Evaluation of acute kidney injury among hospitalized patients

AKI: acute kidney injury; ATN: acute tubular necrosis; BUN: blood urea nitrogen; CT: computed tomography; GFR: glomerular filtration rate; SPEP: serum protein electrophoresis; UPEP: urine protein electrophoresis.

* Refer to UpToDate content on evaluation of AKI among hospitalized adult patients for details.

¶ We obtain a spot urine protein-to-creatinine ratio or albumin-to-creatinine ratio. For patients who are >40 years of age and have no other obvious cause for AKI, we also obtain SPEP with immunofixation, UPEP with immunofixation, and a serum free light chain assay to evaluate for multiple myeloma/cast nephropathy.

Δ We typically use kidney ultrasound to evaluate for obstruction. However, helical CT scan without contrast is generally preferred among patients with suspected urolithiasis. For older males, in whom benign prostatic hyperplasia and concomitant bladder outlet obstruction are common, post-void bladder ultrasound is a reasonable initial imaging modality. However, the lack of urinary retention on bladder scan does not rule out upper urinary tract obstruction.