Cloie June Chiong
A 37 year old male with a past medical history of ulcerative colitis, now status-post total abdominal colectomy with a creation of end ileostomy, left-sided ureteral lysis due to retroperitoneal fibrosis, robotic-assisted proctectomy with creation of an ileoanal pouch and diverting loop ileostomy, extensive lysis of adhesions and right-sided ureterolysis, and ileostomy takedown in 2024 presents to the ED with diffuse abdominal pain that began this morning and sweats beginning last night. The pain was 4/10 with rest, 7/10 with standing, and 8/10 with ambulation. The pain radiated to the right shoulder this morning while lying in bed. He denied nausea and vomiting. He endorsed intermittent testicular pain, reduced oral intake, and decreased voids, but urinated and defecated without pain. Did not report any abnormal concerns with stool input through anastomosis.
Vitals: BP: 122/78 | Pulse: 78 | Temp: 98.6°F | Resp: 16 | SpO2: 100%
Physical Exam showed a soft, flat, non-distended abdomen. A surgical scar was present. There was generalized abdominal tenderness and guarding throughout the abdomen with palpation, without rebound or rigidity. He had tenderness in the lower quadrants > upper quadrants, left > right. There was no hernia present. The remainder of the physical exam was unremarkable.
Labs: WBC 16.9
A bedside ultrasound was performed on the abdomen:
Figure 1: Pneumoperitoneum
Figure 2: Pouchitis
Discussion:
Pneumoperitoneum, a critical condition marked by the presence of free air in the abdominal cavity, typically arises from a perforated hollow viscus and is a rare yet serious cause of acute abdominal pain1,2. This condition requires immediate surgical intervention due to its potential for high mortality. Detecting serious conditions based on abdominal pain alone during physical examinations is challenging due to low sensitivity. Differential diagnoses for acute abdominal pain may include inflammatory bowel disease complications, intra-abdominal abscesses, perforations, bowel obstructions, mesenteric ischemia, and pancreatitis.
While abdominal X-ray and computed tomography of the abdomen are considered as more conventional standards for imaging, ultrasound also serves as a rapid, radiation-free diagnostic tool for detecting gastrointestinal perforations3. The diagnostic performance of ultrasonography for pneumoperitoneum has shown to have a sensitivity of 93%, accuracy of 90%, specificity of 64%, and positive predictive value of 97%, versus plain radiography (79%, 77%, 64%, and 96%, respectively)4.
One key ultrasonographic finding in cases of gastrointestinal perforation is the presence of the peritoneal stripe sign, which shows equidistant, horizontal or vertical reverberations posterior to the abdominal wall and can extend to the lower edge of the monitor, creating a striped pattern of alternating dark and light hyperechoic lines. A “comet tail” appearance may also be present as a result of reverberation artifacts caused by pockets of free air, which acts as a barrier to ultrasound waves2,5.
An additional technique used in ultrasound for detecting a pneumoperitoneum is the "shifting phenomenon." This involves repositioning the patient to observe the movement of air and the peritoneal stripe sign within the peritoneal cavity, confirming the presence of free air6. The "scissors maneuver" further confirms this technique by placing a linear probe in the right epigastric region without abdominal compression; reverberation artifacts are observed and manipulated by pressing and releasing the caudal end of the probe, showing movement of the free air and reverberation artifacts away from the anterior liver5.
The use of ultrasound not only confirmed the presence of pneumoperitoneum, but also allowed for immediate surgical intervention, underscoring its high sensitivity and the crucial impact of rapid assessment capabilities in emergency settings. Point-of care ultrasound should be considered as a potential first-line form of diagnostic imaging for abdominal perforation.
References:
- Nazerian, P., Tozzetti, C., Vanni, S. et al. Accuracy of abdominal ultrasound for the diagnosis of pneumoperitoneum in patients with acute abdominal pain: a pilot study. Crit Ultrasound J 7, 15 (2015). https://doi.org/10.1186/s13089-015-0032-6
- Chao, A., Gharahbaghian, L., & Perera, P. (2015). Diagnosis of pneumoperitoneum with bedside ultrasound. The western journal of emergency medicine, 16(2), 302. https://doi.org/10.5811/westjem.2014.12.24945
- Jiang L, Wu J, Feng X. The value of ultrasound in diagnosis of pneumoperitoneum in emergent or critical conditions: A meta-analysis. Hong Kong Journal of Emergency Medicine. 2019;26(2):111-117. doi:10.1177/1024907918805668
- Bacci, M., Kushwaha, R., Cabrera, G., & Kalivoda, E. J. (2020). Point-of-Care Ultrasound Diagnosis of Pneumoperitoneum in the Emergency Department. Cureus, 12(6), e8503. https://doi.org/10.7759/cureus.8503
- Taylor, M.A., Merritt, C.H., Riddle, P.J. et al. Diagnosis at gut point: rapid identification of pneumoperitoneum via point-of-care ultrasound. Ultrasound J 12, 52 (2020). https://doi.org/10.1186/s13089-020-00195-2
- Yum, J., Hoffman, T., & Naraghi, L. (2021). Timely Diagnosis of Pneumoperitoneum by Point-of-care Ultrasound in the Emergency Department: A Case Series. Clinical practice and cases in emergency medicine, 5(4), 377–380. https://doi.org/10.5811/cpcem.2021.4.52139