Radiology Teaching Files > Case 48899530

Contributed by: Aaron Betts, Resident, Brooke Army Medical Center, Texas, USA.
Patient: 68 year old
History: 68 year old patient: nine days post coronary artery bypass graft. Patient began having worsening hemoptysis, and CT chest pulmonary angiogram was performed to evaluate for possible pulmonary arterial pseduoaneurysm secondary to Swan-Ganz catheter placement. Prior CT chest pulmonary angiogram had been performed 6 days earlier.

Fig. 1: Coronal sternum, post-operative day 3.

Fig. 2: Coronal sternum, post-operative day 9.

Fig. 3: Axial, post-operative day 3.

Fig. 4: Axial, post-operative day 9
Findings: No pulmonary artery pseudoaneurysm present. However, the CT revealed diastasis of the inferior aspect of the midline sternotomy, measuring 1 cm at the inferior aspect of the sternum, which measured only 5 mm on the study on the third postoperative day. Addtionally, increased density is seen in the soft tissue in the gap, and within the soft tissues superficial and deep to the sternum. Sternal cerclage wires remained intact. Small amount of pneumomediastinum noted, which was improved compared to first examination. Bilateral pleural effusions are also noted.
Diagnosis: Sternal dehiscence with concern for wound infection and mediastinitis.

Sternal wound infection is a known complication of coronary artery bypass graft, which occurs in approximately 1-2% of sternotomies. The wound infection can be a limited superficial infection, or may progress to mediastinitis.

Clinically, patients with mediastinitis are more likely to have systemic symptoms of fever and leukocytosis. Wound infections are usually monomicrobial. The most common organism is methicillin sensitive staphylococcus aureus (MSSA), followed by methicillin resistant staph (MRSA). MSSA is usually related to preoperative colonization, whereas MRSA is usually a nosocomial infection.

The earliest finding is sternal dehiscence, and there may be disruption or alteration of the appearance of the cerclage wires. Gaps greater than 3 mm are usually indicative of sternal instability, and progressive widening indicates dehiscence. Dehiscence is frequently associaetd with infection, and this finding should raise possibility of infection. Infection will usually manifest approximately 2 weeks postoperatively. If the infection spreads to osteomyelitis of the bone, CT will show osseous erosion, Mediastinitis will show fluid collections and mediastinal gas. The distinctions are important because mortality is increased in mediastinitis compared to superficial wound infections. Additionally, the imaging findings may direct the provider to specific treatments.

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Additional Details:

Case Number: 48899530Last Updated: 2011-01-11
Anatomy: Chest   Pathology: Infection
Modality: CTAccess Level: Readable by all users
Keywords: dehiscence, coronary artery bypass graft

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