Pelvic phleboliths are small calcifications, often called “vein stones,” found within the veins of the pelvic region. They result from old, hardened blood clots that have undergone calcification. These vein stones are extremely common, occurring in up to 40% of adults over 40, and their frequency tends to increase with age. They are generally considered an incidental finding, discovered during imaging tests performed for an unrelated reason. Understanding the nature of phleboliths can help alleviate anxiety, as they rarely represent a serious health problem.
What Pelvic Phleboliths Are
Pelvic phleboliths begin as thrombi, or small blood clots, that form inside the veins of the pelvic venous plexuses. Over time, these stagnant blood clots are infiltrated by calcium and other minerals, leading to the formation of a hard, stone-like deposit. These tiny calcifications are typically round or oval and usually measure between 2 and 5 millimeters in diameter.
Their formation is directly linked to factors that cause sluggish blood flow or increased pressure within the pelvic veins. Common risk factors include advanced age and a history of pregnancy, as both can place significant pressure on the pelvic vasculature. Chronic constipation or straining during bowel movements is also a contributing factor due to the increased abdominal pressure it creates. Other underlying venous conditions, such as varicose veins or venous malformations, can also lead to the slow blood flow necessary for phlebolith development.
The composition of a phlebolith is primarily calcified laminated fibrous tissue, a hardened remnant of the original blood clot. They are most frequently located in the lower pelvis, often near the bladder. Their presence indicates a past or chronic issue with blood flow dynamics in the pelvic veins.
Addressing the Symptom Question
Pelvic phleboliths themselves are almost always asymptomatic. Because they are stationary, hardened calcifications, they do not typically move or obstruct blood flow enough to cause discomfort or pain. They are essentially inert markers of a past vascular event, not an active source of pathology.
When a person with phleboliths experiences symptoms like chronic pelvic pain, discomfort, or hematuria, the phleboliths are usually not the direct cause. Instead, these symptoms are often attributable to the underlying condition that prompted the medical imaging. This could include conditions such as irritable bowel syndrome, interstitial cystitis, or endometriosis.
In some instances, the symptoms may be related to the underlying venous issue that caused the phleboliths to form. For example, a patient may experience localized pain or pressure if the phleboliths are associated with symptomatic varicose veins or a venous malformation. However, the pain originates from the enlarged, overfilled veins themselves, not the small, calcified deposit within them. Finding phleboliths during an imaging test directs the physician to investigate other potential causes of the patient’s discomfort.
How Phleboliths Are Diagnosed and Distinguished
Pelvic phleboliths are most commonly discovered incidentally during imaging studies of the abdomen and pelvis. They appear as small, dense, rounded white spots on X-rays, Computed Tomography (CT) scans, or Magnetic Resonance Imaging (MRI). Radiologists are trained to recognize these characteristic appearances and locations, especially in the pelvic venous plexuses.
The most important clinical challenge is distinguishing a phlebolith from a ureteral calculus, or kidney stone, which is a common cause of severe flank and abdominal pain. Both appear as calcified spots in the lower pelvis on imaging, but a ureteral stone often requires immediate treatment, while a phlebolith does not. Differentiation is critical, especially since the ureters run close to the veins where phleboliths form.
Radiologists use specific imaging characteristics to tell them apart, particularly on CT scans. Phleboliths are typically round or oval and may exhibit a characteristic appearance known as a central lucency. They also tend to have a lower mean attenuation value on CT compared to the dense mineral structure of ureteral stones. The presence of a “soft-tissue rim” sign, which is swelling in the surrounding ureteral wall, is a feature strongly associated with a symptomatic ureteral stone and is not seen with phleboliths.
When phleboliths are found, and the patient is experiencing symptoms, the clinical focus shifts to ruling out other, symptomatic conditions. Because phleboliths are considered harmless, the next step is to continue the diagnostic workup for the actual source of the patient’s pain or discomfort. Advanced imaging techniques, such as thin-slice CT or ultrasound with Doppler, can provide the necessary detail to confidently confirm the diagnosis.