Incisional hernia is defined as a defect in the abdominal wall in placements of postoperative wounds. They are recognizable by clinical examination and/or by imaging tests. The incidence of trocar site incisional hernia has been poorly documented over the years which may be due to the paucity of symptoms and to the lack of long-term postoperative follow-up since the pathology that leads to the laparoscopic surgery is usually benign and no further follow-up is deemed necessary. Consequently, in most situations the follow-up is not sufficient to detect TSIH.
In the present study it was hypothesized that the real incidence of trocar site incisional hernia, when properly assessed, could be higher than is currently believed. Therefore, we aimed to analyze the actual TSIH incidence in our environment, measured by both physical and radiological exams, the latter being considered the gold standard technique (8).
Incidence. In our series, a high TSIH rate was found. The incidence detected by physical examination was 27.6%, compared to 23.7% when assessed by ultrasound. After having been a neglected issue, during the last decade, few authors have addressed the incidence and risk factors of TSIH after laparoscopic surgery. In 2010, Chiong et al published a retrospective analysis of 1055 patients who underwent surgery due to urologic tumors and found a TSIH rate of 0.66%. All of them were clinically suspected and radiologically confirmed by computed tomography (9). In 2011, a systematic review based on 19 prospective and retrospective studies, which included a total of 30568 adults and 1098 children, documented a TSIH incidence of 0.5-2% (10). In 2013, a retrospective review of 500 patients who underwent laparoscopic and robotic gynecological surgery documented only 3 cases of TSIH (0.6%), diagnosed on physical examination with radiologic confirmation (1 of them required emergency reoperation for hernia reduction and the other two presented asymptomatic bulges), with an average length of time to TSIH appearance of 21 days (4). In 2011, in a narrative review, Comajuncosas et al. described an incidence of 0.18–2.8%, but the authors concluded that the actual incidence was possibly higher (11). Three years later, the same group published a prospective observational study including 241 patients, with a follow-up of 46.8 months, showing an incidence of 25.9%. In this study, TSIH were identified mainly with clinical examination, but an abdominal ultrasound was carried out in doubtful cases (12).
Location. In spite of using a systematic protocol for closure, most of TSIH cases were located in the 10 mm incisions at the umbilical level. The TSIH rate can change depending on the type of trocar and its location. TSIH have been described at any location, but those situated at the10mm trocar are the most frequent(9, 10, 12–14). It seems that for 5 mm trocars facial closure should not be necessary, but for ≥ 10 mm trocars it would be mandatory. Keeping in mind some previous studies (4, 6, 10, 11) and the results if this study, the standard closure technique may not be enough.
Risk factors. We found that obesity and age over 70 years were independent risk factors for the appearance of TSIH. In open surgery, some risk factors for incisional hernias, either individual or dependent on the surgical technique, are well documented. Factors including abdominal aortic aneurysm surgery, obesity, cachexia, advanced age, male sex, COPD, anemia, smoking, steroid treatment, and immunosuppression. (1, 10, 12, 15, 16). duration of the procedure, presence of previous umbilical hernia, diabetes mellitus, or smoking, have been described as possible risk factors for TSIH (11, 17) but according to our data only age and obesity can be confirmed as risk factors for TSIH.
Diagnosis. Clinical examination overdiagnoses TSIH and in consequence, it might be necessary to complement it with an ultrasound exam to achieve an accurate diagnosis. A systematic review carried out in 2018 which was led by Kroese et al. (18) reinforces this idea as they concluded that the use of imaging modalities would usually result in more incisional hernia being diagnosed compared to the use of physical examination alone. Bloemen et al. (19) also concluded that an ultrasonographic examination added to the physical examination yields a significant number of, mostly asymptomatic, hernias, which would not be found using physical examination alone.
Follow up. As in open surgery, one of the main problems when considering laparoscopic incisional hernia diagnosis is a proper period of follow-up. There is no certainty about which would be the optimal follow-up time to detect TSIH and most studies describe follow-up for less than one year. In addition, the frequent absence of symptoms would result in a lack of medical consulting. According to the definition of Tonouchi (17), it seems reasonable to advise a minimum follow-up of 2 years, although some authors recommend more than 4 years(12, 13). The mean follow up in our series almost achieves 3 years (34 months) which would be quite reasonable.
The study has some limitations. There may be a selection bias, as the acceptance could be related to the presence of symptoms. Furthermore, cancer patients having exhaustive oncological controls may have refused to participate so as not to increase the number of outpatient consultations. Finally, findings may be limited by the relatively small sample size.