- Email: [email protected]
Interstitial pregnancy: A potential for misdiagnosis of ectopic pregnancy with emergency department ultrasonography
OBSTETRICS AND GYNECOLOGY/CASE REPORT
Interstitial Pregnancy: A Potential for Misdiagnosis of Ectopic Pregnancy With Emergency Department Ultrasonography
Christopher DeWitt, MD Jean Abbott, MD From Denver Health Medical Center Residency in Emergency Medicine (DeWitt), and the Division of Emergency Medicine, Department of Surgery, University of Colorado Health Sciences Center (Abbott), Denver, CO.
Interstitial pregnancy is a rare and dangerous form of ectopic pregnancy that can be mistaken for a normal intrauterine pregnancy on ultrasonography, leading to catastrophic results. Increasingly, emergency physicians are using ultrasonography to diagnose intrauterine pregnancy. Emergency physicians should be aware of the potential for mistaking an interstitial pregnancy for an intrauterine pregnancy. We present a case report of an interstitial pregnancy misdiagnosed as an intrauterine pregnancy and discuss ultrasonographic and physical examination findings to help differentiate interstitial pregnancy from an intrauterine pregnancy. [DeWitt C, Abbott J. Interstitial pregnancy: a potential for misdiagnosis of ectopic pregnancy with emergency department ultrasonography. Ann Emerg Med. July 2002;40:106-109.]
Copyright © 2002 by the American College of Emergency Physicians. 0196-0644/2002/$35.00 + 0 47/1/125426 doi:10.1067/mem.2002.125426
1 0 6
ANNALS OF EMERGENCY MEDICINE
40:1
JULY 2002
INTERSTITIAL PREGNANCY DeWitt & Abbott
INTRODUCTION
Interstitial pregnancy is a rare and dangerous form of ectopic pregnancy that can be mistaken for a normal intrauterine pregnancy on ultrasonography. Because more emergency physicians are using bedside ultrasonography and because a missed interstitial pregnancy can be catastrophic, this potential pitfall in the diagnosis of intrauterine pregnancy is important to recognize. We present a case from our institution, a tertiary care teaching hospital, of an interstitial pregnancy misdiagnosed as a normal intrauterine pregnancy by means of emergency department ultrasonography. CASE REPORT
A 21-year-old gravida 3, para 1, 8 3⁄7 weeks’ pregnant by last menstrual period presented to the ED complaining of abdominal pain, nausea, nonbloody emesis, and diaphoresis. The abdominal pain started suddenly approximately 1 hour before presentation. She denied any fever, vaginal bleeding, vaginal discharge, diarrhea, or dysuria. Her history was remarkable for a previous spontaneous abortion. She was currently taking Macrobid (nitrofurantoin monohydrate/macrocrystals) for a urinary tract infection. She denied any previous surgeries. On initial examination, the patient appeared to be in mild discomfort. She was afebrile, with blood pressure 90/58 mm Hg and pulse rate 81 beats/min. Abdominal examination was without tenderness or peritoneal signs, and bowel sounds were present. Pelvic examination showed no bleeding or discharge. There was mild cervical motion tenderness and mild uterine motion tenderness. There were no adnexal masses or tenderness. Rectal examination demonstrated hemoccultnegative, brown stool. Intravenous fluids were started. An initial hematocrit level was 37.2%, and urinalysis was positive for ketones and protein. The attending emergency physician, who had previously completed a departmental ultrasonography certification process that included at least 50 examinations of first-trimester intrauterine pregnancies, performed a bedside transabdominal ultrasonographic scan with a Toshiba ECCO-
JULY 2002
40:1
ANNALS OF EMERGENCY MEDICINE
CEE (Toshiba American Medical Systems, Tustin, CA). The ultrasonographic scan was interpreted as an 8 1⁄7week intrauterine pregnancy on the basis of crownrump length with heart tones present. The ovaries were not examined. Approximately 3 hours after admission, the patient’s abdominal pain had decreased, and she was tolerating oral fluids. Obstetrics was consulted by telephone and recommended follow-up in the clinic in 1 to 2 days. However, just before discharge, the patient had a syncopal episode, followed by 1 episode of nonbloody emesis. A repeat hematocrit level was 29%, and blood glucose concentration was 129 mg/dL. A repeat abdominal ultrasonographic scan by the attending emergency physician demonstrated free fluid in Morrison’s pouch. Obstetrics then examined the patient in the ED and recommended a formal pelvic ultrasonogram. The pelvic ultrasonogram performed by the radiology department demonstrated a large amount of free fluid in the peritoneal cavity, with echogenic material in the pelvis consistent with clotted blood. There was no intrauterine pregnancy identified. The endometrial stripe measured 15 mm. Findings were consistent with a ruptured ectopic pregnancy. A repeat hematocrit level after the ultrasonogram was 24%. The patient was taken to the operating room, where she underwent a right cornual wedge resection after finding a ruptured and bleeding right interstitial ectopic pregnancy with approximately 400 mL of clotted blood in the peritoneum. The patient received 3 units of packed RBCs, and the remainder of her hospital course was uneventful. She was discharged on postoperative day 3. On retrospective review, the original still ultrasonographic images demonstrated a thin, asymmetric myometrial mantle, as seen in the Figure. DISCUSSION
Interstitial pregnancy is an ectopic pregnancy located in the fallopian tube as it transverses the uterine wall, with the main portion of the gestational sac located outside the uterine cavity. Although previously known as a cornual pregnancy, that term is now reserved for preg-
1 0 7
INTERSTITIAL PREGNANCY DeWitt & Abbott
nancies that occur in the rudimentary horn of a congenital bicornuate uterus. Interstitial pregnancy accounts for 2% to 3% of all ectopic pregnancies1-7 but carries a mortality rate of more than twice that of other tubal pregnancies (2.2%3,4,8,9 versus <1%3,8,9). Because the implant site is easily distensible, dilates painlessly, and is
Figure.
A, Transabdominal ultrasonogram of the superior portion of the uterus in the transverse plane. The gestational sac, containing the fetus and yolk sac, is high in the fundus and surrounded by a thinned, asymmetric myometrial mantle. The umbilical cord is indicated by the plus sign. B, Line drawing of structures seen on the ultrasonographic image. A thinned, asymmetric myometrial mantle surrounds the fetus and yolk sac. Arrows indicate the right side of the uterus, where the myometrial mantle is thinned and measures less than 5 mm in width.
A
B Yolk Sac Myometrium
Fetus
1.0 cm
1 0 8
highly vascular, interstitial pregnancies tend to rupture at a later gestational age (usually between 8 and 16 weeks’ gestation5) and cause massive intraperitoneal bleeding. Risk factors for interstitial pregnancy are similar to those of other tubal pregnancies (pelvic inflammatory disease, intrauterine device in place, previous tubal surgery), but patients who have had a cornual anastomosis are at even greater risk.8 Patients with interstitial pregnancies tend to have presentations similar to those of other ectopic pregnancies, with a history of amenorrhea, vaginal bleeding, and abdominal pain. Because interstitial pregnancies can develop to later gestational ages, fetal heart tones might be present by ultrasonography2,8,10 and theoretically can be determined on auscultation. There are also case reports of interstitial pregnancies delivering at term.8 The pelvic examination might reveal a broadbased palpable mass extending out from the uterine angle (Baart de la Faille’s sign),8,11 the fundus might be displaced to the contralateral side with rotation of the uterus and elevation of the affected cornu (Ruge-Simon Syndrome),1,8,11 or the affected side might have greater mobility and feel softer than the remainder of the uterus (Zimmerman-Drazancic’s sign).11 However, given the poor reliability of pelvic examination, the utility of such signs is doubtful. Ultrasonographic findings reported to be suggestive of interstitial pregnancy include the following: • a gestational sac covered by an asymmetric, thin, or incomplete myometrial mantle3,5,8,9,12 (some authors have suggested that the gestational sac of a normal intrauterine pregnancy must be surrounded by 5 mm of myometrium in all planes, but the specificity of this has yet to be investigated13,14); • an empty uterine cavity with a central linear echo2,5,8,12 (the central echo represents the interface between the 2 layers of endometrium and is obliterated as early as 3 weeks’ gestation in a normal intrauterine pregnancy2); • a very lateral or eccentrically located gestational sac (ie, the main portion of the gestational sac is outside the uterine cavity1,5,7-10);
ANNALS OF EMERGENCY MEDICINE
40:1
JULY 2002
INTERSTITIAL PREGNANCY DeWitt & Abbott
• a gestational sac not seen above the level of the internal os in the longitudinal plane of the uterus3,8; • myometrium located between the gestational sac and uterine cavity8; and • a gestational sac seen high in the uterine fundus (anatomically, the fallopian tube intersects the uterus at the upper portion of the fundus). The most consistent ultrasonographic findings of interstitial pregnancy are a gestational sac eccentric to an empty endometrial cavity and an asymmetric or incomplete myometrial mantle.3,9 An eccentrically located gestational sac, or an asymmetric myometrial mantle, can also be seen in a cornual pregnancy, in a pregnancy in a myomatous uterus,2,9 in a patient with an overly distended bladder,9 and in an angular pregnancy (intrauterine pregnancy at the extreme lateral angle of the uterine cavity).2,12 However, an angular intrauterine pregnancy or an intrauterine pregnancy in a myomatous uterus should still have a substantial amount of myometrium completely surrounding the gestational sac.2 It is also important to identify the ovaries on ultrasonography because a fluid-filled ovarian mass might be mistaken for an ectopic pregnancy.9 In conclusion, the diagnosis of interstitial pregnancy requires a high level of clinical suspicion with a careful pelvic and ultrasonographic examination. If the patient has signs and symptoms of peritoneal leakage despite an apparent intrauterine pregnancy or if the ultrasonogram demonstrates a thin asymmetric myometrium or eccentrically located gestational sac, interstitial pregnancy should be considered. At that point, obstetrics should be consulted, and a formal ultrasonogram should be performed. Additionally, laparoscopy is often needed to confirm the diagnosis.
REFERENCES 1. Chandra P, Koenigsberg M, Rommey S, et al. Unruptured interstitial pregnancy. Obstet Gynecol. 1978;52:612-615. 2. Coady DJ, Snyder JR, Goldstein SR, et al. Ultrasound diagnosis of interstitial pregnancy. N Y State J Med. 1985;85:655-656. 3. Graham M, Cooperberg P. Ultrasound diagnosis of interstitial pregnancy: findings and pitfalls. J Clin Ultrasound. 1979;7:433-437. 4. Maher PJ, Grimwade JC. Cornual pregnancy—diagnosis before rupture. Aust N Z J Obstet Gynecol. 1982;22:172-174. 5. Sherer DM, Tamara A, Singh GS, et al. Transvaginal sonographic diagnosis of an unruptured interstitial pregnancy. J Clin Ultrasound. 1990;18:582-585. 6. Smith H, Hanken H, Brundelet P. Ultrasound diagnosis of interstitial pregnancy. Acta Obstet Gynecol Scand. 1981;60:413-416. 7. Weissman A, Fishman A, Gal D. Interstitial pregnancy: a diagnostic challenge. Int J Gynecol Obstet. 1989;29:373-375. 8. de Boer CN, van Dongen PW, Willemsen WN, et al. Ultrasound diagnosis of interstitial pregnancy. Eur J Obstet Gynecol Reprod Biol. 1992;47:164-166. 9. Jafri S, Loginsky S, Bouffard J, et al. Sonographic detection of interstitial pregnancy. J Clin Ultrasound. 1987;15:253-257. 10. Auslender R, Arodi J, Pascal B, et al. Interstitial pregnancy: early diagnosis by ultrasonography. Am J Obstet Gynecol. 1983;146:717-718. 11. Skulj V, Bunarevic A, Bacic G, et al. Interstitial pregnancy. Am J Obstet Gynecol. 1964;88:596-600. 12. Chen G, Lin M, Lee M. Diagnosis of interstitial pregnancy with sonography. J Clin Ultrasound. 1994;22:439-442. 13. Fleischer AC, Pennell RG, McKee MS, et al. Ectopic pregnancy: features at transvaginal sonography. Radiology. 1990;174:375-378. 14. Levine D. Ectopic pregnancy. In: Callen PW, ed. Ultrasonography in Obstetrics and Gynecology. 4th ed. Philadelphia, PA: Saunders Company; 2000:927-928.
Received for publication July 18, 2001. Revisions received November 2, 2001, and February 11, 2002. Accepted for publication March 19, 2002. Address for reprints: Christopher DeWitt, MD, Denver Health Medical Center Residency in Emergency Medicine, 777 Bannock Street, Denver, CO 80204; 303-436-7142, fax 303-436-7541; E-mail [email protected]. We thank Paul Davidson, MD, and Paul Redstone, MD.
JULY 2002
40:1
ANNALS OF EMERGENCY MEDICINE
1 0 9
Interstitial Pregnancy: A Potential for Misdiagnosis of Ectopic Pregnancy With Emergency Department Ultrasonography
Christopher DeWitt, MD Jean Abbott, MD From Denver Health Medical Center Residency in Emergency Medicine (DeWitt), and the Division of Emergency Medicine, Department of Surgery, University of Colorado Health Sciences Center (Abbott), Denver, CO.
Interstitial pregnancy is a rare and dangerous form of ectopic pregnancy that can be mistaken for a normal intrauterine pregnancy on ultrasonography, leading to catastrophic results. Increasingly, emergency physicians are using ultrasonography to diagnose intrauterine pregnancy. Emergency physicians should be aware of the potential for mistaking an interstitial pregnancy for an intrauterine pregnancy. We present a case report of an interstitial pregnancy misdiagnosed as an intrauterine pregnancy and discuss ultrasonographic and physical examination findings to help differentiate interstitial pregnancy from an intrauterine pregnancy. [DeWitt C, Abbott J. Interstitial pregnancy: a potential for misdiagnosis of ectopic pregnancy with emergency department ultrasonography. Ann Emerg Med. July 2002;40:106-109.]
Copyright © 2002 by the American College of Emergency Physicians. 0196-0644/2002/$35.00 + 0 47/1/125426 doi:10.1067/mem.2002.125426
1 0 6
ANNALS OF EMERGENCY MEDICINE
40:1
JULY 2002
INTERSTITIAL PREGNANCY DeWitt & Abbott
INTRODUCTION
Interstitial pregnancy is a rare and dangerous form of ectopic pregnancy that can be mistaken for a normal intrauterine pregnancy on ultrasonography. Because more emergency physicians are using bedside ultrasonography and because a missed interstitial pregnancy can be catastrophic, this potential pitfall in the diagnosis of intrauterine pregnancy is important to recognize. We present a case from our institution, a tertiary care teaching hospital, of an interstitial pregnancy misdiagnosed as a normal intrauterine pregnancy by means of emergency department ultrasonography. CASE REPORT
A 21-year-old gravida 3, para 1, 8 3⁄7 weeks’ pregnant by last menstrual period presented to the ED complaining of abdominal pain, nausea, nonbloody emesis, and diaphoresis. The abdominal pain started suddenly approximately 1 hour before presentation. She denied any fever, vaginal bleeding, vaginal discharge, diarrhea, or dysuria. Her history was remarkable for a previous spontaneous abortion. She was currently taking Macrobid (nitrofurantoin monohydrate/macrocrystals) for a urinary tract infection. She denied any previous surgeries. On initial examination, the patient appeared to be in mild discomfort. She was afebrile, with blood pressure 90/58 mm Hg and pulse rate 81 beats/min. Abdominal examination was without tenderness or peritoneal signs, and bowel sounds were present. Pelvic examination showed no bleeding or discharge. There was mild cervical motion tenderness and mild uterine motion tenderness. There were no adnexal masses or tenderness. Rectal examination demonstrated hemoccultnegative, brown stool. Intravenous fluids were started. An initial hematocrit level was 37.2%, and urinalysis was positive for ketones and protein. The attending emergency physician, who had previously completed a departmental ultrasonography certification process that included at least 50 examinations of first-trimester intrauterine pregnancies, performed a bedside transabdominal ultrasonographic scan with a Toshiba ECCO-
JULY 2002
40:1
ANNALS OF EMERGENCY MEDICINE
CEE (Toshiba American Medical Systems, Tustin, CA). The ultrasonographic scan was interpreted as an 8 1⁄7week intrauterine pregnancy on the basis of crownrump length with heart tones present. The ovaries were not examined. Approximately 3 hours after admission, the patient’s abdominal pain had decreased, and she was tolerating oral fluids. Obstetrics was consulted by telephone and recommended follow-up in the clinic in 1 to 2 days. However, just before discharge, the patient had a syncopal episode, followed by 1 episode of nonbloody emesis. A repeat hematocrit level was 29%, and blood glucose concentration was 129 mg/dL. A repeat abdominal ultrasonographic scan by the attending emergency physician demonstrated free fluid in Morrison’s pouch. Obstetrics then examined the patient in the ED and recommended a formal pelvic ultrasonogram. The pelvic ultrasonogram performed by the radiology department demonstrated a large amount of free fluid in the peritoneal cavity, with echogenic material in the pelvis consistent with clotted blood. There was no intrauterine pregnancy identified. The endometrial stripe measured 15 mm. Findings were consistent with a ruptured ectopic pregnancy. A repeat hematocrit level after the ultrasonogram was 24%. The patient was taken to the operating room, where she underwent a right cornual wedge resection after finding a ruptured and bleeding right interstitial ectopic pregnancy with approximately 400 mL of clotted blood in the peritoneum. The patient received 3 units of packed RBCs, and the remainder of her hospital course was uneventful. She was discharged on postoperative day 3. On retrospective review, the original still ultrasonographic images demonstrated a thin, asymmetric myometrial mantle, as seen in the Figure. DISCUSSION
Interstitial pregnancy is an ectopic pregnancy located in the fallopian tube as it transverses the uterine wall, with the main portion of the gestational sac located outside the uterine cavity. Although previously known as a cornual pregnancy, that term is now reserved for preg-
1 0 7
INTERSTITIAL PREGNANCY DeWitt & Abbott
nancies that occur in the rudimentary horn of a congenital bicornuate uterus. Interstitial pregnancy accounts for 2% to 3% of all ectopic pregnancies1-7 but carries a mortality rate of more than twice that of other tubal pregnancies (2.2%3,4,8,9 versus <1%3,8,9). Because the implant site is easily distensible, dilates painlessly, and is
Figure.
A, Transabdominal ultrasonogram of the superior portion of the uterus in the transverse plane. The gestational sac, containing the fetus and yolk sac, is high in the fundus and surrounded by a thinned, asymmetric myometrial mantle. The umbilical cord is indicated by the plus sign. B, Line drawing of structures seen on the ultrasonographic image. A thinned, asymmetric myometrial mantle surrounds the fetus and yolk sac. Arrows indicate the right side of the uterus, where the myometrial mantle is thinned and measures less than 5 mm in width.
A
B Yolk Sac Myometrium
Fetus
1.0 cm
1 0 8
highly vascular, interstitial pregnancies tend to rupture at a later gestational age (usually between 8 and 16 weeks’ gestation5) and cause massive intraperitoneal bleeding. Risk factors for interstitial pregnancy are similar to those of other tubal pregnancies (pelvic inflammatory disease, intrauterine device in place, previous tubal surgery), but patients who have had a cornual anastomosis are at even greater risk.8 Patients with interstitial pregnancies tend to have presentations similar to those of other ectopic pregnancies, with a history of amenorrhea, vaginal bleeding, and abdominal pain. Because interstitial pregnancies can develop to later gestational ages, fetal heart tones might be present by ultrasonography2,8,10 and theoretically can be determined on auscultation. There are also case reports of interstitial pregnancies delivering at term.8 The pelvic examination might reveal a broadbased palpable mass extending out from the uterine angle (Baart de la Faille’s sign),8,11 the fundus might be displaced to the contralateral side with rotation of the uterus and elevation of the affected cornu (Ruge-Simon Syndrome),1,8,11 or the affected side might have greater mobility and feel softer than the remainder of the uterus (Zimmerman-Drazancic’s sign).11 However, given the poor reliability of pelvic examination, the utility of such signs is doubtful. Ultrasonographic findings reported to be suggestive of interstitial pregnancy include the following: • a gestational sac covered by an asymmetric, thin, or incomplete myometrial mantle3,5,8,9,12 (some authors have suggested that the gestational sac of a normal intrauterine pregnancy must be surrounded by 5 mm of myometrium in all planes, but the specificity of this has yet to be investigated13,14); • an empty uterine cavity with a central linear echo2,5,8,12 (the central echo represents the interface between the 2 layers of endometrium and is obliterated as early as 3 weeks’ gestation in a normal intrauterine pregnancy2); • a very lateral or eccentrically located gestational sac (ie, the main portion of the gestational sac is outside the uterine cavity1,5,7-10);
ANNALS OF EMERGENCY MEDICINE
40:1
JULY 2002
INTERSTITIAL PREGNANCY DeWitt & Abbott
• a gestational sac not seen above the level of the internal os in the longitudinal plane of the uterus3,8; • myometrium located between the gestational sac and uterine cavity8; and • a gestational sac seen high in the uterine fundus (anatomically, the fallopian tube intersects the uterus at the upper portion of the fundus). The most consistent ultrasonographic findings of interstitial pregnancy are a gestational sac eccentric to an empty endometrial cavity and an asymmetric or incomplete myometrial mantle.3,9 An eccentrically located gestational sac, or an asymmetric myometrial mantle, can also be seen in a cornual pregnancy, in a pregnancy in a myomatous uterus,2,9 in a patient with an overly distended bladder,9 and in an angular pregnancy (intrauterine pregnancy at the extreme lateral angle of the uterine cavity).2,12 However, an angular intrauterine pregnancy or an intrauterine pregnancy in a myomatous uterus should still have a substantial amount of myometrium completely surrounding the gestational sac.2 It is also important to identify the ovaries on ultrasonography because a fluid-filled ovarian mass might be mistaken for an ectopic pregnancy.9 In conclusion, the diagnosis of interstitial pregnancy requires a high level of clinical suspicion with a careful pelvic and ultrasonographic examination. If the patient has signs and symptoms of peritoneal leakage despite an apparent intrauterine pregnancy or if the ultrasonogram demonstrates a thin asymmetric myometrium or eccentrically located gestational sac, interstitial pregnancy should be considered. At that point, obstetrics should be consulted, and a formal ultrasonogram should be performed. Additionally, laparoscopy is often needed to confirm the diagnosis.
REFERENCES 1. Chandra P, Koenigsberg M, Rommey S, et al. Unruptured interstitial pregnancy. Obstet Gynecol. 1978;52:612-615. 2. Coady DJ, Snyder JR, Goldstein SR, et al. Ultrasound diagnosis of interstitial pregnancy. N Y State J Med. 1985;85:655-656. 3. Graham M, Cooperberg P. Ultrasound diagnosis of interstitial pregnancy: findings and pitfalls. J Clin Ultrasound. 1979;7:433-437. 4. Maher PJ, Grimwade JC. Cornual pregnancy—diagnosis before rupture. Aust N Z J Obstet Gynecol. 1982;22:172-174. 5. Sherer DM, Tamara A, Singh GS, et al. Transvaginal sonographic diagnosis of an unruptured interstitial pregnancy. J Clin Ultrasound. 1990;18:582-585. 6. Smith H, Hanken H, Brundelet P. Ultrasound diagnosis of interstitial pregnancy. Acta Obstet Gynecol Scand. 1981;60:413-416. 7. Weissman A, Fishman A, Gal D. Interstitial pregnancy: a diagnostic challenge. Int J Gynecol Obstet. 1989;29:373-375. 8. de Boer CN, van Dongen PW, Willemsen WN, et al. Ultrasound diagnosis of interstitial pregnancy. Eur J Obstet Gynecol Reprod Biol. 1992;47:164-166. 9. Jafri S, Loginsky S, Bouffard J, et al. Sonographic detection of interstitial pregnancy. J Clin Ultrasound. 1987;15:253-257. 10. Auslender R, Arodi J, Pascal B, et al. Interstitial pregnancy: early diagnosis by ultrasonography. Am J Obstet Gynecol. 1983;146:717-718. 11. Skulj V, Bunarevic A, Bacic G, et al. Interstitial pregnancy. Am J Obstet Gynecol. 1964;88:596-600. 12. Chen G, Lin M, Lee M. Diagnosis of interstitial pregnancy with sonography. J Clin Ultrasound. 1994;22:439-442. 13. Fleischer AC, Pennell RG, McKee MS, et al. Ectopic pregnancy: features at transvaginal sonography. Radiology. 1990;174:375-378. 14. Levine D. Ectopic pregnancy. In: Callen PW, ed. Ultrasonography in Obstetrics and Gynecology. 4th ed. Philadelphia, PA: Saunders Company; 2000:927-928.
Received for publication July 18, 2001. Revisions received November 2, 2001, and February 11, 2002. Accepted for publication March 19, 2002. Address for reprints: Christopher DeWitt, MD, Denver Health Medical Center Residency in Emergency Medicine, 777 Bannock Street, Denver, CO 80204; 303-436-7142, fax 303-436-7541; E-mail [email protected]. We thank Paul Davidson, MD, and Paul Redstone, MD.
JULY 2002
40:1
ANNALS OF EMERGENCY MEDICINE
1 0 9