— Judgment, Supreme Court, New York County (David Edwards, Jr., J.), entered May 3, 1990, which, after the close of evidence at a jury trial, dismissed the complaint pursuant to a CPLR 4401 motion for a directed verdict, unanimously affirmed, without costs.

Plaintiff Donald Storniolo, who suffered from severe ulcerative colitis, commenced this action after he developed a fistula of the urethra following surgery by the defendants for the removal of his colon and the creation of an ileostomy. Defendants’ motion for a directed verdict was properly granted, since by no rational process could the jury have found in plaintiff’s favor. (Blum v Fresh Grown Preserve Corp., 292 NY 241.)

*551The medical testimony adduced at trial, including that of plaintiffs’ own medical expert, failed to establish a departure from normal medical standards during the surgery, or that negligence on the part of one or both of the defendants was a substantial factor in causing the fistula. Rather, the testimony established multiple possible causes for the development of a fistula even in the absence of medical malpractice, including the underlying disease process and an infection or ischemic necrosis. Thus, the medical testimony at trial did not provide any rational basis for the jury to conclude that the fistula developed by reason of the defendants’ negligence (Mortensen v Memorial Hosp., 105 AD2d 151).

Similarly, the trial court properly declined to submit the case to the jury under the doctrine of res ipsa loquitur, where the plaintiffs failed to establish that the development of a fistula following the underlying surgery was an event which ordinarily does not occur in the absence of negligence or was caused by any agency or instrumentality within the exclusive control of the defendants. (Dermatossian v New York City Tr. Auth., 67 NY2d 219.)

We have reviewed the plaintiffs’ remaining claims and find them to be without merit. Concur — Carro, J. P., Wallach, Kupferman, Asch and Kassal, JJ.