Perianal abscess is a widespread disease, and the incidence rate is as high as 10% -20% in some high-risk groups such as anal foreign body, anal fissure, rectal fistula, and other patients. 14 In addition, people who are sedentary or have limited movement, such as office workers and long-term bedridden patients, are also more likely to develop perianal abscesses.15 Early, small perianal abscesses can be relieved and cured by non-operative programs (such as drug treatment, hot compress, etc.). If recurrence occurs after non-operative treatment, or the abscess persists, or the abscess spreads to surrounding tissue causing perianal infection or affecting sphincter function, or there are other complications such as anal fistula, surgery should be performed immediately.16 Surgery can effectively drain and remove infection, thus quickly eliminating inflammation and abscesses and reducing symptoms such as pain and discomfort.17 The time from the early stage of perianal abscess to the need for surgical treatment varies from person to person, with a minimum of one day and up to several weeks. This process depends on the severity of the disease, the effect of non-surgical treatment options, and the recovery ability of the individual.18 Once the patient has surgical indications, a timely and appropriate surgical strategy is essential for the success of the operation and postoperative recovery. The relevant diagnostic information obtained by rapid and accurate preoperative imaging examination can help clinicians formulate the best operation strategy to reduce operation time, improve treatment effects, and reduce disease recurrence.
At present, perianal ultrasound is the most commonly used preoperative imaging tool for perianal abscesses. In this study, the accuracy of pelvic CT in diagnosing the type of perianal abscess, the location of the perianal abscess, and the internal opening of the perianal abscess were 100%, 93.94%, and 81.82%, respectively. Studies have shown that the accuracy of perianal ultrasound in diagnosing the type of perianal abscess is 50-83.8%, the accuracy of diagnosing the location of perianal abscess is 75-85%, and the accuracy of diagnosing the internal opening of perianal abscess is 73%. 19 Singh et al. found that the accuracy of MRI in diagnosing the type of perianal abscess was 95-100%, the accuracy of diagnosing the location of the perianal abscess was more than 90%, and the accuracy of diagnosing the internal opening of the perianal abscess was 96%. 20 Through indirect comparison, we found that the accuracy of pelvic CT in diagnosing the type of perianal abscess was significantly better than that of perianal ultrasound and slightly better than MRI, the accuracy of diagnosing the location of the perianal abscess was higher than that of perianal ultrasound and MRI, and the accuracy of diagnosing the internal opening of the perianal abscess was significantly better than that of perianal ultrasound but lower than that of MRI. The internal opening of a perianal abscess usually refers to the channel or opening inside the abscess that communicates with the anal canal. The internal opening is usually located in the local part of the perianal abscess and is part of the soft tissue. 21 Some studies have shown that because the soft tissue resolution of pelvic CT is lower than that of MRI, the accuracy of diagnosing the internal opening of perianal abscess is lower than that of MRI.22 In this study, the accuracy of pelvic CT has no obvious disadvantage compared with MRI, which may be related to the higher reading level of clinicians in our hospital. In China's public third-tier hospitals in second-third-tier cities, pelvic CT takes 5-10 minutes and costs RMB 100-200. 23 Perianal ultrasound takes 10-15 minutes and costs about RMB 100; MRI tests are longer and more expensive than perianal ultrasound and pelvic CT.(ranging from 30 minutes to 1 hour, with an average cost of 1,000 yuan)24 Through indirect comparison, we found that the time and cost of pelvic CT in diagnosing perianal abscess was similar to that of perianal ultrasound. However, it was significantly better than MRI, suggesting that a pelvic CT scan has a better economic and time advantage in the preoperative diagnosis of perianal abscess. This is mainly due to the use of magnetic resonance imaging in MRI, signal acquisition is slow, scanning time is longer, and MRI examination requires patients to cooperate with more preparation, such as patients can not wear metal products during the examination.In addition, there are more taboos on MRI examination: for example, some claustrophobic patients cannot cooperate reasonably with the examination; obese patients do not quickly enter the scan chamber, and even if they do, the image may not be apparent due to physical contact with the coil; patients with pacemakers or magnetic medical devices in their bodies are restricted; critically ill patients who cannot cooperate reasonably or patients with monitoring systems and life support systems cannot enter the magnet room. However, ultrasonic imaging has low spatial resolution and limited accuracy in three-dimensional reconstruction, and ultrasonic images can not be continuously collected (ultrasound technicians can only collect a small number of pictures, according to experience). Therefore, it is difficult for clinicians to make accurate ultrasound reports by analyzing images and evaluating ultrasound features quickly. At the same time, a perianal ultrasound examination will inevitably squeeze the abscess site of the patient, which is easy to aggravate the pain and discomfort of the patient. If the abscess is deep, the abscess needs to be squeezed by the ultrasonic probe to a deeper level, and the pain is more prominent. Pelvic CT can carry out accurate three-dimensional reconstruction, doctors can consult continuous images at any time, and clinicians can quickly learn to read and distinguish pelvic CT images through short-term training, which is helpful for anorectal surgeons to determine the location and internal orifice of perianal abscess according to specialist experience and to judge the depth of perianal abscess. In addition, pelvic CT uses X-ray to image the different transmittance of different human body tissues, and there is no physical contact with the abscess site of the patient. Therefore, compared with ultrasound, it has the advantage of being painless or will not aggravate the pain.25 In summary, pelvic CT is expected to be used as a first-line imaging tool for preoperative diagnosis of perianal abscess to help anorectal surgeons choose the correct surgical path.
This study also has some limitations: first, the sample size is small, mainly because the imaging technicians in our hospital work in shifts and the personnel are relatively unstable, which leads to the inconsistent scanning range of different patients and is excluded, which significantly affects the sample size included. Therefore, the imaging technician should be fixed as far as possible in the relevant clinical trials. Second, there needs to be a more direct comparison between pelvic CT, MRI, and perianal ultrasound, which needs to be realized by further clinical control studies. Third, the quality of the pelvic CT diagnosis report depends on the reading level of anorectal surgeons and radiologists.
To sum up, pelvic CT has high accuracy in diagnosing the type, location, and internal opening of the perianal abscess. It is a safe, accurate, economical, and effective tool for preoperative imaging diagnosis of perianal abscess. It is suggested that anorectal surgeons should choose pelvic CT as a tool for preoperative imaging diagnosis of perianal abscess.We look forward to more large-sample, multicenter, high-quality clinical studies to confirm this conclusion and prepare for its entry into the guidelines for diagnosing and treating perianal abscesses.
Supported by Sichuan Science and Technology Program (2022YFS0625).
JL, JQW and XDY, came up with the study's concept. JL and XDY read pelvic CT, and JQW collected data and drew the images. JL and JQW conducted an analysis of the stats. JL, WJQ, XDY,YJW, WZH and LYL all provided their interpretations of the data. JL and JQW produced the initial draft. JL, JQW, XDY, and LYL critically evaluate the manuscript to see whether it contains any noteworthy intellectual content. All authors gave their approval to the final version.
Disclosure forms provided by the authors are available with the full text of this article.
A data sharing statement provided by the authors is available with the full text of this article.
We thank the authors of all other studies that provided data.