Six-year progression of medically treated infective aortitis

Introduction

Infective aortitis is a rare but life-threatening pathology. It is rapidly progressive, almost always with development of mycotic aneurysms that are of much higher rupture risk compared to conventional aneurysms.^1,2 It is non-specific in its clinical presentation, with common presenting complaints of abdominal and/or back pain, fevers, and malaise, and is characterised on computed tomography (CT) imaging by the presence of peri-aortic fat stranding with or without aneurysmal changes and abscess formation. ³ With modern advances in antibiotics, hygiene and healthcare, there has been a shift in the most common causative agents from staphylococci or streptococci species to salmonella species. ³ There is a strong recommendation for operative intervention first-line in these cases, thus there are very few cases reporting on medically managed infective aortitis, and even fewer that have been successful. We present a case of salmonella aortitis successfully treated medically, with CT imaging up to 6 years post-diagnosis demonstrating the phases of acute, subacute, and resolved infectious aortitis.

Case

A 77-year-old female presented to a rural hospital with 4 days of abdominal pain, associated with anorexia, vomiting, and fevers to 38C. She had a history of known breast cancer resected primarily and no other significant risk factors such as smoking, diabetes or conditions/medications resulting in immunocompromise. She recounts eating undercooked chicken shortly before symptom onset and was commenced on oral amoxicillin by her general practitioner. She had a white cell count of 7.1x10⁹/L but a raised C-reactive protein level of 82 mg/L. She underwent a computed tomography (CT) scan of her abdomen, followed by a CT angiogram, demonstrating marked fat stranding surrounding the para-renal aorta which had a thickened wall but minimal calcific atherosclerotic disease otherwise (Figure 1). On discussion with the closest referral centre, she was transferred to a larger hospital and commenced on intravenous ceftriaxone 2g daily for reasonably broad coverage of potential organisms including staphylococci, streptococci, haemophilus species, escherichia coli, and salmonella species. ³ OPEN IN VIEWER

Clinically, she improved on intravenous antibiotics. She had no further fevers, her pain and biochemistry improved, and progress CT angiography three days after the first demonstrated reduction in fat stranding. Unfortunately, her blood cultures, taken prior to administration of intravenous antibiotics, were negative. Upon further discussion with Infectious Diseases, a presumptive diagnosis of salmonella aortitis was made given her history and symptoms of gastroenteritis. After thorough exploration of risks and benefits, the patient did not want operative intervention and thus was discharged after one week with ongoing daily intravenous ceftriaxone 2g daily via a peripherally inserted central catheter and weekly follow-up.

On follow-up CT angiography 2 weeks later, her infrarenal aorta had expanded significantly in size to 36 mm in maximal diameter with worsening stranding and concurrent development of a small saccular suprarenal aortic aneurysm (Figure 2 - top). A thorough discussion was had with the patient regarding the increased difficulty of potential endovascular repair in the context of the suprarenal aneurysm and discussed options for open repair. The patient, acknowledging the risks of rupture, sepsis, and death, again opted for non-operative management. On repeat discussion with Infectious Diseases, she was commenced on oral ciprofloxacin 500 mg twice a day alongside the intravenous ceftriaxone for more aggressive salmonella coverage, receiving a total of 6 weeks of ceftriaxone followed by life-long ciprofloxacin. She did agree to ongoing follow-up and imaging to better assess disease progression and treatment outcomes. CT angiography 8 weeks post-diagnosis demonstrated further growth in size for both infrarenal (46 mm) and suprarenal (29 mm) aneurysms but with reduced fat stranding compared to previous (Figure 2 –bottom). From that point, ongoing follow-up scans performed annually demonstrated no significant change in aneurysm size. Follow-up CT imaging done 4 years post-diagnosis demonstrated stable saccular aneurysmal disease both infrarenal (48 mm) and suprarenal (28 mm),with no fat stranding, and it was identical to the 6-year post-diagnosis CT (Figure 3). She had self-ceased her ciprofloxacin after 1 year and had been asymptomatic from a vascular perspective, and is now undergoing standard surveillance for below-threshold aortic aneurysms.OPEN IN VIEWER

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Figure 3.

Follow-up CT Angiograms at 4 years (top) and 6 years (bottom).

Discussion

The literature paints a very grim prognosis for infective aortitis, particularly those managed medically with up to 75%–100% mortality, albeit noting the significant risk of selection and publication bias contributing to these figures.^1–4 There are very few case reports commenting on successfully medically treated infectious aortitis, and none have extensive follow-up imaging.^1–5 Surgical approaches in the management of infectious aortitis include in situ graft repairs, extra-anatomical bypass grafting, patch repairs and more recently, endovascular aneurysm repairs, with these approaches having an estimated 20%–40% mortality.^1,2,4–8

The proposed pathophysiology of infective aortitis involves seeding of bacteria into the arterial intima resulting in endothelial infection, often in the presence of atherosclerosis and hypertension causing intimal damage.^2,3 Elastolytic and collagenolytic enzymes created during this infective process can result in formation of mycotic aneurysms that expand rapidly and are at high risk of rupture.^3,9 This case demonstrates this progression, with rapid aneurysmal degeneration associated with active infection within the subacute period, which stabilised once the infection was controlled with no further growth many years after initial insult. Current guidelines recommend repair of mycotic aneurysms regardless of size, with endovascular approaches deemed an acceptable alternative, thus this case offers a rare glimpse into the natural progression of infective aortitis and mycotic aneurysms.

Conventional approaches to this pathology involved large open aortic surgery thus surgical decision-making involved discussing significant operative risk and possible post-operative complications and some patients, like the one discussed in this case, opt to take a non-operative route. There have been case reports on successful endovascular repairs that prevent aneurysmal progression in infective aortitis particularly from Salmonella,^8,9 which may be better tolerated for the more comorbid patient. The endovascular approach recommends pre-operative anti-infective therapy ranging from 1 week to 4 months in non-emergent cases, and further antibiotics post-operatively for at least 6 weeks. ¹ It is interesting to consider whether the stent graft would still be required at this point after 4 months of antibiotics, given the findings in this case of no further aneurysmal dilatation once infection was cleared.

Antimicrobial therapy is paramount in the management of infectious aortitis, regardless of definitive management plan. Unfortunately, infectious aortitis is culture negative in 20%–50% of cases.^3,4,10 Early, effective empiric antimicrobial therapy is associated with decreased mortality.^4,9,10 Whilst there are no definitive guidelines on agents to use in infectious aortitis, there is a preference of using third generation cephalosporins with or without fluoroquinolones in the literature with a recommended duration ranging from 6 months to life-long.^1,3–6,10 There has also been a distinction established between salmonella aortitis compared to non-salmonella infection, with favourable long-term outcomes in the salmonella cohort.^4,9 For this reason, there are recommendations for life-long antibiotics and vigilant monitoring after intervention in cases of non-salmonella infection and 6–12 months of antibiotics in salmonella cases.^4,9 When considering conservative management, the causative organism is thus a key factor in determining chances of success. Patients who are immunocompromised or with particularly virulent microorganisms such as fungal infections, pseudomonas species or staphylococcal species would be unlikely to survive conservative management.

Conclusion

Infectious aortitis remains a predominantly surgical issue, with a shift towards endovascular management, and the current recommendations advocate for intervention to mitigate rupture risk. However, there will always be a subset of patients who present too unwell for surgery or refuse surgery, and it is in this cohort that undergo medical treatment, formulating the dismal mortality figures quoted in previous papers. This case demonstrates an otherwise well lady who opted for medical management and had a good outcome. While she was certainly fortunate, her case and surveillance bring to light key factors that may affect therapeutic decision-making. Firstly, the development of mycotic aneurysms occurs predominantly during the acute and subacute infective phase, with no further deterioration after active infection is controlled. Thus, if intervention is being planned, earlier intervention would be recommended over delayed intervention. Secondly, less aggressive causative agents (e.g., presumed salmonella in this case) would have better chances surviving medical therapy than others (e.g., pseudomonas). Confirmatory cultures of less virulent organisms may therefore be a relative indication for conservative management if contemplating options during clinical equipoise, such as in a relatively comorbid patient with infectious aortitis.