From the Guidelines
To order a KUB (Kidney, Ureter, Bladder) radiography, it is generally recommended to use it in combination with other imaging modalities, such as US, for the initial or follow-up imaging of patients with acute onset flank pain and suspicion of stone disease, particularly in pregnant patients or when CT is not readily available 1. When ordering a KUB, it is essential to consider the patient's medical history, current symptoms, and the potential benefits and limitations of the examination.
- The KUB procedure is quick and painless, involving a single X-ray image of the abdominal area while the patient lies still on an examination table.
- Before the examination, the patient may be asked to fast for a few hours, though specific preparation instructions vary by facility.
- The patient should wear comfortable clothing without metal objects, as they may need to change into a hospital gown.
- KUB radiography helps visualize the urinary system and surrounding abdominal structures, allowing doctors to detect kidney stones, abnormal gas patterns, foreign bodies, or certain types of bowel obstructions.
- Results are typically available within 1-2 days and will be interpreted by a radiologist before being shared with the referring physician.
- According to the American College of Radiology, the use of KUB may be appropriate in certain scenarios, such as in pregnant patients or when CT is not readily available 1.
- A study published in the Journal of the American College of Radiology found that combining US findings with complementary KUB improved the sensitivity for urolithiasis and had acceptable specificity when compared with either modality alone 1.
- However, it is crucial to note that CT is more sensitive for obstructive urolithiasis, and KUB may have limited sensitivity and specificity for detecting ureteral calculi 1.
- Therefore, the decision to order a KUB should be made on a case-by-case basis, taking into account the patient's individual needs and the availability of other imaging modalities 1.
From the Research
Ordering a KUB (Kidneys, Ureters, and Bladder) Scan
To order a KUB scan, the following steps can be considered:
- The patient's symptoms and medical history should be evaluated to determine the necessity of a KUB scan 2, 3, 4, 5.
- Non-contrast enhanced computed tomography of kidneys, ureters, and bladder (CT KUB) is the gold standard radiological imaging for nephrolithiasis and can be used as the first line investigation in suspected upper urinary tract obstruction 6, 2.
- The cranial extent of the CT KUB scan can be limited to the T10 vertebral level to reduce radiation exposure while maintaining adequate diagnostic utility 6.
- Urinalysis and patient history of urolithiasis can be used to decide between contrast-enhanced or noncontrast CT for renal colic 5.
- In cases where the patient has no history of urolithiasis and a negative urinalysis, a contrast-enhanced CT may be more appropriate to rule out alternative diagnoses 5.
Key Considerations
- Radiation exposure is a major limitation of CT KUB scans, and efforts should be made to minimize it 6, 2.
- The sensitivity and specificity of CT KUB scans are extremely high in the diagnosis of stones, but other imaging modalities such as ultrasound and plain radiography can also be used 2, 3.
- Alternative diagnoses such as Page kidney should be considered in patients presenting with flank pain and hematuria 4.