Sonographic Evaluation of GI Perforation Eric schwartz

GI Perforation Various causes that require early recognition and, frequently, emergent surgical treatment: peptic ulcer inflammatory disease blunt or penetrating trauma iatrogenic factors foreign body neoplasm

U/S as an initial diagnostic test Reported sensitivity varies between studies One report indicates a sensitivity of 76% vs 92% for radiography Another found a sensitivity of 93% vs 79% for radiography An experienced sonographer may detect as little as 2 mL of intraperitoneal free air (IFA) CXR can detect 1 mL IFA under the right hemidiaphragm if performed with pt in upright position; however, pt’s with severe abdominal pain often cannot tolerate upright CXR.

Utility Potentially useful as an initial ED test in patient groups where radiation burden should be limited (i.e. children and pregnant women) U/S is less expensive and more readily available than CT; may be a useful tool for initial workup, allowing CT to be reserved for nondiagnostic studies. May be useful as an adjunct to CXR

Procedure Patients should be first scanned in the supine position concentrating on the midline and right upper quadrant IFA typically appears as an enhanced peritoneal stripe accompanied by posterior reverberation artifact with characteristic comet-tail appearance Next, patients should be scanned in the left lateral decubitus position The enhanced peritoneal stripe will move when the patient changes position

Sagittal sonographic section of the RUQ using a curvilinear probe showing enhanced peritoneal stripe (empty arrow) and reverberation artifacts (small arrows) which partially obscure the right lobe of the liver (L) and right kidney (K). Laparotomy confirmed perforated diverticulitis

Findings may be subtle Jejunum perforation with free intraperitoneal gas after trauma

Air Bubbles Reverberation artifact may not be seen in small air collections. Trapped air bubbles in ascitic fluid or in a localized fluid collection will appear as hyperechoic foci

Transverse sonographic section of the RUQ using a linear probe showing a hyperechoic focus (arrow head) moving within a fluid collection. Laparotomy confirmed that the patient had a perforated duodenal ulcer

Determining etiology via U/S Detection of intraperitoneal free or localized fluid collections can be seen in perforated peptic ulcer or perforated appendix. Thickened bowel or gall bladder wall and decreased bowel motility or ileus may point toward a peritoneal inflammatory process that can be associated with perforation of diverticulitis or small bowel perforation. Lymph node metastasis may be seen in perforated tumors of the gastrointestinal tract.

Sagittal section of the RUQ using a curvilinear probe showing an interrupted hyperechoic line under the liver in Morrison's pouch (arrow head), fluid collection (white arrow), and a hyperechoic line in the anterior wall of the duodenum representing the scar of a duodenal ulcer (black arrow). Laparotomy confirmed that the patient had a perforated duodenal ulcer

Optimizing detection of IFA Use a linear probe (10-12 MHz) for detecting IFA because of its higher resolution in the near field where air accumulates. IFA is best detected in the right upper quadrant between the anterior abdominal wall and liver where there is no intervening bowel. The presence of air in abnormal sites such as along with the fissure of ligamentum teres and Morrison's pouch should raise the suspicion of IFA.

Optimizing detection of IFA In morbidly obese patients, visualization of enhanced peritoneal stripe can be facilitated by having the patient take a deep breath. This helps differentiate between the enhanced peritoneal stripe and the moving intraperitoneal fat and bowel. To avoid artifacts resulting from the adjacent lung, scan the RUQ both during inspiration and expiration. The shadows produced by the intervening ribs originate above the peritoneal line and move with respiration.

Optimizing detection of IFA In pt’s with inconclusive scans, but high clinical suspicion for perforated bowel, repeat scans should be performed as more free air may accumulate over time

Drawbacks May be difficult to detect, even for experienced sonographers Pneumoperitoneum can be mistaken for bowel gas, or vice versa Sensitivity is significantly less when using older machines with lower resolution Difficult in obese patients and trauma pt’s with subcutaneous emphysema Pt’s with severe abdominal pain may not be able to tolerate exam

Conclusion Ultrasound may be useful as an initial diagnostic test, allowing CT to be reserved for patients with nondiagnostic U/S results Repeating scans over time may improve detection, but sick pt’s p/w symptoms consistent with perforation are likely to receive CT anyway Sensitivity of the exam is highly operator dependent as sonographic findings of perforation may be subtle Further research required to determine actual utility in the ED setting

References Blaivas M, Kirkpatrick AW, Rodriguez-Galvez M, Ball CG. Sonographic depiction of intraperitoneal free air. J Trauma. 2009;67:675. Chadha D, Kedar RP, Malde HM. Sonographic detection of pneumoperitoneum: An experimental and clinical study. Australas Radiol. 1993;37:182–5. Chen SC, Wang HP, Chen WJ, Lin FY, Hsu CY, Chang KJ, et al. Selective use of ultrasonography for the detection of pneumoperitoneum. Acad Emerg Med. 2002;9:643–5. Muradali D, Wilson S, Burns PN, Shapiro H, Hope-Simpson D. A specific sign of pneumoperitoneum on sonography: Enhancement of the peritoneal stripe. AJR Am J Roentgenol. 1999;173:1257–62. Nurberg D, Mauch M, Spengler J, Holle A, Pannwitz H, Seitz K (2007) Sonographical diagnosis of pneumoretroperitoneum as a result of retroperitoneal perforation. Ultraschall med 28(6):612-21. Seitz K, Reising KD (1982) Ultrasound detection of free air in the abdominal cavity. Ultraschall Med 3(1):4-6.