Radiation to groin, ipsilateral testicle, or labia
Abdominal pain
Associated intra-abdominal injury concern
Peritoneal signs
Systemic symptoms
Lightheadedness or syncope
Hemorrhagic blood loss marker
Orthostatic symptoms
Nausea and vomiting
Pain-related vs ileus from retroperitoneal hemorrhage
Risk factors and past medical history
Pre-existing renal conditions
Solitary kidney
Stakes of any injury markedly increased
Nephrology involvement mandatory
Renal anomalies
Horseshoe kidney
Hydronephrosis
Polycystic kidney disease
ADPKD increases vulnerability
Lower-energy mechanisms can cause significant injury
Medications and coagulation
Anticoagulants
Warfarin (INR)
Direct oral anticoagulants (DOACs)
Antiplatelet agents
Aspirin, clopidogrel
Increased bleeding risk even in low-grade injury
Surgical history
Prior renal surgery or nephrectomy
Determines functional reserve
Anatomic distortion on imaging
Prior abdominal or retroperitoneal surgery
Adhesions affecting hemorrhage containment
Physical Exam
Vital signs and hemodynamic assessment
Hemodynamic stability markers
Blood pressure
SBP < 90 mmHg triggers hemorrhagic shock protocol
Serial readings every 15 minutes acutely
Heart rate
Tachycardia > 100 bpm as bleeding marker
Relative bradycardia in vasovagal response
Respiratory rate
Increased rate with thoracic injury
Pain-related splinting
Lactate and perfusion indicators
Capillary refill > 2 seconds
Peripheral hypoperfusion marker
Mental status changes
Hemorrhagic shock neurological effect
Class III-IV hemorrhage indicator
Flank and abdominal exam
Flank findings
Ecchymosis (Grey Turner sign)
Retroperitoneal blood tracking
May be delayed 24-48 hours
Palpable mass
Expanding perirenal hematoma
Urinoma development
Costovertebral angle tenderness
Direct renal parenchymal injury
Reproducible on percussion
Abdominal exam
Distension
Retroperitoneal hemorrhage extension
Associated intra-abdominal injury
Peritoneal signs
Guarding and rigidity
Intra-abdominal injury concern
Lower rib assessment
Ribs 10-12 tenderness
Associated renal injury in 10-20% of lower rib fractures
Crepitus on palpation
Seatbelt sign or contusions over flank
Pattern of force applied
Underlying organ injury correlation
Genitourinary and additional exam
Urethral meatus inspection
Blood at meatus
Urethral injury concern before catheter placement
Urology consultation before urethral catheterization
Lumbar spine assessment
Lumbar transverse process fracture tenderness
Associated renal injury risk
L1-L3 level involvement
Skin survey
Abrasions and contusions over flank or abdomen
Force vector determination
Associated visceral injury clue
Penetrating wound assessment
Entry and exit wounds
Trajectory assessment
PITFALLS
Examination limitations
Grey Turner sign delayed appearance
Normal initial exam does not exclude retroperitoneal hemorrhage
Reassess at 12-24 hours if symptoms persist
Hematuria absence does not exclude significant renal injury
Vascular pedicle injuries may present with minimal hematuria
High-energy mechanism warrants imaging regardless
Differential Diagnosis
Life-threatening diagnoses
Higher-grade renal injuries
AAST Grade III-V renal laceration
ICD-10 S37.061 (major renal laceration)
Collecting system involvement or vascular pedicle injury
Renal pedicle avulsion or arterial thrombosis
Absent nephrogram on contrast CT
High-energy deceleration mechanism
Ureteral injury
Rare in blunt trauma < 1%
Delayed contrast extravasation on CT urogram
Associated solid organ injuries
Splenic laceration
Left-sided mechanism
ICD-10 S36.031
Hepatic laceration
Right-sided mechanism
ICD-10 S36.113
Pancreatic injury
Epigastric force vector
Elevated lipase
Mimics and adjacent diagnoses
Musculoskeletal injuries
Lower rib fractures (ribs 10-12)
ICD-10 S22.31-S22.39
Normal urinalysis
Lumbar transverse process fracture
Posterior element tenderness
CT spine findings
Flank muscle contusion
Superficial tenderness
No hematuria
Retroperitoneal hemorrhage (non-renal)
Lumbar vessel injury
No renal parenchymal abnormality on CT
Periaortic hematoma location
Psoas hematoma
Hip flexion pain
Isolated retroperitoneal location
Adrenal hemorrhage
Can mimic perirenal hematoma on imaging
Distinct suprarenal location
Cortisol axis monitoring if bilateral
Other considerations
Pre-existing renal pathology unmasked by trauma
Renal cell carcinoma with traumatic bleeding
ICD-10 C64
Disproportionate hemorrhage for mechanism
Renal cyst rupture
Known cystic disease history
Cystic vs solid differentiation on CT
Renal abscess
Febrile presentation
Fluid collection with wall enhancement
Laboratory Tests
Urinalysis and hematuria evaluation
Urinalysis
Hematuria present in 88-94% of renal trauma
Microhematuria defined as > 3 RBC/HPF
Gross hematuria visible to naked eye
Degree of hematuria does not reliably predict injury grade
Vascular pedicle injuries may have minimal or no hematuria
High-energy mechanism warrants CT regardless of UA
Urine microscopy
RBC casts
Intrinsic renal disease consideration
Glomerulonephritis differentiation
Myoglobinuria screen
Associated rhabdomyolysis in polytrauma
Dipstick positive blood without RBCs on microscopy
Hematologic and coagulation studies
Complete blood count
Baseline hemoglobin/hematocrit
Serial monitoring every 6 hours if gross hematuria
Hemoglobin drop > 20 g/L suggests ongoing hemorrhage
Platelet count
Thrombocytopenia increases bleeding risk
Target > 50 x10^9/L if active hemorrhage
Coagulation studies
PT/INR
Warfarin anticoagulation quantification
Target INR < 1.5 for hemostasis
PTT
Heparin monitoring
Factor deficiency screen
Anti-Xa level if on DOAC
Guides reversal agent dosing
Rivaroxaban, apixaban, edoxaban
Metabolic and organ function
Basic metabolic panel
Serum creatinine
Baseline renal function
Serial monitoring post-injury
Electrolytes
Sodium and potassium for resuscitation guidance
Bicarbonate for acid-base status
Blood urea nitrogen
Prerenal component from hypovolemia
BUN:creatinine ratio > 20:1 suggests prerenal
Additional trauma labs
Type and screen
Transfusion preparation
Crossmatch if active hemorrhage
Lactate
> 2 mmol/L indicates tissue hypoperfusion
Serial lactate clearance targets
Lipase
Associated pancreatic injury screening
Mechanism-dependent indication
Diagnostic Tests
Scoring Systems
AAST Organ Injury Scale for kidney (2018 revision)
Grade I: contusion or non-expanding subcapsular hematoma, no laceration
Normal nephrogram on CT
Management: non-operative, observation
Grade II: perirenal hematoma confined to Gerota's fascia; laceration ≤ 1 cm depth, no urinary extravasation
Perirenal hematoma contained within Gerota's fascia
Management: non-operative in most cases
Grade III: laceration > 1 cm depth without collecting system rupture or urinary extravasation
Deep parenchymal injury
Management: non-operative with close monitoring
Grade IV: laceration involving collecting system with urinary extravasation; renal artery or vein injury with contained hemorrhage; segmental infarction
ICD-10 S37.062 (major renal laceration with collecting system disruption)
Management: angioembolization or surgical consideration
Grade V: shattered kidney; avulsion of renal hilum with devascularization; laceration of segmental renal vein or artery with contained hematoma
Highest mortality
Management: operative in most cases
AAST clinical significance
Grade I-II: 75-98% of all renal injuries
Heals without complications in vast majority
Non-operative management standard of care
2018 revision incorporated vascular injury into grading
Improved correlation with management requirements
Society of Interventional Radiology position statement supports endovascular intervention for Grade IV-V
MRI
MRI indications in renal trauma
Role is limited in acute trauma setting
CT remains gold standard for acute evaluation
MRI reserved for specific circumstances
Indications for MRI over CT
Contrast allergy where CT urogram contraindicated
Radiation concern in pediatric or pregnant patients
Characterization of equivocal renal lesion found on CT
MRI findings in renal contusion
Focal T2 hyperintensity in renal parenchyma
Corresponds to edema and bruising
No disruption of cortical outline
No collecting system involvement
Intact Gerota's fascia signal
Absence of perirenal T2 bright fluid collections
MRI limitations
Not recommended for acute trauma triage
Longer acquisition time
Limited availability in emergency setting
Motion artifact degrades image quality
Requires cooperative patient
Breath-hold sequences needed
CT
CT abdomen/pelvis with IV contrast
Gold standard for renal trauma evaluation
Sensitivity > 98% for significant renal injury
ACS Best Practices Guidelines support CT as primary modality
Indications for CT in renal trauma
Gross hematuria regardless of mechanism
Microhematuria with hemodynamic instability (SBP < 90 mmHg)
Additional CT indications
High-energy mechanism (fall > 3 m, high-speed MVC)
Flank ecchymosis or lower rib fractures
Clinical suspicion despite absence of hematuria
CT protocol for renal trauma
Triple-phase imaging recommended
Arterial phase: vascular injury and active extravasation
Cirillo B, Duranti G, Cirocchi R, et al. Journal of Clinical Medicine 2025
High-volume urban emergency department retrospective analysis
Real-world outcome data for non-operative management
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