protocol selection on the CT console and scanning) was 1.30 min.

A few seconds after the supine acquisition each patient was turned in the prone position respecting their tolerance and a second CT scan was obtained.

Correspondence to: Emanuele Neri; email: [email protected]

E. Neri et al.: Vasovagal reactions in CT colonography 553

Fig. 1. Patient 1. The CTC scout view, obtained at the beginning of the exam in the supine decubitus, shows an overdistention of the small bowel in the left upper quadrant of the abdomen (black arrows). The overdistention of the small bowel is also shown in the CT acquisition obtained in the supine decubitus (white arrows). T, transverse colon; D, descending colon. The coronal reformation shows the overdistention of the small bowel (black arrows) and the patency of the ileo-cecal anastomosis with air reflux in the small bowel (sb).

Patient 1

Female, aged 65, 3 years before had a previous right colectomy for a colorectal cancer underwent CTC to follow-up; the intervention included the removal of the ileo-cecal valve with subsequent ileo-colic anastomosis. Insufation in the supine decubitus did not cause abdominal pain, and no objective or subjective symptoms were reported. Immediately after the prone decubitus, at the end of the examination, the patient reported headache, nausea, stimulus to vomiting meanwhile cold sweat and diaphoresis were observed. Cardiovascular functions were monitored: ECG did not show alterations of the cardiac cycle, blood pressure was normal, but a substained bradycardia (56 beats/min) was observed.

The CTC data analysis revealed an overdistention of the small bowel in the supine (Fig. 1A, B) and in the prone decubitus (Fig. 1C).

Headache resolved after 3 h; the remaining symptoms in 30 min.

Discussion

In both cases, after the occurrence of vasovagal reaction the pneumocolon was immediately reduced by opening the enema bag. An anesthesiologist was promptly called and each patient was monitored for at least 3 h from the onset of the symptoms and dismissed from the Radiological Department.

We reviewed the incidence of vasovagal reactions in the literature and we found that the occurrence of this temporary clinical condition in CTC is not reported. On the other hand vasovagal reactions are rare complications of colonoscopic studies, reported with incidences between 0.1% and 16%, and caused by the bowel distention during the endoscope progression (Table 1.). It is believed that during the examination pain, distention of the colon and stretching of the mesentery may stimulate the vagi sufficiently to produce the reaction.

Dual positioning in CTC is required to obtain a complete colonic study [1618]. We believe that the prone position was in these patients the cause of vasovagal reaction since it determined an overdistention of the small bowel. Such condition, due to reflux of colonic air through the ileo-cecal valve, is commonly observed in CTC.

Patient 2

Female, aged 44, underwent CTC for screening purposes since she was rst degree relative of a patient with colorectal cancer. Two years before, she had an incomplete colonoscopy for the presence of dolicocolon.

Immediately after the prone decubitus, at the end of the examination, the patient reported abdominal pain, nausea, and stimulus to vomiting meanwhile cold sweat was observed. ECG did not show alterations of the

cardiac cycle, blood pressure was normal, and a sub-stained bradycardia (50 beats/min) was observed.

CTC data analysis conrmed the presence of the dolicocolon and revealed an overdistention of the small bowel in the supine (Fig. 2A, B) and in the prone decubitus (Fig. 2C). All the symptoms resolved in 30 min.

554 E. Neri et al.: Vasovagal reactions in CT colonography

Table 1. Incidence of vasovagal reactions in colonoscopy. Literature review

Author

Year of publication Examinations

Vasovagal reactionsa

Thomas-Gibson et al. [10]

2002 505 6 (1.2%)

Eckardt et al. [11] 1999 2500 22 (0.8%) Lee et al. [15] 1995 21,946 24 (0.1%) Herman et al. [12] 1993 223 37 (16%) Kjaergard et al. [13] 1986 1368 4 (0.29%) Macrae et al. [14] 1983 5000 Minimal

(no. not reported)

aData are number of patients

Fig. 2. Patient 2. The axial CT obtained in supine decubitus demonstrates a significant overdistention of the small bowel (black arrows). A, ascending colon; D, descending colon. The coronal reformation provides an overview of large and small bowel and clearly shows the overdistention of the entire small bowel (black arrows); C, cecum; A, ascending colon; T, transverse colon; D, descending colon.

In the patient with ileo-colic anastomosis two factors favored the reux in the small bowel: the absence of the ileo-cecal valve and the reduced volume of the colon after colectomy; this postoperative condition resulted in increased endoluminal pressure during the insufation of the content of the entire enema bag (1.5 L of room air), which was more properly adequate for a normal colon. Therefore, the CTC study in these patients should have foreseen the insufation of a moderate quantity of air. In the patient 2 the reux of air in the small bowel, that was yet observed in the supine position, can only be explained by a slight incontinence of ileo-cecal valve.

In both the cases reported, a signicant distention of the small bowel has been observed. We believe therefore that it was the cause of vasovagal reaction. As it is for perforation, vasovagal reactions are potential complications of CTC.

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