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Deivasigamani et al. Mini-invasive Surg 2023;7:9 https://dx.doi.org/10.20517/2574-1225.2022.99 Page 3 of 19

caused by ice formation, cellular stress response (“kill switch” mechanism), necrotic and apoptotic cascades,
[8]
vasoconstriction leading to stasis during the thawing process, and activation of immune responses .
Extracellular ice crystal formation initiates the processes of cell death caused by CA, which results in
hyperosmosis and cell dehydration, followed by denaturation. Ice crystal development causes mechanical
damage to the cell membrane owing to shearing forces; intracellular ice crystal formation causes permanent
cell damage. During thawing, vasoconstriction causes a loss of blood flow, further leading to coagulative
necrosis and subsequent inflammation resulting in the release of cytokines that causes apoptosis of the
[8]
damaged cells . Figure 1 offers a comprehensive depiction of several CA mechanisms of action.
Cryoablation procedure
Imaging
Open CA, laparoscopic CA (LCA), and percutaneous CA (PCA) are all guided by imaging during the
procedure to assess cryoprobe placement and ice ball formation; imaging modalities utilized for CA
guidance include ultrasonography, a computerized tomography (CT) scan, or magnetic resonance imaging
(MRI). The edge of the ice ball can be seen on imaging; however, the edge of the ice ball has a temperature
of 0 °C, so the ice ball visualized on imaging must extend beyond the intended treatment zone to ensure the
entire treatment zone achieves a sufficiently lethal nadir temperature of approximately -20 °C to -40 °C .
[9]
Cryoprobes and currently utilized cryogens
The cryoprobes are inserted into the tumor with their tips extending just beyond the tumor margin. The
appropriately sized ice ball for the patient’s target tissue is accomplished using one or more cryoprobes of
the appropriate size for the given lesion. Currently, available commonly used cryoprobes come in diameters
ranging from 1.5 mm to 3.8 mm and are selected to form ice balls of spherical or elliptical shapes of various
sizes. An access sheath can often be utilized to avoid repetitive skin punctures while allowing for multiple
entries of needles for biopsy and cryoprobes [10,11] . The cryoprobe achieves rapid cooling because it contains a
Joules-Thompson chamber that allows highly pressurized argon gas to expand, causing the cryoprobe to
reach extremely cold temperatures that are then transferred to the target tissue via conduction. Thawing can
be accelerated by injecting helium gas into the chamber or using an electrical heating element. The
cryoprobes receive gas from the argon and helium tanks via controlled pressure regulators .
[10]

Precautionary measures
[12]
Warming the skin entry points may be necessary to reduce collateral skin injury . To achieve technical
success, probes should be inserted parallel to one another with spacing to allow for adequate ice ball overlap
[9]
so that a uniformly low temperature is reached at the target tissues . In the case of LCA, if post-procedural
bleeding is encountered, it can be controlled with argon beam coagulation and hemostatic agents. If
neighboring organs such as the bowel are too close to the target renal lesion, routinely used techniques to
help create a safer distance include patient repositioning, hydro-dissection, or gas insufflation with
CO 2 [9,11,12] . An additional technique to help create additional space between the target renal lesion and
adjacent organs is to use the cryoprobe itself to provide retraction or torque to the kidney itself . When the
[13]
renal lesion is close to the proximal ureter, the patient may benefit from the placement of a ureteral stent
[14]
and pyeloperfusion to protect the ureter from freezing temperatures . For upper pole tumors treated with
PCA, there is an increased risk of iatrogenic pneumothorax if the needle path transverses the pleura, this
can sometimes be mitigated with patient positioning and an oblique needle trajectory, but sometimes a
pneumothorax is unavoidable and a small chest tube can be left in place at the conclusion of the
[15]
procedure .