Imaging Flashcards
Why is it important to be sure of renal colic before requesting imaging?
- high radiation dose so ensure you’re sure before requesting
- if pt. pregnant use USS and/or MRI
What is imaging for in renal colic?
identify the calculus causing symptoms
assess the size and morphology of the calculus
detect associated ureteric obstruction
identify additional asymptomatic calculi
What are most calculi rich in?
calcium and are dens
-some are calcium poor and are of low density (urate)
What tests are used to detect calculus?
- KUB x-ray
- CT
- MRI
What is 1st line test renal colic?
KUB xray
-only minority are visible though
can also use x-rays following iv contrast: intravenous urogram IVU
Where do ureteric calculi usually get stuck?
Ureteric calculi often get stuck at predictable sites, such as the pelviureteric junction (PUJ), pelvic brim and vesicoureteric junction (VUJ).
What is the definitive test to confirm symptomatic ureteric calculus?
Non-contrast enhanced CT (‘CT stone search’) is the definitive test to confirm a symptomatic ureteric calculus
CT shows virtually all calculi, irrespective of size or calcium content
CT also shows signs of obstruction, raising diagnostic confidence:
- perinephric stranding
- hydroureteronephrosis
CT may show alternative diagnoses eg appendicitis, hernia
What are the for CT stone search
CT occasionally struggles to distinguish between small pelvic calculi and phleboliths, when there are no secondary signs to help eg hydroureter
CT gives a high radiation dose, so should be avoided in pregnancy and if possible, non-pregnant young females, when US and/or MRI may be used to give similar information
What are the imaging modalities for macroscopic haematuria in those over 50yo?
CT urography (CTU) -examines the kidneys, collecting systems and ureters
Cystoscopy:
- examines the bladder and urethra
- gives option for ureteroscopy to confirm tumour where CTU equivocal
- to ablate tumours in patients unfit for nephroureterectomy
Describe the technique for CT urography
First CT scan before contrast
-most sensitive way to detect renal or ureteric calculi
Administration of IV contrast which is concentrated and excreted by kidneys over 15 minutes, similar to traditional IVU
Top up dose of IV contrast to enhance renal parenchyma
Second CT scan following contrast = most sensitive way to detect:
- renal parenchymal tumours
- urothelial tumours of the collecting systems or ureters
- any tumour detected can be staged at the same time
Describe the investigation of macroscopic haematuria of the under 50s?
Under 50 years age, the incidence of urothelial tumours of kidney or ureter is very low, so routine CTU which imparts a double radiation dose is unjustified
Investigation strategy therefore changes as follows:
- US of kidneys to detect calculi and renal parenchymal tumours
- Cystoscopy to look for occasional bladder TCC, bladder calculi, other bladder tumours or evidence of urethritis/prostatitis
- CTU only when US and cystoscopy are normal and macroscopic haematuria persists
What is MR urography used for?
Only when CTU contraindicated as less sensitive than CTU for small calculi or upper tract TCC
Doesn’t require contrast Doesn’t use radiation So useful in patients who have -contrast allergy -renal impairment -pregnancy
Renal masses:
how do most of these present?
Some renal masses present with haematuria
Most renal masses are detected incidentally:
-by imaging performed for another reason (common)
-during clinical examination (rare)
What is the role of imaging for renal masses?
confirm a mass is present
characterise the mass as benign, indeterminate or malignant
stage malignant masses
What is imaging used for indeterminate masses?
follow up to assess mass behaviour
guidance of biopsy or ablation
What is used to look at the characterisation of renal masses?
CT is typically used to assess mass:
- size
- density (fat, fluid, soft tissue, calcified)
- uniformity (is density all the same or variable)
- internal morphology (presence of nodules, septa)
It is recognised that renal masses smaller than 3cm very rarely metastasize, whatever their appearance, so these are often followed up rather than operated upon
What are masses containing fat called?
benign angiomyolipomas
What are fluid dense masses?
cysts and uniform cysts = benign
complex cysts containing solid areas/thick septa = often malignant
What are solid (non-cystic) masses usually?
larger than 3cm are often malignant
What is usually sufficient to diagnose a simple cyst?
USS
When is MR used?
As in other situations, MR with contrast may be used instead of CT to assess renal masses in young or pregnant patients
MR can also assess features such as mass size, presence of fat or fluid and internal architecture
What imaging is used for malignant renal tumour staging?
CT is used to assess
Local extent:
- extracapsular spread
- involvement of adjacent organs
- involvement of renal vein or IVC
nodal disease
metastatic disease:
-lung, bone
What is the role of imaging in renal impairment for pre-renal disease?
pre-renal disease – MR angiography to detect RAS
What is the role of imaging in renal impairment for renal disease?
renal disease – US used to guide biopsy
What is the role of imaging in renal impairment fo post-renal disease?
US shows hydronephrosis, which often accompanies obstruction
obstruction may be at bladder outlet level and US can assess completeness of bladder emptying
other causes of ureteric obstruction often require CT for diagnosis
beware that hydronephrosis can result from ureteric reflux and is not always due to obstruction
renal size assessment by US is helpful to distinguish acute from chronic renal impairment and predict prospect of recovery
The painful scrotum - what imaging modality is used?
USS
Epididymo-orchitis - hypervascular testis and/or epidydimis
Testicular torsion - avascular testis
Trauma
What is used to image painless scrotal swelling?
USS provides excellent spatial resolution of superficial soft tissue structures and is used in diagnosis
What does a varicocoele look like on USS?
dilated scrotal venous plexus
typically on left side
tortuous veins usually >2mm in diameter
What does a hydrocoele look like on USS?
black anechoic fluid surrounding testicles
What does an epidymal cyst look like on USS?
anechoic uni or multilocular cyst
typically arise within epididymal head
extremely common
What does a testicular seminoma look like on USS?
intra-testicular soft tissue mass
often have demonstrable vascularity
US appearance varies with tumour type
What is renal injury best imaged with?
Renal injury is best assessed by CT and may involve the vascular pedicle, renal parenchyma or collecting system
What is bladder injury best imaged with?
Diagnosis is by cystography or CT cystography. After filling the bladder, contrast leaks through the bladder tear into the intra or extraperitoneal space
what is urethral injury best imaged by?
in acute setting, the role of imaging is limited
urethral trauma may be complicated by long term stricture formation - urethrography is used to define this
(if you have clinical suspicion (meatal bleeding, patient can’t pass urine) don’t attempt catheterisation - call the urologists)
What is non-vascular intervential uro-radiology used for?
relief of ureteric obstruction (nephrostomy, ureteric stent)
drainage of abscess or renal cyst
biopsy of renal masses
guided ablation of renal tumours (RFA, cryoablation)
What is vascular uro-radiology used for?
correction of renal artery stenosis
control of arterial bleeding sites (embolisation) e.g. post biopsy haemorrhage
varicocoele embolisation
