Arterial oxygen desaturation during colonoscopy with sedation is a well-documented complication occurring in 41–50% of patients.1Potential causes for the decrease in oxygen saturation include respiratory depression, older age, increased intraabdominal pressure resulting from air insufflation into the colon, external manipulation of the abdomen, and suppression of airway reflexes resulting in aspiration of gastric contents.1,2 

A 64-yr-old, 82-kg, 5' 1” woman with a history of hypertension, asymptomatic heart murmur, arthritis, diverticulosis, and breast cancer was scheduled for a colonoscopy and polypectomy. Past surgery and recent colonoscopy were tolerated without incident. Propofol sedation was given with the patient in the left lateral decubitus position. Air insufflation of the colon was done as part of routine practice. Forty-five minutes into the procedure, the patient began coughing and the pulse oxygen saturation decreased to 85%. A small amount of clear secretions was suctioned from the oropharynx and the patient was given 100% oxygen by mask. The pulse oxygen saturation increased to 93–95% but decreased breath sounds and wheezing were noted in all lung fields. The patient was given albuterol and 100% oxygen by face mask and transported to the postanesthesia care unit. A portable chest radiograph obtained in the postanesthesia care unit showed extensive herniation of the entire stomach and portions of the colon into the chest cavity (fig. 1). The cardiac silhouette was obscured by a large transdiaphragmatic hernia. A follow-up chest radiograph showed an infiltrate consistent with aspiration pneumonia and a slight decrease in the size of the colonic loops within the chest cavity. On further review of the case, an earlier chest radiograph was uncovered showing herniation of the stomach and colon but to a lesser extent. The patient was asymptomatic, had had an uneventful colonoscopy, and did not reveal this information in preoperative assessment. The patient was discharged home on the third hospital day after receiving antibiotic treatment for a clinical diagnosis of postcolonoscopy aspiration pneumonia, although compression atelectasis could have also accounted for similar symptoms.

Transdiaphragmatic hernias are most often the result of blunt (5%) or penetrating (10%) trauma and less so as varying sizes of hiatal hernias.3,4There are case reports of transdiaphragmatic hernia first discovered during colonoscopy.5,6In one case, the patient developed acute respiratory distress with resulting fatal tension pneumothorax.5In another case, the patient had extensive bowel herniation into the chest cavity with incarceration that required emergency surgical intervention.6Approximately 25% of all people over the age of 50 have a hiatal hernia. Transdiaphragmatic hernia, in contrast, is more pronounced and often involves herniation of stomach and bowel into the chest. The patient gave no history that indicated that a chest radiograph was necessary for the planned procedure. In retrospect, the size of this patient's transdiaphragmatic hernia would have precluded monitored anesthesia care and required general anesthesia with tracheal intubation.

* Memorial Sloan-Kettering Cancer Center and Weill Medical College of Cornell University, New York, New York.

Eckardt V, Kanzler G, Schmitt T, Eckardt A, Bernhardt G: Complications and adverse effects of colonoscopy with selective sedation. Gastrointest Endosc 2000; 52:703–4
Rezaiguia-Delclaux S, Streich B, Bouleau D, Delchier JC, Dhonneur G, Meignan M, Duvaldestin P: Pulmonary scintigraphy for diagnosis of aspiration during intravenous propofol anaesthesia for colonoscopy. Br J Anaesth 2001; 87:204–6
Katz RI, Belenker SL, Poppers PJ: Intraoperative management of a patient with a chronic, previously undiagnosed traumatic diaphragmatic hernia. J Clin Anesth 1998; 10:506–9
Simpson J, Lobo DN, Shah AB, Rowlands BJ: Traumatic diaphragmatic rupture: Associated injuries and outcome. Ann R Coll Surg Engl 2000; 82:97–100
Baumann U, Mettler M: Diagnosis and hazards of unexpected diaphragmatic hernias during colonoscopy: Report of two cases. Endoscopy 1999; 31:274–6
Chae H, Kim S, Han S, Choi K, Sun H, Ahn C: Herniation of the large bowel through a posttraumatic diaphragmatic defect during colonoscopy: Report of a case. Dis Colon Rectum 2002; 45:1261–2