Duration and Clinical Significance of Radiographically Detected “Free Air” After Laparoscopic Nephrectomy:

Pneumomediastinum and pneumoperitoneum on computed tomography after peroral endoscopic myotomy (POEM): postoperative changes or complications?

BACKGROUND

Many of the acute alterations after peroral endoscopic myotomy (POEM) may be of little clinical significance, while others may herald major clinical problems. The question whether pneumomediastinum/pneumoperitoneum is a normal postoperative finding after POEM, or should be regarded as a sign of a complication needs to be evaluated. Familiarity with these findings in computed tomography (CT) is essential for radiologists.

PURPOSE

To evaluate whether or not pneumomediastinum/pneumoperitoneum detected by chest CT is a sign of a complication after POEM using CO2 insufflation for esophageal achalasia.

MATERIAL AND METHODS

One hundred and eight patients with esophageal achalasia who underwent chest CT within 30 hours after POEM were included. CT findings were retrospectively reviewed by two radiologists in consensus. The correlation between pneumomediastinum and/or pneumoperitoneum shown on CT and the development of complications was analyzed.

RESULTS

Abnormal findings were identified on post-treatment CT, including pneumomediastinum and/or pneumoperitoneum (53.7%, 58/108), pneumothorax (0.9%, 1/108), subcutaneous emphysema (29.6%, 32/108), pleural effusion (69.4%, 75/108), segmental atelectasis of lung tissue (29.6%, 32/108), minor inflammation of lungs (69.4%, 75/108), and ascites (0.9%, 1/108). Pneumomediastinum and pneumoperitoneum were observed simultaneously in 29 cases. The incidence rate of mild complications was high (79.6%, 86/108), while the rate of severe complications was low (2.8%, 3/108). There was no significant correlation between the occurrence of pneumomediastinum and/or pneumoperitoneum on CT and the development of complications (P = 0.542), or the development of severe complications including delayed hemorrhage, esophageal perforation, and retroperitoneal abscess.

CONCLUSION

Pneumomediastinum and pneumoperitoneum detected by CT occur frequently after POEM and may be regarded as normal postoperative changes.

Multidetector CT imaging of complications after laparoscopic nephron-sparing surgery

Purpose

Laparoscopic nephron-sparing surgery (L-NSS) is increasingly performed to treat localised renal lesions. However, the associated morbidity is non-negligible, with a rate of major complications approaching 10 %.

Methods and Results

This paper provides an overview of indications, surgical techniques and results of L-NSS; explains the incidence, risk factors and manifestations of postoperative complications; discusses the preferred multidetector computed tomography (CT) acquisition techniques; illustrates the appearance of normal postoperative images following L-NSS; and reviews, with example images, the most common and unusual iatrogenic complications. These include haematuria, haemorrhage, vascular injuries, infections and urinary leaks. Most emphasis is placed on CT, which provides rapid, reliable triage and follow-up of iatrogenic complications after L-NSS, identifying occurrences that require transarterial embolisation or repeated surgery.

Conclusions

Multidetector CT allows precise assessment of the surgical resection site; detection of pneumoperitoneum and subcutaneous emphysema; quantification of retroperitoneal blood; and identification of active bleeding, pseudoaneurysms, arterio-venous fistulas, abscess collections and extravasated urine.

Teaching Points

• Laparoscopic nephron-sparing surgery (NSS) is increasingly performed to treat renal lesions.

• Radiologists are increasingly requested to investigate suspected post-surgical NSS complications.

• Post-NSS complications include haemorrhage, haematuria, vascular injuries, infections and urinary leaks.

• Multidetector CT allows choice between conservative treatment, transarterial embolisation or surgery.

Common postoperative findings unique to laparoscopic surgery

The interpretation of images obtained in patients who have recently undergone abdominal or pelvic surgery is challenging, in part because procedures that were previously performed with open surgical techniques are increasingly being performed with minimally invasive (laparoscopic) techniques. Thus, it is important to be familiar with the normal approach used for laparoscopic surgeries. The authors describe the indications for various laparoscopic surgical procedures (eg, cholecystectomy, appendectomy, hernia repair) as well as normal postoperative findings. For example, port site hernias are more commonly encountered in patients with trocar sites greater than 10 mm and occur at classic entry sites (eg, the periumbilical region). Similarly, preperitoneal air can be encountered postoperatively, often secondary to trocar dislodgement during difficult entry or positioning. In addition, intraperitoneal placement of mesh during commonly performed ventral or incisional hernia repairs typically leads to postoperative seroma formation. Familiarity with normal findings after commonly performed laparoscopic surgical procedures in the abdomen and pelvis allows accurate diagnosis of common complications and avoidance of diagnostic pitfalls.

Diagnostic value of abdominal free air detection on a plain chest radiograph in the early postoperative period: a prospective study in 648 consecutive patients who have undergone abdominal surgery

BACKGROUND

To the best of our knowledge, this is the first study to evaluate the predictive value of free air (on a plain radiograph) for bowel perforation in a large prospective cohort of surgical patients.

METHODS

All consecutive patients undergoing abdominal surgery between January 2011 and June 2012 were screened for this study. We performed an upright chest radiograph on the second and third postoperative day. Thereafter, additional radiographic evaluations were performed every 2 days until the disappearance of abdominal free air.

RESULTS

Of the 648 subjects enrolled in our study, free abdominal air was found in 65 subjects on the first radiographic evaluation (2 days after surgery), 51 on the second (3 days after surgery), three on the third (5 days after surgery), and none on the fourth (7 days after surgery). The presence of free abdominal air was associated with an increased risk of gastrointestinal perforation. The presence of free air was associated with a hazard ratio (HR) of 21.54 (95% CI 9.66-48.01, p<0.001) and a HR of 23.87 (95% CI 10.68-53.34, p<0.001) at 2 and 3 days after surgery, respectively. Sensitivity, specificity, positive predictive value, and negative predictive value were 70, 93, 33, and 98%, respectively, at 2 days after surgery, and similar results were confirmed at 3 days after surgery.

CONCLUSION

We believe that the presence of free air at 3 days after surgery should not be considered a common finding. Here, we demonstrate that the detection of free air has a remarkable predictive value for gastrointestinal perforation, which has been overestimated in previous experience.