Transabdominal ultrasonography of the small bowel

Abstract

In the era of double balloon enteroscopy, capsule endoscopy, CT, and MRI enterography is transabdominal ultrasonography (TUS) underestimated method for evaluation of small bowel pathology. As often initial imagine method in abdominal complaints, nowadays has TUS much better diagnostic potential than two decades ago. High-resolution ultrasound probes with harmonic imaging significantly improve resolution of bowel wall in real time, with possibility to asses bowel peristalsis. Color flow doppler enables evaluation of intramural bowel vascularisation, pulse wave doppler helps to quantificate flow in coeliac and superior mesenteric arteries. Small intestine contrast ultrasonography with oral contrast fluid, as well as contrast enhanced ultrasonography with intravenous microbubble contrast also improves small bowel imaging. We present a review of small intestine pathology that should be detected during ultrasound examinations, discuss technical requirements, advantages and limitations of TUS, typical ultrasound signs of Crohn's disease, ileus, celiac disease, intussusception, infectious enteritis, tumours, ischemic and haemorrhagic conditions of small bowel. In the hands of experienced investigator, despite some significant limitations(obesity, meteorism), is transabdominal ultrasonography reliable, noninvasive and inexpensive alternative method to computerised tomography (CT) and magnetic resonance imaging (MRI) in small bowel examination.

Figure 1

Normal small bowel: (a) Transverse view of pars horizontalis duodeni between aorta and SMA. (b) Longitudinal view of jejunum in left mesogastrium—with numerous valvulae conniventes. (c) Longitudinal section of terminal ileum (TI) in the left iliac fossa without and with compression by the probe (d). A—transverse view of appendix. All with high resolution probe.

Figure 2

TUS in Crohn's disease. (a) Transversal view of thickened terminal ileum with preserved stratification and intramural hyper-vascularisation—High resolution probe. (b) Transversal section of two ileal bowel loops—proximal (left) with segmentally impaired stratification, distal with complete absence of stratification with hypoechogenic wall. The right half of picture shows intramural hyper-vascularisation especially in proximal loop, indicating active inflammation—High resolution probe. (c) Transversal view of terminal ileum with hypoechogenic bridge through echogenic submucosa between lumen and outer surface of the wall indicating transmural ulcer (arrow) and thickened inflamed “wrapping” fat (F)—High resolution probe. (d) Blind fistula wrapped by inflamed fat. Increased intramural vascularisation in color-Power Doppler (CFD)—High resolution probe. (e) Segmental absence of echogenic submucosa indicates longitudinal ulcer of terminal ileum (arrows) in longitudinal and (f) transversal view in a Crohn's ileitis (WF-inflamed fat)-FDsign—High resolution probe.

Figure 3

Crohn's disease complications. (a) Transverse view in lower abdomen shows fistula (white arrow) between terminal ileum/TI) and sigmoid colon (SC), black arrow points to small abscess, high resolution probe. (b) Oblique section of terminal ileum (TI) with blind fistula (thick arrow) into echogenic mesenterial fat and ileovesical fistula (thin arrow). Standard abdominal probe. (c) Stricture of ileum (S) with prestenotic dilatation (D)—standard abdominal probe. (d) TUS with color doppler and peroral contrast—Crohn's terminal ileum stenosis with intramural hypervascularisation (with CFD) indicates inflammatory stenosis—high resolution probe.

Figure 4

Celiac sprue: (a) Dilated loops of small bowel with thickened wall, and valvulae conniventes hyperperistalsis—standard abdominal probe. (b) Intussusception of jejunum in transverse (left) and longitudinal section in celiac sprue—high resolution probe. (c) Dilated SMA (9 mm) in a patient with untreated celiac disease—standard probe. (d) Low resistive index-RI (0.69) in SMA in untreated celiac disease—standard probe.

Figure 5

Tumors of small bowel. (a) Solid oval tumor in the lumen of terminal ileum with hypervascularisation in CFD (a) High resolution probe. (b) Endoscopic picture of tumor of terminal ileum in the same case-histologically carcinoid. (c) Oval solid tumor in D2 segment of duodenum—Standard abdominal probe. (d) Endoscopic view in the same case—histologically metastasis of Grawitz tumor (years after nephrectomy for tumor). (e) Longitudinal section of thickened small bowel loop (S) with stenosis and dilatation (D) of lumen. Standard abdominal probe. (f)Transversal view with high resolution probe in dilated segment shows hypervascularisation of thickened wall (f). Surgery confirmed suspected T-lymphoma of jejunum in untreated celiac disease.

Figure 6

Vascular diseases of SB. (a) Fatal Thromboembolia of SMA in a patient with atrial fibrillation, with standard abdominal probe—absence of colour signal in embolised segment (arrows). (b) Use of high resolution probe in the same case. (c) Transversal view of jejunal loop without peristalsis, with thickened, avascular wall—another patient with SMA thromboembolia—but with presence of flow in proximal segment of SMA. High resolution probe. (e) Significant stenosis of SMA/Vmax over 400 cm/sek (>70%) in a patient with ischemic colitis. Standard probe.

Figure 7

(a) Gallstone ileus—oval reflex with acoustic shadow in dilated jejunum. Standard probe. (b) Intussusception of jejunum. High resolution probe. (c) Spontaneous jejunal haematoma—transverse view of thickened hypoechogenic jejunal loops with absence of vascularization (in CFD)—arrows. Dotted arrow point to small peritoneal fluid. Patient in the hypocoagulation state, high resolution probe. (d) Spontaneous bowel haematoma transverse section of thickened jejunal loops with preserved stratification and narrowed lumen in a patient with hemophilia—(arrows)—standard probe. (e) longitudinal view of thickened terminal ileum (TI) and Bauhin's valve (arrow) with hypervascularisation of bowel wall (Yersinia ileocolitis)—high resolution probe. (f) Mesenterial lymphadenitis in the right iliac fossa in the same case—high resolution probe.