Following on from our previous post, how can PoCUS be incorporated into the assessment of flank pain. In many cases, the default investigation is CT. Whilst this has excellent diagnostic performance it also exposes many, often relatively young patients, to significant radiation.
Cox et al describe the use of ultrasound in the assessment of this patient group, with a systematic assessment of the aorta, kidneys and bladder to elucidate a cause of the patient's symptoms. They go on to describe a ultrasound based protocol for the assessment of patients with suspected ureteric colic.
The NEJM paper they reference comparing ultrasound to CT scanning in the investigation of nephrolithiasis can be found here. This showed a reduction in radiation exposure with no significant change in adverse outcomes through the use of a ultrasound based assessment.
Cox C, MacDonald S, Henneberry R, Atkinson PR. My patient has abdominal and flank pain: Identifying renal causes. Ultrasound. 2015; 23(4):242-50.
Smith-Bindman R, Aubin C, Bailitz J, et al. Ultrasound versus CT for suspected nephrolithiasis. New Eng J Med 2014; 371: 1100–10.
If you can do a FAST exam you already know how to locate the kidneys with ultrasound. Assessing for hydronephrosis often relatively straightforward and this 8 minutes video from SonoSite with show you the basics. This is a useful skill to have for patients with acute renal failure or when you are trying to find a potential source of sepsis.
Just remember that congenital abnormalities of the kidneys are relatively common. Unilateral renal agenesis may be present in up to 1 in 500 live births, so if you can't find the kidney there is a chance it might no be there.