Urinary tract stone, urinary calculous disease, nephrolithiasis, ureterolithiasis, vesicolithiasis

Macroscopic concretions of crystals in urinary system, sometimes mixed with proteins

US has 96% sensitivity, nearly 100% specificity for renal stones > 5 mm

US is valuable for follow-up imaging, particularly in patients with renal colic & known renal stones or patients not improving on treatment for known stone

Virtually all stones are visible (including those radiolucent on KUB) on CT except pure matrix stones & protease inhibitor stones (e.g., indinavir, treatment of HIV)

NECT is preferred imaging modality to confirm stone in adult patients with acute flank pain

• ○
  

  Most accurate measurement technique on CT: Bone windows & magnification

Choice of imaging modality follow-up is often based on visibility of stone on CT scout image

In patients with BMI < 30, consider low-dose CT

Dual-energy CT can differentiate urate stones from other types of stones with high accuracy

Milk of calcium in small cyst

Arterial calcifications

Nephrocalcinosis

Emphysematous pyelonephritis

Dependent on type of stone

Size, number, location, evidence of obstruction or infection, & relevant anatomic findings (aberrant vasculature, distorted pelvicalyceal architecture, infundibular orientation) are all imaging findings that impact treatment

US protocol: Drink 16-32 oz water prior to examination to fill bladder

Always include bladder with special attention to UVJ

Twinkling artifact on color Doppler is useful to identify otherwise occult stone; more sensitive than acoustic shadowing but higher false-positive rate