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ABDOMINAL ULTRASOUND
E
F
Figure 7.4 cont’d (E) TS through the RK demonstrating a baggy extrarenal pelvis. The PCS remains undilated, and
this should not be confused with hydronephrosis. (F) Hypertrophied column of Bertin (arrows).
Renal humps
These are areas of renal cortex, which form a bulge
in the renal outline. Like the hypertrophied column
of Bertin, a hump may mimic a renal mass.
Careful scanning can usually solve the dilemma as
the cortex remains constant in thickness. The most
usual manifestation is the splenic hump on the left
kidney, which is a flattening of the upper pole with
a lateral prominence just below the margin of the
spleen. Humps are basically a variation in the shape
of the kidney rather than an area of hypertrophied
tissue.
RENAL CYSTS AND CYSTIC DISEASE
Cysts
The most common renal mass is a simple cyst
which can be found in up to 50% of the population,
the incidence increasing with age. Most cysts
are asymptomatic and may be solitary or multiple.
Generally they are peripheral but may occur within
the kidney adjacent to the renal pelvis. A parapelvic
cyst may be difficult to distinguish from pelvicalyceal
dilatation, a calyceal diverticulum or an extrarenal
pelvis and careful scanning is required to differentiate.
A parapelvic cyst may be the cause of a
filling defect on intravenous urogram (IVU) and
CT can differentiate a cyst from a diverticulum if
necessary, as the latter will fill with contrast.
Occasionally cysts can haemorrhage causing pain.
Large cysts, particularly of the lower pole, may be
palpable, prompting a request for an ultrasound
scan.
Ultrasound appearances
Like cysts in any other organ, renal cysts display
three basic characteristics: they are anechoic, have
a thin, well-defined capsule and exhibit posterior
enhancement. It can be difficult to appreciate the
posterior enhancement if the hyperechoic perirenal
fat lies distal to the cyst; scanning from a different
angle (Fig. 7.5) may be helpful. Haemor-rhage or
infection can give rise to low-level echoes within a
cyst and in some cases the capsule may display calcification.
Whilst a solitary, simple cyst can almost certainly
be ignored, cysts with more complex acoustic
characteristics may require further investigation,