Role of Endoscopic Ultrasound in Diagnosis of Rectal and Perirectal Lesions

INTRODUCTION

Because of its capability to discriminate multiple layers of the gastrointestinal (GI) wall, endoscopic ultrasound (EUS) has become a valuable tool for evaluating GI tract lesions and lesions near the GI tract. Although EUS is well-known for assessing pancreatic and upper GI tract lesions, its value as a diagnostic and staging tool for other parts of the GI tract, notably the recto-sigmoid colon, is becoming more frequently recognized [1, 2].

Even though EUS can correctly stage GI malignancies, it cannot reliably distinguish benign from malignant lesions on its own. As a result, pathologic testing is usually necessary to establish a definitive diagnosis for clinical intervention [3]. The ability to collect cytological material under direct vision has expanded the diagnostic performance of this procedure, allowing for a more precise diagnosis [4, 5].

Endoscopic ultrasound-guided fine needle aspiration (EUS-FNA) diagnostic accuracy for esophageal, gastric and duodenal subepithelial tumors has been reported to be 82–94% [6, 7] and 80–95% for pancreaticobiliary lesions [8, 9].

Few studies have looked at how useful EUS is as a diagnostic tool for ‎rectal and perirectal pathologies. The relevance of EUS-FNA in assessing ‎submucosal and extrinsic masses of the colon and rectum has been highlighted in ‎several trials [10-13].‎Aim:‎

Our study looked at role of EUS to assess nature of polyps and submucosal ‎lesions and differentiate benign and malignant lesions in the rectal and perirectal ‎areas. ‎

PATIENTS AND METHODS

This cross-sectional prospective study included 70 adult patients (44 males and 26 females) with mean age of 51.91 ± 9.90 years and ranges from of 26 to 69 years. All patients had rectal and/or perirectal lesions detected either by abdominopelvic CT or MRI and/or colonoscopy. All the 70 patients underwent rectal EUS. Out of the 70 patients, EUS-FNA was performed for 26 patients if the wall thickness was sufficient for aspiration (> 7 mm). The patients selected from those attending the Internal Medicine Department during the period from June 2017 to May 2019.

In this study, inclusion criteria according to the findings detected were:

• Patients with a thickened rectal wall
• Patients with space occupying mass in the rectum or perirectal area
• Patients with rectal polyps
• Patients with rectal submucosal lesions

Exclusion criteria were:

• Patients with lesions more distant than 20 cm from the anal verge
• Patients with advanced co-morbidities (Chest, Heart diseases …. etc.) interfering with performing endoscopy or giving Propofol injection.
• Patients with bleeding tendency contraindicated EUS-FNA.
• Patients missed for following up or patients whose histological examination was not available, so the final diagnosis was not settled.

For all the patients included, the following assessment schedule applied:

• Detailed history taking with special stress on symptoms of bleeding per rectum, change in bowel habits, rectal pain, weight loss, anemic manifestations; history of similar conditions, previous operations or cancer; family history of similar conditions or cancer.
• Thorough clinical examination with special attention to abdominal examination (including per rectal examination) and lymph nodes examination.
• Abdominal ultrasound examination
• Thorough examination of recent abdominopelvic CT or MRI, as well as a colonoscopy for rectal or perirectal abnormalities, was performed prior to the EUS procedure. Patients were fasting for at least 8 hours before examination. Preparation done by polyethylene glycol and repeated enemas. Coagulation profile of the patients was assessed. Sedation with Propofol indicated in irritable patients. Patients received single IV antibiotic injection of third generation cephalosporins before EUS-FNA.

Procedure:

The patients were in a left lateral decubitus position. An EUS linear array machine (Pentax EG-3830UT Echoendoscope) attached to a compatible ultrasound machine (Hitachi EUB 7000 or Avius)were used. One expert endosonographer performed all EUS examinations. FNA was obtained under EUS guidance using fine needles (Cook Echotip needle) 22 or 19G.

Elastography was done to assess the hardness of the lesions. To avoid puncturing intervening blood vessels, Doppler was utilized to assess the needle's predicted route.

During EUS, all lesions were examined thoroughly including all layers of the rectal wall underneath the lesions. The presence of perirectal lymph nodes, depth of wall invasion and invasion into the perirectal fat or adjacent organs (such as the bladder, prostate, seminal vesicles, vagina or anal sphincters) were evaluated (figure 1).

If it was feasible and the wall thickness was sufficient for aspiration, the FNA needle was progressed through the linear array echoendoscope's instrument channel, the gut wall punctured, the needle entered the lesion and reciprocated back and forth with a negative suction applied via a syringe of 10 mL once the internal stylet was removed. The needle was retracted then into the sheath before being removed from the scope.

Note: Data expressed in the form of frequency (percentage) or mean (standard deviation) as appropriate.

N, number; SD, standard deviation.

DISCUSSION

Although EUS may be used to outline the GI wall, there has been few research on the use of EUS to diagnose rectal and perirectal pathologies. As a result, rectal EUS continues to be underused, maybe due to a lack of knowledge and awareness of the procedure's worth.

Our study aimed to confirm the utility of EUS in the diagnosis of rectal and perirectal lesions. Rectal EUS and EUS-FNA, according to our findings, are excellent diagnostic techniques that play an important role in patient care. When a malignant diagnosis is made in a clinically worrisome lesion, treatment can begin right once. Unwarranted surgery can be avoided by confirming a benign diagnosis on lesions with low clinical suspicions.

Our study showed that both rectal EUS and EUS-FNA had a perfect diagnostic accuracy, sensitivity and specificity, whereas colonoscopy alone had a lower diagnostic accuracy of 88.50%, sensitivity of 88% and specificity of 89% because it missed some benign and malignant pararectal lesions. The diagnostic accuracy was improved to 93%, the sensitivity to 97%, and the specificity to 89% by adding an imaging modality to colonoscopy making a presumptive diagnosis.

Previous EUS studies for the lower GI tract have similarly shown great diagnostic precision. Boo et al. [13] found EUS to be effective in rectal or perirectal lesions, with good diagnostic accuracy (91.70%). Amin et al. [15] found that EUS had a sensitivity and specificity of 91% and 100% for detecting malignant rectal/perirectal lesions, respectively. Maleki et al. [16] evaluated the use of rectal EUS to assess perirectal lesions and found that it had 87% sensitivity, 100% specificity, 90% diagnostic accuracy, 100% positive predictive value (PPV), and 77% negative predictive value (NPV). According to Puli et al. [17] meta-analysis and systematic review, the pooled sensitivity of EUS in diagnosing T0 was 97.30%, the pooled specificity was 96.30%, the positive likelihood ratio was 21.90 while the negative likelihood ratio was 0.08.

Some previous trials have contradicted our findings. According to Soh et al. [18], EUS had a low diagnostic accuracy of 50% for subepithelial tumors (5/10), 75% for non-subepithelial tumors (15/20), and an overall diagnostic accuracy of 67% (20/30) for rectal and perirectal lesion. And according to Serra-Aracil et al. [19], the overall accuracy of EUS was 78%, with 83.78% sensitivity, 20% specificity, 91.30% PPV, and 11% NPV. Forty patients (8.08%) were under staged, whereas 50 (10.90%) were over staged.

The capacity to assess tissue elasticity makes elastography an extension of clinical sense, reinforcing and validating the diagnosis. There are, however, few research on the use of EUS elastography to distinguish benign from malignant rectal tumors. Our study showed that there was a relationship between EUS elastography and the final diagnosis of the lesions. Soft pattern (grades 1 and 2) corresponded to most of the benign cases (67.60%) and firm pattern (grades 3 and 4) corresponded to most of the malignant cases (78.70%).

Additional advantage of EUS is that it is quite safe, with a minimal risk of serious complications. In all the cases in which we studied it; the technique had no adverse effects.

Our work had some limitations; (1) Relatively small sample size (2) There were no on-site cytopathologists for all cases. (3) There was a problem in fixing specific imaging modality (e.g., MRI). (4) Restricted ability of rectal EUS examination to evaluate for the lymph nodes in the region of the left iliac vessels.

Various advanced technologies to enhance ultrasound imaging and therapeutic indications may contribute to the expanded utility of rectal EUS. Future multicenter studies with large sample sizes on the relevance of EUS and elastography in the evaluation of rectal and perirectal lesions are needed. Comparative studies between EUS and imaging techniques, particularly MRI, might be prepared in the diagnosis of rectal and perirectal lesions.

CONCLUSION

EUS is a useful diagnostic technique evaluating rectal and perirectal lesions; it confirms or rules out malignancy in lesions when clinical suspicion exists. On the condition that the endosonographer has a lot of expertise with endosonography, EUS alone without FNA may be enough to diagnose rectal and perirectal abnormalities. The use of EUS elastography in the identification and distinction of benign and malignant rectal and pararectal lesions could be valuable.

Source(s) of support: none

Presentation at a meeting: no

Conflicting Interest: no

Ethical Considerations:

The study performed after being approved from the Institutional Review Board (IRB) of Faculty of Medicine with an IRB number of 17200593. The study was conducted in accordance with the provision of Declaration of Helsinki. Privacy of the participants as well as confidentiality of the data assured. Patients informed about the possible side effects and complications that may happen within the procedure. Informed consents, telephone numbers, and addresses were taken from the patients.