Page 261 - Medicine and Surgery

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Chapter 6: Disorders of the kidney 257

examination should be performed to look for pelvic uretericorificesandcontrastinjected.Cystoscopymay
disease. also visualise a cause of obstruction.
U&Es may demonstrate renal impairment. FBC may
Macroscopy show a normochromic, normocytic anaemia of chronic
An acutely obstructed kidney is swollen, but chronic disease.
damage to the kidneys may make it small and shrivelled. Urine should be sent for microscopy and culture, ur-
gently if infection is suspected.
Complications
Infection above the level of obstruction can cause Management
pyelonephritis (pyonephrosis is the term for an infected, It is important to diagnose and treat urinary tract ob-
obstructed hydronephrosis) or cystitis, and patients can struction quickly, as delayed treatment can cause irre-
become very unwell due to pain, fever and sepsis. versible loss of renal function.
Bladder catheterisation should be performed if blad-

Investigations der neck obstruction is suspected. Percutaneous
The investigation of choice is a renal ultrasound (USS), nephrostomy is indicated for ureteric or pelvi-ureteric
as this will diagnose obstruction and its cause in most junction obstruction. Acute renal failure and its
cases. If the kidneys are poorly visualised CT scanning is complications require appropriate treatment (see
a useful substitute. In renal obstruction USS and CT will page 234).
show a hydronephrosis, i.e. dilated renal pelvis and ca- Infection of an obstructed system requires drainage
lyces (also called pelvicalyceal dilatation) and/or dilated of the system, together with high dose intravenous
ureters. However dilatation may not be seen if there is antibiotics.
oligo-/anuria, in the first 72 hours before the systems Relief of the obstruction can cause marked polyuria,
have dilated, or if there is retroperitoneal fibrosis en- as much as 500–1000 mL/hour. Some of this is due
casing the ureters. False positives may occur on USS or to loss of concentrating ability of the tubules, which
CT because of cysts, staghorn calculi or a dilated baggy may take a few days to recover, but often the patient is
low-pressure system, which may be mistaken for an ob- also fluid overloaded. Careful fluid balance monitor-
structed system. Therefore, if there is doubt, one of the ing is needed, to avoid hypotension or prerenal failure
following may be required: during this phase.
Intravenous urogram (IVU). This is very useful, par-

ticularlyinacuteobstructionbeforethereisdilatation,
Pelviureteric junction obstruction
as it shows contrast ‘held up’ by the obstruction and (idiopathic hydronephrosis)
may show the lesion as a space-filling defect such as a
radio-lucent stone or a papilla. A plain film should be Definition
donefirsttolookforradio-opaquestones.IVUshould Narrowing of the pelviureteric junction (PUJ) which is
be avoided in renal failure. acommon cause of gross hydronephrosis.
Radionuclide study such as MAG3 can show impaired

uptake, delayed peak activity and delayed transit time Age
on the side of the obstruction. This picture is also seen Likely to be congenital but may present at any age.
inanycauseofrenalimpairment,butifitreverseswith
adose of diuretics, then obstruction is not present. Aetiology/pathophysiology
As part of the management percutaneous nephros- The cause is unknown. There appear to be excessive col-

tomy can be placed and then anterograde pyelogra- lagen fibres around the muscle cells at the PUJ, which
phy and ureterography can be performed through the prevent their proper relaxation, so that there is a nar-
nephrostomy. This avoids intravenous contrast. Alter- rowed segment of the ureter at the exit of the renal pelvis.
natively retrograde ureterography can be performed, This causes gross dilatation ‘hydronephrosis’ of the renal
using a cystoscope. Catheters are introduced into the pelvis.