Adhesive Small Bowel Obstruction: Predictive Radiology to Improve Patient Management

Deep learning for automatic bowel-obstruction identification on abdominal CT

RATIONALE AND OBJECTIVES

Automated evaluation of abdominal computed tomography (CT) scans should help radiologists manage their massive workloads, thereby leading to earlier diagnoses and better patient outcomes. Our objective was to develop a machine-learning model capable of reliably identifying suspected bowel obstruction (BO) on abdominal CT.

MATERIALS AND METHODS

The internal dataset comprised 1345 abdominal CTs obtained in 2015-2022 from 1273 patients with suspected BO; among them, 670 were annotated as BO yes/no by an experienced abdominal radiologist. The external dataset consisted of 88 radiologist-annotated CTs. We developed a full preprocessing pipeline for abdominal CT comprising a model to locate the abdominal-pelvic region and another model to crop the 3D scan around the body. We built, trained, and tested several neural-network architectures for the binary classification (BO, yes/no) of each CT. F1 and balanced accuracy scores were computed to assess model performance.

RESULTS

The mixed convolutional network pretrained on a Kinetics 400 dataset achieved the best results: with the internal dataset, the F1 score was 0.92, balanced accuracy 0.86, and sensitivity 0.93; with the external dataset, the corresponding values were 0.89, 0.89, and 0.89. When calibrated on sensitivity, this model produced 1.00 sensitivity, 0.84 specificity, and an F1 score of 0.88 with the internal dataset; corresponding values were 0.98, 0.76, and 0.87 with the external dataset.

CONCLUSION

The 3D mixed convolutional neural network developed here shows great potential for the automated binary classification (BO yes/no) of abdominal CT scans from patients with suspected BO.

CLINICAL RELEVANCE STATEMENT

The 3D mixed CNN automates bowel obstruction classification, potentially automating patient selection and CT prioritization, leading to an enhanced radiologist workflow.

KEY POINTS

• Bowel obstruction's rising incidence strains radiologists. AI can aid urgent CT readings. • Employed 1345 CT scans, neural networks for bowel obstruction detection, achieving high accuracy and sensitivity on external testing. • 3D mixed CNN automates CT reading prioritization effectively and speeds up bowel obstruction diagnosis.

Pearls and Pitfalls of Imaging Small Bowel Obstruction

Small bowel obstruction (SBO) is a common condition encountered by radiologists in the evaluation of patients with abdominal pain, and is an important diagnosis to be comfortable with given substantial associated morbidity and mortality. In this review, we summarize an imaging approach to evaluating patients with suspected SBO, discuss the role of certain imaging modalities such as radiography and small bowel follow through, CT, and MRI, as well as review some common and also less common causes of SBO such as internal hernia. We will also discuss tailoring the imaging approach to address specific clinical questions and special patient populations such as imaging the pregnant patient with suspected SBO, and the inflammatory bowel disease patient.

Prognostic value of CT findings for conservative treatment failure in adhesive small bowel obstruction

PURPOSE

This study aimed to identify the radiological CT findings that are significantly correlated with the outcome of conservative management with oral water-soluble contrast medium in patients presenting with Adhesive Small Bowel Obstruction (ASBO) to the Emergency Room.

METHODS

In this retrospective single-center study, we considered all consecutive patients admitted to the ER from February 2019 to February 2023 for ASBO with an available contrast-enhanced CT scan performed at diagnosis and treated with conservative management. The investigated CT findings were type and location of transition zone, ASBO degree, fat notch sign, beak sign, small bowel feces sign, presence of peritoneal free fluid and pneumatosis intestinalis. Radiological parameters were analyzed using univariable and multivariable logistic regression to test the significant association between the CT parameters and the target.

RESULTS

Among the 106 included patients (median age 74.5 years), conservative treatment was effective in 59 (55.7%) and failed in 47 (44.3%), needing delayed surgery. In the failure group, there was a higher prevalence of patients who had previous ASBO episodes (p = 0.03), a greater proportion of females (p = 0.04) and a longer hospital stay (p < 0.001). At multivariable analysis, two CT findings were significantly correlated with failure of conservative treatment: fat notch sign (OR = 2.95; p = 0.04) and beak sign (OR = 3.42; p = 0.04).

CONCLUSIONS

Two radiological signs correlate with failure of non-operative management in ASBO, suggesting their importance in surgical decision-making. Patients presenting with these signs are at higher risk of unsuccessful conservative treatment and may require undelayed surgical intervention.

A case study of an acute internal hernia: The complex diagnostic challenges of Roux-en-Y gastric bypass complications

ABSTRACT

Obesity remains a global health challenge linked to several comorbidities, such as obstructive sleep apnea, hypertension, hyperlipidemia, and diabetes. The prevalence of bariatric surgeries being performed is steadily increasing because it is a highly effective surgical tool used to achieve significant permanent weight loss. However, with all weight loss surgeries, several complications may not present for months to years after the initial procedure. In particular, the anatomical changes that occur after the Roux-en-Y gastric bypass (RNYGB) make the risk of internal hernias high. This particular complication is rare but lethal if unrecognized and not treated promptly. This clinical case study aims to provide readers with an overview of diagnosing and recognizing an internal hernia in the setting of previous laparoscopic RNYGB surgical history. Because of the sheer increase in the volume of patients undergoing bariatric surgery worldwide, health care providers must be well educated on the insidious presentations of this late complication and be prepared to act quickly to diagnose and treat these acute abdomen scenarios.

Prediction of bowel necrosis by reduced bowel wall enhancement in closed-loop small bowel obstruction: Quantitative methods

PURPOSE

To assess diagnostic performance and reproducibility of reduced bowel wall enhancement evaluated by quantitative methods using CT to identify bowel necrosis among closed-loop small bowel obstruction (CL-SBO) patients.

METHODS

This retrospective single-center study included patients who diagnosed with CL-SBO caused by adhesion or internal hernia during January 2016 and May 2022. Patients were divided into necrotic group (n = 41) and non-necrotic group (n = 67) according to surgical exploration and postoperative pathology. Two doctors independently measured the attenuation of bowel wall and consensus was reached through panel discussion with a third gastrointestinal radiologist. Reduced bowel wall enhancement was assessed by four quantitative methods. Univariate analyses were used to evaluate the association between each method and bowel necrosis, and kappa/intraclass correlation coefficient values were used to assess interobserver agreement. Diagnostic performance parameters were calculated for each method.

RESULTS

Reduced bowel wall enhancement in arterial phase (OR 8.98, P < 0.0001), reduced bowel wall enhancement in portal phase (OR 16.84, P < 0.001), adjusted reduced bowel wall enhancement in arterial phase (OR 29.48, P < 0.001), adjusted reduced bowel wall enhancement in portal phase (OR 145.69, P < 0.001) were significantly associated with bowel necrosis. Adjusted reduced bowel wall enhancement in portal phase had the best diagnostic performance (AUC: 0.92; Youden index: 0.84; specificity: 94.03 %) and interobserver agreement (kappa value of 0.59-0.73) to predict bowel necrosis.

CONCLUSION

When assessing reduced bowel enhancement to predict bowel necrosis among CL-SBO patients, using unenhanced CT images and proximal dilated loop as standard references in portal phase is the most accurate quantitative method among those tested.

A Rare Case of Small Bowel Obstruction due to Migration of a Percutaneous Biliary Stent

Biliary endoprostheses are widely used in the treatment of biliary lithiasis, malignant and benign strictures, and occasionally in long-lasting biliary fistulas. They can be placed endoscopically during endoscopic retrograde cholangiopancreatography and radiologically (percutaneous) when the endoscopic route is not feasible. Complications associated with the endoscopic placement of biliary endoprostheses are well described in the literature, with migration being the most common. Intestinal obstruction is a rare complication associated with the migration of these devices. There are no reports in the literature of this complication occurring after percutaneous placement. We present a case of a patient who arrived at the emergency department with ileal obstruction secondary to the migration and concurrent embedding of a covered stent placed radiologically to treat a biliary leak after surgery. The patient underwent diagnostic laparoscopic and ileal resection, revealing a lithiasic concretion at the tip of the stent, causing the small bowel obstruction.

Deep learning using computed tomography to identify high-risk patients for acute small bowel obstruction: development and validation of a prediction model : a retrospective cohort study

OBJECTIVE

To build a novel classifier using an optimized 3D-convolutional neural network for predicting high-grade small bowel obstruction (HGSBO).

SUMMARY BACKGROUND DATA

Acute SBO is one of the most common acute abdominal diseases requiring urgent surgery. While artificial intelligence and abdominal computed tomography (CT) have been used to determine surgical treatment, differentiating normal cases, HGSBO requiring emergency surgery, and low-grade SBO (LGSBO) or paralytic ileus is difficult.

METHODS

A deep learning classifier was used to predict high-risk acute SBO patients using CT images at a tertiary hospital. Images from three groups of subjects (normal, nonsurgical, and surgical) were extracted; the dataset used in the study included 578 cases from 250 normal subjects, with 209 HGSBO and 119 LGSBO patients; over 38 000 CT images were used. Data were analyzed from 1 June 2022 to 5 February 2023. The classification performance was assessed based on accuracy, sensitivity, specificity, and area under the receiver operating characteristic curve.

RESULTS

After fivefold cross-validation, the WideResNet classifier using dual-branch architecture with depth retention pooling achieved an accuracy of 72.6%, an area under receiver operating characteristic of 0.90, a sensitivity of 72.6%, a specificity of 86.3%, a positive predictive value of 74.1%, and a negative predictive value of 86.6% on all the test sets.

CONCLUSIONS

These results show the satisfactory performance of the deep learning classifier in predicting HGSBO compared to the previous machine learning model. The novel 3D classifier with dual-branch architecture and depth retention pooling based on artificial intelligence algorithms could be a reliable screening and decision-support tool for high-risk patients with SBO.

The role of computed tomography in enterolith causing small bowel obstruction: A case series

Intestinal obstruction caused by enteroliths is an uncommon medical condition. Timely detection of the presence of enteroliths and identification of their origin can guide clinical treatment. This study aimed to present the Computed Tomography (CT) features of enterolithic ileus confirmed by surgery in 7 patients. Seven patients with surgically confirmed enterolithic ileus who were admitted to our hospital between December 2013 and December 2022 were continuously enrolled, and an abdominopelvic CT examination was performed before surgery. The imaging characteristics were then analyzed. In the transition zone of all patients with intestinal obstruction, the sharply defined intraluminal masses were found. Three of them had gallstones and 4 had primary enteroliths. All 5 enteroliths in the 4 patients with primary enteroliths were in the proximal small intestine and were low-density with gas. Additionally, 3 gallstones were present in the distal small bowel, and calcifications were observed. Simultaneously, cholecystitis and secondary cholecystoduodenal fistula were observed in all 3 patients with gallstones. Compared to gallstones, primary enteroliths tend to be higher positioned, less dense, and accompanied by gas. CT examination is very important, as it allows accurate identification, location, diagnosis, and identification of complications of the different types of enteroliths to provide a basis for surgery.

Complex Surgical Intervention for Small Bowel Obstruction Secondary to Metastatic Colorectal Cancer

Small bowel obstruction (SBO) refers to the inability of contents to pass through the lumen of the small intestine. This is a common surgical emergency in the United States. Although intra-abdominal adhesions are the predominant cause, SBO can occur secondarily to various etiologies, be it one cause or several. Management of SBO secondary to adhesions and metastasized rectal adenocarcinoma, complicated by pulmonary, hepatic, and ureteral disease, highlights the criticality of a multidisciplinary approach. We present a case of a 59-year-old male with SBO secondary to rectal adenocarcinoma. Treatment included surgical resection, acute stabilization, referral for outpatient surgical follow-up, and oncologic management.

Unenhanced CT-based predictive model to identify small bowel necrosis in patients with mechanical small bowel obstruction

OBJECTIVES

To investigate the diagnostic value of unenhanced CT in mechanical small bowel obstruction (SBO) with small bowel necrosis, and to establish a predictive model.

METHODS

From May 2017 to December 2021, the patients with mechanical SBO admitted to our hospital were retrospectively collected. Taking pathology-confirmed small bowel necrosis as the gold standard, the experimental group was composed of patients with small bowel necrosis confirmed by pathology, and the control group was composed of patients with no intestinal necrosis confirmed by surgery or successful conservative treatment with no recurrence of intestinal obstruction during 1-month followed-up.

RESULTS

A total of 182 patients were enrolled in this study, 157 patients underwent surgery, of which 35 patients were accompanied with small bowel necrosis and 122 patients were not (33 patients with ischemic findings at surgery without necrosis). Finally, there were 35 patients in the experimental group and 147 patients in the control group. Multivariable logistic regression showed that increased attenuation of small bowel wall (P = 0.002), diffuse mesenteric haziness (P = 0.010), difference of CT value between mesenteric vessel and aorta (P = 0.025) and U-/C-shaped small bowel loop (P = 0.010) were independent risk factors for the diagnosis of mechanical SBO with small bowel necrosis. Through internal verification, the area under curve (AUC) of the predictive model reached 0.886 (95%CI: 0.824-0.947), and the calibration result was moderate.

CONCLUSION

Multiple features (increased attenuation of small bowel wall; difference of CT values between mesenteric vessel and aorta; diffuse mesenteric haziness; and U-/C-shaped small bowel loop) of unenhanced CT have clinical value in the diagnosis of mechanical SBO with small bowel necrosis. The predictive model based on these four features could achieve satisfactory efficiency.

Closed loop obstruction of small bowel: CT signs predicting successful non-surgical treatment

PURPOSE

To clarify the computed tomography (CT) findings related to successful conservative treatments in patients with closed-loop small bowel obstruction (CL-SBO) without evidence of bowel strangulation.

METHODS

Sixty-four patients (71 CT scans) diagnosed with CL-SBO by CT and received initial conservative treatments from May 2010 to August 2020 were retrospectively included. Two blinded radiologists reviewed the CT findings, including the transition zone (number, distance, and location), maximum bowel diameter, mesenteric haziness, mesenteric fluid, increased unenhanced bowel wall attenuation, decreased bowel wall enhancement, small bowel feces sign, whirl sign, bowel wall thickening, ascites, and degree of obstruction. The findings of the success and failure groups of conservative treatment were compared. Interobserver agreement was assessed for all findings.

RESULTS

Among the 71 cases, conservative treatments were successful in 42 cases (59 %) but failed in 29 cases (41 %). In multivariable analyses, the distance between the transition zones (>1 cm) and low-degree obstruction were independently associated with successful conservative treatments, with odds ratios of 6.23 and 3.52, respectively. The combination of these two CT findings exhibited a specificity of 89.7 % with a positive likelihood ratio of 3.01. Interobserver agreement of the degree of obstruction and the distance between the transition zones was almost perfect (ĸ = 0.814 and 0.914, respectively).

CONCLUSIONS

The distance between the transition zones (>1 cm) and low-grade obstruction are independent CT predictors of successful conservative treatments in CL-SBO patients. Initial conservative treatments are recommended for patients with both CT findings.

Bowel obstruction: signs indicating the need for urgent surgery

Bowel obstruction is common in emergency departments. Obstruction is more common in the small bowel than in the large bowel. The most common cause is postsurgical adhesions. Nowadays, bowel obstruction is diagnosed with multidetector computed tomography (MDCT). MDCT studies for suspected bowel obstruction should focus on four points that need to be mentioned in the report: confirming the obstruction, determining whether there is a single transition point or whether the obstruction is found in a closed loop, establishing the cause of the obstruction, and seeking signs of complications. Identifying signs of ischemia is important in the management of the patient because it enables patients at higher risk of poor outcomes after conservation treatment who could benefit from early surgical intervention to avoid greater morbidity and mortality associated with strangulation and ischemia of the obstructed bowel loop.

Complications of Mesh Sacrocolpopexy and Rectopexy: Imaging Review

Sacrocolpopexy and rectopexy are commonly used surgical options for treatment of patients with pelvic organ and rectal prolapse, respectively. These procedures involve surgical fixation of the vaginal vault or the rectum to the sacral promontory with mesh material and can be performed independently of each other or in a combined fashion and by using an open abdominal approach or laparoscopy with or without robotic assistance. Radiologists can be particularly helpful in cases where patients' surgical histories are unclear by identifying normal sacrocolpopexy or rectopexy mesh material and any associated complications. Acute complications such as bleeding or urinary tract injury or stricture are generally evaluated with CT. More chronic complications such as mesh extrusion or exposure with or without fistulization to surrounding structures are generally evaluated with MRI. Other complications can have a variable time of onset after surgery. Patients with suspected bowel obstruction are generally evaluated with CT. Those with suspected infection, abscess formation, and discitis or osteomyelitis may be evaluated with MRI, although CT evaluation may be appropriate in certain scenarios. The authors review the sacrocolpopexy and rectopexy surgical techniques, discuss appropriate imaging protocols for evaluation of patients with suspected complications, and illustrate the normal appearance and common complications of these procedures. ^© RSNA, 2023 Quiz questions for this article are available in the supplemental material.

An Update on Acute Mesenteric Ischemia

Acute mesenteric ischemia (AMI) is an uncommon yet highly lethal cause of acute abdomen in the emergency setting. Computed tomography (CT) imaging, in particular a biphasic protocol consisting of angiographic and venous phase scans, is widely used to corroborate non-specific clinical findings when suspicions of AMI are high. Techniques such as low kilovoltage peak scanning, dual energy acquisition, or a combined arterial/enteric phase can improve iodine conspicuity and evaluation of bowel enhancement. Biphasic CT with CT angiography is mandatory to directly assess for the 3 primary etiologies of AMI-arterial, venous, and non-occlusive mesenteric ischemia (NOMI), and the CT angiographic findings may be the first visible in the disease. In addition, numerous non-vascular CT findings have also been reported. Bowel wall thickening, mesenteric stranding, and ascites are common but non-specific findings that correlate poorly with disease severity. Pneumatosis intestinalis and portomesenteric venous gas, while not pathognomonic for ischemia, are highly specific in cases of high clinical suspicion. Bowel wall hypoenhancement is an early and specific sign but requires a protocol optimizing iodine conspicuity to confidently identify. Finally, intraperitoneal free air and solid organ infarcts are also highly specific ancillary findings in AMI. AMI occurs as a complication in 10% of small bowel obstruction (SBO) patients, and understanding imaging findings of ischemia in the context of SBO is necessary to aid in treatment planning and reduce over- and under-diagnosis of strangulation. Familiarity with the imaging features of ischemia by radiologists is vital to establish an early diagnosis before irreversible necrosis occurs.

Progress in diagnosis and treatment of surgery-related adhesive small intestinal obstruction

Adhesive small bowel obstruction is a relatively common surgical acute abdomen, which is caused by various factors that result in the contents of the small bowel failing to pass smoothly. The clinical symptoms include abdominal pain, distension, nausea and vomiting, and defecation disorder. The chance of adhesive small bowel obstruction to develop in patients with a history of abdominal surgery is around 2.4%. This paper discusses the most recent developments in the conservative and surgical management of adhesive small bowel obstruction based on clinical manifestation, laboratory analysis, and imaging examination.

Understanding CT imaging findings based on the underlying pathophysiology in patients with small bowel ischemia

Because acute small bowel ischemia has a high mortality rate, it requires rapid intervention to avoid unfavorable outcomes. Computed tomography (CT) examination is important for the diagnosis of bowel ischemia. Acute small bowel ischemia can be the result of small bowel obstruction or mesenteric ischemia, including mesenteric arterial occlusion, mesenteric venous thrombosis, and non-occlusive mesenteric ischemia. The clinical significance of each CT finding is unique and depends on the underlying pathophysiology. This review describes the definition and mechanism(s) of bowel ischemia, reviews CT findings suggesting bowel ischemia, details factors involved in the development of small bowel ischemia, and presents CT findings with respect to the different factors based on the underlying pathophysiology. Such knowledge is needed for accurate treatment decisions.

Obstrucción intestinal por adherencias: un lienzo en blanco en el que el cirujano elige los colores

Introducción. La obstrucción intestinal es una patología de alta prevalencia. Su abordaje diagnóstico y terapéutico ha evolucionado acorde con el avance del conocimiento e implementación de la tecnología. El impacto de sus complicaciones obliga a redoblar esfuerzos en pro de lograr una mayor efectividad. Se hizo una aproximación reflexiva al problema, mediante una identificación de los puntos controversiales de interés para el cirujano general. Métodos. Se realizó una búsqueda sistemática de la literatura en varias bases de datos, utilizando dos ecuaciones de búsqueda que emplearon términos seleccionados a partir de los tesauros “Medical Subject Heading” (MeSH) y “Descriptores en Ciencias de la Salud” (DeCS). Resultados. Se recolectaron 43 artículos y a partir de ellos se construyó el texto de revisión. La identificación pronta de los posibles candidatos a cirugía, mediante un esquema diagnóstico y terapéutico, se constituye en una prioridad en el manejo de estos pacientes. De igual manera, se efectúan consideraciones en la toma de decisiones con respecto a la vía quirúrgica, así como recomendaciones técnicas operatorias producto de la experiencia y lo reportado en la literatura. Existen factores propios del cirujano, del contexto y del paciente, que inciden en la resolución del problema. Conclusión. La obstrucción intestinal y sus implicaciones clínicas obligan a una reevaluación constante de su estado del arte y avances en el manejo, tendiente a una búsqueda de oportunidades para impactar favorablemente en su curso clínico. Hay estrategias por implementar, inclusive el manejo laparoscópico en casos seleccionados.

Interpretation discrepancies of abdominal imaging by on-call radiology residents: Evaluation of risk factors

The aim of this study was to determine the rate, important findings, and risk factors related to discrepancies between on-call residents’ and attending radiologists’ interpretations of abdominal examinations. We identified 1132 eligible patients with abdominal radiology findings that were preliminary interpreted by on-call residents between February 2016 and September 2019. The preliminary interpretations were compared with the final interpretations by abdominal attending radiologists, including clinical data. The preliminary interpretations were analyzed by three radiologists in consensus, who categorized the reports according to organs, important findings (i.e., active bleeding, bowel obstruction, organ ischemia or infarction, and organ rupture), clinical outcomes, and discrepancies with respect to final interpretations. Multiple logistic regression analysis was used to evaluate the risk factors for important discrepant findings. Of 1132 patients, the bowel (n = 567, 50.1%) was the most common organ interpreted by on-call residents, followed by gallbladder/bile duct/pancreas (n = 139, 12.3%) and liver (n = 116, 10.2%). Of 1132, 359 patients (31.7%) had disease with 379 important findings: active bleeding (n = 222), organ rupture (n = 77), bowel obstruction (n = 52), bowel ischemia (n = 24), and organ infarction (n = 4). Sixty-four patients (5.6%) showed discrepancies, and 30 (2.6%) showed 32 important discrepant findings comprising 14 active bleeding, 10 bowel obstructions, 6 organ ruptures, and 2 cases of bowel ischemia. Of the 64 discrepant patients, 33 underwent delayed surgery (n = 18, 28.1%) or interventional treatment (n = 15, 23.4%). In multivariable analysis, bowel obstruction (adjusted odds ratio, 2.52; p = 0.049) was an independent risk factor for determining discrepancy between preliminary and final interpretations. The rate of overall and important discrepancies between on-call residents’ and final interpretations was low. However, given that the bowel was the most frequently interpreted organ, bowel obstruction was identified as a risk factor for discrepant interpretations. The identified risk factor and findings may be useful for residents to minimize discrepancies.

Preoperative prediction of inadvertent enterotomy during adhesive small bowel obstruction surgery using combination of CT features

OBJECTIVES

The purpose of this study was to identify the preoperative CT features that are associated with inadvertent enterotomy (IE) during adhesive small bowel obstruction (ASBO) surgery.

METHODS

From January 2015 to December 2019, all patients with ASBO who underwent an abdominal CT were reviewed. Abdominal CT were retrospectively reviewed by two radiologists with a consensus read in case of disagreement. IE during ASBO surgery was retrospectively recorded. Univariate and multivariate analyses of CT features associated with IE were performed and a simple CT score was built to stratify the risk of IE. This score was validated in an independent retrospective cohort. Abdominal CT of the validation cohort was reviewed by a third independent reader.

RESULTS

Among the 368 patients with ASBO during the study period, 169 were surgically treated, including 129 ASBO for single adhesive band and 40 for matted adhesions. Among these, there were 47 IE. By multivariate analysis, angulation of the transitional zone (OR = 4.19, 95% CI [1.10-18.09]), diffuse intestinal adhesions (OR = 4.87, 95% CI [1.37-19.76]), a fat notch sign (OR = 0.32, 95% CI [0.12-0.85]), and mesenteric haziness (OR = 0.13, 95% CI [0.03-0.48]) were independently associated with inadvertent enterotomy occurrence. The simple CT score built to stratify risk of IE displayed an AUC of 0.85 (95% CI [0.80-0.90]) in the study sample and 0.88 (95% CI [0.80-0.96]) in the validation cohort.

CONCLUSION

A simple preoperative CT score is able to inform the surgeon about a high risk of IE and therefore influence the surgical procedure.

KEY POINTS

• In this retrospective study of 169 patients undergoing abdominal surgery for adhesive small bowel obstruction, 47 (28%) inadvertent enterotomy occurred. • A simple preoperative CT score enables accurate stratification of inadvertent enterotomy risk (area under the curve 0.85). • By multivariable analysis, diffuse intestinal adhesions and angulation of the transitional zone were predictive of inadvertent enterotomy occurrence.

Dual-energy CT of acute bowel ischemia

Acute bowel ischemia is a condition with high mortality and requires rapid intervention to avoid catastrophic outcomes. Swift and accurate imaging diagnosis is essential because clinical findings are commonly nonspecific. Conventional contrast enhanced CT of the abdomen has been the imaging modality of choice to evaluate suspected acute bowel ischemia. However, subtlety of image findings and lack of non-contrast or arterial phase images can make correct diagnosis challenging. Dual-energy CT provides valuable information toward assessing bowel ischemia. Dual-energy CT exploits the differential X-ray attenuation at two different photon energy levels to characterize the composition of tissues and reveal the presence or absence of faint intravenous iodinated contrast to improve reader confidence in detecting subtle bowel wall enhancement. With the same underlying technique, virtual non-contrast images can help to show non-enhancing hyperdense hemorrhage of the bowel wall in intravenous contrast-enhanced scans without the need to acquire actual non-contrast scans. Dual-energy CT derived low photon energy (keV) virtual monoenergetic images emphasize iodine contrast and provide CT angiography-like images from portal venous phase scans to better evaluate abdominal arterial patency. In Summary, dual-energy CT aids diagnosing acute bowel ischemia in multiple ways, including improving visualization of the bowel wall and mesenteric vasculature, revealing intramural hemorrhage in contrast enhanced scans, or possibly reducing intravenous contrast dose.

Surgical management of adhesive small bowel obstruction: Is it still mandatory to wait? - An update

Small bowel obstruction syndromes (SBO) represent one of the main causes of emergency admission for surgical abdominal pain. The 2018 Bologna Guidelines (Ten Broek et al. 2018) recommend non-operative management at the outset if there are no signs of severity; surgery is proposed after 72h for the 20-30% of patients who fail medical management. However, these recommendations were based on old studies published at a time when laparoscopic surgery was not commonplace and when diagnostic capabilities (particularly for establishing etiology) were less developed than they are today. Additionally, the advent and development of laparoscopy and enhanced rehabilitation after surgery have led to a decrease in surgical morbidity. These guidelines are therefore now debated and several recent publications have encouraged urgent or semi-urgent surgical management for patients presenting for SBO in order to reduce morbidity, mortality, duration of hospitalization and costs, and to improve the feasibility of therapeutic laparoscopy. Prompt surgical management could also reduce the risk of recurrent small bowel obstructions. This model for early surgical management probably cannot be applied to all patients. It therefore seems important to select those patients at risk for failure of medical treatment and to identify those in whom the probability of successful laparoscopy is high. New radiological tools should allow better selection in the future. At the present time, the indications for early surgery "within 24h" should be emphasized.

Adhesion-related small bowel obstruction: deep learning for automatic transition-zone detection by CT

Background

To train a machine-learning model to locate the transition zone (TZ) of adhesion-related small bowel obstruction (SBO) on CT scans.

Materials and methods

We used 562 CTs performed in 2005–2018 in 404 patients with adhesion-related SBO. Annotation of the TZs was performed by experienced radiologists and trained residents using bounding boxes. Preprocessing involved using a pretrained model to extract the abdominopelvic region. We modeled TZ localization as a binary classification problem by splitting the abdominopelvic region into 125 patches. We then trained a neural network model to classify each patch as containing or not containing a TZ. We coupled this with a trained probabilistic estimation of presence of a TZ in each patch. The models were first evaluated by computing the area under the receiver operating characteristics curve (AUROC). Then, to assess the clinical benefit, we measured the proportion of total abdominopelvic volume classified as containing a TZ for several different false-negative rates.

Results

The probability of containing a TZ was highest for the hypogastric region (56.9%). The coupled classification network and probability mapping produced an AUROC of 0.93. For a 15% proportion of volume classified as containing TZs, the probability of highlighted patches containing a TZ was 92%.

Conclusion

Modeling TZ localization by coupling convolutional neural network classification and probabilistic localization estimation shows the way to a possible automatic TZ detection, a complex radiological task with a major clinical impact.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13244-021-01150-y.

Added value of iodine-specific imaging and virtual non-contrast imaging for gastrointestinal assessment using dual-energy computed tomography

Dual-energy computed tomography (DECT) has become increasingly available and can be readily incorporated into clinical practice. Although DECT can provide a wide variety of spectral imaging reconstructions, most clinically valuable information is available from a limited number of standard image reconstructions including virtual non-contrast and iodine overlay. The combination of these standard reconstructions can be used for specific diagnostic tasks that provide added value over traditional CT protocols. In this pictorial essay, the added value of these standard reconstructed images will be demonstrated by case examples for diseases specifically related to the gastrointestinal system.

Surgical treatment of mechanical bowel obstruction: characteristics and outcomes of geriatric patients compared to a younger cohort

PURPOSE

Mechanical bowel obstruction (MBO) is one of the most common indications for emergency surgery. Recent research justifies the method of attempting 3-5 days of nonoperative treatment before surgery. However, little is known about specific characteristics of geriatric patients undergoing surgery compared to a younger cohort. We aimed to analyze patients with MBO that required surgery, depending on their age, to identify potential targets for use in the reduction in complications and mortality in the elderly.

METHODS

Thirty-day and in-hospital mortality were determined as primary outcome. We retrospectively identified all patients who underwent surgery for MBO at the University Hospital of Bonn between 2009 and 2019 and divided them into non-geriatric (40-74 years, n = 224) and geriatric (≥ 75 years, n = 88) patients, using the chi-squared-test and Mann-Whitney U test for statistical analysis.

RESULTS

We found that geriatric patients had higher 30-day and in-hospital mortality rates than non-geriatric patients. As secondary outcome, we found that they experienced a longer length of stay (LOS) and higher complication rates than non-geriatric patients. Geriatric patients who suffered from large bowel obstruction (LBO) had a higher rate of bowel resection, stoma creation, and a higher 30-day mortality rate. The time from admission to surgery was not shown to be crucial for the outcome of (geriatric) patients.

CONCLUSION

Geriatric patients suffering from mechanical bowel obstruction that had to undergo surgery had higher mortality and morbidity than non-geriatric patients. Especially in regard to geriatric patients, clinicians should treat patients in a risk-adapted rather than time-adapted manner, and conditions should be optimized before surgery.

Evaluation of ischemia and necrosis in adhesive small bowel obstruction based on CT signs: Subjective visual evaluation and objective measurement

PURPOSE

To investigate the diagnostic performance of CT signs for detecting bowel ischemia and necrosis in adhesive small bowel obstruction(SBO) with subjective and objective methods.

MATERIALS AND METHODS

113 adhesive SBO patients were enrolled and divided into ischemic group (49 cases in necrotic group and 35 cases in reversible ischemic group) and non-ischemic group (29 cases) according to the operation results. Subjective visual assessment of CT signs associated with ischemia and necrosis was performed by two radiologists independently. Elevated unenhanced attenuation and enhancement value of involved bowel wall were objectively measured and compared by single factor analysis of variance. Cut-off value and diagnostic performance were evaluated by receiver operating characteristic curve (ROC).

RESULTS

Closed-loop mechanism, reduced bowel wall enhancement, and mesenteric edema were associated with bowel ischemia, with sensitivity of 81.0%, 65.5%, 75.0%, and specificity of 86.2%, 96.6%, 89.7%, respectively. Increased unenhanced bowel wall attenuation was a specific sign for necrosis with 100.0% specificity and 51.0% sensitivity. The sensitivity and specificity for ischemia were 86.0% and 91.9% with cut-off enhancement value lower than 33.5 HU. The sensitivity and specificity for necrosis were 58.2% and 100.0% with cut-off elevated unenhanced attenuation higher than 16.5 HU, 86.7% and 83.3% with cut-off enhancement value lower than 21.5 HU.

CONCLUSION

Reduced bowel wall enhancement and increased unenhanced bowel wall attenuation were good indicators of bowel ischemia and necrosis. The objective measurement of elevated unenhanced attenuation and enhancement value can predict bowel ischemia and necrosis more accurately.

Correlation of CT findings with intra-operative outcome in closed-loop small bowel obstruction (CL-SBO)

PURPOSE

To correlate CT-findings in patients with closed-loop small bowel obstruction (CL-SBO) with perioperative findings, to identify patients who require immediate surgical intervention. Secondary purpose was to substantiate the role of radiologists in predicting perioperative outcome.

METHODS

Data were retrospectively obtained from patients with surgically confirmed CL-SBO, between September 2013 and September 2019. Three radiologists reviewed CTs to assess defined CT features and predict patient outcome for bowel wall ischemia and necrosis using a likelihood score. Univariate statistical analyses were performed and diagnostic performance parameters and interobserver agreement were assessed for each feature.

RESULTS

Of 148 included patients, 28 (19%) intraoperatively had viable bowel and 120 (81%) had bowel wall ischemia or necrosis. Most CT characteristics, as well as the likelihood of ischemia and necrosis, found fair or moderate multirater agreement. Increased attenuation of bowel wall and mesenteric vessels on non-contrast-enhanced CT had a specificity for bowel ischemia or necrosis of 100% (sensitivity respectively 48% (p < 0.001) and 21% (p = 0.09)). Mesenteric edema had high sensitivity for ischemia or necrosis (90%), but specificity of only 26% (p < 0.001). For mesenteric fluid, sensitivity was 60% and specificity 57% (p = 0.004). Decreased enhancement of bowel wall in both arterial and PV-phase showed significant correlation, respectively a sensitivity of 58% and 42%, and specificity of 88% and 79% (both p < 0.001). Likelihood of both ischemia and necrosis were significantly correlated with perioperative outcome (p < 0.001).

CONCLUSION

CT findings concerning mesenteric and bowel wall changes, as well as radiologists' judgement of likelihood of ischemia and necrosis are significantly correlated with perioperative outcome of bowel wall ischemia and necrosis in patients with CL-SBO.

Many faces of acute bowel ischemia: overview of radiologic staging

Acute bowel ischemia (ABI) can be life threatening with high mortality rate. In spite of the advances made in diagnosis and treatment of ABI, no significant change has occurred in the mortality over the past decade. ABI is potentially reversible with prompt diagnosis. The radiologist plays a central role in the initial diagnosis and preventing progression to irreversible intestinal ischemic injury or bowel necrosis. The most single imaging findings described in the literature are either non-specific or only present in the late stages of ABI, urging the use of a constellation of features to reach a more confident diagnosis. While ABI has been traditionally categorized based on the etiology with a wide spectrum of imaging findings overlapped with each other, the final decision for patient’s management is usually made on the stage of the ABI with respect to the underlying pathophysiology. In this review, we first discuss the pathologic stages of ischemia and then summarize the various imaging signs and causes of ABI. We also emphasize on the correlation of imaging findings and pathological staging of the disease. Finally, a management approach is proposed using combined clinical and radiological findings to determine whether the patient may benefit from surgery or not.

Clinical Features of Ischemic Enteritis Diagnosed by Double-Balloon Endoscopy

INTRODUCTION

Ischemic enteritis (IE) is a relatively rare small bowel disease that is diagnosed via double-balloon endoscopy (DBE), although the lack of established diagnostic criteria can make it difficult to confirm the diagnosis. This study aimed to describe the clinical characteristics, endoscopic imaging features, and treatments for IE at our center. Patients and Methods. We retrospectively searched the DBE database (1,521 patients) at Nagoya University Hospital for patients with IE and collected data regarding endoscopic findings, clinical background, and histological findings. The cases were categorized according to whether they involved transient or stenotic IE.

RESULTS

The DBE database included 24 patients (14 men) with IE. Transient IE was identified in 9 patients, and stenotic IE was identified in 15. Half of the patients had a history of cerebrovascular and cardiovascular disease. A granular structure at the ulcer base was the most frequently observed DBE finding at the stenotic site. Enterography using the contrast medium revealed that transient IE had a similar stenotic lesion length, relative to stenotic IE, although stenotic IE had a significantly higher stenosis ratio (81% vs. 63%, P=0.033). Small bowel enteroclysis revealed the "lead pipe" sign (11 patients), thumbprinting (3 patients), and the serrated lumen sign (1 patient). Only 1 patient with stenotic IE experienced recurrence after conservative treatment.

CONCLUSION

During DBE, IE was characterized by cannular stenosis with extended and variable ulceration types, which spread over the edge of the stenosis, and a granular appearance at the ulcer base. These findings may help guide the diagnosis of IE.

Ultrasound of Small Bowel Obstruction: A Pictorial Review

Small bowel obstruction (SBO) is a common condition requiring urgent attention that may involve surgical treatment. Imaging is essential for the diagnosis and characterization of SBO because the clinical presentation and results of laboratory tests may be nonspecific. Ultrasound is an excellent initial imaging modality for assisting physicians in the rapid and accurate diagnosis of a variety of pathologies to expedite management. In the case of SBO diagnosis, ultrasound has an overall sensitivity of 92% (95% CI: 89–95%) and specificity of 93% (95% CI: 85–97%); the aim of this review is to examine the criteria for the diagnosis of SBO by ultrasound, which can be divided into diagnostic and staging criteria. The diagnostic criteria include the presence of dilated loops and abnormal peristalsis, while the staging criteria are represented by parietal and valvulae conniventes alterations and by the presence of free extraluminal fluid. Ultrasound has reasonably high accuracy compared to computed tomography (CT) scanning and may substantially decrease the time to diagnosis; moreover, ultrasound is also widely used in the monitoring and follow-up of patients undergoing conservative treatment, allowing the assessment of loop distension and the resumption of peristalsis.

Influence of clinical suspicion on CT accuracy of acute mesenteric ischemia: Retrospective study of 362 patients

PURPOSE

Acute mesenteric ischemia (AMI) may be underdiagnosed when not clinically suspected before CT is performed. We assessed the influence of a clinical suspicion of AMI on the CT accuracy.

METHOD

This retrospective single-centre study included patients who underwent CT in 2014-2019 and had clinically suspected AMI and/or confirmed AMI. CT protocols were adapted based on each patient's presentation and on findings from unenhanced images. The CT protocol was considered optimal for AMI when it included arterial and portal venous phases. CT protocols, accuracy of reports, and outcomes were compared between the groups with and without suspected AMI before CT.

RESULTS

Of the 375 events, 337 (90 %) were suspected AMI and 66 (18 %) were AMI, including 28 (42 %) with and 38 without suspected AMI. These two groups did not differ significantly regarding the medical history, clinical presentation, or laboratory tests. The CT protocol was more often optimal for AMI in the group with suspected AMI (26/28 [93 %] vs. 28/38 [74 %], p = 0.046). Diagnostic accuracy was not different between groups with and without suspected AMI (26/28 [93 %] vs. 34/38 [90 %], p = 1.00). However, it was lower in the group without suspicion of AMI when the CT protocol was not optimal for AMI (27/28 [96 %] vs 7/10 [70 %], p = 0.048).

CONCLUSIONS

The negative influence of not clinically suspecting AMI can be mitigated by using a tailored CT protocol.

Management of abdominal emergencies in adults using telemedicine and artificial intelligence

The terms "telemedicine" and "artificial intelligence" (AI) are used today throughout all fields of medicine, with varying degrees of relevance. If telemedicine corresponds to practices currently being developed to supply a high quality response to medical provider shortages in the general provision of healthcare and to specific regional challenges. Through the possibilities of "scalability" and the "augmented physician" that it has helped to create, AI may also constitute a revolution in our practices. In the management of surgical emergencies, abdominal pain is one of the most frequent complaints of patients who present for emergency consultation, and up to 20% of patients prove to have an organic lesion that will require surgical management. In view of the very large number of patients concerned, the variety of clinical presentations, the potential seriousness of the etiological pathology that sometimes involves a life-threatening prognosis, healthcare workers responsible for these patients have logically been led to regularly rely on imaging examinations, which remain the critical key to subsequent management. Therefore, it is not surprising that articles have been published in recent years concerning the potential contributions of telemedicine (and teleradiology) to the diagnostic management of these patients, and also concerning the contribution of AI (albeit still in its infancy) to aid in diagnosis and treatment, including surgery. This review article presents the existing data and proposes a collaborative vision of an optimized patient pathway, giving medical meaning to the use of these tools.

Non-strangulated adhesive small bowel obstruction: CT findings predicting outcome of conservative treatment

OBJECTIVES

To clarify CT findings that predict outcome of conservative treatment in patients with non-strangulated adhesive small bowel obstruction (SBO).

METHODS

Unenhanced and contrast-enhanced abdominopelvic CT studies in 189 patients with adhesive SBO who had initial conservative treatment were reviewed. The CT findings included transition zone, beak signs, maximum bowel diameter, bowel diameter ratio, decreased bowel wall enhancement, increased unenhanced bowel wall attenuation, anterior parietal adhesion, bowel wall thickening, closed-loop obstruction, small bowel feces sign, whirl sign, mesenteric haziness, mesenteric, peritoneal fluid, and submucosal edema. These findings were statistically compared according to the success or failure of treatment.

RESULTS

Conservative treatment succeeded in 144 patients (76.2%) and failed in 45 patients (23.8%). At multivariate analysis, the lack of small bowel feces sign, focal, diffuse mesenteric haziness, and moderate amount of mesenteric fluid were independent findings predicting failure of conservative treatment, with odds ratios of 5.23, 5.5, 13.55, and 4.89, respectively. The presence of all significant findings showed a high specificity of 97.2% with positive likelihood ratio of 8.8. If CT scans showed none of the three significant findings, the negative predictive value was 97.6% and negative likelihood ratio was 0.08.

CONCLUSIONS

The lack of small bowel feces sign, focal, diffuse mesenteric haziness, and moderate amount of mesenteric fluid are independent CT findings predicting the failure of conservative treatment in patients with non-strangulated adhesive SBO. The combination of all CT findings suggests the need for surgery; absence of two or all CT findings should suggest an attempt for conservative treatment.

KEY POINTS

• To minimize delayed operation, it is important to identify non-strangulated adhesive small bowel obstruction patients in whom initial conservative treatment is likely to fail. • The lack of small bowel feces sign, the presence of mesenteric haziness, and a moderate amount of mesenteric fluid are independent factors predicting the failure of conservative treatment in patients with non-strangulated adhesive small bowel obstruction. • The combination of all three CT findings suggests the need for surgery; absence of two or all three CT findings should suggest an attempt for conservative treatment.