Multimodality approach for imaging of non-traumatic acute abdominal emergencies

Kiran Gangadhar,1 Ania Kielar,2 Manjiri K. Dighe,1 Ryan O’Malley,1 Carolyn Wang,1

Joel A. Gross,1 Malak Itani,1 Neeraj Lalwani 1

1Department of Radiology, University of Washington, Seattle, WA 98105, USA2Department of Radiology, University of Ottawa, Ottawa, ON K1H 8L6, Canada

Abstract

‘‘Acute abdomen’’ includes spectrum of medical andsurgical conditions ranging from a less severe to life-threatening conditions in a patient presenting with severeabdominal pain that develops over a period of hours.Accurate and rapid diagnosis of these conditions helps inreducing related complications. Clinical assessment isoften difficult due to availability of over-the-counteranalgesics, leading to less specific physical findings. Thekey clinical decision is to determine whether surgicalintervention is required. Laboratory and conventionalradiographic findings are often non-specific. Thus, cross-sectional imaging plays a pivotal role for helping directmanagement of acute abdomen. Computed tomographyis the primary imaging modality used for these cases dueto fast image acquisition, although US is more specificfor conditions such as acute cholecystitis. Magnetic res-onance imaging or ultrasound is very helpful in patientswho are particularly sensitive to radiation exposure, suchas pregnant women and pediatric patients. In addition,MRI is an excellent problem-solving modality in certainconditions such as assessment for choledocholithiasis inpatients with right upper quadrant pain. In this review,we discuss a multimodality approach for the usual causesof non-traumatic acute abdomen including acuteappendicitis, diverticulitis, cholecystitis, and small bowelobstruction. A brief review of other relatively less fre-quent but important causes of acute abdomen, such asperforated viscus and bowel ischemia, is also included.

Key words: Acute abdomen—ACR appropriatenesscriteria—Acute appendicitis—Diverticulitis—Cholecystitis—Small bowel obstruction—Imaging—MRI—CT—Ultrasound

Of all patients who present to the emergency depart-ment (ED), 4–5% of the patients are symptomatic foracute abdominal pain [1]. There is a wide spectrum ofmedical and surgical conditions that can present withacute abdominal pain. The clinical outcome depends ona variety of factors based on the diagnosis, severity ofthe disease, and management. Abdominal pain can becategorized as visceral, somatoparietal, or referred pain.These types of pain can be a manifestation of a widespectrum of systemic and local causes. Acute appen-dicitis, diverticulitis, cholecystitis, and bowel obstruc-tion are ‘the usual suspects’ of acute abdominal pain.Other important but less frequent conditions that maycause acute abdominal pain include perforated viscusand bowel ischemia. One of the key decisions is todetermine whether surgical intervention is necessary.Imaging plays a major role in diagnosing these condi-tions as well as identifying associated complications.Imaging is also necessary for follow-up of complicationssuch as abscesses and in some cases image to guideinterventions. Abdominal radiographs are the mostcommon initial imaging modality of choice to grosslyrule out pneumoperitoneum and give an overview of thedegree of bowel wall distension and in some cases, thepresence of bowel wall thickening. US and CT havetraditionally been the most commonly used cross-sec-tional imaging modalities for evaluating acute abdomi-nal conditions. The high cost, limited availability, longexamination duration, and increased frequency of arti-facts have been major limitations of MRI use in emer-gency settings.

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Correspondence to: Neeraj Lalwani; email: neerajl@uw.edu

ª Springer Science+Business Media New York 2015

Published online: 22 December 2015AbdominalRadiology

Abdom Radiol (2016) 41:136–148

DOI: 10.1007/s00261-015-0586-6

Imaging modalities to evaluate acuteabdominal emergencies and ACRappropriateness recommendations

Plain radiograph

The imaging workup of patients with acute abdominalpain often starts with radiographs including, supine andupright abdominal radiographs, and upright chest radio-graph [2–4]. A left lateral decubitus may replace the up-right abdomen if the patient is severely ill and cannot bepositioned upright. TheACRappropriateness criteria rateabdominal radiographs as a 5 out of 9, below CT andultrasound, though they provide a caveat of utility to as-sess for bowel perforation. Over-utilization of radio-graphic investigations causes significant financial wastageto both patients and the health care provider [5–7]. A fewstudies in the literature have concluded that a small bowelobstruction (SBO) can be diagnosed with equal sensitivityon a supine abdominal radiograph alone and routine useof the erect abdominal radiograph in the acute abdomenshould be abandoned [8] because bowel loops are more orless at their anatomical position. However, it remainscontroversial and most institutions still obtain the uprightradiograph. A lateral chest radiograph has also been rec-ommended by Woodring et al. to achieve a higher diag-nostic accuracy in detecting free intraperitoneal air thanwith a posterior-anterior chest radiograph [9].

Some studies have advocated plain abdominal radio-graphs for investigation of acute abdominal pain whenrelated to suspected intestinal obstruction, urinary tractcalculi, or a perforated viscus [10]. However, other studies[11] have concluded that the clinical diagnosis after evalu-ation of plain radiographs did not change significantlyfrom the primary diagnosis based on clinical evaluationalone, except in the case of bowel obstruction [11]. In aprospective study Boleslawski et al. [12], only 6% of casesresulted in a change in the suspected diagnosis or thera-peutic management based on plain radiograph appear-ances inpatients presentingwith right lower quadrantpain.

Ultrasound

US is inexpensive, widely available, and one of the com-mon initial modalities of choice for evaluation ofabdominal pain in the ED. The lack of ionizing radiationand real-time imaging are the most important advantagesofUS.Another important advantage ofUS examination isthe possibility to correlate the US findings with the pa-tient’s point ofmaximal tenderness. Themost commonUStechnique used in patientswith acute abdominal pain is thegraded-compression ultrasound technique helping to dis-place bowel loops to achieve better images [13]. Identifi-cation of a non-compressible bowel loop in itself is anindication of abnormalities including appendicitis, intus-susception, malignancy, or luminal distension resulting

from obstruction. Another example of dynamic exami-nation is the evaluation of bowel hernias using Valsalvamaneuvers. This maneuver may reveal an intermittenthernia [14]. US is also useful in evaluating transientintussusception because of its real-time capabilities [15].

Sonography is the imaging modality of choice toevaluate hepatobiliary pathologies and has been assignedan ACR appropriateness score of 9/10 in patients withRUQ pain [16]. It is a useful modality for image-guidedprocedures such as abscess drainage and cholecys-tostomy tube placement, as well as biopsy guidance.

Additionally, ultrasound is also useful in evaluatingpelvic organs, gynecological, and renal pathologies [17].

The major disadvantages of ultrasound are operatordependence, including inter-observer variability, andlack of tissue penetration in obese patients.

In a study by Lameris et al., using sonography as theprimary imaging modality, regardless of the body mass in-dex, age, or location of pain, followed byCT only in cases ofnegative or indeterminate sonographic findings, resulted inthe highest sensitivity for acute abdominal and pelvic con-ditions while reducing exposure to ionizing radiation [18].

CT

The utility of CT in the diagnosis and management ofacute abdominal emergencies is well established. CTprovides greater accuracy than ultrasonography or plainradiography for identifying pneumoperitoneum, as wellas evaluation of bowel pathology, retroperitoneal andbony abnormalities. It has high sensitivity and specificityfor evaluating most common emergent pathologies suchas acute appendicitis and diverticulitis. Traditionally, thetypically described protocol for evaluating an acute ab-domen was to administer both positive oral and IVcontrast media and scan using a standard radiation doseCT technique. However, using oral contrast slows downpatient throughput and may negatively impact patientmanagement in the case of a surgical abdomen. More-over, the presence of oral contrast helps radiologists insome aspects but it has not been shown to increaseaccuracy [19]. Overall, use of oral contrast should bediscouraged in the evaluation of acute abdomen [20, 21].

CT is the most often used imaging modality in pa-tients with right lower quadrant (RLQ) pain with ACRappropriates score of 8/10 (usually appropriate) for CTabdomen and pelvis with IV contrast and 7/10 (usuallyappropriate) for CT abdomen and pelvis without IVcontrast [22]. IV contrast and modified (increased) rateof contrast administration may be necessary for evalu-ating acute vascular conditions like hemorrhage, bowelischemia, renal infarct etc.

The major disadvantages of CT are exposure to radi-ation and contrast media as well as being far moreexpensive than ultrasound. There are new strategies toreduce radiation exposure which include the use of itera-

K. Gangadhar et al.: Multimodality approach for imaging abdominal emergencies 137

tive reconstruction algorithms such as ‘iDose,’ ‘100%ASIR’ (adaptive statistical iterative reconstruction), and‘IRIS’ (iterative reconstruction in image space). The 100%ASIR algorithm has been demonstrated to reduce noiseby 47% while a newer algorithm called Veo (GeneralElectric Healthcare, Milwaukee, Wisconsin, USA) de-creases the image noise up to 70% when compared withthe gold standard filtered back projection model [23].

MRI

MRI may be on the way to becoming a potential alterna-tive for the evaluation of acute abdominopelvic pain. Re-cent advances in MRI have allowed the development ofrapid imaging sequences that are particularly suited for EDindications [24]. There are special circumstances whereinMRI is currently indicated [25]. For example, in pregnantpatients who have symptoms of appendicitis, MRI hasproven to have high sensitivity and specificity [26]. MRIalso can be used to evaluate equivocal CT findings in pa-tients with hepatobiliary pathologies, particularly MRCPfor choledocholithiasis and to monitor previously diag-nosed acute gastrointestinal disease, especially in youngpatients, in whom radiation exposure is of concern [27].MR imaging has also demonstrated utility in detection ofacute inflammatory diseases of the pancreas, kidneys,collecting system, bowel, and pelvic soft tissues [28].

Basic MR imaging protocols for emergent evaluationof the abdomen and pelvis include the following se-quences: axial breath-hold in-phase and out-of-phase T1-weighted GRE, axial and coronal breath-hold T2-weighted single-shot turbo SE, axial T2-weighted fat-suppressed turbo SE with respiratory triggering (or shortinversion time inversion recovery), and steady-state freeprecession. Thick-slab MRCP, respiratory-triggered T2-weighted turbo SE, and volumetric T1-weighted post-contrast sequences are added as necessitated by theclinical indication and with consideration of patient’sability to tolerate breath-hold acquisitions. Of note,gadolinium is considered a class C medication in preg-nancy and is therefore only used in circumstances wherematernal and fetal health would be in jeopardy and thereis no other suitable imaging alternatives available (26).The duration of the MR imaging examination is typically20–30 min, still substantially longer than CT.

The disadvantages of MRI in emergent settings in-clude the relatively longer acquisition times, limitedavailability, the presence of artifacts and to some degree,the high cost.

In patients with RUQ pain without fever and with anormal white count showing only gallstones on ultra-sound, the ACR appropriateness criteria rating for use ofMRI is only 6/10 (may be appropriate) [16]. In patientswith RLQ pain with fever and with high white count aswell as in pregnant women, the ACR appropriatenesscriteria rating is 7/10 (usually appropriate) [22].

Acute appendicitis

Appendicitis is the most common acute abdominalemergency requiring surgery in both adults and pediatricpopulations with an incidence of about 250,000 casesreported in the United States each year [29]. The diag-nosis depends mainly on clinical presentation; however,nearly half of the patients have negative or atypicalclinical presentation [30].

There is a correlation between duration of symptomsand risk of perforation of appendicitis. An overall per-foration rate of 16–39% has been reported in the litera-ture [31] which can lead to several potentially life-threatening complications such as intrabdominal abscess,peritonitis, and sepsis [32].

The false-negative appendectomy rates range from13% to 30% when imaging is not used but has been ashigh as 15–47% in female patients aged 10–39 years [33].

The important clinical symptoms include tendernessat Mcburney’s point, migratory abdominal pain, andfever. Physical examination demonstrates non-specificpositive signs of appendicitis, such as rebound tender-ness, Rovsing’s, obturator, and psoas sign. An increasein the C-reactive protein (CRP) correlates with theseverity of the disease and is a possible surrogateparameter for perforation. Leukocytosis is more sensitivefor the detection of early-stage appendicitis [34].

Imaging algorithm varies depending on patient’sdemography and institutional policies. In general, ultra-sound remains modality of choice for screening purpose,when radiation exposure remains a concern (pregnant orpediatric patient). MR can be performed next to ultra-sound if non-diagnostic. Otherwise, CT is a widely ac-cepted modality of choice to evaluate appendicitis ingeneral population.

Graded compression technique is used in sonographicevaluation of right lower quadrant pain. US maydemonstrate an enlarged, non-compressible appendix,more than 6 mm in diameter. Other ancillary findingsinclude the presence of an appendicolith, a fluid-filledappendix, pericecal fluid, inflammation of surroundingfat, and the presence of a frank abscess.

Pertinent imaging findings on CT are in many re-spects similar to sonographic findings and may include;increased transverse diameter of the appendix >6 mm,increased thickness of the appendiceal wall >2 mm,appendiceal wall hyperenhancement, the presence orabsence of a focal defect in the appendiceal wall, thepresence of an appendicolith/fecalith, periappendicealchanges, cecal wall thickening, and right lower quadrantfree fluid (Fig. 1A). The presence of oral contrast andintraluminar continuous column of air are negativefindings for appendicitis [35]. The CT findings of focaldefects in the appendicular wall, periappendicular ab-scess, larger appendicular diameter (>15 mm), terminalileal thickening, ileus and extraluminal free air or extra-

138 K. Gangadhar et al.: Multimodality approach for imaging abdominal emergencies

luminal appendicolith are helpful in differentiating earlyperforated appendicitis from non-perforated appendicitis(Fig. 1B). The presence of extraluminal gas, abscess, andileus were more specific for perforation. A transversediameter of the appendix greater than 11 mm has thehighest sensitivity (62.7%) while a focal wall defect hasthe highest specificity (98.8%) [36]. Although sonographyis recommended in young patients as the first imagingmodality, some studies also advocate low dose CT forappendicitis in young patients after equivocal findings onultrasound [37].

MR imaging is indicated in pregnant patients withsymptoms of RLQ pain. MR imaging has high reportedsensitivity (97–100%) and specificity (92–93%) for thediagnosis of acute appendicitis during pregnancy [38]. T2turbo spin-echo sequences are particularly helpful foridentifying the location of the appendix. Edema andinflammation appear as T2 signal hyperintensity withinthe wall or surrounding the appendix; fat-suppressedsingle-shot sequences are useful for depicting these fea-tures (Fig. 2). Post-contrast MR sequences may behelpful in diagnosing appendicitis in children byincreasing the tissue contrast [39].

Differential diagnosis for acute appendicitis may in-clude mucocele, mesenteric adenitis, and terminal ileitis(Fig. 3). Mucocele is defined as dilated appendix(>1.3 cm) with intraluminal accumulation of abnormalmucus. Symptoms for complicated mucoceles can mimicthose of acute appendicitis [40]. Underlying cause of amucocele could be a neoplasm (benign or malignant) andit may be associated with a superimposed appendicitis.Mural calcification can be seen. Mesenteric adenitis is aself-limiting inflammatory process involving mesentericlymph nodes. On imaging, it can be diagnosed by findingthree or more lymph nodes measuring at least 5 mm in

short axis in the right lower quadrant or pericecal region[41]. Terminal ileitis represents inflammation of terminalileum due to variegated etiologies, which could be aninflammatory bowel disease or infections.

Acute diverticulitis

Diverticulosis occurs in 5–10% of people >45 years oldand the condition progressively increases in incidencewith advancing age. It has been reported to be found inup to 80 % of people >85 years old. Acute diverticulitisis inflammation of the colonic diverticulum which couldbe uncomplicated (localized inflammation) or compli-

Fig. 2. Coronal T2w fat-suppressed MR image through rightlower quadrant shows dilated appendix (arrow). There is in-creased T2w signal intensity surrounding the appendix (arrowheads) suggestive of inflammation; (Fetus: f).

Fig. 1. A Coronal CECT of the abdomen and pelvis showingincreased transverse diameter of the appendix (double ar-rows), increased mural thickness and mural hyperenhance-

ment and periappendiceal inflammatory changes (asterix); BExtraluminal air along with features of inflammation consistentwith perforated appendicitis.

K. Gangadhar et al.: Multimodality approach for imaging abdominal emergencies 139

cated (associated with an abscess, phlegmon, fistula,obstruction, bleeding, or perforation).

Patients often present with acute left lower quadrantpain and tenderness on clinical examination. Other pos-sible symptoms include anorexia, constipation, nausea,diarrhea, and dysuria. Tachycardia and hypotension mayoccur and should raise suspicion for complicated diver-ticulitis [42].

Using a graded compression technique, ultrasoundimages of diverticulitis include thickening of the wall ofthe colon, which is surrounded by hyperechoic inflam-matory fat with probe tenderness. Sometimes an in-flamed diverticulum can be visible with intraluminalcoproliths. Abscess and developing phlegmon can also bevisible on US which helps image-guided procedures [43].

Contrast-enhanced CT (CECT) depicts early stages ofdiverticulitis and has become the optimal method forevaluation of diverticular disease in the emergency set-ting, with reported accuracy of 80–100% using helicalCECT [44]. Acute diverticulitis is graded by using mod-ified Hinchey classification [45] and the correspondingradiological findings are listed in Table 1 as described byKaiser et al. [46].

The presence of free air, abscess formation, and a‘‘target pattern’’ of contrast enhancement on CT have allbeen proposed to support the diagnosis of diverticulitisbut with low specificity [47]. A differential diagnosis toconsider includes a locally advanced perforated coloniccancer (Table 2) (Fig. 4).

Buckelyet al. [48] reported that it is easier todifferentiatediverticulitis from cancer on MRI than CT due to the factthatMRI exhibits better contrast resolution which helps inappreciating thickened inflamed bowel and features typical

Fig. 3. Differential diagnosis for acute appendicitis. A Cor-onal CECT of the abdomen and pelvis showing mesentericlymphadenitis (circle); B Axial CT showing dilated appendixwith low attenuation intraluminal content (double arrow) con-

sistent with mucocele; C Thickening and mucosal enhance-ment in the terminal ileum consistent with terminal ileitis(double arrows).

Table 1. Hinchey classification for acute diverticulitis

Modified Hincheyclassification

Severity Accompanying CT findings

Stage 0 Clinically mild diverticulitis Diverticula with or without wall thickening of the colonStage Ia Confined pericolic inflammation and

phlegmonous inflammationColonic wall thickening and surrounding

inflammatory changesStage Ib Abscess formation (<5 cm) in the proximity of the

primary inflammatory processAlterations as stage Ia + pericolic or mesocolic

abscess formationStage II Intra-abdominal abscess, pelvic or retroperitoneal

abscess, abscess distant from theprimary inflammatory process

Alteration as stage Ia + distant abscess formation(mostly pelvic or interloop abscesses)

Stage III Generalized purulent peritonitis Free air with local or generalized free fluid and possiblethickening of the peritoneum

Stage IV Fecal peritonitis Similar findings to stage III

Table 2. Differentiating diverticulitis and colonic cancer

Features Diverticultis Sigmoid cancer

Focal thickening withabrupt transitionbetween normalcolon and thickenedcolon

Usually negative Usually positive

Presence of free air Usually positive Usually negative(masscould perforate)

Abscess Usually positive Usually negativeSpecific target pattern

of enhancementPositive Usually negative

Presence of diverticula Usually seen May not be seen

140 K. Gangadhar et al.: Multimodality approach for imaging abdominal emergencies

for cancer as focal thickening with abrupt transition be-tween normal colon and thickened colon. Another study byOistamo et al. also suggested the usefulness of MRI to im-prove the differentiation between sigmoid cancer anddiverticulitis [49], however, larger studies are needed toestablish the clinical utility of MRI in these issues.

Differential diagnosis for diverticulitis may includeepiploeic appendangitis and mesenteric infarction(Fig. 5). Epiploeic appendangitis is usually seen in theleft lower quadrant or flank in adult population andmeasures less than 5 cm. On imaging, they appear as

well-circumscribed fatty lesion with a ‘‘central dot’’(which represents partially thrombosis vessel). Mesen-teric infarcts usually involve right lower quadrant orflank (because of meager blood supply at the peripheryof right mesentery) measures more than 5 cm.

Acute small bowel obstruction

SBO is either mechanical or functional and precludesnormal transit of its contents. It represents 20% of allsurgical admissions for acute abdominal pain [50]. Pa-

Fig. 4. A Colonic cancer: Axial CECT of the abdomen andpelvis showing circumferential mural thickening (double ar-rows) compromising the lumen (arrow head). See the peri-colonic inflammation (asterix) is much lesser than the muralthickening. B Diverticulitis: Axial CECT of the abdomen and

pelvis showing eccentric colonic wall thickening (double ar-rows) and surrounding inflammatory changes (asterix) with afocus of extraluminal air (curved arrow) representing localizedperforation. Note the lumen is patent despite overlying thick-ening (arrow head) numerous engorged peri-colonic vessels.

Fig. 5. Differential diagnosis for diverticulitis. A Axial CECTof the abdomen and pelvis showing inflamed well circum-scribed rounded lesion (circle) next to sigmoid colon (arrowhead) showing an enhancing ‘‘central dot’’(arrow) consistent

with epiploic appendangitis; B Axial CECT of the abdomenand pelvis showing focal area of fat stranding (circle) andhyperdense peripheral halo consistent with mesentericinfarction.

K. Gangadhar et al.: Multimodality approach for imaging abdominal emergencies 141

tients present with abdominal pain, distension, nausea,and vomiting. On clinical examination, mild to moderatedehydration, tachycardia, abdominal distension which istympanic to percussion, and high-pitched bowel soundsare identified [51].

70% of all mechanical SBO are due to postoperativeadhesions [52]. Other common causes of mechanical SBOinclude hernias, neoplasms, and inflammatory bowel dis-ease. The important clinical decision is whether emergentlaparotomy is required or if a conservative approach issufficient [53]: imaging helps in making these decisions.

Useful radiographic signs include a distended stomachand bowel loops (>3 cm), multiple differential air–fluidlevels, a ‘step ladder’ pattern of dilated bowel loops, a‘String-of-beads’ sign corresponding to airbubbles trappedin valvulae conniventes, the ‘stretch sign’ or ‘slit sign’ inwhich a slit of air is caught in a valvulae, the absence of ordisproportionately smaller amount of gas in the recto-sig-moid and increased small bowel to colon ratio. In partic-ular, two findings derived from the upright abdominalradiograph were found to be the most significant andmostpredictive of the higher grades of small bowel obstruction:the presence of differential air–fluid levels (>3 in numberand air-fluid levels of>1 cm height) and a mean width ofair–fluid levels measuring greater than or equal to 25 mm[54]. Other findings suggesting strangulation or ischemiainclude pneumatosis and portal venous gas.

Fluoroscopic small bowel follow-through examina-tions have a limited role in diagnosing the cause of SBObut may be useful in determining the severity ofobstruction [55]. The role of water-soluble high osmolariodine agents has been assessed recently with regard toboth diagnostic and therapeutic; proposed mechanismsare high osmolality (approximately six times more thanextracellular fluid), which promotes shifting of fluids intothe bowel lumen and increases the pressure gradientacross obstructive sites and also facilitating its passage byreducing edema of the intestine wall.

Contrary to barium, water-soluble oral contrastagents are safe even if intestinal perforation and peri-toneal spread occurs [56].

Ultrasound has limitations for complete assessmentof the bowel due to poor visualization of gas-filledstructures. Sonographic appearance of bowel obstructionincludes dilated bowel loops, and hyperperistalsis. Thepresence of aperistaltic loops, fluid-filled, and distendedbowel, as well as wall thickening could represent infarc-tion in the relevant clinical context. Sonography has beenreported to have a sensitivity of 89% compared with 71%for conventional abdominal radiography in diagnosingsmall bowel obstruction and is superior to radiographs inits ability to identify features of strangulation and topredict the location and cause of obstruction [57].

CT is the modality of choice for evaluating suspectedSBO. It can reveal the degree, location, and cause ofobstruction as well as display signs of threatened bowelviability. CT has a sensitivity of 81–94% and a specificityof 96% for diagnosing high-grade obstructions. How-ever, there is a decrease in accuracy for diagnosing lowgrade and subacute obstructions (sensitivity of 64% andspecificity of 79%) [52]. IV contrast is ideally recom-mended while assessing SBO on CT, whereas oral con-trast can be considered based on patient tolerability. Oralcontrast should not be used if there is a request to assessenhancement/viability of the bowel wall. The diagnosisof SBO is made on the basis of dilated bowel loops>3 cm in diameter with discrete transition point [51].Passage of oral contrast material through the transitionzone into the distal bowel indicates partial or incompletebowel obstruction. ‘‘Small bowel feces sign’’ is often seencloser to anticipated transition point and suggestive ofslow transit (Fig. 6A). The CT diagnosis of adhesions isa diagnosis of exclusion as adhesions are often difficult tovisualize, however secondary findings such as acuteangulation and smooth extrinsic compressions couldindicate adhesions and are important signs for radiolo-

Fig. 6. Axial CECT of the abdomen and pelvis showingsmall bowel obstruction due to adhesions. A Small bowelfeces sign (small arrow) is usually seen closer to the transition

point; B The adhesions are not usually seen on imaging butcan be identified by acute angulation (arrows) and extrinsiccompression near the transition point.

142 K. Gangadhar et al.: Multimodality approach for imaging abdominal emergencies

gists to be familiar with (Fig. 6B). In general, imagingsigns of high-grade obstruction, an abnormal vascularcourse, and the presence of a transition zone are usefulpredictors of a surgical intervention. However, a smallbowel feces sign inversely predicts need for surgery.Differentiating congenital bands from adhesions ischallenging but evaluation of thickness as well as thepresence of single (bands) versus multiple matted adhe-sions could be useful observations [58]. Delabrousse et al.[59] showed a higher prevalence of the ‘‘beak sign’’ inpatients with bands than in patients with matted adhe-sions, and the double beak sign has been reported incases of closed loop (two points along the course of abowel are obstructed at a single location) obstruction dueto hernias including internal hernias and volvulus [60].Hence, identification of more than one beak sign couldrepresent a high risk for failure of non-surgical treatment[61]. CT is an excellent modality for detecting herniasand their associated complications such as strangulation,volvulus, and ischemia. At the site of obstruction, theremay be a whirl sign, a beak sign, or triangular configu-ration of adjacent collapsed loops (Fig. 7).

MR imaging also has been shown to be useful fordetecting bowel obstructions in acute settings and dif-ferentiating malignant from benign causes. MR is usefulin evaluating low-grade small bowel obstruction whichoccurs most commonly due to adhesions. In some cases,

low-signal-intensity soft-tissue bands may be seencoursing through high-signal-intensity mesenteric fat onT2-weighted images. MR/CT enteroclysis provides im-proved distention of the small bowel and may demon-strate subtle transition points or an obstruction that maynot be visible at imaging with more routine methods,including MR/CT enterography [62]. However, MR/CTenteroclysis are rarely needed.

Acute cholecystitis

Acute cholecystitis is the most common inflammatoryprocess of the biliary tree and accounts for 5% of EDvisits for acute abdominal pain [63]. The inflammatoryprocess may be calculous or acalculous in origin, mostcommonly calculous with only 5–10% of all cases ofcholecystitis are acalculous [64].

According to Tokyo guidelines [65], a definite diag-nosis of acute cholecystitis can be made on the basis ofdiagnostic criteria in two scenarios: The first is based onone local sign of inflammation (Murphy sign or rightupper quadrant pain with mass, or tenderness) and onesystemic sign of inflammation (fever, increased C-reac-tive protein level, increased white blood cell count). Thesecond set of criteria is based on imaging findings thatare characteristic which include, a thickened gallbladderwall or enlarged gallbladder at ultrasonography (US),

Fig. 7. Coronal CECT of the abdomen and pelvis showingsmall bowel obstruction due to cecal volvulus. A The cecum isdilated and twisted in the upper abdomen/left upper quadrant

(asterix); B The twisted cecal pedicle demonstrates ‘‘me-senteric whirl sign’’ (arrows) in the ileocecal region.

K. Gangadhar et al.: Multimodality approach for imaging abdominal emergencies 143

magnetic resonance (MR) imaging or computed tomog-raphy (CT); positive sonographic Murphy sign; peric-holecystic fluid collection at US and CT; orpericholecystic high-signal intensity at MR imaging. Al-though US is the initial imaging modality of choice forevaluation of acute cholecystitis, CT often is used in theclinical setting because other disease processes such aspancreatitis, gastritis, peptic ulcer disease, and even bo-wel obstruction may mimic right upper quadrant pain[66]. MRCP sequences are often used to look for chole-docholithiasis and to make sure that the patient needs anendoscopic procedure or a surgical procedure. MRimages have excellent soft tissue contrast and can providemore specific information regarding the complicationsthat arise from acute cholecystitis, such as empyema,gangrenous cholecystitis, gallbladder perforation, ente-rocholecystic fistula, emphysematous cholecystitis, andhemorrhagic cholecystitis [67].

The imaging findings include the presence of sono-graphic Murphy’s sign, gallstones, gallbladder wall thick-ening >3 mm, gallbladder distention >5 cm in the shortaxis or >8 cm in the long axis, pericholecystic fluid,inflammatory stranding, and subserosal edema (Fig. 8) [68].

Cholecystectomy is the mainstay of the treatment ofacute cholecystitis performed either laparoscopically orthrough open surgery. Minimal invasive procedures,such as percutaneous gallbladder drainage using imageguidance or endoscopic procedures like transpapillarydrainage of the gallbladder at endoscopic retrogradecholangiopancreatography (ERCP) and endoscopicultrasonography (EUS)-guided gallbladder drainage viathe transluminal route, could be a life-saving treatment

option or serve as a bridge to elective surgery in patientswith contraindications of surgery [69].

Perforated viscus

Pneumoperitoneum in a patient with acute abdominalpain is an important diagnostic sign of gastrointestinal(GI) perforation, which is usually indicative for need forsurgical intervention [70]. GI tract perforation is a dis-ruption in the integrity of the gastrointestinal wall thatmay be caused by various etiologies including, gastro-duodenal ulcers, ischemic or bacterial enteritis, Crohn’sdisease, diverticulitis, ingested foreign bodies, bowelobstruction, volvulus, intussusception, malignancy,abdominal trauma, iatrogenic injury, and postoperativeperforation or anastomotic leakage [71].

Plain radiography is the usual screening modality forpatients with suspected GI tract perforation. The specificfinding of GI tract perforation on plain films is thepresence of air outside the gut lumen. The extraluminalair may be in the free peritoneal cavity, retroperitonealspaces, mesentery, or ligaments of organs. However,pneumoperitoneum may not be identified if the perfo-ration is very small, self-sealed, or well-contained byadjacent organs. The reported sensitivity in the detectionof extraluminal air on plain radiography is 50–70% [72].The ‘‘ligamentum teres sign’’ which is free air confinedalong ligamentum teres, can be seen in cases of perfo-rated duodenal bulb or stomach [73]. The ‘‘falciformligament sign’’ is free air or an air-fluid level crossing themidline and accentuating the falciform ligament. Thissign can be seen with perforation of the stomach andsmall bowel [74].

CT is the most reliable modality for detecting evensmall amounts of free air using ‘‘lung window’’ setting.CT also helps identify the cause of GI tract perforation(87). The direct CT findings of GI tract perforation in-clude discontinuity of the bowel wall and the presence ofextraluminal air and/or extraluminal enteric contrast areconsidered specific signs of gastrointestinal (GIT) per-foration in an intact abdomen.

Indirect CT findings of bowel perforation includebowel wall thickening, abnormal bowel wall enhance-ment, abscess, and an inflammatory mass adjacent to thebowel. Extravasation of oral contrast is specific at iden-tifying the location of a perforation.

Other indirect signs identifying the location of a GIperforation include:

1. Free air in either the supra or inframesocolic com-partments,

2. Gas bubbles adjacent to the intestinal wall,3. Localized extraluminal fluid,4. Segmental wall thickening (>3 mm),5. Perivisceral fat stranding and6. Abscess formation [70].

Fig. 8. Coronal T2 MR imaging showing imaging findings ofacute cholecystitis. Note gallstone (arrowhead) in the neckregion with pericholecystic fluid (arrows).

144 K. Gangadhar et al.: Multimodality approach for imaging abdominal emergencies

Acute bowel ischemia

Intestinal ischemia has a relatively low incidence withestimated incidence around 1% in patients hospitalizedfor acute abdomen. However recently, owing to longerlife expectancy and consequent greater incidence ofatherosclerotic vascular disease, it is more frequentlyobserved in current clinical practice [75]. Bowel ischemiaand infarction result in a high mortality and morbiditywith mortality rates exceeding 60% [76].

The primary causes of insufficient blood flow to thesmall intestine are arterial occlusive disease (throm-boembolism), veno-occlusive disease, non-occlusiveischemia resulting from low-flow states such ashypotension, bowel obstruction, neoplasms, vasculitis,abdominal inflammatory conditions, trauma,chemotherapy, radiation, and corrosive injury [77].

The designated ACR appropriateness score in pa-tients with acute mesenteric ischemia for CTA abdomenwith contrast is 9/10 (usually appropriate), radiographsof the abdomen is 7/10 (usually appropriate), MRA ab-domen without and with contrast is 7/10 (usuallyappropriate), and US abdomen is 6/10 (may be appro-priate) [78]. Although radiography is usually the initialtest requested in patients with acute abdominal pain, butusually remains non-diagnostic in most cases of mesen-teric ischemia.

Computed tomography angiography (CTA) has highsensitivity and specificity in diagnosing acute mesentericischemia and should be considered the first-line imagingin most cases [79].

CTA identifies atherosclerosis, thrombus, occlusion,compression or invasion by tumor, and trauma. Other CTfindings include bowel wall thickening and edema, sub-

mucosal hemorrhage predominantly in cases of venousinfarction, increased bowel enhancement in the earlyphase or decreased enhancement of the bowel wall in later

Fig. 9. Axial A and coronal B CECT of the abdomen on lungwindow settings showing septated gas surrounding trans-verse colon in a patient who is on Sutent therapy for meta-

static renal cancer. The findings are consistent withpneumatosis intestinalis secondary to targeted molecularagent therapy.

Fig. 10. Coronal CECT of the abdomen and pelvis showingdescending colon thickening and edema and increased bowelenhancement with ascites. The rectum is fluid filled anddemonstrates luminal dilation (circle). The walls are paperthin, non-enhancing, and non-perceivable. These imagingsigns represent impending perforation due to ischemia.

K. Gangadhar et al.: Multimodality approach for imaging abdominal emergencies 145

phases, mesenteric stranding or fluid, and pneumatosis incases of bowel necrosis and perforation [80–83].

There are some non-ischemic factors that can inducepneumatosis including chronic lung disease, peptic ulcerdisease, collagen vascular disease, use of steroid, andtreatment with certain molecular agents (Fig. 9). How-ever, the clinical state of the patient generally differen-tiates ischemia from non-ischemic causes of pneumatosis[84]. Portal venous gas is associated with advancedmesenteric infarction (present in 9–36% of cases), but itdoes not necessarily indicate transmural bowel necrosis.The presence of air in the portal branches can also becaused by other diseases such as a perforated gastriculcer, pelvic abscesses, hemorrhagic pancreatitis, dia-betes mellitus, necrotic neoplasia of the colon, divertic-ulitis, or may be associated with ingestion of causticacids.

Impending perforation can be identified by fluid-filleddilation of hollow viscus and paper thin, non-enhancing,and non-perceivable walls (Fig. 10).

MRI is used for assessment of chronic mesentericischemia and is currently more sparingly used in theacute setting. MRA is a useful way of non-invasiveevaluation of mesenteric vessels: sequences such as Timeof Flight (TOF) do not require intravenous contrastagents to visualize the vessels. However, longer acquisi-tion time, artifacts due to patient’s inability to hold thebreath and availability are the limitations.

Conclusion

Non-traumatic abdominal pain is one of the mostcommon symptoms in patients presenting to the ED

and/or admitted to hospital. There is a broad differ-ential diagnosis to consider ranging from benign tolife-threatening causes. Early diagnosis and timelymanagement of these patients is the top priority be-cause if delayed, may lead to poor clinical outcomes.Imaging plays a pivotal role in solving this issue alongwith appropriate history, physical exam, and labora-tory results. Educating ED physicians regarding ACRappropriateness criteria could be of great value inensuring that appropriate imaging algorithms are fol-lowed for these patients (Table 3). Radiologists shouldact as consultants with respect to performing the bestimaging based on clinical suspicion. Although eachmodality has specific indications and contraindications,the diagnosis by imaging is usually driven by ACRappropriateness criteria for acute abdomen dependingupon location of pain and patient’s relevant history.CT is the primary imaging modality for these casesalthough US is more specific for conditions like acutecholecystitis. MR imaging is very helpful in patientswhere radiation exposure remains a concern. MR,is the primary imaging modality for evaluating chole-docholithiasis or acute abdomen in the pregnant pa-tients. The usual causes of acute abdomen includingacute appendicitis, acute diverticulitis, acute cholecys-titis, and acute SBO are to be kept in mind and haveto be thoroughly evaluated according to the clinicalscenario.

Compliance with ethical standards

Conflict of interest The authors declare that they have no conflict ofinterest.

Table 3. ACR appropriateness criteria for most commonly used imaging modalities in setting of RUQ pain, RLQ pain, and acute mesentericischemia (Rating Scale: 1, 2, 3 Usually not appropriate; 4, 5, 6 May be appropriate; 7, 8, 9 Usually appropriate)

Variant ACR appropriatenessscore-plain radiograph

ACR appropriatenessscore-US

ACR appropriatenessscore-CT with contrast

ACR appropriatenessscore-MR with and without

contrast

RUQ pain-fever, elevated white blood cellcount, positive murphy sign

N/A 9 6 6

RUQ pain-no fever, normal white bloodcell count

N/A 9 6 6

RUQ pain-no fever, normal white bloodcell count, ultrasound shows only gall-stones

N/A N/A 7 6

RUQ pain-hospitalized patient with fever,elevated white blood cell count, andpositive murphy sign

N/A 8 6 6

RLQ pain-fever, leukocytosis, and classicpresentation clinically for appendicitisin adults

5 6 8 4

RLQ pain-fever, leukocytosis; possibleappendicitis, atypical presentation,adults, and adolescents

6 6 6 5

RLQ pain-fever, leukocytosis, pregnantwoman

2 8 6 7

RLQ pain-fever, leukocytosis, possibleappendicitis, atypical presentation inchildren (aged <14 years)

6 8 7 5

Acute mesenteric ischemia 7 6 9 (CTA) 7(MRA)

146 K. Gangadhar et al.: Multimodality approach for imaging abdominal emergencies

References

1. Stoker J, van Randen A, Lameris W, Boermeester MA (2009)Imaging patients with acute abdominal pain. Radiology 253(1):31–46. doi:10.1148/radiol.2531090302

2. MacKersie AB, Lane MJ, Gerhardt RT, et al. (2005) Nontraumaticacute abdominal pain: unenhanced helical CT compared withthree-view acute abdominal series. Radiology 237(1):114–122. doi:10.1148/radiol.2371040066

3. Mirvis SE, Young JW, Keramati B, McCrea ES, Tarr R (1986)Plain film evaluation of patients with abdominal pain: are threeradiographs necessary? AJR Am J Roentgenol 147(3):501–503. doi:10.2214/ajr.147.3.501

4. Sala E, Watson CJ, Beadsmoore C, et al. (2007) A randomized,controlled trial of routine early abdominal computed tomographyin patients presenting with non-specific acute abdominal pain. ClinRadiol 62(10):961–969. doi:10.1016/j.crad.2007.01.030

5. Plewa MC (1991) Emergency abdominal radiography. Emerg MedClin North Am 9(4):827–852

6. Young JW (1983) Cutting needless films cuts costs. AJR Am JRoentgenol 140(6):1276–1277. doi:10.2214/ajr.140.6.1276

7. Abrams HL (1979) The overutilization of X-rays. New Engl J Med301(12):668

8. Field S, Guy PJ, Upsdell SM, Scourfield AE (1985) The erectabdominal radiograph in the acute abdomen: should its routine usebe abandoned? Br Med J 290(6486):1934–1936

9. Woodring JH, Heiser MJ (1995) Detection of pneumoperitoneumon chest radiographs: comparison of upright lateral and pos-teroanterior projections. AJR Am J Roentgenol 165(1):45–47. doi:10.2214/ajr.165.1.7785629

10. Prasannan S, Zhueng TJ, Gul YA (2005) Diagnostic value of plainabdominal radiographs in patients with acute abdominal pain.Asian J Surg 28(4):246–251. doi:10.1016/S1015-9584(09)60354-7

11. van Randen A, Lameris W, Luitse JS, OPTIMA Study Group,et al. (2011) The role of plain radiographs in patients with acuteabdominal pain at the ED. Am J Emerg Med 29(6):582–589.e582.doi:10.1016/j.ajem.2009.12.020

12. Boleslawski E, Panis Y, Benoist S, et al. (1999) Plain abdominalradiography as a routine procedure for acute abdominal pain of theright lower quadrant: prospective evaluation. World J Surg23(3):262–264

13. Puylaert JB, Rutgers PH, Lalisang RI, et al. (1987) A prospectivestudy of ultrasonography in the diagnosis of appendicitis. NewEngl J Med 317(11):666–669. doi:10.1056/NEJM198709103171103

14. Jamadar DA, Jacobson JA, Morag Y, et al. (2007) Characteristiclocations of inguinal region and anterior abdominal wall hernias:sonographic appearances and identification of clinical pitfalls. AJRAm J Roentgenol 188(5):1356–1364. doi:10.2214/AJR.06.0638

15. Mazzei MA, Guerrini S, Cioffi Squitieri N, et al. (2013) The role ofUS examination in the management of acute abdomen. CritUltrasound J 5(Suppl 1):S6. doi:10.1186/2036-7902-5-S1-S6

16. Yarmish GM, Smith MP, Rosen MP, et al. (2014) ACR appro-priateness criteria right upper quadrant pain. J Am Coll Radiol11(3):316–322. doi:10.1016/j.jacr.2013.11.017

17. Khalid M, Redhu N, Nazir B, et al. (2012) Diagnostic value ofultrasonography in evaluation and management of acute abdomi-nal conditions in the paediatric age group. Afr J Paediatr Surg9(3):198–201. doi:10.4103/0189-6725.104719

18. Lameris W, van Randen A, van Es HW, Optima Study Group,et al. (2009) Imaging strategies for detection of urgent conditions inpatients with acute abdominal pain: diagnostic accuracy study.BMJ 338:2431. doi:10.1136/bmj.b2431

19. Levenson RB, Camacho MA, Horn E, et al. (2012) Eliminatingroutine oral contrast use for CT in the emergency department:impact on patient throughput and diagnosis. Emerg Radiol19(6):513–517. doi:10.1007/s10140-012-1059-7

20. Uyeda JW, Yu H, Ramalingam V, et al. (2015) Evaluation of acuteabdominal pain in the emergency setting using computed tomog-raphy without oral contrast in patients with body mass indexgreater than 25. J Comp Assist Tomogr 39(5):681–686. doi:10.1097/RCT.0000000000000277

21. Alabousi A, Patlas MN, Sne N, Katz DS (2015) Is oral contrastnecessary for multidetector computed tomography imaging of pa-tients with acute abdominal pain? Can Assoc Radiol J. doi:10.1016/j.carj.2015.03.003

22. Rosen MP, Ding A, Blake MA, et al. (2011) ACR appropriatenesscriteria(R) right lower quadrant pain—suspected appendicitis. JAm Coll Radiol 8(11):749–755. doi:10.1016/j.jacr.2011.07.010

23. Mieville FA, Gudinchet F, Brunelle F, Bochud FO, Verdun FR(2013) Iterative reconstruction methods in two different MDCTscanners: physical metrics and 4-alternative forced-choicedetectability experiments—a phantom approach. Phys Med29(1):99–110. doi:10.1016/j.ejmp.2011.12.004

24. Lubarsky M, Kalb B, Sharma P, Keim SM, Martin DR (2013) MRimaging for acute nontraumatic abdominopelvic pain: rationaleand practical considerations. Radiographics 33(2):313–337. doi:10.1148/rg.332125116

25. Pedrosa I, Rofsky NM (2003) MR imaging in abdominal emer-gencies. Radiol Clin North Am 41(6):1243–1273

26. Birchard KR, Brown MA, Hyslop WB, Firat Z, Semelka RC(2005) MRI of acute abdominal and pelvic pain in pregnant pa-tients. AJR Am J Roentgenol 184(2):452–458. doi:10.2214/ajr.184.2.01840452

27. Tkacz JN, Anderson SA, Soto J (2009) MR imaging in gastroin-testinal emergencies. Radiographics 29(6):1767–1780. doi:10.1148/rg.296095509

28. Singh A, Danrad R, Hahn PF, et al. (2007) MR imaging of theacute abdomen and pelvis: acute appendicitis and beyond. Radio-graphics 27(5):1419–1431. doi:10.1148/rg.275065021

29. Deng Y, Chang DC, Zhang Y, et al. (2010) Seasonal and day of theweek variations of perforated appendicitis in US children. PediatrSurg Int 26(7):691–696. doi:10.1007/s00383-010-2628-z

30. Jacobs JE (2006) CT and sonography for suspected acute appen-dicitis: a commentary. AJR Am J Roentgenol 186(4):1094–1096.doi:10.2214/AJR.06.0174

31. Addiss DG, Shaffer N, Fowler BS, Tauxe RV (1990) The epi-demiology of appendicitis and appendectomy in the United States.Am J Epidemiol 132(5):910–925

32. Storm-Dickerson TL, Horattas MC (2003) What have we learnedover the past 20 years about appendicitis in the elderly? Am J Surg185(3):198–201

33. Tamburrini S, Brunetti A, Brown M, Sirlin CB, Casola G (2005)CT appearance of the normal appendix in adults. Eur Radiol15(10):2096–2103. doi:10.1007/s00330-005-2784-z

34. Kim HC, Yang DM, Lee CM, et al. (2011) Acute appendicitis:relationships between CT-determined severities and serum whiteblood cell counts and C-reactive protein levels. Br J Radiol84(1008):1115–1120. doi:10.1259/bjr/47699219

35. Lai V, Chan WC, Lau HY, et al. (2012) Diagnostic power of var-ious computed tomography signs in diagnosing acute appendicitis.Clin Imag 36(1):29–34. doi:10.1016/j.clinimag.2011.04.003

36. Kim MS, Park HW, Park JY, et al. (2014) Differentiation of earlyperforated from nonperforated appendicitis: MDCT findings,MDCT diagnostic performance, and clinical outcome. AbdomImag 39(3):459–466. doi:10.1007/s00261-014-0117-x

37. Karabulut N, Kiroglu Y, Herek D, Kocak TB, Erdur B (2014)Feasibility of low-dose unenhanced multi-detector CT in patientswith suspected acute appendicitis: comparison with sonography.Clin Imag 38(3):296–301. doi:10.1016/j.clinimag.2013.12.014

38. Pedrosa I, Levine D, Eyvazzadeh AD, et al. (2006) MR imagingevaluation of acute appendicitis in pregnancy. Radiology238(3):891–899. doi:10.1148/radiol.2383050146

39. Incesu L, Coskun A, Selcuk MB, et al. (1997) Acute appendicitis:MR imaging and sonographic correlation. AJR Am J Roentgenol168(3):669–674. doi:10.2214/ajr.168.3.9057512

40. Stark C, Jousi M, Enholm B (2014) Preoperative assessment andtreatment of appendiceal mucocele complicated by acute torsion: acase report. BMC Res Notes 7:1. doi:10.1186/1756-0500-7-1

41. Rao PM, Rhea JT, Novelline RA (1997) CT diagnosis of mesen-teric adenitis. Radiology 202(1):145–149. doi:10.1148/radiology.202.1.8988204

42. Lameris W, van Randen A, van Gulik TM, et al. (2010) A clinicaldecision rule to establish the diagnosis of acute diverticulitis at theemergency department. Dis Colon Rectum 53(6):896–904. doi:10.1007/DCR.0b013e3181d98d86

43. Schwerk WB, Schwarz S, Rothmund M (1992) Sonography inacute colonic diverticulitis. A prospective study. Dis Colon Rectum35(11):1077–1084

K. Gangadhar et al.: Multimodality approach for imaging abdominal emergencies 147

44. Rao PM, Rhea JT, Novelline RA, et al. (1998) Helical CT with onlycolonic contrast material for diagnosing diverticulitis: prospectiveevaluation of 150 patients. AJR Am J Roentgenol 170(6):1445–1449. doi:10.2214/ajr.170.6.9609151

45. Hinchey EJ, Schaal PG, Richards GK (1978) Treatment of perfo-rated diverticular disease of the colon. Adv Surg 12:85–109

46. Kaiser AM, Jiang JK, Lake JP, et al. (2005) The management ofcomplicated diverticulitis and the role of computed tomography.Am J Gastroenterol 100(4):910–917. doi:10.1111/j.1572-0241.2005.41154.x

47. Shen SH, Chen JD, Tiu CM, et al. (2005) Differentiating colonicdiverticulitis from colon cancer: the value of computed tomographyin the emergency setting. J Chin Med Assoc 68(9):411–418. doi:10.1016/S1726-4901(09)70156-X

48. Buckley O, Geoghegan T, McAuley G, et al. (2007) Pictorial re-view: magnetic resonance imaging of colonic diverticulitis. EurRadiol 17(1):221–227. doi:10.1007/s00330-006-0236-z

49. Oistamo E, Hjern F, Blomqvist L, Von Heijne A, Abraham-Nordling M (2013) Cancer and diverticulitis of the sigmoid colon.Differentiation with computed tomography versus magnetic reso-nance imaging: preliminary experiences. Acta Radiol 54(3):237–241. doi:10.1258/ar.2012.120543

50. Foster NM, McGory ML, Zingmond DS, Ko CY (2006) Smallbowel obstruction: a population-based appraisal. J Am Coll Surg203(2):170–176. doi:10.1016/j.jamcollsurg.2006.04.020

51. Maglinte DD, Howard TJ, Lillemoe KD, Sandrasegaran K, RexDK (2008) Small-bowel obstruction: state-of-the-art imaging andits role in clinical management. Clin Gastroenterol Hepatol6(2):130–139. doi:10.1016/j.cgh.2007.11.025

52. Burkill GJ, Bell JR, Healy JC (2001) The utility of computedtomography in acute small bowel obstruction. Clin Radiol56(5):350–359. doi:10.1053/crad.2000.0655

53. Maglinte DD, Heitkamp DE, Howard TJ, Kelvin FM, Lappas JC(2003) Current concepts in imaging of small bowel obstruction.Radiol Clin North Am 41(2):263–283, vi

54. Lappas JC, Reyes BL, Maglinte DD (2001) Abdominal radiogra-phy findings in small-bowel obstruction: relevance to triage foradditional diagnostic imaging. AJR Am J Roentgenol 176(1):167–174. doi:10.2214/ajr.176.1.1760167

55. Mullan CP, Siewert B, Eisenberg RL (2012) Small bowel obstruc-tion. AJR Am J Roentgenol 198(2):W105–W117. doi:10.2214/AJR.10.4998

56. Di Saverio S, Catena F, Ansaloni L, et al. (2008) Water-solublecontrast medium (gastrografin) value in adhesive small intestineobstruction (ASIO): a prospective, randomized, controlled, clinicaltrial. World J Surg 32(10):2293–2304. doi:10.1007/s00268-008-9694-6

57. Schmutz GR, Benko A, Fournier L, et al. (1997) Small bowelobstruction: role and contribution of sonography. Eur Radiol7(7):1054–1058. doi:10.1007/s003300050251

58. Duron JJ, Silva NJ, du Montcel ST, et al. (2006) Adhesive post-operative small bowel obstruction: incidence and risk factors ofrecurrence after surgical treatment: a multicenter prospective study.Ann Surg 244(5):750–757. doi:10.1097/01.sla.0000225097.60142.68

59. Delabrousse E, Lubrano J, Jehl J, et al. (2009) Small-bowelobstruction from adhesive bands and matted adhesions: CT dif-ferentiation. AJR Am J Roentgenol 192(3):693–697. doi:10.2214/AJR.08.1550

60. Yen CH, Chen JD, Tui CM, et al. (2005) Internal hernia: computedtomography diagnosis and differentiation from adhesive smallbowel obstruction. J Chin Med Assoc 68(1):21–28. doi:10.1016/S1726-4901(09)70127-3

61. Millet I, Ruyer A, Alili C, et al. (2014) Adhesive small-bowelobstruction: Value of CT in identifying findings associated with theeffectiveness of nonsurgical treatment. Radiology 273(2):425–432.doi:10.1148/radiol.14132872

62. Fidler JL, Guimaraes L, Einstein DM (2009) MR imaging of thesmall bowel. Radiographics 29(6):1811–1825. doi:10.1148/rg.296095507

63. Prystowsky JB, Pugh CM, Nagle AP (2005) Current problems insurgery. Appendicitis. Curr Probl Surg 42(10):688–742. doi:10.1067/j.cpsurg.2005.07.005

64. Fagenholz PJ, de Moya MA (2014) Acute inflammatory surgicaldisease. Surg Clin North Am 94(1):1–30. doi:10.1016/j.suc.2013.10.008

65. Hirota M, Takada T, Kawarada Y, et al. (2007) Diagnostic criteriaand severity assessment of acute cholecystitis: Tokyo Guidelines. JHepato-Biliary-Pancreatic Surg 14(1):78–82. doi:10.1007/s00534-006-1159-4

66. Harvey RT, Miller WT Jr (1999) Acute biliary disease: initial CTand follow-up US versus initial US and follow-up CT. Radiology213(3):831–836. doi:10.1148/radiology.213.3.r99dc17831

67. Watanabe Y, Nagayama M, Okumura A, et al. (2007) MR imagingof acute biliary disorders. Radiographics 27(2):477–495. doi:10.1148/rg.272055148

68. Patel NB, Oto A, Thomas S (2013) Multidetector CT of emergentbiliary pathologic conditions. Radiographics 33(7):1867–1888. doi:10.1148/rg.337125038

69. Hasan MK, Itoi T, Varadarajulu S (2013) Endoscopic managementof acute cholecystitis. Gastrointest Endosc Clin North Am 23(2):453–459. doi:10.1016/j.giec.2012.12.010

70. Cadenas Rodriguez L, Marti de Gracia M, Saturio Galan N, et al.(2013) Use of multidetector computed tomography for locating thesite of gastrointestinal tract perforations. Cir Esp 91(5):316–323.doi:10.1016/j.ciresp.2012.06.004

71. Furukawa A, Sakoda M, Yamasaki M, et al. (2005) Gastroin-testinal tract perforation: CT diagnosis of presence, site, and cause.Abdom Imag 30(5):524–534. doi:10.1007/s00261-004-0289-x

72. Cho KC, Baker SR (1994) Extraluminal air. Diagnosis and sig-nificance. Radiol Clin North Am 32(5):829–844

73. Cho KC, Baker SR (1991) Air in the fissure for the ligamentumteres: new sign of intraperitoneal air on plain radiographs. Radi-ology 178(2):489–492. doi:10.1148/radiology.178.2.1987613

74. Cho HS, Yoon SE, Park SH, et al. (2009) Distinction betweenupper and lower gastrointestinal perforation: usefulness of theperiportal free air sign on computed tomography. Eur J Radiol69(1):108–113. doi:10.1016/j.ejrad.2007.08.024

75. Horton KM, Fishman EK (2001) Multi-detector row CT ofmesenteric ischemia: can it be done? Radiographics 21(6):1463–1473. doi:10.1148/radiographics.21.6.g01nv091463

76. Lee R, Tung HK, Tung PH, Cheung SC, Chan FL (2003) CT inacute mesenteric ischaemia. Clin Radiol 58(4):279–287

77. Gandhi SK, Hanson MM, Vernava AM, Kaminski DL, Longo WE(1996) Ischemic colitis. Dis Colon Rectum 39(1):88–100

78. Oliva IB, Davarpanah AH, Rybicki FJ, et al. (2013) ACR appro-priateness criteria (R) imaging of mesenteric ischemia. AbdomImag 38(4):714–719. doi:10.1007/s00261-012-9975-2

79. Cangemi JR, Picco MF (2009) Intestinal ischemia in the elderly.Gastroenterol Clin North Am 38(3):527–540. doi:10.1016/j.gtc.2009.06.002

80. Segatto E, Mortele KJ, Ji H, Wiesner W, Ros PR (2003) Acutesmall bowel ischemia: CT imaging findings. Semin Ultrasound CTMR 24(5):364–376

81. Taourel PG, Deneuville M, Pradel JA, Regent D, Bruel JM (1996)Acute mesenteric ischemia: diagnosis with contrast-enhanced CT.Radiology 199(3):632–636. doi:10.1148/radiology.199.3.8637978

82. Bartnicke BJ, Balfe DM (1994) CT appearance of intestinal ische-mia and intramural hemorrhage. Radiol Clin North Am 32(5):845–860

83. Klein HM, Lensing R, Klosterhalfen B, Tons C, Gunther RW(1995) Diagnostic imaging of mesenteric infarction. Radiology197(1):79–82. doi:10.1148/radiology.197.1.7568858

84. Connor R, Jones B, Fishman EK, Siegelman SS (1984) Pneu-matosis intestinalis: role of computed tomography in diagnosis andmanagement. J Comp Assist Tomogr 8(2):269–275

148 K. Gangadhar et al.: Multimodality approach for imaging abdominal emergencies