Imaging techniques to examine the urinary system

2021-07-01 02:44 PM

The ultrasound image shows that the kidney consists of two distinct regions: the renal sinus in the center of the kidney, and the renal parenchyma in the periphery. The kidney is surrounded by a renal capsule with an echogenic border

Urinary system (abdomen) film unprepared (ASP: abdomen sans preparation)


Look for unusual calcifications.

View skeletal system abnormalities.

Look for a space-occupying effect in the abdomen: the tumor is posterior or intraperitoneal pushing the air into the bowel.

A must-have film, prior to performing abdominal preparatory imaging techniques


Prepare the patient for an enema 3 days before, enema the night before, and the next morning before the scan.

The film took straight, supine, from the upper border of D12 to the end of the pubic joint, holding the breath.

When there are symptoms of the urethra, take a picture of the urethral position (up to 450).

Can add: focal photography, side view, rearview.


See the lateral border of the perineal muscle D12 - L14 to the iliac crest if there is a fatty layer at the margin.

The shadow of the kidney is seen if there is a layer of fat around the kidney and the film is constant (except < 8 years old, old, thin).

See the oval shade of the bladder filled with urine.

See the edge under the liver, spleen.

See spine, pelvis, hip joints on both sides.

Ultrasound (Echographie)

As an effective imaging tool to explore the renal parenchyma and perirenal space, it is the best technique to examine the prostate gland. Doppler ultrasound helps to study the renal blood vessels.

Examine the patient in the supine, bilateral, lateral, and possibly prone position. Use a probe with a frequency of 3.5-5 MHz. The transducer transmits and receives the reflected ultrasonic waves. The ultrasound image is a two-dimensional, black-and-white tomographic image. Scan the transducer in different directions consecutively, cutting through at least two perpendicular planes: longitudinal and transverse renal, bladder. The patient holds urine for bladder examination. Doppler ultrasound to study blood flow velocity, find narrowings. Color Doppler ultrasound to better see the blood vessels in structure and direction of blood flow. 3D, 4D ultrasound, mainly beneficial to supplement fetal examination.

The ultrasound image shows that the kidney consists of two distinct regions: the renal sinus in the center of the kidney, and the renal parenchyma in the periphery. The kidney is surrounded by a renal capsule with an echogenic border. The renal sinus, which is hyperechoic (white) due to the presence of fat, along with the vascular walls and the renal pelvis, should give much negative feedback. When urine is present in the renal pelvis, an empty (black) layer of negative (no negative feedback) fluid is seen in the middle of the hyperechoic region. Renal parenchyma is hypoechoic (gray) (little negative feedback) including the renal cortex on the outside, the main renal medulla being the Malpighian pyramids in the inner cortex, between the Malpighi pyramids are the cortical Bertin columns. In children, thin people can distinguish medulla - renal cortex, renal medulla is more hypoechoic.


Simple technique, easy to implement, low cost.

Good result.

Can be re-examined many times.

Can be performed at the bedside.

No harm to health.

Ultrasound can view kidney morphology in 3 dimensions, see tumors in the parenchyma, can distinguish solid or liquid mass, can see the perirenal space.

Ultrasonography can show the proximal ureter to the renal pelvis & the ureter to the bladder wall.

Ultrasound shows the bladder wall, bladder lumen, and prostate gland through the bladder.


Depends on the level of the examiner

Depends on the quality of the ultrasound machine.

Patient dependence (fitness, cooperation)

Ultrasonography did not show pyelonephritis and ureters when not dilated. Renal function was not assessed.

Diagnosis of the dilated urinary tract is sensitive but has false negatives & false positives.

Urographie intraveineuse (UIV)


Patient Preparation: Enemas are an important factor affecting film quality.

You should fast for 3 - 6 hours before the scan to allow the urine to concentrate the contrast agent.

Some cases should not have fasted as kidney failure, Kahler's disease.

Unprepared urography immediately prior to intravenous urography.

Iodine contrast: water-soluble type with high permeability eg Urografin 370mg I/ml, Télébrix 370mg I/ml or low osmolarity eg (Ultravist 300mg I/ml, opamiron 370mg I/ml. Dosage 1ml - 2ml/1kg of body weight, not to exceed 3ml/kg.

Restricted indication for children under 2 weeks & over 70 years old. Women of reproductive age are indicated for intravenous urography in the first half of the menstrual cycle, to avoid pregnancy without knowing that it causes fetal radiation.

Two vascular contrast scans must be spaced more than 5 days apart.

It is important to note risk factors such as drug allergy with iodine: history of allergies, heart failure, high blood pressure, cirrhosis, nephrotic syndrome, kidney failure. If the patient has risk factors, prophylaxis should be given, preferably 3 days in advance (eg, a combination of celestine, polyamine, Atarax); and should choose low osmolarity contrast medium (3-20 times more expensive).

Contrast is one of the least harmful drugs. However, serious complications and even death can occur despite prevention. Reaction testing prior to contrast injection has long been considered futile, confusing, and dangerous. Always consider the indication, should not be abused, and not too reserved. The rate of serious complications requiring treatment is 131/100,000; the Mortality rate: 1/10000.

Conclusion dumb kidney on X-ray must take a film at 3 hours if no drug is excreted into the renal calyx. Conclusion True dumb kidney requires imaging after 24 hours.

Indications & Contraindications

There are almost no absolute contraindications. The most important contraindication is inappropriate intravenous urography.

Intravenous urography is widely indicated when there are clinical and biological changes related to the urinary system.

Common specific indications:

Blood in the urine of unknown cause.

Urinary system stones, diagnosis, and assessment of the condition of the renal pelvis, ureter, bladder, and function of each kidney.

Renal colic, when abdominal radiographs are not prepared & ultrasound is not sufficiently diagnostic.

Suspicion of the urinary tract.

Kidney injury

Retroperitoneal tumor


Contraindications for: severe dehydration

Relative contraindications: renal failure, diabetes, iodine allergy, Kahler's disease, pregnant women.        

Normal results

The results of the venous urography must be analyzed systematically and the two sides must be compared. Evaluation of urinary system morphology and function.           

The bean-shaped kidneys are located on either side of the lumbar spine close to the lateral iliac lumbosacral margin. The longitudinal axis of the kidney is parallel to the lateral iliac muscle. The kidney is composed of the periphery of the renal parenchyma and the central part of the renal sinus. The renal sinus consists of the renal calyx, renal artery - vein, and fatty tissue. Renal parenchyma consists of the outer renal cortex and the inner renal medulla. The main renal medulla is the Malpighian pyramids. Between these pyramids are the Bertin columns also belonging to the renal cortex. Malpighi's tower has a cone shape, the top of the cone is surrounded by the base of the renal pelvis. The urinary tract or urinary tract includes the calyx, renal pelvis, ureters, bladder, and urethra.

Tubular - calyx - renal pelvis:

The radio is shaped like a wine glass. The number of pylons corresponds to the number of Malpighian towers and varies from 7 to 15. The orientation of the pylons is very different, so the X-ray image is triangular, round, or crescent-shaped, overlapping the renal pelvis.

The renal tubules are grouped into 3-5 renal calyces, usually, there are 3 groups: upper, middle, and lower calyces; The renal calyces connect to the renal pelvis. The renal pelvis is triangular when filled with urine, the upper margin convex and the lower margin concave. The renal pelvis becomes progressively smaller and continuous with the ureter. The renal pelvis may be divided into two or more, maybe large and partially located outside the renal sinus, which is normal.


The image of the ureter is a column of contrast, discontinuous. The ureter is divided into 3 segments: the lumbar segment, from the renal pelvis to the superior edge of the sacral wing; iliac segment from the superior border to the lower border of the sacrum, the pelvic segment from the lower border of the sacral blade to the bladder. There are three anatomical narrowing places where stones are common: the ureter-pelvis junction, the anterior cross of the iliac vessels, and the place where the ureter empties into the bladder. The entire ureter is never seen on a single radiograph, due to peristalsis. Peristalsis from the upper calyx, through the renal pelvis, the ureter expels urine.


Contrast begins to reach the bladder after 5 minutes. The dome of the bladder in women when filled with medication can be dimpled due to an anterior flexion of the uterus. When distended, the bladder has a vertical axis across the S1 transverse arch, the base at the superior border of the pubic bone. The large prostate pushes the bottom of the bladder upward. When urinating, the bladder is small and radial, and there is no residual urine.


The male urethra can be seen during urination: There are 4 segments: the prostatic urethra is the rhombus, the urethra is narrow, the bulbous urethra has the largest diameter, and the cavernous urethra has a boat-terminal fossa.

The female urethra is short, in the perineum, upright or anterior. The diameter gradually decreases and ends with a pit.

Figure: Design of the longitudinal section of the kidney.

Figure: The axes of the kidney.

Figure: Normal changes in the renal pelvis.

Figure: Male bladder and urethra.

Basic abnormalities of the urinary tract:

Includes convex and convex shapes

The convex image is the opacity of the contrast medium in the parenchyma, outside the Hodson line. This line is drawn by connecting the base of the tubules, which are parallel to the renal margin. Common causes of convexity are cavernous tubercles and congenital calyx diverticulum.

The defect is a bright shadow on the background of the contrast medium in the urinary tract. The most common causes of venous urolithiasis are non-contrast stones, blood clots, and tumors of the urinary tract.

Abnormal images in the kidney

Abnormalities in quantity:

There may be 3 kidneys or 1 kidney.

Abnormalities of position and abnormalities of renal axis:

The prolapsed kidney is a low-lying kidney with an altered renal axis and a tortuous ureter. Kidney prolapse can be congenital or acquired due to compression. Ectopic kidney is a congenital abnormality caused by the cessation of renal germ migration during the fetal period; The ectopic can be on the same side or on the other side of the healthy kidney. There are many associated abnormalities: renal rotation, short ureter. Renal axis abnormalities may be isolated. The horseshoe-shaped kidney is a congenital malformation, the lower poles of the kidney parenchyma are conjoined, 2 separate renal pelvises and ureters, sigmoid kidney ...

Renal margin abnormalities:

It is possible that the changes are not of pathological significance: renal lobes are present in the fetus; the renal margins are horizontal with the level of the Bertin columns.

The left kidney is camel-shaped, triangular in shape, the apex is outside, possibly mistaken for a kidney tumor. Parenchymal thickness is unchanged, Hodson line is normal. The cause is an imprint of the spleen.

Renal margin hypertrophy or Bertin columns, pseudotumor, vascular structure, and renal tubules were normal on contrast-enhanced renal tissue film (tubular imaging, 60 seconds after contrast injection).

Renal border changes due to pathological conditions such as a renal parenchymal tumor, renal cocoon, make the renal margin citrus. The renal margin has depression due to chronic pyelonephritis; the mark is at the level of the calyx. Concave renal margin due to partial renal hypoplasia.

Size irregularities:

The length, width, and width of the kidney in Vietnamese people according to a study are 10 cm, 5 cm, 4.5 cm. The length of the kidney can be compared with 3.5 lumbar vertebrae ± half a vertebra. Large kidneys due to compensatory action when there is no opposite kidney, due to fluid retention in the stage of renal parenchymal atrophy, renal cocoon, renal tumor. Small kidneys (less than 3 lumbar segments in length) due to hypoplasia, renal parenchymal atrophy after chronic infection, chronic fluid retention.

Figure: Congenital abnormalities of the kidney.

(1. ectopic kidney; 2. ipsilateral kidney; 3. fused kidneys; 4.5. horseshoe kidney; 6. fused kidneys).

Figure: Congenital abnormalities of the ureter.

(1. junction syndrome; 2. posterior inferior vena cava; 3.4. double system; 5. 6. ureteral prolapse; 7. giant ureter).

Figure. Diagram of venous urogram

(1. incomplete and complete double system; 2. horseshoe kidney)

Computed tomography (CT)

Computed tomography has an important place among the techniques of examining the urinary system.

The body-axis sections from the kidney to the prostate, can reconstruct images in any other plane or reconstruct 3-D images, allowing to examine parenchymal, excretory routes, renal calyces, and urinary tracts. esophagus, bladder, prostate gland.

Computed tomography measures density (HU: Hounsfield unit) so it can distinguish blood, fat, calcification, necrosis, fluid...

Computed tomography with intravenous contrast helps to better differentiate structures, identify rich, poor, or avascular lesions, and study renal vasculature.

View the urinary system in its anatomical position, among other organs in the abdomen.


Evaluation of the spread of Urinary System Tumor, Prostate Tumor. Renal tumor staging is the basis for treatment methods.

Infectious diseases of renal parenchyma & perirenal cavity: acute pyelonephritis, renal abscess, yellow granulomatous pyelonephritis...

Renal trauma is the most complete and clear technique. Computed tomography simultaneously evaluates the lesions of solid and hollow viscera in the abdomen.

Acute or chronic ureteral obstruction of unknown etiology.

Retroperitoneal and pelvic pathology affect the urinary system.

Magnetic resonance imaging (MRI magnetic resonance imaging)

Magnetic Resonance Imaging is a contiguous tomographic image, in all planes. It is the most modern technology in the diagnostic imaging industry. Plays a prominent role in neurologic examination and software. For the urinary system, which has not been fully exploited, there are now some clear benefits.

General advantages of magnetic resonance:

View structure in 3D space, view in any plane.

View blood vessels without contrast

It is a technique that has the advantage of distinguishing structures, with high structural resolution.

It is a technique that does not cause radiation, does not cause complications due to contrast injection for patients, suitable for patients who are pregnant women.

Magnetic contrast can be injected with the same effect as iodinated contrast in computed tomography


The low spatial resolution does not clearly see the edges of the structure

There is a lot of noise due to bowel movements, respiratory movements, heart rate, because the recording time is many minutes long.

Contraindicated for patients with metal objects in the body, because it causes many magnetic fields.

Expensive equipment, 4 times the cost of Computerized tomography.

Indications Magnetic resonance for the urinary system is still limited, mainly for bladder and prostate tumors, evaluating renal artery stenosis.

Techniques of direct dyeing

Retrograde imaging: Performed in a sterile room in conjunction with a urologist. Cystoscopy inserts the catheter into the end of the ureter or into the renal pelvis and then injects contrast.

Main Indication: Obstructive urinary tract syndrome when venous ureters do not show obstruction or view defects in the urinary tract unclear on other techniques.

Disadvantages: Upstream infection, patient pain, difficulty to insert the catheter.

Downstream imaging: Fewer complications, less complicated than upstream technique. The catheter is inserted into the renal calyx to inject contrast. There is therapeutic significance because of urine drainage and possible stone collection through ossification. Limitations of the technique: difficult to perform when the renal pelvis is not dilated, the lower ureter is not clearly visible.

Retrograde cystography: Place a catheter in the male urethral fossa and inject contrast to see if the urethra is narrow due to trauma, infection; urethral probe, or look for vesicoureteral reflux. Film taken during injection, then urinating, then after urinating (find residual urine).

Angiography of the kidney

The role of renal angiography has decreased significantly since several decades, when ultrasound and ultra-Doppler, computed tomography, and magnetic resonance were born. Currently, the main indication is for intervention such as embolization, renal angioplasty.

Insert the catheter into the femoral artery and then the abdominal aorta, bilateral renal angiography or selective renal artery catheterization.

Classical angiography is now being replaced by digital subtraction angiography (DSA). Intravenous contrast injection only requires 50% of the amount of contrast compared to classic angiography to see the artery.

Computed tomography angiography (CTA) and magnetic resonance angiography (MRA), are competing with digital background erasure angiography for the diagnosis of vascular diseases such as aneurysms, aneurysms, Arteriovenous fistula, hemangioma, renal artery stenosis, hematuria of unknown cause...