Opinion by
Judge REED.In this medical malpractice action, plaintiff, John Locke, appeals from the judgment entered upon a jury verdict in favor of defendant, Gary Vanderark, M.D. We affirm.
In the months of February, September, and October 1979, the defendant, a neurosurgeon, performed ventricular shunt surgeries to alleviate plaintiff’s condition of hydrocephalus. The purpose of these operations was to drain excessive cerebrospinal fluid from the cranial area. This was to be accomplished by the placement of a shunt catheter through the right side of the brain. Such a catheter allows drainage of the fluid through other catheters for ultimate dissipation into the abdominal area.
After the third operation, plaintiff suffered hemiparesis to the left side of his body. He thereafter brought this action charging, inter alia, that defendant was negligent during the operative procedures. The issues of negligence and causation of plaintiff’s injuries were disputed in the evi*29dence and were submitted to the jury. It found in favor of the defendant.
I.
Plaintiff first contends that the trial court erred in limiting the scope of opinion testimony by plaintiffs experts relative to damages. We disagree.
A.
Testimony of Plaintiffs Psychiatrist
At trial, plaintiff called a board certified psychiatrist who had treated plaintiff in 1979 at Bethesda Psychiatric Hospital in Denver for neuropsychological and organic brain disorders. The psychiatrist testified not as plaintiffs expert witness, but in her capacity as plaintiffs treating psychiatrist at Bethesda.
While under the psychiatrist’s care, plaintiff submitted to a program of psychological testing to assess the extent of his higher cortical functions following a history of hydrocephalus and surgery. Based upon her observation of plaintiff and review of reports prepared by others pertaining to his psychological condition, the psychiatrist stated that plaintiff suffered from profound feelings of hopelessness and had great anxiety about deficits in his cognitive abilities.
The psychiatrist was not permitted to testify, however, concerning whether the long-term result of the hydrocephalus was a lowered IQ or whether a subsequent ven-triculostomy performed in 1986 had restored plaintiffs intellectual functioning.
Plaintiff argues that he was prejudiced and denied a fair trial when the trial court precluded the psychiatrist from giving additional opinion testimony regarding the causal connection between hydrocephalus and his lowered IQ. Defendant contends that the trial court properly precluded the psychiatrist from presenting additional opinion testimony since such had not been disclosed pursuant to the C.R.C.P. 121 § 1-18. Cf. C.R.C.P. 16 (effective as to cases filed on or after April 1, 1988). We agree with defendant.
C.R.C.P. 121 § 1-18 required parties retaining the services of an expert witness to file a trial data certificate setting forth the subject matter upon which the expert is expected to testify, the expert’s conclusions and opinions and the basis thereof, and the expert’s qualifications.
Failure to disclose the identity of experts or their opinions, or failure to supplement the expert’s responses to discovery when additional information becomes known, can result in the imposition of sanctions, including an order limiting the scope of an expert’s testimony at trial. See Daniels v. Rapco Foam, Inc., 762 P.2d 717 (Colo.App.1988).
Whether such sanctions should be imposed is a matter resting within the sound discretion of the trial court. Exercise of that discretion will not be disturbed upon review absent a clear showing that it has been abused. Overland Development Co. v. Marston Slopes Development Co., 773 P.2d 1112 (Colo.App.1989).
Here, there can be no question but that plaintiff failed to disclose the psychiatrist’s opinion regarding’the association between IQ and the hydrocephalic condition affecting plaintiff. The record also reveals that plaintiff did not timely disclose the psychiatrist’s qualifications to render such an opinion. Moreover, despite the fact that interrogatories were propounded to plaintiff requesting the identity of expert witnesses and disclosure of their opinions, plaintiff responded by stating that the opinions of the psychiatrist and the basis therefor were disclosed in her deposition. Hence, it was proper for the trial court to restrict the psychiatrist’s testimony to opinions expressed in her deposition, and any opinion expressed in addition to those in the deposition was properly excluded.
B.
Testimony of Neurosurgeon
Plaintiff also argues that the trial court erred in precluding plaintiff’s expert from testifying regarding damages other than those related to hemiparesis. Defendant contends that the expert’s testimony *30was properly limited to the subject matter of his pre-trial endorsement and the opinions expressed in his deposition. Again, we agree with the defendant.
A board certified neurosurgeon testified as an expert witness for plaintiff to the effect that a partial occlusion of the ventricular shunt occurred after the first surgery, causing re-dilation of the ventricle and development of increased intercranial pressure. This malfunctioning of the shunt necessitated shunt revision procedures in September and October of 1979.
The neurosurgeon opined, based upon a reasonable degree of medical certainty, that repeated passes of the shunt which took place during the October surgery caused vascular left-sided hemiparalysis. In the neurosurgeon's opinion, this placement further exacerbated the original surgery injury with consequent onset of neu-rologic deficits.
The neurosurgeon was also prepared to testify that, in his opinion, defendant was negligent by failing to revise the ventricular end of the shunt during the course of the September surgery. . According to the neurosurgeon, this had the long-term result of causing brain deterioration because of hydrocephalus.
Plaintiff did not formally endorse the neurosurgeon as an expert, pursuant to C.R.C.P. 121 § 1-18, because he was a substitute for another medical witness previously designated to serve as plaintiffs expert on issues of causation and damages relating to plaintiff’s hemiparesis.
The first notice given of the neurosurgeon’s opinion was in answer to defendant’s interrogatories which requested the identity and opinions of plaintiff’s expert witnesses. In response, a copy of a report giving the neurosurgeon’s preliminary evaluation of the case and summarizing his opinions was provided to defendant’s counsel.
The report stated that the third operative procedure performed on plaintiff in October 1979 utilized improper techniques and caused plaintiff’s hemiparesis. It indicated further that at the time of the revision of the shunt, in September of 1989, a new needle track should have been made at the previous operative site for later insertion of a ventricle catheter.
The report, however, did not indicate that the shunt revision procedure performed in September contributed to damages other than hemiparesis. Not until trial did plaintiff’s counsel inform defense counsel and the court that the neurosurgeon’s specific opinion would extend to additional damages relating to the September surgery.
At trial, defendant moved to limit the neurosurgeon’s opinion testimony to that which had been disclosed in the interrogatories. The trial court granted defendant’s motion, finding that to allow the undisclosed opinion would violate C.R.C.P. 121 § 1-18.
Plaintiff maintains, however, that it was defendant’s failure to depose the witness adequately which resulted in the non-disclosure of his additional opinion. According to plaintiff, the doctor told defendant in his deposition that he was prepared to testify concerning the reasonableness and necessity of bills for treatment of depression, inability to concentrate, and lowered IQ.
The purpose of C.R.C.P. 121 § 1-18 was to allow litigants the benefit of timely ascertaining and relying upon the opinions of experts retained by their adversaries. The rule properly contemplated limiting the scope of an expert’s testimony to those opinions actually revealed during discovery. See Daniels v. Rapco Foam, Inc., supra; Conrad v. Imatani, 724 P.2d 89 (Colo.App.1986). The party retaining an expert witness has the obligation to keep abreast of the opinions which may be expressed at trial, and the court should not view favorably late disclosure of new opinions.
The question then is whether the neurosurgeon’s opinion that plaintiff had damages other than hemiparesis which were attributable to negligence in performing the September 1979 shunt revision went beyond the fair scope of his earlier disclosed opinion that trauma caused by the October 1979 procedure was manifested by hemiparesis with incidental effects caused *31by the September 1979 surgery. While there may be no question that the revised .opinion regarding damages caused by the September surgery is consistent with his original opinion, it is decidedly more specific, and the implications of such an opinion may be profoundly different from the standpoint of damages. We conclude, therefore, that the trial court did not err in ruling that the tardily disclosed 'opinion was beyond the scope of discovery, and thus, we find no abuse of discretion by the court in precluding testimony regarding same at trial.
C.
In addition, even if we assume the trial court erred by restricting the scope of opinion testimony relating to plaintiffs neuro-psychological damages, such error was harmless since the jury found in favor of defendant on the issue of liability. Gray v. Houlton, 671 P.2d 443 (Colo.App.1983).
II.
Plaintiff contends that the trial court erred in permitting the defense to cross-examine his expert neurosurgeon witness concerning the fact that he had been sued for malpractice on at least six occasions. We agree, but conclude that the error here does not warrant reversal.
In demonstrating the qualifications of his expert witness, the plaintiff established that a substantial portion of the witness’ practice involved employment as an expert or consultant in medical malpractice cases involving neurosurgeons. He stated that he had given testimony in a number of such cases as an expert witness.
During cross-examination, however, defense counsel was permitted to elicit from the witness that he had been sued for medical malpractice on at least five occasions and for defamation on one occasion. Testimony as to the defamation case was elicited without objection. Defendant argued to the trial court that evidence concerning the other cases was relevant to the witness’ credibility as indicating bias.
The trial court agreed with defendant and, over plaintiff’s objection, allowed cross-examination to proceed with only the admonition that the fact of the malpractice suits be revealed and not the specifics. The record contains no indication that the malpractice suits against the witness involved the medical procedures in question here.
Both before and after adoption of the Colorado Rules of Evidence, the rule in this jurisdiction has been that wide latitude should be allowed in cross-examination of a witness but that counsel should not be permitted to inquire concerning subjects which are totally unrelated to resolution of the issues in the trial. See Webb v. People, 97 Colo. 262, 49 P.2d 381 (1935); People v. Diaz, 644 P.2d 71 (Colo.App.1981).
We view that rule as being of particular significance here because inquiry into unrelated litigation requires, in fairness, that the witness be permitted to explain the nature, circumstances, and the decision, if any, in each case to rehabilitate the challenged credibility. Conversely, if any case was settled, explanation would be necessary regarding the reasons for and terms of any compromise agreement. As a result, this evidence would divert the jury’s attention from the dispositive issues in the case and trial preparation and cost could be extensive. In short, the “sideshow would take over the circus.” See People v. Taylor, 190 Colo. 210, 545 P.2d 703 (1976).
We conclude that the record here does not support the trial court’s ruling that this line of inquiry was relevant to the witness’ bias or credibility. See Laughridge v. Moss, 163 Ga.App. 427, 294 S.E.2d 672 (1982). In so doing, we recognize that courts in other jurisdictions have, for the purposes of credibility, permitted this type of cross-examination. See Navarro de Cosme v. Hospital Pavia, 922 F.2d 926 (1st Cir.1991); Willoughby v. Wilkins, 65 N.C.App. 626, 310 S.E.2d 90 (1983).
Nevertheless, we conclude that reversal is not warranted in this case because we do not view this cross-examination as having prejudiced the jury. See CRE 103(a); Kerby v. Flamingo Club, Inc., 35 *32Colo.App. 127, 532 P.2d 975 (1975). The record discloses that the references made to the malpractice cases was limited during the cross-examination itself and that the issue was not discussed in closing argument. Most importantly, though, we think harmless error is indicated by the record as a whole which reflects that the neurosurgeon was effectively impeached on a number of other topics relating to his credibility-
Specifically, the expert expressed a new and different opinion as to defendant’s malpractice at trial that had not been disclosed during the course of his deposition, notwithstanding questions designed to elicit all of the expert’s views. Moreover, other cross-examination established that the expert could not recall at his deposition ever having testified against a particular physician in another malpractice case, even though he was personally acquainted with that individual and even though this physician had filed suit against the expert for defamation.
Two other examples strike us as persuasive that the challenged cross-examination was harmless. The expert testified as to having been removed from a teaching position, but stated that he was reinstated thereafter. However, a physician called by defendant refuted this, stating that the expert had not been reassigned to the teaching staff.
Also, the expert was forcefully cross-examined on an opinion expressed in another case which appears to contradict directly his conclusions of neurosurgical negligence relating to the ventricular shunt procedure at issue in this case. Finally, the record reflects substantial, competent evidence which supports the verdict of the jury. Thus, we conclude that the error was harmless.
III.
Finally, we reject plaintiff’s contention the trial court erred in admitting various medical and employment records.
In view of plaintiff’s stipulation both to the authenticity of these documents and to the fact that they constituted records kept in the regular course of business, there could be no error committed by their admission into evidence. Bates & Sons, Inc. v. Great Western Ry. Co., 158 Colo. 259, 406 P.2d 98 (1965). Furthermore, because no contemporaneous objection on the grounds of relevancy was made at trial, the issue is not properly preserved for our review. See Russell v. First American Mortgage Co., 39 Colo.App. 360, 565 P.2d 972 (1977).
Error is also claimed by the admission in evidence of other documents provided by a hospital to which plaintiff did object, presumably on relevancy grounds, stating that these made reference to medical findings not otherwise supported by the evidence, e.g., that plaintiff had, at one point, been diagnosed with migraine headaches. However, plaintiff does not direct us to specific parts of the record in which that diagnosis was made. Accordingly, we do not disturb the trial court’s ruling that the jury was entitled to consider the content of these records concerning issues to which they pertained. Mauldin v. Lowery, 127 Colo. 234, 255 P.2d 976 (1953).
IV.
Plaintiff’s contention that the jury should have been instructed concerning the duties of parties to supplement discovery responses is without merit.
Judgment affirmed.
RULAND, J., concurs. DUBOFSKY, J., dissents.