Suspected renal stone. Flank pain.

While stones can be seen on CT with IV contrast, essentially all stones are visible on CT without contrast. If high clinical suspicion of stone, no IV contrast needed. Other etiologies such as diverticulitis and appendicitis can be seen too.

consider xray or limited IVP in pregnant patients, but ultrasound can be useful to detect hydronephrosis. Xray not nearly as sensitive as CT for stone detection. MRI can detect hydro and possible level of obstuction, but expensive and insensitive.