Trauma

The kidney is the most commonly injured organ following abdominal trauma. Children in particular are at an increased risk of renal injury due to several unique anatomical features of the pediatric axial skeleton and surrounding soft tissue. These include the less well-developed and ossified ribcage as well as decreased peri-renal fat and smaller paraspinal and abdominal muscles. These features all contribute to the increased susceptibility to renal trauma in the pediatric patient (McAleer et al. 2002b). Furthermore, preexisting congenital renal anomalies can also predispose to injury (Miller et al. 1966; McAleer et al. 2002a). Approximately 10%-12% of renal injuries in children are associated with some preexisting renal anomaly (Chopra et al. 2002). All children who present with a clinical suspicion of a renal injury following seemingly trivial trauma should be suspected of harboring some underlying abnormality. Ureteropelvic junction (UPJ) disruption is also rather unique in children. The UPJ is particularly vulnerable in children secondary to increased flexion of the spine and mobility of the kidney associated with rapid deceleration (Fig. 8.19).

The vast majority of renal injuries in children are due to blunt trauma secondary to motor-vehicle collisions, falls, or sports-related injuries. The most popular grading system utilized in pediatric renal trauma is that proposed by the American Association for the Surgery of Trauma (Table 8.4). It is also used in adults and has been validated to have good prognostic value (Kansas et al. 2004). Radiological evaluation typically involves contrast-enhanced CT scanning, which enables a rapid assessment of the upper urinary tract as well as intraabdominal viscera to rule out associated injuries (Fig. 8.20).

Table 8.4. American Association for the Surgery of Trauma Renal Injury Grading System

Gradea

Renal injury

1

No laceration, contusion or nonexpanding sub-capsular hematoma

2

Cortical laceration < 1 cm without evidence of urinary extravasation

Nonexpanding perirenal hematoma

3

Cortical laceration > 1 cm without evidence of urinary extravasation

4

Laceration extending through corticomedullary junction into collecting system

Segmental renal vascular injury with contained hematoma

Renal pedicle injury or avulsion

a Advance one grade for bilateral injuries up to grade III

a Advance one grade for bilateral injuries up to grade III

Fig. 8.20. Abdominal CT scan demonstrating grade 4 left blunt renal injury secondary to a snowboarding fall in a 12-year-old boy. This patient was successfully managed conservatively

The initial assessment of children presenting with renal trauma involves the rapid ascertainment of hemodynamic stability and evaluation to determine those who require emergent operative exploration. The indications for surgery are similar to that in adults, that is, ongoing hemodynamic instability, a pulsatile or expanding retroperitoneal hematoma, or, with rare exceptions, penetrating trauma. Relative indications include urinary extravasation, nonviable tissue, arterial injury, or incomplete staging.

Classically, all hemodynamically stable patients with a clinical suspicion of renal trauma underwent cross-sectional imaging. However, large outcome series have recently demonstrated that, depending on the degree of microhematuria and the nature of the injury, not all children with renal trauma require imaging (Buckley and McAninch 2004) Buckley and McAninch, in an expansive series of pediatric renal injuries, only recommend imaging if the urinalysis shows more than 50 red blood cells (RBC) per high power field (HPF) for those with a history of blunt trauma, or more than 5 RBC/HPF in those with penetrating renal trauma (Fig. 8.21). In their series, the majority of significant renal injuries (i.e., grade 2) were identified using these RBC/HPF values and no adverse sequelae occurred in patients for whom imaging was omitted (Buckley and McAninch 2004).

A nonoperative approach is also indicated for select patients with high-grade renal injuries. Recent reports have concluded that the majority of hemodynamically stable patients with grade IV injuries will not experience adverse outcomes nor suffer significant renal functional deterioration following a conservative management approach (Keller et al. 2004; Nance et al. 2004). An initial trial ofbedrest, urethral catheter drainage, and serial hematology is thus warranted in most stable patients with high-grade injuries. Ambulation is subsequently undertaken following resolution of hematuria and documentation of stable hemoglobin levels. Patients with complete renal fracture or significant contrast extravasa tion may benefit from temporary upper tract urinary diversion in order to prevent urinoma formation (Rogers et al. 2004). Patients who fail conservative management usually present with ongoing hemorrhage secondary to an expanding hematoma requiring transfusion, persistent urinary extravasation despite upper tract diversion, or abdominal and flank pain.

Occasionally, controversy occurs when a pediatric patient presents following trauma whose parents are members of Jehovah's Witnesses and therefore refuse all blood products. Although this is fortunately a rare occurrence, the situation must be recognized early, and the appropriate safeguards obtained, so as not to compromise patient care. One must be cognizant and respectful of that patient's family's choice that the use of blood products is absolutely condemned within their religious belief system. Therefore, all possible attempts must be made by medical staff in order to prevent the need for transfusion. The early involvement of an expert hematologist will aid in the decision to use hemoglobin substitutes and various colloid and crystalloid fluid expanders, as necessary. However, in the event that a pediatric patient requires blood or blood products as the only life-saving alternative, a court injunction maybe granted in order to temporarily award custody of the child to the state. Most hospitals and jurisdictions will have a senior administrator and judiciary official on call in order to facilitate this process in the event of such an emergency.

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