What is the recommended initial imaging study for a patient with a suspected ruptured calyceal (kidney cup) and potential renal hematoma (kidney blood clot)?

Imaging for Ruptured Calyceal with Suspected Renal Hematoma

CT abdomen and pelvis with intravenous contrast is the recommended initial imaging study for suspected calyceal rupture and renal hematoma, as it provides rapid, comprehensive evaluation of both the collecting system injury and associated hemorrhage. 1, 2

Primary Imaging Recommendation

Contrast-enhanced CT (with IV contrast) is the optimal initial study because:

• It simultaneously visualizes the site of calyceal rupture through contrast extravasation into the perinephric space and identifies associated renal hematoma 3
• CT provides exact localization of the hematoma, detects active bleeding, and evaluates for complications such as infection or abscess formation 1, 2
• The study has high spatial resolution and speed, critical for potentially unstable patients with significant hemorrhage 1, 2
• Contrast-enhanced CT confirmed the diagnosis in documented cases of calyceal rupture, showing leakage of contrast at the calyx with perinephric fluid collections 3

When to Use Non-Contrast CT Instead

Non-contrast CT abdomen and pelvis is appropriate in specific circumstances:

• Patients with compromised renal function where contrast is contraindicated 1, 4
• When there is concern about additional contrast load if subsequent angiography may be needed 1
• Non-contrast CT can expeditiously confirm or exclude bleeding and is highly sensitive for detecting acute hemorrhage based on attenuation values 1, 5, 6
• High attenuation and mixed attenuation on non-contrast CT indicates acute to subacute bleeding, while low attenuation suggests chronic blood products 1

Critical Diagnostic Features to Identify

On contrast-enhanced CT, look for:

• Extravasation of contrast material from the renal calyx into the perinephric or paranephric spaces, which confirms calyceal rupture 3
• Perinephric fluid collections (urinoma formation) with or without associated hematoma 7, 3
• Obstructing calculi or other causes of increased intrapelvic pressure 7, 3
• Sentinel clot sign, which can suggest the area of bleeding even if active extravasation is not visible at the time of scanning 1

When to Consider Angiography

Reserve angiography for specific clinical scenarios:

• Hemodynamically unstable patients with high suspicion for active arterial hemorrhage requiring simultaneous diagnosis and treatment via transcatheter arterial embolization 1
• Known active arterial bleeding or contained vascular injury identified on CT that is amenable to endovascular intervention 1
• Angiography detects bleeding rates of 0.5-1.0 mL/min, but CTA is actually more sensitive, detecting rates as low as 0.3 mL/min 1

Common Pitfalls to Avoid

• Do not delay imaging due to concerns about contrast in renal disease—if renal function is severely compromised, simply perform non-contrast CT instead, which still provides excellent diagnostic information 1, 4, 6
• Do not assume small obstructing stones cannot cause calyceal rupture—even stones less than 5mm can generate sufficient intrapelvic pressure to rupture the calyx, particularly if located distally 3
• Do not overlook the diagnosis in patients with severe flank pain and normal laboratory markers—calyceal rupture can occur with normal labs, and imaging is essential for diagnosis 3
• Do not use ultrasound as the initial study—US has limited ability to visualize retroperitoneal structures and frequently misses renal injuries and calyceal ruptures 1, 2

Follow-Up Imaging Considerations

• CT serves well for follow-up evaluation of clinically suspected rebleeding, changes in hematoma size, or complications such as infection and abscess formation 1
• Serial imaging may be necessary to monitor resolution of the urinoma and hematoma after conservative or surgical management 7, 3