Which X‑ray should be ordered for a patient with right lower abdominal pain above the bladder, tenderness on palpation, and dysuria?

Imaging for Right Lower Abdominal Pain with Dysuria

Do not order a plain X-ray (KUB) for this patient—CT abdomen and pelvis without IV contrast is the appropriate initial imaging study. 1, 2

Why CT Without Contrast is the Correct Choice

This clinical presentation—right lower abdominal pain above the bladder with tenderness and dysuria—strongly suggests urolithiasis (kidney/ureteral stone) as the primary diagnostic consideration. 1

CT abdomen and pelvis without IV contrast is the gold standard for suspected urinary tract stones, with sensitivity and specificity approaching 100% for detecting calculi. 1, 2 This imaging modality will simultaneously evaluate for:

• Urolithiasis (most likely diagnosis given dysuria and location) 1
• Hydronephrosis indicating obstruction 1
• Alternative diagnoses including appendicitis, diverticulitis, or gynecologic pathology 1

Why Plain X-Ray (KUB) is Inadequate

KUB radiography has unacceptably poor diagnostic performance for this clinical scenario:

• Sensitivity for ureteral calculi is only 53-62% 2
• Specificity is only 67-69% 2
• Particularly insensitive for stones <4mm and mid/distal ureteral stones 2
• Cannot identify the cause or site of obstruction 2
• The American College of Radiology explicitly states KUB should not be used as the initial imaging test for suspected urinary tract stones 2

Even though 90% of stones are radio-opaque, KUB still misses the majority of clinically significant pathology. 2 In one study comparing KUB to CT, **KUB detected only 8% of stones <5mm**, though detection improved to 78% for stones >5mm. 2

Clinical Algorithm

For this patient with right lower abdominal pain, suprapubic tenderness, and dysuria:

1. Order CT abdomen and pelvis without IV contrast immediately 1, 2
2. If CT is unavailable or contraindicated (pregnancy, contrast allergy concerns are irrelevant here since no contrast is needed), ultrasound of kidneys and bladder is the alternative—not KUB 1, 2
3. If ultrasound shows hydronephrosis but no definitive stone, CT remains necessary for definitive diagnosis 1

Important Clinical Caveats

Do not be misled by the location "above the bladder"—this does not change the imaging approach. Right lower quadrant pain with dysuria indicates urinary tract pathology until proven otherwise, and CT without contrast remains the appropriate study. 1

Avoid the common pitfall of ordering KUB first "to save radiation"—this strategy actually increases total radiation exposure when the inevitable follow-up CT is needed after the non-diagnostic KUB. 3 Studies demonstrate that up to 50% of patients with suspected stone disease do not have stones, and preliminary KUB radiographs subject these patients to unnecessary radiation with no diagnostic benefit. 3

If the patient is female of reproductive age, consider pelvic ultrasound as an adjunct if gynecologic pathology (ovarian torsion, ectopic pregnancy, tubo-ovarian abscess) is in the differential, but this does not replace the need for CT evaluation of the urinary tract. 1

In pregnant patients specifically, ultrasound becomes the initial imaging modality, but this is the only exception to the CT-first approach. 1