Role of Endoscopic Ultrasound in Diagnosis of Rectal and Perirectal Lesions

) with statistically significant difference between EUS diagnosis, EUS-FNA diagnosis and final diagnosis. There was a perfect agreement (Kappa Agreement = 0.97) with statistically significant difference between presumptive diagnosis and final diagnosis. Our study showed a relationship between EUS elastography and the final diagnosis of the lesions where soft pattern corresponded to most of the benign cases (67.60%) and firm pattern corresponded to most of the malignant cases (78.70%). Conclusion: EUS is a useful diagnostic tool for 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].
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][11][12][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 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.PR, prostate.
The internal stylet was introduced and the tissue material was extracted onto a slide using air injected with a syringe.The needle was pushed through the lesion once more after checking that the tissue material was sufficient.The procedure repeated for 1-4 times to provide sufficient samples.

Processing of cytological samples:
All cytological samples are processed and interpreted by experienced cytopathologists.The specimens were considered satisfactory when it contained an adequate population of representative cells.The aspirated samples expelled onto slides, and smears prepared.Then the remaining specimens, obtained from subsequent passing, were processed for cellblock evaluation.

Outcome:
The percentage of patients who had a proper diagnosis using EUS and cytopathological diagnosis from samples collected by EUS-FNA were measured.Before undergoing EUS, a presumptive diagnosis was determined based on the imaging and colonoscopy data.In patients who have had surgery, the final diagnosis was made based on cytopathological findings from resected specimens.Based on the long-term clinical course (at least six months) as well as the EUS-FNA results, the final diagnosis was reached in patients who did not have surgery.

Statistical Analysis:
Data verified, coded by the researcher, and analyzed using IBM-SPSS 21.Descriptive statistics: Means, standard deviations, medians, ranges, and percentages calculated.Test of significance: chi-square test used to compare the difference in distribution of frequencies among different groups.Kappa agreement calculated to explore the validity of the different diagnostic modalities against the final diagnosis where; a kappa of 0.01-0.20 = no/slight agreement, 0.21-0.40= fair agreement, 0.41-0.60= moderate agreement, 0.61-0.80= good agreement, 0.81-1= perfect agreement (14).A significant p-value was considered when it is equal or less than 0.05.
Regarding the final diagnosis and diagnosis made by EUS-FNA for the selected cases (for whom FNA was done, N = 26), five cases (19.20%) were benign, and 21 cases (80.80%) were malignant (figure 3).

Validity of Various Diagnostic Tools for Diagnosis of Malignancy:
Regarding the validity of the EUS for diagnosis of malignancy in all studied cases (N = 70), there was a perfect agreement (Kappa Agreement = 1) with statistically significant difference (P < 0.001) between EUS diagnosis and final diagnosis (table 2 and 6).
About the validity of the EUS-FNA for diagnosis of malignancy in the selected cases (N = 26), there was a perfect agreement (Kappa Agreement = 1) with statistically significant difference (P < 0.001) between EUS-FNA diagnosis and final diagnosis (table 3 and 6).
Regarding the validity of the colonoscopy for diagnosis of malignancy in all studied cases (N = 70), there was a perfect agreement (Kappa Agreement = 0.91) with statistically significant difference (P < 0.001) between colonoscopy diagnosis and final diagnosis with some disagreement (table 4 and 6).
About validity of the presumptive diagnosis (colonoscopy + imaging) for diagnosis of malignancy in all studied cases (N = 70), there was a perfect agreement (Kappa Agreement = 0.97) with statistically significant difference (P < 0.001) between presumptive diagnosis and final diagnosis with little disagreement (table 5 and  6).

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.
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.

Research highlights:
• There was a perfect agreement and a perfect diagnostic accuracy between EUS or EUS-FNA diagnosis and final diagnosis.• There was an excellent agreement (with some disagreement) and low diagnostic accuracy between colonoscopy diagnosis and final diagnosis.But by adding an imaging modality to colonoscopy, making the presumptive diagnosis, the diagnostic accuracy was excellent.• There was a relationship between EUS elastography and the final diagnosis of the lesions where soft pattern corresponded to most of the benign cases and firm pattern corresponded to most of the malignant cases.• EUS alone without FNA may be sufficient for diagnosis of rectal and perirectal lesions on condition that high experience in endosonographgy.

Figure 1 :
Figure 1: Rectal endoscopic ultrasound of some of the studied cases.A) rectal mass (white arrow) and cytopathology revealed adenocarcinoma, B) rectal mass (white arrow) with cytopathology revealed gastrointestinal stromal tumor, C) perirectal lymph node (white arrow).

Figure 2 :
Figure 2: Final diagnosis of all studied cases according to disease nature.GIST, gastrointestinal stromal tumor; UC, ulcerative colitis.

Figure 3 :
Figure 3: Final diagnosis of the selected cases according to disease nature.GIST, gastrointestinal stromal tumor.

Table ( 1): Demographic characteristics and medical history of the studied cases.
Data expressed in the form of frequency (percentage) or mean (standard deviation) as appropriate.

Table ( 5): Validity of the presumptive diagnosis (Imaging + Colonoscopy) for diagnosis of malignancy.
Data expressed in the form of frequency (percentage) as appropriate.

Table ( 6): Performance characteristics of various diagnostic tools for diagnosis of malignancy.
Note: Data expressed in the form of percentage as appropriate.EUS, endoscopic ultrasound; EUS-FNA, endoscopic ultrasound-guided fine needle aspiration.

Table ( 7): Relationship between EUS elastography and final diagnosis.
Data expressed in the form of frequency (percentage) as appropriate.A significant p-value was considered when it is equal or less than 0.05.EUS, endoscopic ultrasound.