Ann Thorac Surg 1995;59:1216-1217
© 1995 The Society of Thoracic Surgeons
Case Report
Diagnosis of Infected Modified Blalock-Taussig Shunt by Computed Tomography
Steven W. Turner, MB, BS,
Jonathan P. Wyllie, MRCP,
J. R. Leslie Hamilton, FRCS,
Hugh H. Bain, FRCP
Department of Paediatric Cardiology, Freeman Hospital, Newcastle-upon-Tyne, England
Accepted for publication September 19, 1994.
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Abstract
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Accurate localization of infection after pediatric cardiac operation is essential for correct decisions regarding treatment. We report a case of infection and endocarditis of a Blalock-Taussig shunt. Localization by computed tomography led to successful surgical intervention.
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Introduction
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We present a pediatric case of Streptococcus pneumoniae infection of a (Gore-Tex) right modified Blalock-Taussig shunt 5 weeks after operation. Although blood cultures identified the organism, computed tomography localized the site of infection to the subclavian end of the shunt. At operation the diagnosis was confirmed and the shunt was replaced by a left modified Blalock-Taussig shunt.
This female baby was born at 39 weeks' gestation weighing 2.4 kg after a normal pregnancy and delivery. She was noted to have a murmur on the first day of life, and a diagnosis of tetralogy of Fallot was confirmed by echocardiogram. She was managed as an outpatient until 4 months of age, when she began to have cyanotic spells. These proved resistant to propranolol and the baby was admitted for a 4-mm Gore-Tex (W. L. Gore & Assoc, Flagstaff, AZ) right modified Blalock-Taussig shunt. This was performed without complication and she was discharged home 5 days postoperatively.
She was admitted subsequently 5 weeks later with a 4-day history of pyrexia. Clinical examination was unchanged, with a clearly heard shunt murmur but no other physical signs. Urine microscopy and culture were normal and her chest roentgenogram and echocardiogram were unchanged. Her white blood cell count was 8 x 109/L, and the C-reactive protein level was elevated, at 241 µg/L. After isolation of S pneumoniae from blood culture, a lumbar puncture was performed. This demonstrated normal protein and glucose and no white blood cells, but 893 red blood cells/µL. A further blood culture was taken, and administration of amoxicillin, 150 mg/kg, was started intravenously.
Despite the normal initial findings, the cerebrospinal fluid grew several colonies of S pneumoniae. However, as there were such large numbers of organisms in the blood, it was thought that these originated from the contaminating blood of a traumatic lumbar puncture.
After 5 days' treatment, the C-reactive protein level had fallen to 41 µg/L, but the baby's pyrexia failed to resolve. The white blood cell count was now 20 x 109/L, but there was no clinical or echocardiographic evidence of a focus. A chest roentgenogram showed some faint haziness of the right hilum and upper zone. Computed tomography of the head and thorax was performed. The cranial scan was normal but that of the thorax revealed a fluid collection around the subclavian end of the shunt (Fig 1A
). The wall surrounding the cavity was enhanced with the injection of contrast medium (Fig 1B).
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Fig 1. . Computed tomogram showing walled fluid collection around shunt before (A) and after (B) contrast medium injection. (S = shunt; W = wall of cavity.)
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At thoracotomy a left modified Blalock-Taussig shunt was fashioned before removal of the right, as she had severe right ventricular outflow obstruction and we believed that she would not survive without a shunt. There was a small amount of clear fluid in a thick-walled cavity and vegetations could be seen in the subclavian end of the shunt. The removed shunt was culture-negative but antigen-positive for S pneumoniae.
The baby made an uneventful recovery after 2 weeks of intravenous amoxicillin followed by 2 weeks of oral amoxicillin.
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Comment
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The differential diagnosis of pyrexia in the postoperative period always should include the possibility of wound infection or bacterial endocarditis. Diagnosis of the latter is often difficult, and even with blood culture evidence of bacteremia, the most efficient way to locate the focus is arguable. Although computed tomography has a recognized role in the diagnosis of median sternotomy wound infections [1], transthoracic and transesophageal echocardiography and gallium or indium 111 scans may be more sensitive for endocarditis or deeper infections [2, 3]. The first line of imaging for abdominal abscesses is ultrasound and computed tomography in ill patients, but indium 111 in well patients [4]. However, although indium 111 has been shown to be more sensitive than computed tomography in the diagnosis of vascular graft infections [2, 3], it gives little anatomic detail and there is a high incidence of false positives in the acute postoperative period.
In this case, the presence of infection was suspected because of the history and the high C-reactive protein level; it was confirmed by blood culture. However, pnuemococcus is a rare cause of endocarditis [5], and it was the exact locus that was required and provided by computed tomography. We have found only 1 previous report of shunt endocarditis imaged in this way in a 16-month-old child with a mycotic pseudoaneurysm [6]. This case also involved the subclavian end of the anastomosis.
It seems likely that the infection occurred postoperatively, presenting after 5 weeks. Fortunately this complication is rare, and the only other case in our practice in the past 8 years was confirmed postmortem. In this situation, computed tomography should not be disregarded as a useful tool.
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Acknowledgments
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Jonathan P. Wyllie is supported by The Sir Jules Thorne Charitable Trust.
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Footnotes
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Address reprint requests to Dr Wyllie, Dept of Paediatric Cardiology, Freeman Hospital, Freeman Road, High Heaton, Newcastle-upon-Tyne, NE7 7DN, England.
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References
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- Kay HR, Goodman LR, Teplick SK, Mundth ED. Use of computed tomography to assess mediastinal complications after median sternotomy. Ann Thorac Surg 1983;36:706–14.
- Williamson MR, Boyd CM, Read RC, et al. 111 In-labled leukocytes in the detection of prosthetic vascular graft infections. AJR 1986;147:173–6.
- Berridge DC, Earnshaw JJ, Frier M, et al. 111 In-labled leukocyte imaging in vascular graft infection. Br J Surg 1989;76:41–4.
- Knochel JQ, Koehler PR, Lee TG, Welch DM. Diagnosis of abdominal abcesses witth computed tomography, ultrasound, and 111 In-leukocyte scans. Radiology 1980;137:425–32.
- Zuberbuhler JR, Neches WH, Park SC. Infectious endocarditis: an experience spanning three decades. Cardiol Young 1994;4:244–51.
- Boulden TF, Tonkin ILD, Burton EM, et al. Pediatr Radiol 1990;10:119–21.
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Abstract
Introduction
