الفهرس 
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Abstract
Severe Sepsis is associated with different factors with a great potential to damage the kidneys. These factors include hypotension, renal vasoconstriction, endotoxins and cytokines, and activation of inflammatory cells by Lipopolysaccharide (LPS) and inflammatory mediators. Hypoperfused kidney is sensitive to nephrotoxic agents that are usually administered in treatment of severe sepsis. So, patients with severe sepsis may be predisposed to the development of acute kidney injury (AKI).
AKI is very common in intensive care units (ICU). With the integration of consensus of AKI definition criteria from RIFLE (Risk, Injury, Failure, Loss, End-Stage Kidney Disease), AKIN (Acute Kidney Injury Network), and KDIGO (Kidney Disease Improving Global Outcomes), the incidence of AKI in ICU has been reported to range between 16% - 67%.
Populations at high risk of sepsis associated AKI as elderly patients have been identified. Also, females were found to be more affected. Other comorbidities as DM, CKD, heart failure and malignancy increase patients’ susceptibility. Sites of infection as bloodstream, abdominal, genitourinary and infective endocarditis are associated with a higher incidence of developing AKI.
Ultrasonography (U/S) was used routinely to assess renal morphology. But, renal Doppler U/S can be used to asses large arterial abnor¬malities and evaluate changes in intra-renal perfusion. Color Doppler investigation of the kidneys can show changes in the renal vasculature and blood flow.
Doppler U/S with arterial Renal Resistive Index (RRI) calculation can be used as early detector of the vascular resistance changes. It could help in the determination of the required systemic hemodynamics for renal perfusion. RRI is a non-invasive Doppler-measured parameter defined as, RRI = [(peak systolic velocity − end diastolic velocity)/ peak systolic velocity]. It theoreti¬cally ranges from 0 – 1, normally lower than 0.7 with age differences. The normal renal artery waveform demonstrates a rapid systolic upstroke and an early sys¬tolic peak. The ability of RRI to monitor the renal perfusion remains questionable. However, the value of RRI should be interpreted carefully before concluding that there is a renal injury, because low O2 and renal perfusion pres¬sure could result in high values without AKI.
Doppler U/S was found to be a useful tool for evaluating non-obstructive AKI. RRI 0.7 was found to be a good discriminator between acute tubular necrosis (ATN) and prerenal failure. RRI of 0.8 was a more reliable indicator of persistent AKI than that of common urinary markers. It is noninvasive, bedside, unaffected by diuretics or haemodialysis and it could be a promising tool to predict the reversibility of AKI in critically ill patients.
The aim of this study was to detect the predictive value of RRI in sepsis associated AKI. This study was carried out on adult patients who were admitted to the Critical Care Medicine department, Alexandria Main University Hospital with the diagnosis of sepsis according to (Sepsis-3) definition.
This descriptive study was conducted on 40 adult septic patients of both sexes. Then, according to the incidence and persistence of AKI, patients were classified into 3 groups (No AKI, transient AKI and persistent AKI).
The most important result was the difference between the two RRI readings (admission and after 24 hrs), it was found to be an excellent tool to predict the persistence of AKI at a cut off value of ≥ 0.05. It showed a good sensitivity (71.43%) and excellent specificity (100%) with PPV of 100% and NPV of 86.67%.
from the results of this study, Renal Doppler Ultrasonography based RRI was a good predictor for the persistence of AKI in critically ill septic patients. The difference more than 0.05 between the RRI measured at admission and that was measured after 24 hours, was shown to be an excellent predictor in predicting the persistence of AKI in such patients. Double blinded studies on larger scale should be conducted to evaluate RRI in special populations as hypertensive and diabetic patients, separately to determine the best cut off value for each.