Medical Image of the Week: Staphylococcal Pneumonia in a Patient with Influenza

Figure 1. Thoracic CT scan axial view demonstrating bilateral cavitary infiltrates.

A 63-year-old, obese diabetic man presented to his primary care physician with complaints of fever, headache, myalgias, and cough. A nasal swab specimen was positive for influenza A by fluorescent immunoassay. Therapy with oseltamivir was initiated. The patient’s symptoms progressed and he was transported to the emergency department , where he was found to have a room air oxygen saturation of 74%, bilateral basilar infiltrates on chest radiograph, a white blood count of 24.2 K/uL and a procalcitonin level of 12.66 ng/ml. He was placed on BIPAP with high flow supplemental oxygen,  started on empiric intravenous antibiotic therapy with vancomycin and piperacillin/tazobactam, and admitted to the intensive care unit.  Blood and sputum cultures were eventually positive for methicillin-sensitive Staphylococcus aureus, and the patient’s antibiotic therapy was de-escalated to nafcillin. On hospital day 5, a CT of the chest obtained to evaluate pleuritic pain revealed extensive bilateral cavitary infiltrates (Figure 1). The patient’s discomfort resolved without further intervention, he continued to improve, and was uneventfully transitioned to oral therapy. 

S. aureus pneumonia is characterized by high fever, productive cough, and a radiographic pattern of patchy, often multilobar, infiltrates which may exhibit cavitary change.  In the USA, approximately 2% of patients admitted to the hospital for treatment of community-acquired pneumonia demonstrate microbiologic evidence of S. aureus infection (1). There is a slight predominance of methicillin sensitive species (MSSA) compared to methicillin resistant species (MRSA).  Morbidity and mortality are both high, with over 80% of patients requiring care in the ICU, and a fatality rate of 13% (2).

Among patients admitted to the intensive care unit with a primary diagnosis of influenza, there is a 15% incidence of S. aureus pneumonia. Risk factors for co-infection in this setting  include obesity, HIV infection, and immunosuppressive medication. There is a robust association between bacteremia and mortality (3).  Early empiric antibiotic therapy with an agent active against S. aureus should be strongly considered for patients admitted to the ICU with influenza complicated by pneumonia, pending the return of blood and respiratory cultures.

¹Charles VanHook, ²Kristin Dahlem, and ¹Angela Taylor

¹Longmont United Hospital, Longmont, Colorado USA

²Massachusetts College of Pharmacy and Health Sciences, Boston, Massachusetts USA

References

1. Jain S, Self WH, Wunderink R, et al. Community-acquired pneumonia requiring hospitalization among U.S. adults. N Engl J Med. 2015 Jul 30;373(5):415-27. [CrossRef] [PubMed]
2. Self WH, Wunderink RG, Williams DJ, et al. Staphylococcus aureus community-acquired pneumonia: prevalence, clinical characteristics, and outcomes. Clin Infect Dis. 2016 Aug 1;63(3):300-9. [CrossRef] [PubMed]
3. Martin-Loeches I, J Schultz M, et al. Increased incidence of co-infection in critically ill patients with influenza. Intensive Care Med. 2017 Jan;43(1):48-58. [CrossRef] [PubMed]

Cite as: VanHook C, Dahlem K, Taylor A. Medical image of the week: staphylococcal pneumonia in a patient with influenza. Southwest J Pulm Crit Care 2017:14(4):170-1. doi: https://doi.org/10.13175/swjpcc045-17 PDF

Medical Image of the Week: Massive Abdominal Aortic Aneurysm

Figure 1. Non-contrast CT A) axial, B) sagittal, and C) coronal views demonstrate a massive abdominal aortic aneurysm measuring 12.5 cm wide at maximal diameter.

Figure 2. Representative images from a CT-angiogram shows A) upper and B) lower abdominal axial sections showing renal artery involvement (red arrow) and substantial intramural thrombus (light blue brace). C) Coronal view demonstrates fusiform dilation of the iliacs (green arrow) and D) sagittal view demonstrates involvement of the thoracoabdominal aorta (pink arrow) and all major arterial branches of the abdominal aorta (celiac trunk, superior and inferior mesenteric arteries; dark blue arrows).

An 88 year-old presented to the emergency department with left flank and lower back pain as well as lower abdominal fullness. The fullness had started 2 days prior, but the left flank pain acutely started in the early morning before presenting. He had a history of unmedicated hypertension, hyperlipidemia, and mild vertigo. His review of systems was positive for chills and difficulty urinating but no hematuria. He was a non-smoker, and had undergone orthopedic surgeries but had otherwise avoided emergent hospitalizations.

On exam, vitals were unremarkable; there was no flank nor costovertebral angle tenderness; however, a midline pulsatile mass was present. An initial non-contrast CT abdomen/pelvis revealed a massive abdominal aortic aneurysm (AAA, Figure 1). Follow-up CT angiogram of the AAA can be seen in Figure 2. Upon further questioning, he had undergone a research study some 30 years earlier involving ultrasound to screen for AAA and was told he did not have one at the time.

AAA’s occur in 4-9% of the population (1-3) because of the diminished elastin in the infrarenal aorta. Inciting or etiologic factors include inflammatory, genetic and biochemical mediators, with positive risk factors including white race, atherosclerosis, smoking, male gender, hypertension, personal history of other arterial aneurysms, family history of AAA’s, and advancing age. Screening all men aged 65-79 has been shown to reduce mortality (2) despite the non-trivial mortality associated with elective AAA repair (3). Only 1% of 65 year-old men with a negative ultrasound will go on to develop an AAA (2).

The feared and fatal complication of AAA is rupture, and occurs in 10,500 ± 1,500 patients yearly in the U.S.A., with larger AAA’s posing higher annual risk of rupture (1-3). Emergent surgical repair mortality in the 30-50% that survive a rupture long enough to go to the operating room is roughly 50%.

The extensive nature of this patient’s aneurysm would have made for a nearly-impossible surgery, with operative mortality estimates between 15% using the British Aneurysm Repair Score (3) to 50% based on clinical opinion. This dissuaded the patient, his family, and vascular surgery team from pursuing elective repair. The patient desired discharge with pain medications and stricter blood pressure control with outpatient follow-up.

Michael Larson, M.D., Ph.D.

Tucson Hospitals Medical Education Program

Tucson, AZ, USA

References

1. Lederle FA. Ultrasonographic screening for abdominal aortic aneurysms. Ann Intern Med. 2003 Sep 16;139(6):516-22. [CrossRef] [PubMed]
2. Cosford PA, Leng GC. Screening for abdominal aortic aneurysm. Cochrane Database Syst Rev. 2007 Apr 18;(2):CD002945. [CrossRef] [PubMed]
3. Grant SW, Hickey GL, Grayson AD, Mitchell DC, McCollum CN. National risk prediction model for elective abdominal aortic aneurysm repair. Br J Surg. 2013 Apr;100(5):645-53. [CrossRef] [PubMed]

Cite as: Larson M. Medical image of the week: massive abdominal aortic aneurysm. Southwest J Pulm Crit Care. 2016:13(1):30-1. doi: http://dx.doi.org/10.13175/swjpcc052-16 PDF