July Case #1: Flank Pain

80 y/o WF presents to the ED with left flank pain for 1 day.  Her pain has been constant and she denies dysuria, frequency or hematuria.  Denies N/V/D.
PMHx: HTN
PSHx: pacemaker
All: NKDA
SocHx: occ ETOH, denies tob or  drugs

PE: BP 132/64, P 70, R 16, T 98.0, Pox 99% (RA)
GEN:  WNWD, WF, NAD
CHEST: CTA B, non labored
CV: RRR, no M/R/G
ABD: soft, NTND, +BS
GU: L CVAT

Bedside US is performed:

 

What is the diagnosis?
What is the color doppler artifact noted and how does it occur?

Special thanks to Guest Presenter: Dr. Sarah Bogle!