Clinical case: Iliac Vein Compression Syndrome

Author: Carlos Suarez-Quian, PhD • Reviewer: Aykut Üren, MD
Last reviewed: October 11, 2022
Reading time: 17 minutes

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.

Contents

Case description
Anatomical and medical considerations
1. Iliac vein compression syndrome
2. May–Thurner syndrome
Explanations to objectives
Sources

+ Show all

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.

History

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.

Imaging

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).

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.

Explanations to objectives

Objectives

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.

Pitting edema

Edema is the apparent swelling that results from fluid accumulation that is most commonly found in the feet, ankles and lower limbs although edema may also sometimes occur in the face, hands and other parts of the body. Women during pregnancy and the elderly are often affected by this condition, but it can happen to anyone. The swelling results from the accumulation of fluid in the subcutaneous interstitial spaces. Clinically, two types of edema are recognized – pitting and non-pitting edema.

Pitting edema refers to edema such that when pressure is applied to the skin of the swollen area and released, an indentation remains (e.g., when the skin is pressed with a finger or when stockings or socks induce indentation in the skin Figure 2B). Non-pitting edema refers to edema when the pressure-induced indentation does not occur.

Occasionally, edema (pitting and non-pitting) can occur without an underlying disease and it is then referred to as idiopathic edema. This is most common in premenstrual or menopausal women. The patient in our case showed pitting edema because of excessive pressure in his lower limb veins due to the compression on the external iliac vein. Pitting edema is also often a sign of congestive heart failure. Non-pitting edema is typically associated with lymphedema, lipedema and myxedema.

Collateral pathways and 'caput medusae'

The two primary components of the abdominal wall superficial venous collateral network in IVC obstruction are the paired lateral thoracic and internal thoracic systems. Figure 3 is a schematic representation of the anatomy of these systems. In general, the distal tributaries of the lateral thoracic system are the superficial epigastric and circumflex iliac veins. The venous blood in this system eventually drains into the superior vena cava via the axillary vein.

In our case, the superficial epigastric veins were dilated because they were draining lower limb blood (most of this blood would flow normally through the iliac venous system). The inferior epigastric veins can also drain the lower limb via the external iliac veins, the inferior and superior epigastric veins and finally the internal thoracic veins. So although not visible from the skin surface, it is likely in this patient this inferior and superior epigastric veins, which are deep to the rectus abdominis muscle, were also dilated. Communication with the lumbar and intercostal veins also allow for some redistribution of the blood from superficial abdominal veins.

Superficial epigastric vein - ventral view

Caput medusae, also known as the palm tree sign, are the appearance of distended and engorged superficial abdominal wall veins that radiate from the umbilicus. The name caput medusae (Latin for "head of Medusa") is used because the radiation of the veins from the umbilicus has a visual similarities to the snakes on Medusa’s head. Any cause of an increase in the caliber of the paraumbilical veins due to increased blood flow in these veins can cause caput medusa and it is possible these veins would have become engorged in this patient over a longer period. Caput medusa is typically a sign of portal hypertension because the paraumbilical veins become distended with the increased pressure in the portal venous system.

Urethral obstruction

Obstruction of the urethra causes bladder distention, secondary urethra hypertrophy and diverticula formation in the bladder. These changes all result from the increased urethra pressure caused by the blockage. With bladder distention, the oblique angle of the ureter entry into the bladder changes and actually acts to impede backflow into the ureter. Thus, hydronephrosis is not normally associated with bladder distention. However, if the pressure in the bladder exceeds the pressure in the ureter, then urine made in the kidneys cannot flow to the bladder and backs up in the ureters and the renal pelvis, causing their dilatation.

Contrast-enhanced CTs in venous compressions

Computed tomography (CT) is a form of radiography that depends on the use of x-rays to reveal internal body anatomy. Radiography is based on the principle that the more dense a structure is, the more x-rays it will scatter and thus those x-rays will not reach the detector. X-rays that reach the detector are conventionally depicted as dark on the screen whereas areas of the screen that receive few or no x-rays are depicted as white. Contrast in radiography is typically based on the injection of an iodinated compound or the ingestion of a barium solution, both of which are radio-dense, thus increasing the visibility of many anatomical structures because of the incorporation of the barium or iodinated compounds temporarily into their structure. Furthermore, the kidneys mainly excrete injected contrast agents so that all the urinary system is typically well seen with IV injection of iodinated contrast agent.

However, almost all urinary calculi are primarily composed of calcium and therefore are highly opaque to x-rays. Thus, these calculi show up very well in non-contrast abdominal CT exams or an abdominal x-ray exam, typically referred to as a KUB (kidneys, ureters and bladder). However, if the patient is injected with contrast prior to a CT or KUB, the contrast agent will mask any calculi that are in the urinary system. Thus, when searching for urinary system calculi it is imperative that a non-contrast exam is ordered (subsequently, a contrast exam may also be done).

Using contrast material for CT may also be avoided in patients with poor kidney function, prior sensitivity to contrast agent and during pregnancy. Less than 10% of stones in the urinary system are uric acid stones, which are radiolucent and do not show up on direct x-rays. They will, however, show up as filling defects in contrast containing imaging studies such as CT and IVP (intravenous pyelogram). Had a contrast CT been done after the non-contrast exam in this patient, the iliac veins would have been filled with blood and the contrast agent, and would have had a high radiographic density and likely would have been much easier to identify on the CT images.

Sources

All content published on Kenhub is reviewed by medical and anatomy experts. The information we provide is grounded on academic literature and peer-reviewed research. Kenhub does not provide medical advice. You can learn more about our content creation and review standards by reading our content quality guidelines.

References:

Ikegami A, Kondo T, Tsukamoto T, Ohira Y, Ikusaka M. Iliac Vein Compression Syndrome due to Bladder Distention Caused by Urethral Calculi. Case Reports in Urology Volume 2015, Article ID 743270.
Modified by Joel A. Vilensky PhD, Carlos A. Suárez-Quian PhD, Aykut Üren, MD.

Authors:

Joel A. Vilensky
Carlos A. Suárez-Quian
Aykut Üren

Layout:

Abdulmalek Albakkar
Adrian Rad

Illustrators:

Figure 2 (B) - James Heilman, MD
Collateral Venous Circulation via Superficial Abdominal Veins - Stefanie Schultz
Male urinary bladder (ventral view) - Irina Münstermann
Superficial epigastric vein (ventral view) - Yousun Koh

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