CT Scan Prior to Admission for UPJ Stone with Obstruction

Importance of CT Scan in Surgical Planning

Ultrasound has only 24-57% overall sensitivity for detecting renal calculi compared to CT, with particular difficulty characterizing stone burden and exact anatomic location, according to the American College of Radiology 1, 2.
The American College of Radiology recommends CT abdomen and pelvis with or without IV contrast for patients with a history of renal stones or renal obstruction, rating it as "usually appropriate" 3.
CT definitively measures stone size and density, which determines whether ureteroscopy, shock wave lithotripsy, or percutaneous nephrolithotomy is most appropriate, as suggested by the American College of Radiology 2.
For a UPJ stone, CT is necessary to determine if there are additional stones in the collecting system that would change the surgical approach, according to the American College of Radiology 1, 4.

The European Association of Urology guidelines emphasize that prompt differentiation between uncomplicated and potentially obstructive pyelonephritis is crucial, as obstruction with infection can rapidly progress to urosepsis 5.
If the patient remains febrile or clinically deteriorates, contrast-enhanced CT should be performed immediately to rule out pyonephrosis or perinephric abscess, as recommended by the European Association of Urology 5.

The American College of Radiology recommends obtaining CT abdomen and pelvis without IV contrast initially, as it is the reference standard with 97% sensitivity for detecting stones 1, 4.
Add IV contrast only if there is clinical suspicion of infection, fever, or concern for complications such as abscess or calyceal rupture, according to the American College of Radiology and the European Association of Urology 3, 5.

If the patient has signs of infection, obtain CT with IV contrast immediately to evaluate for pyonephrosis or perinephric abscess, as recommended by the American College of Radiology and the European Association of Urology 3, 5.
If the patient is pregnant, use MRI without IV contrast instead of CT to avoid radiation exposure while still obtaining superior anatomic detail compared to ultrasound, as suggested by the European Association of Urology and the American Urological Association 5, 6, 7.