Congenital
abnormalities of the renal pelvis and ureter
Duplication of
a renal pelvis
Duplication of a renal pelvis (Fig. 64.8) is the most common congenital abnormality of the upper renal tract and is found in about 4 per cent of patients. It is usually unilateral and is slightly more common on the left. The upper renal pelvis is relatively small and drains the upper group of calyces; the larger lower renal pelvis drains the middle and lower groups of calyces.
Duplication of
a ureter
Duplication of a ureter is found in about 3
per cent of excretion urograms. The ureters often join before they reach the
bladder, usually in the lower third of their course (Fig.
64.9) and have a
common ureteric orifice. Less commonly the ureters open independently into the
bladder, in which case the ureter from the upper pelvis opens distal and medial
to its fellow (Fig. 64.10).
Clinical
features
Duplication of the renal pelvis or ureter is
often a chance finding on renal imaging but infection, calculus formation and
pelviureteric junction obstruction are more common than in normal kidneys. One
of the moieties may be dysplastic and nonfunctioning. Where the two ureters
open separately, the lower orifice is liable to be abnormal in function or
position. Failure of the normal valvular mechanism at the ureterovesical
junction may lead to urinary reflux and, if there is associated infection,
damage to the parenchyma of the upper moiety. An ectopic second ureteric opening
is a rarity but it may cause puzzling symptoms.
In the female an ectopic ureter opens either
into the urethra below the sphincter (Fig. 64.11) or into the vagina. The
diagnosis can often be made from the history alone and is confirmed by excretion
orography. A girl or woman who has dribbled urine for as long as she can
remember, despite the fact that she has a desire to void and indeed voids
normally, probably has an ectopic oreteric orifice. The orifice is often
difficult to see because it is guarded by a valve: it may help to give an
intravenous injection of a dye such as indigocarmine to colour the urine leaking
from it.
In
the male patient the aberrant opening is above the external urethral sphincter
so the patient is continent. The ureteric orifice at the apex of the trigone,
the posterior urethra, in a seminal vesicle or in an ejaculatory duct is
likely to be functionally abnormal and infection is the most common
complication.
Treatment
Asymptomatic duplication of the kidney is a
harmless variant and does not require treatment. If one moiety is severely
diseased or atrophic, partial nephrectomy is usually simple and effective. An
ectopic ureter in the female frequently drains hydronephrotic and chronically infected renal
tissue, which is best excised. Rarely, the
incontinence can be cured and renal function preserved by implanting the ectopic
ureter into the bladder or by joining it to its fellow.
Congenital megaureter
Congenital megaureter is a curious and
uncommon condition which may be bilateral and is often associated with other
congenital anomalies. A functional obstruction at the lower end of the ureter
leads to progressive dilatation and a tendency to infection. The ureteric
orifice appears normal and a ureteric catheter passes easily. Reflux is not a
feature of the untreated condition but is almost inevitable if the ureteric
orifice is opened endoscopically to make it drain. Definitive surgical treatment
involves refashioning the lower end of the affected ureter so that a tunnelled
reimplantation into the bladder can be done to prevent reflux.
Postcaval
ureter
The right ureter passes behind the inferior
vena cava instead of lying to the right of it. If this causes obstructive
symptoms, the ureter can be divided and rejoined in front of the cava using a
long oblique anastomosis without tension. Unusually, the retrocaval portion of
the ureter is fibrotic and must be excised.
Ureterocele
Ureterocele is a cystic enlargement of the
intramural portion of the ureter thought to result from congenital atresia of
the ureteric orifice. Although present from childhood, the condition is often
unrecognised until adult life. The ‘adder head’ on excretory orography (Fig.
64.12) is typical. Usually the cyst wall is composed of urothelium only and the
diagnosis is confirmed by the cystoscopic appearance of a translucent cyst
enlarging and collapsing as urine flows in from the upper ureter (Fig.
64.13).
Treatment should be avoided unless there are symptoms arising from infection
and/or stone formation. Ureterocele is most common in women; occasionally the
cyst may cause obstruction to the bladder outflow by prolapsing into the
internal urethral opening.
Endoscopic
diathermy incision is usually all that is required for treatment of a
symptomatic ureterocele, although a micturating cystogram is advisable to detect
postoperative urinary reflux. In advanced unilateral cases with hydronephrosis
or pyonephrosis, nephrectomy may be appropriate.