Emergency Body CT > Renal Colic

Renal Colic

The CT scan protocol can be optimized to evaluate renal or ureteral stones, a common cause of flank pain. This scan is typically performed without IV or oral contrast. The kidneys, ureters, and bladder are scanned in overlapping 5 mm sections. Almost all renal and ureteral stones are detectable using this method.
Occasionally the ureters cannot be followed throughout their entire length and the difficulty of distinguishing a ureteral stone from a phlebolith (a calcified thrombosed pelvic vein) then arises. Secondary signs of an obstructing ureteral stone can be helpful in making this distinction. Such secondary signs include:

1. Hydronephrosis and perinephric stranding on the involved side
2. The "rim sign"- a soft tissue rim around a pelvic calcification may also be seen, and represents the edematous ureter surrounding a stone

The complete absence of these secondary signs makes it unlikely (approximately 5-8% chance) that a pelvic calcification actually represents a stone. In cases where the distinction still cannot be made with certainty, IV contrast may be given and images through the ureters obtained following a 5-10 minute delay. This will opacify the ureters and reveal whether the suspect calcification lies within or outside the ureter.

Renal stone (arrow) right sided hydronephrosis (arrowhead)

Distal ureteral stone (arrow) leading to right
hyrdronephrosis in above image

Ureteral junctional stone (arrow)

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