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Clinical case: Iliac Vein Compression Syndrome: want to learn more about it?

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Clinical case: Iliac Vein Compression Syndrome

After reviewing this case you should be able to describe the following:

  • What is meant by pitting edema? The diagnostic value of this condition and how the test of pitting edema is done.
  • The importance of the collateral pathway provided by the superficial epigastric veins in iliac compression syndrome. What is meant by the caput medusa sign and how it might relate to this case.
  • How the calculus in the urethra resulted in bladder distension. Also, why might you expect bladder distension would be associated with hydronephrosis.
  • A non-contrast CT rather than a contrast-enhanced CT was used to evaluate the patient for urinary calculi. Whether a contrast-enhanced CT might have revealed the venous compression more easily.

This article is based on a case report published in the Journal "Case Reports in Surgery" in 2015, by Caroline C. Jadlowiec, Beata E. Lobel, Namita Akolkar, Michael D. Bourque, Thomas J. Devers, and David W. McFadden.

It has been modified and reviewed by Joel A. Vilensky PhD, Carlos A. Suárez-Quian PhD, Aykut Üren, MD.

Case description

Figure 1. Cadaver photograph showing the external iliac artery and vein. Note that the femoral nerve is also visible in this image (yellow). Remember that the nerve is the most lateral structure here. The vein, in contrast, is the most medial structure and most subject to compression by the distended bladder.


A 71-year-old man presented with bilateral lower extremity edema, which had gradually become more severe over the last week. During this week the patient had also gained 4 kg of weight. The swelling was more prominent toward evening, but neither of his lower limbs was painful. The patient had a history of dysuria, which had worsened over the same one-week period. The patient also had a history of left renal tuberculosis, which resulted in a non-functioning left kidney and idiopathic urethral stenosis beginning 20 years ago, as well as very dry, cracked skin (asteatotic eczema) for several years (Figure 2, A-C). The patient was not on any drug therapy.

Figure 2. A. Photograph of the patient showing pronounced bilateral lower limb edema with asteatotic eczema. B. Photograph of a patient (not of the patient described in this case) showing pitting edema. C. Photograph of the patient in this case showing distended superficial veins of the anterior abdominal wall (superficial epigastric vein is indicated by the arrows). Note also same eczema on the right side. (B - Wikipedia - James Heilman, MD))

Physical examination

Physical examination revealed distention of both superficial epigastric veins, prominent pitting edema of both lower limbs, and redness of the skin due to asteatotic eczema (Figure 2 A-C). His cardiovascular and respiratory examinations were normal. Because the bilateral distention of the superficial epigastric veins began at the femoral triangle, the patient’s bilateral leg edema was hypothesized to be caused by obstruction of the iliac veins or obstruction of the inferior vena cava (Figure 3).

Figure 3. Illustration of collateral venous circulation provided by superficial abdominal veins.

Furthermore, because the bilateral lower extremity edema and worsening dysuria had a similar onset, the cause was suspected to be bilateral iliac vein compression by an acutely distended bladder, which was, in turn, thought to result from urine retention.


Figure 4. Axial CT showing the urethral stone (yellow circle). Note also that the urethra is dilated proximal and distal to the stone. See Figure 5 for cadaver anatomy relative to this CT.

Abdominal non-contrast CT was performed, revealing a calculus in the pendulous portion of the spongy urethra, marked distention of the bladder (as well as the right renal pelvis and ureter), and compression of both external iliac veins by the distended bladder (Figures 4-7).

Figure 5. Photograph of a mid-sagittal section of a cadaver showing the different parts of the male urethra. The location of the stone in the pendulous part of the spongy urethra is shown by the sold solid white circle.

Diagnosis and management

Figure 6. A. Coronal CT of the patient in this case showing the distended bladder with a white line showing the level of the section in B. B. Axial CT showing the distended bladder and the compressed external iliac veins. The TB in the image is an unusual trabecular band/diverticular band seen in this bladder (although in a single CT image it resembles a polyp the entire CT series and cystography suggested it was an unusual feature of a highly convoluted bladder). The same feature is seen in the coronal image in A

Based on these findings, a diagnosis of iliac vein compression syndrome due to bladder distention caused by urethral calculus was made. A urethral catheter was inserted to relieve urinary retention; subsequently, the patient’s lower limb edema gradually improved and resolved after one week.

Figure 7. Mid-Sagittal photograph of cadaver pelvis showing the external iliac vein and artery. Note how the distended bladder would compress the vein. The artery is not affected because the arterial pressure is much greater than venous pressure.

Anatomical and medical considerations

Iliac vein compression syndrome

Iliac vein compression syndrome secondary to bladder distention usually presents with bilateral edema that shows an acute onset. The present case demonstrates well the hypothetico-deductive method of medical reasoning that is part of the differential diagnosis and that was able to lead the authors of the case report to deduce the underlying etiology of their patient’s lower limb edema. Although this patient had had dysuria for a sustained period, the coincidence in timing of its increased severity with the lower limb edema led the authors to look for disease conditions that could cause both.

In this patient, the distended bladder resulted from the urethral calculus. Although it would seem that such bladder distention would not lead to dysuria (in fact it would intuitively seem to leave to frequent urination), the stretching of the bladder can compress, stretch and change to orientation of the trigone and the internal urethral orifices making urination difficult (figure 8).

Figure 8. An illustration showing an overview of the anatomical structures of the male urinary bladder.

Of course in this patient, urination was already difficult due to the urethral calculus, which also likely had become more securely lodged in the urethra as the bladder became more distended. Concurrent with the dysuria, the patient showed lower limb pitting edema (see Figure 1 and explanation 1 below). The contemporaneity of the two conditions led the authors to deduce that the patient was suffering from iliac compression syndrome, which was confirmed by CT.

The leading cause of a distended urinary bladder among men is benign prostate hyperplasia; other causes include prostate cancer, benign prostate tumor, urethral stricture, and neurogenic bladder. For women, neurogenic bladder from stroke and diabetes can cause urinary retention.

May–Thurner syndrome

A different type of iliac compression syndrome is known as May–Thurner syndrome (MTS). This is a more specific condition in which compression of the venous outflow of the left lower extremity may cause discomfort, swelling, pain and most seriously, deep venous thrombosis.

Figure 9. An illustration showing how the left common iliac vein could be compressed by the overlying right common iliac artery just after it origin (green shape).

In MTS the left common iliac vein is compressed by the overlying right common iliac artery. It traverses diagonally from left to right to drain to the inferior vena cava. As the vein does this, it passed deep to the right common iliac artery, where it may be compressed between the artery and the bodies of the lumbar vertebrae. This compression may be benign and only become clinically significant if it causes significant reduction in venous flow or increases in venous pressure, or if it is associated with deep venous thrombosis.

Clinical case: Iliac Vein Compression Syndrome: want to learn more about it?

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