9%20ECOGRAFIA%20ABDOMINAL%20COMO%20CUANDO%20DONDE

THE RENAL TRACT 167
Table 7.1
Source of obstruction
Intrinsic factors
Stones
Tumour
Blood clot
Papillary necrosis
Infective processes
Stricture
Fungal balls
Tuberculosis
Congenital
Idiopathic PUJ
obstruction
Posterior urethral
valves
Ureterocoele
Outflow obstruction
Prostate enlargement
Urethral stricture
Extrinsic pelvic mass
Cervical carcinoma
Causes of renal tract obstruction
Characteristics
Accompanied by renal colic.
May be situated anywhere
along the renal tract
In the bladder, PCS or ureter
From infection or trauma
Sloughed papillae can travel
down the ureter, causing
obstruction
Caused by chronic, repeated
infection
Rare
Usually unilateral. PCS
dilatation only
Entire renal tract dilatation.
Frequently diagnosed
antenatally
Unilateral hydronephrosis
with hydroureter
Benign or malignant
May be iatrogenic, congenital
or as a result of infection.
Accompanied by disturbed
micturition
Proximity to the ureters
causes obstruction
Endometriosis
Endometriotic lesions adhere
to the peritoneal and/or
ureteric surfaces, causing
compression
Others: lymphadenopathy, Always scan the kidneys to
inflammatory bowel exclude obstruction when a
masses, gynaecological pelvic mass is present
masses
Iatrogenic
Postsurgical procedure Ligation of ureters in
gynaecological procedures
Trauma
Can cause a stricture of the
ureter or can cause the renal
tract to be blocked by blood
clot from damage to the
kidney
PCS = pelvicalyceal system; PUJ = pelviureteric junction.
Further management of renal obstruction
In the majority of cases the exact level and cause of
obstruction are difficult to identify on ultrasound.
Confirmation of the cause and identification of the
exact level is traditionally best established on
IVU; 10 however CT IVU is becoming a rapidly
universally adopted first-line investigation. 11
A plain abdominal X-ray is useful in confirming
the presence of calculi in the renal tract, but ultrasound
may demonstrate stones which are nonopaque
on X-ray; CT is probably the best overall
test for stone detection.
It is important to assess the function of the
obstructed side, as a chronic, longstanding
obstruction with no residual function cannot be
treated, but a kidney which still has function is
worth saving. A DTPA scan can assess the relative
functions of the obstructed and non-obstructed
side.
Percutaneous nephrostomy (the placing of a
tube into the PCS to drain the urine) in the case
of unilateral obstruction is performed to relieve
the obstruction, minimizing damage to the kidney
and maintaining renal function and drainage.
This may be done under either ultrasound or fluoroscopic
guidance or a combination of both.
The decision of whether to proceed to nephrostomy
or cystoscopic stent will depend upon
patient presentation and local factors and
policies.
Pyonephrosis
Pyonephrosis is a urological emergency. An
obstructed kidney is prone to become infected.
High fever and loin pain can suggest obstructive
pyonephrosis. Pus or pus cells may also be detected
in the urine.
Low level echoes can be seen within the
dilated PCS on ultrasound, and may represent
pus. Sometimes, however, the urine may appear
anechoic, despite being infected. The clinical
history should help differentiate pyo- from simple
hydronephrosis (Fig. 7.13A). Percutaneous
drainage by ultrasound or fluoroscopically guided
nephrostomy is usually necessary, partly as diagnostic
confirmation and partly as a therapeutic
procedure.