Imaging of the Urinary System Flashcards
What are the indications for renal imaging?
Renal colic and renal stone disease - for diagnosis and follow up Haematuria Suspected renal mass Recurrent UTI Hypertension
What are the imaging techniques used for imaging of the urinary system?
Plain film Contrast studies - IVU, pyelography, cystography Ultrasound +/- constrast CT and CTU MR and MRU Isotope scans PET-CT
What are the advantages of plain film imaging?
Cheap and readily available
Functional and anatomical information
What are the disadvantages of plain film imaging?
Low sensitivity and specificity for urological disease
Radiation exposure
Where is contrast injected in pyelography?
Into the ureters
What does micturating cystourethrography demonstrate?
Vesico-ureteric reflux and its grade
What are the advantages of ultrasound
Cheap and readily available
No radiation
Contrast is not nephrotoxic
Real time imaging
What are the disadvantages of ultrasound?
Limited by body habitus and gas
Poor visualisation of ureters
Operator dependent
No functional information
What are the advantages of CT?
Good spatial resolution with capability of multi-planar reformat
Currently imaging modality of choice for detection of renal stones, staging renal tumours and investigation of haematuria
What are the disadvantages of CT?
Radiation dose
Cost
Contrast resolution less than MR
Contrast reaction and nephrotoxicity
What are the advantages of MR scanning?
Multiplanar imaging
Excellent contrast resolution
Imaging of urothelium without contrast injection (MRU)
What are the disadvantages of MR scanning?
Poor spatial resolution
Poor detection of calcification and stones
Cost
Contraindications - pace maker, claustrophobia
Contrast reaction and other side effects
When are isotope scans useful in imaging the urinary system?
DMSA to look for renal scarring
MAG3 to assess renal function and drainage
Bone scan to look for metastatic disease e.g. from prostate cancer
Why is there limited use of PET-CT in the staging of urological malignancies?
Due to high uptake in urine and variable uptake by tumours
May be useful for extra-urological metastatic disease if other imaging modalities are equivocal or in poor surgical candidates
