"Is CT mandatory for the detection of residual stone fragments
following PCNL?"
Petros Sountoulides1, Linda Metaxa2, Luca Cindolo3
1
2
3
Urology Department, General Hospital of Veria, Greece
Radiology Department, General Hospital of Veria, Greece
Urology Department, “S.Pio da Pietrelcina” Hospital Vasto, Italy
The introduction of minimally invasive endourological procedures as SWL, URS and PCNL for upper
urinary stone disintegration has closed the curtain on the era of open surgery for upper urinary tract
stones where complete stone eradication was the rule. This shift to minimally invasive procedures has
led to the introduction of new terminology such as stone-free rates and residual stone fragments, the
presence of which following treatment was considered an acceptable therapeutic end point. This review
intends to focus on the current role of CT for the detection of residual lithiasis following PCNL for kidney
stones. Questions to be answered include the definition and significance of clinically insignificant residual
lithiasis and the best imaging study to detect those fragments
A comprehensive electronic literature search was conducted in january 2012 using the Medline database
to identify all publications relating to residual fragments, CTscan post PCNL, renal stones.
The available studies on the rate of residual fragments post-PCNL have presented conflicting results,
ranging from 8% to 80% depending on the definition of “residual lithiasis” and the imaging modality
used for residual stone detection. Although there is no consensus regarding the maximum size or stone
characteristics, clinically insignificant residual fragments(CIRFs) following either SWL or PCNL are
defined as residual fragments smaller than 4 mm or 5mm in diameter associated with sterile urine in an
otherwise asymptomatic patient with no evidence of upper tract obstruction.
Despite the fact that CT is considered essential for the diagnosis and exact localization of stones, and
has been used for the creation of percutaneous tracts in PCNL, its routine use for the post-PCNL
detection of residual stones has not been established. There is evidence that routine application of postPCNL CT provides additional advantages compared to other imaging modalities. On the other hand the
issues of cost, availability of CT scanners and radiation exposure along with the acceptable sensitivity,
cost and availability of other imaging studies has raised doubts as to whether CT should be the routine
imaging study following PCNL.
Stone-free status following PCNL is an elusive concept. The size and location of post-PCNL RFs predicts
the development of stone related events. Currently the need of routine postoperative CT imaging after
PCNL remains controversial. There is evidence to support that fragments smaller than 1-2 mm probably
do not require a second look, whereas RFs larger 3-4 mm are more likely to cause a stone-related event
and require secondary surgical intervention. There is strong evidence that routine follow up with
Unenhanced Helical CT is necessary for patients where complete eradication of stones is deemed
essential due to a more pronounced risk of recurrent stone formation.