The position of the vermiform appendix in relation to the caecum is varied, with a pelvic orientation the most commonly noted. The appendix may be located in all forms of external hernias.5
The two most frequently documented locations are inguinal and femoral, eponymously known as Amyand's and de Garengeot's hernias respectively. Additionally, the appendix has been reported in left-sided inguinal, umbilical and Spigelian hernias.6
Hypotheses for these unusual anatomical locations include malrotation during embryonic development, previous surgery and hypermobility of the caecum.7
Unlike routine appendicitis, extraluminal compression has been proposed as the explanation for acute inflammation in hernial appendicitis. The cause of extraluminal compression varies from a narrowed hernial neck causing direct ischaemia to repeated trauma creating inflammatory adhesions.
Almost all intra-abdominal organs have been described in incisional hernias, including stomach, small bowel, colon, ovaries and fallopian tube. To the best of our knowledge, Case 1 is the first reported case of acute appendicitis in an upper midline incisional hernia. We speculate that the patient's previous surgery created inflammatory adhesions of the small bowel leading to the midline location of the appendix. Pre-operative diagnosis of hernial appendicitis is difficult to establish. This difficulty arises as the classic symptoms of acute appendicitis are not apparent due to the entrapment of the appendix in the hernial sac. Pre-operative CT may be of benefit in demonstrating the presence of the appendix within unusual incisional hernias. The complexity of the surgical background may influence the decision to request pre-operative imaging. CT diagnosis of a vermiform appendix in a right transverse incisional hernia has been reported in two cases.7
In each of these cases, the patient had undergone renal transplantation. Of interest, incisional hernia formation following renal transplantation poses a unique problem as the defect tends to lie deep within the abdominal wall musculature rather than through the external oblique aponeurosis.8
Laparoscopic surgery has several well documented advantages over open surgery including shorter hospital admission, decreased analgesia requirements and improved cosmesis. The advent of laparoscopic surgery has resulted in newly described surgical complications including port-site hernia formation. PSH formation is the most common complication following laparoscopic surgery, with a reported incidence of 0.8–2.8%.9
PSH arise from fascial defects originating at trocar entry sites. Risk factors for PSH formation include trocar size, incomplete closure of fascial defects and organ retrieval through the port. To the best of our knowledge, Case 2 is the first reported case of acute appendicitis within a 5 mm port site hernia.
It is routine surgical practice to close fascial defects in port sizes ≥10 mm as the port size correlates directly with the incidence of hernia formation.10
A recent systematic review of 118 PSH identified that 96% arose in port sites of a minimum size of 10 mm.11
There is no published evidence for routine closure of 5 mm port sites in adults.9
Nevertheless, identified risk factors for PSH in 5 mm port sites include age greater than 60 years, prolonged trocar manipulation and surgery greater than 90 min in duration.9
In Case 2, a Redivac®
suction drain was placed and externalised through a 5 mm port in the right iliac fossa. This drain was removed two days later. We postulate that the combination of negative suction pressure and the partial vacuum created by removal of the drain made the appendix more susceptible to herniation. Herniation of a non-inflamed appendix following the removal of a drain through a 5 mm port site has been described. It was hypothesised that the appendix was directly adherent to the intra-abdominal component of the suction drain.12
Interestingly, the use of a drain placed through a 5 mm port site has been suggested as a risk factor for PSH and the practice of externalising the drain through a 5 mm port site is controversial.13
The appearance of an inflamed appendix within an incisional hernia potentiates the complexity of two routinely performed surgical procedures. Difficulty relates to potential violation of aseptic principles by excision of a faecally contaminated organ in a clean contaminated wound. The treatment of hernial appendicitis consists of immediate appendicectomy through the herniotomy with subsequent primary hernia repair.14
The macroscopic inflammatory appearance of both appendices in Cases 1 and 2 was a clear indication for appendicectomy. Conversely, incidental appendicectomy in the case of a non-inflamed appendix within a hernial sac is not recommended.15
The method of primary repair of an incisional hernia containing an inflamed appendix is debatable and is determined by the extent of the underlying inflammatory process. Utilisation of synthetic mesh for incisional hernia repair decreases recurrence rates, but increases the risk of wound infection when compared to open suture repair.16
Considering the rarity of incisional hernia appendicitis, most clinical experience arises from the management of Amyand's hernia. Several authors state that a prosthetic mesh should not be used to repair contaminated defects within the abdominal wall with an increase in recurrence rates observed when compared to clean wounds.17
Prosthetic mesh can be used safely in the absence of gross contamination or perforation following hernial appendicitis.18
Synthetic biological mesh was utilised in Case 1, as the size of the hernial defect made it impossible to achieve primary closure otherwise. Mesh repair to close a large right inguinal incisional hernial defect in the presence of an inflamed appendix has been reported.19
New biological meshes, such as human acellular dermal matix, have been evaluated in contaminated surgical fields with promising results.20
However, the expense and limited international experience with the use of biological meshes may restrict their use in clinical practice.