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Chapter 6: Clinical 229

can demonstrate its size, any asymmetry, or suspicious Computed tomography (CT)
areas. USS-guided prostatic biopsy may be performed. In most cases, the diagnostic ability of CT is improved
by giving intravenous contrast, but as noted above, cer-
Intravenous urogram/pyelogram (IVU/IVP) tain precautions should be taken.
This is commonly used in the investigation of renal colic, Renal cysts and masses – CT can help differentiate
although it is also a useful tool in assessing the anatomy benign cysts from malignancy.
of the urinary tract. It can be used for staging in all types of genitourinary
Aplainfilmistakenfirstasthecomparisonfilm,thena malignancy, including renal cell carcinoma, bladder
slow intravenous injection of an iodine-containing con- cancer and testicular tumours.
trastdyeisgiven(prophylaxiswithhigh-dosesteroidsare It is able to detect radiolucent stones missed on plain
givento asthmatics and those with a known allergy to X-ray.
iodine, to prevent an allergic reaction). Serial X-rays are In polycystic kidney disease it can be useful if one cyst
then taken, which show the passage of the dye through is thought to be infected or malignant.
the renal parenchyma, outlining the kidneys clearly. The
dye then normally passes rapidly into the ureters. If there
Nuclear medicine scans
is obstruction, dye will be ‘held-up’ on one or both sides.
Anon-nephrotoxic radioisotope is given intravenously,
The exact site of obstruction can often be seen with di-
which is taken up and excreted by the kidneys. Imaging
latationabove.Afillingdefectwithintheuretersuggestsa
may be ‘static’ (for anatomical detail), or ‘dynamic’ (for
radiolucent stone or tumour. Pre and post-voiding films
function).
are taken to look for any filling defects in the bladder Static DMSA scans are more sensitive than IVU to
(stone or tumour), and to assess bladder emptying.
look for scarring and ischaemia.
IVU/IVP should be avoided in significant renal im-
Dynamic DTPA and MAG3 are used to look for renal
pairment because of nephrotoxicity and poor dye ex-
parenchymal disease and obstruction. To look for ob-
cretion makes the test difficult to interpret. All patients
struction, furosemide is given – the radioisotope will
should be well hydrated. Diabetics are particularly at risk
flush out promptly if there is no obstruction.
of nephrotoxicity, metformin should be stopped prior to
giving contrast.
Magnetic resonance imaging/angiography
(MRI/MRA)
Other urographic studies
MRI is sometimes used to further assess renal cysts
These two methods are more invasive than IVU/IVP,
and solid lesions. It is also used with gadolinium
but as the dye is given directly into the urinary tract,
contrast to perform angiography (MRA) as a non-
avoidstheriskofnephrotoxicityandallergy.Therapeutic
invasive alternative to renal angiography. Gadolinium is
stents may be placed as part of the procedure to relieve
non-nephrotoxic.
obstruction.
1 Nephrostomy and antegrade pyelography – for upper
tract obstruction, a fine-bore catheter is introduced Renal angiography
intothedilatedrenalpelvispercutaneouslyunderlocal This is mainly performed for suspected renal artery
anaesthetic. This relieves the obstruction and allows stenosis. A sheath is placed in the femoral artery, and
urine to drain out. Contrast is then injected through an arterial catheter passed to the aorta. Each renal artery
the catheter, to demonstrate the cause and site of is selectively catheterised and contrast injected. Conven-
obstruction. tional or digital subtraction angiography (DSA) may be
2 Retrograde pyelography – following cystoscopy, a used. DSA uses less contrast, which reduces the risk of
catheter is passed into the ureteric orifice normally contrast nephropathy (acute renal failure secondary to
under general anaesthetic. Contrast is injected and the nephrotoxic contrast). Other complications include
images are obtained. This is useful for defining lower cholesterol emboli and arterial dissection. Percutaneous
ureteric lesions such as stones, and to look for transi- renal angioplasty (PRA) and renal artery stenting can
tional cell carcinoma of the ureter. also be performed.