Manual for abdominal ultrasound in cancer screening and health checkups, revised edition (2021)

Shinji Okaniwa1 · Toshiko Hirai2 · Masahiro Ogawa3 · Sachiko Tanaka4 · Kazuo Inui5 · Takashi Wada6 · Naoki Matsumoto3 · Shigehiko Nishimura7 · Yuko Chiba8 · Hiroyoshi Onodera9 · Takashi Kumada10 · Masahisa Kojima11 · Michiko Nakajima12 · Yoshihiro Mizuma13 · Shinji Tanaka14 · Toru Nishikawa15 · Shuichi Mihara16 · Yoshioki Yoda17 · Masaki Adachi18 · Tomofumi Atarashi19 · Working Group on Revision of the Manual for Abdominal Ultrasound in Cancer Screening and Health Checkups, Ultrasound Screening Committee of the Japanese Society of Gastrointestinal Cancer Screening


Introduction
This manual is a revised version of the first edition [1][2][3] published jointly by the Japanese Society of Gastrointestinal Cancer Screening (JSGCS), the Japan Society of Ultrasonics in Medicine (JSUM), and Japan Society of Ningen Dock (JSND) in 2014.
Abdominal ultrasonography is distinct in that it is used to examine many organs, and it is applicable various kinds of disease including malignant neoplasm. Moreover, a procedure for describing examination findings had not been standardized. Therefore, its objective accuracy and efficacy as a screening modality could not be evaluated. In addition, there were no clear rules regarding examination procedures at any of the societies. Against this backdrop, the Guideline for Abdominal Ultrasound Cancer Screening [4,5]-which was comprised of practice standards aimed at improving the quality of abdominal ultrasound cancer screening, and assessment criteria to allow for accurate assessment as a cancer screening modality-was published in 2011, led by the JSGCS Ultrasonic Screening Committee (former Ultrasonography Working Group). The Abdominal Ultrasound Screening Assessment Manual was subsequently created through a joint effort by the above-mentioned three societies by partially revising the Guideline and adding items and assessments. The aim was to improve the quality of and homogenize abdominal ultrasound screening, standardize examination results, and evaluate accuracy and efficacy through the widespread adoption of the Guideline by creating a manual shared by the three societies.
This revision had been planned to take place about 5 years after the original publication. The manual was revised by working groups at each of the three societies, with the additional participation of the Japanese Society of Sonographers (JSS), Japan Society of Health Evaluation and Promotion (JSHEP), and Japanese Association for Cancer Detection and Diagnosis (JACDD) as observer societies, based on current experience. The manual was created with the following structure: practice standards and specific ultrasound findings and categories, tables with ultrasound findings in Report Forms and assessments presented 1:1 and cautionary notes, and representative ultrasound images of the respective findings.
It is a well-known fact that the accuracy of ultrasonography differs depending on the status of the device, examiner, and examinee. In modern medicine, standards are required in terms of ergonomics and device conditions (including periodic inspections) to improve examination quality; the practice standards in this manual were revised based on the guidelines of each society as well as other sources. Although evidence is lacking in some areas and they are not required, we hope that institutions will refer to this manual as a rule of thumb for the current examination environment.
The biggest shortcoming of ultrasonography is a lack of objectivity, which it true of not only ultrasound images but also ultrasound findings and assessments. When we consider such factors as examinee/examiner transfers and diversification of secondary examination facilities, we predict a dramatic improvement in objectivity with the permeation of this manual, and we look forward to its widespread adoption going forward.

Practice standards
(1) Before beginning an examination In terms of screening techniques performed primarily on people without symptoms, we have the "medical checkup," which is used to check and learn the level of an individual's health or check for risk of future disease, and "screening," the purpose of which is to check for the presence or absence of a specific disease. It should be noted that there are examinations where the two cannot be clearly distinguished based on the examination items [6]. Cancer screening, which is a typical screening, has two types: a population-based type carried out by municipalities and an opportunistic type carried out in other situations. In the case of population-based cancer screening, the Japanese government has proposed screening for five major cancers by modalities confirmed to lower the mortality rate. In addition to opportunistic cancer screening for hepatic cancer, renal cancer, and other cancers, this Abdominal Ultrasound Screening Assessment Manual also covers "screenings" to check for the presence or absence of disorders such as gallstones, as well as "medical checkups" to check for future disease risk such as hepatic steatosis and arteriosclerosis.
There are merits and demerits with any cancer screening, not just ultrasonography, but the merits must outweigh the demerits. Therefore, the examiner needs to understand the merits and demerits of cancer screening and improve the quality of the screening, and the examiner must obtain proper informed consent from the examinee. It is also important to understand that there are two distinct reasons for performing a thorough examination in response to an abnormal finding detected by screening: one is to make a definitive diagnosis of cancer and the other is to rule out suspected cancer. Merits • Early treatment based on early detection of cancer is possible.
• Psychological sense of relief when no abnormalities are found.

Demerits
• Possibility of false-negative tests (ultrasonography does not detect 100% of cancers). • Possibility of false-positive tests (as a result, there is a possibility of examinee complications associated with unnecessary invasive procedures and examinations, and being subjected to psychological and economic strain). • Possibility of overdiagnosis (detection of cancer that does not affect the vital prognosis).
(2) Target organs • The target organs covered in this Manual are the liver, biliary tract, pancreas, spleen, kidneys, and abdominal aorta. • Tell the examinee the target organs in advance, and explain that there may be some cases and sites where each organ may be difficult to observe. • The adrenal gland and lower abdominal region (e.g., bladder, uterus, ovaries, and prostate) are not formally regarded as target organs, but any findings observed during the scanning process should be recorded. In addition, in cases where a target organ will be added with a voluntary contract with the client, clearly communicate the details of the examination to the examinee.
(3) Examination environment [1] Diagnostic unit • Use a convex probe with a frequency of 3.5-7.0 MHz. • Add other probes such as a high-frequency probe (7.5 MHz or higher), linear probe, or microconvex probe as necessary according to the examinee's situation. • Use of a unit capable of tissue harmonic imaging and color Doppler is recommended. • Periodically perform appropriate maintenance/ management of the diagnostic unit, and avoid using a unit beyond its service life (normally 7 years).
[2] Operators A JSGCS gastrointestinal cancer screening general certified physician or gastrointestinal cancer screening certified physician (hepatobiliary system and pancreas), JSUM specialist or technician with an ultrasonographer qualification in the medical checkup domain or gastrointestinal domain certified by JSUM, Board Certified Physician of JSND, Health Evaluation and Promotion Specialist of JSHEP/JSND, Japan Radiological Society (JRS) radiology specialist, or Japanese Society of Laboratory Medicine (JSLM) clinical laboratory test specialist should be in charge of the examination. [3] Advanced preparation • Examinees with an examination scheduled for the morning should not eat solid foods or dairy products after 10 p.m. the night before. • Examinees with an examination scheduled for the afternoon should not eat solid foods or dairy products within 6 h before the examination. • Drinking liquids (e.g., cold/hot water) to prevent dehydration is allowed up to about 200 ml per time up to 2 h before the examination. • In cases where a gastrointestinal tract examination will be performed the same day, perform ultrasonography first, with the exception of upper endoscopy using carbon dioxide [7].
[4] Peripheral facilities • A proper examination environment is said to not only lessen examiner fatigue but also prevent misdiagnosis, making it an important factor. • In addition to a private room to protect the examinee's privacy or equivalent examination room, there is an ergonomically recommended environment that encompasses everything including the heights of the examining table, chair, and monitor; therefore, one should aim to perform examinations under the correct environment (Refer to "Proposal from The Japan Society of Ultrasonics in Medicine for ultrasonographers to work safely, comfortably, and healthily: Equipment and work environment to prevent work-related musculoskeletal disorders and eye disorders" [8]).
[5] Precautions during epidemics • The COVID-19 pandemic completely changed how screenings are performed. Examiners will need to familiarize themselves with ultrasonography-related precautions during epidemics in preparation for new infectious diseases in the future based on this experience. • Ultrasonography has distinct examination procedures, sanitization procedures, and so forth that differ from those of other medical care.
• Take into account ultrasound screening methods during epidemics by referring to such sources as the Ultrasound Equipment and Safety Committee's "Recommendations and resources related to handling and safety of ultrasonic diagnostic equipment" [9][10][11] published on the JSUM website.
[6] Recording and scanning procedures • There are a variety of image recording/storage methods depending on the institution, such as storage using a thermal printer, storage as DICOM data, and video storage on videotape/DVD. However, storage of DICOM data on electronic media is recommended from the viewpoint of secondary image interpretation and sending referral attachments to facilities for thorough examination. • Perform measurements with the image adequately enlarged on the monitor, and denote measurements in millimeters, rounding off to the nearest integer. (However, evaluation of an entire organ can be denoted in centimeters.) • For Category 3 or severer lesions and focal lesions, always record images from multiple directions, and also record and save the maximum diameter/ scan site at the same time. • With respect to the scanning procedure, carefully and thoroughly observing the entirety of each organ as a basic ultrasound scan, and properly evaluating not only focal lesions but also diffuse lesions throughout an entire organ, are fundamental. • With respect to standards for sections to store during examinations, there is no nationwide uniform method. However, fundamental sections should be established to properly deal with situations, such as demonstration of the examination region, quality control, double interpretation, comparison of changes over time, referral to other institutions, education, and transfer of examiners/examinees. • With respect to the position of the examinee, scans are almost always performed with the examinee in the supine position, but since the visualization capability of ultrasonography changes with a change of position, appropriate position changes (e.g., right and left half side-lying position, right and left lateral position, semi-sitting position, and sitting position) should be utilized in cases where observation in the supine position is insufficient. • The time required for examinations will differ depending on the examination environment, but about 5-6 people without findings can be screened per hour (Ample time should be allocated as examination duration correlates with examination accuracy and the ability of the examiner.) • Twenty-five recommended sections to record [12] and images by position change are presented here (Fig. 1, Fig. 2).
[7] Examination results/image interpretation/ultrasound image findings/assessments/post-examination management • For examination results, record the results using the categories described later together with a record of the ultrasonography findings (   examinees should be instructed to visit and referred to an appropriate medical institution according to the screening results. In addition, it is important to maintain a line of communication with the receiving institution, so that requests can be made for feedback on the results of thorough examinations as it will serve as important information at annual screenings. • When writing a referral, include not only the test results but also clearly state the details of the request for thorough examination, and also attach images from the entire examination (DICOM digital images are recommended).
(6) Quality control • Controlling the screening process as a whole so that it is always properly performed is important in order for ultrasound screening to continue to be effective as a cancer screening modality going forward. In addition to internal quality control, it is recommended that the process also undergoes periodic outside evaluation. • In addition to control of the examination environment including the diagnostic unit, quality control includes but is not limited to tabulation and management of examination results (e.g., percentage of examinees who required thorough examination, percentage of examinees who underwent thorough examination by category assessment, and cancer detection rate), ascertainment and tabulation of post-examination guidance (e.g., ascertainment and tracking of examinees who did and did not undergo thorough examination, screening recommendation, and ascertainment of screening sensitivity/specificity), and cooperation with and registration in nationwide tabulation.

Categories and assessments
(1) Ultrasound imaging findings • Operators should consider in detail to which ultrasound imaging finding item in the Manual the abnormal findings noted in observations of the liver, biliary tract, pancreas, spleen, kidneys, abdominal aorta, and other target organs correspond and select the applicable item. • Although observation of organs other than the target organs is not essential, describe any findings that are noted. • If an organ cannot be visualized at all, it should be assessed as "Unable to visualize." If part of an organ cannot be visualized, it should be assessed as "Poorly visualized" and regarded as equivalent to "Difficult to visualize" and "Inadequately visualized," and cases where the border is indistinct after partial resection, etc., should be included in this category; clearly describe poorly visualized sites and use findings from sites that could be visualized.
(2) (Categories (Tables 1, 2) • The cancer-related category, ultrasound findings (described in Report Form), and assessment are determined in accordance with the ultrasound imaging findings selected. • Categories are criteria for cancer detection and also summaries of findings noted during ultrasonography. • For each organ, the highest category should be recorded as the category for the organ. However, in cases where the highest category and highest assessment differ, both should be recorded (e.g., Category 2/Assessment D2, Category 3/Assessment C). • For a lesion that can be compared with a past image, record comments on any chronological changes. • If a lesion has findings corresponding to Assessment D2 or higher on ultrasound images but has been deemed to be benign as a result of thorough examination, the relevant category is indicated with an apostrophe [e.g., 0', 2', 3', 4'], and the assessment is C. (Note that the high-risk group is not included in this category.) ( Fig. 3) (3) Ultrasound findings (described in Report Form) It consists of simplified terms for notification of ultrasound imaging findings to examinees. Ultrasound  findings are described in the Report Form. Categories 4 and 5 are described as "Tumor" and Category 3 focal lesions as "Mass," including suspected ones.
(4) Assessment (Table 3) As a rule, the final assessment is determined by the physician in charge of assessment in accordance with the Manual based on abnormal findings on ultrasound images. However, the physician in charge of assessment can change the assessment as necessary based on test results other than ultrasonography and comparison with previous findings. Notes • P: Panic finding, Promptly report Category 5 lesions to the physician in charge of assessment. • Promptly report it to the physician in charge of assessment in the case of findings indicative of transition to an emergency situation such as biliary stone. • For Assessment C, the term "Follow-up observation needed" had been used until now, but the timing of follow-up observation was unclear; therefore, "Reexamination needed" will be used instead going forward to standardize the terminology at institutions, and the specific timing will be entered. • The reexamination timing selected was 3/6/12 months, but it can be changed at the direction of the physician in charge of assessment. • Reexaminations will be performed at a medical institution as necessary, but in the case of the 12-month reexamination, the examinee should be strongly recommended to undergo screening the following year. • In the case of Category 2', 3', or 4' with Assessment C, ultrasonography at the annual screening 12 months later may be used as a substitute for reexamination.
• If "Reexamination needed" is selected, the examinee should be given specific instructions regarding the institution to visit for reexamination. • If "Thorough examination needed" is selected, the examinee should be given specific instructions regarding the institution to visit for thorough examination and examination procedures, etc. • When the examinee undergoes reexamination (e.g., during dietary therapy for hepatic steatosis, or main pancreatic duct dilatation/pancreatic cyst) either inhouse or at another institution (every 3/6/12 months), the assessment should be C, not E. • Assessment C or E may be selected if the examinee has undergone thorough examination at another medical institution and continues to be followed up by the institution. However, for an examinee in the group at high risk for cancer, Assessment D2 may be selected after hearing the details of examinations performed at the medical institution. • A Category 3 lesion may be assessed as C if there are no chronological changes compared with at least the past 2 results. • Assessment D2 may be selected as necessary if the diameter of the focal lesion or lumen definitely increases compared to the previous result. • If organ atrophy is found, refer to the past medical history, history of present illness, or treatment history when making the assessment. • In the case of total resection, partial resection, or detection of treatment scar, refer to the past medical history or history of present illness when making the assessment. • Make use of color Doppler ultrasound as appropriate to aid assessment. • Assessment D2 may be selected as necessary for a focal lesion in the liver if chronic hepatic disease is suspected based on clinical biochemistry data such as infection   (continued) *1) Those without findings of recurrence after local treatment are not regarded as neoplastic lesions. In the case of partial resection, document the resection site if known, and evaluate the ultrasound imaging findings of the remaining portion *2) A congenital deformity (e.g., partial atrophy) is regarded as Category 2 and Assessment B, and parts other than the deformed part are evaluated using the same method as others *3) Compare the brightness of the liver parenchyma with the healthy kidney at the same depth (compare with the spleen in cases with chronic renal failure). Check the spleen-kidney contrast and evaluate the liver-kidney contrast if there is no difference in brightness between the spleen and kidney. If it is an irregular hypoechoic area in a commonly focal spared area without a disturbed speckle pattern, and no deviation of blood vessel is detected on color Doppler, it is not considered a solid lesion (Fig. 3) *4) During evaluation of the liver parenchyma, if the flag sign or bamboo blind sign is found, include it in rough parenchymal echo pattern *5) Lesions in which an internal change is detected such as the "sludge worm" sign are placed in this category *6) Mosaic pattern (same as nodule in nodule): An echo pattern formed by a mosaic array of nodules within a mass. Characteristically seen in hepatocellular carcinoma. Bright loop appearance: This term refers to the state after dedifferentiation of hepatocellular carcinoma in which hypoechoic nodules appear in hyperechoic nodules. Hump sign: This refers to observation of a protrusion on the surface of a solid organ made by a tumor, etc. *7) Cluster sign: Visualized as a cluster of many aggregated masses, it is characteristic of metastatic liver tumors. Bull's eye pattern (same as target sign): An echo pattern where the internal echo of a mass, etc., exhibits a concentric circular structure *8) All cystic lesions with definite wall thickness should be regarded as wall thickening. Changes in internal fluid (e.g., intracystic hemorrhage/ infection) are also subject to thorough examination as the possibility of neoplasticity cannot be ruled out. In addition, neoplastic cysts, the generic term for cysts covered with cells showing neoplastic proliferation, are also included in this category *9) If peripheral bile duct dilatation due to a hepatic cyst is present, thorough examination is required as there is a possibility of cystic tumor involvement and cases in which treatment is indicated are included *10) The comet-like echo found in biliary hamartoma, etc., is included. Pneumobilia and calcification/lithiasis should be differentiated by movement status at position change or while breathing *11) The threshold for dilatation of the intrahepatic bile duct is ≥ 4 mm (round off to the nearest integer) (right and left hepatic ducts are extrahepatic hepatic ducts). Localized bile duct dilatation without a mass lesion and post-bile duct surgery are also included *12) In addition to portal-venous shunts, arterial-portal shunts, and arterial-venous shunts, vascular abnormalities include but are not limited to portal hypertension findings including extrahepatic collateral flow, aneurysms, and portal aneurysms. However, mild portal aneurysms or portalvenous shunts deemed to have no effect on the pathologic condition should be regarded as Category 2 and Assessment C. In addition, mass lesion-related vascular abnormalities should be evaluated in the same manner as mass lesions (Fig. 36  3 Diffuse gallbladder wall thickening D2 Figure 40 If small cystic structure or comet-like echo is present 2 Gallbladder adenomyomatosis C Figure 41 With irregularity or disruption of the layered structure of the wall       The gallbladder wall is inevaluable (the wall is inevaluable due to being filled with stones). Category 3, Assessment D2 Fig. 38 The gallbladder wall is inevaluable (the wall is inevaluable due to food intake). Category 3, Assessment D2        Table 7 Spleen *1) In the case of partial resection, document the resection site if known, and evaluate the remaining portion using the same method as others *2) Confirm the presence or absence of excision, and regard as unable to visualize if the presence or absence of swelling cannot be assessed, but there is no need for thorough examination *3) Regard a congenital deformity (e.g., polysplenia) as Category 2 and Assessment B, and evaluate the remaining portion using the same method as others *4) With respect to the size of the spleen, the reference range differs depending on the age and build of the examinee *5) All cystic lesions with definite wall thickness should be regarded as wall thickening. In addition, changes in internal fluid (e.g., intracystic hemorrhage/infection) are regarded as Category 4 and Assessment D2 as the possibility of a cystic tumor cannot be ruled out (Fig. 104) *6) In addition to aneurysms, this includes abnormalities of the splenic hilum such as collateral flow of the splenic vein. However, mass lesionrelated vascular abnormalities should be evaluated in the same manner as mass lesions. The measured value should be the maximum diameter   Internal anechoic region is present in round lesion with distinct border and smooth contour 5

Renal tumor D1
Internal anechoic region is present with either of peripheral hypoechoic zone or lateral shadow 5 Renal tumor D1 Figure 117 Brightness equal to or higher than that of the central echo complex with irregular contour or comet image Maximum diameter < 40 mm *5), *6) 2 Renal angiomyolipoma C Figures   Vascular abnormality *12) 2 Renal vascular abnormality D2 Figure 138, 139 No abnormal findings 1 Normal kidneys A ture similar to that of the normal renal parenchyma on color Doppler *4) Solid lesions < 10 mm can be regarded as Assessment C (because cases with a small tumor diameter show slow tumor growth, although some cases where it is difficult to differentiate from renal carcinoma are included) *5) Comet image refers to an ultrasound image where the echo of the posterior surface of a lesion becomes indistinct due to multiple reflection, making it look like an enlarged comet-like echo with deep echo attenuation *6) A renal angiomyolipoma < 40 mm showing signs or symptoms of enlargement can be regarded as Assessment D2 as there is a risk of rupture *7) Cysts with two or fewer thin septi and microcalcification are regarded as Category 2 and Assessment B *8) In cases where the longest diameter of either of the kidneys is ≤ 9 cm, the likelihood is high that it is a simple cyst rather than polycystic kidney disease, and it can be regarded as Category 2 and Assessment C (Fig. 104) *9) Changes in internal fluid (e.g., intracystic hemorrhage/infection) are also subject to thorough examination as the possibility of neoplasticity cannot be ruled out. In addition, neoplastic cysts, the generic term for cysts covered with cells showing neoplastic proliferation, are also included in this category *10) If it cannot be determined whether it is in the renal parenchyma or in the pelviocaliceal system, regard it as nephrocalcinosis or renal stone, and regard < 10 mm as Assessment C and ≥ 10 mm as Assessment D2 *11) Document the occluded site if known * 12) Vascular abnormalities include vascular aneurysms, arterial-venous shunts (including arteriovenous malformation), venous emboli (thrombi), collateral flow and so on. However, vascular abnormalities associated with solid lesions should be evaluated according to the criteria for solid lesion (Fig. 140)  Table 9 Abdominal aorta * Panic finding: Add "P" to the assessment in the case of an urgent condition *1) Examinees who have undergone stent-graft insertion for aortic aneurysm are assessed as D2P* if the maximum aneurysm diameter has increased since the last examination (including before treatment) *2) Measure the aorta diameter as shown in Fig. 140 (according to The Japan Society of Ultrasonics in Medicine Terminology and Diagnostic Criteria Committee: Standard Evaluation Methods for Aortic Lesions Using Ultrasound 2020) *3) For saccular dilatation or fusiform dilatation ≥ 55 mm in maximum diameter, report it to the physician in charge of assessment as "P" as the risk of rupture is high *4) As a rule, the assessment of aortic dissection is D2, but fusiform aortic aneurysm applies depending on the extent of the dilatation. Assess as D2P if it is a new finding *5) If particularly large plaque or mobile plaque is found in the aorta, it can be documented. Wall thickening, calcification, or other findings can also be documented separately   Lymph-node swelling Short diameter ≥ 7 mm *1) 3 Lymph-node swelling C Figure 148 Either short diameter ≥ 10 mm or short/long diameter ratio ≥ 0.5 4 Lymph-node swelling D2 Figure 149 Intraperitoneal fluid retention Fluid retention is present *2) 3 Ascites D2 Figure 150, 151 Intrathoracic fluid retention Fluid retention is present *2) 3 Pleural effusion D2 Figure 152, 153, 154 Fluid retention in cardiac cavity Fluid retention is present *3) 2 Pericardial effusion D2 Figure 155 Abdominal cavity, retroperitoneum, or pelvic cavity (including adrenal gland) Mass image is present *4) 3 Abdominal mass D2 Figure 156, 157