Clinical Outcomes of Pediatric Patients With Acute Abdominal Pain and Incidental Findings of Free Intraperitoneal Fluid on Diagnostic Imaging

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1 ORIGINAL RESEARCH Clinical Outcomes of Pediatric Patients With Acute Abdominal Pain and Incidental Findings of Free Intraperitoneal Fluid on Diagnostic Imaging Samantha Matz, DO, Mary Connell, MD, Madhumita Sinha, MD, Christopher S. Goettl, MD, Palak C. Patel, MD, David Drachman, PhD Article includes CME test Received November 20, 2012, from the Departments of Radiology (S.M., M.C.) and Research (D.D.), Maricopa Medical Center, Phoenix, Arizona USA; Department of Pediatric Emergency Medicine, Arizona Children s Center at Maricopa Medical Center, Phoenix, Arizona USA (M.S.); and University of Arizona College of Medicine, Tucson, Arizona USA (C.S.G., P.C.P.). Revision requested December 7, Revised manuscript accepted for publication January 22, This study was presented as a podium presentation at the 112th Annual Meeting of the American Roentgen Ray Society; May 2012; Vancouver, British Columbia, Canada. Address correspondence to Madhumita Sinha, MD, Department of Pediatrics, Maricopa Integrated Health System, 2601 E Roosevelt St, Phoenix, AZ USA. madhumita_sinha@dmgaz.org Abbreviations CT, computed tomography; ED, emergency department doi: /ultra Objectives The presence of free intraperitoneal fluid on diagnostic imaging (sonography or computed tomography [CT]) may indicate an acute inflammatory process in children with abdominal pain in a nontraumatic setting. Although clinical outcomes of pediatric trauma patients with free fluid on diagnostic examinations without evidence of solid-organ injury have been studied, similar studies in the absence of trauma are rare. Our objective was to study clinical outcomes of children with acute abdominal pain of nontraumatic etiology and free intraperitoneal fluid on diagnostic imaging (abdominal/pelvic sonography, CT, or both). Methods We conducted a retrospective review of medical records of children aged 0 to 18 years presenting to a pediatric emergency department with acute abdominal pain (nontraumatic) between April 2008 and March Patients with intraperitoneal free fluid on imaging were divided into 2 groups: group I, imaging suggestive of an intraabdominal surgical condition such as appendicitis; and group II, no evidence of an acute surgical condition on imaging, including patients with equivocal studies. Computed tomograms and sonograms were reviewed by a board-certified radiologist, and the free fluid volume was quantitated. Results Of 1613 patients who underwent diagnostic imaging, 407 were eligible for the study; 134 (33%) had free fluid detected on diagnostic imaging. In patients with both sonography and CT, there was a significant correlation in the free fluid volume (r = 0.79; P <.0005). A significantly greater number of male patients with free fluid had a surgical condition identified on imaging (57.4% versus 25%; P <.001). Children with free fluid and an associated condition on imaging were more likely to have surgery (94.4% versus 6.3%; P <.001). Conclusions We found clinical outcomes (surgical versus nonsurgical) to be most correlated with a surgical diagnosis on diagnostic imaging and not with the amount of fluid present. Key Words abdomen; children; free fluid; imaging; pain The presence of free intraperitoneal fluid may be a cardinal sign of an acute inflammatory process in a patient with abdominal pain in a nontraumatic setting. Small amounts of free fluid have been found on diagnostic imaging and are considered physiologic in asymptomatic children. 1,2 Although a finding of free intraperitoneal fluid among children with blunt abdominal 2013 by the American Institute of Ultrasound in Medicine J Ultrasound Med 2013; 32:

2 trauma may signal an associated solid or hollow viscous injury, recent studies have suggested that isolated free intraperitoneal fluid detected on diagnostic imaging in pediatric trauma patients, with no associated findings of solid-organ injury, a normal mental status, and lack of abdominal tenderness, may be managed conservatively without surgery. 3 5 Our review of published literature yielded few studies addressing the same issue in children with acute abdominal pain of nontraumatic etiology who have incidental findings of free fluid without an associated surgical condition. 6 Our objective was to study clinical outcomes of children with acute abdominal pain (nontraumatic etiology) and isolated findings of free intraperitoneal fluid on diagnostic imaging (abdominal/pelvic sonography, computed tomography [CT], or both). The primary outcome of the study was the need for surgery; secondary outcomes included emergency department (ED) disposition, complications, and return visits to the ED for the same condition after ED discharge. Materials and Methods Design We conducted a retrospective review of medical records of children aged 0 to 18 years who presented to the pediatric ED of a tertiary care teaching hospital between April 2008 and March 2009 with acute abdominal pain (nontraumatic) and who had diagnostic imaging (sonography, CT, or both) performed. Setting This study was conducted in the pediatric ED of a 449-bed tertiary care teaching hospital. The pediatric ED evaluates approximately 20,000 pediatric patients annually and also serves as a pediatric trauma referral center. The Institutional Review Board of the hospital approved the study. Patients Pediatric patients with acute abdominal pain who underwent diagnostic imaging while in the ED, were identified by Current Procedural Terminology codes. Patients with a history of trauma, patients who had a diagnostic examination for nonacute abdominal pain (>7 days), and patients with other chronic abdominal conditions such as inflammatory bowel disease were excluded from the study. Patients who had free intraperitoneal fluid detected on diagnostic imaging were divided into 2 groups: group I, including children who had positive sonographic or CT findings suggestive of an intra-abdominal surgical condition such as appendicitis; and group II, including children with free intraperitoneal fluid but no evidence of an associated surgical condition on diagnostic imaging and those who had equivocal studies. Free Fluid Volume Estimation and Categorization Formal CT and sonographic reports were reviewed by the study team; in addition, images of patients reported to have free intraperitoneal fluid were reexamined by a boardcertified pediatric radiologist. Free fluid volume was estimated by using the ellipsoid volume formula (4/3 width height length π; Figure 1). 1 Figure 1. Images from a 16-year-old female patient presenting to the ED with acute abdominal pain. The patient was discharged from the ED with a diagnosis of constipation. A, Sagittal oblique long-axis sonogram obtained at presentation to the ED showing a pocket of anechoic free fluid in the pelvis. B, Transverse short-axis pelvic sonogram obtained subsequently. Pockets of free fluid were measured in 3 orthogonal planes, and free fluid volumes were estimated by the ellipsoid volume formula. A B 1548 J Ultrasound Med 2013; 32:

3 Sonographic and CT Scan Techniques Sonography (transabdominal and transvaginal in sexually active female patients) was performed with LOGIQ 9 ultrasound equipment (GE Healthcare, Waukesha, WI) using real-time 4 7-MHz linear and curved probes with color Doppler capabilities. For abdominal scans, a survey of the abdomen was obtained, including transverse, oblique, and longitudinal images of the upper right, lower right, upper left, and lower left quadrants. For pelvic imaging of female patients, the pelvis was surveyed, including transverse, oblique, and longitudinal images of the bilateral adnexal regions and rectouterine pouch. Free fluid volumes were measured in 3 orthogonal planes, calculated according to the ellipsoid volume formula, and expressed in milliliters. A gray scale morphologic evaluation of the fluid collections was performed with attention to echogenicity, septations, and multifocality. According to these parameters, fluid collections were classified as free fluid (complex or simple collections). In patients who had multiple pockets of free fluid, the 3 largest measureable pockets were each measured independently in 3 orthogonal planes, and the total was summed. Computed tomography was performed with a Light- Speed RT 16 CT scanner (GE Healthcare). Patients received a nonionic intravenous contrast agent (Omnipaque 350 [iohexol]; GE Healthcare) in a single parenteral dose of 1.0 ml/kg, administered by a power injector. In addition, some patients also received an oral contrast agent (Gastrografin [diatrizoate meglumine and diatrizoate sodium]; Bracco Diagnostics, Inc, Monroe Township, NJ). For patients 0 to 8 years of age, 100 kv (peak) and Smart ma (automatic exposure control) were used with 2.5-mm-thick slices and a 1.25-mm interval. For patients older than 8 years, 120 kv (peak) and Smart ma were used with 5-mm-thick slices and a 4-mm interval. Helical imaging of the abdomen and pelvis was obtained with sagittal and coronal reformatted images. Similar to the sonographic technique, morphologic evaluation of the fluid collections was performed with attention to density, septations, and multifocality. According to these parameters, fluid collections were classified as free fluid or loculated collections. In patients who had multiple pockets of free fluid, the 3 largest measureable pockets were each measured independently in 3 orthogonal planes, and the total was summed (Figure 2). On the basis of the free intraperitoneal fluid volume estimation for individual patients, it was decided to divide patients into the following categories: small (<15 ml of free fluid detected on sonography or CT), medium (15 50 ml of free fluid detected), and large (>50 ml of free fluid detected). If the amount of free fluid detected was too small to quantify, it was designated trace. Statistical Analysis Statistical analysis was done with SPSS version 19.0 software for Windows (SPSS Inc, Chicago, IL). We used descriptive statistics to describe sample characteristics and t tests and χ 2 tests to compare demographic (age, sex, and race) and clinical characteristics (type of diagnostic examination, surgery done, final diagnosis of appendicitis, disposition from the ED, and complications at follow-up) between the groups. P.05 was considered significant. Subgroup Analysis Since our cohort of interest was the group II patients, who had free fluid detected on diagnostic imaging without associated surgical conditions and their outcomes, further categorization of this group was done to enable a detailed subgroup analysis: subgroup IIa included female patients older than 10 years, and subgroup IIb included all male patients in group II as well as female patients 10 years or younger. Results Overall Results Of the 1613 patients who underwent diagnostic imaging for an abdominal/pelvic condition in the ED over a 1-year period, 407 fulfilled eligibility requirements and were included in the study: 250 (61.4%) had sonography, 210 (51.6%) had CT, and 55 (13.5%) had both. The mean age was 10.6 years (SD, 5.9 years), and 169 (41.5%) were male. Most (79.9%) were Hispanic. In patients with both sonography and CT, there was significant correlation in the free fluid volume (r = 0.79; P <.0005). A total of 134 (33%) patients had free fluid detected on diagnostic imaging. Of those patients who had free fluid on diagnostic examinations (sonography, CT, or both), 54 (40.3%) were assigned to group I with a definitive surgical condition identified on imaging. Comparisons of demographic characteristics and clinical outcomes between groups I and II are illustrated in Table 1. A significantly greater number of male patients with free fluid had a surgical condition identified on the diagnostic examination (57.4% versus 25.0%; P <.001). There was no difference in the mean age or ethnicity/race among patients with free intraperitoneal fluid with and without an associated intra-abdominal surgical condition warranting surgery. Children with free fluid and an associated condition on diagnostic examinations were most likely to have surgery (94.4% versus 6.3%; P <.001). J Ultrasound Med 2013; 32:

4 Figure 2. Images from a 9-year-old male patient presenting to the ED with acute abdominal pain who had findings consistent with acute appendicitis with free fluid on imaging. The patient was transferred to the operating room from the ED and was found to have acute gangrenous appendicitis on pathologic examination. Images represent an irregular fluid collection on CT broken down into 3 separate pockets for the purposes of measurement. The 3 pockets were each measured in 3 orthogonal planes, and the total was summed. A, Anteroposterior and craniocaudal measurements of pocket 1. B, Lateral measurement of pocket 1. C, Anteroposterior and craniocaudal measurements of pocket 2. D, Lateral measurement of pocket 2. E, Anteroposterior and craniocaudal measurements of pocket 3. F, Lateral measurement of pocket 3. A B C D E F 1550 J Ultrasound Med 2013; 32:

5 In group II with free intraperitoneal fluid, 5 patients (6.3%) had equivocal examinations for an intra-abdominal surgical condition, and the clinical outcomes of these patients were analyzed: 2 patients were taken to the operating room from the ED on clinical suspicion and found to have appendicitis intraoperatively; 1 had surgical repair of an incarcerated inguinal hernia; 1 had an intussusception reduction in the operating room; and 1 was admitted for observation and discharged from the inpatient unit with a deferred ovarian cyst aspiration performed as an outpatient procedure. Final discharge diagnoses of the remaining 75 patients in group II who did not undergo surgery are listed in Table 2. Table 1. Comparison of Demographic and Clinical Characteristics Among Patients With Free Intraperitoneal Fluid and the Presence (Group I) or Absence (Group II) of Any Associated Surgical Condition Identified on Diagnostic Imaging Group I Group II Characteristic (n = 54) (n = 80) P Male, n (%) 31 (57.4) 20 (25) <.001 a Mean age ± SD, y ± ± b Ethnicity/race, n (%).16 c Hispanic/Latino 45 (83.2) 59 (73.7) Non-Hispanic white 2 (3.7) 6 (7.5) African American 1 (1.9) 8 (10.0) Asian 0 (0.0) 0 (0.0) Native American 5 (9.3) 6 (7.5) Other 1 (1.9) 1 (1.3) Diagnostic examination, n (%).002 c CT only 30 (55.6) 37 (46.3) Sonography only 13 (24.1) 33 (41.3) Both 11 (20.4) 20 (25) Surgery done, n (%) 51 (94.4) 5 (6.3) <.001 a Final diagnosis of 44 (81.5) 2 (2.5) <.001 a appendicitis, n (%) Disposition from ED, n (%) <.001 c Admitted and went to surgery 18 (33.3) 2 (2.5) later Admitted for inpatient 3 (5.6) 34 (42.5) observation Discharged from ED 0 (0.0) 41 (51.2) Transferred to operating room 33 (61.1) 3 (3.8) from ED Complications at follow-up, n (%) 4 (7.5) 0 (0.0).02 a A significantly greater number of male patients with free fluid had a surgical condition identified on the diagnostic examination. a Continuity-corrected χ 2 test of a 2 2 table. b Independent samples t test. c χ 2 test of a 2 n contingency table, where 2 is the number of groups, and n is the number of categories. Subgroup Analysis Results Fifty-one patients (63.8%) were categorized into subgroup IIa, and 29 (36.2%) were categorized into subgroup IIb (Table 3). Children categorized into subgroup IIb were significantly more likely to have a surgical outcome than those in group IIa (13.8% versus 2.0%; P =.036). Most female patients in subgroup IIa (66.7%), who had free fluid without an associated condition, were discharged from the ED and did not return with complications. Interestingly, 100% of patients in subgroup IIb had a large amount of free fluid on diagnostic CT, compared to 68.4% in subgroup IIa, and this difference approached significance. Of the 15 patients with a large amount of free fluid on CT, 1 had a surgical outcome. Of the 4 patients in group IIb who had surgical outcomes, 2 had large volumes identified on imaging. Discussion To do or not to do a surgical exploration in children with acute abdominal pain and free intraperitoneal fluid in the absence of an associated surgical condition clearly identified on a diagnostic imaging often poses a serious management dilemma for physicians. Although recent studies in pediatric trauma patients have shown that nonsurgical management is safe even in the presence of small amounts of free fluid in children without evidence of an associated solid-organ injury, 7 the same issue in patients without trauma has not been well studied. In this retrospective study, we attempted to look at the outcomes of children with acute abdominal pain who have free fluid on sonography or CT; the primary outcome was the need for sur- Table 2. Final Discharge Diagnoses for Patients in Group II With Free Intraperitoneal Fluid, No Surgical Condition on the Diagnostic Examination, and a Nonsurgical Final Outcome Diagnosis Abdominal pain (unspecified) 28 Mesenteric adenitis 2 Acute gastroenteritis 9 Colitis 3 Constipation 3 Ovarian cyst 12 Pelvic inflammatory disease 6 Urinary tract infection 6 Intussusception (nonsurgical reduction) 1 Nephrolithiasis 2 Spontaneous abortion 1 Dysfunctional uterine bleeding 1 Gastritis 1 Total 75 n J Ultrasound Med 2013; 32:

6 gery. We found that in pediatric patients who presented to the ED with acute abdominal pain (nontraumatic) and in whom free fluid was detected on diagnostic imaging with no associated identifiable surgical condition (eg, appendicitis), the mere presence of fluid and the fluid volume were not predictive of a surgical outcome. However, in patients with free fluid and a concomitant surgical condition identified on imaging, the presence of free fluid was strongly correlated with a surgical outcome. Since our focus was on children with just free fluid and no other gross surgical pathologic findings such as acute appendicitis on radiologic examination, we conducted a detailed subgroup analysis in this cohort based on age and sex. We grouped older female patients separately in our subgroup analysis, as physiologic free fluid related to gynecologic issues is commonly noted on imaging in this age group. Surprisingly, even when outcomes in this group of older female patients were analyzed separately, we found that the quantity of free fluid on imaging in the absence of an associated surgical condition was not significantly related to a surgical outcome. In our subgroup analysis, the only 2 patients who had equivocal sonographic examinations with the presence of free fluid and were found to have acute appendicitis intraoperatively also had clinical examinations that were highly suggestive of acute appendicitis. All patients with free fluid and no associated condition who were discharged from the ED did not return with adverse outcomes. Acute appendicitis is known to be more common in male patients, and this situation was found to be no different in our study. Nearly all of the male patients who went to surgery had proven acute appendicitis on pathologic examination (90.9%). A relatively large prospective study done by Sivit 6 involved 250 children with acute abdominal pain and 50 control participants, and graded compression sonography was done for detailed assessment of the lower abdomen and pelvis. The results of that study were similar to our results and found that the presence of free peritoneal fluid detected by sonography in children with acute abdominal pain was largely a nonspecific finding. To our surprise, while reviewing published literature for our research, we did not find a standard well-accepted method for free fluid volume quantitation and stratification; hence, Table 3. Comparison of Female Patients 10 Years or Older (Subgroup IIa) Versus Female Patients Younger Than 10 Years and All Male Patients (Subgroup IIb) Subgroup IIa Subgroup IIb Outcome (n = 51) (n = 29) P Surgery done, n (%) 1 (2.0) 4 (13.8).036 a ED disposition, n (%).002 b Inpatient admission and surgery later 0 (0.0) 2 (6.9) Inpatient admission for observation only 16 (31.4) 18 (62.1) Discharged from ED 34 (66.7) 7 (24.1) Transferred to operating room from ED 1 (2.0) 2 (6.9) Return to ED after discharge for same condition 0 (0.0) 0 (0.0) Subgroup IIa Subgroup IIb Comparison by Fluid Volume Stratification (CT) (n = 19) (n = 15) P Estimated size of fluid collection on CT, n (%) Trace 0 (0.0) 0 (0.0) Small 3 (15.8) 0 (0.0) Medium 3 (15.8) 0 (0.0) Large 13 (68.4) 15 (100.0).056 b Subgroup IIa Subgroup IIb Comparison by Fluid Volume Stratification (Sonography) (n = 28) (n = 10) P Estimated size of fluid collection on sonography, n (%) Trace 0 (0.0) 1 (10.0) Small 14 (50.0) 2 (20.0) Medium 5 (17.9) 1 (10.0) Large 9 (32.1) 6 (60.0).11 b Most patients in subgroup IIa (66.7%), who had free fluid without an associated condition, were discharged from the ED and did not return with complications. a Continuity-corrected χ 2 test of a 2 2 table. b χ 2 test of a 2 n contingency table, where 2 is the number of groups, and n is the number of categories J Ultrasound Med 2013; 32:

7 we developed our own stratification method based on age and sex. Interestingly, all our patients in subgroup IIb (female patients <10 years and male patients) had a large amount of free fluid on diagnostic CT, compared to 68.4% in subgroup IIa (female patients >10 years), and this difference approached significance. Even though these patients did not have surgical diagnoses suggested on imaging, many did have major nonsurgical conditions such as gastroenteritis and pyelonephritis, as mentioned in Table 2. Secondary outcomes of this study included emergency ED disposition, complications, and return visits to the ED for the same condition after ED discharge. A significant number of older female patients were discharged from the ED (66.7%); the etiology of abdominal pain in these patients was predominantly gynecologic. Of the 78 patients who were discharged without surgery, none returned to the ED within a 2-week period requiring surgery for the same condition or with complications related to delays in treatment. Our study findings indicate that patients presenting with acute abdominal pain without an antecedent history of trauma who have isolated free fluid detected without definitive surgical conditions on imaging are highly unlikely to have surgical outcomes, especially in absence of overt signs of an abdominal condition requiring surgery on clinical examinations. Our study had several limitations. Since it was a retrospective study, images were not reviewed in real time, which may have influenced the volume quantitation done by retrospective review of images, especially for sonographic studies. In addition, the imaging studies were done by different radiology staff members without prestudy standardization and were conducted at a single center. Since the literature in this area is so limited, we anticipate that larger prospective studies involving multiple centers will be needed in the future for further validation of our results. 4. Holmes JF, London KL, Brant WE, Kuppermann N. Isolated intraperitoneal fluid on abdominal computed tomography in children with blunt trauma. Acad Emerg Med 2000; 7: Christiano JG, Tummers M, Kennedy A. Clinical significance of isolated intraperitoneal fluid on computed tomography in pediatric blunt abdominal trauma. J Pediatr Surg 2009; 44: Sivit CJ. Significance of peritoneal fluid identified by ultrasonographic examination in children with acute abdominal pain. J Ultrasound Med 1993; 12: Venkatesh KR, McQuay N Jr. Outcomes of management in stable children with intra-abdominal free fluid without solid organ injury after blunt abdominal injury. Trauma 2007; 62: References 1. Simanovsky N, Hiller N, Lubashevsky N, Rozovsky K. Ultrasonographic evaluation of the free intraperitoneal fluid in asymptomatic children. Pediatr Radiol 2010; 41: Rathaus V, Grunebaum M, Konen O, et al. Minimal pelvic fluid in asymptomatic children: the value of the sonographic finding. J Ultrasound Med 2003; 22: Rodriguez C, Barone JE, Wilbanks TO, Rha CK, Miller K. Isolated free fluid on computed tomographic scan in blunt abdominal trauma: a systematic review of incidence and management. J Trauma 2002; 53: J Ultrasound Med 2013; 32: