Imaging features of renal malperfusion in aortic dissection

Abstract

Objectives: Malperfusion syndrome accompanying aortic dissection is an independent predictor of death with in-hospital mortality rates >60%. Asymmetrically decreased renal enhancement on computed tomography angiography is often considered evidence of renal malperfusion. We investigated the associations between renal enhancement, baseline laboratory values and the diagnosis of renal malperfusion, as defined by invasive manometry, among patients with aortic dissection.

Methods: In this retrospective cohort study, we included all patients who were referred to our institution with acute dissection and suspected visceral malperfusion between 2010 and 2020. We determined asymmetric renal enhancement by visual assessment and quantitative density measurements of the renal cortex. We collected invasive renal artery pressures during invasive angiography at the aortic root and in the renal arteries. Logistic regression was performed to evaluate independent predictors of renal malperfusion.

Results: Among the 161 patients analysed, the majority of patients were male (78%) and had type A dissection (52%). Invasive angiography confirmed suspected renal malperfusion in 83% of patients. Global asymmetric renal enhancement was seen in 42% of patients who did not have renal malperfusion during invasive angiography. Asymmetrically decreased renal enhancement was 65% sensitive and 58% specific for renal malperfusion. Both global [odds ratio (OR) 4.43; 1.20-16.41, P = 0.03] and focal (OR 11.23; 1.12-112.90, P = 0.04) enhancement defects were independent predictors for renal malperfusion.

Conclusions: In patients with aortic dissection, we found that differential enhancement of the kidney as seen on the computed tomography angiography is predictive, but not prescriptive for renal malperfusion. While detection of renal malperfusion is aided by computed tomography angiography, its diagnosis requires close monitoring and often invasive assessment.

Keywords: Aortic dissection; Asymmetric enhancement; Renal malperfusion.

Figure 1:

Patient selection flowchart.

Figure 2:

Assessment of renal enhancement on computed tomography angiography. CTA: computed tomography angiography; HU: Hounsfield units.

Figure 3:

(A) Occlusion type by kidney. (B) Luminal supply of renal arteries.

Figure 4:

Representative example of dynamic changes in luminal enhancement due to contrast transit time in acute aortic dissection. (A) On initial angiographic images (time = 4:25 pm) the false lumen shows higher enhancement than the true lumen. (B) Approximately 1 min later (4:26 pm) enhancement of both lumens equilibrates to a low level. (C) Subsequently, the patient received another bolus of intravenous contrast and on repeat scan 7 min later (4:33 pm) the luminal enhancement pattern is reversed with the true lumen demonstrating higher enhancement. The patient underwent repair of his type A dissection, and on CT 9 years later, there was no renal atrophy. F: false lumen.