Renal Ultrasound Unwarranted for AKI Evaluation

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SAN DIEGO—Routine use of renal ultrasound may be inappropriate for evaluating hospitalized patients with acute kidney injury (AKI), and a simple electronic alerting system may provide an early warning of rising creatinine levels, according to separate studies presented at Kidney Week 2012.

Renal ultrasound frequently is used to look for obstructive uropathy, but a study by Dipal Patel, MD, a third-year internal medicine resident at Mount Sinai Hospital in Chicago, and colleagues showed this to be a rare cause of AKI. In addition, the study showed that renal ultrasound did not provide meaningful information that affected patient management.

“We did this study because there are not much data on this issue and whether it [renal ultrasound] is really useful or not,” Dr. Patel said. “There is a waste of money and a waste of time and it may lead to longer hospitalization. We found there was fewer than 5% that had obstructive uropathy.”

The study included 1,121 AKI patients older than 18 years. The study excluded pregnant women and patients who had a kidney transplant. The researchers collected data on the patient's medical history, which was taken at the time of presentation. They also collected data on patient demographics (age, sex, and race), serum creatinine, and PSA level. The researchers identified from the patients' past medical history the presence of medical problems known to cause obstructive uropathy (benign prostatic hyperplasia, abdominal or pelvic surgery, pelvic malignancy, and nephrolithiasis).

The investigators identified patients who had a positive renal ultrasound, which they defined as the presence of bilateral hydronephrosis and compared these patients with those who had a negative ultrasound.

During the six year study period, 5,010 patients underwent renal ultrasound; of these, 1,121 met study inclusion criteria. Their mean age was 62 years, 53.8% were male, and 73.5% were African American. Sixty-two patients (5.5%) had a positive renal ultrasound; of these, 43 (69% were male and their mean age was 65 years.

Of the 62 patients, 28 (45%) presented with symptoms of urinary retention and 47 (76%) had risk factors for obstructive uropathy. Elevated PSA levels, male gender, and medical problems known to cause obstructive uropathy were associated with a positive renal ultrasound.

The researchers concluded that renal ultrasound should be reserved for patients who have a higher likelihood of obstructive uropathy based on their medical history.

Electronic alerts prove helpful

In a separate pilot study, British researchers demonstrated the potential benefits of using a 24-hour electronic alerting system. It could provide a simple approach to the early identification of patients experiencing a rise in creatinine following hospitalization. The electronic notification system also appears to provide a gateway for standardizing clinical guidance for AKI management.

“We need a new tool,” said lead investigator Edward Stern, MD, of the Royal Free Hospital Centre for Nephrology in London. “Anything that is a stimulus for a small percentage of clinicians to think about the change in a patients' creatinine more quickly is very important. It may not revolutionize our management, but it is a small part in this attempt to augment the physicians' awareness of a patient's change in creatinine and what the significance may be.”

AKI is associated with a significantly increased risk of death in hospitalized patients, Dr. Stern noted. Delays in identifying significant relative rises in creatinine, which may be small in absolute terms are known to contribute to mortality.

He and his colleagues designed an automated rule for the hospitals' electronic pathology systems. If the systems identified patients with a creatinine rise of 50% or more from the previous value (within 90 days), an electronic alert was posted on the pathology report. The report identified the patient as having AKI and provided a link to the London AKI Network website, which provided relevant clinical guidelines. The biochemistry team used its discretion to subsequently telephone requesting clinicians.

Dr. Stern and his team collected data for the first 100 adult patients identified by the electronic alerting system. The group consisted of 86 inpatients, seven hospital outpatients, and seven community general practitioner patients. The mean rise in serum creatinine was 1.27 mg/dL (130%). The median time from baseline to creatinine alert was 20 days.

The investigators divided the patients by KDIGO [Kidney Disease: Improving Global Outcomes] stage and found that 56 patients had AKI stage 1, 29 had AKI stage 2, and 15 had AKI stage 3.  Fifteen patients died within the 42-day study period (five with AKI stage 1, eight with AKI 2, and two AKI stage 3).

The program was easy to establish and implement, Dr. Stern said. It facilitated early identification of patients with an unmet clinical need. Post-operative AKI was identified and managed early and clinicians were able to identify a number of unexpected AKI cases among samples sent by community general practitioners.

The system already has been extended to five hospitals in North London. “It takes just five minutes to set up and we hope it is changing the way people think about AKI in our region,” Dr. Stern said.

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