Introduction
This topic covers the imaging methods for the urinary tract (ultrasound, plain radiography, excretory urography/IVP, CT, MRI and interventional methods): what each shows, how to use them and when to choose which. A GU imaging study is done for neoplasm, infection, stone disease and trauma; haematuria is the sign of possible cancer in the urinary system.
Diagnostic methods
Ultrasound
- Method of choice. No ionizing radiation; used to avoid radiation, and can be used for screening, in pregnant women, children and patients with renal insufficiency.
- Assesses shape, size, topic (position) and perfusion of the kidneys; evaluates the renal parenchyma, pararenal structures and tumours; detects hydronephrosis and stones.
- Distinguishes solid from cystic lesions; excellent for distinguishing cysts from solids (malignancy); confirms a renal mass as a cyst and confirms hydronephrosis.
- Low information value for lymph nodes and no value for staging renal carcinomas.
- Varieties of the kidney that do not affect organ function are also examined by US. The second US shows the bladder in sagittal view and then in transverse view (left to right).
Plain radiography
- Detects stones and calcifications and can also assess the psoas muscle. Patients with well-developed perirenal adipose tissue allow better assessment of the kidneys.
- The X-ray shows normal kidneys, ureters and bladder.
Excretory urography (intravenous pyelogram / urogram, IVP)
- Intravenous administration of iodinated contrast; a relatively sensitive method. Urea, creatinine and allergic reactions are checked first.
- Assesses renal function (cortical function), topic and size of the kidneys, the collecting system, ureters and urinary bladder. Shows congenital abnormalities, hydronephrosis and filling defects in the pyelocalyceal system.
- Advantage: quick, accurate and detailed assessment of renal anatomy. Cysts and tumours are better evaluated by CT; cross-sectional techniques are preferred when a renal mass is suspected, especially if peripheral.
- Phases: the contrast fills the renal arteries 1-3 min after injection; 5-7 min is the nephrographic phase with visualisation of the parenchyma; at 15 min is the excretory phase (by glomerular filtration), which visualises the renal collecting system. If excretion is delayed, the intervals increase.
- How to evaluate: give contrast and obtain radiographs at about 1, 3, 5 and 10 min, watching the opacities of contrast move from one part to the next over time. If there is obstruction, no opacities form distal to it.
Late phase of excretion: the renal pelvis and calyces of the kidneys, the two ureters and the bladder are seen; all are normal.