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(Radiology. 1999;212:515-518.)
© RSNA, 1999

Pediatric Imaging

Splenic Injury Diagnosed with CT: US Follow-up and Healing Rate in Children and Adolescents1

Kathleen H. Emery, MD, Diane S. Babcock, MD, Andrea S. Borgman, MD and Victor F. Garcia, MD

1 From the Departments of Radiology (K.H.E., D.S.B., A.S.B.) and Pediatric Surgery (V.F.G.), Children's Hospital Medical Center, 3333 Burnet Ave, Cincinnati, OH 45229-3039. From the 1997 RSNA scientific assembly. Received August 12, 1998; revision requested September 25; revision received December 22; accepted February 12, 1999. Address reprint requests to K.H.E.


   Abstract
TOP
 Abstract
Introduction
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 References
 
PURPOSE: To determine if pediatric splenic injury healing observed during ultrasonography (US) is related to the computed tomographic (CT) grade of injury severity, to review any delayed complications, and to formulate a grade-specific timetable for follow-up imaging.

MATERIALS AND METHODS: Sixty-eight children and adolescents with CT-documented blunt splenic injury underwent US at approximate 6-week intervals to document injury healing (normal parenchyma or linear echogenic "scar"). Medical records of those not followed up to complete healing were reviewed.

RESULTS: Forty-eight patients were followed up to complete injury healing: 14 of injury grade 1 (mean, 7 weeks; range, 4–12 weeks), 24 of injury grade 2 (mean, 9.5 weeks; range, 6–17 weeks), and 10 of injury grade 3 (mean, 16 weeks; range, 6–29 weeks). The difference in mean time to healing among all grades was significant (P < .02). Only two cysts were found; one decreased in size over time. No complications occurred in the 68 study patients.

CONCLUSION: The time course to US-documented healing of blunt pediatric splenic injury is related to injury severity. This information can be used to tailor follow-up imaging and provide cost savings.

Index terms: Spleen, CT, 775.12112 • Spleen, injuries, 775.411, 775.43 • Spleen, neoplasms, 775.3121 • Spleen, US, 775.1298


   Introduction
TOP
 Abstract
 Introduction
MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 References
 
In the child with hemodynamically stable blunt injury to the spleen, nonsurgical management has become the standard of care (1–3). However, there is no consensus regarding the length of time to restrict physical activity in these patients. Documentation of injury healing with noninvasive imaging is often the benchmark cited. Several researchers in the literature have examined the use of computed tomography (CT) for this purpose (4–6). Questions have even been raised about the necessity of routine follow-up imaging in pediatric (6) and adult (4) patients in clinically stable condition, as CT results do not appear to contribute to clinical management.

The late complications of blunt splenic injury, while rare, are real. These include delayed rupture (7), pseudoaneurysm formation (8,9), and enlarging posttraumatic cyst formation (10,11). Surgeons caring for these patients must balance the risk of missing late sequelae with the economic pressure to decrease utilization of resources. Ultrasonography (US) may be useful in fulfilling this need, since it is less costly than CT and uses no radiation or contrast material. The purpose of our study was to determine if US-documented healing of the pediatric spleen is related to the CT grade of injury, to review any posttraumatic complications, and to formulate an optimum grade-specific timetable for US follow-up of these injuries, with the goal of minimizing the number of scans obtained per patient.


   MATERIALS AND METHODS
TOP
 Abstract
 Introduction
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 References
 
At our level I trauma center between January 1991 and March 1997, 157 children and adolescents were evaluated for blunt traumatic splenic injury. Eight of these children and adolescents required surgical management; the remaining 149 were treated nonsurgically. Criteria for conservative management were hemodynamic stability, absence of peritoneal irritation, and absence of other abdominal injuries requiring surgery. Eighty patients did not return for US follow-up. Of the 69 patients who returned for follow-up US of their splenic injury, one had CT results that could not be obtained for review. The remaining 68 patients formed the study population (43 male, 25 female; age range, 1–16 years; mean age, 9 years). The distribution of injury grades was similar in this study group and the group that did not return for US follow-up.

At the time of injury, 54 of the 68 patients underwent CT at our institution with either a model 9800 Quick or CT HiSpeed Advantage system (GE Medical Systems, Milwaukee, Wis). The remaining 14 patients underwent CT at neighboring institutions on third- or fourth-generation units. All scans were obtained during or immediately after intravenous bolus administration of contrast material with 7–10-mm section collimation. In 66 of the 68 patients, scanning included the entire abdomen and pelvis. In two patients with outside studies, scanning included only the abdomen.

All CT scans were retrospectively reviewed, and splenic injuries were graded with the consensus of two radiologists (K.H.E., D.S.B.). A variation of the grading classification proposed by Brick et al (12) (Table 1) with estimation of the percentage of parenchymal involvement was used. Where only a laceration was visible, the classification by Mirvis et al (13) (Table 1) was used to grade the injury. The presence of peritoneal fluid was noted.


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  		TABLE 1. Method of Splenic Injury Grading
 
Per clinical routine, follow-up abdominal US was performed 6 weeks after discharge from the hospital and then every 4–6 weeks. All studies were performed with a model 128 unit (Acuson, Mountain View, Calif) or an HDI scanner (Advanced Technology Laboratories, Bothell, Wash). Color Doppler US was not performed.

The images were retrospectively reviewed by the same two radiologists with knowledge of the CT findings. Degree of healing was determined by the presence of either normal homogeneous splenic parenchymal echogenicity or a thin linear echogenic band presumably representing scar (14) (Fig 1). The presence of heterogeneous echogenicity, a hypoechoic collection (Fig 2), or an anechoic structure (presumably a cyst) was labeled as not healed.



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  		Figure 1a. Healing with scar. (a) CT scan of grade 2 splenic laceration (arrows). (b) Transverse follow-up US image shows thin, linear echogenic scar (arrows) at 9 weeks after injury.

 


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  		Figure 1b. Healing with scar. (a) CT scan of grade 2 splenic laceration (arrows). (b) Transverse follow-up US image shows thin, linear echogenic scar (arrows) at 9 weeks after injury.

 


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  		Figure 2a. Incomplete splenic healing. (a) CT scan shows grade 3 splenic injury (arrows) with moderate hemoperitoneum (arrowheads). (b) Follow-up US image at 7 weeks after injury shows that an irregular hypoechoic region remains (cursors).

 


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  		Figure 2b. Incomplete splenic healing. (a) CT scan shows grade 3 splenic injury (arrows) with moderate hemoperitoneum (arrowheads). (b) Follow-up US image at 7 weeks after injury shows that an irregular hypoechoic region remains (cursors).

 
Activity restrictions were maintained until the US results documented healing. The medical records of 20 study patients who underwent initial US but were not followed up until healing was complete were reviewed to determine if there were any delayed sequelae.


   RESULTS
TOP
 Abstract
 Introduction
 MATERIALS AND METHODS
 RESULTS
DISCUSSION
 References
 
In the 68 children and adolescents who returned for follow-up US, the distribution of splenic injury grade according to CT findings was as follows: 15 with grade 1, 33 with grade 2, 20 with grade 3, and 0 with grade 4 injuries. Forty-eight of these were followed up to complete US-documented healing: 14 of 15 with grade 1 (range, 4–12 weeks; mean, 7.0 weeks ± 0.6 [SD]), 24 of 33 with grade 2 (range, 6–17 weeks; mean, 9.5 weeks ± 0.7), and 10 of 20 with grade 3 (range, 6–29 weeks; mean, 16.6 weeks ± 2.6) injuries. When the Wilcoxon rank sum test was applied, the difference between the times to mean healing among the grades of injury was significant (P < .02).

Thirty-six of the 48 patients (75%) completing follow-up had normal homogeneous parenchymal echogenicity at healing (Table 2). The remaining 12 (25%) demonstrated a visible echogenic scar: two of 14 patients with grade 1 injuries, five of 24 with grade 2 injuries, and five of 10 with grade 3 injuries. While there was an increased incidence of scar formation with higher-grade injuries, the increase was not statistically significant (P > .05).


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  		TABLE 2. Healing Pattern
 
Only two patients developed anechoic structures meeting the criteria for a cyst; both had grade 2 injuries. Neither of these patients was followed up to complete resolution. One patient had a 2.6-cm cyst at initial US at 6 weeks, which decreased to 1.2 cm by his third US examination 23 weeks after injury (Fig 3). The other patient had only a 0.4-mm cyst at an 8-week postinjury US examination. Neither patient has returned to our institution with clinical sequelae of an enlarging posttraumatic cyst. The remaining 18 patients not meeting the criteria for healing had residual hypoechoic or heterogeneously echogenic areas within the spleen. Review of medical records in this group also failed to reveal any delayed sequelae.



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  		Figure 3a. Involuting posttraumatic fluid collection. (a) CT scan of grade 2 splenic injury (arrows). (b) Initial US image at 6 weeks after injury shows that the injury has developed a small anechoic fluid collection (cursors). (c) Delayed US image at 23 weeks after injury shows only a tiny residual cystic structure (cursors).

 


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  		Figure 3b. Involuting posttraumatic fluid collection. (a) CT scan of grade 2 splenic injury (arrows). (b) Initial US image at 6 weeks after injury shows that the injury has developed a small anechoic fluid collection (cursors). (c) Delayed US image at 23 weeks after injury shows only a tiny residual cystic structure (cursors).

 


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  		Figure 3c. Involuting posttraumatic fluid collection. (a) CT scan of grade 2 splenic injury (arrows). (b) Initial US image at 6 weeks after injury shows that the injury has developed a small anechoic fluid collection (cursors). (c) Delayed US image at 23 weeks after injury shows only a tiny residual cystic structure (cursors).

 
Eight of the 68 patients (12%) had no visible peritoneal fluid at CT at the time of injury. Four of these had grade 1 splenic injury and four had grade 2 injury. Neither of the two patients lacking pelvic CT scans from outside institutions was included in this group, as both had visible peritoneal fluid in the upper abdomen or paracolic gutter. No free fluid was seen on any of the follow-up US scans.

With our current protocol of follow-up imaging at 6 weeks, 10 of the 48 patients with documented healing (21%) required more than one US examination (grade 1, one of 14 patients [7%]; grade 2, three of 24 patients [13%]; and grade 3, six of 10 patients [60%]).


   DISCUSSION
TOP
 Abstract
 Introduction
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
References
 
The issue of follow-up imaging of blunt splenic injury in the era of nonsurgical management has been a source of controversy throughout the literature (4–6,15). While pseudocyst formation, delayed splenic rupture as the result of subcapsular hematoma, and pseudoaneurysm formation remain rare (7–11), the potential consequences of missing even one case remain formidable. It is this concern that drives most surgeons caring for these patients to seek objective documentation of injury healing before removing physical activity restrictions. Given the high degree of physical activity in the pediatric population as compared with that in adults (often including contact sports), this concern is valid.

If imaging documentation of healing of blunt splenic injury is required, one ideally minimizes costs and relative risk (radiation, intravenous contrast material, etc) while maximizing yield (ie, documenting healing with one examination). In studies in the literature, CT has been the predominant imaging modality (4–6). An informal survey (Emery KH, unpublished data, 1997) of the membership of the Society for Pediatric Radiology, or SPR, for which 95 radiology departments in North America responded, revealed that in nearly 80% routine follow-up imaging is performed to document splenic injury healing. The majority, approximately 65%, stated that they use CT.

However, US may be better suited to document injury healing at lower cost and risk. As these study findings have shown, there are significantly different healing times dependent on graded severity of injury. This relationship has been documented in children and adolescents with both CT (5) and US, as noted in a recent article in the surgery literature (15).

To our knowledge, there have been no direct comparative studies of CT and US to determine the relative accuracy of these two modalities for confirming splenic injury healing. One limitation of our study, as well as that of Lynch et al (15), is the assumption that use of the term "US-documented healing" implies that the organ has completely healed. To our knowledge, there have been no correlative US and histologic studies performed to confirm the assumption that normal parenchymal echogenicity equates to normal, functioning splenic tissue.

Researchers in a prior study (14) examining the use of US to observe healing in the traumatized spleen discovered that intrasplenic hematomas and contusions were resorbed over several months, and in two of 26 patients, linear echogenic bands were observed, which they attributed to fibrous scarring (14). While to our knowledge there is no histopathologic proof, the spleen is known to heal with fibrosis and scarring in areas of hemorrhage and infarction in patients with sickle cell disease (16). Realizing that hemorrhage and infarction occur in the traumatized spleen, it is reasonable to assume that scarring may also occur in this setting. Of interest, in the 58 patients examined by Lynch and colleagues (15) (including four with grade 4 injuries equivalent to complete splenic rupture), no echogenic parenchymal scars were reported. The reasons for this are not clear but may be related to equipment differences and scanning techniques, neither of which is specified in their article.

By combining the numbers of patients in the study by Lynch et al (15) with ours, we found that of the 106 patients followed up to complete US-documented healing, no complications were encountered. This emphasizes the rarity of these complications.

The two cysts in the patients in our study were likely resolving hematomas. Of interest, the patient with the decreasing posttraumatic cyst on serial US scans (Fig 3) had incurred a splenic injury 6 years earlier. We had no imaging documentation of complete healing of this prior injury. The possibility that this earlier injury was a precipitating factor for subsequent cyst development is interesting. None of the 20 patients who did not complete US follow-up subsequently presented to our institution with delayed injuries during the follow-up of 1–6 years.

In light of our results, we propose a more tailored approach to US follow-up of splenic injuries on the basis of injury grade to minimize the number of scans necessary to document healing (Table 3). Ten of our 48 patients with documented healing (21%) required more than one US examination following the current protocol of follow-up imaging at 6 weeks. While it is impossible to predict accurately the number of examinations that would not have been performed by using this revised protocol (given the relative variability of timing of the repeat studies), at least five of the six patients with grade 3 injuries who underwent two or more examinations would have required only one.


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  		TABLE 3. Injury Grade and Recommended US Follow-up
 
At our institution, the cost of an abdominal US examination is $81, as compared to $176 for an abdominal CT examination. A detailed cost analysis is beyond the scope of this article. However, the 68 patients in our study underwent a total of 86 US examinations. Had these all been CT examinations, the total cost would have been $15,136 instead of the $6,966 for US examinations, an increased cost of $8,170.

More important, since no complications were encountered in the 149 pediatric patients with blunt splenic trauma treated nonsurgically at our institution over approximately 6 years, the next logical question would be whether follow-up imaging of these injuries is even necessary in asymptomatic patients. Given healing rates documented here and in other studies in which CT or US has been performed (4–6,15) without complication noted, logical times for activity restriction could be devised on the basis of injury severity with a high degree of confidence for patient safety. Some of our colleagues in trauma surgery (17) are beginning to critically examine this issue, noting that results of routine serial abdominal CT examinations do not influence management or outcome.

In summary, we have shown that there is a clear relationship between the severity of blunt splenic injury in children and adolescents and the time course to US-documented healing; this information may be used to tailor the timing of follow-up imaging. While some question remains as to the need for follow-up imaging of these injuries, US provides the necessary information in a more cost-effective way than CT. While we encountered no clinically important complications, gathering further data in a larger patient population is necessary to confirm the efficacy of this approach.


   Acknowledgments
 
We thank Sallie Kroeger for her assistance in manuscript preparation and Jane C. Khoury, MS, for assistance with the statistical analysis.


   Footnotes
 
Author contributions: Guarantor of integrity of entire study, K.H.E.; study concepts, K.H.E., D.S.B.; study design, K.H.E., D.S.B., V.F.G.; definition of intellectual content, K.H.E., D.S.B., V.F.G.; literature research, K.H.E., A.S.B.; clinical studies, K.H.E., D.S.B., A.S.B.; data acquisition, K.H.E., D.S.B., A.S.B.; data analysis, K.H.E.; statistical analysis, K.H.E.; manuscript preparation, K.H.E.; manuscript editing, K.H.E., D.S.B., V.F.G.


   References
TOP
 Abstract
 Introduction
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 References
 

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This Article
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