AJR 2002; 178:1152-1154
© American Roentgen Ray Society
Transient Postpartum Portosystemic Shunting Reavealed by MR Venography
John R. Leyendecker1,
David E. Grayson2 and
Robert Good2
1 Department of Radiology, University of Texas Health Science Center at San
Antonio, 7703 Floyd Curl Dr., San Antonio, TX 78284-7800.
2 Department of Radiology, Wilford Hall Medical Center, Lackland AFB, TX
78236.
Received August 27, 2001;
accepted after revision October 18, 2001.
The opinions and assertions contained herein are the private views of the
authors and are not to be construed as official or as reflecting the views of
the Department of the Air Force or the Department of Defense.
Address correspondence to J. R. Leyendecker.
Introduction
Little is known about the imaging appearance of the pelvic veins and portal
hemodynamics of women in the immediate postpartum period. To our knowledge,
portosystemic shunting of blood via the pelvic veins has not been described in
pregnancy or the puerperium in the absence of predisposing factors such as
cirrhosis, portal venous thrombosis, or other causes of portal hypertension.
We describe a 33-year-old woman in whom we incidentally found markedly
enlarged parauterine and right gonadal veins supplied, in part, by an enlarged
retrograde-flowing inferior mesenteric vein. These findings resolved
completely within 3 weeks of delivery.
Case Report
A 33-year-old woman, gravida 2 with a history of ectopic pregnancy,
presented at 36 weeks 1 day gestation with right lower extremity swelling and
a 2-day history of chest pressure and shortness of breath. Other than the
ectopic pregnancy, the patient had no remarkable medical history. At
admission, she was hypoxic, with an oxygen saturation of 79%, and her lungs
were clear to auscultation. Evaluation for possible pulmonary embolism
included sonographic examination of the lower extremities with negative
findings, a chest radiograph showing a questionable left lower lobe
infiltrate, and findings of intermediate probability on
ventilation—perfusion scan. D-dimer test findings were negative. Because
of clinical concern for pulmonary embolism, the patient was started on IV
heparin. Her admission laboratory data were also remarkable for an elevated
serum creatinine level, which was subsequently attributed to obstructive
uropathy related to pregnancy. Because of the patient's worsening renal
function, a vaginal breech delivery was induced.
On postpartum day 1, because of the continued high index of clinical
suspicion for pulmonary embolism and her renal insufficiency, the patient
underwent MR venography for evaluation of the deep venous system of the pelvis
and inferior vena cava. A time-of-flight venogram was obtained with superior
(arterial) saturation on a 1.5-T scanner (Signa; General Electric Medical
Systems, Milwaukee, WI) (TR/TE, 28/9.4; flip angle, 45°; slice thickness,
5 mm). Because the time-of-flight study revealed indeterminate findings for
deep vein thrombosis, three-dimensional gadolinium-enhanced MR venography was
performed with 20 mL of gadolinium chelate (6.1/1.3; flip angle, 30°;
partitions, 3 mm). This contrast-enhanced study revealed no evidence of deep
venous thrombosis on source image review, but it did show large pelvic
varices, which drained predominately via an enlarged right gonadal vein
(Fig. 1A). In addition, a
markedly enlarged inferior mesenteric vein was noted, with retrograde flow
evidenced by early filling on the arterial phase of the gadolinium-enhanced MR
venogram (Fig. 1B) and
saturation on the time-of-flight venogram
(Fig. 1D). In the axial plane,
the inferior mesenteric vein was comparable in size to the inferior vena
cava.
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Fig. 1A. —33-year-old woman 1 day postpartum with renal insufficiency
and clinical suspicion for pulmonary embolism. Venous phase
maximum-intensity-projection image from three-dimensional contrast-enhanced MR
venography shows enlarged parauterine veins, inferior mesenteric vein
(arrow), and right gonadal vein (arrowhead).
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Fig. 1B. —33-year-old woman 1 day postpartum with renal insufficiency
and clinical suspicion for pulmonary embolism. Arterial phase
maximum-intensity-projection MR image from same study as A shows early
retrograde filling of inferior mesenteric vein (arrow).
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Fig. 1D. —33-year-old woman 1 day postpartum with renal insufficiency
and clinical suspicion for pulmonary embolism. Axial source MR image from
two-dimensional time-of-flight venography performed at level of infrarenal
aorta and inferior vena cava (arrow) shows saturation of signal in
inferior mesenteric vein and aorta caused by presence of superior saturation
band. Findings confirm retrograde flow in inferior mesenteric vein.
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Subsequent sonography of the right upper quadrant revealed patent portal
and hepatic veins with hepatopedal flow in the main portal vein and normal
hepatic echotexture. Liver function tests on the day of admission and at 3
weeks revealed normal findings as well. Because the portosystemic shunting
remained unexplained, the patient underwent repeated contrast-enhanced MR
venography of the portal system 3 weeks postpartum, which revealed complete
resolution of the previous findings (Fig.
1E).
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Fig. 1E. —33-year-old woman 1 day postpartum with renal insufficiency
and clinical suspicion for pulmonary embolism. Maximum-intensity-projection
image from three-dimensional contrast-enhanced MR venography performed 3 weeks
postpartum. Previous findings are no longer present. Normal flow direction was
confirmed in inferior mesenteric vein with repeated time-of-flight venography
(not shown).
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Discussion
MR imaging is increasingly used to assess the venous system. The absence of
ionizing radiation or nephrotoxicity with MR imaging makes it a particularly
valuable tool in the setting of pregnancy or renal insufficiency. However, MR
venography is relatively new, and the spectrum of normal findings during the
puerperium remains to be
defined.
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Fig. 1C. —33-year-old woman 1 day postpartum with renal insufficiency
and clinical suspicion for pulmonary embolism. Targeted
maximum-intensity-projection MR image from same examination as A
confirms origin of inferior mesenteric vein (arrow) from splenic vein
(arrowhead).
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The potential for portosystemic shunting via the inferior mesenteric and
pelvic veins is well known. Study of the inferior mesenteric veins of cadavers
shows plentiful, unidirectional communications from the rectal to the
vaginouterine and vesical plexuses of the female pelvis
[1]. However, to our knowledge,
portosystemic shunting via this pathway has not been documented in pregnancy
in the absence of additional factors predisposing to portal hypertension.
Therefore, the cause, incidence, and clinical significance of such incidental
portosystemic shunting during pregnancy or the puerperium (as in our patient)
are unknown.
One possible explanation for portosystemic shunting during pregnancy would
be the presence of transient portal hypertension related to the latter stages
of pregnancy. Unfortunately, the normal hemodynamic response of the mesenteric
and portal veins to pregnancy in humans is poorly understood. The mesenteric
venous system in rats has been shown to undergo changes in contractility,
basal venous tone, and responsiveness to adrenergic stimulation during
pregnancy, but such data are lacking in humans
[2,3,4].
It has been suggested on the basis of sonographic studies in humans that
portal vein blood flow and velocity increase during pregnancy
[5,
6]. However, evidence directly
linking these alterations to transient portal hypertension is lacking. Further
investigation into the portal hemodynamics of pregnancy is clearly needed.
Such information would be particularly beneficial in assessing the risk of
variceal hemorrhage in pregnant patients with preexisting portal
hypertension.
In summary, this case illustrates that reversible portosystemic shunting
may occur in the puerperium in the absence of underlying hepatic dysfunction
or known vascular disease. This information should prove useful as the number
of vascular MR studies performed in pregnant and postpartum women increases
and may provide additional insight into the hemodynamics of pregnancy.
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Introduction
Case Report
