Anatomical Anal Stenosis after PPH: Insights from a Retrospective Study and Rat Model.

High-grade hemorrhoids are usually recommended to receive operational treatments. However, these traditional surgeries are associated with severe postoperative pain. A procedure for prolapse and hemorrhoids (PPH), a circular staple device, has been developed to improve short-term outcomes, including reducing the severity of postoperative pain. PPH, compared to conventional surgery, has been associated with the incidence of anatomical anal stenosis. The causes of stenosis after PPH are not yet clear. We first analyzed the complications of our patients with PPH, and then developed a rat model to verify the tension force of PPH using Hematoxylin-eosin, Masson's trichrome, immunohistochemistry, and immunofluorescence staining. Our clinical data showed that PPH significantly improved postoperative pain, but that it resulted in higher incidences of complications, including anal stenosis, than hemorrhoidectomy. We simulated the status of PPH and developed a rat model to verify PPH's tension force, including the scarring area and the deposition of proinflammatory factors, angiogenic factors, and fibrotic factors. The tension wound histological data showed more extensive granulation tissue and inflammatory cell infiltration and a thicker epidermis than the control group on day 12 post-operation and tension treatment. In addition to IL-1β and IL-10 cytokines on day 3 and IL-1β, IL-6, and IL-10 cytokines on day 12 post-operation in the tension group, two angiogenic factors, CD31 and VEGF-A, were found to have a more significant expression on day 7 post-operation in the tension group. The mean scar area was larger and the distribution of fibrotic proteins (collagen 1, α-SMA, CTGF, and MMP2) in the tension group was significantly broader than in the control on day 12 post-operation and tension treatment. Based on the findings of our animal model, the development of a lesser tensile force for PPH to decrease the deposition of proinflammatory factors, angiogenic factors, and fibrotic factors is urgently required.