233 F.3d 382 (6th Cir. 2000)
Deborah Jahn, Plaintiff-Appellant,v.Equine Services, PSC; Scott D. Bennett,  D.V.M.; Mary Beth Wallingford, D.V.M.; and  Richard Griffin, D.V.M., Defendants-Appellees.
No. 99-5647
UNITED STATES COURT OF APPEALS FOR THE SIXTH CIRCUIT
Argued: May 4, 2000Decided and Filed: November 21, 2000

Appeal from the United States District Court for the Eastern District of Kentucky at Frankfort.  No. 98-00009--Joseph M. Hood, District Judge.[Copyrighted Material Omitted]
Daniel E. Danford, Benjamin L. Kessinger, Jr., STITES & HARBISON, Lexington, Kentucky, for Appellant.
Matthew J. Smith, Thomas F. Glassman, SMITH, ROLFES & SKAVDAHL COMPANY,  Cincinnati, Ohio, Michael J. Cox, MILLER, GRIFFIN & MARKS, Lexington, Kentucky, for Appellees.
Before: MERRITT, CLAY, and CUDAHY, Circuit Judges*.
OPINION
CUDAHY, Circuit Judge.


1
Deborah Jahn owned a champion Hackney pony named Night Passage. In April of 1997, the  pony was taken to Equine Services, PSC, to have corrective surgery for a breathing problem. The surgery was performed on  April 15, 1997, and a few hours after the operation, Night Passage was found dead in his stall. Jahn sued Equine Services  and three veterinarians in federal court asserting various state-law causes of action. The district court granted summary  judgment in favor of the defendants on all counts in the complaint, and Jahn now appeals.


2
Jahn, an Illinois resident, sought treatment for Night Passage's palate displacement, a condition common among  Hackney ponies that interferes with the horse's breathing. This condition can be corrected using one of several surgical techniques, and Dr. Bennett at Equine Services1 chose to use a technique known as a "modified Forsell's procedure."2  This procedure involves the removal of muscle and tissue from the pony's neck, thereby allowing it to better relax its neck  to open the airway and permit fuller breathing3.  During a pre-surgery evaluation, it was discovered that Night Passage  had a fibrinogen level of 600 and a nasal discharge. Dr. Bennett apparently concluded that this was not a source of concern  and had the pony prepared.


3
The surgery began at approximately 4:30 p.m. on April 15, 1997. Three veterinarians and two assistants took part in the  procedure. Dr. Bennett supervised the entire operation and performed the modified Forsell's procedure himself. Dr. Richard  Griffin--a veterinary intern--recommended a pre-surgical anesthesia dosage and administered the anesthesia once Dr.  Bennett verbally approved the dose. Night Passage was given 450 milligrams of xylanine and 1100 milligrams of ketamine  before the surgery. Dr. Maribeth Wallingford--another veterinary intern--had limited involvement with the operation  because an emergency with another animal required her attention. The modified Forsell's procedure was conducted with  Night Passage under general anesthetic, and Dr. Griffin, again under the supervision of Dr. Bennett, administered anesthetic  gas to the pony throughout the surgery. No record of the type or amount of gas used exists4.  According to the  veterinarians present, Night Passage remained stable during the entire surgery, which lasted about 45 minutes.


4
After the surgery ended at 5:15, Night Passage was taken to a padded recovery room, where he began to wake up about  five minutes later. From this point forward,Equine Services made no additional medical records relating to Night Passage.  According to Dr. Bennett, Night Passage was back on his feet after 20 minutes, and he decided to return Night Passage to  his stall. Dr. Griffin supervised the pony's return to a regular stall, and observed Night Passage for approximately 10  minutes thereafter. All appeared fine. Dr. Bennett claims that he "probably saw [Night Passage] going back and forth to the  stalls and checking other horses 10 or 15 times" before 7:30 p.m., and each time, he detected no problems with the pony's  condition. See J.A. at 223 (Bennett Depo.).5 As indicated above, however, no medical records of any kind document  these visits or Night Passage's condition during the course of the evening. A horse caretaker at Equine Services claims that  he checked on Night Passage periodically until 8:15 (when he went home for the night), but again, there are no records of  the visits or Night Passage's condition. At approximately 9:00, one of the technicians who assisted with Night Passage's  surgery checked the pony. She claimed that no problems were detected, but, yet again, there are no medical records to  support this. Night Passage was found dead at approximately 10:00 p.m.


5
Night Passage's corpse was sent to Dr. Robert Tramontin at the Livestock Disease Diagnostic Center (LDDC) in  Lexington, Kentucky, where he preformed an autopsy on the unfortunate animal. His autopsy report does not indicate  whether he conducted an external examination of the body, but it contains several specific findings from an internal  examination. During this autopsy, Dr. Tramontin examined the area of the surgery and determined that the surgery had been  done properly. He also performed cultures to check for bacterial infection in the lungs but found no evidence of an  infection, although he noted that the lungs were very congested and the trachea and bronchi contained a "pale frothy  material." J.A. at 452 (Tramontin's Case Summary). The report states that the "[c]ongestive change in various organs along  with very pale mucous membranes indicate that this animal was in shock." Id. In his deposition, Dr. Tramontin stated that  he did not know the specific cause of death, and the autopsy report noted simply "DIAGNOSIS: Hemorrhage, brain and  spinal cord, etiology uncertain." Id. The LDDC sent numerous slides to Dr. Bolin, the veterinary pathologist at the Illinois  Bureau of Animal Disease Laboratory. Looking at these slides, Dr. Bolin also identified signs of shock, but he could not  determine the cause of death. Nor did Dr. Bolin see any signs of infection based on the slides in his possession6.


6
In November of 1997, Jahn filed suit against Dr. Bennett and Equine Services in the Eastern District of Kentucky, later  adding Drs. Griffin and Wallingford as defendants in her first amended complaint. (We shall refer to the defendants  collectively as Equine Services.) Jahn's complaint stated five counts against the defendants. First, she alleged that all the  defendants had been negligent in their treatment of Night Passage before, during and after the surgery. Second, she claimed  that Equine Services had breached an oral contract to monitor Night Passage "continuously, completely and around the  clock." J.A. at 39 (First Amended Complaint). Third, Jahn alleged that Dr. Bennett and Equine Services were negligent by  failing to inform her of the risks involved in Night Passage's surgery. Fourth, Jahn pleaded conversion against Dr. Bennett  and Equine Services alleging that they did not have consent to perform the surgery. Fifth, and finally, Jahn alleged that  Equine Services had committed fraud by representing to her that NightPassage would be monitored "continuously,  completely and around the clock." Id. at 42. Given the complicated nature of cases dealing with allegations of veterinary  malpractice, Jahn employed two expert witnesses.


7
Jahn's first expert witness , Dr. George Mundy, has been a practicing veterinarian in Kentucky since 1983 and has  extensive experience diagnosing and treating horses. He has presented several papers on the veterinary aspects of race  horses, but as of the time he was deposed, Dr. Mundy had not performed a surgery in the preceding ten years and had never  performed a modified Forsell's procedure. Jahn's other expert, Dr. Rhonda Robbins, has been a veterinarian since 1986,  specializing in horse medicine, and has taught in the Department of Large Animal Surgery at Auburn University.


8
In their depositions, both Drs. Mundy and Robbins stated that a fibrinogen level of 600 and a nasal discharge are signs  of infection or inflammation and provided cause for delaying the surgery in order to conduct further tests. Dr. Robbins  explained that Night Passage's fibrinogen level was high enough to be a significant factor in the pony's death, and Dr.  Mundy noted that even a mild infection can threaten a horse's life. Both also agreed that infection matched with  anesthesia--even normal dosages, when given to a horse with an infection--could lead to shock and then death. Dr. Robbins  stated that it appeared, from the records she had before her, that Night Passage had been given an overdose of  approximately 1.5 to 2 times the normal pre-operative dosage of Xylanine and Ketamine. Dr. Mundy believed that the pony  went into shock at some point after the surgery, fell and hit his head, causing the hemorrhage in the brain and spinal cord  and death. Drs. Mundy and Robbins were both critical of the lack of medical records kept by Equine Services and were  especially critical of the lack of postoperative care. But, much like the pathologists Tramontin and Bolin, neither Dr.  Mundy nor Dr. Robbins could identify with any degree of certainty the specific physiological cause of Night Passage's  death.


9
After the case proceeded through discovery, all the defendants moved for summary judgment. Although Dr. Wallingford  had retained separate counsel, the defendants all made the same argument for summary judgment. They argued that Jahn's  claims failed because she could not establish the cause of the pony's death. Because Jahn could not establish causation, they  argued, her entire case collapsed. In response to these motions, the district court determined, sua sponte and without  allowing additional briefing, that the proposed testimony of Drs. Mundy and Robbins was inadmissible under Daubert v.  Merrell Dow Pharm., Inc., 509 U.S. 579 (1993), and rejected their expert testimony. The district court then decided  summary judgment against Jahn on all her claims because without the testimony from her expert witnesses she could not  prove causation. She appeals, arguing that the district court improperly excluded her expert-witness testimony. She also  contends, under numerous theories, that the district court erred by granting summary judgment for the defendants. We shall address only her expert witness argument here. Summary judgment is, of course, closely linked with the Daubert analysis,  although it might conceivably be available even with a different Daubert outcome. We will not discuss Jahn's res ipsa  loquitur and bailment arguments, since they were apparently not raised below.


10
We review the district court's decision to grant summary judgment de novo. See Harris v. General Motors Corp., 201  F.3d 800, 802 (6th Cir. 2000). Summary judgment is proper only if there is no genuine issue of material fact. See Celotex  Corp. v. Catrett, 477 U.S. 317, 330 (1986); Anderson v. Liberty Lobby, Inc., 477 U.S. 242, 248(1986). The burden of  proving proximate causation falls on the plaintiff, and in a professional negligence case in Kentucky, proximate causation  must be established by expert testimony. See Morriss v. Hoffman, 551 S.W.2d 8, 9 (Ken. Ct. App. 1977); see also Welsh v.  United States, 844 F.2d 1239, 1243 (6th Cir. 1988). Here, the sole basis for the district court's decision to grant summary  judgment was its exclusion of Jahn's expert testimony. Thus, we must review its ruling that Jahn's proffered expert  testimony was inadmissible, and, even in the context of summary judgment, we review that decision for abuse of discretion. See General Elec. Co. v. Joiner, 522 U.S. 136, 143 (1997).


11
The admissibility of expert testimony in a federal court is primarily governed by Federal Rule of Evidence 702, which  states:


12
If scientific, technical, or other specialized knowledge will assist the trier of fact to understand the evidence or to  determine a fact in issue, a witness qualified as an expert by knowledge, skill, expertise, training, or education, may  testify thereto in the form of an opinion or otherwise.


13
Fed. R. Evid. 702. In Daubert, the Supreme Court provided extensive guidance for the application of the dictates of Rule  702. The Court explained that Rule 702 displays a "liberal thrust" with the "general approach of relaxing the traditional  barriers to 'opinion' testimony." Id. at 588 (quotation omitted). But, the Court continued, Rule 702 places some restrictions  on the admissibility of expert testimony, and the district court retains the responsibility of "screening such evidence." Id. at  589. When a party proffers expert testimony, the district court must determine whether the testimony is both relevant and  reliable when ruling on its admission. See id. at 590-91.


14
In assessing the relevance and reliability of proffered expert testimony, the district court must determine:


15
whether the expert is proposing to testify to (1) scientific knowledge that (2) will assist the trier of fact to understand  or determine a fact in issue. This entails a preliminary assessment of whether the reasoning or methodology  underlying the testimony is scientifically valid and of whether the reasoning or methodology properly can be applied  to the facts in issue.


16
Daubert, 509 U.S. at 592-93. "'[S]cientific knowledge' establishes the standard of evidentiary reliability," id. at 590, and to  be considered appropriately scientific, the expert need not testify to what is "'known' to a certainty" but must only state "an  inference or assertion . . . derived by the scientific method." Id. Testimony meets this threshold when "an expert, whether  basing testimony on professional studies or personal experience, employs in the courtroom the same level of intellectual  rigor that characterizes the practice in the relevant field." Kumho Tire Co., Ltd. v. Carmichael, 526 U.S. 137, 152 (1999).  Experts are permitted a wide latitude in their opinions, including those not based on firsthand knowledge, so long as "the  expert's opinion [has] a reliable basis in the knowledge and experience of the discipline." Daubert, 509 U.S. at 592. The  court explained that relevance of proposed scientific testimony is established through Rule 702's "'helpfulness' standard"  which "requires a valid scientific connection to the pertinent inquiry as a precondition for admissibility." Id. at 591-92. In  the end, Rule 702 embodies a flexible approach and its "overarching subject is the scientific validity . . . of the principles  that underlie the proposed submission. The focus, of course, must be solely on principles and methodology, not on the  conclusions that they generate." Daubert, 509 U.S. at 594-95.


17
As a general matter, "[p]hysicians and other medical professionals routinely testify as experts since their specialized  knowledge generally helps the jury resolve medical issues." 4 Jack B. Weinstein & Margaret A. Berger, Weinstein's Federal  Evidence § 702.04[4] (Joseph M. McLaughlin ed., 2d ed. 2000). So here, given the inherently medical nature of Jahn's  lawsuit, Jahn proffered the testimony of veterinarians Dr. Mundy and Dr. Robbins to assist the trier of fact in determining  whether Equine Services was responsible for Night Passage's death. The district court's Daubert analysis consisted of five  pages in its first order granting summary judgment. The court first notes that Dr. Mundy had never performed a modified  Forsell's procedure and had never worked outside of a university setting, concluding from these facts that Dr. Mundy's  "opinions as to what may have killed Night Passage are very suspect." J.A. at 57C (Mem. Op. and Order, April 6, 1999).  The district court also noted that Dr. Mundy, relying solely on the pathologists' report, "makes an assumption as to what  killed Night Passage and then gives what he considers to be the most likely scenario that would have produced such a  result," referring to this methodology as "stack[ing] one guess on top of another." Id. at 57D. The district court also noted  that Jahn's other expert witness, Dr. Robbins, freely admitted that she did not have an opinion as to what specifically caused  the horse's death. The district court finally noted that both experts' suggestion that an infection may have killed the pony  was contradicted by the pathologist's report (which didn't find any evidence of infection)--reducing their explanations to  "speculative and unreliable opinions." Id. at 57G. However, we believe that the district court's Daubert analysis both  mischaracterized the methodology employed by Drs. Mundy and Robbins and ultimately employed a standard of  admissibility more stringent than that expressed in Rule 702.


18
We first note that the district court erred in finding that Dr. Mundy's opinions as to how Night Passage died were "very  suspect" on the ground that Dr. Mundy "never performed the surgery that was performed in this case and has never worked  in a non-university setting." J.A. at 57C (Mem. Op. and Order, Apr. 6, 1999). The fact that Dr. Mundy had never performed  a modified Forsell's procedure would cast doubt on any criticisms he had regarding the performance of the surgery, but he  did not criticize the surgical procedure. As his report and deposition make clear, Dr. Mundy criticized Equine Services'  failure to conduct a more thorough pre-operative examination and failure to monitor Night Passage after the surgery. Dr.  Mundy did not base his opinions regarding Equine Services' care of Night Passage or the cause of his death on any  knowledge of the procedure performed. Instead, he quite clearly explained that he was relying on the medical records  presented to him by the defendants and his own clinical/professional experience. Therefore, his lack of hands-on familiarity  with the surgery performed was not relevant to a ruling on the admissibility of Dr. Mundy's testimony regarding  pre-operative testing and post-operative monitoring.


19
The primary reason the district court gave for excluding Dr. Mundy's and Dr. Robbins' opinion testimony was their  inability to specify what, in particular, killed Night Passage. The district court turned to this section of Dr. Mundy's  deposition testimony:


20
Q: One: Do you have an opinion as to what [Night Passage] died of?


21
A: No, but I--it's apparent to me that something went wrong.


22
Q:So you are not prepared to give testimony as to the cause of death; is that correct?


23
A: I'm not prepared because I don't see anything in the medical records specifically giving a diagnosis.


24
J.A. at 361 (Mundy Depo.). From this excerpt, the district court concluded that "[w]ithout knowing the cause of death, Dr.  Mundy's opinions are not reliable." J.A. at 57D (Mem. Op. and Order, Apr. 6, 1999). The district court also pointed to an  excerpt from Dr. Robbins's deposition:


25
Q: So as I understand you sitting here today you do not have an opinion as to what cause this horse's death?


26
A: Not really.


27
J.A. at 543 (Robbins Depo.). Based on these excerpts, the district court stated that "[b]ecause plaintiff's experts do not  know what caused the pony's death, they can only speculate." J.A. at 57G (Mem. Op. and Order, Apr. 6, 1999). Plaintiff  concedes that no one knows the precise physiological cause of Night Passage's death, and by implying that specific  knowledge of the precise physiological cause of Night Passage's death is a prerequisite to admissibility, we believe that the  district court held the experts up to entirely too strict a standard when considering the admissibility of their testimony.


28
The central issue in this case is whether Equine Services caused or failed to prevent Night Passage's untimely demise.7  In order to be admissible on the issue of causation, an expert's testimony need not eliminate all other possible causes of the  injury. See Ambrosini v. Labarraque, 101 F.3d 129, 140 (D.C. Cir. 1996). "The fact that several possible causes might  remain 'uneliminated' . . . only goes to the accuracy of the conclusion, not to the soundness of the methodology." Id. Here,  although they admitted that they did not know the cause of death, both Dr. Mundy and Dr. Robbins identified what they  believed to be the probable cause of Night Passage's demise. See J.A. at 396-97, 419 (Mundy Depo.); id. at 582-83, 590  (Robbins Depo.). It is undeniable that Night Passage is dead, and Jahn has proffered expert testimony to "assist the trier of  fact to understand the evidence or to determine" why this animal is dead. Fed. R. Evid. 702. Daubert and Rule 702 require  only that the expert testimony be derived from inferences based on a scientific method and that those inferences be derived  from the facts of the case at hand, see Daubert, 509 U.S. at 590-92, not that they know answers to all the questions a case  presents--even to the most fundamental questions. Certainty is not to be found in this case, due in considerable part to the  lack of medical records kept by the defendants. Hampered by a lack of post-operative medical records, Jahn has called on  her expert witnesses to use their expertise to piece together what probably happened to her now-dead horse. If Equine  Services had kept records, Drs. Mundy and Robbins could probably have stated their opinions in a more illuminating  fashion, and it might have been possible for the witnesses to precisely determine the physiological cause of Night Passage's  death. Both experts noted that their analysis was hampered by the lack of records, see J.A. at 386 (Mundy Depo.); id. at 541  (Robbins Depo.), and it seems patently unfair to allow Equine Services to benefit from what seems to be a deplorable, and  perhaps even negligent, absence of record-keeping. Cf. Welsh, 844 F.2d at 1245-49 (explaining, in a diversity action  governed by Kentucky law, that the party that negligently failed to preserve medical records must "bear the onus of proving  a fact whose existence or nonexistence was placed in greater doubt by [that] negligent party").


29
Dr. Mundy and Dr. Robbins, after reviewing all of the evidence presented to them, present a chain of events that they  believe, in toto, probably caused Night Passage to die. First, Night Passage probably had a mild infection on the day of the  surgery. This indication of infection should have delayed the surgery andprompted further testing to determine if the  infection made an operation hazardous. Second, being put under anesthetic stressed the horse's system to the point that,  although it awoke from the surgery, Night Passage went into shock sometime thereafter. This shock progressed unnoticed  and untreated and eventually killed the animal. The district court, however, viewed this as "stacking one guess on top of  another," J.A. at 57D (Mem. Op. and Order, Apr. 6, 1999), and rejected his testimony on that basis.


30
Were Dr. Mundy and Dr. Robbins pulling their notions from thin air, the district court's use of "guess" would be  appropriate, and their testimony should have been excluded as lacking a factual foundation. But they did no such thing:  both based their opinions on the facts with which they were presented. By off-handedly labeling this a "guess," the district  court failed to explore whether the proposed testimony was based on "the same level of intellectual rigor that characterizes  the practice" of veterinary medicine. Kumho Tire, 526 U.S. at 152. We believe that Drs. Mundy and Robbins clearly used a  methodology derived from scientific medical knowledge, although limited by the information provided to them by the  defendants. For example, Dr. Mundy explained that he believed an infection was probable for two reasons:


31
The first is the elevated fibrinogen value that is documented, and second--and if you look in my conclusions, I  also--I--I dictate two specific facts documented in the record, the elevated fibrinogen value concurrent with the mild  serous mucoid bilateral nasal discharge.


32
J.A. at 382 (Mundy Depo.). This shows that Dr. Mundy based his opinion on clinical indicia of an infection. Dr. Robbins  similarly explained that Night Passage's fibrinogen level and nasal discharge suggested an infection. See J.A. at 579-82  (Robbins Depo.). The district court discounted these facts by explaining that "it is very suspect to assume that the animal  had an infection within a reasonable medical probability, especially considering that the pathologist did not find an  infection." J.A. at 57G n.10 (Mem. Op. and Order, Apr. 6, 1999). See also id. at 57E n.6 ("Because the pathologist did not  find an infection, this calls into question the reliability of Dr. Mundy's report."); id. at 57G ("The problem with this  assumption is that it goes against the pathologist's report . . . ."). In so stating, the district court erred in two ways. First, the  district court apparently weighed the pathologist's testimony against Jahn's expert testimony and apparently found the  opinions of Dr. Mundy and Dr. Robbins suspect because they contradicted that of the pathologist. But comparing two  pieces of evidence and determining which is more credible should be left for the finder of fact and should not be considered  when ruling on Rule 702 admissibility. See Kennedy v. Collagen Corp., 161 F.3d 1226, 1229 (9th Cir. 1998) (reversing  district court's exclusion of expert testimony because "[u]ltimately, the trial court failed to distinguish between the  threshold question of admissibility of expert testimony and the persuasive weight to be accorded such testimony by a jury").


33
The second error committed by the district court in dismissing Dr. Mundy's and Dr. Robbins's opinions that Night  Passage had an infection prior to the surgery is that it mischaracterized the methodology they employed to come to that  opinion. Looking at the records of test results and physical symptoms to infer the presence of an infection is not a  methodologically unsound "assumption" or "guess"--it is a diagnosis. See Walker v. Soo Line R.R. Co., 208 F.3d 581, 586  (7th Cir. 2000) (noting that patient histories "provide information upon which physicians may, and at times must, rely in  their diagnostic work");  In re Paoli R.R. Yard PCB Litig., 35 F.3d 717, 762 (3d Cir. 1994) ("[E]valuation of the patient's  medical records . . . is a reliable method of concluding that a patient is illeven in the absence of a physical examination.").  The fact that neither pathologist confirmed the existence of an infection certainly places the matter in debate, but it does not  render the methodology of Drs. Mundy or Robbins unreliable (although their conclusions may be less than certain).  Whether Night Passage was suffering from an undiagnosed infection and whether Equine Services negligently failed to  conduct further tests on the horse are questions for the trier of fact, not for the district court to answer when ruling on  admissibility of expert testimony.


34
The other components of Dr. Mundy's and Dr. Robbins' opinions are similarly based on the objective medical facts of  this case. With respect to their belief that Equine Services' inadequate post-surgical monitoring contributed to Night  Passage's death, recall that both Dr. Tramontin and Dr. Bolin noted that there were signs that Night Passage had been in  shock and that there had been a hemorrhage in his brain and spinal cord. These documented observations by the  pathologists, matched with the total absence of medical records for the post-surgical period, support the inference that  Night Passage was in some kind of distress, of which Equine Services was not aware. Using other clues from the existing  medical records, Dr. Mundy pieced together what he believed to be the probable series of events leading up to the pony's  demise. Based on Dr. Tramontin's note that the brain hemorrhage "may have been self-induced through some form of  trauma" and a photograph of Night Passage's corpse in the stall at Equine Services with blood pooling around its head and  some blood on the wall of the stall, Dr. Mundy believed that the horse suffered a "progressive, agonal death undoubtedly  with struggle." J.A. at 434 (Mundy Report). The hypothesis was that the horse was in shock due to the administration of  anesthesia in the presence of an undiagnosed infection, see J.A. at 396-97, 419 (Mundy Depo.), bashed his head on the wall  of the stall and died. Dr. Mundy concluded that, because there were no medical records, Equine Services did not adequately  monitor Night Passage, and stated that "[r]easonable veterinary practice includes close regular monitoring by trained  medical personnel, with appropriate medical records, in the post-surgical period," and "[t]he absence of this reasonable  veterinary practice, in my opinion, compromised the patient's life." J.A. at 434 (Mundy Report). Dr. Robbins linked the  undiagnosed infection to Night Passage's death: "the stress of surgery could have allowed endotoxin to be absorbed and  then we've got to follow up with an endotoxic reaction later." J.A. at 583 (Robbins Depo.). Dr. Robbins also believed that  "had someone been in attendance and monitored the pony as promised, life saving procedures could have been  implemented and may have prevented the death of the pony." J.A. at 619 (Robbins Report). Jahn's experts used the existing  facts to present their opinions on causation: the anesthesia and infection, which should have delayed the surgery in the first  place, caused Night Passage to go into shock and because Equine Services did not adequately monitor Night Passage, the  shock led to the horse's death. Even Dr. Bennett believes that the shock contributed to Night Passage's death. See J.A. at  239 (Bennett Depo.). Of course, Dr. Bennett and the Equine Services staff professed that they monitored Night Passage,  and Dr. Bennett pointed out that not all forms of shock are treatable. However, the adequacy of post-operative monitoring  and whether better monitoring could have saved the horse is surely a question for the trier of fact, not one to be ruled on  when determining the admissibility of expert testimony.


35
Because the opinions of Dr. Mundy and Dr. Robbins were based on undisputed objective medical facts and because the  experts apparently applied a scientifically-based methodology to the limited facts with which they were presented, we  believe that the district court abused its discretion in finding them inadmissibleon the apparent grounds that they  employed improper methodology and that the pathologists were more persuasive on the issue of the infection--under Rule  702. Medical opinions need not be unchallengeable in order to be admissible. Medical experts are just witnesses, and they  need not be purveyors of ultimate truth in order to be allowed on the stand. As the Supreme Court noted in Daubert, that  "[v]igorous cross-examination, presentation of contrary evidence, and careful instruction on the burden of proof are the  traditional and appropriate means of attacking shaky but admissible evidence." 509 U.S. at 596. The opinions of Dr. Mundy  and Dr. Robbins may very well be "shaky," but they are clearly not, as the district court apparently believed, "guesses" or  "assumptions."


36
Not only do we believe that the district court erred by mischaracterizing the methodology employed by Jahn's experts  and by weighing their testimony against that of the pathologists, but we also believe that the record was insufficient in order  to make a proper Daubert determination. Although we have explained that "[t]he district court is not obligated to hold a Daubert hearing," Clay v. Ford Motor Co., 215 F.3d 663, 667 (6th Cir. 2000), a district court should not make a Daubert determination when the record is not adequate to the task. "[I]n the absence of a hearing, we must review the record to  determine whether the district court erred in its assessment of the relevance and reliability of the expert testimony," id.  (quotation omitted), and the record before us contains enough material--the experts' reports, the pathologists' reports and  depositions from most of the people involved--for us to have determined that the district court mischaracterized the  testimony of Drs. Mundy and Robbins by weighing their opinions against the pathologists'. However, we do not believe  that the record is complete enough for this court to reverse the district court and directly rule that Jahn's expert testimony is  admissible.


37
For example, although we firmly believe relying on lab results and records of physical symptoms is appropriate  methodology to determine whether Night Passage had an infection, there is no evidence--like veterinary studies--in the  record verifying or contradicting the veterinarians' opinions that a fibrinogen level of 600 indicates the presence of an  infection.8 The district court mentioned the fact that Jahn provided no studies to support this opinion, but it is not very  surprising that the record was incomplete because the court gave Jahn no notice that it would be ruling on the admissibility  of her experts. A district court should not make a Daubert ruling prematurely, but should only do so when the record is  complete enough to measure the proffered testimony against the proper standards of reliability and relevance. We believe  that the record needs to be further developed to make an adequate Daubert determination in this case. With a more  complete record before the district court, Jahn will have an adequate opportunity to defend the admissibility of her experts'  testimony, and Equine Services will have an adequate opportunity to argue against it.


38
Because the district court's decision to grant summary judgment was based on its improper exclusion of Jahn's proffered  expert testimony, we Vacate the district court's decision to grant summary judgment. Further, we Remand for proceedings  not inconsistent with this opinion.



Notes:


*
  The Honorable Richard D. Cudahy, Circuit Judge of the United States Court of Appeals for the Seventh Circuit, sitting by  designation.


1
 . Equine Services, a Kentucky corporation, is owned by Dr. Scott Bennett. Jahn had taken Night Passage to Dr. Bennett  before to receive care for an eye injury. Although she was displeased with the high bill, she returned to discuss treatment of  Night Passage's breathing condition. During a tour of Equine Services's facility, she was told that Equine Services  monitored "continuously, completely and around-the-clock."


2
 . There is, however, no evidence in the record suggesting why Dr. Bennett chose this particular procedure, or whether he  discussed it with Jahn.


3
 . Jahn employed Larry Bacon as Night Passage's trainer, and Bacon brought Night Passage to Equine Services for  admission and performance of the modified Forsell's procedure. Although Jahn did not personally authorize the surgery on  the day of the operation, Bacon did. However, there is no documentary evidence demonstrating that Dr. Bennett explained  the risk of this procedure to either Jahn or Bacon.


4
 . In his deposition, Dr. Griffin testified that the gas used was halothane--a common general anesthetic--but he did not  recall the amount he administered.


5
 . All citations to the record will be to the parties' Joint Appendix.


6
 . The slides contained sections of Night Passage's lungs, liver, intestines, spleen, kidney, thyroid, myocardium and  portions of the brain.


7
 . The defendants' negligence is, of course, also central to this case, but because the district court's decision to grant  summary judgment did not address negligence, we will not do so either. Nor do we address the merits of Jahn's contract  claims.


8
 . We note, however, that a lack of supporting studies is not, in itself, fatal to the admissibility of expert testimony. See McCullock v. H.B. Fuller Co., 61 F.3d 1038, 1044 (2d Cir. 1995) ("Disputes as to the strength of [an expert's] credentials . .  . or lack of textual authority for his opinion go to the weight, not the admissibility, of his testimony.").


