The research examined adverse incidents from medical procedures performed in offices and same-day surgical centers rather than hospitals.
An eventual outgrowth of the analysis may be guidelines recommending against office procedures for some patients, said lead investigator Dr. David Bernstein, chief of gastroenterology at North Shore University Hospital in Manhasset.
He presented the analysis Tuesday at the annual convention of the American College of Gastroenterology in Washington, D.C.
While colonoscopy is an "extremely safe procedure," Bernstein said, "in terms of numbers, colonoscopy was the highest in terms of adverse events."
Bernstein and his colleagues found 391 complications associated with colonoscopy and 43 following combined colonoscopy/upper endoscopy. In addition to lacerated spleens, there was also evidence of perforated colons and a host of other problems.
Reasons cited for the hospitalizations and deaths included heart and breathing impairments, complications linked to pre-existing disorders, seizures, infections and allergic reactions.
Nine patients died within two days of the procedure, the analysis found. The New York State Health Department is currently investigating the deaths.
Among colonoscopy patients who suffered complications, Bernstein found 134 had to be transferred from the treatment site to a hospital for immediate care. Another 212 had to be hospitalized days or weeks later.
Since 2008, the state has required doctors to report negative outcomes associated with specific invasive procedures performed on an outpatient basis. New York is the only state to require such record-keeping.
Doctors must report complications stemming from treatments in offices or surgical centers involving gynecologic operations, colonoscopy or upper endoscopy. An estimated 1 million colonoscopies are performed annually in New York, with half performed in offices and surgical centers, and the rest in hospitals.