Ultrasound in Acute Kidney Injury | BMUS, Lecture notes of Radiology

Download Ultrasound in Acute Kidney Injury | BMUS and more Lecture notes Radiology in PDF only on Docsity! Ultrasound in Acute Kidney Injury Pamela Parker Ultrasound Specialty Manager Aims • What is Acute Kidney Injury (AKI)? • Discuss the implications of AKI for USS • Revisit Resistive Index (RIs) ie) ara! es or OO Rt Kidney Hull and East Yorkshire Hospitals NHS Dimes AKI Explained • The older term is 'acute renal failure' (ARF). • Acute kidney injury (AKI) is a rapid deterioration of renal function, resulting in inability to maintain fluid, electrolyte and acid-base balance. AKI Explained • It is detected and monitored by serial serum creatinine readings primarily, which rise acutely • The definition of acute kidney injury has changed in recent years, and detection is now mostly based on monitoring creatinine levels, with or without urine output. Why NICE? • Acute kidney injury: prevention, detection and management of acute kidney injury up to the point of renal replacement therapy • NICE guideline August 2013 Why NICE? • Estimated that improving care could save 12,000 lives in England and save the NHS £150 million per year NICE Guideline 2013 Ultrasound Offer urgent ultrasound of the urinary tract to patients with acute kidney injury who: – have no identified cause of acute kidney injury, or – are at risk of urinary tract obstruction. • Ensure that the imaging is performed within 24 hours of assessment. nem eCelal ea Hull and East Yorkshire Hospitals NHS Dimes Classification and Definitions • RIFLE (Risk, Injury, Failure, Loss, End stage kidney disease), 2004 • AKIN (Acute Kidney Injury Network) • KDIGO (Kidney Disease: Improving Global Outcomes), 2012 • pRIFLE paediatric version of RIFLE Classification and Definitions • NICE recommends that AKI can be detected by using any of the following criteria, in line with pRIFLE, AKIN or KDIGO definitions: Stage eGFR (ml/min/1.73 m 2 ) Description Qualifier 1 ≥ 90 Kidney damage, normal or increased GFR Kidney damage (presence of structural abnormalities and/or persistent haematuria, proteinuria or microalbuminuria) for ≥ 3 months 2 60-89 Kidney damage, mildly reduced GFR 3A 45-59 Moderately reduced GFR ± other evidence of kidney damage GFR < 60 ml/min for ≥ 3 months ± kidney damage 3B 30-44 4 15-29 Severely reduced GFR ± other evidence of kidney damage 5 < 15 Established kidney failure Causes Pre-Renal 40-70% Renal 10-50% Post-Renal 10% Renal Hypoperfusion Acute tubular necrosis Obstruction • Hypovolaemia (Ischaemia of renal tubules) • Sepsis Drugs • CCF Contrast agents • Cirrhosis Haemoglobinuria • NSAIDs or ACEi myeloma Vasculitis Assessment and Investigations • It is important to first identify the cause of AKI, as this will affect management, particularly where there is a potentially treatable cause (for example obstruction, hypovolaemia, nephrotoxic drugs or glomerulonephritis). — le — L.Kidney Oblique R.Kidney Oblique R.Kidney Oblique SMIRNCEH CCIE es acc ult | Tang Bladder Ultrasound • Imaging technique most commonly used in initial evaluation of patients with suspected AKI • Widely available • Easy to use and free of complications • Portability,especially for critically ill patients in ICU • Although the rate of abnormal ultrasound findings in the setting of AKI is not high (about 10%), these findings can have a significant impact on patient management Ultrasound - Basic information • Renal size and cortical echogenecity – Normal range 9 – 10.5am – = / Hypoechoic to Liver • Large (AKI) vs Small (CRF) • Cortical Thickness / preservation – Normal range >1cm • Thick (AKI) vs Thin (CRF) 1: AKI 2: Normal 3: CRF Hull and East Yorkshire Hospitals TSMC Can we do more? • In the early 1990s, several groups postulated that the pathophysiology of urinary obstruction might be reliably manifested by changes in arterial Doppler spectra • Haemodynamic response obstruction • Renal blood flow decreases, and renal vascular resistance increases Resistive Index • This vasoconstriction response is an ideal phenomenon to be detected by changes in the RI • RI can be increased by extrinsic factors such as kidney compression, breath holding during the Valsalva manoeuver and extreme bradycardia • RI values are also correlated with arteriovascular disease (check if bilateral) Resistive Index in AKI • RI greater than 0.70 or a difference of greater than 0.06–0.10 in mean RI values between kidneys is found to be highly specific and sensitive for acute obstruction • Evidence of obstruction identified before the development of collecting system dilatation with the use of RI values Case 1 The right renal length measures 10.8cm. The left renal length measures 11.3cm. There is mild left renal pelvic fullness with a maximum AP diameter of 1 cm. There is a small cortical cyst arising from the right kidney. Otherwise both kidneys demonstrate normal collecting system and cortex. Good cortical preservation noted. The bladder is poorly filled and therefore the prostate volume cannot be established. The aorta is obscured by overlying bowel gas and cannot be measured today. G4 NHS tg Platt J, Rubin J, Ellis J, DiPietro MA. Duplex Doppler US of the kidney; differentiation of obstructive from nonobstructive dilatation. Radiology 1989; 171:515 –517 University of Michigan, RIs from 21 hydronephrotic kidneys were obtained before nephrostomy. The mean RI in 14 kidneys with confirmed obstruction (0.77 ± 0.04) was significantly higher than the mean RI from seven kidneys with nonobstructive pelvicaliectasis (0.64 ± 0.04). Moreover, RI values returned to normal after nephrostomy. The obstruction may be significant and demands surgical intervention when the resistive index reaches 0.7 Platt J, Rubin J, Ellis J. Acute renal obstruction: evaluation with intrarenal duplex Doppler and conventional US. Radiology 1993; 186:685 –688 To evaluate duplex Doppler ultrasound (US) in acute renal obstruction, bilateral intrarenal Doppler US was performed in 23 patients with unilateral renal obstruction (proved by means of intravenous urography) of 36 hours duration or less. A mean renal resistive index (RI) was calculated for each obstructed and normal contralateral kidney and compared with findings on conventional US scans. The mean RI in the obstructed kidneys was elevated (.77 +/- .07 [standard deviation]) and was higher than the mean RI in the normal contralateral kidney (.60 +/- .04) (P < .001). RIs in the obstructed kidneys were as follows: .75 or greater in 15 kidneys, .70-.74 (mild RI elevation) in five kidneys (but > or = .10 higher than the RI in the normal contralateral kidney), and less than .70 in three kidneys (two of these three patients had pyelosinus extravasation and one patient had clinical obstruction for only 4-5 hours). RI elevation occurred before collecting-system dilatation in four patients (17%). RI elevation occurs by 6 hours of clinical acute renal obstruction and may precede pyelocaliectasis. Renal duplex Doppler US contributes useful clinical information, especially when US is the first modality used to evaluate acute renal colic. Abstract Introduction: The objective of this study was to determine whether the renal resistiveindex (RI) can predict hydronephrosis in patients with renal colic (RC) and whether or not its performance is time-dependent. Materials and methods: The study population was composed of 54 patients admitted for unilateral RC. At the time of the first observation (time point I, tpI), each patient underwent routine examinations, abdominal ultrasonography, and renal color Doppler ultrasound (CDUS)with measurement of the RI. The two imaging studies were repeated 6, 12, 18, 24, 36, and 48 h later (tpII, tpIII, tpIV, tpV, tpVI, tpVII). In addition, each patient underwent noncontrast urinary tract CT 48-60 h after admission. A mean renal RI of >0.70 (mRIþ) for the symptomatic kidney was considered indicative of obstruction. Patients were retrospectively divided into two groups: those who developed dilatation (group A) and those who did not(group B). No. of cases of Hydronephrosis Group A (Dilatation developed) Time point No. cases hydronephrosis % cases hydronephrosis Admission 0 0 6 hours 0 0 12 hours 3/54 5.5 18 hours 14/54 25.9 24 hours 10/54 18.5 36 hours 2/54 3.7 48 hours 0 0 Total 29/54 53.7% Number of RI +ve cases Group A No. of cases Hrs before hydronephrosis Group B No. of cases Admission 0 0 - At 6 hours 7/29 (24%) 1 case – 18h 4/25 (16%) 12 cases-12h At 12 hours 16/29 (55.1%) 5 cases-12h 0 11 caes-6h At 18 hours 5/29 (17.2%) 1 case – 18h 0 4 cases-6h At 24hours 1/29 (3.4%) 1 case – 6h 0 At 36 + 48 hours 0 0 0 Total 29/29 (100%) 2/29-18hrs(6.9%) 4/25 (16%) 8/29- 12hrs(27.6%) 19/29- 6hrs(65.5%) Nonobstructive Renal Disease Pre-renal and Renal causes of AKI The lack of specificity of the gray-scale examination in evaluating intrinsic renal disease has been frustrating for decades. • Renal size •Cortical thickness •Echogenicity These findings do not aid in the differential diagnosis or management of renal disease; they are not objective. • Platt J, Ellis J, Rubin J, DiPietro MA, Sedman AB. Intrarenal arterial Doppler sonography in patients with nonobstructive renal disease: correlation of resistive index with biopsy findings. AJR 1990; 154:1223 –1227 • Mostbeck G, Kain R, Mallek R, et al. Duplex Doppler sonography in renal parenchymal disease; histopathologic correlation. J Ultrasound Med 1991; 10:189 –194 • McDermott R, Teefey S, Middleton W, et al. The resistive index in renal parenchymal disease: no correlation with histopathologic findings. (abstr) Radiology 2000; 217(P):560 Is there a role for RIs? Platt J, Rubin J, Ellis J. Acute renal failure: possible role of duplex Doppler US in distinction between acute prerenal failure and acute tubular necrosis. Radiology 1991; 179:419 –423 Ultrasonography (US) of the native kidneys is commonly requested for acute renal failure (ARF), although in most cases the examination results are negative. 91 patients with ARF were studied to determine a mean resistive index (RI) for each patient. Forty-six patients had acute tubular necrosis (ATN) with a mean RI +/- 1 standard deviation of .85 +/- .06, which was significantly higher than the mean RI of .67 +/- .09 in 30 patients with prerenal ARF (P less than .01). Relieving Obstruction Refer all adults, children and young people with upper tract urological obstruction to a urologist. Refer immediately when one or more of the following is present: •pyonephrosis •an obstructed solitary kidney •bilateral upper urinary tract obstruction •acute kidney injury caused by urological obstruction. • when nephrostomy or stenting is used to treat upper tract urological obstruction in adults, children and young people with acute kidney injury, undertake as soon as possible and within 12 hours of diagnosis. Acute kidney injury. NICE clinical guideline 169 (2013) Case 3- AKI ?cause A. RIs(inspired by BMUS) B. Advise immediate referral to Urologist C. NICE Standards recommend Nephrostomy within 24 hours D. All of above Case 4- AKI a — I ame) am iP) recision ae nr? BLADDER I Hull and East Yorkshire Hospitals NHS Dimes  Diagnosic criteria Detect acute kidney injury by using any of the following criteria: •a rise in serum creatinine of 26 micro mol/l or greater within 48 hours •a 50% or greater rise in serum creatinine known or presumed to have occurred within the past 7 days •a fall in urine output to less than 0.5 ml/kg/hour for more than 6 hours in adults and more than 8 hours in children and young people •a 25% or greater fall in eGFR in children and young people within the past 7 days.