Methods:
A retrospective analysis of renal US were obtained from January 2016 to March 2016 with the ‘request diagnoses’ of AKI. AKI cases related to renal transplant, tumor lysis syndrome, interstitial nephritis and rhabdomyolysis cases were excluded.
Manual review of electronic records was undertaken to evaluate the diagnostic yield of Ultrasound with the considerations of (1) abnormal US findings (2) whether an abnormal result affected the AKI diagnosis or management in terms of procedural intervention or subsequent investigations conducted.
Results:
There were 111 AKI related US requests over the 3 month period. 61 cases showed medical renal disease and 36 cases were non diagnostic. There were 4 cases in which only the bladder was found to be distended.
A total of 10 hydronephrosis cases were found; 4 cases were established obstructive uropathy cases in which the US was done post nephrostomy. Four cases of unilateral hydronephrosis were related to nephrolithiasis and/ or stent exchange. One case of bilateral hydronephrosis was related to bladder distension that was picked up on a bedside bladder scan prior to US, clincial chart review revealed that the patient had established Benign Prostatic Hyperplasia (BPH) not on medications; the US findings led to intermittent self catheterisation and the patient was started on alpha blockers.
In one case of AKI the US was reported as unilateral pelvic prominence; clincial chart review did not reval any obvious cause and the US findings did not lead to further investigation or intevention, it was contemplated it could be due to a recent passage of a calculus.
Incidental findings of renal cysts and masses not related to AKI were found in around 15 cases which led to further investigations. Almost all AKI got better with simple medical management, the major etiologies for AKI in our study were ATN from sepsis and pre-renal azotemia.
Conclusions:
US in the cases of AKI even when abnormal has limited clinical utility and is is probably one of the ‘Things We Do For No Reason’!
Diagnostic testing should be based on both ‘pre-test probability’ from the clinical context as well as an appreciation of the diagnostic value and actionability of the data provided by the test.
We propose the following indications of US in pure AKI cases:
- History of Hydronephrosis
- Urological procedures
- History of Malignancy
- Elderly males (>75 years), patients on prostatic medications and bedside bladder scanning showing retention on admission
- No improvement in AKI parameters after 24 hours of targeted resuscitation.
