Blunt renal trauma—blessing in disguise?

Blunt Renal Trauma—Blessing in Disguise? By Priya Chopra, Dickens St-Vil, and Salam Yazbeck Montreal, Quebec

Purpose: The purpose of this study was to quantify pathologic lesions of the kidney found incidentally during the workup of a blunt renal trauma. Methods: A retrospective review of the medical records of 103 patients ages 0 to 18 years with blunt renal injuries admitted to a level 1 pediatric trauma center between January 1, 1991 and December 31, 1999 was performed. All patients underwent ultrasonography and Doppler of their renal vessels. Additional investigations with computed tomography (CT) scan, cystography, or nuclear medicine functional studies were performed as indicated. Results: Coexisting urogenital lesions were identified in 13 of 103 (12.6%) patients reviewed, and 7 (54%) required surgical treatment. The majority of the patients (9 of 13, 69%) suffered minimal trauma. All patients presented with gross hematuria as their main symptom. Stenosis of the uretero-pelvic junction was the most frequent diagnosis (n ⫽ 7): 3 patients required uretero-pyeloplasty, and 3 required nephrectomy. Two heterogeneous renal masses were discovered in which

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LUNT TRAUMA results in renal injury in 10% of the pediatric population.1-3 When compared with an adult blunt trauma, the pediatric kidney is at higher risk to be injured.4 Various anatomic factors have been cited to explain this predisposition. The pediatric kidney is considered to be of a relatively larger proportion of the body and also is located lower in the abdomen. Children retain fetal lobulations that have been associated with a higher incidence of parenchymal injury and lower pole amputations. There is less protection of the kidney related to a thoracic cage that is more pliable, weaker abdominal musculature, less perirenal fat, and weaker renal capsule when compared with an adult.1,3,4 For similar reasons, congenital anomalies also are thought to increase the risk of sustaining a major renal injury as a result of blunt trauma with an incidence reported in the literature between 5% and 17%.2,3 This study from a single institution is a descriptive review of the presentation, radiologic imaging, underlying pathology, and surgical treatment of traumatic renal injuries in patients with previously unknown underlying renal malformations. MATERIALS AND METHODS All children 18 years or younger admitted to a level 1 pediatric trauma center over a 9-year period (January 1, 1991 through December 31, 1999) with renal injuries from blunt trauma were identified, and the

Journal of Pediatric Surgery, Vol 37, No 5 (May), 2002: pp 779-782

the diagnosis of a malignant process could not be eliminated; elective resection and open biopsy were performed. The diagnoses of multicystic kidney and solitary cyst with complex hematoma, respectively, were confirmed on pathology. Grade III ureterovesical reflux with pyelonephritis (n ⫽ 1), polycystic kidney (n ⫽ 1), extrarenal pelvis without obstruction (n ⫽ 1), and horseshoe kidney (n ⫽ 1) were the other lesions discovered. Conclusions: Pathologic lesions of the urinary tract are uncommon; however, they may complicate an otherwise negligible renal trauma. The diagnostic and therapeutic approach to blunt renal trauma must be modified in these cases. A high index of suspicion must be maintained when a patient presents with gross hematuria with a minimal force blunt abdominal trauma. J Pediatr Surg 37:779-782. Copyright 2002, Elsevier Science (USA). All rights reserved. INDEX WORDS: Renal trauma, congenital anomalies.

charts of those children with congenital renal abnormalities were reviewed in detail. All children underwent abdominal ultrasonography with Doppler of their renal vessels. Computed tomography (CT), cystography, intravenous pyelography, and nuclear medicine renography (DTPA, DMSA, MAG-3) were performed as needed. Information collected included initial hemodynamics, presence of hematuria, mechanism of injury, imaging performed, and treatment. Grading of injuries was done based on the scale devised by the American Association for the Surgery of Trauma. All patients underwent follow-up, and additional imaging was obtained when clinically indicated.

RESULTS

A total of 103 patients with blunt renal trauma were treated at our center during the period specified. Thirteen children, treated for blunt renal injuries in the setting of an underlying congenital renal malformation, were identified for an incidence of 12.6%. A male predominance was noted (Table 1). Ten patients (77%) had isolated renal injuries. All patients were hemodynamically stable, From the Division of Pediatric Surgery, Hoˆpital Sainte-Justine, Montreal, Quebec, Canada. Address reprint requests to Dickens St-Vil, MD, Hoˆpital SainteJustine, 3175 Ste. Catherine Rd, Montreal, Quebec, Canada H3T 1C5. Copyright 2002, Elsevier Science (USA). All rights reserved. 0022-3468/02/3705-0023$35.00/0 doi:10.1053/jpsu.2002.32286

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Table 1. Patient Characteristics Mean age years (range) Gender

10.5 (4-18) 2 girls (15%) 11 boys (85%)

Grade of Injury I II III IV V Only hydronephrosis on ultrasound scan Associated injuries None Splenic Pulmonary Orthopedic

2 1 1 1 2 6 10 1 1 1

3 patients had admission hemoglobin values less than 100 g/dL, and 2 required intensive care monitoring. No patients died as a result of their trauma. All patients who had renal injuries presented with gross hematuria, and all injuries were sustained as a result of fairly minor trauma (Table 2). One patient fell from a height of 14 feet; the remaining 12 fell less than 10 feet, from a bicycle, or had a minor sports injury. There were no patients involved in motor vehicle collisions. All patients underwent abdominal ultrasonography with Doppler of the renal vessels. Additional investigations included intravenous pyelogram (n ⫽ 1), oral and intravenous infused abdominal-pelvic CT (n ⫽ 5), cystography (n ⫽ 3), DTPA/DMSA scans (n ⫽ 6) and MAG-3 (n ⫽ 2). Nine patients underwent 2 investigations; 4 patients required 3 separate diagnostic tests. Seven patients (54%) required surgical intervention (Table 3) to treat their underlying congenital malformation or to exclude the presence of underlying malignancy with superimposed hematoma. All but one of the surgical interventions were performed under nonurgent (defined as greater than 24 hours postadmission) circumstances.

In total, 3 uretero-pyeloplasties were performed for newly diagnosed uretero-pelvic junction stenosis with significant obstruction documented on functional testing. Three nephrectomies were performed. In another case, imaging could not rule out a malignant cystic tumor, and the final pathology finding was a multicystic kidney with hematoma. The other nephrectomy was performed at exploratory laparotomy for a grade V injury associated with urinoma. Final histology results showed underlying hydronephrosis secondary to significant uretero-pelvic junction stenosis. In a second case in which malignancy could not be eliminated as an underlying pathology, open renal biopsy was performed for the definitive diagnosis of simple renal cyst with associated complex hematoma. All but 2 children had follow-up appointments. No cases of hypertension, cysts, arteriovenous fistulas, nephrolithiasis, or hypoplasia were found. DISCUSSION

In this series, 12.6% of all blunt renal trauma occurred in pathologic kidneys. This figure is consistent with the ranges published in the pediatric trauma literature.2,5 Cass5 found 2 of 248 (1%) congenital abnormalities in his review of renal trauma with a fortuitous discovery of a case of hydronephrosis and a second case of bilateral hydroureters. McAleer et al2 discussed 4 of 50 (9%) cases of preexisting pathology. They found horseshoe kidney (n ⫽ 1), vesico-urethral reflux (n ⫽ 1), multicystic dysplastic kidney (n ⫽ 1), and small kidney (n ⫽ 1). In the adult trauma literature, Giannopoulos et al6 found that 3.5% (24 of 675) of blunt renal traumas involved kidneys with underlying pathology. In this age group the underlying pathology included nephrolithiasis (n ⫽ 12), renal masses (n ⫽ 7), unilateral renal agenesis (n ⫽ 1), duplication of renal pelvis (n ⫽ 1), bilateral ureterocele (n ⫽ 2), and retroperitoneal fibrosis (n ⫽ 1). There are several differences in presentation when normal and pathologic kidneys are subject to blunt ab-

Table 2. Clinical Presentation and Treatment Based on Underlying Pathology

Hematuria Gross Micro Hb ⬍100 g/dL Mechanism of injury Bicycle/fall Sports related Surgery Pyeloplasty Nephrectomy Open biopsy

Stenosis UPJ

Renal Mass

Reflux

Polycystic Kidney

Extrarenal Pelvis

Horseshoe Kidney

Other

6

2

1

1

1

1

1

1

—

1

1

—

—

—

3 3

2 —

1 —

1 —

1 —

1 —

1 —

3 2 —

— 1 1

— — —

— — —

— — —

— — —

— — —

Abbreviation: UPJ uretero-pelvic junction.

BLUNT RENAL TRAUMA

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Table 3. Investigation and Surgical Management Age (yr)/ Sex

12/M 8/M 13/M

Finding on Ultrasound (Grade of Injury or HDN)

Other Investigation

Underlying Congenital Malformation

Surgical Management

DTPA DTPA CT

R UPJ stenosis, 12–17% function L UPJ stenosis R UPJ stenosis

R uretero-pyeloplasty (elective) L uretero-pyeloplasty (elective) R nephrectomy (urgent)

Cystogram MAG-3 CT DMSA

L UPJ stenosis, extra-renal pelvis

L uretero-pyeloplasty (elective)

L UPJ stenosis

L nephrectomy (elective)

Polycystic kidneys ?tumor Complex R renal cyst ?tumor

L nephrectomy (elective)

8/M

Hydronephrosis Hydronephrosis Grade IV with renal pelvis disruption Hydronephrosis Urinoma Hydronephrosis

18/M

Grade V with urinoma

10/F

Hydronehprosis Grade III

CT

10/M

Grade II

CT

R renal open biopsy (elective)

Abbreviations: R, right; L, left; HDN, hydronephrosis; CT, computed tomography of abdomen/pelvis with oral plus intravenous contrast; UPJ, uretero-pelvic junction; Nuclear function testing—DMSA, dimercaptosuccinic acid, radio-pharmaceutical agent used for optimal images of renal parenchyma; DTPA, diethylene-triamine-penta-acetic acid, radio-pharmaceutical used to evaluate renal function and depict whether dilatation is secondary to obstruction; MAG-3, radio-pharmaceutical that visualizes both renal parenchyma and function.

dominal forces. Motor vehicle collisions have been the cause of most (47% to 82%) pediatric blunt traumatic renal injuries in previous series.1-3,7,8 In this report, most of the mechanisms of injury involved fairly minimal forces. This point lends support to the theory that abnormal renal size, position, consistency, or location diminishes the effectiveness of the natural protective mechanisms and predisposes the kidney to injury even with minimal insult. All injured pathologic kidneys presented with gross hematuria prompting immediate investigation with ultrasonography and Doppler of renal vessels. In all 13 cases, the ultrasound scans showed either varying grades of hematoma, or hydronephrosis. However, all 13 patients in the group require additional radiologic investigation. Further radiologic investigations were performed to document anatomic details and for assessment of renal function and include CT scan or nuclear medicine studies. In adult trauma protocols, radiographic evaluation is performed on any patient presenting with either gross hematuria or microscopic hematuria combined with hemodynamic instability.6 It has been argued that hypotension rarely develops in children who sustain major blunt renal injuries; thus, the criteria of microscopic hematuria

accompanied by hypotension are a nonreliable indicator of major renal injury.9 At our institution, if there is no other indication for abdominal imaging, the presence of gross hematuria or microscopic hematuria with a deceleration mechanism or persistence of microscopic hematuria 24 hours after presentation prompts ultrasound or Doppler investigation.10,11 Pediatric kidneys are more likely than their adult counterparts to be injured in a blunt abdominal trauma. Underlying congenital malformations causing hydronephrosis (UP junction stenosis, extrarenal pelvis) predispose the kidney to significant injury even with minor forces. The larger size and possible increased fluid density could be the related factors. Other malformations such as horseshoe kidneys (lower position) also can be injured more easily because the protective thoracic cage is too high. Abnormalities of parenchymal consistency as a result of reflux and resulting pyelonephritis or cystic kidney disease (single or multiple) also could be hypothesized to provide less resistance to traumatic forces. Thus, a high index of suspicion should be maintained to rule out a congenital renal malformation in any child presenting with gross hematuria after a relatively minor trauma.

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