Management of Mild Left Renal Pelvis Fullness Without Stones
For an asymptomatic patient with mild left renal pelvis fullness and no stones or focal lesions on ultrasound, obtain a detailed clinical history focusing on any episodes of flank pain, urinary symptoms, or risk factors for obstruction, then proceed with either CT urography (CTU) or non-contrast CT abdomen and pelvis to identify the underlying cause of hydronephrosis. 1
Initial Clinical Assessment
Before proceeding with additional imaging, determine:
- Presence or absence of symptoms: Any history of renal colic, flank pain, urinary frequency, or hematuria 1
- Risk factors for obstruction: History of urolithiasis, malignancy, prior pelvic surgery, or urinary tract infections 1
- Pregnancy status (if applicable): Physiologic hydronephrosis occurs in 70-90% of pregnant patients, typically right-sided 1
- Renal function: Check serum creatinine, as elevated levels may indicate significant obstruction requiring urgent intervention 1
Recommended Next Imaging Step
For Asymptomatic Patients (Most Applicable to Your Case)
CT Urography (CTU) without and with IV contrast is the preferred comprehensive evaluation for asymptomatic unilateral hydronephrosis of unknown cause, as it provides near-complete assessment of the entire genitourinary tract and can identify both intrinsic and extrinsic causes of obstruction 1. CTU includes:
- Unenhanced phase to detect calculi
- Nephrographic phase to assess renal parenchyma
- Excretory phase (≥5 minutes post-contrast) to evaluate collecting system anatomy 1
Alternative option: Non-contrast CT abdomen and pelvis may be appropriate if urolithiasis is the primary concern, though this is less likely given the ultrasound already excluded echogenic calculi 1. However, CT has 97% sensitivity for detecting stones that ultrasound may miss, particularly small stones <3mm 2.
Important Caveats About Ultrasound Limitations
- Ultrasound sensitivity for detecting renal stones is only 52-57% in the right kidney and 32-39% in the left kidney compared to CT 1
- The absence of visible stones on ultrasound does not exclude urolithiasis 2
- Mild hydronephrosis on ultrasound has 77% positive predictive value for ureteral stone on subsequent CT 1
Alternative Imaging Modalities
MR Urography (MRU)
- Useful if IV contrast is contraindicated or to avoid radiation exposure 1
- Provides excellent soft tissue characterization for masses or extrinsic compression 1
Diuretic Renography (DTPA or MAG3 scan)
- Gold standard for determining if true functional obstruction exists versus non-obstructive hydronephrosis 1
- Consider if CTU shows hydronephrosis but no clear anatomic cause 1
- MAG3 is preferred over DTPA, especially in patients with reduced renal function 1
When Conservative Management May Be Appropriate
If the patient remains completely asymptomatic and renal function is normal, some causes of mild hydronephrosis may be observed:
- Physiologic variants (extrarenal pelvis)
- Intermittent obstruction
- Resolved obstruction with persistent dilation 1
However, definitive imaging is still recommended because:
- Upper urinary tract deterioration in adults is often silent 1
- Chronic obstruction can lead to permanent nephron loss 1
- Underlying malignancy or other serious pathology must be excluded 1
Red Flags Requiring Urgent Evaluation
Proceed immediately to contrast-enhanced CT if any of the following develop:
- Fever or signs of infection (risk of pyonephrosis/urosepsis) 1
- Acute flank pain (possible acute obstruction) 1
- Rising creatinine (suggests significant bilateral obstruction or obstruction of solitary kidney) 1
- Bilateral hydronephrosis (higher risk of renal failure) 1