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
