From the Guidelines
The KUB X-ray is a diagnostic imaging test that provides a two-dimensional view of the abdominopelvic region, and it is particularly useful for detecting radio-opaque kidney stones, abnormal calcifications, bowel gas patterns suggestive of obstruction, and some foreign bodies. The test uses ionizing radiation to create images of dense structures like bones and calcifications, making it a valuable tool in evaluating patients for kidney stones, bowel obstruction, constipation, or foreign body ingestion 1.
Key Findings of KUB X-ray
- Detects radio-opaque kidney stones, which account for about 90% of all stones, including calcium oxalate, calcium phosphate, and struvite stones 1
- Identifies abnormal calcifications, which can be indicative of various conditions such as kidney stones or other pathologies
- Visualizes bowel gas patterns, which can suggest obstruction or other gastrointestinal issues
- Detects some foreign bodies, particularly those that are radio-opaque
Limitations of KUB X-ray
- Cannot visualize soft tissues well, which may limit its ability to detect certain conditions such as radiolucent stones or other soft tissue pathologies 1
- May miss radiolucent stones or other conditions requiring contrast, highlighting the need for additional imaging modalities in some cases
- Has limited sensitivity for detecting ureteral calculi, with a sensitivity range of 53% to 62% and specificity of 67% to 69% 1
Clinical Use of KUB X-ray
- Often used as an initial screening tool before more advanced imaging like CT scans or ultrasounds are ordered, particularly in emergency settings where quick assessment is needed 1
- Can be used in combination with other imaging modalities, such as ultrasound, to improve detection rates for certain conditions like urolithiasis 1
- May be used to monitor patients with known kidney stones or other conditions, allowing for quick and non-invasive assessment of the abdominopelvic region 1
From the Research
Findings of an Abdominopelvic X-ray
The findings of an Abdominopelvic X-ray, specifically a Kidneys, Ureters, and Bladder (KUB) X-ray, can vary depending on the presence and location of stones, as well as other factors.
- The KUB X-ray can detect radiopaque stones, but may miss radiolucent stones or smaller stones in certain locations 2, 3, 4, 5, 6.
- Studies have shown that the sensitivity of KUB X-ray for detecting renal stones is around 81% 3, while the sensitivity for detecting ureteric stones is lower, around 45-77% 3, 6.
- The use of ultrasound in combination with KUB X-ray can increase the sensitivity for detecting stones, particularly in patients with renal failure 3.
- Computed Tomography (CT) scans, including CT planning images and scout films, can also be used to detect stones and may be more sensitive than KUB X-ray for certain types of stones 2, 5, 6.
- Factors such as stone size, location, and Hounsfield units (HU) can affect the visibility of stones on KUB X-ray and CT scans 5.
Comparison of KUB X-ray and Other Imaging Modalities
- KUB X-ray and CT scout films have been compared for their ability to detect urinary tract stones, with CT scout films detecting around 75% of stones visible on KUB X-ray 6.
- Ultrasound has been shown to be sensitive and specific for renal stones, but less sensitive for ureteric stones 3, 4.
- CT scans, including ultra-low-dose CT, have been shown to be effective for detecting small and distal ureteral stones that may be missed by KUB X-ray or ultrasound 2.