Urinary Tract Infection - Diagnosis

Imaging Techniques

Because of the expense and the limited accuracy of imaging procedures, these techniques are used only for the following:

Serious and recurrent cases of pyelonephritis.
When structural abnormalities are suspected.
If infections do not respond to treatment.
If a doctor suspects obstruction or an abscess.
After a first urinary tract infection in children two to 24 months to detect possible obstruction or vesicoureteral reflux. Tests include ultrasound and a voiding cystourethrogram and possibly scans. Some evidence suggests that ultrasound is probably not necessary, but at this time it is recommended by major medical groups.

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Ultrasound. Ultrasound is a noninvasive, risk-free imaging test that can be used to screen for hydronephrosis (obstructions of the flow of urine), kidney stones that predispose to infection, and kidney abscesses. In men, ultrasound can detect enlargement or abscesses of the prostate and, when combined with x-rays, is an accurate method for detecting incomplete emptying of the bladder, a common cause of UTI in men over 50. In children with urinary tract infections, they also can be used to detect vesicoureteral reflux, the defect of the valve-like mechanism between the ureter and bladder. They are not as accurate as voiding cystourethrograms.

Nuclear Scans. Imaging techniques called nuclear scans may be useful in certain complicated cases, such as detecting kidney scarring after pyelonephritis in children. They produce better images and expose the patient to far less radiation than x-rays do. One such scan called dimercaptosuccinic acid (DMSA) scintigraphy first employs injections of tiny amounts of radioactive tracing medicine. A scanning machine (scintillation or gamma camera) is then used to detect pictures of the tracer in the kidney. This information is recorded on a computer screen or on film.

Magnetic Resonance Imaging (MRI) or Computed Tomography (CT). Magnetic resonance imaging (MRI) and computed tomography (CT) scans are noninvasive advanced imaging techniques that are sometimes used when nuclear scans are inconclusive. A CT scan is useful for ruling out kidney stones or obstructions in women with recurrent UTIs.

X-Rays. Special x-rays can be used to screen for structural abnormalities, urethral narrowing, or incomplete emptying of the bladder, which can cause stagnation of urine and predispose to infection.

Voiding cystourethrogram is an x-ray of the bladder and urethra. To obtain a cystourethrogram, a dye, called contrast material, is injected through a catheter inserted into the urethra and passed through the bladder.
An intravenous pyelogram (IVP) is an x-ray of the kidney. For a pyelogram, the contrast matter is injected into a vein and eliminated by the kidneys. In both cases, the dye passes through the urinary tract and reveals any obstructions or abnormalities on x-ray images. Due to the possible risks to the fetus, x-rays are not performed on pregnant women.