Kimberly, Garland, and Brad Roth brought suit against G.D. Searle & Company seeking recovery for injuries suffered as a result of Kimberly Roth’s use of a Cu-7 intrauterine device (IUD). The district court1 granted summary judgment in favor of Searle, concluding that the statute of limitations barred the Roths’ claims, which they filed in March 1989. The court stated Ms. Roth knew of her injuries and either knew or should have known of her potential claims before March 1987 — thereby triggering the two-year limitations period. The Roths argue that there were genuine issues of material fact with respect to the statute of limitation issues, that her injuries were latent, and that fraudulent concealment and equitable estoppel prevent application of the time bar. We affirm.
*1305The parties agree about most of the underlying facts. In early 1982, Kimberly Roth consulted with Dr. J.J. Kuncaitis about various methods of birth control. She decided to have an IUD inserted into her uterus, a procedure which Dr. Kuncaitis performed. Searle designed, manufactured, and marketed the device inserted, a Cu-7. The only potential side effects which Ms. Roth recalls discussing with Dr. Kuncaitis involved the possibility of an abortion or an allergic reaction to the copper in the IUD. She does, however, remember receiving a patient brochure which she “briefly read.” Searle offered uncontradicted testimony that the brochures distributed at that time contained language warning against pelvic infection and other possible adverse reactions.2
Approximately four months after the insertion, Ms. Roth began suffering severe pain in her lower abdomen. When she reported this pain to Dr. Kuncaitis, he referred her to Dr. Victor T. Wilson. Dr. Wilson told Ms. Roth that she suffered from an infection, and removed her IUD. Ms. Roth stated that neither doctor told her the cause of the infection.
Approximately two months after removal of her first IUD, Ms. Roth requested and received a second Cu-7. Although Dr. Kun-caitis wrote that Ms. Roth “has complete understanding of all the potential risks of the IUD,” Ms. Roth recalls no discussion of the risks associated with Cu-7 insertions. She does not dispute Dr. Kuncaitis’ testimony that she received a second patient brochure about the device.
In June 1983, fourteen months after receiving her second IUD, Ms. Roth suffered extreme pelvic pain that forced her to go to a hospital emergency room. Dr. R.M. Carney removed the IUD, and Ms. Roth stated he told her she never should have had the second IUD inserted. According to Ms. Roth, she did not ask and was not told why the IUD was removed. Her physical problems continued after the removal. Approximately ten days after the procedure, Dr. Kuncaitis assessed her condition as “resolved salpingi-tis.” Ms. Roth underwent more extensive diagnostic procedures three months later. These tests disclosed chronic pelvic inflammatory disease. Dr. Wilson’s records reflect that Ms. Roth “states she has had to be on a considerable amount of antibiotics since July and cannot understand why she keeps having reoccurrences of infections despite the removal of the IUD.” Dr. Kuncaitis testified he knew by July 1984 that Ms. Roth’s IUD was at least a contributing cause of her acute endometritis and acute salpingitis, and that it is a reasonable assumption that he so told her, as is his practice.
Ms. Roth states that she knew in October 1984 that she suffered from an infection of *1306her uterus and fallopian tubes that could affect her fertility. Faced with Ms. Roth’s deteriorating condition, Dr. Kuncaitis subsequently referred her to two gynecologists. She consulted Dr. Stanley W. Greenwald in November 1984. He considered her available options to be simply accepting the pain or undergoing surgery. Ms. Roth does not recall asking Dr. Greenwald about the cause of her physical problems. Two years later, Ms. Roth consulted a second gynecologist, Dr. Barbara Beatty, about the desirability of a hysterectomy. Ms. Roth does not recall discussing the cause of her pelvic inflammatory disease or the possibility of a link between pelvic inflammatory disease and IUD use. If asked, however, Dr. Beatty stated she could have told Ms. Roth that the two episodes of pelvic inflammatory disease were “IUD associated salpingitis.”3
On March 13, 1987, Ms. Roth underwent a total abdominal hysterectomy (i.e., removal of the uterus) and bilateral salpingo-oopho-rectomy (i.e., removal of the ovaries and tubes). According to Ms. Roth, she first learned of the possible connection between her condition and her IUDs in 1988 when CNN broadcast a report about a woman with similar symptoms. She denies any awareness of the many earlier widely-circulated articles discussing the possible connection between IUDs and pelvic inflammatory disease. The Roths filed this action on March 3, 1989.
The district court concluded that the factual record supported summary judgment in favor of Searle because Iowa’s two-year statute of limitations barred the Roths’ claims. Roth v. G.D. Searle & Co., No. 4-89-7073, slip op. at 7, 1992 WL 672905 (Dec. 28, 1992). In reviewing the district court’s entry of summary judgment, we apply the same standard as the district court. Trnka v. Elanco Products Co., 709 F.2d 1223, 1225 (8th Cir.1983). We view all facts in the light most favorable to the non-moving party, and give that party the benefit of all reasonable inferences that can be drawn from the facts. United States v. Columbia, 914 F.2d 151, 153 (8th Cir.1990); Woodsmith Pub. Co. v. Meredith Corp., 904 F.2d 1244, 1247 (8th Cir.1990). The court should grant summary judgment if the record, so considered, reveals no genuine issue of material fact and the moving party is entitled to judgment as a matter of law. Fed.R.Civ.P. 56; Kuhnert v. John Morrell & Co. Meat Packing, Inc., 5 F.3d 303, 304 (8th Cir.1993). The requirement that a fact dispute be genuine means that “the mere existence of some alleged factual dispute between the parties will not defeat an otherwise properly supported motion for summary judgment.” Anderson v. Liberty Lobby, Inc., 477 U.S. 242, 247-48, 106 S.Ct. 2505, 2509-10, 91 L.Ed.2d 202 (1986). We review de novo, without deference, the district court’s interpretation of state law. Salve Regina College v. Russell, 499 U.S. 225, 231-32, 111 S.Ct. 1217, 1221, 113 L.Ed.2d 190 (1991).
Under Iowa law, the “statute of limitations begins to run when the injured person discovers or in the exercise of reasonable care should have discovered the allegedly wrongful act.” Franzen v. Deere & Co., 377 N.W.2d 660, 662 (Iowa 1985). Actual knowledge of one’s injury or claim is not required. Sparks v. Metalcraft, Inc., 408 N.W.2d 347, 351 (Iowa 1987). “The statute begins to run when the person gains knowledge sufficient to put him on inquiry.” Id. Once the plaintiff gains such knowledge, the “plaintiff is charged with knowledge of facts that would have been disclosed by a reasonably diligent investigation.” Id. Moreover, “the duty to investigate does not depend on exact knowledge of the nature of the problem that caused the injury.” Franzen, 377 N.W.2d at 662. Rather, “[i]t is sufficient that the person be aware that a problem existed.” Id.
The Roths argue that there is a genuine issue of fact as to whether Ms. Roth should have discovered her claims before March 1987, and therefore, the district court erred in entering summary judgment against them. The district court held that the undisputed facts show “that [Ms.] Roth knew facts sufficient to put her on inquiry notice, and reasonable inquiry would have led her to discov*1307er her potential claims against defendant before March 3, 1987.” The court recounted several facts in support of its position. First, the court stated that Dr. Kuncaitis gave Ms. Roth a “detailed patient brochure warning of PID,” which she “briefly read through.” Slip op. at 7. The court also found undisputed evidence that Dr. Kuncaitis warned Ms. Roth of at least some IUD-assoeiated risks and that Dr. Carney informed her that she never should have had a second IUD inserted. Id. Moreover, the court emphasized that had the Roths asked Dr. Beatty about the cause of her pelvic inflammatory disease, she would have learned that her condition was “IUD associated.” Id. Finally, the court acknowledged the “considerable media publicity” during the mid-1980s highlighting Cu-7 litigation and the possible link between IUDs and pelvic inflammatory disease. Id.
For the first time on appeal the Roth’s challenge some of the court’s “undisputed” facts. They question whether the brochure Ms. Roth received was the same brochure that Searle presented at her deposition. The Roths also argue that Dr. Kuneaitis’ warnings were ineffective insofar as he warned Ms. Roth only about sexually transmitted risks, and not about the non-sexually transmitted infection which she allegedly developed. If a party fails to raise an issue for resolution by the district court, however, that issue may not be raised before this court. Diercks v. Durham, 959 F.2d 710, 713-14 (8th Cir.1992); Clarke v. Bowen, 843 F.2d 271, 273 (8th Cir.1988). The Roths did not raise these concerns in their opposition to Searle’s motion for summary judgment. We reject the Roths’ attempts to raise these issues for the first time before this court. “The district courts cannot be expected to consider matters that the parties have not expressly called to their attention, even when such matters arguably are within the scope of the issues that the parties have raised.” Stafford v. Ford Motor Co., 790 F.2d 702, 706 (8th Cir.1986). A contrary result “could encourage a party to ‘sandbag’ at the district court level, only then to play his ‘ace in the hole’ before the appellate court.” Id.
The Roths’ remaining arguments involve their assertion that the district court erred in concluding that, based on the undisputed facts, Searle should prevail as a matter of law. They offer three reasons why the district court should have found their claims to be timely filed: (1) the Iowa discovery rule extends the time for filing when a plaintiff, such as Ms. Roth, suffers from latent injuries; (2) Searle’s fraudulent concealment of the Roths’ cause of action tolled the statute of limitations; and (3) Searle should be equitably estopped from raising a statute of limitations defense.
We first consider the Roths’ contention that their claims were timely filed. The discovery rule protects plaintiffs who were “unaware of the accrual of a claim and could not have been aware of it in the exercise of reasonable diligence.” Chrischilles v. Griswold, 150 N.W.2d 94, 100-01 (Iowa 1967). Iowa law recognizes the discovery rule for product liability actions brought by consumers of medical products. Wilber v. Owens-Corning Fiberglass Corp., 476 N.W.2d 74, 75 (Iowa 1991). The rule “is applied in [certain] cases to prevent the unfairness which would result from assuming a plaintiff was aware of facts which were ‘unknown and inherently unknowable.’” Id. (quoting LeBeau v. Dimig, 446 N.W.2d 800, 802 (Iowa 1987)). The relevant question is when Ms. Roth knew or should have known of her injuries and their possible connection to her IUD. Sparks, 408 N.W.2d at 351. “On that date, [the plaintiff] is charged with knowledge of facts that would have been disclosed by a reasonably diligent investigation.” Id. (quoting Franzen, 377 N.W.2d at 662).
Searle contends that, under Iowa law, the statute of limitations period begins running when earlier, less-serious injuries (i.e., Ms. Roth’s early pelvic inflammation) manifest themselves, not when a later more-serious injury (i.e., chronic PID and infertility) develops.4 We need not decide this difficult issue of state law because Ms. Roth obviously *1308learned of the existence of her injuries no later than November 11, 1986, when she obtained a second opinion from Dr. Beatty about the possibility of a hysterectomy and a bilateral salpingo-oophorectomy. It was because she knew of the relative seriousness of her injuries that Ms. Roth sought Dr. Beatty’s opinion.
The district court concluded that the undisputed facts established that Ms. Roth “knew facts sufficient to put her on inquiry notice, and reasonable inquiry would have led her to discover her potential claims against [Searle] before March 3,1987.” Slip op. at 7. We conclude that the district court did not err in so ruling.
First, the brochures given to Ms. Roth specifically warned of “PELVIC INFECTION INCLUDING INFLAMMATION.” Moreover, the brochures plainly state that the insertion of an IUD “COULD DECREASE FUTURE CHANCES OF GETTING PREGNANT OR EVEN PREVENT IT AND REQUIRE MAJOR SURGERY.” Ms. Roth admits briefly reading at least one brochure. After removing Ms. Roth’s second Cu-7 in June 1983, Dr. Carney informed her that she should never have had the second device inserted. Collectively, these statements should have alerted Ms. Roth to the possibility of a causal link between the IUD and her disease well before March 1987.5 Again, under Iowa law, actual knowledge of a causal relationship is not required to begin the running of the statute of limitations. Sparks, 408 N.W.2d at 351-52; Franzen, 377 N.W.2d at 662.
The Roths next argue that the district court erred in refusing to toll the statute of limitations because of Searle’s fraudulent concealment of their cause of action. Iowa courts apply the fraudulent concealment doctrine if a plaintiff shows: (1) an affirmative act by the defendant to conceal the cause of action, and (2) that the plaintiff diligently attempted to discover his or her cause of action. Kurtz v. Trepp, 375 N.W.2d 280, 282 (Iowa Ct.App.1985); Pride v. Peterson, 173 N.W.2d 549, 555 (Iowa 1970). After considering the Roths’ contention that they made these showings or at least raised material questions of fact, the district court dismissed their fraudulent concealment claim with little comment. Slip op. at 7 n. 3.
The record read in the light most favorable to the Roths, gives some support to the proposition that Searle sought at least to downplay, if not suppress, information linking Cu-7s to pelvic inflammatory disease and fertility. The Roths point to 1979 internal company reports and memoranda. There are, on the other hand, the patient brochures we have referred to above, and the evidence that Dr. Kuneaitis and Dr. Beatty were both aware in 1984 and 1986 that the IUD was associated with pelvic infection such as Ms. Roth’s. Even assuming that the conflicting evidence meets the first element of fraudulent concealment, the Roths’ claim founders on the second element.
To avail themselves of Iowa’s fraudulent concealment doctrine, the Roths must also prove that they made diligent attempts to discover their cause of action. The Roths argue that they diligently attempted to try to find the cause of Ms. Roth’s problems. Ms. Roth did, in fact, question Dr. Kuneaitis when her physical problems first appeared, but at that time Dr. Kuneaitis did not know the cause. Ms. Roth, however, later failed to pursue the issue despite being given ample opportunity. When Dr. Carney removed her second IUD, he told her that she should never have had another IUD inserted. Ms. Roth failed to explore the basis for this opinion. Nor did she question either of the gynecologists whom she consulted after her injuries became more severe. Had Ms. Roth inquired of the doctors, Dr. Kuneaitis and Dr. Beatty made clear that she would have been told, at the very least, that her condition was IUD-associated. Iowa law requires a reasonably diligent investigation. By failing to pursue her investigation beyond the preliminary questioning of Dr. Kuneaitis, Ms. Roth failed to meet the obligations imposed *1309on her, and her fraudulent concealment claim fails.
The Roths’ final argument focuses on the perceived harshness and unfairness of the unavailability of the fraudulent concealment doctrine. The district court rejected the Roths’ argument that Searle should be equitably estopped from asserting a statute of limitations defense. Slip op. at 6 n. 3. Iowa does recognize equitable estoppel as a defense to the application of a time-bar statute. Beeck v. Aquaslide ‘N’ Dive Corp., 350 N.W.2d 149, 157 (Iowa 1984). This doctrine prevents a party from taking an unconscionable advantage from his own wrongful conduct by asserting his strict legal rights. See Meier v. Alfa-Laval, Inc., 454 N.W.2d 576, 579-80 (Iowa 1990).
There are four elements of equitable estop-pel under Iowa law, revolving around misrepresentation or concealment. Beeck, 350 N.W.2d at 158; Bradshaw v. Wahonda Club, 476 N.W.2d 743, 748 (Iowa Ct.App.1991). Each must be proven by clear and convincing evidence. Beeck, 350 N.W.2d at 157.
Of these, the existence of misrepresentation or concealment is the most significant issue in this ease. Although the Roths contend that virtually any false representation or concealment of facts relevant to the case satisfies this element, we read the Iowa cases applying this theory to limitations issues to require a far more specific misrepresentation or concealment. See Meier, 454 N.W.2d at 580; Beeck, 350 N.W.2d at 158 (where defendant allegedly concealed true manufacturer’s identity, plaintiff could prevail only by showing that the defendant “falsely represented or concealed its identity as the true manufacturer and that its identity was a material fact”). In Meier, the Iowa Supreme Court considered whether certain repairs and assurances that the repairs cured the defect gave rise to equitable estoppel. The court found that “there must be some evidence that such repairs and assertions were not only made to conceal the true condition of the product, but also with the intent to mislead the injured party into the trap of the time bar.” 454 N.W.2d at 580. The court found nothing to indicate that the defendant’s repairs were merely “an attempt to lull the plaintiffs into inaction.” Id. The Roths’ attack on Searle’s course of conduct goes to the merits of their claim, but they do not show that the claimed acts by Searle were intended to mislead them, or others like them, into “the trap of the time bar.” Meier, 454 N.W.2d at 580.
Searle contends that the Roths also failed to establish another required element of their equitable estoppel claim — that they lacked knowledge of a possible link between Cu-7 and Ms. Roth’s injuries. In light of our holding that any misrepresentations by Searle were not specific enough to trigger Iowa’s equitable estoppel doctrine, we need not consider whether the Roths have met this additional element. Considering this record, we conclude that the Roths did not establish the elements of equitable estoppel by clear and convincing evidence, and thus the district court did not err in applying Iowa’s time bar.
We have considered the Roths’ remaining arguments and find them without merit. Accordingly, we affirm the district court’s grant of summary judgment to Searle.
. The Honorable Harold D. Vietor, United States District Judge for the Southern District of Iowa.
. The brochure gave various warnings and listed potential adverse reactions, including:
‘vaginal discharge and infection
* inflammation of the lining of the uterus
* inflammation of the lining of the urinary bladder
‘PELVIC INFECTION INCLUDING INFLAMMATION OF THE FALLOPIAN TUBES, WHICH MAY DAMAGE OR BLOCK THEM. (THIS COULD DECREASE FUTURE CHANCES OF GETTING PREGNANT OR EVEN PREVENT IT AND REQUIRE MAJOR SURGERY).
(Emphasis in the original).
The patient brochure also stated:
“Warnings.
1. Call your doctor for any of the following reasons: * * *
b. Pelvic pain and cramps, especially after the first two or three cycles following insertion, could mean an infection has developed requiring treatment.
Pelvic infections have been reported following insertion of a Cu-7.... Most infections can be eliminated by antibiotic therapy, but if not, the Cu-7 should be removed.
An increased risk of pelvic infection associated with the use of IUDs has been reported. While unconfirmed, this risk appears to be greatest for young women who have never had a baby and/or who have many sexual partners. Pelvic infection can be severe and result in abscesses of the ovaries and tubes, or in general peritonitis. Pelvic infection may include inflammation of the fallopian tubes, which can become damaged and blocked. This could decrease future chances of getting pregnant or even prevent it and require major surgery. Therefore, you should report any symptoms of pelvic infection to your doctor immediately. These symptoms include: new development of menstrual disorders (prolonged or heavy bleeding), unusual vaginal discharge, abdominal or pelvic pain, painful intercourse, and fever. The decision to use any IUD in a particular case must be made by the woman and her doctor with the consideration of a possible deleterious effect on future fertility.
. According to Dr. Beatty, this term reflects only the fact that the infection occurred during IUD use. Dr. Beatty declined to comment on whether a causal connection existed.
. Some case law supports Searle’s position. See LeBeau, 446 N.W.2d at 802; but see Wilber, 476 N.W.2d at 75, 78. This issue need not be finally resolved by this court because all of Ms. Roth's injuries developed before 1986 — still outside the applicable two-year statute of limitations period.
. The question before us is whether Ms. Roth knew facts which placed her on inquiry notice, thereby triggering the statute of limitations. Whether Searle's warnings were inadequate or deficient in some other sense is simply not relevant to this issue.