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ERROR: type should be string, got "https://profreg.medscape.com/px/getpracticeprofile.do?method=getProfessionalProfile&urlCache=aHR0cHM6Ly9lbWVkaWNpbmUubWVkc2NhcGUuY29tL2FydGljbGUvMzc1MTY2LW92ZXJ2aWV3\nDrugs & Diseases > Radiology\nUlcerative Colitis Imaging\nAuthor: Ali Nawaz Khan, MBBS, FRCS, FRCP, FRCR; Chief Editor: Eugene C Lin, MD more...\nSections Ulcerative Colitis Imaging\nNuclear Imaging\nUlcerative colitis (UC) is a type of inflammatory bowel disease (IBD), along with Crohn disease (CD). Unlike Crohn disease, which can affect any part of the gastrointestinal tract, ulcerative colitis characteristically involves the large bowel. UC mainly affects the rectum and sigmoid colon, but it may involve the entire colon and the terminal ileum. In addition, cases with proximal involvement have been described (eg, diffuse gastritis, focally enhanced gastritis, and duodenitis). [1, 2, 3, 4, 5]\nUC is a multifactorial polygenic disease; the exact etiology is unknown. Included in the etiologic theories are environmental factors, immune dysfunction, and a likely genetic predisposition. Children of below-average birth weight who are born to mothers with ulcerative colitis may have a greater risk of developing the disease.\nDouble-contrast barium enema study shows changes of early disease. Note the granular mucosa.\nSingle-contrast enema study in a patient with total colitis shows mucosal ulcers with a variety of shapes, including collar-button ulcers, in which undermining of the ulcers occurs, and double-tracking ulcers, in which the ulcers are longitudinally orientated.\nPostevacuation image obtained after a single-contrast barium enema study shows extensive mucosal ulceration resulting from Shigella colitis.\nHistocompatibility human leukocyte antigen (HLA)–B27 is identified in most patients with ulcerative colitis, though this finding is not associated with the condition. Immune dysfunction has been postulated as a cause, although the clear evidence of this is limited. Ulcerative colitis might also be linked to diet, though diet is thought to play a secondary role. Food or bacterial antigens might exert an effect on the already damaged mucosal lining, which has increased permeability.\nThe severity of ulcerative colitis can be graded as follows:\nMild — Bleeding per rectum and fewer than 4 bowel motions per day\nModerate — Bleeding per rectum with more than 4 bowel motions per day\nSevere — Bleeding per rectum, more than 4 bowel motions per day, and a systemic illness with hypoalbuminemia (< 30 g/L)\nPatients are defined as having extensive disease if inflammation extends proximal to the splenic flexure; left-sided disease if inflammation extends proximal to the rectum but not past the splenic flexure (or < 50 cm from the anus); and proctitis if inflammation is limited to the rectum (or < 15–20 cm from the anus). Both disease severity and anatomic extent are important in choosing appropriate treatment.\nPreferred examination\nTraditionally, barium enema examination has been the mainstay of radiologic investigation for suspected ulcerative colitis. Plain abdominal radiographs (see the images below) are a useful adjunct to imaging in cases of ulcerative colitis of acute onset. In severe cases, the images may show colonic dilatation, suggesting toxic megacolon, perforation, obstruction, or ileus. Radiographic imaging has an important role in the workup of patients with suspected IBD and in the differentiation of ulcerative colitis and Crohn disease. Because of its ability to depict fine mucosal detail, double-contrast barium enema examination is a valuable technique for diagnosing ulcerative colitis and Crohn disease, even in patients with early disease. [6, 7, 8]\nDouble-contrast barium enema studies in a 44-year-old man known to have a long history of ulcerative colitis. Images show total colitis and extensive pseudopolyposis.\nPlain abdominal radiograph in a patient (same as in the previous image) who presented with an acute exacerbation of his symptoms. Image shows thumbprinting in the region of the splenic flexure of the colon.\nPlain abdominal radiograph obtained 2 days later in the same patient as in the previous image shows distention of the transverse colon associated with mucosal edema. The maximum transverse diameter of the transverse colon is 7.5 cm. The patient was treated for toxic megacolon.\nTransabdominal ultrasonography (US) is a noninvasive modality that may be helpful in the diagnosis of IBD, but it cannot be used to distinguish between ulcerative colitis and Crohn disease. US is also a useful technique in the investigation of biliary complications of the disease. [9]\nCapsule endoscopy is sensitive for early mucosal inflammation, but it can only detect mucosal changes, whereas magnetic resonance imaging (MRI) and intestinal ultrasonography are able to reveal transmural inflammation as well as identify complications\nGenerally, CT has a limited role in the diagnosis of uncomplicated ulcerative colitis. However, CT plays an important role in the differential diagnosis of ulcerative colitis, and it is an excellent modality in the diagnosis of complications associated with the disease. Biliary dilatation suggests primary sclerosing cholangitis.\nComputed tomography enterography (CTE), with its high contrast resolution and rapid imaging capability, allows evaluation of intramural and extra-intestinal involvement of UC and complications such as fistula, abdominal abscess, or cellulitis. CTE is now widely used to diagnose and monitor inflammatory bowel disease (IBD), including UC. [10]\nCross-sectional imaging studies such as CT, MRI, and US are useful for showing the effects of these conditions on the wall of the bowel and for demonstrating intra-abdominal abscesses and other extraluminal findings in patients with more advanced disease. Thus, barium studies and cross-sectional imaging studies have complementary roles in the evaluation of ulcerative colitis. [11, 9]\nRadionuclide studies (see the image below) are useful in cases of acute fulminant colitis when colonoscopy or barium enema examination is contraindicated. Radionuclide studies are also useful in depicting disease activity and the extent of disease and in monitoring the response to therapy. [12]\nRadiologic findings in cases of acute infective enterocolitis from infection caused by Entamoeba histolytica (amebiasis), cytomegaloviral colitis, and Isospora, Salmonella, Shigella, or Yersinia may be similar to the findings seen in cases of ulcerative colitis; this is especially true with CT scans.\nScan obtained with technetium-99m hexamethylpropylamine oxime (HMPAO)–labeled WBCs in a patient with active colitis involving the transverse and descending colon.\nHistologic scoring systems for UC include the Geboes score, the Nancy score, and the Robarts Histopathology Index. [4, 13, 14, 15, 16] The Geboes score has 6 grades: 0, structural change only; 1, chronic inflammation; 2, lamina propria neutrophils; 3, neutrophils in epithelium; 4, crypt destruction; and 5, erosions or ulcers. The Nancy score includes 3 histologic items that define 5 grades of activity: absence of significant histologic disease, chronic inflammatory infiltrate with no acute inflammatory infiltrate, mildly active disease, moderately active disease, and severely active disease. The Robarts histopathology index includes 4 grades: chronic inflammatory infiltrate, lamina propria neutrophils, neutrophils in the epithelium, and erosions or ulcerations.\nLimitations of techniques\nAll imaging techniques lack specificity. Mucosal ulceration depicted on barium studies is nonspecific and is encountered in a variety of colitides. In severe cases, barium enema may precipitate toxic megacolon. Generally, barium enemas may be performed safely only in mild cases. Thickening of the bowel wall, as seen on cross-sectional imaging (CT, MRI, and US), is a nonspecific finding seen in a variety of bowel conditions besides IBD. Increased radionuclide focal activity may be related to a variety of physiologic and pathologic conditions unrelated to ulcerative colitis. Motion artifacts may interfere with cross-sectional imaging. Although this is not a major problem with modern scanners, some investigators still use a hypotonic agent to decrease bowel peristalsis.\nFor patient information resources, see the Crohn Disease Center and the Esophagus, Stomach, and Intestine Center, as well as Crohn Disease and Crohn Disease FAQs.\nPlain radiographic findings\nPlain radiographs frequently yield useful information that may serve as a guide to further clinical evaluation and imaging (see the images below). The intraluminal gas pattern may show pseudopolyposis and deep ulcers. The colon may appear shortened, with associated loss of colonic haustra. Toxic megacolon is a complication of ulcerative colitis. The plain abdominal radiograph may show massive colonic dilatation associated with an abnormal mucosal contour. The dilatation is most pronounced in the transverse colon. Colonic perforation is another known complication of ulcerative colitis. Perforation may occur with or without a toxic megacolon. Pneumoperitoneum associated with a colonic perforation is usually massive. Fecal residue may be absent in inflamed bowel.\nPlain abdominal radiograph in a patient with known ulcerative colitis who presented with abdominal pain, peritonism, and leukocytosis. At surgery, a perforated toxic megacolon superimposed on ulcerative colitis was confirmed.\nIncreased postrectal space is a known feature of ulcerative colitis.\nPlain abdominal radiograph on a patient with known ulcerative colitis who presented with an acute exacerbation of his symptoms. Image shows thumbprinting in the region of the splenic flexure of the colon.\nPlain abdominal radiograph in a 26-year-old with a 10-year history of ulcerative colitis shows a long stricture/spasm of the ascending colon/cecum. Note the pseudopolyposis in the descending colon.\nLateral radiograph of the lumbar spine shows a bamboo spine.\nBarium enema findings\nThe findings on a barium enema examination vary with the stage and severity of disease (see the images below). The radiographic changes may involve the whole colon; when the disease is segmental, the left colon is usually involved. Rectal sparing is rare; it is thought to occur in 5% of cases. Skip lesions are unusual. The colon may appear narrow; such narrowing is often associated with incomplete filling caused by colonic spasm and irritability.\nDouble-contrast barium enema studies show changes of early disease. Note the granular mucosa.\nDouble-contrast barium enema study shows pseudopolyposis of the descending colon.\nSingle-contrast enema study in a patient (same patient as in the previous image) with known ulcerative colitis in remission shows a benign stricture of the sigmoid colon.\nDouble-contrast barium enema study shows total colitis. Note the granular mucosa in the cecum/ascending colon and multiple strictures in the transverse and descending colon in a patient with a more than a 20-year history of ulcerative colitis.\nSingle-contrast barium enema study shows burnt-out ulcerative colitis.\nSingle-contrast barium enema study in a patient with Shigella colitis.\nDouble-contrast barium enema studies show granular mucosa associated with Campylobacter colitis.\nThe earliest mucosal changes are best depicted on a good-quality double-contrast barium enema study. Before ulcers appear, mucosal edema has a fine, granular appearance when the radiographs are seen en face. When ulcers first appear, the mucosa may have a fine, stippled appearance when seen en face. When mucosal ulcers become established and confluent, the mucosa is replaced by granulation tissue; on double-contrast enema examination, the characteristic appearance is coarsely granular.\nIn the acute and subacute phases of the disease, the ulcers may acquire a variety of shapes: collar-button ulcers occur with undermining of the ulcers; double-tracking ulcers are longitudinally orientated and are sometimes several centimeters long.\nSymmetrical thickening of haustral folds may produce the appearance of thumbprinting. Pseudopolyps are a consequence of severe mucosal disease; they appear as multiple filling defects of varying sizes. These may develop rapidly, and they tend to persist, even when ulcerative colitis is quiescent. Occasionally, mucosal bridges are formed between pseudopolyps, which may be radiologically demonstrable.\nWith increased severity and duration of disease, the involved colon may become narrow, shortened, and loose in terms of its normal redundancy and haustral pattern. On lateral projections, rectal narrowing is easily recognizable as increased retrorectal space. When the entire colon is involved, changes in the terminal ileum may be seen (backwater ileitis); this involves 4-25 cm of the terminal ileum. The ileocecal valve appears patulous. The mucosa is granular and is usually associated with the absence of peristalsis.\nBenign strictures occur in 1-11% of patients with long-standing disease. Such strictures are predominantly found in the left colon. Carcinomas that complicate ulcerative colitis are usually annular and may be difficult to differentiate from benign strictures. Often, however, malignant strictures are eccentric, with nodular narrowing and shouldered edges. Multiple carcinomas are not rare in the setting of ulcerative colitis. About 50% of these tumors are not detected on clinical or radiologic examination; instead, they are diagnosed at colectomy or autopsy.\nThe diagnostic signs of various colitides overlap considerably. Similar radiographic signs may be seen in cases of infective diarrhea, Crohn disease, ischemic colitis, drug-induced colitis, and amebic colitis. Infective diarrhea is occasionally the presenting feature of IBD.\nWith increased use of CT as a primary imaging modality for evaluating inflammatory bowel disease (IBD), radiologists must be able to recognize the features of ulcerative colitis on CT. Although barium studies remain the principal tool for diagnosing and evaluating suspected IBD, CT may aid in differentiating ulcerative colitis and Crohn disease when results of barium studies are equivocal. High-resolution thin-section imaging of both the intraluminal and extraluminal components enables radiologists to detect and stage colonic pathology. [17, 18, 19, 20, 21]\nCT is valuable for the detection and characterization of ulcerative colitis. CT typically demonstrates circumferential, symmetrical wall thickening with fold enlargement. Thickening of the colon wall (mean, 7.8 mm; standard deviation, 1.9) may be present, with inhomogeneous attenuation, a target appearance of the rectum, and the proliferation of perirectal fat. The normal colonic wall has a maximal thickness of 3 mm with the lumen distended and 5 mm with the lumen collapsed. In comparison, Crohn colitis causes greater bowel wall thickening (mean, 11 mm; standard deviation, 5.1). Such thickening appears in association with homogeneous attenuation, fistula and abscess formation, and mesenteric abnormalities.\nThe target sign consists of an inner ring of soft tissue attenuation, representing mucosa, lamina propria, and enlarged muscularis mucosa; a middle ring of low attenuation, resulting from widening and fatty infiltration or edema of the submucosa; and an outer area of soft tissue attenuation, representing the muscularis propria. If the submucosa is infiltrated by fat, this is a sign of chronicity; it is more specific to IBD. This sign is best appreciated on the arterial phase of enhancement. It is a nonspecific sign that is also reported in cases of Crohn disease and pseudomembranous colitis.\nUlcerative colitis is typically left sided or diffuse; only rarely does it involve the right colon exclusively. In cases of ulcerative colitis, wall thickening may be diffuse and symmetrical; by contrast, in cases of Crohn disease, wall thickening is eccentric and segmental, and skip lesions are present. The proliferation of perirectal fat is a nonspecific sign that can be seen in any of the colitides. Submucosal fat deposition is present significantly more often in ulcerative colitis (61%) than in Crohn colitis (8%).\nMural thickening of the terminal ileum may be visualized in 10-25% of patients; such thickening is caused by backwash ileitis, which occurs as a result of the reflux of colonic contents into the distal ileum. Abscesses and pseudodiverticula are not features of ulcerative colitis; they occur almost exclusively in Crohn colitis.\nDegree of confidence\nCross-sectional imaging plays a prominent role in the assessment of IBD of the colon. The clinical history, laboratory data, and extent of involvement are used in conjunction with the radiographic results to reach a specific diagnosis.\nCT is preferred to MRI for assessing the extent of inflammatory disease in and beyond the bowel wall. An added benefit of CT over MRI is the fact that patients with abscesses or large fluid collections may undergo drainage while in the CT scanner. CT and MRI may help to distinguish between cases of ulcerative colitis with minimal wall thickening and cases of Crohn disease with marked wall thickening with concomitant skip lesions and fistula and/or abscess formation. [22]\nAlthough many CT findings in ulcerative colitis are striking, they are not considered specific. Some features do suggest a diagnosis of IBD, and specific features may indicate a single diagnosis of ulcerative colitis with a high degree of confidence. The halo sign typically occurs in ulcerative colitis.\nThe utility of multidetector-row computed tomography (MDCT) in assessing the severity of ulcerative colitis (UC) in comparison with clinical assessment, colonoscopy, and histopathology has been studied. Disease severity assessment by MDCT demonstrates positive correlation with severity established by clinical assessment and colonoscopy. Only increasing wall thickness, as graded on MDCT, correlates with histopathologic disease severity. [23]\nFalse positives/negatives\nBowel thickening is a nonspecific finding; it may be encountered in a variety of colitides and other pathologies of the bowel wall. The target sign is also nonspecific; it has been reported in Crohn colitis. Mucosal ulceration is difficult to detect with CT.\nThe target sign may be secondary to a hypoattenuating submucosal layer of fluid (nonspecific) or fat (chronic in origin and usually from IBD). Also, there is evidence that submucosal fat may be a normal variant.\nMagnetic resonance cholangiopancreatography (MRCP) seems to be a reliable, noninvasive imaging method for diagnosing and following up primary sclerosing cholangitis. The rapid acquisition with relaxation enhancement (RARE) sequence has been found to have the highest diagnostic accuracy of the T2-weighted sequences.\nGiovagnoni and associates used high-resolution MRI to study 16 resected rectosigmoid specimens of patients who underwent total colectomy in treatment of severe ulcerative colitis, [24] and the findings suggested that MRI can detect changes of the colon wall in ulcerative colitis. The in vitro results showed that MRI could depict all layers of the colonic wall. In ulcerative colitis specimens, in particular, T1-weighted spin-echo MRI showed thickening and the peculiar abnormal hyperintensity of the mucosal and submucosal layers. The in vivo results confirmed the high signal intensity of the mucosal and submucosal layers.\nGadolinium-based contrast agents have been linked to the development of nephrogenic systemic fibrosis (NSF) or nephrogenic fibrosing dermopathy (NFD). NSF/NFD is a debilitating and sometimes fatal disease. Characteristics include red or dark patches on the skin; burning, itching, swelling, hardening, and tightening of the skin; yellow spots on the whites of the eyes; joint stiffness with trouble moving or straightening the arms, hands, legs, or feet; pain deep in the hip bones or ribs; and muscle weakness. [11, 9]\nThe usefulness in transmural assessment, the capability for sagittal imaging, and the lack of invasiveness are attractive features of MRI.\nIn a study by Shoenut and associates, MRI was comparable to endoscopy in differentiating ulcerative colitis from Crohn disease and in assessing the severity of disease. [25] In 17 of 18 patients, a correct diagnosis was made using gadolinium-enhanced, fat-suppressed, T1-weighted, spin-echo MRI. In 15 patients, a correct diagnosis was made on endoscopy. Overall, MRI was not significantly better than endoscopy in distinguishing ulcerative colitis from Crohn disease. MRI permitted correct grading of the severity of inflammatory changes in 13 of 20 patients; endoscopy did so in 11 cases. MRI and endoscopic findings were each found to be within one grade of the histologic findings in 7 patients. No significant difference was found between MRI and endoscopy in terms of the estimation of disease severity (as determined from biopsy samples). Assessments of bowel wall thickness on MRIs correlated well with the percentage of contrast enhancement. [25]\nCrohn disease is important in the differential diagnosis of ulcerative colitis, though it is not always possible to differentiate these 2 conditions on the basis of imaging.\nHansmann and associates evaluated the diagnostic role of hydro-MRI in 33 patients suspected of having either Crohn disease or ulcerative colitis and concluded that hydro-MRI was a reliable modality for diagnosing Crohn disease. [26] A correct diagnosis was made with MRI in all 24 patients with active Crohn disease. However, MRI results were positive in only 2 of 5 patients with ulcerative colitis. In 5 patients, IBD was excluded. No false-positive results occurred.\nExcluding infective and toxic states, Crohn disease and ulcerative colitis are the most common causes of chronic large bowel inflammation. US features are nonspecific and include bowel wall thickening, which may involve both the hypoechoic muscular coat and the echogenic mucosa. Wall thickening extends longitudinally, and there is decreased echogenicity and luminal narrowing. Localized perforation may lead to the formation of an abscess, which may be clinically silent if the patient is receiving steroid therapy.\nSeveral criteria have been described for the detection of Crohn colitis and ulcerative colitis. A water-filled colon allows better definition of the large bowel mucosa. With Crohn colitis, the whole bowel wall is thickened; all layers are involved with edema, fibrosis, inflammation, and lymphangiectasis. On US, the wall is clearly thickened, hypoechoic, and homogeneous initially, but it may become inhomogeneous because of fat deposition. The layered anatomy of the bowel wall and the haustra are lost. The bowel becomes rigid, with diminished compressibility and peristalsis. The diameter of the wall is approximately 13 mm.\nIn ulcerative colitis, the wall thickness is not as great, averaging 7.8 mm. Early disease is confined to mucosa; wall stratification is preserved, but haustra are lost. In Crohn disease and ulcerative colitis, the presence of Doppler parietal flow throughout the affected thickened segment indicates an acute condition. Similarly, an abnormally high mean portal velocity of 30-48 cm/s (normal, 15 ± 7 cm/sec) and an abnormally low resistive index of 0.58-0.78 (normal, 0.908-0.026) are detected in the superior mesenteric artery (SMA). These values, which are determined on the basis of Doppler examination, are known to revert to normal with successful therapy.\nDifferentiation between ulcerative colitis and Crohn disease is important from a management viewpoint. The latter tends to be transmural disease; the former tends to be a superficial inflammatory process of the mucosa.\nEndosonography (EUS) plays a limited role in discriminating ulcerative colitis from Crohn disease, but EUS evaluation of perirectal and perianal complications of Crohn disease has been demonstrated to be superior to fistulography and CT and equal or superior to MRI. [27, 28]\nIn a study by Bru and associates, hydrocolonic US demonstrated 100% sensitivity in identifying patients with active IBD, and it demonstrated greater overall accuracy (87%) than scintigraphy (77%) in the assessment of disease extension. In addition, a hydrocolonic US activity index was strongly correlated with clinical and endoscopic activity indexes. The authors prospectively compared the usefulness of hydrocolonic US and technetium-99m (99mTc) hexamethylpropylamine oxime (HMPAO)–labeled WBC scintigraphy in 68 patients with active IBD (34 patients had ulcerative colitis; 34 had Crohn disease), in 12 with inactive IBD, and in 10 control subjects. [29] The authors concluded that their study provided precise US criteria for the definition of bowel involvement by active IBD.\nSigirci and associates concluded in their study that duplex Doppler US of the inferior mesenteric artery (IMA) and superior mesenteric artery (SMA) may be used to evaluate inflammatory disease of the large bowel, to assess the extent of disease, and to document the response to therapy. They evaluated Doppler US blood-flow parameters and spectral patterns in the IMA and the SMA in patients with active and inactive (remission-phase) ulcerative colitis. [30, 9]\nVisualization of the upper abdomen and the bowel, in particular, is frequently compromised by the presence of gas within the bowel. To a certain extent, this may be overcome by performing US examinations in the morning, when bowel gas is at a minimum. Water may be used to distend the colon and thereby provide an acoustic window, but many people swallow air when drinking, which may cause further artifacts.\nUS measurements of bowel wall thickness offer a simple, noninvasive technique for monitoring IBD in children. Thickened and hypervascularized bowel wall are characteristic findings in cases of IBD. A combination of B-mode and power Doppler US offers an additional noninvasive procedure for the determination of activity in patients with IBD.\nMost bowel pathologies cause thickening of the bowel wall. On bowel examination, a target sign is usually seen. With this sign, a hypoechoic wall surrounds the echogenic mucosa, intraluminal mucous, air, and other bowel contents. This target may be round or oval (pseudo-kidney sign).\nUnder normal physiologic conditions, the hypoechoic bowel wall measures less than 4 mm. With few exceptions, this 4-mm rule may be applied to the whole of the bowel. Under pathologic conditions, the bowel wall thickens symmetrically in target fashion. It may be thickened asymmetrically when the echogenic lumen is displaced to one side on a true cross-section; this is the atypical target sign.\nMost bowel pathology, whether inflammatory or neoplastic, may be inferred from the aforementioned signs. As with most imaging findings, these signs are nonspecific and suggest only a differential diagnosis. US findings of mural thickening of the bowel with a paucity of luminal content may be helpful in the detection of IBDs. However, the findings are nonspecific, and the differential diagnosis must be related to the specific segment of the bowel involved.\nGallium-67 (67Ga) was once the only radionuclide used in the scanning of inflammatory bowel disease (IBD); however, leukocyte labeling has largely replaced the use of gallium because of better dosimetry and resolution and a lower radiation burden to the patient. Jones and associates performed 67Ga citrate scanning in 9 patients with ulcerative colitis, [31] and in all patients, there was good correlation between the regional uptake of gallium and the extent and activity of disease. In 2 patients, scans were positive during an acute exacerbation and reverted to normal or near normal during clinical remission. In 1 patient in whom the colon was resected because of toxic dilatation, good correlation was found between pathologic and scintigraphic results.\nDuring an acute attack of ulcerative colitis, when colonoscopy or barium enema may be contraindicated, gallium scanning may provide a noninvasive means of assessing the extent of colonic involvement. It may also be an alternative means of following the clinical course of the disease.\nWith the availability of indium-labeled WBCs, radionuclide-imaging studies have a definite role in the diagnosis and staging of IBD. The indium-111 (111In) WBC study is particularly helpful in evaluating recurrent disease in patients with severe intercurrent diseases and in screening patients, without the need for barium examinations. [32]\nIndium-111 oxine and 111In tropolone are neutral, nonpolar, lipophilic chelates that penetrate the cell membrane of leukocytes. Once inside the leukocytes, the 111In ion dissociates from the chelate and forms a relatively stable bond with cytoplasmic and nuclear proteins. There are a number of differences in the 2 chelating agents; one of the most important is that 111In oxine cannot be used to label leukocytes in the presence of plasma because of the higher affinity of 111In for transferrin than for oxine. Indium-111 tropolone is a stronger chelating agent; its use does not require the removal of plasma before cell labeling.\nBoth types of 111In label all types of blood cells indiscriminately; therefore, the leukocytes must first be separated from the other cells. The result is a mixed population of labeled leukocytes, including neutrophils, monocytes, and lymphocytes; this is acceptable for most imaging. Labeling efficiencies on the order of 80-90% may be achieved with either agent. If the labeling efficiency is less than 40%, the cells should not be reinjected.\nIndium-111–labeled leukocytes are normally distributed in the spleen, liver, and bone marrow and transiently in the lungs. The accumulation of activity at sites other than these sites is suggestive of infection or inflammation.\nWBCs may be labeled with 99mTc. Technetium-99m HMPAO is a neutral, nonpolar, lipophilic agent that was originally developed for cerebral perfusion imaging (see the image below). The compound is unstable and breaks down into a hydrophilic secondary complex. In its lipophilic form, 99mTc HMPAO can cross the cell membrane of leukocytes. Once within the cell, its structure is altered to the hydrophilic form, and 99mTc is trapped inside. [12]\nTechnetium-99m HMPAO leukocyte labeling may be performed in the presence of plasma and appears to have significant selectivity for granulocytes. As with 111In-labeled leukocytes, 99mTc-labeled leukocytes are localized in the spleen, liver, and bone marrow and transiently in the lungs.\nFalse-positive diagnosis of bowel inflammation is possible with 99mTc-labeled leukocytes. In adults, normal localization occurs in the bowel about 3-4 hours after administration; in children, normal localization occurs earlier. This localization is associated with sloughing of leukocytes into the lumen of the GI tract. In addition, activity is seen in the urinary tract and occasionally within the gallbladder. Fasting for 2-4 hours before imaging may reduce hepatobiliary excretion and subsequent bowel activity, especially in children. The 1-hour images demonstrate lung activity but no activity in the GI system.\nFluorodeoxyglucose positron tomography has been used in the diagnosis of pediatric IBD. This technique appears to provide adequate information for patients suspected of having IBD. [33]\nRadionuclide-labeled WBC scanning using 111In is an accurate, quantitative, and noninvasive method for assessing the degree of bowel inflammation in cases of IBD; it is also useful in assessing response to therapy. Fecal collection or total body counts of radioactivity may be used.\nThe use of 99mTc HMPAO WBC scanning has several advantages over the111 In scanning, including a reduction in the radiation dose and better image resolution. The 99mTc HMPAO WBC technique may be used in combination with single-photon emission CT (SPECT), which allows visualization of the entire bowel as distinct from overlying structures. Tc-99m HMPAO WBC SPECT permits measurement of segmental and total bowel uptake. [34]\nTechnetium-99m HMPAO-labeled leukocyte scintigraphy has been found to correlate well with colonoscopy in the assessment of both the extension and severity of ulcerative colitis. Use of 2-hour scintigraphic imaging decreases the number of false-positive results. [35]\nTolia and associates compared 111In-labeled WBC scanning and colonoscopy in 19 children and adolescents with chronic IBD; they compared the degree to which the 2 diagnostic modalities correlated with histologic diagnosis. [36] The data suggested that the usefulness of scans is limited to patients in whom standard diagnostic procedures are contraindicated. The sensitivity of 111In scanning was 18%, its specificity was 62.5%, and its accuracy for colonic disease was only 37%. In comparison, the sensitivity and specificity of colonoscopy were 100% and 57%, respectively; its accuracy was 84%.\nIn-111-labeled WBCs accumulate nonspecifically at sites of inflammation or infection. The differential diagnosis for accumulation of 111In-labeled WBCs involving the abdomen most commonly includes Crohn disease, ulcerative colitis, diverticulitis, ischemic or infarcted bowel, phlegmon, and wound infection.\nFactors that may lead to false-positive results include the swallowing of leukocytes, the use of enteric tubes, and the presence of a GI bleed. False-positive results may also occur as a result of the physiologic uptake of 99mTc-labeled WBCs; biliary and urinary excretion; and delayed normal bowel excretion.\nAngiography is a valuable tool in the diagnosis and therapy of hemorrhage from the large bowel resulting from ulcerative colitis and other causes. [37]\nTsuchiya and associates performed selective superior and inferior mesenteric angiography in 25 patients with ulcerative colitis. [38] Vascular changes in large vessels, such as increased diameter of the IMA, were found to correlate better with the severity or activity of illness. However, in some cases, microcirculatory changes of small vessels of the intestinal wall (eg, capillary blush or loss of normal tapering of vasa recta) remained in remission of this disease.\nBrahme and Hildell evaluated the diagnostic yield of angiography in 116 patients with Crohn disease [39] and concluded that angiography was a diagnostic adjunct to barium studies and that it revealed the presence of lesions, as well as their extent. Angiographic abnormalities were found in over 90%. Crohn disease could be distinguished from ulcerative colitis in only 30% of the cases.\nAngiographic findings are nonspecific; both false-positive and false-negative results may occur.\nWhat is ulcerative colitis (UC)?\nWhat is the role of imaging studies in the diagnosis of ulcerative colitis (UC)?\nHow is ulcerative colitis (UC) graded?\nWhat are the limitations of imaging in the diagnosis of ulcerative colitis (UC)?\nWhich findings on plain radiographs are characteristic of ulcerative colitis (UC)?\nWhich barium enema findings are characteristic of ulcerative colitis (UC)?\nWhich CT findings are characteristic of ulcerative colitis (UC)?\nWhat is the role of CT scanning in the workup of ulcerative colitis (UC)?\nWhich nonspecific findings may affect the accuracy of CT in the diagnosis of ulcerative colitis (UC)?\nWhat is the role of MRI in the diagnosis of ulcerative colitis (UC)?\nWhat is the accuracy of MRI in the diagnosis of ulcerative colitis (UC)?\nHow is Crohn disease differentiated from ulcerative colitis (UC) on imaging?\nWhat is the role of ultrasonography in the diagnosis of ulcerative colitis (UC)?\nWhat are the limitations of ultrasonography in the diagnosis of ulcerative colitis (UC)?\nWhich findings on ultrasonography are characteristic of ulcerative colitis (UC)?\nWhat is the role of nuclear imaging in the workup of ulcerative colitis (UC)?\nWhat is the accuracy of nuclear imaging in ulcerative colitis (UC)?\nWhat causes false-positive nuclear imaging results in ulcerative colitis (UC)?\nWhat is the role of angiography in the diagnosis of ulcerative colitis (UC)?\nGarcía Gavilán MDC, López Vega MC, Sánchez IM. Ulcerative colitis with gastric and duodenal involvement. Rev Esp Enferm Dig. 2017 Jul. 109 (7):535-536. [Medline].\nAmerican Gastroenterological Association. Mild-to-Moderate Ulcerative Colitis (UC) Clinical Decision Support Tool. Gastroenterology. 2019 Feb. 156 (3):765. [Medline]. [Full Text].\n[Guideline] American Gastroenterological Association. New guideline provides recommendations for the treatment of mild-to-moderate ulcerative colitis. AGA. Available at https://www.gastrojournal.org/article/S0016-5085(18)35407-6/fulltext. January 9, 2019; Accessed: February 23, 2019.\nMurthy SK, Shukla T, Antonova L, Belair MA, Ramsay T, Gallinger Z, et al. Predictive models of disease burden at diagnosis in persons with adult-onset ulcerative colitis using health administrative data. BMC Gastroenterol. 2019 Jan 21. 19 (1):13. [Medline].\n[Guideline] American College of Gastroenterology. Ulcerative Colitis Clinical Practice Guidelines. Medscape. 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Review article: quantitative leucocyte scanning in the assessment of inflammatory bowel disease activity and its response to therapy. Aliment Pharmacol Ther. 1996 Apr. 10(2):123-32. [Medline].\nAydin F, Dinçer D, Güngör F, Boz A, Akça S, Yildiz A, et al. Technetium-99m hexamethyl propylene amine oxime-labeled leukocyte scintigraphy at three different times in active ulcerative colitis: comparison with colonoscopy and clinico-biochemical parameters in the assessment of disease extension and severity. Ann Nucl Med. 2008 Jun. 22(5):371-377. [Medline].\nTolia V, Kuhns LR, Chang CH. Comparison of indium-111 scintigraphy and colonoscopy with histologic study in children for evaluation of colonic chronic inflammatory bowel disease. J Pediatr Gastroenterol Nutr. 1991 Apr. 12(3):336-9. [Medline].\nBaum S, Athanasoulis CA, Waltman AC. Angiography in the diagnosis and therapy of hemorrhage from the large bowel. Radiologe. 1975 Nov. 15(11):427-33. [Medline].\nTsuchiya M, Miura S, Asakura H. 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[Medline].\nA 22-year-old man presented with abdominal pain, passage of blood and mucus per rectum, abdominal distention, fever, and disorientation. Findings from sigmoidoscopy confirmed ulcerative colitis. Abdominal radiographs obtained 2 days apart show mucosal edema and worsening of the distention in the transverse colon. The patient's clinical condition deteriorated over the next 36 hours despite steroid and antibiotic therapy, and the patient had to undergo total colectomy and ileostomy.\nIntravenous urogram shows features of ankylosing spondylitis.\nAli Nawaz Khan, MBBS, FRCS, FRCP, FRCR Consultant Radiologist and Honorary Professor, North Manchester General Hospital Pennine Acute NHS Trust, UK\nAli Nawaz Khan, MBBS, FRCS, FRCP, FRCR is a member of the following medical societies: American Association for the Advancement of Science, American Institute of Ultrasound in Medicine, British Medical Association, Royal College of Physicians and Surgeons of the United States, British Society of Interventional Radiology, Royal College of Physicians, Royal College of Radiologists, Royal College of Surgeons of England\nAali J Sheen, MD, MBChB, FRCS Consulting Hepatobiliary Surgeon, HepatoBiliary Unit, Manchester Royal Infirmary, UK\nAali J Sheen, MD, MBChB, FRCS is a member of the following medical societies: British Medical Association, International Hepato-Pancreato-Biliary Association, Royal College of Surgeons of England\nHaren Varia, MB, ChB, FRCR Consultant, Department of Clinical Radiology, Blackpool, Fylde and Wyre NHS Trust, UK\nDavid Andrew Nicholson, MBBS, FRCR Honorary Lecturer, Department of Radiology, University of Manchester Medical School; Consultant Gastrointestinal Radiologist, Department of Radiology, Hope Hospital, Salford Royal Hospital NHS Trust, UK\nEugene C Lin, MD Attending Radiologist, Teaching Coordinator for Cardiac Imaging, Radiology Residency Program, Virginia Mason Medical Center; Clinical Assistant Professor of Radiology, University of Washington School of Medicine\nEugene C Lin, MD is a member of the following medical societies: American College of Nuclear Medicine, American College of Radiology, Radiological Society of North America, Society of Nuclear Medicine and Molecular Imaging\nThe authors and editors of Medscape Reference gratefully acknowledge the contributions of previous author Sumaira MacDonald, MBChB, PhD, MRCP, FRCR,to the development and writing of this article.\nencoded search term (Ulcerative Colitis Imaging) and Ulcerative Colitis Imaging\nUlcerative Colitis in Children\nSurgical Treatment of Ulcerative Colitis\nFast Five Quiz: How Much Do You Know About Ulcerative Colitis?\nFast Five Quiz: Can You Properly Identify Ulcerative Colitis and Initiate Best Treatment?\nEpithelial Response to Butyrate Diminished in Active IBD\nAnti-TNF Agents Linked to Increased Risk of IBD\nHidradenitis Suppurativa Tied to Inflammatory Bowel Disease Risk\nInflammatory Bowel Disease: 10 Cases to Test Your Dx/Rx Skills\nDiseases & Conditions Ulcerative Colitis\nDiseases & Conditions Ulcerative Colitis in Children\nNews Inflammatory Bowel Disease Patients Have Higher Health Costs"