Urinary System - Radiological Anatomy

Urinary System - Radiological Anatomy

• The urinary system includes two kidneys, two ureters, one urinary bladder, and one urethra.
• Radiographic examinations of the urinary system are commonly performed using contrast media.
• Kidneys are located in the lumbar region.
• The kidney has an outer fibrous capsule, perirenal fat, renal fascia, and pararenal fat.
• The renal sinus is a cavity within the kidney, containing the renal pelvis, renal vein, branches of renal arteries, ureter and lymph vessels.
• The kidney is divided into two main parts: the renal parenchyma (for urine production) and the renal pelvicalyceal system (collects urine).
• The renal medulla is composed of renal pyramids with their apices (renal papillae) pointing towards the center.
• The renal cortex extends into the medulla between the pyramids as renal columns.
• The renal sinus contains the renal pelvis and its branches, the major and minor calyces.
• The renal pelvis is connected to the ureter.
• The kidney has a characteristic blood supply, with different artery and vein levels.
• The main arteries of the kidney are renal arteries.
• The renal blood supply consists of segments of arteries leading to interlobar, arcuate, interlobular, afferent and efferent arterioles
• Each kidney is supplied by multiple branches from a single renal artery
• The collecting system of the kidney consists of renal pelvis, major calyces, and minor calyces
• Ultrasound, X-ray KUB (Kidney, Ureter, Bladder), fluoroscopy and CT scan are imaging techniques used for urinary system examination.
• Variations in kidney structures, such as lobulation and columns of Bertin, can be normal.
• Kidney anomalies can include agenesis (absence), duplex kidney, ectopic kidney (in unusual location), crossed fused ectopic kidneys and horseshoe kidney.

Kidney Location

• Right kidney-posterior to the liver.
• Left kidney-posterior to the spleen.
• The upper pole of the kidney is near the diaphragm.

Kidney Poles

• Kidneys are divided into upper, middle, and lower poles for describing pathology location.

Sonographic Characteristics of Normal Kidney

• Average size: 11cm (range 9-13cm).
• Right kidney is smaller than or equal to the liver, left is smaller than the spleen.
• Kidney parenchyma is homogeneous (except hypoechoic pyramids).
• Renal sinus is hyperechoic.
• External contour is smooth.

Renal Blood Supply

• The blood supply to the kidney is a complex system involving various arteries and veins.
• Multiple arteries branching and connecting to form the blood supply for the filtering units (Glomeruli).
• Different levels of vessels can be seen, including segmental, interlobar, arcuate, and interlobular.

X-Ray KUB

• X-ray KUB (Kidney, Ureter, Bladder) examination is used to identify stones in the urinary system.
• An X-ray KUB image enables visualization of the kidney, ureter, and bladder.

Ultrasound

• Ultrasound can identify the kidneys and their location (posterior to the liver on the right, posterior to the spleen on the left).
• Ultrasound can be used to locate kidney, spleen, and other abdominal organs.
• It's possible to locate anatomical structures and diagnose pathological conditions using ultrasound.

Fluoroscopy

• Fluoroscopy is a technique used for dynamic imaging of the urinary system.
• Types of fluoroscopic urographic examinations include: intravenous urography (IVU), cystography (cystogram), ascending urethrography, and antegrade pyelography.

Intravenous Urography (IVU)

• IVU is a common procedure to image the urinary tract using contrast.
• IVU images can show the collecting system of the kidney.
• IVU helps in assessing the functionality of the kidneys.

I.V.U - Time to Follow

• Immediate film: Major calyces appear typically within 2 minutes of contrast administration.
• 10-20 min: Pelvicalyceal system and upper ureter (ureterogram phase).
• 45 min: Lower ureter and bladder filling (cystogram phase).
• 1½ hr: Full bladder.

Anatomy Review on IVU

• The IVU studies show the different parts of the renal collecting system, including: minor calyces, major calyces, renal pelvis, ureteropelvic junction, proximal ureter, distal ureter and urinary bladder

Antegrade Pyelography

• An antegrade pyelography involves injecting contrast directly into the kidney or ureter using a catheter to visualize these structures.
• A method to visualize the kidney and ureter, in case the intravenous method is not possible.

Cystography (Cystogram)

• Cystogram is a form of fluoroscopy used to image the urinary bladder.
• Cystography images are done using an iodinated contrast medium installed through a catheter.
• Cystography is used to identify conditions such as trauma, calculi and tumors in the urinary bladder

Urethrography (Terminology)

• Urethrography is a study of the male urethra, commonly using a retrograde or ascending approach.
• Retrograde urethrography (RUG): Introduces contrast into distal urethra.
• Ascending urethrography (ASU): Introduces contrast into proximal urethra during micturition.
• Voiding cystourethrography (VCUG): Studies contrast during urination.

Ascending Urethrography

• Ascending urethrography is a technique to visualize the length of the urethra in male patients.
• It's used to look at the different parts of the male urethra to see whether there are any problems with it, such as blockages or abnormalities.

Micturating Cystourethrography (MCUG)

• MCUG is a functional study that assesses urination process in bladder and urethra.
• It's used in situations like vesicoureteral reflux or bladder abnormalities.

Vesicoureteral Reflux (VUR)

• VUR presents as urine flowing from the bladder into the ureters or kidneys.
• VUR typically appears as different grades of severity.

Common Radiological Findings

• Hydronephrosis-kidney swelling, caused by urine backflow.
• Hydroureter-ureter swelling-often due to ureter blockages.

Non-functioning Kidney

• A non-functioning kidney might not show up in the image after 45 minutes, when contrast has had the chance to pass through it.