Imaging of renal tract Flashcards
As a GP (in the community). When do you consider renal imaging?
- abdominal mass
- drop in renal function
- infection -> but not everyone (if recurrent UTI and in men)
- haematuria
In hospital (acute setting), when would you consider renal imaging?
- abdominal mass
- decreased renal function
- infection
- renal trauma - haematuria (?)
When to consider renal imaging in a hospital (outpatient) setting?
- follow up of malignancy
- congenital abnormalities
What pathologies of kidney is a renal imaging good to look at? What are not?
- Good: masses, stones
- Not suitable: glomerulus, tubular conditions *
* these are diagnosed by renal biopsy
Advantages of X-ray
cheap, quick and lower dose compared to CT
*but limited information provided (as compared with CT)
What can we use x-ray for (in terms of the renal system)?
- useful for radiopaque stones
*not used for gallstones as they contain fat/cholesterol
What landmarks on X-ray would allow us to identify kidney?
- psoas muscle
- L2 vertebra
What is this?
Opacity in renal region -> renal calculi
What’s that?
Could be renal but also ureteric calculi
What’s the abnormality?
Some sort of calculi (we cannot really determine if it is within the ureters or in the bladder)
What’s that?
Staghorn calculi
*opacity in the vertebra -> belly bottom piercing
How do we achieve intravenous urograms?
What are they used for?
- contrast is injected IV -> it goes through the kidney
- delayed radiograph would show opacification of the collecting system
What conditions do we assess for by the use of intravenous urogram?
- hydronephrosis (dilatation of renal pelvis/urethra)
- ureteric reflux (incompetent valve in the bladder -> urine backup) *
*now CT used more for that
What’s that?
Hydronephrosis (on the R) - dilated ureter
How does ultrasound work? How is the image formed?
USS
- high-frequency sound waves transmitted through the tissues
- forms an image by measuring the time taken by the echoes to return
Advantages of USS
- do not use radiation
- portable
look at the image of the kidney on USS
What’s that?
Hydronephrosis - renal pelvis is seen and grossly dilated
What’s that?
Image of the bladder - used also to assess the volume
*scan before the pt goes to wee -> then scan after -> to assess the amount of residual volume
What’s that?
Calculi in the bladder -> stone
What the difference between these two images?
on the first one: we cannot see past the mass’ -> possibly stone
on the right one: we can see it has a similar structure to the tissue around it -> bladder polyp
Pros and cons of ultrasound
- Pros: cheap, quick, portable, no ionising radiation, good detail in children, can assess vascularity (doppler function), real-time imaging
- Cons: difficult in obese (as the waves go through lots of fat), operator dependent, technical limitations
What’s the principle of CT scan?
multiple x - rays from different angles
Just look at the picture of that CT scan
What’s the abnormality?
L kidney - looks dilated -> cyst-like structures
*polycystic kidney with hydronephrosis
What’s that?
R renal stone causing slight hydronephrosis
What’s that?
Crossed-fused renal ectopia
*kidney came from another side and fused with the other - kidney function is normal
*however, need to monitor as may lead to CKD
What is the abnormality?
Renal cell carcinoma
Pros of CT scan
- great detail of information on an image
- quick
- cheper than MRI
- easy access
Cons of CT scan
Cons:
- high radiation dose
- contrast induced nephropathy (avoid if eGFR <30)
- epensive
- not portable
What if there is a clinical need for CT scan in pt with eGFR <30?
We consider alternative methods or hydrate the patient -> bag of fluid before and after the scan *
* but careful in HF
The principle of MRI scan
- cross-sectional image (similar to CT)
- use magnetic properties of hydrogen atoms within human tissues
*magnet on -> hydrogen atoms flip/ go to one side
* magnet off -> hydrogen atoms relax (by differing amounts)
- lots of hydrogen -> relax fast
- little hydrogen -> relax slowly
Image formed by working out by how quickly hydrogen atoms relax
Can MRI be used in pregnant women?
Yes, it does not use ionising radiation
*MRI imaging of foetal heart can be even measured
Look at the normal MRI scan (anatomy)
*look from feet up (like in CT scan)
Pros of MRI scan
- functional imaging
- ecellent diagnostic detail
- not ionising
Cons of MRI scan
- expensive
- time consuming
- claustrophobia
- limited indications
Nuclear medicine
- principle
- gamma camera and radioactive isotopes are utilized
- Radioisotopes emit radiation as they travel through the body -> so it can be ‘traced’
* can be tagged with an organ
Pros of nuclear medicine imaging
Pros
- functional imaging
- split function -> useful in kids and transplant patients (to see which kidney is problematic)
- good sensitivity and specificity
What is an abnormality on this nuclear medicine scan?
R side is not draining the contrast -> some sort of obstruction
16 years old girl with R iliac fossa pain
- differentials
Differentials:
- renal/uretetic stone
- appendicitis
- ovarian torsion
- ectopic pregnancy
16 years old girl with R iliac fossa pain
- what mode of imaging would you use?
Ultrasound
- ultrasound -> stone, pregnancy and ectopic pregnancy
* possibly (if not much bowel gas) - to indicate appendicitis
AKI in an 87 y old nursing home resident (GP detected AKI from the bloods)
Causes
- pre-renal: dehydration, sepsis, bleeding elsewhere (not enough perfusion)
- renal: ACE inhibitors, glomerulonephritis
- post-renal: kidney stone obstructing
AKI in an 87 y old nursing home resident
What causes would imaging show?
- Imaging would only show post-renal causes (e.g. obstruction)
Painless haematuria in elderly patient
causes
what imaging would you use?
- cancer: renal, bladder
- stone disease
- renal disease (e.g. nephritic syndrome)
Imaging: CT or MRI (malignancy, stone disease)
but definitive would be with biopsy
Middle-aged woman presenting with right flank pain, fever and high WBC
- differentials
- imaging and why
- UTI -> pyelonephritis
- infection
- appendicitis
- abscess - intraabdominal
- urolithiasis
Imaging:
- Pyelonephritis - no need to image unless not resolving
- kidney stones -> CT -> is there an urinary stasis, obstruction
- appendicitis -> USS, CT
