Multidetector helical CT in the evaluation of acute small bowel obstruction: Comparison of non-enhanced (no oral, rectal or IV contrast) and IV enhanced CT

Investigation of scan delays for CT evaluation of inner wall layering and peak enhancement of the canine stomach and small intestine using a 20 second fixed-injection-duration and bolus tracking technique

Many gastrointestinal diseases affect the mucosal layer, suggesting that on computed tomography (CT) examination, detection of consistent inner wall layering of the gastrointestinal tract may aid in detection of disease. Changes in wall enhancement can also characterise specific diseases and provide prognostic information. The objectives of this mixed retrospective and prospective analytical study were therefore to identify the scan delays for peak detection of canine stomach and small intestinal inner wall layering and enhancement when using a 20 s fixed-injection-duration and bolus tracking technique. For each patient, 700 mg I/kg iohexol was administered intravenously. Bolus tracking was used to determine aortic arrival. Diagnostic scans were performed after a post-aortic arrival scan delay. Postcontrast CT series were grouped according to post-aortic arrival scan delay: 5 s (n = 17), 10 s (n = 18), 15 s (n = 23), 20 s (n = 10), 25 s (n = 6), 30 s (n = 14), 35 s (n = 17), 40 s (n = 24), and 180 s (n = 60). The stomach and small intestine were assessed for the presence of a contrast-enhancing inner wall layer and wall enhancement. Statistical modeling showed that the scan delays for peak inner wall layering and enhancement were 10 and 15 s for the small intestine, respectively, and 40 s for the stomach. For the injection protocol used in this study, assessment of the canine gastrointestinal tract may use scan delays of 10-15 s and 40 s.

Computed Tomography in Emergency Diagnosis and Management Considerations of Small Bowel Obstruction for Surgical vs. Non-surgical Approach

BACKGROUND

Small bowel obstruction (SBO) accounts for 15% of abdominal pain complaints referred to emergency departments and imposes significant financial burdens on the healthcare system. The absence of passage of flatus or stool and abdominal distention are reported as the most common symptom and a sign of SBO, respectively. Patients who do not demonstrate severe clinical or imaging findings are typically treated with conservative approaches. Patients with clinical signs of sepsis or physical findings of peritonitis are often instantly transferred to the operating room without supplementary imaging assessment. However, in cases where symptoms are non-specific, or the physical examination is challenging, such as in cases with loss of consciousness, the diagnosis can be complicated. This paper discusses the key findings detectable on Computed tomography (CT), which are vital for the emergent triage, proper treatment, and decision making in patients with speculated SBO.

METHOD

Narrative review of the literature.

RESULTS AND CONCLUSION

CT plays a key role in emergent triage, proper treatment, and decision making. It provides high sensitivity, specificity, and accuracy in the detection of early-stage obstruction and acute intestinal vascular compromise. It can also differentiate between various etiologies of this entity which is considered an important criterion in the triage of patients into surgical vs. non-surgical treatment. There are multiple CT findings, such as mesenteric edema, lack of the small-bowel feces, bowel wall thickening, fat stranding in the mesentery, and intraperitoneal fluid, which are predictive of urgent surgical exploration.

Imaging Modalities for Evaluation of Intestinal Obstruction

It is essential for the colon and rectal surgeon to understand the evaluation and management of patients with both small and large bowel obstructions. Computed tomography is usually the most appropriate and accurate diagnostic imaging modality for most suspected bowel obstructions. Additional commonly used imaging modalities include plain radiographs and contrast imaging/fluoroscopy, while less commonly utilized imaging modalities include ultrasonography and magnetic resonance imaging. Regardless of the imaging modality used, interpretation of imaging should involve a systematic, methodological approach to ensure diagnostic accuracy.

Adhesive Small Bowel Obstruction: Predictive Radiology to Improve Patient Management

Adhesive small bowel obstruction (SBO) remains one of the leading causes of emergency room visits and is still associated with high morbidity and mortality rates. Because the management of adhesive SBO has shifted from immediate surgery to nonoperative treatment in the absence of ischemia, it is crucial to rapidly detect or predict strangulation, which requires emergent surgery. CT is now established as the best imaging technique for the initial assessment of patients suspected of having adhesive SBO. CT helps confirm the diagnosis of mechanical SBO, locate the site of obstruction, establish the cause, and detect complications. This article is a review of the role of imaging in answering specific questions to help predict the management needs of each individual patient. It includes (a) an update on the best CT signs for predicting ischemia and a need for bowel resection; (b) a discussion of the CT features that help differentiate open-loop from closed-loop obstruction and a single adhesive band from matted adhesions and how these differences can influence the management; and (c) a review of the main CT predictors of the success or failure of nonoperative management in adhesive SBO.

ACR Appropriateness Criteria® Suspected Small-Bowel Obstruction

Small-bowel obstruction is a common cause of abdominal pain and accounts for a significant proportion of hospital admissions. Radiologic imaging plays the key role in the diagnosis and management of small-bowel obstruction as neither patient presentation, the clinical examination, nor laboratory testing are sufficiently sensitive or specific enough to diagnose or guide management. This document focuses on the imaging evaluation of the two most commonly encountered clinical scenarios related to small-bowel obstruction: the acute presentation and the more indolent, low-grade, or intermittent presentation. This document hopes to clarify the appropriate utilization of the many imaging procedures that are available and commonly employed in these clinical settings. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Diagnostic utility of CT for small bowel obstruction: Systematic review and meta-analysis

BACKGROUND

To perform a systematic review and meta-analysis evaluating the diagnostic performance of computed tomography (CT) for small bowel obstruction (SBO), including diagnostic accuracy, ischemia, predicting surgical intervention, etiology and transition point.

METHODS

PubMed/MEDLINE and related databases were searched for research articles published from their inception through August 2018. Findings were pooled using bivariate random-effects and summary receiver operating characteristic curve models. Meta-regression and subgroup analyses were performed to evaluate whether publication year, patient age, enhanced CT, slice thickness and pathogenesis affected classification accuracy.

RESULTS

In total, 45 studies with a total of 4004 patients were included in the analysis. The pooled sensitivity and specificity of CT for SBO were 91% (95% confidence interval [CI]: 84%, 95%) and 89% (95% CI: 81%, 94%), respectively, and there were no differences in the subgroup analyses of age, publication year, enhanced CT and slice thickness. For ischemia, the pooled sensitivity and specificity was 82% (95% CI: 67%, 91%) and 92% (95% CI: 86%, 95%), respectively. No difference was found between enhanced and unenhanced CT based on subgroup analysis; however, high sensitivity was found in adhesive SBO compared with routine causes (96% vs. 78%, P = 0.03). The pooled sensitivity and specificity for predicting surgical intervention were 87% and 73%, respectively. The accuracy for etiology of adhesions, hernia and tumor was 95%, 70% and 82%, respectively. In addition, the pooled sensitivity and specificity for transition point was 92% and 77%, respectively.

CONCLUSIONS

CT has considerable accuracy in diagnosis of SBO, ischemia, predicting surgical intervention, etiology and transition point.

Intravenous Contrast Agent in Abdominal CT: Is It Really Needed to Identify the Cause of Bowel Obstruction? Proof of Concept

Background

To compare sensitivity of unenhanced computed tomography (CT) and contrast-enhanced CT for the identification of the etiology of bowel obstruction.

Materials and Methods

We retrospectively evaluated abdominal CT scans of patients operated for bowel obstruction from March 2013 to October 2017. Two radiologists evaluated CT scans before and after contrast agent in two reading sessions. Then, we calculated sensitivity of CT in the diagnosis of bowel obstruction and determined in which cases the etiology of bowel obstruction was detected on both unenhanced and enhanced CT or on enhanced CT only. The reference standard was defined as the final diagnosis obtained after surgery.

Results

Eighteen patients (mean age 72 ± 15 years, age range 37-88 years) were included in the study. Sensitivity of unenhanced CT and enhanced CT was not significantly different in either small bowel obstruction (64%, 7/11 patients vs. 73%, 8/11 patients; P = 0.6547) or large bowel obstruction (71%, 5/7 patients vs. 100%, 7/7 patients; P = 0.1410). Adhesions were identified on unenhanced CT as the etiology of small bowel obstruction in 80% (4/5) of patients. Tumors were identified on unenhanced CT as the etiology of large bowel obstruction in 67% (4/6) of patients.

Conclusion

In the diagnosis of small bowel obstruction due to adhesions with normal bowel wall thickening and when a neoplasm is identified as the etiology of large bowel obstruction on unenhanced CT, an intravenous contrast agent may be avoided for the identification of the etiology. In remaining cases, contrast agent is still recommended.

Emergency Medicine Evaluation and Management of Small Bowel Obstruction: Evidence-Based Recommendations

BACKGROUND

Small bowel obstruction (SBO) is a commonly diagnosed disease in the emergency department (ED). Recent literature has evaluated the ED investigation and management of SBO.

OBJECTIVE

This review evaluates the ED investigation and management of adult SBO based on the current literature.

DISCUSSION

SBO is most commonly due to occlusion of the small intestine, resulting in fluid and gas accumulation. This may progress to mucosal ischemia, necrosis, and perforation. A variety of etiologies are present, but in adults, adhesions are the most common cause. Several classification systems are present. However, the most important distinction is complete vs. partial and complicated vs. simple obstruction, as complete complicated SBO more commonly requires surgical intervention. History and physical examination can vary, but the most reliable findings include prior abdominal surgery, history of constipation, abdominal distension, and abnormal bowel sounds. Signs of strangulation include fever, hypotension, diffuse abdominal pain, peritonitis, and several others. Diagnosis typically requires imaging, and though plain radiographs are often ordered, they cannot exclude the diagnosis. Computed tomography and ultrasound are reliable diagnostic methods. Management includes intravenous fluid resuscitation, analgesia, and determining need for operative vs. nonoperative therapy. Nasogastric tube is useful for patients with significant distension and vomiting by removing contents proximal to the site of obstruction. Surgery is needed for strangulation and those that fail nonoperative therapy. Surgical service evaluation and admission are recommended.

CONCLUSION

SBO is a common reason for admission from the ED. Knowledge of recent literature can optimize diagnosis and management.

MDCT findings in small bowel obstruction: implications of the cause and presence of complications on treatment decisions

Small bowel obstruction (SBO) accounts for a considerable proportion of emergency room visits, inpatient admissions, and surgical interventions in the United States. Multi-detector computed tomography (MDCT) plays a key role in imaging patients presenting with acute symptoms suggestive of SBO, which helps in establishing the diagnosis, elucidating the cause of obstruction, and detecting complications, such as ischemia or frank bowel necrosis and perforation. Recently, management of patients with SBO has shifted toward a more conservative approach with supportive care and nasogastric tube decompression, as the obstruction in many cases can resolve spontaneously without the need for operative intervention. However, management decisions in SBO remain notoriously difficult, relying on a combination of clinical, laboratory, and imaging factors to help stratify patients into conservative or surgical treatment. Imaging is often an important factor assisting in the decision-making process since traditional clinical signs of vascular compromise, such as acidosis, fever, leukocytosis, and tachycardia are often unreliable in predicting the need for operative intervention. Thus, it is critically important for radiologists to identify imaging features that suggest or indicated high likelihood of bowel vascular compromise in order to help optimize management prior to the development of bowel ischemia and eventually necrosis. By excluding signs of potentially ischemic or necrotic bowel on MDCT, patients may be spared unnecessary surgery, thus decreasing postsurgical complications and averting potential increase for the risk of future SBO and repeated surgery. Conversely, if imaging features indicate potential vascular compromise of the bowel wall that may lead to bowel ischemia, urgent surgical intervention may prevent progression to bowel necrosis and subsequent perforation.

Review of small-bowel obstruction: the diagnosis and when to worry

This is a review of small-bowel obstruction written primarily for residents. The review focuses on radiography and computed tomography (CT) for diagnosing small-bowel obstruction and CT for determining complications. (©) RSNA, 2015.

Colonic stenting: a practical update

Colonic stenting is part of the UK service provision guidelines for colorectal cancer. However, there are issues about availability and expertise within the UK, and controversies remain regarding various clinical and technical aspects of the technique. Based on the current evidence, this article will provide a practical update on the indications, the clinical and technical considerations and the remaining unanswered questions regarding colonic stenting.

Adult small bowel obstruction

BACKGROUND

Small bowel obstruction (SBO) is a clinical condition that is often initially diagnosed and managed in the emergency department (ED). The high rates of potential complications that are associated with an SBO make it essential for the emergency physician (EP) to make a timely and accurate diagnosis.

OBJECTIVES

The primary objective was to perform a systematic review and meta-analysis of the history, physical examination, and imaging modalities associated with the diagnosis of SBO. The secondary objectives were to identify the prevalence of SBO in prospective ED-based studies of adult abdominal pain and to apply Pauker and Kassirer's threshold approach to clinical decision-making to the diagnosis and management of SBO.

METHODS

MEDLINE, EMBASE, major emergency medicine (EM) textbooks, and the bibliographies of selected articles were scanned for studies that assessed one or more components of the history, physical examination, or diagnostic imaging modalities used for the diagnosis of SBO. The selected articles underwent a quality assessment by two of the authors using the Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS-2) tool. Data used to compile sensitivities and specificities were obtained from these studies and a meta-analysis was performed on those that examined the same historical component, physical examination technique, or diagnostic test. Separate information on the prevalence and management of SBO was used in conjunction with the meta-analysis findings of computed tomography (CT) to determine the test and treatment threshold.

RESULTS

The prevalence of SBO in the ED was determined to be approximately 2% of all patients who present with abdominal pain. Having a previous history of abdominal surgery, constipation, abnormal bowel sounds, and/or abdominal distention on examination were the best history and physical examination predictors of SBO. X-ray was determined to be the least useful imaging modality for the diagnosis of SBO, with a pooled positive likelihood ratio (+LR) of 1.64 (95% confidence interval [CI] = 1.07 to 2.52). On the other hand, CT and magnetic resonance imaging (MRI) were both quite accurate in diagnosing SBO with +LRs of 3.6 (5- to 10-mm slices, 95% CI = 2.3 to 5.4) and 6.77 (95% CI = 2.13 to 21.55), respectively. Although limited to only a select number of studies, the use of ultrasound (US) was determined to be superior to all other imaging modalities, with a +LR of 14.1 (95% CI = 3.57 to 55.66) and a negative likelihood ratio (-LR) of 0.13 (95% CI = 0.08 to 0.20) for formal scans and a +LR of 9.55 (95% CI = 2.16 to 42.21) and a -LR of 0.04 (95% CI = 0.01 to 0.13) for beside scans. Using the CT results of the meta-analysis for the 5- to 10-mm slice subgroup as well as information on intravenous (IV) contrast reactions and nasogastric (NG) intubation management, the pretest probability threshold for further testing was determined to be 1.5%, and the pretest probability threshold for beginning treatment was determined to be 20.7%.

CONCLUSIONS

The potentially useful aspects of the history and physical examination were limited to a history of abdominal surgery, constipation, and the clinical examination findings of abnormal bowel sounds and abdominal distention. CT, MRI, and US are all adequate imaging modalities to make the diagnosis of SBO. Bedside US, which can be performed by EPs, had very good diagnostic accuracy and has the potential to play a larger role in the ED diagnosis of SBO. More ED-focused research into this area will be necessary to bring about this change.

Evaluation and management of small-bowel obstruction: an Eastern Association for the Surgery of Trauma practice management guideline

BACKGROUND

Small-bowel obstruction (SBO) represents as many as 16% of surgical admissions and more than 300,000 operations annually in the United States. The optimal strategies for the diagnosis and management of SBO continue to evolve secondary to advances in imaging techniques, critical care, and surgical techniques. This updated systematic literature review was developed by the Eastern Association for the Surgery of Trauma to provide up-to-date evidence-based recommendations for SBO.

METHODS

A search of the National Library of Medicine MEDLINE database was performed using PubMed interface for articles published from 2007 to 2011.

RESULTS

The search identified 53 new articles that were then combined with the 131 studies previously reviewed by the 2007 guidelines. The updated guidelines were then presented at the 2012 annual EAST meeting.

CONCLUSION

Level I evidence now exists to recommend the use of computed tomographic scan, especially multidetector computed tomography with multiplanar reconstructions, in the evaluation of patients with SBO because it can provide incremental clinically relevant information over plains films that may lead to changes in management. Patients with evidence of generalized peritonitis, other evidence of clinical deterioration, such as fever, leukocytosis, tachycardia, metabolic acidosis, and continuous pain, or patients with evidence of ischemia on imaging should undergo timely exploration. The remainder of patients can safely undergo initial nonoperative management for both partial and complete SBO. Water-soluble contrast studies should be considered in patients who do not clinically resolve after 48 to 72 hours for both diagnostic and potential therapeutic purposes. Laparoscopic treatment of SBO has been demonstrated to be a viable alternative to laparotomy in selected cases.

Bowel obstruction and hernia

Bowel obstruction and abdominal hernia are commonly observed in patients seeking emergency care for abdominal pain. This article discusses bowel obstruction, adynamic ileus, acute colonic pseudo-obstruction, and abdominal hernias, with particular emphasis on the management of patients in the emergency department (ED). Although the diagnostic approach to bowel obstruction often requires imaging, abdominal hernia may be identified in most circumstances by history and physical examination alone. Urgent surgical consultation is indicated when there is a concern for bowel ischemia, strangulation, or complete obstruction. This article reviews an ED-based approach to the patient presenting with symptoms of bowel obstruction or hernia.

[Mechanical obstruction as a cause of acute abdomen. Radiological differential diagnosis]

Mechanical obstruction is a common cause of acute abdomen. Besides the diagnosis of the obstruction itself it is crucial to recognize the cause of the obstruction for planning of conservative or operative treatment.This article gives a general overview of the methods available for imaging obstructions in the setting of an acute abdomen. In the second part the differential diagnoses of the most common causes of obstruction will be discussed.

The relevance of transition zones on computed tomography in the management of small bowel obstruction

BACKGROUND

Frequently, radiologists emphasize radiographic transition zones (RTZs) on computed tomography (CT), which are areas of abrupt change from dilated to collapsed bowel, as pathognomonic for small-bowel obstruction (SBO) diagnosis and location. The relevance of RTZs to patient management remains unknown. The purpose of this study was to determine the surgical predictive value and intraoperative accuracy of RTZ.

METHODS

A retrospective review of 200 patients with SBO who underwent abdominal CT at a single institution from 2002 to 2007 was performed. Statistical analysis was conducted using an unpaired t test, a Chi-square test, and multivariate analysis.

RESULTS

Of the 200 patients with SBO, 150 (75%) had an RTZ. Seventy-five (38%) patients required operative intervention; 58 (39%) patients had RTZ and 17 (34%) patients did not have RTZ (P=NS). The presence of RTZ was not associated with increased probability of operative versus nonoperative management (odds ratio=1.19; 95% confidence interval [0.61-2.32]). The mean time to operative intervention was 3.6 days. Immediate operative intervention (<24 h) was equivalent in patients with versus without RTZ (57% vs 53%; P=NS) as was intervention for failed nonoperative management (43% vs 47%; P=NS). For patients who required operative intervention, RTZ correlated with intraoperative site of obstruction in only 31 (63%) patients.

CONCLUSION

The presence of RTZs does not increase the likelihood of operative intervention or identify patients who will fail nonoperative management. RTZ should, therefore, not be used as a major criterion influencing operative versus nonoperative management decisions in patients with SBO. For patients who required operative intervention, RTZ had a 63% correlation with intra-operative findings, which makes it a useful adjunct to pre-operative planning.

Multiphasic MDCT in small bowel volvulus

OBJECTIVE

Evaluate the use of MDCT with 3D CT angiography (CTA) and CT portal venography (CTPV) reconstruction for the diagnosis of small bowel volvulus (SBV).

METHODS

Multiphasic MDCT findings in nine patients (seven males and two females, age range 2-70) with surgically proven SBV were retrospectively reviewed. Non-contrast and double phase contrast enhanced MDCT including 3D CTA and CTPV reconstruction were performed in all the patients. Two experienced abdominal radiologists evaluated the images and defined the location, direction and degree of SBV.

RESULTS

On axial MDCT images, all cases show segmental or global dilatation of small intestine. Other findings include circumferential bowel wall thickening in eight cases, halo appearance and hyperemia in seven cases, whirl sign in six cases, beak-like appearance in six cases, closed loops in six cases and ascites in one case. CTA/CTPV showed abnormal courses involving main trunks of superior mesenteric artery (SMA) and superior mesenteric vein (SMV) in seven cases, with or without distortion of their tributaries. Normal course of SMA but abnormal course of SMV was seen in the other two cases. Of all the nine cases, whirl sign was seen in six cases and barber's pole sign in five cases. Dilated SMV was observed in eight cases and abrupt termination of SMA was found in one case. Compared with surgical findings, the location, direction and degree of SBV were correctly estimated in all cases based on CTA/CTPV.

CONCLUSION

Multiphasic MDCT with CTA/CTPV reconstruction can play an important role in the diagnosis of SBV. The location, direction and degree of SBV can all be defined preoperatively using this method.