The current study includes patients undergoing HP for rectal cancer in the county of Skåne with a one-year follow-up. The incidence of pelvic sepsis was 11%, with 40% of the patients diagnosed more than 30 days after surgery. Neoadjuvant RT and BMI over 25 kg/m2 were risk factors for pelvic sepsis in the multivariable analysis, whereas older patients were at a slightly lower risk of developing pelvic sepsis. Most pelvic sepsis patients were treated conservatively and no patient required major surgery. Pelvic sepsis was not more frequent after low HP.
Recent studies have reported a pelvic sepsis rate of 6-8% within 30 days (10, 14, 16). Our study includes the diagnosis of pelvic sepsis up to one year postoperatively with 40% diagnosed later than 30 days postoperatively, and is thus in accordance with these studies. Several small retrospective studies with a longer follow-up time have been inconsistent and report a rate of pelvic sepsis from 10–33% (4, 5, 12, 13). Tottrup et al. (12) concluded a one year incidence of pelvic sepsis of 18.6% and 33% if the resection level was low i.e. on the pelvic floor, attributed to poor healing properties of the lower rectum causing dehiscence of the short anorectal stump. However, apart from rectal cancer, the study included patients with diverticulitis as well as other diagnoses which may have influenced the results (12). Molina et al. compared low HP with APR for distal rectal cancer and found a pelvic sepsis rate of 12.2% after low HP, advocating that APR should be considered in distal rectal cancer when anastomosis is unsuitable (13). Since APR is associated with impaired wound healing in the perineum (16, 17) intersphincteric APR has been proposed as an alternative to HP. A randomised study, the HAPIrect, has been initiated in Sweden to compare low HP with intersphincteric APR (18).
The present study showed that neoadjuvant RT increased the risk of pelvic sepsis after HP, in line with previous studies (14, 19-21) indicating that neoadjuvant RT causes defective wound healing and subsequently increases the risk of pelvic sepsis. Although neoadjuvant RT was a risk factor for pelvic sepsis development in a large study from the Dutch surgical audit it did not affect the overall reinvention rate or mortality (14). Since neoadjuvant RT has been shown to decrease local recurrence, the use of neoadjuvant RT is steadily increasing with around 60% of patients in Sweden receiving RT and over 90% of patients in the Netherlands receiving RT, which may affect postoperative morbidity (22).
Interestingly the ASA grade was lower in the pelvic sepsis group and the pelvic sepsis group was significantly younger. This could be explained by significantly higher RT rate in patients younger than 75 years of age. The increased operation time and blood loss in the pelvic sepsis patients may suggest that technical difficulties occurred intraoperatively. Lastly the rate of overall complications and reoperations were higher in the pelvic sepsis group suggesting that neoadjuvant RT may be a confounding factor, causing difficulties intraoperatively as well as impaired wound healing. This can explain why older patients had a slightly lower risk of developing pelvic sepsis. A contributing factor could be unintended HP in younger patients due to intraoperative problems. As there was no difference in terms of TNM stage, with approximately 50% of patients classified as TNM stage I-II in patients with and without pelvic sepsis, a more advanced tumour stage probably did not affect the results.
Obesity has been shown to increase the risk of postoperative complications such as surgical site infections and respiratory complications (23). Furthermore, surgeons are less likely to attempt minimally invasive surgery in obese patients and there is a higher risk of conversion in some studies (24). The present study identified BMI higher than 25 kg/m2 as a risk factor for pelvic sepsis. This is in line with a recent study by Jonker et al. (14), which showed that BMI over 30 kg/m2 increased the risk for pelvic sepsis.
When evaluating the consequences of pelvic sepsis, the present study showed that most patients with pelvic sepsis were successfully treated conservatively, none required major surgery and no patient that developed pelvic sepsis died within 90 days. The 30- and 90-day mortality was consistent with other studies on patients undergoing HP (10, 20). However, when comparing HP mortality with overall mortality after rectal cancer surgery, the numbers are high, possibly reflecting a selected group of patients undergoing HP (25). Not many studies report morbidity after HP; the most common complaint in our study was chronic secretion from the anorectal remnant seen in 32 patients (13%). Similar findings are reported by Popiolek et al.(26).
This study was not without limitations; its partially retrospective nature and the relatively small patient cohort should be considered when interpreting the results. Since data on rectal stump length as well as data on partial vs. total mesorectal excision was not recorded in the SCRCR during the study period, low HP was presumed when tumour height was registered <10 cm and used as a surrogate to predict the level of transection. The strengths of the study were a meticulous review of medical charts and a long follow-up time resulting in a complete data set.
There is an ongoing discussion about the best treatment for distal rectal cancer (16, 27). A better understanding of the incidence of pelvic sepsis and risk factors is desired when constructing treatment recommendations regarding the use of HP in rectal cancer patients. Larger patient cohorts would allow potential risk factors such as smoking or diabetes to be explored, as well as preoperative nutritional status. Other HP aspects such as how many patients undergo unintentional HP as a result of intraoperative adverse events, overall postoperative HP complications and oncological results are issues that warrant addressing.