Transrectal biplane ultrasound-guided transperineal biopsy for rectal and peri-rectal lesions: an 18-year retrospective analysis.

During the clinical diagnostic and therapeutic processes, confirmed diagnosis of rectal cancer is a critical step ( 1 - 3 ). When patients present with symptoms and/or when diagnostic imaging reveals a rectal mass, enteroscopy is typically performed to directly visualize the intestinal lumen. If a lesion is detected, tissue must be obtained through the biopsy channel for histopathological examination, a process known as endoscopic forceps biopsy (EFB) ( 4 , 5 ). EFB is widely accepted by the clinical community for its simple use, speed, and minimal patient discomfort, making it the most commonly used method for sampling rectal lesions ( 6 - 10 ). However, because EFB samples only superficial mucosa, some malignant tumors yield pathology reports showing merely intraepithelial neoplasia, which can delay definitive diagnosis and treatment planning ( 11 , 12 ). Moreover, some mesenteric-origin tumors may present as inflammatory changes, and other submucosal lesions may appear normal under endoscopy, further complicating diagnosis. To overcome EFB’s superficial sampling limitation, techniques such as endoscopic ultrasound-guided biopsy and transrectal ultrasound-guided core needle biopsy (CNB) have been developed. However, endoscopic ultrasound-guided biopsies, which often utilize cytological fine-needle aspiration (FNA), still carries a relatively high false-negative rate. Reported complication rates for these approaches include post-procedural bleeding in 1.3–4% of cases ( 13 - 15 ), and fever in approximately 2% ( 16 - 18 ) of cases. For transrectal biopsy specifically, bleeding occurs in 2–4% and infection in 1–4% of patients ( 19 ). Despite these low incidence rates, it is particularly important to further reduce the probabilities of bleeding and infection. In addition, perirectal lesions also merit special attention. During follow-up, patients with various malignant tumors are prone to develop metastases in the Douglas cavity ( 20 ), the lowest point of the pelvis. These lesions can be challenging to characterize as benign or malignant, and biopsy options for this location are limited. The commonly employed transrectal puncture method carries risks such as enterocutaneous fistula, infection, and bleeding. Moreover, because most samples obtained from the aforementioned procedures are cytological rather than histological, definitive diagnosis can be delayed. Inspired by the established technique of rectal ultrasound-guided transperineal prostate biopsy, our center has been conducting transrectal biplane ultrasound-guided transperineal biopsy (TRUSTPB) for patients with rectal and perirectal lesions since 2004. This study presents 18 years of experience with this method and the major finding is that TRUSTPB can be considered as a better alternative procedure because of its higher accuracy, lower complication rate compared to standard procedure. To our knowledge, this is the first report describing the use of TRUSTPB for perirectal lesion biopsy. We present this article in accordance with the STARD reporting checklist (available at https://qims.amegroups.com/article/view/10.21037/qims-2025-1691/rc ).

This retrospective study was approved by the Institutional Review Board of Zhejiang Cancer Hospital (Approval No. IRB-2024-1315). The requirement for informed consent was waived due to the retrospective nature of the study and the use of anonymized clinical data. This study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. This retrospective study included a total of 99 patients who were admitted to Zhejiang Cancer Hospital between 2006 and 2020, comprising 50 with rectal lesions and 49 with peri-rectal lesions, all of whom met the specified inclusion criteria listed below. A detailed algorithm for patient screening is shown in Figure 1 . Flow chart for study inclusion and exclusion of patients. TRUSTPB, transrectal biplane ultrasound-guided transperineal biopsy. Inclusion criteria for rectal lesions: patients were eligible if they met at least one of the following conditions (II, III, IV, V). Rectal lesions detected by colonoscopy or relevant imaging. Failure to obtain pathological results via colonoscopy. The pathological result of colonoscopy biopsy is not clear. Colonoscopy was performed without biopsy, and repeat colonoscopy was declined by the hospital. Enteroscopy suggests inflammatory changes, but a false-negative result was suspected and required confirmation. Clinical indication for puncture biopsy based on physician judgment. Availability of definitive pathological or follow-up results. Inclusion criteria for peri-rectal lesions: patients were eligible if they met any of the following conditions Imaging examination suggests the presence of peri-rectal lesions. Imaging examination unable to clearly identify the origin or nature of the lesions. Availability of definitive pathological or follow-up results. Exclusion criteria: The patient refuses to undergo TRUSTPB. Severe cardiovascular or cerebrovascular disease, or significant coagulopathy, posing a high risk for puncture. History of low rectal surgery impeding probe. Incomplete or missing ultrasound puncture data. Criteria for final diagnosis confirmation: Malignancy confirmed by enteroscopic biopsy or puncture pathology. Surgical pathology after resection clearly indicates benign or malignant status. Puncture pathology negative for malignancy, but clinical findings strongly suggestive of malignancy and responsive to chemotherapy, leading to a malignant diagnosis. Benign diagnosis was determined by puncture pathology when puncture pathology was negative for malignancy and the patient remained stable during a five-year follow-up or responded to anti-inflammatory treatment. Gastrointestinal mesenchymal tumors were classified as malignant in diagnostic efficacy analysis. Biopsy is successful if effective tissue or cellular material are obtained for pathological evaluation. Failure was defined as the absence of effective cells or tissues, with specimens consisting solely of blood or mucus. To enable a meaningful comparison of diagnostic efficacy between EFB and TRUSTPB, we explicitly differentiated technical success from diagnostic accuracy. Biopsies yielding sufficient tissue for a definitive pathological interpretation—including high- or low-grade intraepithelial neoplasia, villous adenomas with moderate-to-severe dysplasia, gastrointestinal stromal tumors (GISTs), or other lesions exhibiting moderate-to-severe dysplasia—were classified as diagnosable (i.e., technically successful and clinically interpretable). In contrast, biopsies with insufficient tissue, non-representative sampling, or procedural failure were deemed non-diagnosable. Diagnostic accuracy was defined as the proportion of patients in whom TRUSTPB provided a correct or clinically actionable diagnosis among all evaluable cases (n=99). A biopsy was considered diagnostically accurate if it satisfied any of the following criteria: the initial pathological diagnosis concurred with the final clinical reference standard [e.g., invasive carcinoma, high-grade intraepithelial neoplasia (HGIN), GIST, or villous adenoma with significant dysplasia]; the initial report was benign or non-neoplastic, and subsequent surgical pathology or long-term clinical follow-up (≥5 years) confirmed the lesion to be benign; histological features suggestive of GIST were later confirmed by immunohistochemistry (e.g., CD117 or DOG1 positivity) or characteristic clinical course. To reflect distinct clinical decision making threshold, we conducted two parallel sensitivity analyses: (I) sensitivity for malignancy: malignancy was strictly defined as histologically confirmed invasive carcinoma. Sensitivity was calculated as the proportion of patients with invasive carcinoma (confirmed by reference standard) who were correctly identified by TRUSTPB as malignant. (II) Sensitivity for clinically significant lesions: this category encompassed all lesions warranting therapeutic intervention per current guidelines—including invasive carcinoma, HGIN, GISTs, and villous adenomas with moderate-to-severe dysplasia. Sensitivity was defined as the proportion of patients with any of these conditions (confirmed by reference standard) who were correctly identified by TRUSTPB as having a clinically significant lesion. Monitoring of complications: bleeding and vital signs were monitored intraoperatively, and complete blood counts and body temperature were assessed postoperatively. Method of procedure: TRUSTPB was performed at initial diagnosis in all patients, prior to any anti-tumor therapy. The reference standard was established either by surgical resection or by clinical and radiological follow-up for a minimum of 12 months. The median time interval between TRUSTPB and the reference standard was 16 days [interquartile range (IQR), 10–25 days]. No clinical interventions that could alter the disease status—such as chemotherapy, radiotherapy, immunotherapy, or antibiotics for suspected infection—were administered between the index test and the reference standard. Following clinical evaluation, patients underwent rectal ultrasound-guided transperineal biopsy of rectal or perirectal masses in the ultrasound interventional theatre. Patient identity and medical history were verified, with special attention given to any history of rectal surgery that could affect probe insertion or positioning. The patient was first examined in the left lateral, hip flexor, or stone position. Then the patient was positioned in the lithotomy position, with the buttocks elevated. The perianal region was disinfected in a centrifugal manner—starting from the surrounding skin and progressing inward, with the anus disinfected last. This process was repeated three times before sterile draping was applied. All procedures were performed by ultrasound interventionalists with more than three years of experience in rectal ultrasound-guided transperineal prostate biopsy. The ultrasound instrument used was either MYLAB 90 or MYLAB Twice from Esaote with a biplane probe model TRT33 (ESAOTE, Genoa, Italy). The probe was slowly inserted into the patient’s anus until the rectal or perirectal lesion was fully visualizable. A routine ultrasound examination of the lesion was then performed using convex and linear array probes to assess lesion size, location, length, width, thickness and morphology. For rectal wall lesions, the distance from the anal verge was also measured. Based on lesion size and morphology, the operator selected between FNA or CNB. In general, a 21G Chiba needle was used for lesions smaller than 2 cm or predominantly cystic lesions. Larger or solid lesions were sampled using core biopsy needles—either Bard fully automated or Demeter semi-automated devices. Given the extended study period (2006–2020), specific manufacturers and model numbers of biopsy devices could not be retrospectively retrieved for all procedures due to institutional record-keeping limitations and rapid technological turnover. Nevertheless, a consistent procedural protocol was maintained throughout the study period. For FNA, 21G Chiba needles were routinely used. For CNB, 18G semi-automated or automated biopsy needles were employed in all cases. The choice between FNA and CNB was at the operator’s discretion based on lesion characteristics and real-time ultrasound findings. Color Doppler imaging was performed to map intralesional and perilesional vessels, ensuring the puncture path avoided critical vessels. Local anesthesia with lidocaine was then administered. Under real-time guidance with the linear array probe, a needle was inserted into the lesion to obtain tissue samples for pathological examination, with 1 to 4 punctures being performed. All TRUSTPB procedures were performed using a freehand technique under real-time transrectal ultrasound guidance, without a needle guide attachment, allowing dynamic adjustment of needle trajectory based on lesion morphology and surrounding anatomy. The detailed procedure of the puncture is shown in Figure 2 and Video 1 . Schematic illustration of TRUSTPB for a rectal wall lesion. (A) Scanning the lesion with the convex array probe. (B) Use a line array probe to scan the lesion and plan a biopsy. (C) Ultrasound-guided transperineal puncture of Rectal lesions using a biopsy needle. TRUSTPB, transrectal biplane ultrasound-guided transperineal biopsy. Real-time demonstration of TRUSTPB for a rectal wall lesion. The video shows the entire procedural workflow, including biplane ultrasound localization of the hypoechoic rectal wall mass, perineal needle insertion under real-time dual-plane guidance, and core tissue sampling with the automated biopsy gun. TRUSTPB, transrectal biplane ultrasound-guided transperineal biopsy. Bleeding and vital signs were monitored intraoperatively. Post-procedure, patients were continuously monitored for bleeding, changes in vital signs, and other complications. Complete blood counts and body temperatures were also assessed. Biopsy was considered successful if effective tissue or cellular material was obtained for pathological evaluation. Failure was defined as the absence of effective cells or tissues, with specimens consisting solely of blood or mucus. We conducted pre-specified subgroup analyses to assess variability in the diagnostic accuracy of TRUSTPB according to: (I) lesion nature (solid vs. cystic/necrotic), and (II) needle type (18G core biopsy vs. 21G FNA). These factors were selected based on clinical experience and prior studies suggesting their impact on biopsy adequacy. Additionally, we performed exploratory analyses examining the influence of lesion size and operator experience, which were not defined in the original study protocol. All statistical analyses were conducted using SPSS version 26.0 (IBM Corp., Armonk, NY, USA). For quantitative variables that followed a normal distribution, data were described using mean ± standard deviation (SD), while non-normally distributed variables were described using median and IQR. Categorical data were expressed as frequencies and percentages. Inter-group comparisons for normally distributed variables were conducted using independent-samples t -tests. For non-normally distributed variables, the Mann-Whitney U test was applied. Categorical variables were compared using the Chi-squared test. Multivariate analysis was performed using binary logistic regression to identify factors independently associated with the outcomes. A P value of less than 0.05 was considered statistically significant.

A total of 99 eligible cases were retrospectively collected at our center from 2006 to 2020, comprising 70 females and 29 males, with age ranging from 36 to 82 years. Most patients underwent puncture with a core needle. Among these, 50 cases had intestinal wall lesions and 49 with peristomal lesions. The size of each lesion was measured, and detailed records were maintained for the location, shape, and anorectal distance of the intestinal wall lesions. Further details are presented in Table 1 . Data are presented as n (%) or median [range] or mean ± standard deviation. Of the 99 biopsies performed, 95 were successful and 4 were unsuccessful. Among the failed cases, 2 involved intestinal wall lesions, both sampled via FNA. In each case, the biopsy results revealed only blood or mucinous components without viable cells or tissues. In the first case, surgery was performed based on malignant indication from colonoscopic pathology. In the second case, postoperative colonoscopy during surveillance revealed a new anastomotic lesion. Pathology from colonoscopy suggested granulation tissue with some focal glandular hyperplasia and increased secretion. Although the patient initially declined surgery due to concern related to invasiveness and complications, postoperative pathology eventually confirmed a benign lesion. The remaining two unsuccessful biopsies involved perirectal lesions. In one case, the patient with a history of cervical cancer surgery presented with perirectal lesions. Biopsy indicated extensive necrosis, raising the possibility of malignancy. Based on clinical judgment, radiotherapy was administered, leading to a reduction in lesion size. The second patient, who had previously undergone surgery and chemotherapy for rectal cancer, was found to have an ill-defined perirectal mass during follow-up. Biopsy revealed sheets of gelatinous material without identifiable tumor cells. The patient underwent colonoscopy and biopsy, which indicated chronic mucosal inflammation with necrosis and exudate, and mild focal glandular atypia. A multidisciplinary team recommended continued surveillance, and no recurrence was observed during follow-up. In 2019, the patient developed intestinal obstruction and underwent anastomotic resection at our hospital, with pathology confirming benign changes. A total of 50 rectal lesion cases were identified, comprising 7 benign cases, 4 GISTs, and 39 malignant cases. Of the 39 malignant cases, 25 originated in the rectum, 8 in the stomach, 2 in the cervix, 2 in the bladder, and 2 in the prostate. Among the 7 benign cases, there was 1 case of endometriosis, 1 case of lesions that regressed spontaneously upon follow-up, 1 case that shrank after anti-inflammatory treatment, 2 benign cases indicated by postoperative pathology following surgery, and 2 cases with no significant changes observed during a five-year follow-up. Detailed information is presented in Table 2 . Out of the 50 patients, 12 did not undergo colonoscopy at our center, and lacked pathological samples due to inadequate colonoscopic sampling or absence of significant abnormalities on colonoscopy. Pathological results were available for 37 patients: 6 were malignant, 7 were benign (with 6 false negatives), 10 had HGIN, 2 were indeterminate, 1 had low-grade intraepithelial neoplasia, and 1 had a villous adenoma with moderate to severe epithelial dysplasia. The TRUSTPB results identified 32 cases as definitively malignant, while 9 patients had biopsies suggesting benignancy, though 3 of these were false negatives Additionally, FNA in two patients revealed moderate-to-severe dysplastic epithelial cells; one patient had HGIN, and two biopsies were unsuccessful. A case study is presented in Figure 3 . Further details are provided in Table 3 . GIST, gastrointestinal stromal tumors. The patient presented to the hospital 8 months ago with an increased frequency of bowel movements, occurring 6–7 times/day, consisting of loose stools, accompanied by urgency and a feeling of incomplete defecation. During the anus finger test, it was noted that 3 cm from the anus, the right anterior wall of the rectum could be palpated, revealing an elevated type of mass that is hard, approximately 2 cm in size, with poor mobility. During enteroscopy, it was observed that there is a submucosal bulge 2 cm from the dentate line of the rectum, with a smooth, hard mucosal surface. We performed TRUSTPB on him. Pathological findings of the biopsy were: gastrointestinal mesenchymal tumour. (A) Ultrasound line-array scan of rectal lesions, (B) CDFI, (C) biopsy procedure, (D) pathological image (H&E staining, 400×). CDFI, Color Doppler flow imaging; H&E, hematoxylin and eosin; TRUSTPB, transrectal biplane ultrasound-guided transperineal biopsy. EFB, endoscopic forceps biopsy; HGIN, high-grade intraepithelial neoplasia; LGIN, low-grade intraepithelial neoplasia; TRUSTPB, transrectal biplane ultrasound-guided transperineal biopsy. A total of 49 peri-rectal lesions were identified, comprising 7 benign cases, 6 GISTs, and 36 malignant cases. Of the 36 malignant nodules, all but one chordoma and one germ cell tumor were metastatic or recurrent tumors originating from other sites. Detailed information is presented in Table 2 . Of these 49 patients, 26 did not undergo colonoscopy, and 8 had normal colonoscopy results, hence no pathological specimens were obtained. Pathological results showed 9 benign lesions (including 6 false negatives), 1 GIST, 2 cases of HGIN, and 1 indeterminate case. Rectal ultrasound-guided transperineal biopsy identified 36 malignant cases, 6 benign cases, 5 GISTs. In one case, pathology could not definitively exclude a neoplastic lesion; the patient opted for surveillance, and no changes were observed over a five-year follow-up, indicating a benign outcome. Another case was initially diagnosed as a mesenchymal tumor on biopsy, but the surgical result confirmed a prostatic stromal tumor. Two biopsies were unsuccessful. Two diagnosed cases of perirectal lesions are presented in Figures 4,5 . Further details are provided in Table 3 . Colorectal 3 months after surgery, ultrasonography revealed two hypoechoic nodules between the outer wall of the left rectum and the left seminal vesicle gland. ultrasound-guided transrectal pelvic nodule puncture biopsy was performed. Pathological results indicated the metastatic lesion. (A) Ultrasound line-array scan of peri-rectal lesions, (B) CDFI, (C) biopsy procedure, (D) pathological image (H&E staining, 400×). CDFI, Color Doppler flow imaging; H&E, hematoxylin and eosin; TRUSTPB, transrectal biplane ultrasound-guided transperineal biopsy. 5 years after surgery for cervical cancer. A postoperative MRI review suggested a nodal focus on the left pararectal side of the rectum with metastatic potential. To clarify the diagnosis, she presented to our hospital and underwent a TRUSTPB. Pathological results revealed a poorly differentiated squamous carcinoma of the left side of the rectum. (A) Ultrasound line-array scan of peri-rectal lesions, (B) ultrasound convex-array scan of peri-rectal lesions, (C) biopsy procedure, (D) pathological image (H&E staining, 100×). CDFI, Color Doppler flow imaging; H&E, hematoxylin and eosin; MRI, magnetic resonance imaging; TRUSTPB, transrectal biplane ultrasound-guided transperineal biopsy. Given that a pathological diagnosis of malignancy is definitive, no false-positive cases occurred in our cohort. Consequently, false-positive rates and specificity were not applicable and were excluded from the statistical analysis. Our results demonstrate that, for both rectal and peri-rectal lesions, TRUSTPB achieved higher diagnostic accuracy and sensitivity than EFB, while also exhibiting a lower technical failure rate. Detailed comparative data are presented in Table 4 . EFB, endoscopic forceps biopsy; TRUSTPB, transrectal biplane ultrasound-guided transperineal biopsy. Our results revealed that the use of coarse needles and the presence of malignancy were associated with higher biopsy success rates (P<0.05), with a statistically significant relevance. Detailed results are provided in Table 5 . Data are presented as n or mean ± standard deviation. The patient’s postoperative status, including body temperature, bleeding, and blood routine, were closely observed, and no serious complications were found.

Rectal malignancies are among the most common cancers in terms of both incidence and mortality, posing a significant threat to human health ( 21 - 23 ). Although the incidence and mortality rates of rectal cancer have shown a downward trend in some developed countries, the burden of colorectal cancer in China continues to increase ( 22 , 24 ). This trend is expected to worsen with the ongoing Westernization of lifestyle habits. In recent years, increasing health awareness and improved screening practices have led to a higher detection rate of rectal wall lesions. Accurate diagnosis of these lesions is crucial for guiding optimal treatment strategies and improving patient outcomes ( 25 - 27 ). Colonoscopy remains the most widely used diagnostic tool in clinical practice, which has a unique advantage in detecting mucosal lesions ( 28 - 30 ). However, rectal lesions show considerable heterogeneity, and EFB often fails to obtain adequate samples from submucosal or extensively necrotic lesions due to its limited sampling depth ( 31 ). In addition to primary rectal wall lesions, many patients with malignant tumors develop metastatic deposits in the Douglas pouch, the most dependent portion of the abdominal cavity ( 32 - 34 ). These lesions are deeply situated and challenging to access via transabdominal biopsy due to the presence of critical organs such as the uterus and bladder ( 35 - 37 ). For the purposes of this study, lesions located near the most dependent portion of the abdomen are referred to as perirectal lesions ( 38 , 39 ). Currently, most reports on ultrasound-guided rectal puncture describe transrectal puncture, which has a complication rate of around 11%. Moreover, this method often yields only cytological samples, limiting the ability to establish a definitive histopathological diagnosis. Although computed tomography (CT)-guided biopsy has been proposed for such cases, its lack of real-time visualization increases the risk of injury to blood vessels, nerves, and other adjacent structures ( 40 ). Moreover, CT guidance is often inadequate for small nodules or those confined to the rectal wall. To this end, we employed a transperineal puncture technique with a dual-plane rectal ultrasound probe. This method does not require a guide frame and offers real-time, precise, and highly accurate results. By avoiding penetration of the rectal wall, this approach substantially reduces the risks of bleeding and infection. Additionally, the entire puncture path can be visualized using the linear-array mode, allowing flexible selection of the needle entry point and facilitating the use of larger-gauge needles to obtain more tissue. As a result, the safety and accuracy of this puncture method are significantly improved. The four unsuccessful biopsies in our cohort—two involving small intestinal wall nodules and two perirectal lesions—highlight the diagnostic challenges inherent in sampling deeply seated or anatomically complex lesions. Notably, all failed cases were approached using FNA, which was selected due to lesion size (<1 cm in three cases) or proximity to critical structures (e.g., rectal wall, anastomotic sites, or post-radiation fibrotic zones), where larger-gauge needles posed unacceptable procedural risks. While FNA offers a safer profile in such scenarios, it is well recognized to carry a higher rate of non-diagnostic or acellular samples compared to CNB, particularly when targeting necrotic, mucinous, or fibrotic tissue—features commonly seen in post-treatment or inflammatory lesions. In our patient cohort, failed specimens consisted predominantly of blood, mucin, or amorphous gelatinous material without viable cellular elements, underscoring the limitations of blind or grayscale ultrasound-guided FNA in low-suspicion or heterogeneous lesions. These cases suggest two actionable strategies to improve diagnostic yield in future practice. First, contrast-enhanced endoscopic ultrasound (CE-EUS)—which was not routinely available during our study period—could help identify viable, vascularized regions within otherwise ambiguous nodules, thereby guiding needle placement toward metabolically active tissue and avoiding necrotic or acellular zones. Second, the implementation of rapid on-site evaluation (ROSE) by a cytopathologist would allow immediate assessment of sample adequacy, enabling real-time repeat sampling if initial passes are non-diagnostic. Both approaches have been shown in other gastrointestinal and pelvic malignancy settings to significantly reduce non-diagnostic rates and enhance procedural efficiency. Importantly, despite initial biopsy failure, none of the four patients harbored occult malignancy at long-term follow-up (median >5 years), reinforcing that clinical vigilance and multidisciplinary management can safely compensate for technical limitations in select cases. Nevertheless, optimizing pre-procedural planning and intra-procedural feedback remains critical to minimizing diagnostic uncertainty—particularly in patients with prior cancer history or complex post-treatment anatomy, where distinguishing recurrence from benign sequelae is clinically paramount. A fundamental limitation of the TRUSTPB technique is its reliance on intact transrectal access for ultrasound probe placement. In our cohort, 21 patients were deemed ineligible for TRUSTPB due to post-surgical anatomical alterations—specifically, anastomotic strictures or dense pelvic fibrosis—following prior low anterior resection for rectal cancer. These changes rendered both transrectal ultrasound probe insertion and endoscopic evaluation technically unfeasible in most cases. For this subgroup, alternative image-guided biopsy strategies were pursued: CT-guided percutaneous biopsy or conventional transperineal ultrasound-guided biopsy (without transrectal probe assistance) served as viable options. Notably, in female patients, real-time guidance using a transvaginal biplane ultrasound probe enabled a transperineal approach to peri-rectal lesions, effectively circumventing the need for transrectal access. Final clinical decisions were informed by findings from these alternative biopsies, complemented by multimodal imaging [e.g., pelvic magnetic resonance imaging (MRI), CT, or positron emission tomography-computed tomography (PET-CT)], tumor biomarkers, and longitudinal follow-up. This experience underscores a critical boundary of TRUSTPB: it is not applicable in patients with severely disrupted rectal anatomy. Future studies should aim to systematically evaluate and standardize these complementary image-guided techniques to ensure equitable diagnostic access for all patients, irrespective of their surgical history. Biopsy needle selection was determined according to the lesion’s size and morphological characteristics. For small lesions, fine needle aspiration (FNA) was preferred because the shortest cutting range of an automatic biopsy needle is 20 mm. Although semi-automatic needles offer adjustable cutting lengths down to 10 mm, such short settings markedly reduce firing force, increasing the risk of sampling failure. Therefore, for lesions smaller than 20 mm, we primarily used a percutaneous transhepatic cholangiography (PTC) needle. Additionally, for cystic lesions, which often yield insufficient tissue samples, we also used the PTC needle for aspiration. In this study, coarse needle biopsy outperformed fine needle biopsy in providing accurate histopathological diagnoses. However, the relatively small number of benign cases and the fact that many patients with prior surgical history may limit the generalizability of these findings and obscure the differences between the two methods. Given that coarse needles provided more diagnostic information, their use is still recommended for most biopsy procedures. In this study, TRUSTPB achieved an accuracy of 91.92%, demonstrating strong diagnostic and predictive value. Accuracy was consistent across different puncture sites and was similar for both coarse and fine needle biopsies. However, the positive detection rate for fine needle biopsies was significantly lower than that for coarse needle biopsies. Similarly, smaller lesions exhibited a markedly lower positive detection rate compared with larger lesions. Specifically, nodules larger than 25 mm were almost always positive, except for predominantly cystic lesions. False-negative cases with TRUSTPB were mainly attributed to the transitional nature of 2–5 cm rectal lesions. Such lesions often extend into reactive surrounding tissue, which can lead to false-negative results ( Figure 6 ). Despite these occasional false negatives, the diagnostic accuracy of TRUSTPB remains high compared to other studies. This study performed a comparative analysis between TRUSTPB and EFB for rectal and perirectal lesions. EFB, as a routine diagnostic method, continues to play an irreplaceable role in diagnosis of rectal lesions. However, in a significant portion of malignant cases in this cohort, EFB results showed findings limited to intraepithelial neoplasia. This highlights the superficial nature of EFB sampling, which, while sufficient for early-stage patients eligible for surgery based on imaging, yet insufficient to guide chemotherapy decisions in mid- to late-stage disease. Our findings are consistent with recent evidence showing superior diagnostic yield of transperineal core-needle biopsy over EFB in complex rectal lesions ( 41 ). Therefore, TRUSTPB can serve as a valuable adjunct to EFB in clinical decision-making. A 46-year-old male presented with hematochezia and mucoid diarrhea for two months. Pelvic contrast-enhanced MRI revealed a 7.2-cm irregular rectal wall thickening extending to the mesorectal fat, with suspicious perirectal lymphadenopathy. Initial endoscopic forceps biopsies yielded inconsistent results—ranging from low-grade dysplasia to HGIN—despite three repeated attempts. Given the high clinical and radiological suspicion for locally advanced rectal cancer, TRUSTPB was performed, which demonstrated severely dysplastic glands within fibromuscular tissue, with a pathological comment of “carcinoma cannot be excluded”. After multidisciplinary discussion and informed consent, the patient proceeded directly to neoadjuvant chemoradiotherapy without further biopsy. Final postoperative pathology confirmed moderately differentiated adenocarcinoma with extramural invasion and treatment-related regression, while all sampled lymph nodes showed only chronic inflammation. (A) CDFI demonstrates abundant intratumoral vascularity within the rectal wall lesion. (B) Spectral Doppler analysis confirms arterial blood flow within the nodule, characterized by a high-resistance waveform. (C) Real-time transperineal core needle biopsy of the lesion under transrectal ultrasound guidance. CDFI, Color Doppler flow imaging; HGIN, high-grade intraepithelial neoplasia; MRI, magnetic resonance imaging; TRUSTPB, transrectal biplane ultrasound-guided transperineal biopsy.

Based on 18 years of single-center experience, this study is the first to report the application of TRUSTPB for rectal wall and perirectal lesions. This technique offers real-time, efficient, highly accurate biopsy approach, and a low complication rate, making it a safe and practical biopsy approach suitable for broad clinical adoption.

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