RENAL MASSES RADIOLOGICAL ASSESSMENT
Category: Urology
Abstract : Radiological assessment of renal masses Abdominal ultrasound The
first-line investigation for a patient with loin pain or a suspected renal mass.
The size resolution for renal masses is 1.5cm, exhibiting variable echo
patterns. Ultrasound may also detect renal cysts, most of which are simple:
smooth-walled, round or oval, without internal echoes and complete transmission
with a str
Radiological assessment of renal masses
Abdominal ultrasound
The
first-line investigation for a patient with loin pain or a suspected renal mass.
The size resolution for renal masses is 1.5cm, exhibiting variable echo
patterns. Ultrasound may also detect renal cysts, most of which are simple:
smooth-walled, round or oval, without internal echoes and complete transmission
with a strong acoustic shadow posteriorly.
If the cyst has a solid intracystic
element, septations, an irregular or calcified wall, further imaging with CT is
indicated.
CT scan
If a renal mass is detected, a thin slice CT scan
before and after contrast is the most important investigation. In general, any
solid enhancing renal mass is considered a renal carcinoma until proven
otherwise. Even relatively avascular renal carcinomas enhance by 10 - 25
Hounsfield units.1 Occasionally, an isodense but enhancing area of kidney is
demonstrated (pseudotumour ) and may correspond to a harmless hypertrophied
cortical column (of Bertin) or dysmorphic segment. CT may mislead with respect
to liver invasion (rare) due to partial volume effect ; real-time ultrasound is
more accurate. Lymphadenopathy >2cm is invariably indicative of
metastases.
Bosniak developed the following radiological classification of
renal cysts:
- Uncomplicated, simple (see above criteria); benign; no
follow-up if asymptomatic
- Minimally complicated; septa, calcification,
hyperdense (contain blood); benign but require radiological follow-up
-
Complicated; irregular margin, thickened septa, thick irregular calcification;
indeterminate, surgical exploration indicated unless there is history of trauma
or infection
- Large, irregular cyst margins with solid components
internally; cystic renal carcinoma until proved otherwise; surgery
required
MRI with gadolinium contrast
may be used for imaging the
inferior vena cava, locally advanced disease, renal insufficiency, or for
patients allergic to iodinated contrast. Renal arteriography is seldom used in
the diagnostic setting, but may be helpful to delineate the number and position
of renal arteries in preparation for nephron-sparing surgery or surgery for
horseshoe kidneys.
Fine needle aspiration/needle biopsy
Ultrasound or
CT-guided fine needle aspiration (FNA) or needle biopsy in the investigation of
renal masses is of limited value because of the accuracy of modern
cross-sectional imaging, false -ve biopsy results (5 - 15%), plus risks of
haemorrhage (5%) and tumour spillage (rare). FNA is useful for aspiration of
renal abscess or infected cyst, or to diagnose suspected lymphoma or metastatic
lesions.
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