Imaging of Urinary System

Imaging of Urinary System. Dr. Dilgash Hameed Ahmad M.Sc. Diagnostic Radiology.

Outline. Imaging modalities in Radiology Radiological terms Imaging modalities of urinary system Radiological anatomy of urinary system.

Learning objectives. Be familiar with the imaging techniques used in evaluating the urinary system. Be familiar with the normal radiological appearances of different urinary tract structures. Be able to identify urinary tract structures on different imaging modalities..

Imaging Modalities of Radiology. Conventional radiography (X-ray) Ultrasound Computed Tomography (CT scan) Magnetic Resonance Imaging (MRI) Fluoroscopy Angiography.

Radiological Terms. X-ray – density Ultrasound – echogenicity Hypoechoic Hyperechoic Isoechoic Echogenic Anechoic.

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US: Ultrasound First-line investigation in most patients. Safe , no risk of radiation. Uses of US: Assesses the size, shape, location, and blood flow to the kidneys (assesses blood flow to the kidneys using doplar ultrasound using color ultrasound) . Assesses the prostate gland in males. Detects stones, hydronephrosis and hydroureter , cysts, solid masses, infective changes..

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KUB: Kidneys, Ureters, Bladder Rapid plain x-ray but has risk of radiation exposure. Uses of KUB: General evaluation mainly for stones; also detects calcifications. May show soft tissue shadows (psoas abscess). Assess bones. Assess site of drains or stents..

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IVU: Intravenous urography Timed series of x-ray images of the urinary tract after administration of IV contrast agent. Gives detailed information about the pelvicalyceal system (PCS) and ureters . Indications: To assess patients with anatomic variations or congenital anomalies. Acute ureteric colic, stones, and hematuria..

Phases of IVU. Nephrogram –1-3 minutes Pyelographic – 10-15 minutes Ureterogram – 30 minutes Cystogram – 45 minutes Post-void.

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CT scan: Computed Tomography Indications : Evaluation of masses Staging of tumors Diagnosis or exclusion of renal trauma Demonstration of radiolucent stones Delineation ( رسم ) of renal vascular anatomy In some centers, to assess acute ureteric obstruction.

Other imaging modalities. Used in selected cases….. MRI & MRA: Magnetic Resonance Imaging & Angiography Clarify problems not solved by US or CT Reserved mainly for vascular problems (renal artery stenosis, venous extension in tumor, vasculature before surgery). Antegrade & Retrograde Pyelography Reserved for cases where less invasive procedures failed to reach diagnosis especially in obstruction. Cystography, Urethrography & Micturating Cystourethrography (MCUG) Used mainly in reflux. Urethral abnormalities (stricture, valve). Functional bladder diseases..

Radiological Anatomy of Urinary System.

Kidneys. KUB: Soft tissue density with lucent outlines (due to perirenal fat) . Renal size: range from 10-15 cm , left is usually larger. US: Renal outline is normally smooth. Size: smaller than on KUB, 9-12 cm . Renal cortex (parenchyma) appears darker than the renal sinus (fat, calyces, infundibula, and vessels) which is very bright (echogenic)..

Kidneys. IVU: Renal outline is seen in nephrogenic phase. Calyceal system is seen in pyelographic phase..

Kidneys. CT and MRI: Kidneys are seen as slices from T12-L3 vertebral levels. They are homogeneous on unenhanced CT images. On MRI , the cortex and medulla appear different on T1 and T2 weighted images… T1: cortex is higher in signal (hyperintensity mean whiter) than medulla. T2: cortex is lower (hypointensi mean less whiter) in signal than medulla.

Kidneys. On both CT and MRI three phases of contrast enhancement can be appreciated: Arterial cortico -medullary phase – cortex enhances strongly so cortico -medullary junction is well differentiated. (we take picture after 20-30 sec of injecting the contrast) Venous nephrogenic phase – homogeneous contrast throughout the kidney. (we take picture after 60-100 sec of injecting the contrast) Delayed excretory phase – contrast is seen in collecting system. (we take picture after 6-10 minute of injecting the contrast).

Ureters. KUB: Ureters are not visualized on plain films. Course: they pass anterior to tips of the transverse processes of L2-L5 vertebrae at ischial spines and medially again to the bladder. US: The proximal and distal parts may be visible when dilated. Mid-portion is not usually seen due to gaseous reflections unless abnormally dilated..

Ureters. IVU: Are usually partially visualized when filled with contrast due to peristalsis. Course: same as on KUB . CT scan: Ureters can be identified even on non-contrast images. Normal diameter: up to 3 mm but normally has three regions of constrictions..

Urinary Bladder. Plain films: Smooth and rounded soft-tissue density with surrounding lucent line. Contrast studies: Fills with contrast either after IV injection in IVU or retrogradely via the urethra. Uterine and prostatic impressions are seen at postero -superiorly and inferiorly , respectively..

Urinary Bladder. Ultrasound: Anechoic fluid filled structure. Normal wall thickness: 3-5 mm. CT scan: Fluid density on non-contrast images. Hyperdense on contrast enhanced images. MRI: T1: bladder wall and contents are homogeneous low signal. T2: wall is low signal and urine is high signal..

Male Urethra. Retrograde urethrography : Urethra is outline by contrast, verumontanum appears as a posterior filling defect in prostatic urethra..

Prostate Gland. Ultrasound: Peripheral zone – isoechoic Central part – hypoechoic CT scan: Rounded soft-tissue density. Zonal anatomy cannot be distinguished..

Prostate Gland. MRI: T1: low signal intensity, zones cannot be distinguished. T2: is excellent for zonal anatomy. Peripheral zone – high signal. Transitional & central zones – intermediate signal..

Gallery.

CT vs MRI.

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