KUB (kidneys, ureters, bladder) is a plain abdominal X‑ray and typically uses no contrast agent. It visualises radiopaque stones, bowel gas, calcifications and some foreign bodies. If more detailed urinary tract imaging is required, contrast studies are performed instead — typically iodinated intravenous contrast for IV/CT urography or iodinated intravesical contrast for cystography.

MRI scans typically use gadolinium-based contrast agents (GBCAs) injected intravenously. Gadolinium is paramagnetic and shortens tissue T1 relaxation times, improving visualization of blood vessels, inflammation, tumors, and areas with blood–brain barrier breakdown. Allergic reactions are uncommon, but GBCAs are used cautiously in severe kidney impairment due to a rare risk of nephrogenic systemic fibrosis; macrocyclic agents are often preferred.

The full form of KUB MRI is "Kidney–Ureter–Bladder Magnetic Resonance Imaging" — an MRI study focused on the kidneys, ureters and urinary bladder. It provides detailed soft‑tissue images to evaluate anatomy and pathology such as masses, congenital anomalies, obstruction, infection or inflammation. MRI is useful when avoiding ionizing radiation, though CT is generally better for detecting calcified stones.

MRI of the kidneys can be done with or without contrast. Non-contrast MRI (including MR urography and diffusion imaging) assesses anatomy, obstruction and some lesion features. Gadolinium-enhanced MRI gives better lesion characterization, vascular detail and perfusion data. Contrast is chosen based on the clinical question and is used cautiously or avoided in patients with severe renal impairment (low eGFR).

A KUB is an abdominal radiograph that images the Kidneys, Ureters, and Bladder. It’s used to assess urinary tract stones, their size and position, bowel gas patterns, and some abdominal calcifications. Often performed with other tests, it can help identify obstruction, large renal stones, or foreign bodies but has limited sensitivity for small stones and soft-tissue detail, so further imaging may be needed.

A contrast scan of the kidneys is an imaging test—usually CT or MRI—where a contrast dye is injected to highlight renal anatomy, blood vessels and the urinary tract. It helps detect stones, tumors, infections, blockages and assess kidney function. Preparation includes checking kidney function and allergy history. Side effects are usually mild (warmth, nausea); rare risks include allergic reactions or contrast-related kidney injury.