Table 1.3 Long‐term follow‐up recommendations.
| AUA [34] | EAU [81, 82] | SIU/WHO [30] |
|---|---|---|
| Periodic monitoring of blood pressure up to a year after injury. Do not recommend routine DMSA (dimercaptosuccinic acid) or other functional nuclear scans. | Physical exam, urinalysis, “individualized radiological investigation,” serial blood pressure monitoring, and determination of renal function. Follow‐up should continue until healing is complete and lab findings have stabilized. Monitoring may need to be continued for years to evaluate for latent renovascular hypertension. | No specific recommendations, but consensus statement does cite a study that recommends that all grade IV/V injuries follow‐up with documentation of renal function by quantitative assessment |
Short‐term monitoring and follow‐up of trauma patients as previously specified is intended to detect complications and offer appropriate additional interventions. In terms of long‐term follow‐up, there is no consensus and most trauma series do not have the luxury of long‐term follow‐up, given the difficulty in following up the acutely injured population [80]. Follow‐up recommendations are outlined in Table 1.3.
Secondary Hemorrhage
Delayed hemorrhage can be a life‐threatening complication of renal trauma that can arise as a result of the parenchymal injury itself, segmental arterial bleeding, or ruptured arteriovenous fistulas (AVFs) or pseudoaneurysm. One series of grade III–IV blunt injuries managed conservatively showed a 13–25% rate of delayed bleeds, with the caveats that this number varies significantly by series and the majority of the literature on delayed bleeds is derived from cases of penetrating trauma [83‐85]. Delayed bleeds occur most commonly in the first 2–3 weeks after trauma, although case reports have described trauma‐associated bleeds occurring as late as 15 or 20 years after the initial insult [83-84]. Renal trauma from stab wounds demonstrate the onset of secondary hemorrhage in the 2–36 day time‐frame [30, 85].
Most often, delayed hemorrhage is caused by AVF or pseudo‐aneurysm [30]. The occurrence of pseudoaneurysm after blunt renal trauma has been described in several case reports but is a rare event [83,86–88]. Pseudoaneurysms are believed to form within the surrounding tissue after an arterial injury, likely due to shear stress in blunt renal trauma, where the space around the vascular injury is temporarily tamponaded by coagulation. Eventually, the intravascular and extravascular space may recannulate after degradation of the clot and necrosis of the surrounding tissue, leading to the formation of a pseudoaneurysm which can then grow and rupture [88, 89].
AVF after blunt trauma is also a rare event and has been reported in several case reports [89–92]. The fistula is thought to form as a result of injury to an arterial and venous vessel in close proximity to one another, usually within the renal parenchyma. Initially the bleeding may be tamponaded by a clot; as the hematoma resorbs the arterial bleeding can resume, draining into the nearby lacerated vein [30].
New‐onset or worsening hematuria, flank pain or mass, a hematocrit drop, or even new‐onset hypertension, should raise suspicion of a delayed bleed. CT angiogram or conventional angiography is the preferred imaging modality, although diagnosis can be made with ultrasound in some cases. Depending on the etiology, either surgical management or super‐selective embolization is employed, with the goal of controlling the bleeding while preserving as much renal function as possible [93, 94]. Complications of embolization can include abscess, infarction, renal insufficiency, and pulmonary embolization of coils [25, 84, 94, 95].
Urinary Extravasation and Perinephric Abscess
AUA guidelines recommend that clinicians perform urinary drainage in the presence of complications such as enlarging urinoma, fever, increasing pain, ileus, fistula, or infection [34].
Renal injuries with urinary extravasation at initial presentation can for the most part be managed conservatively given the high rates (90%) of spontaneous resolution, although repeat imaging is intended to evaluate for persistent leaks, urinomas, or perinephric abscesses that require additional intervention such as stenting or percutaneous drainage [3046–48, 98]. Patients with devitalized renal parenchyma in conjunction with urinary extravasation tend to have increased morbidity and may require more aggressive management [80,96–98]. Furthermore, patients with concomitant injuries, such as pancreatic or colonic injuries, may also have a higher likelihood of developing complications [25,99–101].
In practice, approximately 29% of patients with high‐grade renal trauma undergo ureteral stent placement [102]. To date, there are no standard guidelines on duration of stent and Foley placement for high‐grade renal trauma. In a single center series, an indwelling stent for six to eight weeks was associated with favorable outcomes [103]. Generally, maintaining a Foley catheter while a stent is in place helps with healing by preventing antegrade reflux of urine to the kidney, minimizing pressure in the collecting system, and enhancing urinoma drainage. Percutaneous drains may be necessary in cases of increasing urinoma size, complexity, and/or infection [34].
Renal Insufficiency
The lack of long‐term follow‐up after renal trauma makes it difficult to determine the true rates of renal insufficiency after trauma. One study evaluating pediatric blunt renal trauma patients managed conservatively found that the decline in percentage of renal function of the injured renal unit correlated to the severity of renal injury, with 44.7 ± 8.4% residual function for grade II–III injuries, 41.8 ± 9.2% residual function for grade IV injury, and 29.5 ± 7.9% residual function for grade V injuries [104]. Notably, all patients had normal serum creatinine at follow‐up. This group re‐assessed renal function for a subset of these patients at one year post‐injury, finding that renal function remained stable over this time period [105]. These results are supported by another study of 67 renal injuries (36% blunt trauma) that underwent post‐injury dimercapto‐succinic acid renal scan and found that the mean decrease in renal function corresponded to injury grade (p < 0.005 in multivariate analysis), with a mean decrease in renal function of 15% for grade III, 30% for grade IV, and 65% for grade V injuries [106]. In multivariate analysis, there was no difference in the decrease in renal function between blunt and penetrating renal injury or in those injuries that were managed operatively versus conservatively.
A study evaluating 52 patients who underwent renal reconstruction after renal trauma found that renal function on the reconstructed side had a mean 39.3% preservation of function, with 81% of patients having more than one‐third function of the injured kidney based on radionucleotide scintigraphy [107].
Two studies evaluated the rates of chronic kidney disease after renal trauma. One compared trauma patients with and without renal injuries, finding that 230 patients without renal injury had an incidence of acute kidney injury of 17.4% compared to 11.4% in the patients with renal injury [108]. Another multi‐institutional study evaluating grade IV and V renal injuries (49% blunt trauma) found that 6/89 patients developed chronic kidney disease (CKD) (serum creatinine range 2.0–15.6 mg/dl), and of these 6 patients, 3/5 with long‐term follow‐up developed progressive and permanent renal failure requiring dialysis