What is the significance of a 3.7 mm calcific density along the anterior aspect of the right psoas muscle in a patient with normal kidney size, shape, and parenchymal attenuation, and no evidence of focal discrete solid lesion, hyperdense calculi (kidney stones), or significant back pressure changes?

Calcific Density Along Psoas Muscle: Clinical Significance

This 3.7 mm calcific density along the anterior aspect of the right psoas muscle is most likely a phlebolith (calcified pelvic vein) or a passed/passing ureteral stone, and requires clinical correlation with symptoms to determine if any further evaluation is needed.

Most Likely Differential Diagnoses

The location along the anterior psoas muscle suggests several possibilities:

• Phlebolith (calcified pelvic vein) - This is the most common incidental finding in this location and is clinically insignificant 1
• Passed or passing ureteral calculus - Given the location along the expected course of the ureter, this could represent a stone that has passed from the kidney or is in the process of passing 1
• Calcified lymph node - Less common but possible in this anatomic location
• Vascular calcification - Can occur along pelvic vessels in this region

Clinical Correlation Required

If Patient Has Pain or Hematuria

• Painful hematuria warrants imaging evaluation to identify urinary tract pathology, and this calcific density should be considered a potential ureteral stone 1
• The absence of hydronephrosis or back pressure changes suggests that if this is a stone, it is either non-obstructing or has already passed 1
• Consider obtaining a KUB (kidney-ureter-bladder) radiograph to better characterize the density and determine if it lies along the expected course of the ureter 1

If Patient Is Asymptomatic

• No further imaging is indicated for isolated, asymptomatic calcific densities in this location 1
• This is most likely an incidental phlebolith with no clinical significance 1
• Document the finding but reassure the patient that no intervention is needed

Key Distinguishing Features

Phlebolith vs. Ureteral Stone

• Phleboliths typically have a lucent center on CT (though not always visible at 3.7 mm)
• Ureteral stones are more likely to be located precisely along the course of the ureter and may show a "soft tissue rim sign" (periureteral edema)
• The absence of hydronephrosis makes an obstructing stone unlikely but does not exclude a passed stone 1

Management Algorithm

1. Assess for symptoms: urgency, frequency, dysuria, flank pain, or hematuria 1
2. If symptomatic:
   • Obtain urinalysis to evaluate for hematuria or infection 1
   • Consider KUB radiograph to track the calcification
   • Follow clinically for stone passage if suspected
3. If asymptomatic:
   • Document as incidental finding
   • No further imaging needed 1
   • Reassure patient

Common Pitfalls to Avoid

• Do not assume all calcifications are stones - phleboliths are far more common in the pelvis and are benign 1
• Do not order extensive workup for asymptomatic findings - this leads to unnecessary testing and patient anxiety 1, 2
• Do not ignore symptoms - if the patient has pain or hematuria, this calcification warrants further evaluation regardless of the normal kidney appearance 1