14 - Radiology of the Renal Tract Flashcards
What kinds of imaging are used in the renal tract?
plain film intravenous urogram (IVU) - less US CT MRI Nuclear medicine
Plain film?
Often the first imaging modality
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Shows radio-opaque stones BUT there are non-radio-opaque stones
Little else you can see on plain film
Which renal calculi can you see on plain film?
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
What is renal colic?
Abd pain commonly caused by kidney stones
Where do the ureters travel?
Parallel to the transverse processes of the lumbar vertebrae (so where you often will find a ureteric calculus)
IVU?
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
Ultrasound?
- 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
What is US useful for?
Renal stones, renal obstruction, renal mass, bladder lessions (good as is filled with WATER - air is bad on US)
What is US NOT useful for?
To assess the ureters
Describe the echogenicity of the kidney in US
- capsule is an echogenic line
- medulla darker?
- the central sinus complex has high echogenicity as contains fat, vessels and fibrous tissue
CT?
- 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
What is CT useful for?
Stones/calculi, tumours, trauma, infection
How should the kidney look on ct?
- 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
What muscle are the kidney’s parallel to?
Psoas
MRI?
- EXCELLENT soft tissue evaluation and fluid
- expensive
- no rad
- longer scan time (someone with renal colic isn’t going to sit still this long)
What is MRI useful for?
Soft tissue abnormalities
Renal Tumour
Infection
Nuclear Medicine?
- gamma camera and injecting radioactive isotopes
- NM is a FUNCTIONAL test; it assesses the function and excretion of the kidneys
- still involves radiation
What is NM useful for?
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
What are you looking for in antenatal renal imaging?
- congenital abnormalities like agenesis, polycystic kidneys.. (check these at the 20 week check)
- obstructed kidneys (PUJ/pelvi-uretetic junction constriction can cause hydronephrosis)
- reflux
What do you expect to see with agenesis?
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
Antenatal reflux?
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
Why may you get bilaterally enlarged kidneys in antenatal?
Polycystic kidneys - aren’t very functional
What may cause thin renal parenchyma and a dilated renal pelvis
hydronephrosis? Kidney/ureters may be blocked or there may be reflux (vesico-ureteric reflux)
Vesico-ureteric reflux?
- may see dilated ureters and calyces
- damages the ureters
Posterior urethral valves?
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
Young 25 year old, left plank radiation to the groin, haematuria, no fever, normal WBC
- 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
Suspected kidney stones, but nothing seen on xray. What should the next imaging test be?
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
Renal colic?
- 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)
What do you often see with calculi?
- 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.
Where will you see a stone in the ureters?
Sitting on top of psoas and transverse processes
What is the upper limit of the size of stones that will pass?
6mm (mean of 22 days to pass!)
42 year old, right flank pain (NOT radiating), high WBC
- 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
US of inlammed kidney
- 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
Elderly 85 year old man with recurrent UTIs
- 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
22 year old woman, decreased renal function (i.e. high creatine and urea)
- 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
25 year old man crashed his bike in the forest
- 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!
No dye in left kidney?
Left renal kidney has avulsed/pulled off of the aorta (spasmed and so didn’t bleed much)
