Several studies have demonstrated the success of the non-operative management of renal injuries, indicating that the decision concerning the expectant or surgical management does not have to be made based only on the grade of the tomographic staging of the injury, but also by taking into consideration the clinical picture, the hemodynamic state, the presence of associated injuries and the blood transfusion requirements [2, 3, 27–30].
The reduction of the renal volume observed by computed tomography in 50% of the patients and the percentage of renal volume reduction were found to be related to renal trauma severity as defined by OIS, including the subdivisions of grades IV and V. Our results confirm that the degree of renovascular injury and the extent of nonperfusion of the kidney at admission CT scan appear to determine the functioning volume loss observed by nuclear scanning at the follow-up assessment was highlighted by previous series [1, 10].
Functional studies of the kidneys, like angiography and flow measurements, using MR imaging were not possible until recently, because motion from respiratory cycle and perturbation of magnetic field, near the interface between gas within bowels and pericolonic fat interfere with data acquisition. The sensitivity and specificity in the detection of significant renal stenosis (> 50%) are 100% and 93%, respectively [23–26]. In this study MR imaging, no renal artery stenosis was founded. Although the asymmetry between the blood flow in both kidneys was detected in most cases, there was no significant difference among the different grades of renal trauma.
DMSA renal scintigraphy is the standard procedure for estimating the functional renal mass because its yields high quality static images of the renal cortex [31, 32]. Other series showed that non-operative treatment of renal trauma, specifically in more advanced grades, can be safe with low index of complications and the correlation between AAST grade and relative renal function [1, 12–14]. These findings are closed to our results (Figure 1). However, with the subdivisions of the functional outcome of the renal traumas grades IV and V, differentiating the vascular and parenchymal injuries, revealed that the renal injuries of grade III had produced the same functional outcomes as those of grade IV with extravasation (Figure 2). The vascular renal injury grades IV had a significantly worse functional result than those of grades III and IV with extravasation (Table 4). This finding is in disaccording with another previous study . Additional analysis of a larger sample size from multiple institutions should be performed to validate these findings.
Dugi et al even proposed a subclassification of grade IV renal trauma to help decide between non operative management (grade 4a – low risk) and early surgery or angiographic embolization (grade 4b – high risk) based on the presence or absence of a series of important radiographic risk factors, including perirenal hematoma, intravascular contrast extrasavation and renal laceration complexity .
This discussion is in accordance with the revision proposed to updated the AAST OIS for renal trauma . Actually, the classification is based primarily on parenchymal laceration depth and the presence or absence of vascular injury . It is necessary this revision to eliminate existing confusion and inaccurate renal staging by creating a precise and complete renal staging classification to guide clinical management and to facilitate renal trauma research, particularly in grades IV and V . Also, the functional outcome of renal trauma based on the initial radiological evaluation would help us avoid multiple time and cost consuming procedures to salvage a nonfunctional kidney .
Future alterations in the current classification of renal injury gravity would be advanced by imaging diagnostic methods that would allow the identification of extravasation of contrast in arterial segments, quantitative measures of the volume of the hematoma and other variables that would predict, in a more precise manner, the results of renal trauma . Information about evaluation of renal function after trauma could be included in revision of AAST providing additional strength to the injury scale as an instrument to predict clinical outcomes after renal trauma.
The complications that may arise from non-operative management of renal trauma include: urinoma, perinephritic abscess, delayed hemorrhage and arterial hypertension [29, 30].
Some authors who assessed the incidence and prevalence of post-traumatic renal hypertension [35–41], with different times of follow-up, have commented on the factors related to the etiology of arterial hypertension [19, 42–45].
Monstrey et al ., who studied 622 patients with renal trauma to evaluate the incidence and prevalence of posttraumatic arterial hypertension, did not observe any increase in the incidence of arterial hypertension. They found no definitive relation between hypertension and renal trauma. In the same article, the authors reviewed 71 publications from the medical literature which showed that more than 90% of 223 cases previously described as posttraumatic renal hypertension, in fact did not confirm with the diagnosis due to the following reasons: documented normal blood pressure before the injury, associated renal disease, non-validated hypertension, no definition of the anatomical injury or its functional significance. Most documented cases can be classified into one of three types of renal lesions known to produce renal ischemia with subsequent development of hypertension, namely, renal artery stenosis (Goldblatt mechanism) , external renal compression (Page mechanism) , and intra-renal arteriovenous fistula . In this study, none of these types of damage was founded in imaging evaluation of posttraumatic renal injuries.
The diagnostic refinement derived from the use of ambulatory blood-pressure monitoring allowed the identification of 29% of cases of arterial hypertension (9 patients). No previous study in the literature on renal trauma and arterial hypertension had used ambulatory blood pressure monitoring. It is important to note the low average age of the hypertensive patients with future cardiovascular risks associated with the high rate of familial arterial hypertension. There was no direct correlation between the grade of renal injury and the presence of arterial hypertension, although 66.7% of the cases had renal injury of grade III. Morphological evaluation by both computed tomography and magnetic resonance angiography excluded any possibility of renal artery stenosis, external renal compression or arteriovenous fistula. Furthermore, there was no correlation between a serious reduction of renal function found by DMSA renal scintigraphy and the presence of arterial hypertension.
In the patients with renovascular hypertension, the dynamic renal scintigraphy with the use of the 99mTc EC demonstrates a gradual accumulation of the radionuclide in the kidney affected during the phase of the study after captopril administration. This can be explained by the reduced glomerular filtration rate, measured scintigraphically as delayed uptake and cortical retention. Investigators have reported the test to have approximately 90% sensitivity and more than 95% specificity [31, 46].
The diagnosis of a rennin-dependent renovascular hypertension was excluded in all patients, suggesting that arterial hypertension may be essential.