Xanthogranulomatous pyelonephritis,
or XP in short,
is a rare form of chronic renal infection,
making up around 1% of all chronic pyelonephritis.
Even more so in paediatric population,
as patients with this disease are usually between 50 and 70 years old,
with women said to be affected up to 4 times more often.
The core of XP are slow but progressive changes that include destruction of renal parenchyma,
which is then replaced with lipid-filled macrophages.
It is believed to be a response to recurring subacute inflammatory processes – ones that may have had an atypical course and consequently pose quite a challenge for the examining clinicist.
What’s more,
symptoms presented by XP patients are mostly non-specific (e.g.
palpable mass,
fever,
weight loss,
flank pain,
hematuria,
loss of appetite),
thus further increasing the clinical difficulty.
Therefore,
past medical documentation contributes much to the interpretation of imaging findings: over 80% of patients with XP have a history of multiple renal infections.
P.
mirabilis and E.
coli make up the majority of pathogens involved and are detected in up to 95% patients at the time of diagnosis.
Still,
the exact cause of XP is yet to be determined – beside bacterial infections,
other factors include urinal obstructions (mainly due to staghorn calculi),
vesicoureteral reflux,
kidney ischaemia and lipid anomalies.
Usually,
only one kidney is involved,
and there is no predilection to either side.
Standard treatment for this disease is nephrectomy – in paediatrics preferably partial,
but this depends on the staging and area affected by the process.
The use of antibiotics has been discussed over years,
with the conclusion being it is not viable as a sole treatment.
The postoperative prognosis is remarkably good,
as opposed to other diseases that may mimic XP.
However,
if left untreated,
the mortality rate is even up to 10%.