We present a case of kidney rupture following ... kidney, but the renal parenchyma and ureters could not be ... model for the diagnosis of ectopic pregnancy.1 I ...
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19. Goldberg BB. Evaluation of ascites by ultrasound. Radiology. 1970; 96(7): 15–22. 20. Jehle D, Abrams B, Sukumvanich P,
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Seibel R, Moscati R. Ultrasound for the detection of intraperitoneal fluid: the role of Trendelenburg positioning [abstract]. Acad Emerg Med. 1995; 2:407.
Kidney Rupture Following Extracorporeal Shock Wave Lithotripsy We present a case of kidney rupture following extracorporeal shock wave lithotripsy (ESWL) that presented to a university-based ED. The patient’s chief complaints were persistent flank pain and anuria. His flank pain did not subside despite aggressive pain management in the ED. Surgical exploration revealed multiple lacerations in the left kidney. Although hemodynamic instability was never detected, the patient underwent left nephrectomy after reparative surgical intervention had failed.
CASE REPORT A 52-year-old male presented to our ED with severe flank pain for the previous three to four hours and anuria for two hours. His medical history was unremarkable except for an attack of ureteral colic eight years ago. For the last three days, he had experienced colicky flank pain. On the day of presentation, he was diagnosed as having left urolithiasis by positive ultrasonographic examination done at a private medical center where he had then undergone ESWL. His current complaint has persisted since the procedure earlier in the day. Because of increased pain intensity, two vials of diclofenac sodium had been administered IM at the private medical center. This outpatient treatment failed to alleviate the pain and the patient presented to our ED three hours following completion of the ESWL procedure. On ED presentation the patient’s vital signs were within normal limits. He complained of intractable abdominal and left-sided flank pain as well as dysuria and urinary frequency until the last two hours. In the last two hours prior to ED presentation, he had no urinary output. Appetite and bowel habits were as usual. The physical examination revealed an anxious, fully oriented pa-
tient with no abdominal tenderness or guarding. Bowel sounds were normal and rebound tenderness was absent. The patient had marked tenderness on costovertebral angle palpation on the left. Laboratory studies disclosed a slightly elevated BUN and creatinine levels (36 and 1.4 mg/dL, respectively), and a normal complete blood count. The patient received 200 mL of normal saline infusion IV and diclofenac sodium IM. He was unable to give a urine specimen during the four-hour period in the ED. Persistent pain necessitated IV morphine and derivatives (fentanyl), although they were not effective. An abdominal ultrasound examination revealed a moderately enlarged left kidney, but the renal parenchyma and ureters could not be adequately visualized. Abdominal CT disclosed a perirenal hematoma measuring 12 ⫻ 8 cm. A urologic consultation was obtained, and the patient, whose clinical course and vital signs had been stable, was transferred to another hospital in the vicinity due to lack of admission beds. Laparotomy was subsequently performed and the kidney capsule was found to have three burst-shaped lacerations: two anteriorly and one medially. Reparative surgical efforts failed to stop the bleeding and a left nephrectomy was performed. The patient had an uneventful postoperative follow-up and urinary output returned to normal levels in 24 hours.
DISCUSSION Abdominal and flank pain is one of the most common reasons adult patients seek emergency medical care. Emergency physicians assume the task of differentiating life-threatening causes of abdominal pain from so-called ‘‘nonspecific abdominal pain.’’ Besides physical examination
findings, failure to achieve pain relief despite high-dose analgesic medications is an important clue to sort out the life-threatening diseases from others. Patients with urolithiasis commonly undergo ESWL procedure. Case reports describe scrotal hematoma1 and acute renal failure from subcapsular hematoma2 as complications of ESWL. Perirenal hematoma,3 rupture of the kidney,4 and kidney lacerations5 following ESWL procedure have also been reported. However, our case appears to be the only report of multiple lacerations of kidney following ESWL that eventually required a nephrectomy. Perirenal hematoma following ESWL is detected in 15% to 30% of the cases.2 Risk factors that can predispose ESWL patients to perirenal hematoma include coagulopathy, hypertension, and aspirin use. None of these risk factors were present in our patient. The kidney rupture that occurred in this patient may have been due to a technical problem during the ESWL procedure itself. Solid organ lacerations should be considered and sought via adjunctive imaging studies, especially if the patient presents with persistent abdominal pain and a history of ESWL. Because of the abundant vasculature of the kidney, visceral injury may cause severe bleeding. We suggest that the differential diagnosis of patients who present with abdominal pain and a history of ESWL should include visceral organ injury and internal bleeding.—D. NIYAZI OZUCELIK, MD, OZGUR KARCIOGLU, MD, Dokuz Eylul University Medical School, Emergency Department, Izmir, Turkey Key words. kidney; rupture; extracorporeal shock wave lithotripsy.
References 1. Kay MC, Streem SB, Yost A. Scrotal hematoma resulting from extracorporeal shock wave lithotripsy for a distal ureteral calculus. J Urol. 1993; 150(2 pt I): 481–2. 2. Lipski B, Miller J, Rigaud G, Stack G, Marsh C. Acute renal failure from a supcapsular hematoma in a solitary kidney; an unusual complication of extracorporeal shock wave lithotripsy. J Urol. 1997; 157:6, 2245. 3. Knapp PM, Kulb TB, Lingeman JE, et al. Extracorporeal shock wave lithotripsy-induced perirenal hematomas. J
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Urol. 1988; 139:4, 700–3. 4. Seddiki A, Thomas J, Tobelem G, et al. A rare complication of extracorporeal shock wave lithotripsy: rupture of kidney. Apropos of a case. J Urol (Paris).
1991; 97:4 – 5, 224 – 7. 5. Fukumori T, Yamamoto A, Ashida S, et al. Extracorporeal shock wave lithotripsy-induced renal laceration. Int J Urol. 1997: 4:4, 419–21.
CORRESPONDENCE Reporting Clinical Prediction Rules To the Editor:—I read with interest the article by Dr. Buckley et al. on the derivation of a clinical prediction model for the diagnosis of ectopic pregnancy.1 I am writing out of concern about methodologic issues pertaining to this study. The authors correctly stated that they had not validated their rule as part of this project. There are several ways to obtain data for the validation of derived prediction rules. Resampling techniques, such as the jackknife and bootstrap methods, although computationally cumbersome, allow for validation of a rule by using data from the original study population.2 Another reasonable option is to delay the dissemination of a prediction rule until the validation phase of the study is completed. The validation phase of the development of a prediction rule may completely invalidate the results.2 Publishing such incomplete results gives the reader the impression that the rule is valid and introduces potentially false information into the field. In addition, the authors performed only univariate tests on the clinical variables. How were confounders controlled for? Why did the authors not perform a multivariate regression analysis? The authors did not report interrater reliability. Their results could be greatly affected by interviewer bias.3 This is supported by the fact that emergency medicine attending physicians were examiners in 18% of ectopic pregnancies but only 5% of non-ectopic pregnancies, more than a threefold difference that was found to be statistically significant but not accounted for. Publication of this article may cause some readers to believe that a prediction rule has been generated by the authors and, unfortunately, may lead some to alter their clinical practice. Current standards support
that every patient at risk for ectopic pregnancy who presents with firsttrimester abdominal pain or vaginal bleeding undergo a pelvic ultrasound examination.4,5 The results of this study should in no way change that.—ANDREW T. MCAFEE, MD, Department of Emergency Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA Key words. ectopic pregnancy; clinical prediction rule; multivariate analysis; interrater reliability.
References 1. Buckley RG, King KJ, Disney JD, Ambroz PK, Gorman JD, Klausen JH. Derivation of a clinical prediction model for the emergency department diagnosis of ectopic pregnancy. Acad Emerg Med. 1998; 5:951–60. 2. Wasson JH, Sox HC, Neff RK, Goldman L. Clinical prediction rules. Applications and methodologic standards. N Engl J Med. 1985; 313:793–9. 3. Sackett DL. A primer on the precision and accuracy of the clinical examination. JAMA. 1992; 267:2638–44. 4. Kaplan BC, Dart RG, Moskos M, et al. Ectopic pregnancy: prospective study with improved diagnostic accuracy. Ann Emerg Med. 1996; 28:10–7. 5. Counselman FL, Shaar GS, Heller RA, King DK. Quantitative -hCG levels less than 1,000 mIU/mL in patients with ectopic pregnancy: pelvic ultrasound still useful. J Emerg Med. 1998; 5:699–703.
● In reply:—We thank Dr. McAfee for his detailed observations regarding the methodologic aspects of our study. The most important was the need to await prospective validation before being used in clinical practice. The second important limitation was our inability to measure interrater reliability. Both of these were thoroughly discussed in our paper.1 Nonetheless, it is important
665 that they be highlighted and emphasized again. We chose to use recursive partitioning, rather than regression, because it allows a clinically intuitive algorithm to be constructed rather than a weighted score.2 Logistic regression also tends to generate models that have high overall accuracy but that suffer from unacceptably low sensitivity or specificity—rendering them less useful for clinical application.3 The suggestion of using bootstrap or jackknife cross-validation techniques is an interesting one. The downside of using these techniques is that they simply reestimate the error rate using the same sample—being subjected to the same biases and sampling errors of the original derivation set.4 Retesting a clinical prediction model on an independent set of patients is by far the superior approach.5 So why did we publish our results? We elected to publish our derivation set model so that a more detailed and lengthy explanation of our methods, results, and design limitations could be made available (including an appendix summarizing our data collection form), in anticipation of referencing them when a more condensed report of the validation set is published. It should be noted that we submitted this manuscript to Academic Emergency Medicine as a ‘‘preliminary report’’ —a section for ‘‘hypothesis-generating studies.’’ Perhaps this would have been a more appropriate section, and may warrant a comment from the editors. It is not uncommon, however, to find derivation sets published as ‘‘original contributions’’ and even ‘‘lead articles.’’ 3,6,7 A preliminary report of our validation set results was presented at last October’s Research Forum at the American College of Emergency Physicians’ Scientific Assembly.8 We agree that ultrasonography is critical in the evaluation of symptomatic first-trimester patients. However, should the emergency physician remove any consideration of clinical findings from the medical decision making process when ultrasonography is neither diagnostic nor readily available? The goal of our study was to help clinicians estimate the pretest probability of ectopic pregnancy. We did this by describing
