GU imaging

Question 1

Let’s define what structures we are imaging…

Answer 1

• Kidneys
• Ureters
• Bladder

Question 2

What issues typically require imaging of the urinary tract?

Answer 2

• Kidney stones (nephrolithiasis)
• Acute kidney injury (AKI)
• Chronic kidney disease
• Urinary tract obstruction (want to find it when it causes AKI so it doesn’t lead to CKD!)
• Kidney or bladder cancer
• Kidney cysts (either solitary or as part of a genetic polycystic kidney disease), abscesses, or infarcts

Question 3

Abdominal Plain Film

Answer 3

• if obtained, most common view is abdominal AP supine- view also called by the acronym KUB
• because it includes the Kidneys, Ureters, and Bladder
• Sometimes kidney outline can be seen if surrounded by retroperitoneal fat*

Question 4

Normal Abd X-ray

Answer 4

• (A) Normal plain film of the abdomen.
• The lower margins of the posterior portion of the liver, the hepatic angle (H), and the lower part of the spleen (S) are delineated by a fat shadow.
• Both kidneys (K) and the psoas muscle shadows (arrowheads) are outlined by a fat shadow.
• The properitoneal fat stripe is also shown bilaterally (arrows).

Question 5

Abd X-ray cons

Answer 5

• Even though ≈80-90% of pts with nephrolithiasis form calcium stones (calcium oxalate +/- calcium phosphate), the sensitivity of KUB for picking up kidney stones is only ~50-60%
• Struvite* stones and cystine** stones also radiopaque
• Easy to miss small stones or stones overlying bony structures
• Uric acid stones radiolucent

Question 6

KUB showing staghorn calculi

Answer 6

Question 7

diagnostic test of choice when nephrolithiasis is suspected is ..?

Answer 7

• noncontrast* helical CT scan (“stone protocol”)

Question 8

CT scan of kideny stone

Answer 8

• Renal calculus, conventional radiograph (A), and axial computed tomography (CT) scan (B).
• A, There is a calcification (black arrow) that overlies the shadow of the left kidney (white arrow) . Although it is too small to recognize lamination, its location suggests a renal calculus. B, In a different patient, an image from an unenhanced axial CT called a stone search reveals a large calcification in the proximal right ureter (black arrow) and several smaller calcifications in the left intrarenal collecting system (white arrow) . Because of its greater sensitivity, a CT stone search done without intravenous contrast has primarily replaced conventional radiography for the identification of renal and ureteral calculi

Question 9

Intravenous Pyelogram (IVP)

Answer 9

• Aka intravenous urogram
• “Old time” technique, currently much less popular - replaced with ultrasound and CT
• Requires the administration of IV contrast and use of plain film
• Has a decent sensitivity and specificity for the detection of stones and can pick up obstruction

Question 10

KUB radiograph method…

Answer 10

• KUB radiographs are obtained immediately before IV contrast administration and at 1, 5, 10, and 15 minutes afterwards or until visible contrast material fills both ureters . Prone films are sometimes obtained to enhance visualization of the ureters. When the bladder is full of contrast and the distal ureters contain sufficient contrast for visualization, the patient is asked to void; then a postvoid film is taken.

Question 11

Renal Ultrasound

Answer 11

• Most commonly used imaging modality for renal disease
• Four Primary Uses:
  
  • Identify urinary tract obstruction to drainage – (“post-renal” cause of AKI) “hydronephrosis”
  • Determine kidney size / echogenicity in trying to determine the etiology and chronicity of kidney disease
  • Evaluate for simple or complex cysts / solid masses/multiple cysts (Polycystic Kidney Disease)
  • Guide kidney biopsies or drain fluid collections around kidneys

Question 12

Renal Ultrasound : hydronephrosis

Answer 12

• Identify obstruction to urine drainage by looking for “hydronephrosis”
  
  • Literally “water inside the kidney” — refers to distension and dilation of the renal pelvis and calyces, caused by obstruction of the free flow of urine from the kidney
  • Urinary tract obstruction may lead to urinary tract infection and urosepsis, if bilateral may be a cause of AKI (“postrenal AKI”) and prolonged obstruction eventually may cause significant renal parenchymal compression, damage, scarring and atrophy with decline in GFR (i.e. prolonged obstruction is a cause of CKD)

Question 13

Common Causes of UTO / Hydronephrosis

Answer 13

• Benign prostatic hyperplasia, or “BPH” – most common (extrinsic compression of prostatic urethra)
• Cancer of the prostate or extensive cancer of other organs in the pelvis– i.e. lymphoma, ovarian cancer, cervical cancer (extrinsic compression of the ureters)
• Kidney stones
• Urothelial carcinoma* (e.g. bladder CA or CA of the ureter)
• Blood clots
• Neurogenic bladder

Question 14

hydronephrosis possible cause image

Answer 14