Urology - Imaging Flashcards
Why are plain abdominal films a useful first line investigation?
Plain abdominal films are essential prior to urinary tract investigation. They are particularly useful for showing calculi within the urinary tract - renal calculi, parenchymal calcification, ureteric and bladder calculi, prostatic calcification, or sclerotic bone deposits.
How can renal calcifications be misinterpreted on a plain abdominal film?
Overlying calcified mesenteric glands and pelvic vein phleboliths can often be mistaken for ureteric calculi. Inspiration and expiration films change the position of the kidneys and often confirm that a calcified area in the upper abdomen is a calculus.
Why is renal ultrasound a good imaging technique? What variant of RUS is used to assess the prostate?
RUS is one of the most valuable investigations of the urinary tract and the investigation of choice in children. It is non invasive and can be easily repeated.
Useful in - renal size, growth, masses, renal obstruction, bladder residual volumes and prostatic size. Transrectal US is used when an accurate image of the prostate is required (e.g. during biopsy).
What is an IVU? Who should get one?
IVU = intravenous urography.
Patients with urinary retention and urinary tract infection should initially have an ultrasound rather than IVU. The indications for IVU are haematuria or ureteric colic.
Not used as much, CT is preferable.
What is the procedure in an IVU?
1) Preliminary “scout” film of the abdomen
2) 50-100ml of low osmolar iodinated contrast medium is injected, contrast rapidly reaches the kidney and is excreted by glomerular filtration
3) Immediate film after injection demonstrates the nephrogram phase, showing the renal parenchyma and outline
4) Subsequent films after 5, 10 and 15 mins reveal contrast in the pelvicalyceal systems, ureters and bladder
What is retrograde pyelography? When is it performed?
A retrograde pyelogram is occasionally needed when detail of the pelvicalyceal system and ureters is not adequately identified by IV contrast. This may be when there is suspicion of a tumour in the urinary tract. In theatre, a catheter is placed into the ureter after a cystoscopy; contrast injected through the catheter outlines the pelvicalyceal system and ureter.
What is a percutaneous nephrostomy?
A nephrostomy is a catheter that is inserted into the pelvicalyceal system to provide temporary drainage of an obstructed kidney. It is also used to localise the site of an obstructing lesion such as a calculus or stricture.
What is a micturating cystogram?
This is where a catheter is inserted into the bladder and filled to capacity with contrast. After catheter removal, films are taken of the renal tract as the patient is micturating. Particular attention is given to vesico-ureteric reflux.
What techniques can be used to visualise the male urethra?
The adult male urethra can be visualised by 2 main techniques:
- Ascending urethrography = contrast is injected into the meatus and images obtained of the urethra
- Descending urethrography = after filling the bladder with contrast the catheter is removed and images are taken of the urethra during micturition
In both techniques, the entire urethra must be studied.
