14 - Radiology of the Renal Tract

Question 1

What kinds of imaging are used in the renal tract?

Answer 1

plain film
intravenous urogram (IVU) - less
US
CT
MRI 
Nuclear medicine

Question 2

Plain film?

Answer 2

Often the first imaging modality
cheap
Shows radio-opaque stones BUT there are non-radio-opaque stones
Little else you can see on plain film

Question 3

Which renal calculi can you see on plain film?

Answer 3

Radio-opaque ones i.e. ones with CALCIUM salts. Means you can’t see renal calculi formed by accumulation/crystallisation of URIC ACID i.e. as occurs in GOUT

Question 4

What is renal colic?

Answer 4

Abd pain commonly caused by kidney stones

Question 5

Where do the ureters travel?

Answer 5

Parallel to the transverse processes of the lumbar vertebrae (so where you often will find a ureteric calculus)

Question 6

IVU?

Answer 6

Intravenous urogram
Plain xray but with contrast injected. Now usually replaced with CT or MRI.
The minor calyces should look nice and sharp (where the medulla drains into)
If they are large and swollen/not well defined and can’t really see ureters then it suggests that the urine is blocked and can’t get out

Question 7

Ultrasound?

Answer 7

• high frequency sound waves
• no radiation
• operator dependent
• patient body dependent (is a fixed frequency so a larger patient absorbs the US before it gets to the kidney

Question 8

What is US useful for?

Answer 8

Renal stones, renal obstruction, renal mass, bladder lessions (good as is filled with WATER - air is bad on US)

Question 9

What is US NOT useful for?

Answer 9

To assess the ureters

Question 10

Describe the echogenicity of the kidney in US

Answer 10

• capsule is an echogenic line
• medulla darker?
• the central sinus complex has high echogenicity as contains fat, vessels and fibrous tissue

Question 11

CT?

Answer 11

• more accurate, assesses soft tissues, fluid and calcification
• expensive
• significant radiation
• may need IV contrast (can have a reaction)
  > need to think about age risk and benefits

Question 12

What is CT useful for?

Answer 12

Stones/calculi, tumours, trauma, infection

Question 13

How should the kidney look on ct?

Answer 13

• bright
• right kidney is DARKER suggesting it isn’t getting as much blood/perfusion (bf in or out problem)
• also see the dye in the aorta
• can see the renal vein draining into the ivc

Question 14

What muscle are the kidney’s parallel to?

Answer 14

Psoas

Question 15

MRI?

Answer 15

• EXCELLENT soft tissue evaluation and fluid
• expensive
• no rad
• longer scan time (someone with renal colic isn’t going to sit still this long)

Question 16

What is MRI useful for?

Answer 16

Soft tissue abnormalities
Renal Tumour
Infection

Question 17

Nuclear Medicine?

Answer 17

• gamma camera and injecting radioactive isotopes
• NM is a FUNCTIONAL test; it assesses the function and excretion of the kidneys
• still involves radiation

Question 18

What is NM useful for?

Answer 18

Function, excretion and obstruction

• able to see the urine being excreted by the kidneys overtime
• DONT get the same detail i.e. you can’t see the calyces or ureters well, but you can tell if they are obstructed and where abouts
• can see if one kidney is darker than the other and blocked

Question 19

What are you looking for in antenatal renal imaging?

Answer 19

• congenital abnormalities like agenesis, polycystic kidneys.. (check these at the 20 week check)
• obstructed kidneys (PUJ/pelvi-uretetic junction constriction can cause hydronephrosis)
• reflux

Question 20

What do you expect to see with agenesis?

Answer 20

i.e. no kidneys. While in utero the baby swallows the amniotic fluid and so they are peeing sterile. Drink and pee it. If no kidneys then there will be very little/no fluid around the baby and so mother will have a small abd

Question 21

Antenatal reflux?

Answer 21

The ureters normally travel vertically down the transverse processes and then enter at a 45 degree angle into the bladder so everytime the bladder contracts (detrusor muscle) it clamps ureter outflow. If they entered vertically then the urine would squirt back up/reflux

Question 22

Why may you get bilaterally enlarged kidneys in antenatal?

Answer 22

Polycystic kidneys - aren’t very functional

Question 23

What may cause thin renal parenchyma and a dilated renal pelvis

Answer 23

hydronephrosis? Kidney/ureters may be blocked or there may be reflux (vesico-ureteric reflux)

Question 24

Vesico-ureteric reflux?

Answer 24

• may see dilated ureters and calyces

- damages the ureters

Question 25

Posterior urethral valves?

Answer 25

A posterior urethral valve is an obstructing membrane in the posterior male urethra due to abnormal in utero development. Causes bladder outlet obstruction and so see little urine output, bloating/palpable bladder, dribbly/doesn't squirt like they should

Question 26

Young 25 year old, left plank radiation to the groin, haematuria, no fever, normal WBC

Answer 26

- kidney stones - loin to groin pain (can appear to be testes in males/testicular pain - referred pain) - nothing seen on xray? > uric acid renal calculi

Question 27

Suspected kidney stones, but nothing seen on xray. What should the next imaging test be?

Answer 27

CT is very good at showing stones in the ureters. US is not good at imaging the ureters as the bowel gets in the way. Do a low dose CT urogram (no dye). Is an adult. > low dose will give a noisy picture but will be enough to diagnose

Question 28

Renal colic?

Answer 28

- very common 12% of pop will have a urinary stone - severe abd pain that radiates to the groin/gonad - difficulty lying still (need lots of pain relief, MRI not practical)

Question 29

What do you often see with calculi?

Answer 29

- peri-nephric stranding - peri-ureteric stranding - hydronephrosis (and so dilated swollen kidney and ureter) > may NOT cause obstruction. If just sitting in kidney don't cause a lot of problems. It's the small ones in the ureters that cause a lot of pain.

Question 30

Where will you see a stone in the ureters?

Answer 30

Sitting on top of psoas and transverse processes

Question 31

What is the upper limit of the size of stones that will pass?

Answer 31

6mm (mean of 22 days to pass!)

Question 32

42 year old, right flank pain (NOT radiating), high WBC

Answer 32

- Likely diagnosis is inflam or infection If infection is likely pyelonephritis (inflam due to bacterial infection) - would NOT x ray (not good for soft tissue) - US could help if the kidney is swollen, obstructed or if there is an abscess

Question 33

US of inlammed kidney

Answer 33

- has echos in it, isn't black like water - do doppler and if there is no BF then suggests it is not a tumor (vascular) and is more likely to be thick pus and so is an abscess

Question 34

Elderly 85 year old man with recurrent UTIs

Answer 34

- UTIs are much less common in men so recurrent utis suggests an anatomical problem - obstruction likely due to enlarged prostate - US; scan the water in the bladder and see how well he empties - there were very dilated minor calyces and renal pelvi - prostate was impinging on the prostatic urethra and is also bulging into the bladder

Question 35

22 year old woman, decreased renal function (i.e. high creatine and urea)

Answer 35

- do an US as young - as she is so young you would ask about family history i.e. was someone on dialysis - do US and see lots of cystic areas > Adult polyscystic kidney > replacement of the renal tissue with cysts, also seen in the pancreas and liver

Question 36

25 year old man crashed his bike in the forest

Answer 36

- need to know what is happening with BF to the kidney - is he actively bleeding? - has he passed water? is there HAEMATURIA?? - image; are the transverse processes fractured? - inject dye in the arterial phase and portal venous and where urine goes - don't want to breach retroperitineum to keep distinct from abd (will tamponad) - could be bleeding to death but don't see in abd!

Question 37

No dye in left kidney?

Answer 37

Left renal kidney has avulsed/pulled off of the aorta (spasmed and so didn't bleed much)