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Assessment of urinary dipstick in patients admitted to an ED for blunt abdominal trauma
YAJEM-56369; No of Pages 4 American Journal of Emergency Medicine xxx (2016) xxx–xxx
Contents lists available at ScienceDirect
American Journal of Emergency Medicine journal homepage: www.elsevier.com/locate/ajem
Assessment of urinary dipstick in patients admitted to an emergency department for blunt abdominal trauma F. Moustafa a,⁎, C. Loze a, B. Pereira b, MA. Vaz c, L. Caumon d, C. Perrier a, J. Schmidt a,e a
Service des urgences, Pôle SAMU-SMUR-Urgences, CHU Gabriel Montpied, Clermont-Ferrand, France Direction de la Recherche Clinique et de l'Innovation, Département de Biostatistiques, CHU Gabriel Montpied, Clermont-Ferrand, France Service de radiologie, CHU Gabriel Montpied, Clermont-Ferrand, France d Service des urgences, CH Aurillac, Aurillac, France e Université d'Auvergne, Clermont-I, UFR de médecine, Clermont-Ferrand, France b c
a r t i c l e
i n f o
Article history: Received 19 October 2016 Received in revised form 16 December 2016 Accepted 16 December 2016 Available online xxxx Keywords: Blunt abdominal trauma Urinalysis Hematuria Emergency
a b s t r a c t Introduction: Clinicians still face significant challenge in predicting intra-abdominal injuries in patients admitted to an emergency department for blunt abdominal trauma. This study was thus designed to investigate the value of dipstick urinalysis in patients with blunt abdominal trauma. Methods: We performed a retrospective, multicenter, cohort study involving patients admitted to the emergency department for abdominal traumas, examined by means of urinary dipstick and abdominal CT scan. The primary endpoint was the correlation between microscopic hematuria detected via dipstick urinalysis (defined by the presence of blood on the dipstick urinalysis but without gross hematuria) and abdominal injury, as evidenced on CT scan. Results: Of the 100 included patients, 56 experienced microscopic hematuria, 17 gross hematuria, and 44 no hematuria. Patients with abdominal injury were more likely to present with hypovolemic shock (odds ratio [OR]: 8.4; 95% confidence interval [CI]: 2.7–26), abdominal wall hematoma (OR: 3.1; 95% CI: 1.2–7.9), abdominal defense (OR: 5.2; 95% CI: 1.8–14.5), or anemia (OR: 3.6; 95% CI: 1.2–10.3). Moreover, dipstick urinalysis was less likely to predict injury, with just 72.2% sensitivity (95% CI: 54.8–85.8), 53.1% specificity (95% CI: 40.2–65.7), and positive and negative predictive values of 46.4% (95% CI: 33.0–60.3) and 77.3% (95% CI: 62.2–88.5), respectively. Conclusion: Dipstick urinalysis was neither adequately specific nor sensitive for predicting abdominal injury and should thus not be used as a key assessment component in patients suffering from blunt abdominal trauma, with physical exam and vital sign assessment the preferred choice. © 2016 Published by Elsevier Inc.
1. Introduction Abdominal injuries account for 15–20% of trauma-related lesions and constitute a leading cause of mortality in 10–30% of patients exhibiting such lesions [1]. They primarily constitute lesions caused by contusion in solid organs (spleen, liver, kidneys, or pancreas) or perforation of hollow organs (duodenum, small intestine, or colon). Whilst clinical diagnosis can be straightforward, with indicators such as pain or abdominal defense, clinical abdominal examination cannot be used to diagnose all patients with intra-abdominal injuries [2,3]. ⁎ Corresponding author at: Service des urgences, Hôpital Gabriel Montpied, 58 rue Montalembert, F-63003 Clermont-Ferrand Cedex 1, France. E-mail addresses: [email protected] (F. Moustafa), [email protected] (C. Loze), [email protected] (B. Pereira), [email protected] (M.A. Vaz), [email protected] (L. Caumon), [email protected] (C. Perrier), [email protected] (J. Schmidt).
Assessment of intra-abdominal post-traumatic injuries typically relies on contrast-injection abdominal computed tomography (CT) (92.4– 100% sensitivity; 94.4–96.8% specificity), which remains the primary method of assessing hemodynamically-stable blunt-trauma patients with a positive predictive value (PPV) N 98% [4]. A further examination, namely the urine dipstick, is frequently used in emergency services for abdominal trauma cases in order to diagnose hematuria. This simple, quick, and inexpensive examination for detecting the presence of blood in urine from red blood cells (RBC) exhibits a sensitivity of 91–100% [5,6]. One particular study has shown that the presence of gross hematuria suggests intra-abdominal injury, yet this cannot be said for microscopic hematuria associated with abdominal trauma [7]. The diagnostic and prognostic benefits of microscopic hematuria remain a subject of contention in the event of abdominal trauma. Several studies have, in fact, shown that simple microscopic hematuria may be associated with severe urogenital lesions, whilst others refrain from recommending examination via urine dipstick in
http://dx.doi.org/10.1016/j.ajem.2016.12.047 0735-6757/© 2016 Published by Elsevier Inc.
Please cite this article as: Moustafa F, et al, Assessment of urinary dipstick in patients admitted to an emergency department for blunt abdominal trauma, American Journal of Emergency Medicine (2016), http://dx.doi.org/10.1016/j.ajem.2016.12.047
2
F. Moustafa et al. / American Journal of Emergency Medicine xxx (2016) xxx–xxx
abdominal trauma due to the lack of significance of microscopic hematuria [5,6,8]. In light of the paucity of articles regarding the diagnostic benefit of performing dipstick urinalysis in emergency cases following abdominal injury, we conducted this study with the aim of evaluating the diagnostic value of dipstick urinalysis in emergency medicine following abdominal trauma.
2. Patients and methods We performed a retrospective, multicenter, cohort study at the University Hospital of Clermont-Ferrand (Trauma Center, Level one) and the Hospital of Aurillac (Trauma Center, level three) from January 2012 to August 2014. All included patients were over 18 years old, admitted to the emergency department for abdominal trauma, and underwent urinalysis dipstick and contrast-injection abdominal CT. We thereby excluded urine samples collected via catheterization or suprapubic catheters, in order to avoid iatrogenic traumatic hematuria cases, patients with kidney cancer, bladder cancer, or polycystic kidney disease, and patients affected by Berger's disease or those with suspected urinary tract infection through the presence of leukocytes or nitrites on urinalysis. As this study was observational, non-interventional, and retrospective, there was no need to request approval from the ethics committee, nor informed consent from patients. By means of patients' medical records, we collected demographic variables as well as clinical and laboratory data, such as age, gender, background, indication of anticoagulant therapy, injury mechanism (accidents involving light vehicles, two-wheelers, falls or board sports, sustained as a pedestrian, or trauma caused by an object), abdominal pain, abdominal defense or abdominal wall hematoma, signs of hemodynamic shock (defined as systolic blood pressure ≤ 90 mmHg), and anemia (Hb b 10 g/dL). Abdominal CT data was collected from archived radiological reports. Therapeutic management (fluid resuscitation, transfusion, surgery, embolization, hospitalization, etc.) and patient outcome data was also obtained. Microscopic hematuria was defined via the presence of over 5–10 red cells per field or the appearance of at least one cross on the urine dipstick (Clinitek Status® Analyser, Siemens) [9]. Gross hematuria was defined via visible blood in patient urine. The gold standard for determining abdominal injury was the result obtained via contrast-injection abdominal CT.
2.1. Statistical analysis Data was expressed as numbers and percentages for categorical variables, as means and standard deviations or medians and interquartile ranges in terms of the statistical distribution (normality analyzed using the Shapiro-Wilk test) for quantitative variables. Comparison of quantitative variables was performed by means of Student's t-test or Mann-Whitney test. Comparison of qualitative parameters was carried out via the Chi-squared test or, if necessary, Fisher's exact test. Diagnostic results were expressed in terms of sensitivity and specificity, as well as positive and negative predictive values (PPV and NPV) and areas under the curve, in conjunction with their 95% confidence interval (CI). All analyses were conducted through bilateral formulation for an error significance level of 5% using the Stata software (Version 13, StataCorp, College Station, US). 3. Results From January 2012 to August 2014, abdominal CTs and urine dipstick analysis were performed for 123 patients suffering from abdominal trauma (Fig. 1). Overall, 100 patients were included in our study, comprising 33 women and 67 men, with a mean age of 46.3 ± 21.8 years old (Table 1). In total, 36 had experienced abdominal injury, 19 (52.7%) involving cases of kidney or urinary tract damage, four (11.1%) splenic lesions, seven (19.4%) liver lesions, seven (19.4%) pelvic fractures, 24 (66.7%) intra-abdominal hematomas, and two (5.5%) lesions of the renal pedicle. Two out of every three traumas were accounted for by car accidents or falls. The clinical examination revealed 69 patients affected by abdominal pain. For patients exhibiting abdominal injury compared to those without, abdominal defense was over 3-fold higher (odds ratio [OR]: 5.2; 95% CI: 1.8–14.5), abdominal wall hematoma over 2-fold higher (OR: 3.1; 95% CI: 1.2–7.9), and hemodynamic shock over 5-fold higher (OR: 8.4; 95% CI: 2.7–26). Moreover, one in every three patients with abdominal injury presented with anemia on the initial blood test (OR: 3.6; 95% CI: 1.2–10.3). For the 56 patients with microscopic hematuria, the presence of three crosses on the dipstick was 3-fold higher for patients with abdominal injury than those without (OR: 4.8; 95% CI: 1.9–11.9). The incidence of gross hematuria was 6-fold higher in patients with abdominal injury than those without (OR: 8.5; 95% CI: 2.5–28.7).
Fig. 1. Flowchart.
Please cite this article as: Moustafa F, et al, Assessment of urinary dipstick in patients admitted to an emergency department for blunt abdominal trauma, American Journal of Emergency Medicine (2016), http://dx.doi.org/10.1016/j.ajem.2016.12.047
F. Moustafa et al. / American Journal of Emergency Medicine xxx (2016) xxx–xxx
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Table 1 Comparison of patient characteristics according to the presence or absence of abdominal lesions detected via CT scan.
Sex Female, n (%) Male, n (%) Age, mean ± sd Age N 50 years old, n (%) Antithrombotic agent Type of trauma Car accident, n (%) Two-wheeler accident, n (%) Blunt object, n (%) Fall, n (%) Accident as pedestrian, n (%) Winter sports, n (%) Clinical examination Abdominal pain, n (%) Abdominal defense, n (%) Abdominal wall hematoma, n (%) Shock, n (%) Anemia Microscopic hematuria (Blood in dipstick) 0 cross, n (%) 1 cross, n (%) 2 crosses, n (%) 3 crosses, n (%) Gross hematuria, n (%) Hospitalization, n (%)
Total N = 100
Abdominal injury detected via CT scan N = 36
No abdominal injury detected via CT scan N = 64
P-value
33 67 46.3 ± 21.8 42 17
9 (25%) 27 (75%) 48.47 ± 3.64 15 (41.6%) 8 (22.2%)
24 (37.5%) 40 (62.5%) 45.15 ± 2.74 27 (42.2%) 9 (14.1%)
30 11 15 37 2 5
7 (19.4%) 5 (13.8%) 6 (16.7%) 13 (36.1%) 1 (2.8%) 4 (11.1%)
23 (35.9%) 6 (9.4%) 9 (14.1%) 24 (37.5%) 1 (1.6%) 1 (1.6%)
69 21 23 20 18
29 (80.5%) 14 (38.9%) 13 (36.1%) 15 (41.6%) 11 (30.5%)
40 (62.5%) 7 (10.9%) 10 (15.6%) 5 (7.8%) 7 (1.6%)
0.061 0.001 0.019 b0.001 0.014
44 10 15 31 17 59
10 (27.7%) 0 7 (19.4%) 19 (52.8%) 13 (36.1%) 33 (91.6%)
34 (53.1%) 10 (15.6%) 8 (12.5%) 12 (18.7%) 4 (6.2%) 26 (40.6%)
0.35 – 0.52 0.001 b0.001 b0.001
0.20
0.47 0.96 0.30 0.22
The significant p-value are in bold.
The sensitivity and specificity for microscopic hematuria were 72.2% (95% CI: 54.8–85.8) and 53.1% (95% CI: 40.2–65.7), respectively (Table 2). PPV was 46.4% (95% CI: 33–60.3) and NPV was 77.3% (95% CI: 62.2–88.5). The sensitivity and specificity for gross hematuria were approximately 36.1% (95% CI: 20.8–53.8) and 93.8% (95% CI: 84.8–98.3), respectively, with a PPV of 76.5% (95% CI: 50.1–93.2) and NPV of 72.3% (95% CI: 61.4–81.6). 4. Discussion Our study demonstrated that dipstick urinalysis should not be preferred over clinical sign assessment to establish a diagnosis of abdominal injury. We found that clinical signs, such as hypovolemic shock, abdominal wall hematoma, abdominal defense or anemia, were significantly more predictive for detecting abdominal injuries, whereas microscopic hematuria was found neither adequately specific nor sensitive. First, our study revealed that clinical signs were superior for helping detect blunt abdominal trauma. The likelihood of CT scan revealing abdominal injury was greater if the patients presented with hemodynamic shock, abdominal defense, wall hematoma or anemia, as reflected by other studies [10,11]. In order to decrease mortality among such patients (36 abdominal injuries, 20% of patients affected by hemodynamic shock in our study), diagnosis must be established, and thus optimal treatment commenced, as early as possible [7,12]. However, even if
hemodynamic instability constitutes grounds for performing CT scan irrespective of hematuria severity [8,10,13,14], such patients should promptly be referred to the operating room to be managed by the trauma surgery team. Secondly, this negative result for urinalysis may be partly accounted for by the fact that in all emergency departments, the proportion of microscopic hematuria may reach a false positive rate of 13%, even after excluding those patients admitted in a trauma context [11]. These results were consistent with those of other studies that demonstrated that no patients with microscopic hematuria who had not undergone CT scans experienced clinical consequences. Urinalysis has even proven to offer low diagnostic value in the prediction of traumatic intra-abdominal injuries by blunt objects in children [7,8]. The studies on urinalysis in abdominal traumas have, however, produced contradictory findings. One particular study did not find a single parenchymal laceration in the absence of hematuria in a population of 1038 subjects with suspected renal injury. Furthermore, out of 100 negative urine strip results, no secondary lesion was found, proving that urinalysis is a safe tool with a zero morbidity rate [15]. That said, other studies have demonstrated that the absence of hematuria may provide false reassurance, especially in the event of renal pedicle lesions associated with kidney trauma, which may account for 15–30% or 24–40% of cases of pedicle violations and 31–55% of ureteral avulsions [6,16]. Such vascular lesions were primarily related to sudden deceleration, commonly associated with snow
Table 2 Performance characteristics of urinalysis for detecting intra-abdominal injury following blunt traumas.
Microscopic hematuria Equal or N1 cross Equal or N2 crosses Equal or N3 crosses Gross hematuria
Sensitivity [95%CI]
Specificity [95%CI]
PPV [95%CI]
NPV [95%CI]
AUC [95%CI]
72.2% [54.8–85.8%] 72.2% [54.8–85.8%] 52.8% [35.5–69.6%] 36.1% [20.8–53.8%]
53.1 [40.2–65.7%] 68.8% [55.9–79.8%] 81.3% [69.5–89.9%] 93.8% [84.8–98.3%]
46.4% [33–60.3%] 56.5% [41.1–71.1%] 61.3% [42.2–78.2%] 76.5% [50.1–93.2%]
77.3% [62.2–88.5%] 81.5% [68.6–90.7%] 75.4% [63.5–84.9%] 72.3% [61.4–81.6%]
0.627 [0.53–0.723] 0.705 [0.611–0.799] 0.67 [0.574–0.766] 0.649 [0.564–0.734]
Microscopic hematuria was defined by the appearance of at least one cross on the urine dipstick. PPV = Positive predictive value; NPV = Negative predictive value; CI = Confidence interval; AUC = Area under curve.
Please cite this article as: Moustafa F, et al, Assessment of urinary dipstick in patients admitted to an emergency department for blunt abdominal trauma, American Journal of Emergency Medicine (2016), http://dx.doi.org/10.1016/j.ajem.2016.12.047
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F. Moustafa et al. / American Journal of Emergency Medicine xxx (2016) xxx–xxx
sports [17]. Authors found that particular attention must be paid in the event of gross hematuria, which displays a high specificity of 93.8% for abdominal trauma. Therefore, the presence of gross hematuria should be grounds for performing a CT scan, or at least admitting the patient for observation, with several studies involving adults and children expressing a consensus on this point [1,17-19]. Finally, systematic imaging no longer appears justified for abdominal blunt trauma presenting with microscopic hematuria and stable hemodynamics [1,8,10,14,20]. Given its retrospective nature, our study displays certain limitations. Our figures representing the incidence of gross hematuria are probably underestimated due to that fact that its presence was recorded solely when it was indicated in patient folders; we excluded patients on urine catheters, and the most severe patients were referred directly to the ICU or operating room. In terms of determining severity, urine dipstick examination showed little benefit for the clinician in their diagnostic approach. It would prove useful to now carry out prospective studies with larger populations in order to avoid confounding bias and facilitate the creation of an accurate risk score with the aim of predicting the occurrence of abdominal injury in traumas and detecting patients at risk in order to manage them as rapidly as possible. In summary, we have demonstrated that the key component to discovering whether an intra-abdominal injury has occurred after a blunt abdominal trauma is assessment of hypovolemic shock, abdominal defense, abdominal wall hematoma or anemia, whereas dipstick urinalysis should only be considered as an additional diagnostic tool due to its low sensitivity and specificity. Conflict of interest None of the study authors declared a conflict of interest. Acknowledgments All authors had full access to all study data (including statistical reports and tables) and bear responsibility for data integrity, as well as the accuracy of the data analysis. All authors were involved in the critical revision of the manuscript with regard to its primary intellectual content, and all approved the final version submitted for publication.
References [1] Miniño AM, Heron MP, Murphy SL, et al. Deaths: final data for 2004. Natl Vital Stat Rep 2007;55:1–119. [2] Poletti PA, Mirvis SE, Shanmuganathan K, et al. Blunt abdominal trauma patients: can organ injury be excluded without performing computed tomography? J Trauma 2004;57:1072–81. [3] Schurink GWH, Bode PJ, van Luijt PA, et al. The value of physical examination in the diagnosis of patients with blunt abdominal trauma: a retrospective study. Injury 1997;28:261–5. [4] Peytel E, Menegaux F, Cluzel P, et al. Initial imaging assessment of severe blunt trauma. Intensive Care Med 2001;27:1756–61. [5] Karamercan MA, Sevgili AM, Karamercan A, et al. Microscopic hematuria as a marker of blunt abdominal trauma in rats: description of an experimental model. J Trauma 2011;71:687–93. [6] Knudson MM, McAninch JW, Gomez R, et al. Hematuria as a predictor of abdominal injury after blunt trauma. Am J Surg 1992;164 [482-5-6]. [7] Sabzghabaei A, Shojaee M, Safari S, et al. The accuracy of urinalysis in predicting intra-abdominal injury following blunt traumas. Emerge (Tehran, Iran) 2016;4: 11–5. [8] Olthof DC, Joosse P, van der Vlies CH, et al. Routine urinalysis in patients with a blunt abdominal trauma mechanism is not valuable to detect urogenital injury. Emerg Med J 2015;32:119–23. [9] Wollin T, Laroche B, Psooy K. Canadian guidelines for the management of asymptomatic microscopic hematuria in adults. Can Urol Assoc J 2009;3:77–80. [10] Mani NBS, Kim L. The role of interventional radiology in urologic tract trauma. Semin Interv Radiol 2011;28:415–23. [11] Mohr DN, Offord KP, Owen RA, et al. Asymptomatic microhematuria and urologic disease. A population-based study. JAMA 1986;256:224–9. [12] Alavi-Moghaddam M, Safari S, Najafi I, et al. Accuracy of urine dipstick in the detection of patients at risk for crush-induced rhabdomyolysis and acute kidney injury. Eur J Emerg Med 2012;19:329–32. [13] Raz O, Haifler M, Copel L, et al. Use of adult criteria for slice imaging may limit unnecessary radiation exposure in children presenting with hematuria and blunt abdominal trauma. Urology 2011;77:187–90. [14] Nishijima DK, Simel DL, Wisner DH, et al. Does this adult patient have a blunt intraabdominal injury? JAMA 2012;307:1517–27. [15] Kennedy TJ, McConnell JD, Thal ER. Urine dipstick vs. microscopic urinalysis in the evaluation of abdominal trauma. J Trauma 1988;28:615–7. [16] Cass AS. Renovascular injuries from external trauma. Diagnosis, treatment, and outcome. Urol Clin North Am 1989;16:213–20. [17] Lloyd GL, Slack S, McWilliams KL, et al. Renal trauma from recreational accidents manifests different injury patterns than urban renal trauma. J Urol 2012;188:163–8. [18] Dawson C, Whitfield H. ABC of urology. Urological trauma and bladder reconstruction. BMJ 1996;312:1352–4. [19] Holmes JF, Wisner DH, McGahan JP, et al. Clinical prediction rules for identifying adults at very low risk for intra-abdominal injuries after blunt trauma. Ann Emerg Med 2009;54:575–84. [20] Lynch TH, Martínez-Piñeiro L, Plas E, et al. EAU guidelines on urological trauma. Eur Urol 2005;47:1–15.
Please cite this article as: Moustafa F, et al, Assessment of urinary dipstick in patients admitted to an emergency department for blunt abdominal trauma, American Journal of Emergency Medicine (2016), http://dx.doi.org/10.1016/j.ajem.2016.12.047
Contents lists available at ScienceDirect
American Journal of Emergency Medicine journal homepage: www.elsevier.com/locate/ajem
Assessment of urinary dipstick in patients admitted to an emergency department for blunt abdominal trauma F. Moustafa a,⁎, C. Loze a, B. Pereira b, MA. Vaz c, L. Caumon d, C. Perrier a, J. Schmidt a,e a
Service des urgences, Pôle SAMU-SMUR-Urgences, CHU Gabriel Montpied, Clermont-Ferrand, France Direction de la Recherche Clinique et de l'Innovation, Département de Biostatistiques, CHU Gabriel Montpied, Clermont-Ferrand, France Service de radiologie, CHU Gabriel Montpied, Clermont-Ferrand, France d Service des urgences, CH Aurillac, Aurillac, France e Université d'Auvergne, Clermont-I, UFR de médecine, Clermont-Ferrand, France b c
a r t i c l e
i n f o
Article history: Received 19 October 2016 Received in revised form 16 December 2016 Accepted 16 December 2016 Available online xxxx Keywords: Blunt abdominal trauma Urinalysis Hematuria Emergency
a b s t r a c t Introduction: Clinicians still face significant challenge in predicting intra-abdominal injuries in patients admitted to an emergency department for blunt abdominal trauma. This study was thus designed to investigate the value of dipstick urinalysis in patients with blunt abdominal trauma. Methods: We performed a retrospective, multicenter, cohort study involving patients admitted to the emergency department for abdominal traumas, examined by means of urinary dipstick and abdominal CT scan. The primary endpoint was the correlation between microscopic hematuria detected via dipstick urinalysis (defined by the presence of blood on the dipstick urinalysis but without gross hematuria) and abdominal injury, as evidenced on CT scan. Results: Of the 100 included patients, 56 experienced microscopic hematuria, 17 gross hematuria, and 44 no hematuria. Patients with abdominal injury were more likely to present with hypovolemic shock (odds ratio [OR]: 8.4; 95% confidence interval [CI]: 2.7–26), abdominal wall hematoma (OR: 3.1; 95% CI: 1.2–7.9), abdominal defense (OR: 5.2; 95% CI: 1.8–14.5), or anemia (OR: 3.6; 95% CI: 1.2–10.3). Moreover, dipstick urinalysis was less likely to predict injury, with just 72.2% sensitivity (95% CI: 54.8–85.8), 53.1% specificity (95% CI: 40.2–65.7), and positive and negative predictive values of 46.4% (95% CI: 33.0–60.3) and 77.3% (95% CI: 62.2–88.5), respectively. Conclusion: Dipstick urinalysis was neither adequately specific nor sensitive for predicting abdominal injury and should thus not be used as a key assessment component in patients suffering from blunt abdominal trauma, with physical exam and vital sign assessment the preferred choice. © 2016 Published by Elsevier Inc.
1. Introduction Abdominal injuries account for 15–20% of trauma-related lesions and constitute a leading cause of mortality in 10–30% of patients exhibiting such lesions [1]. They primarily constitute lesions caused by contusion in solid organs (spleen, liver, kidneys, or pancreas) or perforation of hollow organs (duodenum, small intestine, or colon). Whilst clinical diagnosis can be straightforward, with indicators such as pain or abdominal defense, clinical abdominal examination cannot be used to diagnose all patients with intra-abdominal injuries [2,3]. ⁎ Corresponding author at: Service des urgences, Hôpital Gabriel Montpied, 58 rue Montalembert, F-63003 Clermont-Ferrand Cedex 1, France. E-mail addresses: [email protected] (F. Moustafa), [email protected] (C. Loze), [email protected] (B. Pereira), [email protected] (M.A. Vaz), [email protected] (L. Caumon), [email protected] (C. Perrier), [email protected] (J. Schmidt).
Assessment of intra-abdominal post-traumatic injuries typically relies on contrast-injection abdominal computed tomography (CT) (92.4– 100% sensitivity; 94.4–96.8% specificity), which remains the primary method of assessing hemodynamically-stable blunt-trauma patients with a positive predictive value (PPV) N 98% [4]. A further examination, namely the urine dipstick, is frequently used in emergency services for abdominal trauma cases in order to diagnose hematuria. This simple, quick, and inexpensive examination for detecting the presence of blood in urine from red blood cells (RBC) exhibits a sensitivity of 91–100% [5,6]. One particular study has shown that the presence of gross hematuria suggests intra-abdominal injury, yet this cannot be said for microscopic hematuria associated with abdominal trauma [7]. The diagnostic and prognostic benefits of microscopic hematuria remain a subject of contention in the event of abdominal trauma. Several studies have, in fact, shown that simple microscopic hematuria may be associated with severe urogenital lesions, whilst others refrain from recommending examination via urine dipstick in
http://dx.doi.org/10.1016/j.ajem.2016.12.047 0735-6757/© 2016 Published by Elsevier Inc.
Please cite this article as: Moustafa F, et al, Assessment of urinary dipstick in patients admitted to an emergency department for blunt abdominal trauma, American Journal of Emergency Medicine (2016), http://dx.doi.org/10.1016/j.ajem.2016.12.047
2
F. Moustafa et al. / American Journal of Emergency Medicine xxx (2016) xxx–xxx
abdominal trauma due to the lack of significance of microscopic hematuria [5,6,8]. In light of the paucity of articles regarding the diagnostic benefit of performing dipstick urinalysis in emergency cases following abdominal injury, we conducted this study with the aim of evaluating the diagnostic value of dipstick urinalysis in emergency medicine following abdominal trauma.
2. Patients and methods We performed a retrospective, multicenter, cohort study at the University Hospital of Clermont-Ferrand (Trauma Center, Level one) and the Hospital of Aurillac (Trauma Center, level three) from January 2012 to August 2014. All included patients were over 18 years old, admitted to the emergency department for abdominal trauma, and underwent urinalysis dipstick and contrast-injection abdominal CT. We thereby excluded urine samples collected via catheterization or suprapubic catheters, in order to avoid iatrogenic traumatic hematuria cases, patients with kidney cancer, bladder cancer, or polycystic kidney disease, and patients affected by Berger's disease or those with suspected urinary tract infection through the presence of leukocytes or nitrites on urinalysis. As this study was observational, non-interventional, and retrospective, there was no need to request approval from the ethics committee, nor informed consent from patients. By means of patients' medical records, we collected demographic variables as well as clinical and laboratory data, such as age, gender, background, indication of anticoagulant therapy, injury mechanism (accidents involving light vehicles, two-wheelers, falls or board sports, sustained as a pedestrian, or trauma caused by an object), abdominal pain, abdominal defense or abdominal wall hematoma, signs of hemodynamic shock (defined as systolic blood pressure ≤ 90 mmHg), and anemia (Hb b 10 g/dL). Abdominal CT data was collected from archived radiological reports. Therapeutic management (fluid resuscitation, transfusion, surgery, embolization, hospitalization, etc.) and patient outcome data was also obtained. Microscopic hematuria was defined via the presence of over 5–10 red cells per field or the appearance of at least one cross on the urine dipstick (Clinitek Status® Analyser, Siemens) [9]. Gross hematuria was defined via visible blood in patient urine. The gold standard for determining abdominal injury was the result obtained via contrast-injection abdominal CT.
2.1. Statistical analysis Data was expressed as numbers and percentages for categorical variables, as means and standard deviations or medians and interquartile ranges in terms of the statistical distribution (normality analyzed using the Shapiro-Wilk test) for quantitative variables. Comparison of quantitative variables was performed by means of Student's t-test or Mann-Whitney test. Comparison of qualitative parameters was carried out via the Chi-squared test or, if necessary, Fisher's exact test. Diagnostic results were expressed in terms of sensitivity and specificity, as well as positive and negative predictive values (PPV and NPV) and areas under the curve, in conjunction with their 95% confidence interval (CI). All analyses were conducted through bilateral formulation for an error significance level of 5% using the Stata software (Version 13, StataCorp, College Station, US). 3. Results From January 2012 to August 2014, abdominal CTs and urine dipstick analysis were performed for 123 patients suffering from abdominal trauma (Fig. 1). Overall, 100 patients were included in our study, comprising 33 women and 67 men, with a mean age of 46.3 ± 21.8 years old (Table 1). In total, 36 had experienced abdominal injury, 19 (52.7%) involving cases of kidney or urinary tract damage, four (11.1%) splenic lesions, seven (19.4%) liver lesions, seven (19.4%) pelvic fractures, 24 (66.7%) intra-abdominal hematomas, and two (5.5%) lesions of the renal pedicle. Two out of every three traumas were accounted for by car accidents or falls. The clinical examination revealed 69 patients affected by abdominal pain. For patients exhibiting abdominal injury compared to those without, abdominal defense was over 3-fold higher (odds ratio [OR]: 5.2; 95% CI: 1.8–14.5), abdominal wall hematoma over 2-fold higher (OR: 3.1; 95% CI: 1.2–7.9), and hemodynamic shock over 5-fold higher (OR: 8.4; 95% CI: 2.7–26). Moreover, one in every three patients with abdominal injury presented with anemia on the initial blood test (OR: 3.6; 95% CI: 1.2–10.3). For the 56 patients with microscopic hematuria, the presence of three crosses on the dipstick was 3-fold higher for patients with abdominal injury than those without (OR: 4.8; 95% CI: 1.9–11.9). The incidence of gross hematuria was 6-fold higher in patients with abdominal injury than those without (OR: 8.5; 95% CI: 2.5–28.7).
Fig. 1. Flowchart.
Please cite this article as: Moustafa F, et al, Assessment of urinary dipstick in patients admitted to an emergency department for blunt abdominal trauma, American Journal of Emergency Medicine (2016), http://dx.doi.org/10.1016/j.ajem.2016.12.047
F. Moustafa et al. / American Journal of Emergency Medicine xxx (2016) xxx–xxx
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Table 1 Comparison of patient characteristics according to the presence or absence of abdominal lesions detected via CT scan.
Sex Female, n (%) Male, n (%) Age, mean ± sd Age N 50 years old, n (%) Antithrombotic agent Type of trauma Car accident, n (%) Two-wheeler accident, n (%) Blunt object, n (%) Fall, n (%) Accident as pedestrian, n (%) Winter sports, n (%) Clinical examination Abdominal pain, n (%) Abdominal defense, n (%) Abdominal wall hematoma, n (%) Shock, n (%) Anemia Microscopic hematuria (Blood in dipstick) 0 cross, n (%) 1 cross, n (%) 2 crosses, n (%) 3 crosses, n (%) Gross hematuria, n (%) Hospitalization, n (%)
Total N = 100
Abdominal injury detected via CT scan N = 36
No abdominal injury detected via CT scan N = 64
P-value
33 67 46.3 ± 21.8 42 17
9 (25%) 27 (75%) 48.47 ± 3.64 15 (41.6%) 8 (22.2%)
24 (37.5%) 40 (62.5%) 45.15 ± 2.74 27 (42.2%) 9 (14.1%)
30 11 15 37 2 5
7 (19.4%) 5 (13.8%) 6 (16.7%) 13 (36.1%) 1 (2.8%) 4 (11.1%)
23 (35.9%) 6 (9.4%) 9 (14.1%) 24 (37.5%) 1 (1.6%) 1 (1.6%)
69 21 23 20 18
29 (80.5%) 14 (38.9%) 13 (36.1%) 15 (41.6%) 11 (30.5%)
40 (62.5%) 7 (10.9%) 10 (15.6%) 5 (7.8%) 7 (1.6%)
0.061 0.001 0.019 b0.001 0.014
44 10 15 31 17 59
10 (27.7%) 0 7 (19.4%) 19 (52.8%) 13 (36.1%) 33 (91.6%)
34 (53.1%) 10 (15.6%) 8 (12.5%) 12 (18.7%) 4 (6.2%) 26 (40.6%)
0.35 – 0.52 0.001 b0.001 b0.001
0.20
0.47 0.96 0.30 0.22
The significant p-value are in bold.
The sensitivity and specificity for microscopic hematuria were 72.2% (95% CI: 54.8–85.8) and 53.1% (95% CI: 40.2–65.7), respectively (Table 2). PPV was 46.4% (95% CI: 33–60.3) and NPV was 77.3% (95% CI: 62.2–88.5). The sensitivity and specificity for gross hematuria were approximately 36.1% (95% CI: 20.8–53.8) and 93.8% (95% CI: 84.8–98.3), respectively, with a PPV of 76.5% (95% CI: 50.1–93.2) and NPV of 72.3% (95% CI: 61.4–81.6). 4. Discussion Our study demonstrated that dipstick urinalysis should not be preferred over clinical sign assessment to establish a diagnosis of abdominal injury. We found that clinical signs, such as hypovolemic shock, abdominal wall hematoma, abdominal defense or anemia, were significantly more predictive for detecting abdominal injuries, whereas microscopic hematuria was found neither adequately specific nor sensitive. First, our study revealed that clinical signs were superior for helping detect blunt abdominal trauma. The likelihood of CT scan revealing abdominal injury was greater if the patients presented with hemodynamic shock, abdominal defense, wall hematoma or anemia, as reflected by other studies [10,11]. In order to decrease mortality among such patients (36 abdominal injuries, 20% of patients affected by hemodynamic shock in our study), diagnosis must be established, and thus optimal treatment commenced, as early as possible [7,12]. However, even if
hemodynamic instability constitutes grounds for performing CT scan irrespective of hematuria severity [8,10,13,14], such patients should promptly be referred to the operating room to be managed by the trauma surgery team. Secondly, this negative result for urinalysis may be partly accounted for by the fact that in all emergency departments, the proportion of microscopic hematuria may reach a false positive rate of 13%, even after excluding those patients admitted in a trauma context [11]. These results were consistent with those of other studies that demonstrated that no patients with microscopic hematuria who had not undergone CT scans experienced clinical consequences. Urinalysis has even proven to offer low diagnostic value in the prediction of traumatic intra-abdominal injuries by blunt objects in children [7,8]. The studies on urinalysis in abdominal traumas have, however, produced contradictory findings. One particular study did not find a single parenchymal laceration in the absence of hematuria in a population of 1038 subjects with suspected renal injury. Furthermore, out of 100 negative urine strip results, no secondary lesion was found, proving that urinalysis is a safe tool with a zero morbidity rate [15]. That said, other studies have demonstrated that the absence of hematuria may provide false reassurance, especially in the event of renal pedicle lesions associated with kidney trauma, which may account for 15–30% or 24–40% of cases of pedicle violations and 31–55% of ureteral avulsions [6,16]. Such vascular lesions were primarily related to sudden deceleration, commonly associated with snow
Table 2 Performance characteristics of urinalysis for detecting intra-abdominal injury following blunt traumas.
Microscopic hematuria Equal or N1 cross Equal or N2 crosses Equal or N3 crosses Gross hematuria
Sensitivity [95%CI]
Specificity [95%CI]
PPV [95%CI]
NPV [95%CI]
AUC [95%CI]
72.2% [54.8–85.8%] 72.2% [54.8–85.8%] 52.8% [35.5–69.6%] 36.1% [20.8–53.8%]
53.1 [40.2–65.7%] 68.8% [55.9–79.8%] 81.3% [69.5–89.9%] 93.8% [84.8–98.3%]
46.4% [33–60.3%] 56.5% [41.1–71.1%] 61.3% [42.2–78.2%] 76.5% [50.1–93.2%]
77.3% [62.2–88.5%] 81.5% [68.6–90.7%] 75.4% [63.5–84.9%] 72.3% [61.4–81.6%]
0.627 [0.53–0.723] 0.705 [0.611–0.799] 0.67 [0.574–0.766] 0.649 [0.564–0.734]
Microscopic hematuria was defined by the appearance of at least one cross on the urine dipstick. PPV = Positive predictive value; NPV = Negative predictive value; CI = Confidence interval; AUC = Area under curve.
Please cite this article as: Moustafa F, et al, Assessment of urinary dipstick in patients admitted to an emergency department for blunt abdominal trauma, American Journal of Emergency Medicine (2016), http://dx.doi.org/10.1016/j.ajem.2016.12.047
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F. Moustafa et al. / American Journal of Emergency Medicine xxx (2016) xxx–xxx
sports [17]. Authors found that particular attention must be paid in the event of gross hematuria, which displays a high specificity of 93.8% for abdominal trauma. Therefore, the presence of gross hematuria should be grounds for performing a CT scan, or at least admitting the patient for observation, with several studies involving adults and children expressing a consensus on this point [1,17-19]. Finally, systematic imaging no longer appears justified for abdominal blunt trauma presenting with microscopic hematuria and stable hemodynamics [1,8,10,14,20]. Given its retrospective nature, our study displays certain limitations. Our figures representing the incidence of gross hematuria are probably underestimated due to that fact that its presence was recorded solely when it was indicated in patient folders; we excluded patients on urine catheters, and the most severe patients were referred directly to the ICU or operating room. In terms of determining severity, urine dipstick examination showed little benefit for the clinician in their diagnostic approach. It would prove useful to now carry out prospective studies with larger populations in order to avoid confounding bias and facilitate the creation of an accurate risk score with the aim of predicting the occurrence of abdominal injury in traumas and detecting patients at risk in order to manage them as rapidly as possible. In summary, we have demonstrated that the key component to discovering whether an intra-abdominal injury has occurred after a blunt abdominal trauma is assessment of hypovolemic shock, abdominal defense, abdominal wall hematoma or anemia, whereas dipstick urinalysis should only be considered as an additional diagnostic tool due to its low sensitivity and specificity. Conflict of interest None of the study authors declared a conflict of interest. Acknowledgments All authors had full access to all study data (including statistical reports and tables) and bear responsibility for data integrity, as well as the accuracy of the data analysis. All authors were involved in the critical revision of the manuscript with regard to its primary intellectual content, and all approved the final version submitted for publication.
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Please cite this article as: Moustafa F, et al, Assessment of urinary dipstick in patients admitted to an emergency department for blunt abdominal trauma, American Journal of Emergency Medicine (2016), http://dx.doi.org/10.1016/j.ajem.2016.12.047