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Berger. Mini-invasive Surg 2023;7:24 https://dx.doi.org/10.20517/2574-1225.2023.30 Page 3 of 10

was centrally incised to allow the passage of the stoma-related bowel and placed in a retromuscular position.
The diagnosis of parastomal hernia was established by clinical investigation. After 27 patients in each group,
the ethics committee stopped the trial because the rate of parastomal hernia was drastically reduced in the
mesh group. After one year, 13 out of 26 patients without a mesh developed a hernia compared with one
out of 21 patients with a prophylactic mesh. It should be pointed out that the described technique is similar
to the “keyhole technique” originally described for the repair of parastomal hernia. During the following
years, a lot of observational and randomized controlled studies were published, leading to the Guidelines of
the European Hernia Society in 2017, which strongly recommend a prophylactic mesh during the creation
of end colostomies . Further analyses of existing randomized studies, including newer ones, were not able
[21]
[22]
to find differences favoring the prophylactic use of meshes . The authors explained the inconsistent results
with different techniques in terms of different meshes, different mesh placements, and different diagnostic
tools and concluded that based on the available data in 2020, a prophylactic mesh could not be
recommended. In a more recent systematic review, McKechnie et al. calculated a significant reduction of
parastomal hernia in the mesh group . However, analyzing the studies published during the last five years,
[23]
there was no difference in favor of prophylactic meshes anymore.

How can these obvious contradictions be explained? The diagnostic value of the clinical examination is
[24]
lower compared to computed tomography (CT) or ultrasound imaging . Moreno-Matias previously
[9]
described this aspect when establishing the radiologically based classification of parastomal hernia . He
could also point out that the clinical relevance of clinically established hernias is more pronounced than in
cases with only radiologically diagnosed hernias. A Finnish randomized controlled trial (RCT) using
intraperitoneal keyhole prophylaxis demonstrated a clinical benefit that was no more present when patients
[25]
with radiologically diagnosed parastomal hernia were included . Another aspect concerns the observation
period. It seems to be clear that the prophylactic mesh delays the occurrence of parastomal hernia . The
[26]
long-term results of this RCT after five years showed no statistical difference concerning the rate of
parastomal hernia between the groups; however, there was a clear delay of the onset of the hernia in the
mesh group. Generally, the mesh groups proved to be less symptomatic, underlining the above-mentioned
results of fewer symptoms when the hernia is only detected by CT. Additionally, the methodology of
performing systematic reviews and meta-analyses is subject to debate. In a comprehensive review, Garcia-
Alamino et al. found that eight out of 14 systematic reviews meeting the inclusion criteria and dealing with
the prevention of parastomal hernia had a generally low quality with a high risk of bias .
[27]
Technical aspects should also be kept in mind, as most studies are based on the keyhole technique. In this
technique, a synthetic non-resorbable mesh with a central hole, usually incised by the surgeon himself, is
placed either retromuscularly or intraperitoneally. However, for the repair of existing parastomal hernias,
the keyhole technique was no more recommended. There is the only hypothetical explanation that the
shrinkage of the mesh induces an enlargement of the central opening, ending up in a recurrent hernia. This
hypothetical explanation may also be true for the prophylaxis of parastomal hernia. When taking into
account that small-pore meshes do shrink more than large-pore structures , there is another point of
[28]
heterogeneity in these studies.

In a few observational studies, the role of a funnel-like mesh in preventing parastomal hernia is described
with promising results. The material used for the mesh is polyvinylidene fluoride, which exhibits some
advantages over polypropylene not only in terms of foreign body reaction [28,29] . The main difference to the
above-described studies is the fact that this technique is definitely not a keyhole technique, as shown in
Figure 1. The mesh is implanted intraperitoneally with the funnel surrounding the stoma loop for 2.5 or 4
cm, depending on the structure used. When believing the above-described hypothesis about the keyhole